Subscriber access provided by BUFFALO STATE
Review
Catalytic approaches to monomers for polymers based on renewables Bernhard Stadler, Christoph Wulf, Thomas Werner, Sergey Tin, and Johannes G. de Vries ACS Catal., Just Accepted Manuscript • DOI: 10.1021/acscatal.9b01665 • Publication Date (Web): 08 Jul 2019 Downloaded from pubs.acs.org on July 16, 2019
Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.
Page 1 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
Catalytic Approaches to Monomers for Polymers Based on Renewables Bernhard M. Stadler, Christoph Wulf, Thomas Werner, Sergey Tin, Johannes G. de Vries*
Leibniz Institut für Katalyse e. V. an der Universität Rostock, Albert-Einstein-Strasse 29a, 18059 Rostock, Germany
ABSTRACT: Polymers are used in simple consumer items like carpets, furniture, glues and clothing but are also materials used in advanced engineering, including those used in the aerospace industry. Therefore polymers and consequently their monomers play an important role in our everyday life. Currently, most of the monomers are produced from fossil resources, the supply of which is diminishing. In this article we review strategies and catalytic processes to obtain currently used and potentially new monomers from renewable bio-based feedstocks and platform chemicals. The review is divided by type of monomer and includes diacids and esters, diols, hydroxyacids and esters, lactones, carbonates, cyclic ethers, diamines, amino acids and lactams, 1 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
alkenes, acrylics and conjugated dienes. Only routes based on the use of homogeneous, heterogeneous or bio-catalysis are described. Fermentative processes are not discussed.
Keywords: sustainable chemistry, polymers, bio-refining, monomers, renewable resources, catalysis
1. Introduction The supply of fossil resources is finite and although it remains unclear at what moment in time this would lead to an acute shortage, it is generally considered that this could happen in the next 50 years; and thus we need to prepare ourselves for this. In order to safeguard the production of the chemicals our everyday life depends on we will have to consider their production from renewable resources. The major resource is lignocellulose in the form of wood or agro waste; also municipal waste and waste from the paper industry can be considered. Next to this, fats, fatty acids and glycerol are a treasure trove of resources and finally also the terpenes, although currently only 2 ACS Paragon Plus Environment
Page 2 of 247
Page 3 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
- and -pinene are produced on a large scale. Although considerable amounts of protein are available from nature, this is generally not considered a very good source in view of the presence of 20 natural amino acids that are not easily separated from one another. There are a number of different ways to convert biomass into chemicals but one methodology that has attracted considerable attention is conversion via the use of socalled platform chemicals. These are rather simple building blocks that can be prepared from renewable resources in a single step, either by fermentation or by thermochemical conversion in good yields, but still retain sufficient functionality for further conversion into usable compounds. A group of 12 types of compounds that can be made from sugars has been defined in a report made for the US Department of Energy.1 The chart shown here (Figure 1) is based on this but contains some additional platform chemicals such as ethanol, lactic acid oleic acid, etc. Very little catalysis, with the exception of acid catalysis is used in the preparation of these platform chemicals, however, the conversion of platform chemicals into useful chemicals requires the use of catalysis in over 90% of the cases. In this review we will 3 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 4 of 247
limit ourselves to the description of catalytic processes that convert sugars and platform chemicals into CO2H
HO
CO2H
HO2C
Fumaric acid
HO
Malic acid
OH O
O
O
2,5-Furandicarboxylic acid
CO2H
3-Hydroxy-propionic acid
O
O
HO
Furfural
Itaconic acid
O
H
H
O
CO2H
CO2H
HO
HO2C
HO2C
Succinic acid
CO2H
OH
O
O Levulinic acid
5-Hydroxymethylfurfural NH2
CO2H
O
CO2H
OH OH OH
HO H 2N
CO2H
H 2N
L-Aspartic acid
CO2H
H 2N
L-Glutamic acid
CO2H
OH OH O
L-Lysine
HO
Glucaric acid OH OH
O
HO
O
OH
HO
OH
3-Hydroxy-butyrolactone
OH OH OH
HO
OH OH
Glycerol
OH OH
Sorbitol
Xylitol
OH OH -Pinene
-Pinene
Ethanol
CO/H2 Synthesis gas
CO2H Lactic acid
7
7
Oleic acid
CO2H
5
HO
7
CO2H
Ricinoleic acid
Figure 1. Platform chemicals (Structures in red where added by the authors and were not part of the original DOE report1)
monomers for polymers. We have limited ourselves to the description of processes for the production of compounds that have already been used as monomers for polymers. Fermentative routes will not be described. 4 ACS Paragon Plus Environment
Page 5 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
2. Dicarboxylic acids Dicarboxylic acids are important monomers for the production of polyesters and polyamides. In view of the importance of this class of compounds, many syntheses have been reported, some of which are already nearing the stage of large-scale production. Figure 2 gives an overview of the diacids, esters and anhydrides that are part of this review.
OH HO
O OH
O
OH
HO
O SA
TA O
CO2H
OH
OH
HO
MeO2C
O
OH O
X
O
X=O, C(CH3)2
PA
OH O
O
FDCA
HO O
O
MAN
O
O AA O
O
HO
OH
HO
GA O
O
MA
O
O
HO
HO2C
O
O
O
RO
OR
n = 7, 8, 9, 10, 16, 17, 18
CO2Me CO2Me
MeO2C
Figure 2. Bio-based diacids, diesters and anhydrides
2.1 C-3 di-acids
Many studies have been published on the oxidation of glycerol, but few of these report high selectivity to a single product. Hutchings and co-workers reported the 5 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 6 of 247
oxidation of glycerol to tartronic acid using AuPt/LaMnO3 in water containing 4 equiv of NaOH w.r.t. glycerol at 3 bar O2 and 100 °C. After 24h an 88% selectivity to tartronic acid was observed (Scheme 1).2 Although Tartronic acid decarboxylates at temperatures above 180 °C it has been used as co-monomer in the polymerization with glycolic acid.3 AuPt/LaMnO3 O2, 3 bar
OH HO
OH
OH HO
NaOH, H2O 100 °C, 24h
OH 88% Selectivity
O O Tartronic acid
Glycerol
Scheme 1. Tartronic acid from glycerol
2.2 Succinic acid
a.
O
Ru-Np
OH
O2, 15 bar H2O, 150 °C
LA O O
(98% Selectivity CO2H at 79% Conversion)
CO2H
+ HO
CO2H
+ CH3CO2H + HCO2H + CF3CO2Me Amberlyst-15
H
O
60%
TFA, 90 °C
O
c.
SA HO2C
H 2O 2
OH
b.
HO2C
H 2O 2 H2O, 80 °C
O
HO2C
CO2H 74%
FA d.
HO HO HO
O
OH OH
Fe@CNT O2, 10 bar H2O, 140 °C
HO2C
HO CO2H
fructose
Scheme 2. Succinic acid from renewable resources 6 ACS Paragon Plus Environment
O
O OH
Page 7 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
Succinic acid (SA) can be produced by fermentation. Nevertheless, a number of catalytic routes have been reported for its synthesis based on other platform chemicals that also show promise for large-scale production. The oxidation of levulinic acid (LA) with oxygen (14 bar) catalyzed by Ruthenium nanoparticles at 150 °C leads to the formation of SA with 98% selectivity if the conversion does not exceed 80% (Scheme 2a).4 Mascal and co-workers reported the Baeyer-Villiger oxidation of LA using hydrogen peroxide in trifluoroacetic acid at 90 °C (Scheme 2b).5 The product of this reaction is a mixture of SA, 3-hydroxypropionic acid, acetic acid, formic acid and methyl trifluoroacetate. From this mixture they were able to isolate SA in 59% yield by removal of the volatiles. Ebitani and co-workers reported the oxidation of furfural (FA) to SA in 74% yield using hydrogen peroxide and the acidic ion exchange resin Amberlyst-15 as catalyst (Scheme 2c).6, 7 Use of the same method on a toluene solution of crude furfural obtained from acid treatment of hemicellulose resulted in a 52% yield of SA, based on the amount of FA in the crude mixture.8 Interestingly, oxidation of fructose with oxygen (10 bar) catalyzed by iron nanoparticles on carbon nanotubes (Fe@CNT) at 140 °C
7 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
led to good selectivity to SA only at very low conversions. At higher conversions the SA was rapidly converted to oxalic acid (Scheme 2d).9
2.3 Maleic acid and maleic anhydride
The aerobic oxidation of furfural (FA) to maleic acid (MA) was catalyzed by phosphomolybdic acid as catalyst in aqueous/organic biphasic systems. Best results were obtained in tetrachloromethane/water. Under optimized conditions (20 bar O2, 110 °C), a 35% yield of MA could be obtained with 69% of selectivity, at 50% furfural conversion (Table 1) 2a).10 Using a combination of copper nitrate and phosphomolybdic acid under otherwise the same conditions, the same group could achieve a yield of 49% of MA.11 Oxidation of FA with H2O2 catalyzed by titanium silicalite (TS-1) at 50 °C gave an 80% yield of MA after 28h and 92% yield after 52h.12 This method was recently further improved by Dumesic and co-workers who used a two-phase system composed of -valerolactone (GVL) and water.13 Here a yield of 70% could be obtained, which could be further improved to 83% by a different preparation method of the TS-1 catalyst. Oxidation of FA under 1.2 MPa of oxygen pressure catalyzed by iron tetra-(p-chlorophenyl)-porphyrin (FeTCTPP) at 90 °C resulted after 10h in 44% 8 ACS Paragon Plus Environment
Page 8 of 247
Page 9 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
yield of MA.14 The catalyst is quite stable and could be recycled a number of times. Oxidation of FA using hydrogen peroxide in formic acid as solvent at 60 °C resulted in the formation of MA in 91% yield after 4h.15 5-Hydroxymethyl-furfural (HMF) could also be oxidized using the same method at 100 °C and resulted in an MA yield of 81% after 4h. Even better results were obtained with furan, which can be obtained by decarbonylation of furfural. Here a yield of 99% of MA was obtained after 4h at 100 °C. Oxidation of FA in the gas phase over VOx/SiO2 at 320 °C and 5.7 kPa oxygen pressure led to the formation of maleic anhydride (MAN) in 73% selectivity.16 Zhang and co-workers examined a number of different vanadium phosphorus oxide (VPO) type catalysts and found that a plate type catalyst produced by a hydrothermal method with glucose as reductant led not only to the highest selectivity in the oxidation of FA to MAN but it also had the highest activity.
Table 1. Oxidation of furfural to maleic acid and maleic anhydride
Catalyst Oxidant H
O O FA
Solvent Temp.
HO2C
CO2H
or
O
O MAN
MA
9 ACS Paragon Plus Environment
O
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Entry Oxidant
Catalyst
Solvent
Page 10 of 247
T (°C) Product Yield (%)
1.
O2, 2 MPa
H3PMo12O40 CCl4 / H2O 110
MA 35
2.
O2, 2 MPa
Cu(NO3)2
CCl4 / H2O 110
MA 49
H 2O
MA
/
Conv.a
Sel.a MA
FA (%)
or (%)
50
69
H3PMo12O40 3.
H2O2
TS-1
50
80b,
92c 4.
H2O2
5.
O2,
TS-1 1.2 FeTCTPP
GVL / H2O 50
MA 83
H 2O
MA 44
90
MPa 6.
H2O2
7.
O2,
-
HCO2H
5.7 VOx/SiO2
-
MA 91 320
MAN
73
kPad a
Conv. = Conversion; Sel. = Selectivity bAfter 28h. cAfter 52h. d Gas phase reaction
2.4 C-5 diacids
Pentanedioic acid or glutaric acid has been made from glutamic acid. Monosodium glutamate is produced on large scale by fermentation mainly for application as flavoring agent. De Vos and co-workers converted glutamic acid into N,N-dimethylglutamic acid via reductive amination with formaldehyde.17 Hydrogenolysis of this compound using
10 ACS Paragon Plus Environment
MAN
Page 11 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
30 bars of H2 catalyzed by Pt/TiO2 in methanol at 225 °C yielded 81% yield of glutaric acid after 4h (Scheme 3). CO2H
H 2N
CO2H
CO2H
H2CO, H2 Pd/C
Glutamic acid
N
CO2H
Pt/TiO2 H2 40 bar MeOH
CO2H
N, N-Dimethylglutamate 90%
+ Me3N HO2C Glutaric acid 81%
Scheme 3. Glutaric from glutamic acid
2.5 Adipic acid Adipic acid (AA) is one of the two monomers for nylon-6,6. Its current production is associated with a rather high carbon footprint. This is caused by the excessive number of recycles needed as a result of the low conversion in the cyclohexane to cyclohexanone oxidation as well as by the associated NOx production in the oxidation of cyclohexanone to AA with nitric acid. In addition, it is a rather high-volume bulk chemical and for these reasons many groups have looked into the possibility of producing AA from renewables.
cis,cis-Muconic acid can be produced by fermentation. Hydrogenation of Muconic acid gives AA in excellent yield. Hydrogenation of the filtered fermentation broth with 11 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
10% Pt on carbon (5% mol/mol) at 34 bar of H2 pressure for 2.5 h at ambient temperature afforded a 97% (mol/mol) conversion of cis,cis-muconic acid into AA (Scheme 4a).18 Bimetallic catalysts were also used for this conversion of which Ru10Pt2 produced AA with 95% selectivity.19 The company Rennovia has developed an interesting two-step process from glucose (Scheme 4b).20, 21 In the first step glucose is oxidized with oxygen to glucaric acid using a heterogeneous catalyst. Based on their patent the assumption can be made that a platinum catalyst on a carrier material is used. The oxidation takes places without any added base. The reaction is probably stopped at a stage were selectivity to glucaric acid is around 50% to prevent over oxidation. The resulting product mixture is purified by simulated moving bed (SMB) and the intermediate oxidation products can be recycled back to the oxidation reaction.22 In the next step glucaric acid is hydrogenated in the presence of HBr (or HI) in acetic acid. A range of noble metals (Pd, Ru, Rh, Ir, Pt) and combinations thereof were screened and all these led to the formation of AA in yields between 30-89%. In view of the fact that reclamation of metal combinations is near impossible it seems likely that a single metal would be used in their pilot plant, most likely palladium. 12 ACS Paragon Plus Environment
Page 12 of 247
Page 13 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
It is also possible to subject mucic acid, obtained via oxidation of galactose or even enzymatically from sugar beet residue,23 or one of its esters to the deoxydehydration reaction catalyzed by rhenium compounds such as MeReO3 or Re2O7 using a primary or secondary alcohol as reductant (Scheme 4c). This leads to the formation of hexadienedioic acid otherwise known as muconic acid. This compound can be hydrogenated with a palladium or platinum catalyst to adipic acid. Toste and coworkers used 1-butanol as reductant and obtained an overall 62% yield of di-n-butyl adipate using HReO4 for the deoxydehydration step.24 Su, Zhang and co-workers found that the esterification step is slow, but necessary to solubilize mucic acid and added p-TsOH to the reaction in 2-pentanol to speed up this step, resulting in a 99% yield of a mixture of muconic mono- and diesters, which was subjected to transfer hydrogenation with 2-pentanol catalyzed by Pt/C to give a 99% yield of the mixture of adipate esters.25 Combining the two reactions in one step yielded 73% of the mixture of adipate esters. Use of ionic liquids as solvent in the deoxydehydration step allowed recycle of the Re-catalyst.26 trans,trans-Muconic acid could also be reduced in good yield using an enoate reductase.27
13 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 14 of 247
Rennovia developed another process based on the hydrogenation of 2,5-furandicarboxylic acid (FDCA, see sub-chapter 2.6 for its production) (Scheme 4d).28 In this process FDCA is first hydrogenated in acetic acid catalyzed by Pd/SiO2 at 140 °C and 53 bars of H2 to from 2,5-tetrahydrofuran-dicarboxylic acid in 88% yield. This compound was next hydrogenated in acetic acid in the presence of HBr (or HI) using either a rhodium or palladium catalyst at 160 °C and 50 bars of hydrogen to form AA in over 90% yield. Surprisingly, this second step is also possible without metal catalyst as shown by Vlachos and co-workers who used a combination of hydrogen and HI or a combination of hydrogen and an iodide salt and the solid acid catalyst Nafion in propionic acid.29, 30 a.
Fermentation Sugars
10% Pt/C
CO2H
HO2C
H2, 34 bar
cis,cis-Muconic acid
b.
HO OH H
HO H
H OH
Pt-Cat H
OH OH O HO
O2
OH OH
OH O
OH OH
HReO4, MeReO3 or Re2O7
OH OH O HO OH OH
1-butanol or 3-pentanol
OH
O
H O
AA
HBr or HI
CO2R
RO2C
H2
Pd/SiO2
Ox. HO2C
O
Pt or Pd
Esters of AA
R = H, 1-butyl or 2-pentyl
Mucic acid
d.
Adipic acid (AA)
Glucaric Acid
Glucose
c.
OH O
Pd/C, H2 OH
O
O HO
CO2H
H2
HO2C
O
14 ACS Paragon Plus Environment
Rh or Pd-cat H2 50 bar, HBr or CO2H H2 / HI
AA
Page 15 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
Scheme 4. Catalytic conversion of sugars into adipic acid
Levulinic acid can be hydrogenated to gamma-valerolactone in near quantitative yield using a variety of catalysts of which ruthenium on a solid carrier seems to be one of the best.31 Gamma-valerolactone (GVL) can be subjected to a ring-opening process to form a mixture of isomeric pentenoic acids by using an acid catalyst in a reactive distillation process32 or it can be ring-opened in the presence of methanol in a gas phase process using acidic33-35 or basic catalysts36, 37 or also as reactive distillation process.38, 39 Van Meurs and co-workers subjected the mixture of pentenoic acids to an isomerizing hydroxycarbonylation reaction using the palladium bisphosphine catalyst that had earlier been developed by Lucite, giving adipic acid in 98% yield (Scheme 5a left side).32,40 Researchers at DSM developed a very similar process at the same time performing an isomerizing methoxycarbonylation on the mixture of methyl pentenoates to give dimethyl adipate in 98% yield, which was subsequently hydrolyzed to adipic acid (Scheme 5a right side).41-43 The direct hydroxycarbonylation of GVL to adipic acid would of course be the ideal process. Unfortunately, the high temperatures needed for the ring-opening of GVL do not allow the use of ligands, making it impossible to steer the selectivity of the hydroxycarbonylation. Consequently, 15 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 16 of 247
a maximum selectivity to adipic acid of 61% could be obtained when the hydroxycarbonylation
was
catalyzed
a.
by
RhCl3
and
HBr
O OH O LA H2 CO2H
Solid acid catalyst
+ CO2H + CO2H
cat.
Distill product from liquid phase
O
O GVL
Solid acid catalyst
+
MeOH Gas Phase
+
Pentenoic esters PtBu2 PtBu2
Pd(OAc)2 DTBP MeSO3H
Pd(OAc)2 DTBP MeSO3H
DTBP H+/H2O
CO2H
MeO2C
O
RhCl3 / HBr CO, 28 bar
O
HOAc, 220 °C
CO2H HO2C
GVL
CO2H AA
+ VA
c.
HO2C + MGA
CO2H
+
HO2C ES
CO2H
Grubbs' Metathesis catalyst CO2R
CO2Me
Dimethyl adipate
Adipic acid (AA)
b.
CO2Me CO2Me
Pentenoic acids
HO2C
CO2Me
RO2C
H2 CO2R
R = H, Me
Metathesis cat. or Pd/C
Scheme 5. Catalytic conversion of levulinic acid into adipic acid
16 ACS Paragon Plus Environment
AA
in
Page 17 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
acetic acid at 220 °C and 28 bar CO pressure.44 The remaining products were 2methyl-glucaric acid (MGA, 21%), 2-ethyl-succinic acid (ESA, 4%) and valeric acid (12%) (Scheme 5b). If 3-pentenoic acid or the methyl ester can be obtained pure, they can be subjected to a metathesis reaction to obtain the unsaturated C6 diacid or ester, which can be hydrogenated, either using the metathesis catalyst as hydrogenation catalyst or in a separate step with Pd/C (Scheme 5c). Metathesis of the mixture of acids or esters gives a mixture of C6, C7 and C8 unsaturated diacids/esters.45,46 Hronec reported the highly selective hydrogenative ring-closure of furfuryl alcohol under aqueous conditions to obtain cyclopentanone in 95% selectivity.47 Du and coworkers reacted cyclopentanone with dimethyl carbonate at 260 °C, catalyzed by MgO to obtain 51% selectivity to dimethyl adipate (DMA) at 86% conversion (Scheme 6).48 Cyclopentanone first reacts with DMC to form 2-methoxycarbonyl-cyclopentanone, which subsequently undergoes a retro-Dieckmann condensation reaction with methoxide to from DMA. O H O
O
10%Ni/SiO2 H2, 8 bar H 2O
O
MeO
O OMe
MgO, 260 °C
MeO
OMe O dimethyl adipate
FA
17 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Scheme 6 Dimethyl adipate from furfural via cyclopentanone
2.6 2,5-Furandicarboxylic acid 5-Hydroxymethylfurfural (HMF) is made via acid catalyzed dehydration from fructose.49 If the reaction is performed in water, the yield remains low as HMF is rehydrated and reacts further to form levulinic acid and formic acid. Quite high yields of HMF have been obtained in dipolar non-protic solvents, such as DMSO and DMF using Lewis acid catalysts. The problem here is that HMF is not easily removed from these solvents as it decomposes during distillation. In addition, the solvents themselves are not stable under the condition of the dehydration. Dumesic developed a biphasic system consisting of four different solvents the use of which resulted in decent yields of HMF.50 However, the fructose concentration has to be kept low to prevent formation of humins and thus relatively large amounts of solvents need to be recycled. Currently HMF is only produced by the Swiss company Ava-Biochem, who produces it as a side product in their sugar carbonization process on a scale of ca 300 Ton/yr.51 It seems highly unlikely that an economic process can be developed for the production of HMF on large scale. However, two workarounds have been found. Avantium has developed a process for the production of the methyl ether of HMF by 18 ACS Paragon Plus Environment
Page 18 of 247
Page 19 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
performing the dehydration reaction in methanol (Scheme 7b).52 This compound is stable and thus a good yield and selectivity could be achieved. This process has run in a pilot plant for a number of years and plans have been announced to build a 25-50 kTon facility in Belgium. They have developed a process for the oxidation of 5methoxymethyl-furfural to a mixture of 2,5-furandicarboxylic acid and its monomethylester using the classical manganese-cobalt-bromide catalyst that was developed for the Amoco process for the oxidation of xylene to phthalic acid.53 The product mixture was further esterified to dimethyl 2,5-furandicarboxylate. The other solution stems from the work of Mascal, who performed the dehydration reaction of fructose in a two-phase system of concentrated HCl (with added chloride salt) and a chlorinated solvent (Scheme 7c)54 He was able to obtain yields in excess of 70% of 2chloromethyl-furfural, again a stable compound. It was also possible to make this compound from glucose or even cellulose in good yields. Here, the only issue is the recycling of the HCl. The 5-chlormethylfurfural has been converted to FDCA by oxidation with HNO3.55 I was also converted into the 2-acetoxymethyl compound by exchange with acetate and this compound was oxidized to FDCA using Pt/C and O2 in the presence of NaHCO3.56 19 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
HMF can be oxidized to 2,5-furandicarboxylic acid (FDCA) (Scheme 7a). Polyesters have been made from FDCA that seem quite promising, in particular the polyester with ethyleneglycol (PEF) that has been touted as replacement for PET. Many groups have worked on the oxidation of HMF to FDCA. The area has been reviewed.57, 58 Thus, in view of this and in view of the fact that it seems unlikely that any of these processes will ever be scaled up as it is impossible to obtain HMF in high isolated yields in an economic manner, we will not discuss this in detail. The general picture is that metalcatalyzed oxidation with oxygen or air at higher pressures is quite feasible and leads to FDCA yields claimed to be higher than 95% as long as 2 or more equivalents of a mineral base, usually NaOH are used. Without base the FDCA seems to precipitate on the catalyst, but in addition, the dehydrogenation reaction is probably catalyzed by base and slows down upon its consumption. Another important issue is the fact that the formed acid will catalyze the formation of humins from HMF. A number of basefree processes have been reported, but it would seem to be the catalyst carrier material that functions as the base in most of these cases. It is also possible to use the Mn/Co/Br catalyst without base and this system was extensively evaluated by Subramanian and co-workers. They found that mass transfer of oxygen is limiting and developed a 20 ACS Paragon Plus Environment
Page 20 of 247
Page 21 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
spraying type process to increase the gas-liquid surface. Using this methodology they were able to increase the yield of FDCA to 96%.59, 60 Enzymatic oxidation of HMF to FDCA is also quite successful and achieves excellent selectivities.61 The conversion has been achieved with an oxidoreductase that was cloned into a pseudomonas Putida, allowing whole cell fermentative oxidation in 97% yield. Fraaije and co-workers used an FAD dependent enzyme and also achieved very high yields of FDCA. However, the relatively high dilution and low rates of these processes result in a productivity that is about 50 times lower than the chemical oxidation. In addition, these processes demand a pH of 7 and thus two equivalents of salt are produced. Thus these processes are also unlikely to be used on large scale.
21 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
HOCH2 a.
O OH
CH2OH
H+
OH OH Fructose
HOCH2 b.
O OH
CH2OH OH OH
HOCH2 c.
O OH
O
OH
H
Metal catalyst
H+ MeOH
MeO
HO2C
O
RO2C
OH HO
CO2H O
OH OH D-galacturonic acid
O
CO2R
R = H, Me
ClCH2CH2Cl
O
Cl
H O
HNO3 or 1. NaOAc 2. Pt/C, O2
HO2C
O
CaCl2
HOCaOOC
CH2OH O OH OH
HO2C
OH
CO2H
Au/C O2
MeONa MeOH
or glucose or cellulose
d.
CO2H
O2 Co/Mn/Br catalyst
O
O
2,5-furandicarboxylic acid (FDCA)
H
CH2OH Conc. HCl LiCl OH OH
O2 or air
Hydroxymethylfurfural (HMF)
O
Page 22 of 247
O
H O
5-keto-galactonic acid calcium salt
Scheme 7. Conversion of sugars to 2,5-furandicarboxylic acid
In view of the instability of HMF, Bitter and co-workers examined the production of FDCA starting from D-Galacturonic acid which is available in large amounts from sugar beet pulp.62 In the first step this compound was isomerized to the 5-keto analogue, catalyzed by CaCl2 (Scheme 7d). The product could be dehydrated under acidic conditions in methanol to obtain methyl 5-formyl-2-furancarboxylate in up to 65% yield. Further oxidation of this in MeOH/NaOMe using an Au/C catalyst gave dimethyl 2,5furandicarboxylate in 99% selectivity.
22 ACS Paragon Plus Environment
Page 23 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
Furfural is already produced on large scale from biomass. Oxidation of this in KOH gives the potassium salt of 2-furancarboxylic acid. This compound can be subjected to a disproportionation reaction called the Henkel reaction catalyzed by CdI2 or ZnCl2 to give a 50/50 mixture of furan and 2.5-furandicarboxylate.63 Acidification precipitates FDCA in pure form. This reaction was recently revisited by van Es and co-workers, who found that in fact a 7:3 mixture of 2,5- and 2,4-furandicarboxylate is formed (Scheme 8a).64 This had previously been overlooked by other researchers as 2,4furandicarboxylic acid is much more soluble in water than its 2,5 counterpart. Although furan also has value, a process with two different products is in general less desired as market developments may not follow the same dynamics. It is possible to produce FDCA as major product in 89% yield by reaction of the cesium salt of 2-furancarboxylic acid in an atmosphere of CO2 catalysed by excess Cs2CO3 (Scheme 8b).65 Distill
CO2K a.
H
O O
CuO-Np, Air KOH, H2O
OK
O
CdI2 or ZnCl2
+ KO2C
O
+
CO2K O 70%
KO2C
H+
HO2C
b.
(
O)2Cs
O O
Cs2CO3 CO2, 8 bar 265-280 °C
O
CO2H
Precipitates
-
O 2C
O Cs
CO2-
2+
23 ACS Paragon Plus Environment
O 30%
O
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Scheme 8. FDCA from furfural 2.7 Terephthalic acid
Although replacing terephthalic acid with FDCA seems a good option it does require major changes in the entire supply chain and thus a process for renewable phthalic acid would also be highly desirable. HMF can be hydrogenolyzed to 2,5dimethylfuran (DMF).66, 67 This compound can undergo Diels-Alder addition reactions with dienophiles. Toste reacted DMF with acrolein at -60 °C catalyzed by Sc(OTf)3 to obtain the bicyclic adduct. This was oxidized to the acid and next treated with sulfuric acid to obtain 2,5-dimethylbenzoic acid. This compound was decarboxylated using a copper catalyst to obtain para-xylene.68 A more simplified procedure was developed by several other groups who examined the Diels-Alder reaction of DMF with ethylene (A1) catalyzed by various Lewis acids (Table 2). Noteworthy are the excellent results obtained with Cu(OTf)2 (Table 2, Entry 5).
24 ACS Paragon Plus Environment
Page 24 of 247
Page 25 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
CO2H
O CHO
1. Ox 2. H2SO4
Sc(OTf)3 -60 °C
H O
HO
H2C=CH2 Catalyst
Pd/C H2
O
HMF
CuO Bathophenanthroline 210 °C
CHO
O
Process
Solvent, T
DMF
CO2H
AMOCO HO2C
p-xylene
O
terephthalic acid
Scheme. 9 Phthalic acid via Diels-Alder reactions on 2,5-dimethylfuran
Table 2 Diels-Alder reactions of 2,5-dimethylfuran to p-xylene
Entry
Catalyst
Conditions
Conv.a DMF (%)
1
Cp2TiCl2/Silica- 180
°C
in
alumina
ampoule under
particles
autogenous
Yield p-
Sel.a p-
Ref.
xylene (%) xylene (%) 92%
69
3-4
70
pressure 2
-
35 bar, 150
3
H − Y zeolite 63 bar, 300 °C
95
76
71, 72
73
Si/Al = 30
in heptane
4
WOx-ZrO2
20 bar, 250 °C
60
77
5
Cu(OTf)2
Dioxane,
35
99
100
Benzoic
84 bar 280 °C
98
92
anhydride
in AcOH
74, 75
bar, 250 °C 6
25 ACS Paragon Plus Environment
76
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
7
Si-Al Aerogel
30 bar, 250 °C
Page 26 of 247
90
60
100
70
67
77
dioxane 8
Sc(OTf)3
9
Zr-Beta zeolite n-heptane, 250
10
35 bar, 200 °C
78
99
90
79
(Si/Zr = 168)
°C, 62 bar
Nanosponge
50 bar, 250 °C
99
79
80
54 bar, 250 °C
64
88
81
67
89
82
type mesoporous beta zeolite 11
0.20WO3/SBA-15700
12
SiO2-SO3H
In heptane Heptane,
250
°C, 45 bar 13
14
15
ZSM-5 zeolite Heptane,
96
nanosheets
250°C, 50 bar
15%-
Dioxane,
HSiW/SiO2
250°C, 20 bar
Potassium-
250°C, 20 bar
70
83
42
70
84
51
42
85
87
93
86
exchanged faujasite
(KY,
Si/Al = 2.6) 16
Nb2O5 NbOPO4
a
and n-Heptane, 250°C, 54 bar
Conv. = Conversion; Sel. = Selectivity
26 ACS Paragon Plus Environment
Page 27 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
In this reaction, the Lewis acid fulfills a double function: it catalyzes the Diels Alder reaction and it assists in the dehydration of the bicyclic ether. Avantium developed a method that uses benzoic anhydride to drive the dehydration reaction (Table 2, Entry 6).76 It is also possible to use ethanol as a precursor of ethylene (A1). Using the zeolite HUSY-12 as catalyst it was possible to react ethanol with DMF at 300 °C to produce p-xylene with 67% selectivity.87 In addition, some other alkylated aromatics were formed with 23% selectivity. The company GEVO developed a process to xylene based on fermentative isobutanol, which was dehydrated to isobutene (A3, see section 11). The isobutene was oligomerized (ZSM-5, 160 °C) to give a mixture of oligomers containing 69% of iso-octenes (primarily 2,4,4-trimethylpentenes). The iso-octene fraction was purified by distillation and subjected to a dehydrocyclization reaction catalyzed by a chromium doped alumina catalyst togive a 40% yield of xylenes, 90% of which was pxylene.88 The oxidation of p-xylene to terephthalic acid is currently performed on very large scale using the Amoco process that uses Co/Mn/Br as catalyst.89
27 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
There is an inherent redox inefficiency in the route via reduction of HMF to DMF and then in the final step oxidation of the methyl groups to the carboxylic acids (Scheme 9). Unfortunately, FDCA itself is too deactivated to undergo Diels-Alder additions. Nevertheless Davis and co-worker examined the possibility to perform the DA reaction on several oxidized and reduced forms of HMF.90 Interestingly all furans with a single carboxylic acid/ester and a methyl, hydroxymethyl or methoxymethyl group did undergo the DA reaction to some extent. However, yields were clearly lower than with DMF. Frost and co-workers developed an interesting route to terephthalic acid from cis-
cis-muconic acid, which is obtained by fermentation.91 First an isomerization of cis-cis to trans-trans-muconic acid is necessary in order to allow the DA reaction. This is possible using Pd/C, I2 or irridation with UV light. Tessonier investigated the isomerization reaction in depth.92 Next, the DA reaction with ethylene (A1) was performed in an autoclave (Scheme 10). More conveniently, isomerization (I2) and cycloaddition were performed in a single step in dioxane at 160 °C and 19 bar ethylene pressure in dioxane to give cyclohex-2-ene-1,4-dicarboxylic acid in 86% yield. In the next step this compound is dehydrogenated with air, catalyzed by Pt/C. 28 ACS Paragon Plus Environment
Page 28 of 247
Page 29 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
In practice it was found that this step works better on the dimethyl ester and dimethyl terephthalate could be obtained in 59% selectivity. 1,4-Cyclohexanedicarboxylic acid was also formed in 8% yield. Lu, Xu and co-workers further optimized these reactions by performing the cycloaddition in ethanol and by using silicatungstic acid as the catalyst leading to very good yields of the cyclohexenedicarboxylic acid.93 An acceptorless dehydrogenation was performed using Pd/C at 200 °C. An overall yield of 81% was achieved over the two steps.
CO2R
CO2R RO2C
CO2R
Pd/C or I2
Pt/C
+
or h
cis-Muconic acid
CO2R
- H2 CO2R
CO2R
CO2R
R= H, Me, Et
Scheme 10. Terephthalic acid/esters from cis-cis-Muconic acid/esters
2.8 Fatty acid based diacids A rather large amount of work has been performed to convert fatty acids into diacids. Most work has been performed using methyl oleate, which is readily available from the methanolysis of high oleic fats such as triolein. A second interesting raw material is ricinoleic acid, which is obtained from castor oil. This fatty 29 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 30 of 247
acid contains a homoallylic alcohol functionality that allows a lot of different chemistry.94 Arkema converts this acid on commercial scale into a number of products (Scheme 11). Pyrolysis of the methyl ester of ricinoleic acid between 450600 °C leads to the formation of 10-undecenoic acid and heptanal. Basic pyrolysis at 250 °C gives a mixture of sebacic acid and 2-octanol.
O OR Oleic acid (R = H) methyl ester (R = Me)
O OH
450-600 °C R = Me OH
+
O
O
H OR
Ricinoleic acid (R = H)
NaOH
O HO
250 °C R = Me
OH O
Sebacic acid +
OH
Scheme 11. Oleic acid (ester) and ricinoleic acid (ester) as raw material for renewable diacids
Sebacic acid is used by both BASF and DSM as raw material for specialty nylons. Arkema converts 10-undecenoic acid into 11-aminoundecanoic acid in a non-catalytic manner. This compound is also used as a nylon monomer.
30 ACS Paragon Plus Environment
Page 31 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
A straightforward reaction to convert methyl oleate into the -di-ester is by performing an isomerizing methoxycarbonylation (Scheme 12, top). This wonderfully efficient reaction was reported by Cole-Hamilton, Eastham and co-worker using the palladium bisphosphine catalyst that was developed for Lucite’s Alpha process (methoxycarbonylation of ethylene (A1) en route to methyl methacrylate).95 The C19-bis-ester was obtained in 82% isolated yield. Mecking and co-workers looked further into this chemistry and found that performing the reaction with a preformed complex [Pd(P-P)OTf]+OTf – instead of a mixture of palladium
O
Pd2(ba)3 / Ligand OMe
O PtBu2 PtBu2 Ligand
O MeO
O O
7
7
O O
7
7
7
7
O
CO, 20 bar, 40 °C MeSO3H, MeOH Pd(OAc)2 / Ligand CO, 30 bar, 80 °C MeSO3H, MeOH
Scheme 12. Isomerizing methoxycarbonylation of methyl oleate and triolein to the C19 diester
precursor and ligand obviated the need for a large excess of ligand and in addition allowed to increase the substrate/catalyst ratio from 60:1 to 500:1.96 In addition, they performed the same reaction on ethyl erucate (the C-22 unsaturated fatty acid ester) to produce diethyl 1,23tricosanedioate. The mechanistic features of this reaction were also investigated by the same 31 ACS Paragon Plus Environment
O OMe
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 32 of 247
group.97 Several other bidentate ligands were also examined.98 Using the same catalyst Köckritz and co-workers were able to convert triolein directly to the1,19-di-ester (Scheme 12, bottom). 99, 100 Cole-Hamilton and co-workers did the same with tall oil, a waste product from the paper industry but they obtained a mixture of diesters. Behr and co-workers examined the use of several different bidentate phosphine ligands in the (isomerizing) methoxycarbonylation of methyl oleate and used a thermomorphic solvent system, which is homogeneous during the reaction but upon cooling down separates into two phases, allowing an easy separation of the catalyst from the product.101 With Xantphos as ligand they obtained a mixture of mainly branched diesters.
Kroth,
Mecking
and
co-workers
performed
the
isomerizing
methoxycarbonylation directly on oil obtained from microalgae.102, 103 They were able to obtain a mixture of the C1,17 and the C1,19 diesters, which they used in a polycondensation reaction with the diols they obtained by reduction of these diesters. Another reaction that has been used extensively in this context is the metathesis reaction. The self-metathesis of methyl oleate was examined as early as 1972 (Scheme 13a, R = Me) Interestingly, although the first generation metathesis catalysts (high oxidation state halide of W, Re, Mo, Ta, Re or Ru in combination with a reducing 32 ACS Paragon Plus Environment
Page 33 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
agent such as BuLi, PhSiH2, Me4Sn, EtAlCl2) normally only work on unsubstituted alkenes and are strongly inhibited by heteroatoms, they can be used for the metathesis of fatty acid esters (not the acids). Boelhouwer and co-workers showed that reacting methyl oleate with a catalyst made in situ from WCl6 and Me4Sn at 343°K in chlorobenzene led to an equilibrium mixture of approximately 50% methyl oleate, 25% of the unsaturated 1,18-diester and 25% of 9-octadecene. Nevertheless, they were able to separate the diester by crystallization. A heterogeneous catalyst, Re2O7/SiO2.Al2O3 activated with SnR4 or PbR4, also was highly active in this reaction.104 Although one would expect that distillation of the alkene would shift the Metathesis Catalyst
a. 7
R = Me R=H
b.
7
CO2R
RO2C
50% 20%
CO2Me
7
7
CO2R
25% 40% ( ) Metathesis Catalyst
MeO2C 8
8
8 CO2Me
+
7
7
25% 40%
+ H2C=CH2
Scheme 13. Self-metathesis of methyl oleate and oleic acid (a) and of methyl 10undecenoate (b)
33 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 34 of 247
equilibrium to the desired diester, this has not been reported; perhaps the boiling point of the alkene is too high for this, even under vacuum. Ngo and coworkers showed that self-metathesis of unsaturated fatty acids is possible with the Grubbs 2nd generation catalyst and that yields in excess of 70% of the diacids are obtained as the equilibrium is shifted by precipitation of the diacid during the reaction (Scheme 13a, R = H).105 The self-metathesis of methyl oleate was also performed by Mol and co-worker, using the Grubbs I as well as the 2nd generation Grubbs II catalyst, reaching extremely high turnover numbers in the absence of solvent.106 Researchers of Sassol and Umicore reported a phobane containing Grubbs type catalyst for this reaction, achieving high turnover numbers.107 PCy3 Cl Ru Cl
Mes N
Mes N
Ru
Cl Ru
Ph
Cl
Cl
PCy3
Grubbs I
N Mes
Cl
Ph
PCy3
N Mes
Grubbs II
Mes N
O
Hoveyda
N Mes
Mes N
N Mes
Cl
Cl
Ru Cl
Ru Ph
O Cl
PCy3 Sassol/Umicore
Umicore 1
O
Umicore 2
Figure 3. Metathesis catalysts 34 ACS Paragon Plus Environment
Page 35 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
Meier and co-workers reported the self-metathesis of methyl 10-undecenoate (from Ricinoleic acid, vide supra) using Grubbs I, Grubbs II and Grubbs-Hoveyda 2nd generation catalysts (Scheme 13b).108 Here the reaction goes to near completion as the volatile side product ethylene (A1) can be removed. Extensive isomerization of the double bond of the product was found, which is due to the formation of small amounts of ruthenium hydrides. This could be suppressed by the addition of small amounts of benzoquinone. Meier and co-worker examined the cross-metathesis of methyl oleate with methyl acrylate (Scheme 14a, R = H).109 The first generation Grubbs catalyst was inactive and use of the second generation Grubbs catalysts led to a mixture of cross-metathesis and self-metathesis products. However, using the Grubbs-Hoveyda catalyst (5 mol%) 99% selectivity to the cross-metathesis product was achieved using a 10-fold excess of methyl acrylate. Gauvin and co-workers found that at lower catalyst loadings selfmetathesis became a major side-reaction. However, by replacing methyl acrylate with methyl crotonate they avoid formation of the highly unstable ruthenium-methylidene intermediate and thus very high selectivities to the cross-metathesis product were 35 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 36 of 247
obtained with turnover numbers up to 37 000 using Umicore’s metathesis catalysts (Figure 3, Umicore 1 and 2; Scheme 14a R = Me).110
a.
7
7
CO2R
+ R
Metathesis Catalyst CO2Me
R = H, Me b.
CO2Me 8
+
MeO2C 7
Metathesis Catalyst
CO2Me
MeO2C
CO2Me
CO2Me 8
+
R 7
+ H2C=CH2
Scheme 14. (a) Cross-metathesis of methyl oleate with methyl acrylate or crotonate; (b) cross metathesis of methyl 10-undecenoate and methyl acrylate
Meier and co-workers also reported the cross-metathesis between methyl 10undecenoate and methyl acrylate with 99% selectivity to cross-metathesis using 0.1 mol% of the Grubbs-Hoveyda 2nd generation catalyst (Scheme 14b).109 Fischmeister, Bruneau and co-workers found that slow addition of the same catalyst to the reaction mixture allowed them to reach up to 7600 turnovers with the same reaction.111 A third method to obtain diacids or esters from unsaturated fatty acids or esters is via oxidation. Traditionally oleic acid has been subjected to ozonolysis followed by oxidative work-up to give a mixture of the di-acid azelaic acid plus pelargonic acid. In view of the dangers associated with the use of ozonolysis on large scale, many groups
36 ACS Paragon Plus Environment
Page 37 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
have examined the oxidative cleavage of oleic acid or ester to the same products using other less dangerous oxidants. Two recent reviews have appeared that summarize the catalysts that have been developed.112, 113 The best results thus far have been obtained using catalysts based on tungsten. In particular Venturello and co-workers from the Italian company Novamont developed a tungsten peroxo catalyst of formula [(nC8H17)3NCH3]3[PO4[W(O)(O2)2]4] that could be used in the oxidation of oleic acid with 5.5 eq of 40% H2O2 without any added solvent at 85 °C. With this procedure good yields of azelaic acid (79%) and pelargonic acid (82%) could be obtained. Nevertheless, this procedure is still rather expensive in view of the large excess of hydrogen peroxide used. Thus, Novamont developed a two-stage procedure in which oleic acid was first oxidized at 62 °C with 1 equiv of hydrogen peroxide catalyzed by H2WO4 to the dihydroxide. Next a cobalt salt is added and the reaction is continued under the pressure of 22 bar of air at 72 °C (Scheme 15). In the industrial practice this is done on the oil itself. This allows the easy separation of the monocarboxylic acid and next the triglycerate is hydrolyzed to give the diacids and glycerol. In this way yields of around 80% of both azeleic acid (AZA) and pelargonic acid (PA) were obtained from high oleic sunflower oil (containing 82% of oleic acid).114 Oxidation of the dihydroxy 37 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 38 of 247
compound is also possible using 0.2 Mol% of Au/Al2O3 as catalyst and O2 (5 bar) at 80 °C for a yield of 86% of AZA and 99% of PA.115 [n-Oct3NMe]3[PO4[W(O)(O2)2]4] 5.5 eq. 40% H2O2
7
7
CO2R
H2WO4 H 2O 2
HO
OH 7
7
CO2R
Co(OAc)2
H+
Air, 22 bar
H 2O
HO2C
CO2H Azeleic acid CO2H
R = Me R = OCH2CH(O2CR)CH2O2CR
Pelargonic acid
Scheme 15 One- and two-step oxidation of methyl oleate or high oleic sunflower oil.
Park and co-workers studied the enzymatic conversion of fatty acid precursors into diacids using a cascade of enzymatic conversions, using hydratases, alcohol dehydrogenases, Baeyer-Villiger mono-oxygenases and esterases. They were able to achieve yields of diacids between 50 and 70%.116,
117
Ogawa reported the use of
laccases for the oxidative cleavage of unsaturated fatty acids to the diacids.118 Schirp and co-workers reexamined the rhodium-catalyzed Diels-Alder-like reaction between methyl oleate and maleic anhydride that was discovered earlier by Behr and co-workers.119, 120 They found that depending on the type of rhodium catalyst either mostly the Diels-Alder product was formed or a mixture of the Diels-Alder product and the product of the ene reaction (Scheme 16). 38 ACS Paragon Plus Environment
Page 39 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
7
CO2R 7
+
O
O
1. Rh(OAc)2 or RhCl3 O
MeO2C
2. MeOH/H2SO4
CO2Me CO2Me +
6
6
Rh(OAc)2 RhCl3
CO2Me MeO2C CO2Me
m
n
DA
Ene
97% 34%
3% 66%
Scheme 16. Rhodium-catalyzed reactions between oleic acid and maleic anhydride
Hachihama and Hayashi reported the aldol condensation between furfural and levulinic acid to give the unsaturated keto ester which can be hydrolyzed to the levulinic acid dimer (Scheme 17).121 Heating this dimer formed 2,5-furandipropionic acid in 93% yield. Deng, Fu and co-workers performed the hydrogenation of the dimer using Pd/C and W(OTf)6 as catalysts to give sebacic acid in 88% yield.122 O O
CHO
CO2H
NaOH
+
CO2H
EtOH H2O, 58 °C
O
O HCl/EtOH Reflux
HO2C
O
CO2H
O
180-190 °C HO2C
CO2H O Pd/C, W(OTf)6 H2 (30 bar), HOAc 180 °C
HO2C
CO2H
Scheme 17 Diacids from furfural and levulinic acid
2.8 Other diacids 39 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 40 of 247
Amarasekara and co-workers reacted fructose with DOWEX 50 W X8 ion exchange resin in DMSO to give 5,5’-[oxybis(methylene)]bis[2-furfural], which was oxidized to the diacid using Pt/C and 1 bar of O2 in 1.5M NaOH (Scheme 18a).123 Gandini and co-workers took ethyl 2-furancarboxylate and condensed it with acetone, catalyzed by sulfuric acid to obtain the diester in 65% yield (Scheme 18b).124
HOCH2
O HO
a. HO
b. O
OH CH2OH
CO2Et +
Pt/C, O2
DOWEX DMSO 110 °C
O
OHC
H2SO4
O
O
O
EtO2C
CHO 1 M NaOH HO2C
O
O
O
O
O
CO2H
CO2Et
Scheme 18 Diacids from fructose and from furfural
3. Diols Diols are monomers for the production of important polymers such as polyesters and polyurethanes. Diols like 1,3-propanediol, or 1,4-butanediol can be produced very efficiently biotechnologically; this will not be discussed. The diols shown in Figure 4 can be produced by catalyzed processes from biomass or from platform chemicals.
40 ACS Paragon Plus Environment
Page 41 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
OH
OH
HO
HO
OH
D3
D2
D1 HO
OH
HO O D6
OH
OH
D7 OH
HO
O
HO
O
D4
OH
O
HO
D5
OH
D8
HO
OH
HO
OH n D10
D9
n
Figure 4. Diols covered in this review
3.1 Ethylene glycol (D1) The Chinese company Dacheng hydrogenates sorbitol using a Ni/Ru catalyst in the presence of NaOH at 230 °C and 120 bar H2 (Scheme 19a).125 This produces a mixture of ethylene glycol (D1), 1,2-propanediol (D2), glycerol and 2,3-butanediol.126 This process is run on a scale of 200 kton/year. Many publications and patents exist on the hydrogenolysis of sorbitol.127 In most of these, heterogeneous nickel, ruthenium, or a combination of the two are used in the presence of base. Nevertheless, iridium, rhodium, palladium, platinum, osmium and copper catalysts, often in conjunction with other metals, have also been used. It is assumed that the mechanism of formation of ethylene glycol follows this pathway: Sorbitol is dehydrogenated to the aldose, which
41 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
undergoes a retro-aldol reaction to form glycolaldehyde, which is hydrogenated to ethylene glycol. The two first steps benefit from the presence of base. Homogeneous catalysts have also been used. Good yields of D1 and D2 were obtained using a catalyst made in situ from Ru(acac)3 and triphos at 250 °C and 70 bar H2.128 Zhang, Chen and co-workers used a 2%Ni/30%W2C on activated carbon catalyst for the hydrogenolysis of cellulose at 245 °C and 60 bar H2 and achieved up to 61% yield of D1 at 100% conversion (Scheme 19b).129 Increasing the amount of nickel in the catalyst to 10% further improved the yield to 73%.130 Other catalysts that have been used for this conversion are: Ru/WO3, H2WO4/Ra-Ni, Ni/ZnO, Pt/H-ZSM-5 and Ru/ZrO2. The area has been reviewed.131 Zhang and co-workers subjected glucose to hydrogenolysis catalyzed by ammonium tungstate/ruthenium on activated carbon at 240 °C and 50 bar H2.132 They achieved a selectivity to D1 of 50%. In a later publication the effect of the dosing rate of the glucose solution as monitored.133 Slow dosing led to a further increase in selectivity to D1 of 70% (Scheme 19c). Extensive research has been performed on the hydrogenolysis of glycerol.134-136 Major products are 1,2-propanediol (D2), 1,3-propanediol and to a lesser extent 42 ACS Paragon Plus Environment
Page 42 of 247
Page 43 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
ethylene glycol, ethanol, propanol and methane. It is assumed that ethylene glycol is formed by dehydrogenation of glycerol to glyceraldehyde, which can undergo retroaldol reaction to glycolaldehyde and formaldehyde. Further hydrogenation leads to the formation of ethylene glycol and methane. Tomishige and co-workers managed to make ethylene glycol the major product (47% selectivity) by using a platinum doped nickel catalyst in the hydrogenolysis of glycerol in water at 180 °C and 80 bar H2 (Scheme 19d).137
a.
OH
HO
HO
Ni/Ru H2 (120 bar)
OH OH
H2O, 230 °C
OH OH
OH
OH
OH OH
OH OH
HO
OH b.
2%Ni30%W2C/AC H2, 60 bar
Cellulose
HO
H2O, 245 °C
OH c.
O
HO HO
OH
OH 61%
(NH4)10(H2W12O42)4.H2O/Ru/AC H2, 50 bar
HO
H2O, 240 °C
OH
70%
Glucose
d.
OH HO Glycerol
OH
0.5%Pt/5%Ni/-Al2O3 H2, 80 bar H2O, 180 °C
HO
OH
48% sel.
Scheme 19 Ethylene glycol from renewable resources
3.2 1,2-Propanediol (D2)
43 ACS Paragon Plus Environment
OH
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Propylene glycol (D2) which is used to modify crystallinity in polyesters such as PET can be obtained by hydrogenolysis from glycerol at around 200°C using heterogenous catalysts such as Ru/MgAlO4,138 Re-Ru/SiO2,139 Pt-H4SiW12O40,140 Cu-Zn/MgAlO4141 or Cu/MgO (Scheme 20).142 Interestingly, high selectivities of 90-94% at full conversion can be obtained using CuZn/MgAlO4 in combination with basic additives or on Cu/MgO using water as solvent. For reviews, see 3.1. Another strategy to obtain 1,2-propanediol from biomass is the hydrogenation of lactic acid and its esters (Scheme 20). For the homogenous hydrogenation of methyl lactate ruthenium complexes in combination with basic additives have been used.143146
Yields and selectivities are typically close to 100% and the reaction temperature
below 100°C. Further, using homogenous Ru-PNP catalysts allows retaining the stereochemistry when enantiopure lactic acid esters are used,143 this might be important for the development of polymers with higher crystallinity. The direct hydrogenation of lactic acid is more challenging using homogenous catalysts and has only recently been accomplished in an effective manner using N-Triphos complexes of ruthenium.147 With heterogeneous catalysts this reduction is likewise conducted using ruthenium on carbon at around 120°C.148 The activity can be increased (3-4x) by adding small amounts of molybdenum oxide149 or using TiO2150 as support instead of carbon. 44 ACS Paragon Plus Environment
Page 44 of 247
Page 45 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
OH HO
OH
H2 OH OH D2
OH
H2 O
H/R
O
Scheme 20. Biobased routes to 1,2-propane diol
3.3 1,4-Butanediol (D3) For the production of 1,4-Butanediol D3 both catalytic and biotechnological syntheses seem viable. Novamont has opened a plant for the fermentative production of D3, based on the Genomatica process. On the other hand, several companies have announced fermentative production of succinic acid. Succinic acid can be hydrogenated at high temperatures and pressure of hydrogen to D3 in over 90% selectivity using several bimetallic heterogenous catalysts such as Pd/Re, Ru/Re, Ru/Sn, Pd/Ag/Re, Pd/Zr on several different carrier materials (Scheme 21). This area has been reviewed.151
HO2C
Catalyst CO2H
H2
HO
OH D3
Scheme 21. Succinic acid to 1,4-butanediol 45 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 46 of 247
Nakagawa, Tomishige and co-workers reported the selective conversion of 1,4anhydroerythritol into 1,4-butanediol.152 Erythritol, which is produced by fermentation, can be ring-closed to form anhydroerythritol (3,4-dihydoxy-tetrahydrofuran). They used a combination of ReOx-Au/CeO2 and ReOx/C-BP (C-BP is carbon black BP2000) as catalyst and 80 bar H2 in dioxane at 140 °C to convert anhydroerythritol, to 1,4butanediol with 86% selectivity at 100% conversion (See Scheme 22). Analysis of the reaction products delivered evidence for a route via didehydroxylation to 2,5dihydrofuran, which is ring-opened by reaction with water (presumably on the isomeric 2,3-dihydrofuran) to form 2-hydroxy-tetrahydrofuran which ring-opens to 4hydroxybutyraldehyde, which is further reduced to D3.
HO
OH O
ReOx-Au/CeO2 ReOx/C-BP H2, 80 bar dioxane 140 °C
O HO O
O
OH
H
HO
OH D3
Scheme 22. 1,4-butanediol from anhydroerythritol
3.4 1,4-PDO (D4) Interest in 1,4-pentanediol dates back to the world war II era when it was investigated as potential precursor for renewable pentadienes as raw material for rubber.153
46 ACS Paragon Plus Environment
Page 47 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
Nowadays D4 is regarded as an interesting building block for the synthesis of novel fully or semi renewable polyurethanes and polyesters, which might have several novel properties. Scheme 23 shows the two main routes to 1,4-PDO from levulinic acid which can be obtained from lignocellulose. O O
GVL
O OR
OH
HO
O
D4
ML R = Me LA R = H
Scheme 23. Pathways to 1,4-PDO
Table 3. Heterogeneous catalyst for the synthesis of 1,4-PDO with reported yields over 80% Entry
Catalyst
Substr
T
p(H2
ate
[°C]
) bar
S/Ca
Solve
Conv.b
Sel.b(1,
nt
[%]
4-PDO)
Ref.
[%] 1
Re-Ru
LA
240
150
2290
Wate
80
>99
154
97
>93
155
99
156
r 2
Pt-Mo0.25
LA
200
30
50
Wate r
3
Cu-ZrO2
GVL
200
30
10
Ethan 100 ol
aS/C=Substrate/Catalyst b
Conv. = Conversion; Sel. = Selectivity 47 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Heterogeneous hydrogenation of LA or GVL is possible but at present not many effective systems have been found. One of the difficulties in the heterogeneous hydrogenation of GVL to 1,4-PDO is that decarbonylation of GVL to 2-butanol has a lower energy barrier than the hydrogenation of the surface intermediate.157 In addition, high temperature and acidic sites can convert the formed 1,4-PDO to 2-MeTHF.158 Table 3 lists recent catalytic systems were yields of 1,4-PDO over 80% have been achieved. Notably when LA is directly hydrogenated to 1,4-PDO the reaction is conducted in water which is most likely to suppress 2-MeTHF formation. The homogenous hydrogenation of GVL, LA or LA esters on the other hand leads to high yields and selectivities. Table 4 gives an overview of reported catalysts which gave more than 90% yield of 1,4-PDO. Usually GVL or ML are used as substrates, levulinic acid itself is typically not tolerated by most catalysts. The exceptions are ruthenium triphos complexes (Table 4, Entry 1). However, relatively high pressures and temperatures and relatively high loadings are needed with this type of catalyst. Further acidic conditions lead to ring-closing of D4 to 2-MeTHF, which has been exploited to selectively synthesize 2-MeTHF from LA159 or GVL.160 PNP complexes of manganese and iron are also active catalysts for the hydrogenation of GVL to 1,4-PDO 48 ACS Paragon Plus Environment
Page 48 of 247
Page 49 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
but need loadings between 2-3% which might be attributed to the higher sensitiveness towards impurities and lower activity. A base metal catalyst which surprisingly shows a high TON and activity is the cationic cobalt complex developed by Brennessel/Jones and coworkers. Here, without the need of a solvent a TON of 920 could be achieved in 5 hours.
Table 4. Precatalysts for the homogenous hydrogenation of LA, ML and GVL to 1,4PDO, with documented 1,4-PDO yields over 90% Substrate
Complex
(S/C)
Solven
p(H2)
T
t
[bar]
[°C]
-
THF
75
140
16
99a
161
-
THF
75
140
16
99a
161
50
140
16
98a
161
100
25
48
90
145
50
25
6
97
145
Additive
t [h]
Y [%]
Ref.
GVL (100) Ph2P P Ph2
PPh2 Ru
ML
Klankermeyer/Leitner
(100)
1,4-
LA
-
(50)
N
Cl
P(tBu)2
Ru N
Cl
Zhou
NEt2
e NaOMe
GVL (100000)
ML
Dioxan
(10 mol- iPrOH %) NaOMe
iPrOH
49 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
(1000)
Page 50 of 247
(10 mol%)
PEt2 H H N Fe CO PEt2
GVL
HBH3
(50)
-
THF
30
100
18
98
162
KOtBu
1,430
110
24
95a
163
-
60
80
2
91
164
-
55
120
5
92
165
Beller Br H
PEt2
N
Mn
P Et2
CO
GVL
CO CO
(33)
Beller
(10 mol- Dioxan e %)
Cl
H N
S Ru
N
Cl
GVL
PPh3
(2000)
de Vries
KOtBu (2.5 mol-%)
BAr4F
H N
PCy2 Co
P HCy2
CH2TMS
GVL (1000)
-
Brennessel/Jones aDetermined
by GC or NMR others are isolated yields
3.5 1,5-Pentanediol (D5)
50 ACS Paragon Plus Environment
Page 51 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
The current market capacity for 1,5-pentanediol is 3000 tons per year. Due to its structural similarity it is a potential renewable substitute for 1,6-hexanediol (1,6-HDO) in thermoplastic polyurethanes, which could add to its market growth.166 O
O
H2
H2
OH
O
Ni THFA
RhRe,ReMo or NiLa
Al2O3
HO
OH
H2
H 2O
O
DHP
O
Ru
OH
2HY-THP
Scheme 24. Synthesis of 1,5-PDO from furfural
As shown in Scheme 24, 1,5-PDO can be obtained from furfural which is currently produced from hemicellulose on an annual scale of >300 kt.167 The most obvious route to 1,5-PDO from furfural seems hydrogenation to tetrahydrofurfuryl alcohol (THFA)168 followed by hydrogenolysis over bimetallic rhodium-rhenium or nickel-lanthanide catalysts.169-173 Although conversions are general acceptable (47-99%) and selectivities are good (78-97%), in a techno-economic analysis it was found that the high catalyst loading and thus catalyst cost is a limiting factor.166 This led to the development of an alternative route by Brentzel et. al via dihydropyran (DHP).174 Here 51 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 52 of 247
THFA is first dehydrated in the gas phase over aluminum oxide at a weight hourly space velocity of 9 h
-1
in 87% yield.
The DHP is then hydrated to 2-hydroxy
tetrahydropyran (2HY-THP) by adding it to water at 130°C. As hemiacetal, 2HY-THP is in equilibrium with its aldehyde form, making its hydrogenation catalyzed by Ru/TiO2 under mild conditions possible. 1,5-PDO can be produced in an overall yield of 84%. Tomishige and co-workers managed to hydrogenate furfural directly to 1,5-PDO in 71% yield by using Rh-Ir-ReOx/SiO2 as catalyst in a hydrogenation using two different temperatures (313 K for 8 h and 373 K for 24 h).175, 176
3.6 Isosorbide (D6) Isosorbide is considered an interesting building block for the plastics developer’s toolbox as its incorporation in polyesters177,
178
allows increasing glass transition
temperature and thus allows fine-tuning of crystallinity. The reaction with isocyanates leads to the formation of highly elastic polyurethanes.179 The bio-based resource for the production of isosorbide would be glucose obtained from the depolymerization of polysaccharides such as cellulose (Scheme 25).180 The glucose can then be hydrogenated to sorbitol. As hydrogenation catalysts nickel181, 182 and ruthenium183, 184 can be used. Acid catalyzed dehydration can then be used to obtain isosorbide via 52 ACS Paragon Plus Environment
Page 53 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
1,4-sorbitan and 3,6-sorbitan as intermediates (Scheme 25).180, 185, 186 When Brønsted acids are used as catalyst selectivity towards isosorbide is correlated to the pKa-values of the acid.187 Conversion and selectivity are increasing with falling pKa-values till -1.9 (methanesulfonic acid) at which point a plateau is reached and the selectivity for isosorbide is 66-68% at 100% conversion, formation of humines amounted to 12-16%. Further improvements include continuous dehydration in hot steam188 or esterification of sorbitol with dimethyl carbonate followed by intermolecular nucleophilic substitution.189 Lewis-acids in general also catalyze the dehydration reaction, however since water is produced during the reaction it is necessary to employ water stable metal triflates. Liu et. al were able to obtain isosorbide from sorbitol in 85% yield using 3.6 mol-%Bi(OTf)3.190This is the only exception to the rule that the yields using Lewis-acids are lower than those obtained with Brønsted acids.186 For use in continuous processes group (IV) phosphates were also studied as dehydration catalysts.191, 192
53 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 54 of 247
H2 OH OH
OH OH O
HO
OH
HO
OH OH
OH OH
Glucose
Sorbitol
HO
OH HO HO
OH
O
O
OH HO
OH
1,4-Sorbitan
3,6-Sorbitan
HO O O OH Isosorbide (D6)
Scheme 25. Conversion of glucose to isosorbide
3.7. 2,5-Furan-dimethanol (D7) and 2,5-tetrahydrofuran-dimethanol (D8)
2,5-Furan-dimethanol D7 and 2,5-tetrahydrofuran-dimethanol D8 are both interesting building blocks for polyurethanes or polyesters.193, 194 D8, however should have the broader applicability due to the lower likelihood of colorful side products formation during polymerization or consumer usage. As shown in Scheme 26, D7 and D8 can both be obtained by the hydrogenation of the platform chemical 2-HMF. As stated
54 ACS Paragon Plus Environment
Page 55 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
before in this review 2-HMF is available via acidic treatment of fructose. As 2-HMF is a key platform chemical for the biorefinery industry there is an exceptional growth in literature referring to its hydrogenation to D7 (about 81reports from 2017-2018). A recent review by Royer and co-workers covers most of this research.195 Most of the work focuses on the use of Cu supported on SiO2 or ZnO or Au or Pt on basic supports such as CeO. With these types of catalysts, generally excellent selectivities can be obtained. The reaction is typically carried out at 100°C and pressures of 1560 bar with water or THF as solvent. For the direct hydrogenation of HMF to D8 Ru/C160 can be used giving yields of up to 90%. Recent work however focuses more on Co and Ni based systems typically as Raney type materials,159, 196 which give similar performance but having cost advantages.
H2 HO
O
O
HO
O
OH
Cu, Au, Pt >96% Selectivity 5-HMF
D7
4-4
0b
ar Ra H 2 12 ne y 0 C oo Me °C rN OH i
HO
OH
O
D8 95-99%
Scheme 26. 2,5-furan-dimethanol and 2,5-tetrahydrofuran-dimethanol from HMF 55 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 56 of 247
3.8 1,6 Hexanediol D9
The current petrochemical based route to 1,6-hexanediol D9 starts from the oxidation of cyclohexanone or cyclohexanol to adipic acid197 which is then hydrogenated to D9.198 As described in section 2 of this review adipic acid (AA) can be obtained from sugars, LA or HMF as renewable resources, allowing a drop-in strategy in the existing hydrogenation processes. The hydrogenation of adipic acid and its esters is a well-known and optimized process in the chemical industry and as such not in the scope of this review.199 Another important bio-based platform chemical for the synthesis of D9 is 5-HMF. Scheme 27 gives an overview of the processes from bio-derived molecules to D9.
O
O
O
H2 O
O
O
H2
Pd/C
O
O Pd/C Cyrene
LGO
OH LGOL H2
HO
O 5-HMF
O
H2 Raney Ni Pd/C
O RO
HO
OR O Adipic acid/esters
Pd/Si-Al
O
OH
ReRh/SiO2 + solid acid or IrRe
HO
OH
H2 D9
THFDM D8
H2 Rh-Re/SiO2
H2
OH O
O
Ni/C
OH H 2O
O
-H2O TH2PM
THO
OXL
Scheme 27. Conversion of renewable resources to 1,6-hexanediol (D6)
As described earlier in this section 5-HMF can be hydrogenated to 2,5-tetrahydrofuran dimethanol (THFDM) D8 which itself is an interesting building block for polyesters.200 Besides 5-HMF levoglucosenone (LGO) is a potential feedstock. LGO can be obtained from cellulose 56 ACS Paragon Plus Environment
Page 57 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
via acidic treatment with sulfuric acid at 170-230°C in 51% yield.
201
It is then possible to
hydrogenate LGO at 40°C to Cyrene, a potential green and high boiling solvent.
202
Further
hydrogenation leads then via levoglucosenol (LGOL) to the THFDM. The THFDM can then be hydrogenated to D9 using heterogeneous RhRe/SiO2 with Nafion or IrRe catalysts196, 203-207 or in newer approaches with Pt-WOx/SiO2.208 An alternative is a stepwise hydrogenationdehydration-hydration-hydrogenation approach.209 First THFDM is hydrogenated via the intermediate 1,2,6-hexeane triol to tetrahydropyran-2-methanol (TH2PM).210 TH2PM is then dehydrated over zeolites. This is followed by rehydration, which yields 2-oxepanol (OXL) that due to being a hemi-acetal can be easily hydrogenated quantitatively with Ni/C to D6. This process sequence thus allows using only the non-precious metal nickel as hydrogenation catalyst.
3.9 Long-chain α–ω diols (D10) Long-chain diols are currently produced in industry from unsaturated fatty acids, which upon heating dimerize via Diels-Alder reactions.211 The obtained dimer-fatty acids can then be hydrogenated to diols which find application in polyurethanes. Due to their branched structure these diols often have plastifying effects. To obtain linear diols from unsaturated fatty acids a sequence of isomerizing methoxycarbonylation (which is described in the section about diacids of this review) followed by hydrogenation, can be employed.96,
99, 212
Catalysts that have been used for this
purpose are Saudan’s ruthenium catalyst, ruthenium/Triphos, and Milstein’s RuPNN 57 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 58 of 247
pincer catalyst. The metathesis reaction and hydrogenation can also be combined in a one pot process.213 For example renewable methyl oleate can be dimerized via selfmetathesis using Grubbs catalysts. To hydrogenate the diesters to the desired α–ω diols simply 2-(diphenylphosphanyl)ethan-1-amine (the ligand of the Saudan ester hydrogenation catalyst) and a base such as KOtBu is added which allows hydrogenation of the esters moieties, yielding long-chain diols in excellent yields (Scheme 28). O 7
7
[Ru] 50°C neat, 3h
O
Mes N Ru= Cl
O O
N Mes Cl
Ru PCy3 Ph
7
7
O
H2 50 bar
O
L + tBuOK 70°C 70°C, 16 h
OH
HO 7
7
99% Yield
PPh2 L= NH2
Scheme 28. Tandem metathesis hydrogenation of methyl-oleate
4. Hydroxy acids / hydroxy esters. Hydroxy-acids and esters are important classes of monomers for polymer production.214 In this sub-chapter catalytic routes towards important monomers of
58 ACS Paragon Plus Environment
Page 59 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
these classes will be described (Figure 5). Only efficient / best routes from renewable resources will be discussed. O
O OH
HO
HO HA2
HA1
O OH
HO
OH HA3
O
O
O
OH
OH
O
HA4
HA5 OH
O
O
O
HO
17
OH OH HA6
O
HO
O OH
HA8
HA7
Figure 5. Selected hydroxyacids as monomers for polymers.
4.1 Glycolic acid. Glycolic acid is the only 2-carbon hydroxy acid. It has been obtained by oxidation of cellulose with 6 bar of oxygen in water at 180 °C using H4SiMo12O40 as catalyst in 41% yield.215 A similar yield was obtained by oxidation of glucose or cellobiose at 150 °C with H3PMo12O40 as catalyst. It can also be prepared from ethylene glycol via an Oppenauer type oxidation using cyclohexanone as oxidant and Grützmacher’s 59 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 60 of 247
rhodium-complex as catalyst as shown in Scheme 29.216 An advantage of this method is the absolute selectivity to the desired product as well as the requirement of nonexpensive readily available reagents.
OH
HO
i) 0.1 mol% Rh catalyst 1.2 eq. NaOH 2.5 eq. cyclohexanone H2O, RT, 2 h ii) aqueous HCl
N Rh O OH HO HA1 (99%)
PPh3 Grützmacher catalyst
N H
N H
Scheme 29. Preparation of glycolic acid (HA1) from ethylene glycol.
Glycolic acid can also be prepared from glycerol. Up to 77% yield of the desired product can be achieved with ZnO as a catalyst and hydrogen peroxide as the oxidizing agent (Scheme 30).217
OH HO
OH
50 wt% ZnO excess H2O2
O
H2O, UV irradiation 3h
OH HO HA1 (77%)
Scheme 30. Preparation of glycolic acid (HA1) from glycerol.
Alternatively, HA1 can be also prepared from tartaric acid under oxidative conditions (Scheme 31).218 The N-G catalyst, which is used here, is a form of pyrolyzed polysaccharide chitosan. It is assumed that a retro-aldol reaction takes place to glycolic acid and glyoxylic acid, which is further oxidized to oxalic acid.
60 ACS Paragon Plus Environment
Page 61 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
OH
O
OH
HO OH
O
33 wt% N-G catalyst O2 (18 bar) H2O, 160 oC, 10 h
O OH HO HA1 (91%)
Scheme 31. Preparation of glycolic acid (HA1) from tartaric acid.
4.2 3-Carbon hydroxy acids.
Lactic acid and 3-hydroxy-propionic acid are 3-carbon hydroxy acids which are used in the production of polymers. Lactic acid is produced on large scale via fermentation (mostly L-Lactic acid). In 2013 Wang et al. reported the conversion of biomass to lactic acid in the presence of a lead catalyst as shown in Table 5.219 The reaction is performed under 30 bar of nitrogen gas in the presence of a lead catalyst and water only with no requirement of any other reagents. While cellulose, inulin and starch consist of C6 and C5 sugars, the other polymers (Entries 4-6) are basically lignocellulose containing lignin, which cannot be converted to lactic acid. The following percentages of C5 and C6 units are present in these biopolymers: sugar bagasse (72.6 wt%), couch grass (66.5 wt%) and bran (72.6 wt%). Table 5. Direct synthesis of lactic acid (HA2) from different biomass sources.
biomass
Entry
1
2
O
Pb(NO3)2 H2O, N2 (30 bar) 190 oC
Biomass
Cellulose
Inulin
OH
HO HA2
Pb(NO3)2
Reaction time, Yield of HA2
loading
(h)
(%)
20 mol%
4
68
4 mol%
10
59
46 wt%
2
73
61 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
3
Starch
4
Sugar bagasse
5
Couch grass
6
Bran
Page 62 of 247
1.84 wt%
15
41
46 wt%
2
68
1.84 wt%
15
58
46 wt%
15
40 (66)*
1.84 wt%
24
37 (62)*
46 wt%
15
45 (81)*
1.84 wt%
24
33 (60)*
46 wt%
15
64 (92)*
1.84 wt%
24
52 (75)*
*yield based on C5 and C6 units in the biomass
While only average yields are achieved with this approach, it is a convenient way to prepare lactic acid directly from biomass. Using glycerol-derived components as the substrates, very high yields of lactic acid could be achieved with the same catalytic method (Table 6). Table 6. Direct synthesis of lactic acid via isomerization of C3-renewable sources using a Pb(II) catalyst.
triose
Entry
O
27 mol% Pb(NO3)2 H2O, N2 (30 bar) 190 oC, 2 h
Substrate
OH
HO HA2
Yield of lactic acid, %
1
glyceraldehyde
95
2
dihydroxyacetone 92
62 ACS Paragon Plus Environment
Page 63 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
3
pyruvaldehyde
91
Glycerol can also serve the role of the starting material in the preparation of HA2. Crabtree and co-workers reported a highly efficient Iridium catalyst to perform this reaction (Scheme 32).220 Selectivity towards lactic acid is >96%; side products are ethylene glycol and 1,2-propane diol. At lower catalyst loadings (0.002 mol%) a TON of up to 30100 was achieved. 0.036 mol% cat. 6.7 mol% H2O 1.1 equiv KOH
OH HO
OH
115 °C, 24 h
OH OH O HA2, 91%
N
N N
Ir
N
OC CO
Scheme 32. Lactic acid from glycerol
Taarning and co-workers treated sucrose in methanol at 160 °C with zeolites and zeotype compounds.221 He obtained a yield of 68% methyl lactate using Sn-beta as catalyst (Scheme 33). The reaction proceeds via a retro-aldol reaction of fructose and Sn-beta also catalyzes the isomerization of glucose to fructose. In addition, some methyl vinylglycolate is also formed via retro aldol reaction of glucose.
63 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 64 of 247
HO HO
O
HO
HO
OH
O
O OH
HO
OH
Sn-Beta
+
OH
CO2Me
MeOH, 160 °C OH
CO2Me
68%
Sucrose
8%
methyl lactate
methyl vinylglycolate
Scheme 33. Methyl lactate from sucrose
An efficient catalytic method to prepare 3-hydroxy-propionic acid is shown in Scheme 34.222 A Baeyer-Villiger oxidation of levulinic acid gives the alkyl hydroperoxide in good yield, which was easily hydrogenated to the desired product in 82% overall yield. i) H2O2, KOH ii) HCl
O HO O
O HO
0 oC -> RT
O
0.11 mol% Pd / C OOH MeOH, H2 (3.9 bar) 40 min 82%
HO
OH
HA3, 100%
Scheme 34. Preparation of 3-hydroxy-propionic acid (HA3) from levulinic acid in 2 steps.
An alternative method to prepare compound HA3 was described by Ide and Davis.223 1,3Propanediol was oxidized to the desired compound in the presence of a platinum catalyst and oxygen gas (Scheme 35). A 90% conversion and over 95% selectivity towards 3 were achieved under mild conditions. O
1 mol% Pt / C HO
OH
O2 (10 bar), 70 oC
OH
HO
HA3, >85%
Scheme 35. Preparation of 3-hydroxy-propionic acid (HA3) from 1,3-propanediol.
4.3 Fatty acid-based hydroxyl acids. 64 ACS Paragon Plus Environment
Page 65 of 247
Renewable hydroxy acids can also be prepared from fatty acids. For example, methyl 10undecenoate224 was reported to be converted into the two different hydroxyl acid esters (HA4 and HA5).225 In the first step the alkene was subjected to a Wacker reaction to selectively form the ketone (Scheme 36). Further conversion of this by reduction and Baeyer-Villiger reaction used stoichiometric reagents in order to obtain the desired products, which were used in the formation of polymers. O O
8
O
O
2.5 mol% PdCl2 O
(CH3)2NAc / H2O O2 (10 bar) 50 oC, 24 h
NaBH4
8
O O HA4
mCPBA
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
O O
8 O
8
O
H2SO4
O
OH
O
OH 8 HA5
Scheme 36. Preparation of long-chain hydroxy acids.
Methyl oleate was subjected to ozonolysis and the product hydrogenated with RaNi as catalyst to obtain 1,9-hydroxynonanoic acid HA5 (Scheme 37a).226 The same compound was also obtained in an interesting disproportionation reaction between the C1,9-diacid and 1,9-nonanediol catalyzed by Co in the presence of hydrogen (scheme 37b).227 In a sequence of 3 enzymatic reactions, oleic acid was first selectively hydrated to obtain 10-hydroxy-stearic acid (Scheme 37c).228 This compound was oxidized using an alcohol dehydrogenase and next subjected to a reaction with a Bayer-Villigerase resulting in 9-nonaoyloxy-nonanoic acid. This was 65 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 66 of 247
hydrolyzed by base to the desired 1,9-hydroxyacid HA5. In later work all enzymes were expressed in a single organism, to allow whole cell conversion directly into the desired product.116 a.
1. O3 7
7
CO2H
b. HO2C
7 CO2H
c.
HO
2. Ra-Ni, H2
+
OH
HO 7
7
Co, H2
CO2H
HO
210 °C HO
Hydratase 7
7 CO2H
HA5
ADH 7
7
7 CO2H
HA5
O
CO2H
7
7
CO2H
BV
HO
NaOH or 7 CO2H
HA5
Esterase
O 7
O
7
CO2H
Scheme 37. Routes to 9-hydroxy-nonanoic acid HA5
Pandey and Chikkali reported the isomerizing hydroformylation of methyl oleate using rhodium ligated with a bisphosphite ligand and obtained the aldehyde as a 75:25 l/b mixture when the CO/H2 pressure was kept as low as 1 bar (Scheme 38a). The product could be hydrolyzed to the acid and reduced at the same time using KOH in refluxing EtOH. Nozaki and co-workers achieved an isomerizing hydroformylation with concomitant hydrogenation of the aldehyde by using three catalysts: a rhodium bisphosphite catalyst, the Shvo catalyst and Ru3(CO)12 (Scheme 38b). They were able to obtain an isolated yield of 53% of the linear hydroxyl ester.
66 ACS Paragon Plus Environment
Page 67 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
a) 7
Rh(CO)2acac Bisphosphite1 H CO2Me 7 CO/H2 1 bar O dioxane, 120 °C
b) 7
7
CO2Me
CO2Me 17
Rh(CO)acac Bisphosphite2 Shvo Catalyst Ru3(CO)12 CO/H2 5 bar dioxane, 120 °C
OP(OR)2
1.KOH/EtOH Reflux 2. HCl
OH
tBu
OP(OR)2 O
Ph
17
53%
Ph
tBu
CO2Me
OH
Bisphosphite1 R= 1-naphthyl
CO2H
17
tBu O O tBu (RO)2P P(OR)2
HA6
Ph
Ru
Ph Ph H
Ph
O
Ph Ru
CO OC 5
OC
Bisphosphite2 R= 1-naphthyl
H
Ph CO
Shvo catalyst
Scheme 38. C1,19-Hydroxyacid and ester from methyl oleate
4.4 Aromatic acids. Vanillic acid (HA7) is one of the most used aromatic hydroxylic acids in polymerization reactions.229-231 It can be obtained from the renewable source vanillin, which itself is obtained from lignin.232 The most efficient method for obtaining vanillic acid is shown in Scheme 39, where an isolated yield of the desired product of 89% was achieved.233
O HO
O
i) 2.5 molt% Pd/C 10 mol% NaBH4 3 eq. KOH air, RT, 24 h ii) HCl
OH O
O
HO HA7 (89%)
Scheme 39. Preparation of vanillic acid (HA7) from vanilin.
5-Hydroxymethyl-furoic acid (HA8) is another important aromatic hydroxy acid used in the production of polymers which can be prepared from 5-hydroxymethylfurfural. The oxidation of HMF to compound HA8 can be performed via enzymatic procedures (using xanthine oxidase, xanthine oxidoreductase or aldehyde dehydrogenase 3) in very high yields.234, 235 Apart from that, heterogeneous transition metal catalysts (gold, silver or platinum) were also able to catalyze this transformation. The best examples of heterogeneously catalyzed processes are 67 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 68 of 247
shown in Table 7. Excellent yields of the desired product were achieved in all cases. However, all procedures require the addition of base.
Table 7. Metal-catalyzed oxidation of HMF to 5-hydroxymethyl furoic acid (HA8). OH O
O
OH
catalyst
O
O
OH
conditions HA8
Entry
Catalyst
Conditions
[Reference] 1.236
% 95 wt% of 1 NaOH (aq., 20 equiv of the 92 wt% Pt / NaY
2.237
Yield of HA8,
base), 80 oC, O2 (5 bar), 12 h
1.5 mol% of NaOH (aq., 4 equiv of the 93 0.5 wt% Au / base), 30 oC, O2 (3 bar), 5 h MgO
3.238
22 wt% of 1.0 NaOH (aq., 4 equiv of the >98% wt% Ag / ZrO2
base), 50 oC, air (50 bar), 1 h
NaY = zeolite consisting of Na2O, Al2O3, SiO2 and H2O.239
5. Lactones Lactones represent an important class of monomers for the formation of polyesters as the resulting polymers are often bio degradable. An overview of lactones which can be derived catalytically from bio-based platforms is given in Figure 6.
68 ACS Paragon Plus Environment
Page 69 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
O O R
O
O O
O
O
O L1
O
O
O
O
O L4
L3
L2
L5
O R L6
Figure 6. Bio-based lactones which have been polymerized to polyesters
5.1 Propiolactone (L1) The smallest member of this family, propiolactone (L1a), can be polymerized to poly(3-hydroxypropionate) (P3HP).240 P3HP is a biodegradable241 and biocompatible polyester and therefore can be used for medical or pharmaceutical applications. Although P3HP can be directly obtained in biotechnological approaches there is still a huge interest in the pure monomer, which can be obtained from the carbonylation of bio-based ethylene oxide (E1), as shown in Scheme 40. In a similar fashion, methyl propiolactone (L1b) is accessible from the carbonylation of renewable propylene oxide.
69 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 70 of 247
CO O R
O A1
R
O R
E1
L1a R=H L1b R=Me
R=Me, H Biobased ethene or propylene
Scheme 40. Propiolactones from olefines
In initial experiments on the carbonylation of epoxides to propiolactones it was found that adducts of bis(triphenylphosphine)iminium with HCoCO4 in conjunction with Lewis acids led to an efficient system for the carbonylation of ethylene oxide (E1) to propiolactone L1 (Figure 7).242 It was later noticed that increasing the steric bulk around the Lewis acid increases selectivity towards the desired propiolactones. Table 8 illustrates the evolution of these systems.243
70 ACS Paragon Plus Environment
Page 71 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
Co(CO)4 O
Ar Ph2P N Ph2P
CO CO Co CO CO
Ar
N
N
M N
Ar
Co-1
O
N Ar
Al-2 M=Al Co(CO)4 O
t
N N M O O
Bu t
Bu
t
O
t
Co(CO)4
Bu
Ti(THF)2
Bu
Ti-1 Al-1 M=Al Cr-1 M=Cr
Figure 7. Precatalysts for the carbonylation of ethylene oxide and propylene oxide
Table 8. Carbonylation of ethylene oxide (E1) to propiolactone L1a
CO
O
O
O Catalyst
R
R
E1 R=H E1a R=Me
Entry
Substrate
Catalyst
L1a R=H L1b R=Me
T [°C]
p(CO)
t[h]
Solvent
[bar]
(S/C)a
Yield
Ref.
[%]
Co-1 + 1
E1
BF3∙Et2O
110
62
(50)
71 ACS Paragon Plus Environment
24
DME
44
242
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 72 of 247
Co-1 + 2
E1a
BF3∙Et2O
80
62
24
DME
77
242
(100)
3
E1
Al-1 (100)
60
59
8
Toluene
77
243
4
E1
Al-2 (200)
60
59
12
THF
99
243
5
E1a
Cr-1 (50)
22
1
6
DME
96
244
6
E1a
Ti-1 (20)
60
62
4
DME
95
245
aS/C
= Substrate/Catalyst
5.2 Gamma-butyrolactone (GBL) Although previously thought not to be homopolymerizable, due to its very low enthalpy of polymerization246, 247, γ-butyrolactone (L2), achieves increasing attention as a (co)-monomer for bio- and thermal degradable plastics248, 249. L2 can be obtained from the green platform chemical succinic acid or its esters, which are usually obtained via fermentation of sugars. The succinic acid can then be directly hydrogenated to L2 and depending on the conditions to tetrahydrofuran (THF) and/or 1,4-butanediol (BDO). Scheme 41 shows the hydrogenation to L2 and the possible side products.
72 ACS Paragon Plus Environment
Page 73 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
O OH
HO
O
H2
O
O
O From fermentation
L2 (GBL)
OH
HO THF
BDO
Scheme 41. Hydrogenation of succinic acid to GBL (L2)
The hydrogenation of succinic acid was demonstrated with heterogeneous and homogenous catalysts. In both cases the amount of literature is extensive and thus, here we focus on the recent developments in the last decade. Table 9 gives an overview over recently published heterogeneous hydrogenation catalysts and their selectivities/conversions in the hydrogenation of succinic acid.
Table 9. Heterogenous catalysts for the reduction of succinic acid to GBL
Entry
Catalyst
T
p(H2)
(°C)
bar
S/Ca Solven
Co
Sel.b(
Sel.b(BD Sel.b(TH Ref.
t
nv.
GBL)
O) [%]
F) [%]
b
[%]
[%] 1
Pt0.01Au-
240
50
521
None
80
>99
n.a.
n.a.
250
TiO2 2
Au/m-ZrO2
180
40
500
Water
100 >99
n.a.
n.a.
251
3
Pd/TiO2
160
150
250
Water
100 95
3
2
252
73 ACS Paragon Plus Environment
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
4
0.02 % Pd/
240
60
γ-AlOOH 5
137
1,4-
5
Dioxan
Page 74 of 247
75
98
n.a.
n.a.
253
e
Pd-
200
50
67
Water
55
84
0
n.a
254
240
150
n.a.
Water
50
85
95% selectivity towards (5-(aminomethyl)furan-2yl)methanol can be achieved. Other routes towards the latter compounds also exist from HMF417-419 or the furan-2,5-diyldimethanol406,
407
as the starting materials. This
aminoalcohol can also serve as the starting material for the preparation of compound
ACS Paragon Plus Environment
107
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 108 of 247
DAM2 (Scheme 62), where 97% isolated yield was achieved.419 Therefore, it constitutes a 2-steps process to obtain diamine DAM2 from HMF.
H 2N
O
OH
0.5 mol% [Ru(CO)ClH(PPh3)3] 0.5 mol% Xantphos NH3 (7 bar) tert-amyl alcohol 140 oC, 14 h
H 2N
O
NH2
DAM2, 97%
O PPh2
PPh2
Xantphos
Scheme 62. Preparation of 2,5-bis(aminomethyl)furan (DAM2) from (5-(aminomethyl)furan-2-
yl)methanol.
The desired product can also be prepared from HMF or fructose in 3 steps. The first oxidation step can be performed via many efficient routes, producing 2,5-diformylfuran in excellent yields.420-423 The dialdehyde compound can then be converted to the nitrile via classical ammoxidation with ammonia and oxygen using a mixed metal heterogeneous catalyst,424 and the nitrile can be reduced to the desired product (Scheme 63 top).425 The yields of each step in this sequence is over 90%. Another synthetic route from 2,5diformylfuran towards product DAM2 can proceed via synthesis of the bis-oxime – i.e. the bottom pathway in Scheme 63.426-428
ACS Paragon Plus Environment
108
Page 109 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
OH O
N
O
O N NH2
O O
O
NH2
O DAM2
NOH NOH
O
Fructose
Scheme 63. Preparation of 2,5-bis(aminomethyl)furan (DAM2) from HMF or fructose in 3 steps.
Although various multi-step synthetic routes from HMF to 2,5-bis(aminomethyl)furan exist, the reaction described in Scheme 61 is still the most convenient method, as it is a highly efficient single step reaction from HMF.
While compound DAM2 can serve as the monomer in the polyamide synthesis itself, (tetrahydrofuran-2,5-diyl)dimethanamine
(DAM3)
can
be
prepared
from
it
via
hydrogenation of the aromatic ring.57 Excellent yields of the heterocyclic diamine were achieved via this route (Scheme 64).
H 2N
2.2 mol% Pd/C
O NH2 DAM2
H2 (35 bar), MeOH 50 oC, 18 h
H 2N
O NH2 DAM3, 97%
ACS Paragon Plus Environment
109
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 110 of 247
Scheme 64. Preparation of (tetrahydrofuran-2,5-diyl)dimethanamine (DAM3) from (furan-2,5diyl)dimethanamine (DAM2).
Alternatively, it can be prepared via a 2 step process from HMF. After the starting material has been oxidized to diformylfuran, it can be converted to the desired compound in 90% yield in the presence of a heterogeneous nickel catalyst (Scheme 65).429
O
1 mol% Ni/Al2O3
O O
H 2N
2 eq. NH2OH.HCl 2 eq. NaOH, H2 (1 bar) MeOH, 100 oC, 6 mins
O NH2 DAM3, 90%
Scheme 65. Preparation of (tetrahydrofuran-2,5-diyl)dimethanamine (DAM3) from 2,5-diformylfurane.
The most important diamine used in the synthesis of polyamides is 1,6hexamethylenediamine (4). Due to its importance, many synthetic routes exist towards this compound. Efficiency of most of the routes is still low up to date,430-435 and in reality only few synthetic strategies produce the desired amine in high yields (of over 80%). One such route was recently reported by Hoffman and co-workers, where 1,6-hexanediol was
ACS Paragon Plus Environment
110
Page 111 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
converted to DAM4 as shown in Scheme 66.436 The selectivity of this reaction is 88%, and an isolated yield of 81% after distillation was achieved.
HO
OH
0.6 mol% Ru cat. NH3 (5 bar) toluene 155 oC, 16 h
NH2
H 2N DAM4, 81%
N (C6H11)2P Ru Cl H
CO P(C6H11)2
Ru cat.
Scheme 66. Preparation of 1,6-hexamethylenediamine (DAM4) from 1,6-hexanediol.
The most reported efficient way to produce renewable 1,6-hexamethylene diamine is via the reduction of adiponitrile. This is in fact the current fossil-based process. Generally, Ra-Ni or Ra-Co type catalysts are used for this hydrogenation. Examples of recent publications on this reaction with yields of 90% or over are shown in Table 15. Ammonia is usually added to prevent formation of secondary amines.
Table 15. Hydrogenation of adiponitrile to 1,4-hexanediamine (DAM4).
ACS Paragon Plus Environment
111
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
N N
Entry
catalyst
H 2N
conditions
DAM4
Page 112 of 247
NH2
Reaction conditions
Yield
of
DAM4, % 1437
4 mol% Co(OAc)2 /.1,10-phenanthroline / Al2O3, pyrolyzed at 800 90 °C aq. 6.5 equiv NH3, H2 (55 bar), iPrOH, 130 oC, 4 h
2438
Catalyst – Ni, Cu, Cr / Na2CO3 calcined, continuous flow, substrate 97 : pseudocumene : NH3 = 1 : 1 : 10.5, H2 gas (100 bar), 80 oC.
3439
poly(dimethylsilane)-Pd / Al2O3, n-PrOH : H2O = 4 : 1, substrate : 97* HCl = 3, H2 gas (0.5 bar), 60 oC.
4440
1.6 mol% RuHCl(H2)(PCy3)2, 3.8 mol% PCy3, n-amylamine, H2 97 gas (8.6 bar), 80 oC, 6 h.
*isolated as a ammonium hydrochloride salt
Adiponitrile can be prepared via several synthetic routes from renewables. It can be prepared from adipic acid (AA, Section 2) by treatment with ammonia at high temperatures.441 For example, GVL can be converted to a mixture of pentenenitriles in
ACS Paragon Plus Environment
112
Page 113 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
very high selectivity by reaction with ammonia in the gas phase over a basic catalyst (Scheme 67).442 Many patented procedures for the efficient catalytic conversion of pentenenitriles to adiponitrile in the presence of HCN exist. 441, 443-449 Most of these use a combination of a homogeneous nickel catalyst with tri-tolyl phosphite or with bulky bisphosphite ligands and a Lewis acid.
O
N O
N
N
Mg-silicate NH3, H2O 450 oC cont. flow
N catalyst HCN
N
90%
Scheme 67. Preparation of adiponitrile from GVL in 2 steps.
Another renewable starting material for the preparation of adiponitrile can be acrylonitrile (AC3, see section 11.3). The second industrial process for the production of adiponitrile is the electrolytic dimerization of acrylonitrile.450 Synthetic procedures also exist, where acrylonitrile is directly converted to adiponitrile.451, 452 One efficient way to perform this reaction is by using CoI2(PPh3)2 as catalyst and Zn/H2O as the reducing agent.451 Alternatively, this can be performed via 2 steps – first the dimerization of acrylonitrile to 1,4-dicyanobutene (with a ruthenium catalyst)453,
454
and further hydrogenation of the
ACS Paragon Plus Environment
113
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 114 of 247
alkene to adiponitrile in the presence of a rhodium or palladium catalyst (Scheme 68).455, 456
N
N N
N N
Scheme 68. Preparation of adiponitrile from acrylonitrile in 1 or 2 steps.
Diaminoisomannide is a renewable C6-diamine which can be prepared via catalytic routes. Catalytic amination of isosorbide (D6) has been reported. The most efficient routes reported by Beller and co-workers (Ru-catalyst 1)457 and Vogt and co-workers (Rucatalyst 2)458 are shown in Scheme 69. In both cases, 96% yield of the desired product was obtained.
ACS Paragon Plus Environment
114
Page 115 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
O H HO
OH
H O
catalyst excess NH3 tert amyl alcohol 170 oC
O H H 2N
NH2
H O DAM5, 96%
Ru-Catalyst 1
Ru-Catalyst 2
N
O PPh2
PiPr2
PPh2
PiPr2
6 mol% ligand
2 mol% ligand
6 mol% [RuH(CO)(PPh3)3]Cl
0.66 mol% [Ru3(CO)12]
Reaction time = 20 h
Reaction time = 21 h
Scheme 69. Catalytic amination of isosorbide (D6) to DAM5.
8.3. Long chain linear diamines.
Long chain linear diamines can be prepared from the corresponding diols, synthesis of which is discussed in section 3. As shown in Table 16, a number of these diamines can be prepared in high yields.416 It is important to note that a large excess of NH3 is required, as otherwise undesired side products (such as secondary or cyclic amines) start to form in significant amounts.
Table 16. Preparation of long chain diamines from diols.
ACS Paragon Plus Environment
115
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
HO
OH n
0.5 mol% Ru cat. 117 eq. NH3, toluene 150 oC, 64 h
H 2N
Page 116 of 247
NH2 n
N (iPr)2P Ru Cl H
CO P(iPr)2
Entry
n
Yield of the product, %
1
14
89
2
18
87
3
19
95
4
23
96
An alternative preparation method for long-chain diamines from renewable di-acids and di-esters was described by Cole-Hamilton and co-workers (Table 17).459 They developed a one-pot 2-steps reaction which avoids the requirement to isolate the diol. In all 3 examples shown in the table good isolated yields were obtained.
Table 17. Preparation of long chain diamines from diols.
ACS Paragon Plus Environment
116
Page 117 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
O R
O
O
O
n
R
a) 2 mol% Ru(acac)3 4 mol% triphos 2 mol% CH3SO3H dioxane / water H2 (10 bar), 220 oC, 20 h b) dioxane / aq. NH3 H2 (10 bar), 220 oC, 20 h
PPh2 Ph2P
PPh2 Triphos
H 2N
NH2
n
Entry
n
R
Yield of the product, %
1
10
H
83
2
10
CH3
79
3
17
CH3
78
9. Amino acids and lactams Only a limited number of amino acids and lactams have been used for polymerization (Figure 12). O
O NH
NH2
O
H N
HN 7
L1
L2
O
N H
NR R
O 7
NH
7
L5
L6
7
7
CO2Me
AA2
1 2
R RN
CO2Me
7
7
CO2Me
AA4
AA3 H 2N
L4
CO2Me 1 2
L3 O
H N
AA1
7
H 2N
N n CO2H
n = 7, 10 AA5
7
7
NH2
CO2Me
AA6
ACS Paragon Plus Environment
117
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 118 of 247
Figure 12. Selected bio-based lactams and amino acids
9.1 Caprolactam (L1) By far the most important compound is caprolactam (L1), the monomer for nylon-6. This compound is currently made from benzene in a multi-step process with a rather high carbon footprint. This raw material is also a prime candidate for a new efficient process based on renewable resources. Lysine is produced on large scale (> 1 million ton/y world-wide) by fermentation. Frost cyclized lysine to 2-amino-caprolactam at elevated temperatures in a range of solvents (Scheme 70). The best result, 96%, was obtained by refluxing at 187 °C in 1,2propanediol.460 Next, the remaining amino group had to be removed by hydrogenolysis. A range of hydrogenation catalysts and conditions was tested for this. Up to 65% yield of caprolactam was obtained using Ra-Ni or Ru/C as catalyst at 70 bar H2 and 200 °C or with sulfided platinum on carbon, using a mixture of hydrogen and H2S for the hydrogenation.461
ACS Paragon Plus Environment
118
Page 119 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
H 2N
150-200 °C H 2N
CO2H
Solvent
H 2N
O
O NH
Catalyst
NH
H2
Scheme 70. Caprolactam from lysine
Quite a few routes have been developed based on levulinic acid (LA). As discussed in the section on diacids, LA can be converted via gamma-valerolactone into a mixture of methyl pentenoates. Isomerizing hydroformylation of methyl 3-pentenoate (M3P) (obtained from the palladium-catalyzed methoxycarbonylation of butadiene) using a rhodium catalysts with a bulky bisphosphite as a ligand was developed in the 1990’s by BASF, DSM and Dupont.462-464 The resulting methyl 5-formyl-valerate (M5FV) which was obtained in 85% yield can be converted into caprolactam via reductive amination and ring-closure.465 One could try this hydroformylation reaction on the mixture of methyl pentenoates to obtain M5FV. However, it is known that the M2P does not hydroformylate very well and is mostly converted into methyl valerate, being a catalyst inhibitor in the process.466 Kalevaru, de Vries and co-workers managed to improve the gas phase ring-
ACS Paragon Plus Environment
119
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 120 of 247
opening of GVL with methanol using ZrO2 to such an extent that a mixture of methyl pentenoates containing 81% of methyl 4-pentenoate was obtained (Scheme 71).467 This in turn allowed the application of a method that was developed 25 years earlier for the selective hydroformylation of only M4P from a mixture of methyl pentenoates.468 Using rhodium and sulfonated triphenylphosphine (TPPTS) as catalyst in a two phase aqueous system, formylvalerate was obtained with 93% selectivity and a l/b ratio of 97:3. The remaining M2P and M3P were subjected to an isomerizing methoxycarbonylation to obtain dimethyl adipate in excellent yield. O O
Biomass
OH
H2
O Levulinic acid
GVL catalyst
H+
O
Ru/C
MeOH
O
M2P +
O
M3P +
O
Rh(CO)2acac TPPTS CO/H2
O O
M4P O
O H
+ M2P and M3P
O
1. Distill 2. Pd(OAc)2/dppx CO, MeOH
O M5FV 1. NH3/H2 Ru/C 2. Ring-closure
O NH
O O
O O
Caprolactam
Dimethyl adipate
Scheme 71. Caprolactam from levulinic acid via selective hydroformylation
ACS Paragon Plus Environment
120
Page 121 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
Three other routes based on GVL exist. It is possible to perform an isomerizing hydrocyanation on the mixture of methyl pentenoates or on the mixture of pentenoic acids that can be obtained from GVL by a reactive distillation from an acidic catalyst. However, M2P reacts rather slowly and since more and more M2P is formed during the reaction, full conversion is hard to attain. Nevertheless, it was possible using Ni((p-TolO)3P)4 as catalyst and C12H25AlCl2 as co-catalyst to hydrocyanate M3P with 89% conversion after 22h and a selectivity of 88% to methyl 5-cyanovalerate (M5CV) (Scheme 72).469 It was clear from this experiment that M2P, which is formed during the reaction by isomerization, although much slower, is also consumed. Thus this chemistry should also work on the mixture of methyl pentenoates. Use of a bulky bisphosphite as ligand to nickel gave a much faster reaction and still very good selectivity to M5CV.470 Allgeier and co-workers also used nickel in combination with a bulky bisphosphite as catalyst and ZnCl2 as cocatalyst in the isomerizing hydrocyanation of 3-pentenoic acid to 5-cyano-valeric acid (5CVA).471 They were able to obtain 5CVA with 92%
ACS Paragon Plus Environment
121
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 122 of 247
OR
M2P +
O
M3P +
OR
O
CO2R
2. Ring-closure
M5CV (R = Me) 5CVA (R = H)
OR
NH
1. Ra-Ni. H2
NC
Lewis acid HCN
O
M4P
Caprolactam
R = H. Me
Phosphite = (p-TolO)3P
Bis-phosphite =
O Ni/phosphite or bis-phosphite
MeO
tBu O O P O
OMe
O
O O P O
tBu P O
O
O P O O
R R = H, Me
R R
R
Lewis acid = C12H25AlCl2, Ph3SnOTf, ZnCl2
Scheme 72. Caprolactam from levulinic acid via isomerizing hydrocyanation.
selectivity at 85% conversion. Both M5CV and 5CVA can be hydrogenated to the aminoacid/ester which ring-closes to caprolactam in excellent yield. Interestingly, it is also possible to perform the gas phase ring-opening of GVL in the presence of ammonia and this leads to the formation of a mixture of isomeric pentenenitriles.472 Manzer used either Magnesol (magnesium-silicate) at 450 °C (100% conversion and 89% selectivity to pentenenitriles) or Rb/SiO2 at 400 °C (51% conversion and 82% selectivity to pentenenitriles) as catalysts in a gas phase process (Scheme 73). The products can be subjected to an isomerizing methoxycarbonylation or
ACS Paragon Plus Environment
122
Page 123 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
hydroxycarbonylation reaction to again form M5CV or 5CVA. Researchers from Dupont reported the use of the Lucite ligand in combination with Pd(OAc)2 and MeSO3H for the methoxycarbonylation of 3-pentenenitrile and obtained M5CV with a selectivity of 96% at 98% conversion. The TOF at full conversion was 314 h-1. Beller and co-workers developed a novel ligand based on the Lucite ligand using ferrocene instead of o-xylene as the bridge, and with two of the four tert-butyl groups replaced by 2-pyridyl groups. Use of this ligand in the palladium catalyzed methoxycarbonylation of 3-pentenenitrile gave the product with a l/b ratio of 80:20.473 Researchers from ICES-A-Star reported the use of a new ligand BPX in the palladium-catalyzed hydroxycarbonylation of 3-pentenenitrile and achieved a selectivity of 98% to 5CVA, however, at only 9% conversion.474 O
CN O
O
NH3, catalyst
2PN
gas phase 400-450 °C
3PN
Pd(OAc)2 / Ligand
CN
CO, MeSO3H ROH (R = H, Me)
CN
CN
RO2C
NH
5CVA or M5CV
4PN
O N
Ligand =
PtBu2 PtBu2 Lucite ligand
P Fe P Beller
tBu
P
tBu
P
N
BPX O
ACS Paragon Plus Environment
123
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 124 of 247
Scheme 73. Caprolactam from levulinic acid via isomerizing carbonylation of pentenenitriles
Bouwman and co-workers converted the mixture of methyl pentenoates into the amides by reaction with aqueous ammonia. Rhodium-catalyzed hydroformylation of 4pentenamide (4PAM) using Xantphos as ligand resulted in the formation of the dehydrocaprolactam, which was hydrogenated to caprolactam in 87% yield simply by exchanging the CO/H2 mixture for H2 (Scheme 74). Hydroformylation/hydrogenation of a 3:1 mixture of 3PAM and 4PAM, which approaches more closely the mixture of pentenoates as it was obtained from the ring-opening of GVL, gave caprolactam in only 41%.
Rh(COD)Cl2 Xantphos
O NH2 4-pentenamide (4PAM)
CO/H2 (1:2) 50 bar, then H2 80 bar Diglyme,
O
O H
NH2
O N
H2
NH
O 5-formylvaleramide
Caprolactam
Scheme 74. Caprolactam from levulinic acid via hydroformylation of pentenamide
ACS Paragon Plus Environment
124
Page 125 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
It is also possible to produce caprolactam based on HMF.196 Heeres, de Vries and co-workers converted HMF into caprolactone in a high-yielding three-step sequence (see sub-chapter on diols and lactones). As an industrial process has been operated in the past in which caprolactone was converted into caprolactam by reaction with ammonia in excellent yield, this constitutes a route towards caprolactam.475
9.3 Substituted caprolactams (L2-4) Three terpene-based analogues of caprolactam have been reported. Oxidation of pinene to the ketone and reaction with hydroxylamine gave the oxime, which was subjected to a Beckmann rearrangement catalyzed by polyphosphoric acid to give a single bicyclic lactam that could be polymerized (Scheme 75a).476 Menthone could also be reacted with hydroxylamine and when the resulting oximes were subjected to Beckmann rearrangement in polyphosphoric acid a mixture of two lactams was obtained that could be separated by column chromatography (Scheme 75b).477 N
O a.
H2NOH
KMnO4
b.
poly-phosphoric acid
H2NOH O
OH
N
OH
H N
poly-phosphoric acid
NH
O
+ NH
O
O
Scheme 75. Terpene-based lactams
ACS Paragon Plus Environment
125
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 126 of 247
9.3 Fatty acid-based amino acids (AA1-6) Unsaturated fatty acids have been used extensively as raw material for amino acids that can be polymerized to polyamides. Dubois converted oleic acid into the diacid by whole cell oxidation. The diacid was subjected to ozonolysis with a reductive work-up to obtain 9-oxo-nonanoci acid. Reductive amination of this catalyzed by Ra-Ni gave 9amino-nonanoic acid in 76% yield (Scheme 76).478 In a later publication Pd/C was used for the reductive amination of the methyl ester and the amino acid ester was obtained in 74% yield.479 Enzymatic Oxidation 7
7
CO2H
or selfmetathesis
1. O3 HO2C
7
7
CO2H
2. Red.
H
7 CO2H
O
Ra-Ni or Pd/C NH3/H2
H 2N
7 CO2H
Scheme 76. Long-chain amino acid from oleic acid
Fischmeister, Bruneau and co-workers screened a number of catalysts for the crossmetathesis between methyl undecenoate and acrylonitrile. Best results were obtained with the Hoveyda catalyst (Scheme 77). By slowly dosing the catalyst over time the catalyst loading could be reduced to 0.005 mol% allowing 96% conversion with near
ACS Paragon Plus Environment
126
Page 127 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
perfect selectivity to the cross-coupled product within 15h (Scheme 77a, R1 = Me, R2 = H).111 In addition, they performed the cross metathesis of acrylonitrile with dimethyl octadec-9-enedioate, which can be obtained either by self-metathesis of methyl oleate of by selective enzymatic terminal oxidation of methyl oleate (Scheme 77b, R1 = Me, R2 = H). Here 5 mol% of the Hoveyda catalyst was needed for full conversion. However, slow addition of the catalyst allowed to bring back this amount to 0.05 mol% although the yield of the nitrile ester was somewhat reduced from 95 to 88%. In an earlier publication they had shown these metathesis reactions could also be performed on the acid and diacids using 5 mol% of the Hoveyda catalyst (Scheme 77a,b, R1 = H, R2 = H).480 Also, the cross-metathesis between fumaronitrile and methyl oleate as well as with the unsaturated C18-diester was possible with 5 mol% of the Hoveyda catalyst (Scheme 77a, b, R1 = Me, R2 = CN).480 Nevertheless, reactions with acrylonitrile are inherently slow. Ruthenium catalysts based on cyclic alkyl amino carbenes were able to achieve higher turnover numbers up to 28 500 in the metathesis between methyl oleate and acrylonitrile.481 The problem can also be circumvented by another synthetic strategy: Undecenoic acid obtainable from ricinoleic acid can be converted into the
ACS Paragon Plus Environment
127
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 128 of 247
nitrile by reaction with ammonia in the presence of a tungsten oxide on titania catalyst or Nb2O5.482 The Rennes group in collaboration with Arkema showed that it is possible to perform the cross-metathesis of this nitrile with methyl acrylate (Scheme 77c). And indeed, using the Hoveyda catalyst it was possible to lower the catalyst loading to 0.025 mol% and still achieve 98% conversion and 98% selectivity to the desired product.483 Cross metathesis of methyl oleate with allyl cyanide and homoallylcyanide has also been reported.484 It was also possible to perform cross-metathesis with acrylonitrile on the methyl ester of ricinoleic acid (Scheme 77d).111 There is no need for an additional catalyst for the hydrogenation of the double bond and the nitrile group as the remnants of the metathesis catalyst can function as catalyst. However, for full conversion of the unsaturated nitrile to the amino acid ester 3 mol% of metathesis catalyst and 30 mol% of KOtBu were necessary. Thus, application of 20 bar hydrogen pressure at 80 °C allowed full conversion and the amino acid ester was isolated in 90% yield.483
ACS Paragon Plus Environment
128
Page 129 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
R2
CO2R1 +
a.
8
R1 = H, Me
R O 2C
7
7
CO2R
1
R
+
R1 = H, Me
7
H2
CO2R1
NC
H 2N
8
CO2Me 11
CO2Me
Hoveyda catalyst
2
CN
H2
CO2R1
NC
gas phase 300 °C
7
7
CO2Me
H2 CN
MeO2C
Hoveyda catalyst
Cat. NH3
H 2N
11
8
R2 = H, CN
c. 7
CN
R2 = H, CN
b. 1
Hoveyda catalyst
7
+
CN
CO2Me
CO2Me 7
d.
HO 7 5
CO2Me
+
CN
Hoveyda catalyst
OH NC
CO2Me 7
5
CN
Scheme 77. Amino acids based on fatty acids via metathesis reactions
Meier and co-worker subjected methyl oleate to a Wacker reaction thus obtaining a mixture of methyl 9- and 10-oxo- stearates (Scheme 78a). These were subjected to reductive amination with a mixture of ammonium acetate and ammonium chloride using Ra-Ni as catalyst and 30 bar of hydrogen at room temperature to obtain the mixture of amino acids.485, 486 In addition, they performed the reductive amination of these ketones with a series of diamines to produce the corresponding bis-amino acids. It is also possible to isomerize methyl ricinoleate using palladium with the Lucite ligand as catalyst to obtain methyl 12-oxo-stearate (Scheme 78b).487
ACS Paragon Plus Environment
129
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 130 of 247
Hydroformylation of oleic acid (Rh/PPh3) followed by reductive amination gives a 50/50 mixture of 9- and 10-aminomethyl-stearic acid, which was polymerized (Scheme 78c).488 The hydroaminomethylation reaction has been used extensively on fats and fatty acid derivatives.489 Behr and co-workers subjected ethyl oleate to the hydroaminomethylation reaction using a range of primary and secondary amines (T = 140 °C, 1.5-fold excess of the amine compound, 100 bar CO/H2 1:1, toluene, 0.5 mol-% [Rh(cod)Cl]2); ammonia was
not
used
(Scheme
78d).490
Vorholt
and
co-workers
performed
the
hydroaminomethylation reaction on methyl oleate with 3-methylamino-propionitrile (Scheme 78e). The catalyst could be recycled through the use of a thermomorphic solvent system (acetonitrile/heptane).The resulting nitrile ester was hydrogenated using Ra-Ni as catalyst to obtain an amino acid, which polymerized during the hydrogenation. 491
ACS Paragon Plus Environment
130
Page 131 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
O
a. 7
7
CO2Me
PdCl2 10 bar O2
7
O
DMA/H2O 70 °C
7
b.
HO 7
CO2Me
c. 7
7
CO2Me
7
CO2Me
NH3/H2
7
CO2Me
7
7
CO2Me
7
7
7
CO2Me
AA1
AA2
10
1. Rh/PPh3 CO/H2 (1:1) 140 bar, 110 °C
NH2
2. NH3/H2 Ra-Ni
7
7
CO2Me
H 2N + 7
AA3
7
7
7
CO2Me
1 2
R RN +
CO2Me
7
7
CO2Me
AA4 N
7
7
AA4 NR1R2
CO/H2 (1:1) 100 bar, 140 °C
CO/H2 (1:1) 50 bar, 120 °C
CO2Me
CO2Me 5
MeHNCH2CH2CN [Rh(COD)Cl]2 CO2Me
+
7
O
AA3
e.
7
7
R1R2NH (1.5 eq.) [Rh(COD)Cl]2 d.
H 2N
Ra-Ni
Pd(OAc)2 Lucite ligand CH3SO3H MeOH, 100 °C
5
+
NH2
CN
N
Ra-Ni
CO2Me
H2
+ regioisomer
7
7
NH2
CO2Me AA5
Polymers
Scheme 78. Amino acids and esters from fatty acids
9.4 Fatty acid-based lactams (L3-4)
It is also possible to make lactams from fatty acids. Yamamoto and co-workers reacted oleic acid as well as 9-decenoic acid with amino alkenes of different chain length. The resulting amides were subjected to a metathesis reaction with the Hoveyda catalyst and the resulting unsaturated lactam was hydrogenated (Scheme 79).492 Interestingly,
ACS Paragon Plus Environment
131
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 132 of 247
whereas the amides based on 1-but-3-enylamine could be ring-closed in good yields, albeit in high dilution, this was not the case for the amides based on allylamine. Here an extra benzyl substituent on the nitrogen atom was necessary to allow ring-closure in moderate yields. Hoveyda Catalyst
O N R
7
n
7
O
NH
N
or
Hoveyda Catalyst
H N 7
O
Ph
n
O
n = 1, R = CH2Ph n = 2, R = H
O
Pd(OH)2 27bar H2 HCl/MeOH
Pd/C 1 bar H2 MeOH O
NH
NH
Scheme 79. Large-ring lactams from fatty acids via metathesis
10.
Alkenes
n
A1
A2a, n= 0 A2b, n= 1 A2c, n= 14
A3
A4
A5
A6
Figure 13. Bio-based alkene monomers.
ACS Paragon Plus Environment
132
Page 133 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
The production of olefins from biomass is an intensively investigated research field and is discussed in great detailed in several excellent reviews.336, 357, 493-497 Thus, the access of light olefins from biomass will only be discussed briefly. Ethylene (A1), propylene (A2a) and styrene (A4) are the most important industrially used monomers and feedstocks which are commonly obtained from fossil resources (Figure 13).336, 494
10.1 Ethylene (A1) Today approximately 0.3% of the global capacity of ethylene (A1) is derived from bioethanol by catalytic dehydration (scheme 80). A large variety of catalysts such as phosphoric acid, oxides, molecular sieves and heteropoly acid catalysts are used for this reaction while heterogeneous catalysts based on metal oxides or molecular sieves are of industrial relevance.336, 498, 499 Higher α-olefins are in general accessible via dimerization or oligomerization of ethylene.495, 500, 501
ACS Paragon Plus Environment
133
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
OH
Page 134 of 247
Catalytic dehydration - H 2O
Bio-based ethanol
A1
Scheme 80. Catalytic dehydration of ethanol to obtain ethylene (A1).
10.2 Propylene (A2a) In 2010, Braskem announced a project for green propylene (A2a) production based on bioethanol from sugarcane in 2010.502 Machado and co-workers evaluated the production of bio-based propylene (A2a) on the base of sugarcane bio-refinery in Brazil.503 Three pathways are generally discussed for producing propylene (A2a) from ethylene (A1) namely the direct conversion of ethylene by dimerization and metathesis, the metathesis of ethylene and 2-butylene separately and the oligomerization and catalytic cracking afterwards (Scheme 81). These processes were recently summarized by Hulea.500 Promoters for the two first reactions are transition-metal catalysts and for the latter zeolites and silicoaluminophosphates (SAPO) are favored. The dimerization is catalyzed by homogeneous catalysts based on Ni, Ti, Zr, Cr, Co or Fe. The major industrial process (Alpha-Butol process, Axens, Sabic)) for 1-butene from ethylene is based on the use of
ACS Paragon Plus Environment
134
Page 135 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
(Ti(OtBu)4 / AlEt3 as catalyst. The conversion of a mixture of 1-butene and ethylene to propene is the so-called Olefin Conversion Technology (OCT), in which a mixture of an isomerization catalyst (MgO) is used for the isomerization of 1-butene to 2-butene and WO3/SiO2 is used as the metathesis catalyst in a gas phase process at >260 °C and 30− 35 bar. Direct dimerization, isomerization & metathesis
Dimerization Isomerization
Metathesis A2a
A1 Bio-based A1
Oligomerization
Catalytic cracking n
Scheme 81. Synthesis routes of propylene (A2a) from ethylene (A1).
The conversion of glycerol to olefins (GTO) is another possibility to obtain ethylene (A1), propylene (A2a) and other olefins.504 Examples for the conversion of glycerol to A2a with yields higher than 75% are shown in Table 18.
Table 18. Selected examples of the conversion of glycerol to propylene (A2a).
ACS Paragon Plus Environment
135
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
OH HO
OH
H2
Catalytic hydrogenolysis
Page 136 of 247
OH
Catalytic dehydration - H 2O
and/or OH
A2a
entry catalyst
1a 2 3 4 5 6 7 a
yield/
conditions
%a
p(H2)= 6.9 MPa, 210
HI (14 mol%)
°C, 5 h
WO3-Cu/Al2O3
p(H2)= 1.0 atm., 242 °C 85b
SiO2-Al2O3 Ir/ZrO2 (0.12 mol%)
p(H2)= 1.0 MPa, 250
HZSM-5-30
°C, 2 h
MoO3-Ni2P/Al2O3
250 °C, 2 h,
ZSM-5-30
Flow
p(H2)= 1.0 atm., 300
Fe-Mo/C
°C,
316 Stainless Steel HOTf (8
78
p(H2)= 5.5 MPa, 250
mol%)c
°C, 24 h
[Ru(H2O)3(4´-phenyl-
p(H2)= 5.5 MPa, 250
terpyridine)](OTf)2 (0.5 mol%)c
°C, 24 h
ref.
505
506
85
507
88
508
90
509
96
510
100
510
In some cases the yield was calculated from the selectivity and conversion given in
the respective reference.
bAverage
value in 2–5 h.
bHOTf:
triflic acid.
cRu-cat:
[Ru(H2O)3(4´-phenyl-terpyridine)](OTf)2; sulfolane was used as solvent.
Deshpande and co-workers achieved full conversion and a selectivity of 78% towards A2a in the presence of simple HI (14 mol%) in aqueous solution (table 18, entry 1).505
ACS Paragon Plus Environment
136
Page 137 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
Sun et al. studied the conversion of glycerol to propylene under flow conditions whereby a WO3-Cu/Al2O3 catalyst was used in the upper bed of the reactor. A commercial silicaalumina catalyst in the lower bed promoted the reaction of 1-propanol to propylene (A2a) which was obtained in 85% yield (entry 2).506 To achieve optimal yields on A2a Yu and co-workers initially focused on the selective hydrogenation of glycerol to 1-propanol. In the presence of Ir/ZrO2 as the catalyst they realized full conversion in the hydrogenation step and selectivities above 90% with different glycerol concentrations. In combination with HZSM-5-30 as a dehydration catalyst they demonstrated the direct conversion of glycerol to propylene (A2a) with an overall yield of 85% (entry 3).507 A slightly higher yield of 88% was obtained when the same dehydration catalyst was applied with a MoO3 modified Ni2P/Al2O3 as hydrogenation catalyst (entry 4).508 Gambetta and co-workers developed a supported Fe/Mo catalyst giving A2a in up to 90% yield (entry 5).509 Di Mondo et al. reported the formation of propylene (A2a) in 96% yield in a stainless steel 316 (316SS) autoclave in the presence of 8 mol% trifluoromethanesulfonic acid (entry 6).510 Detailed investigations revealed the generation of a catalytically active metal surface
ACS Paragon Plus Environment
137
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 138 of 247
when 316SS was treated with the Brønstedt acid. Notably, the use of a homogeneous Ru-catalyst led to full conversion of glycerol to A2a (entry 7).510
10.3 Butenes (A2b, A3) Bio-based n-butanol can be obtained for example by the ABE process trough fermentation of carbohydrate rich biomass.511, 512 This process produces in addition to nbutanol two other important bulk chemicals, namely acetone and ethanol in an overall ratio of 6 to 3 to 1. The selectivity to 1-butene (A2b) in the dehydration of n-butanol is strongly dependent on the reaction conditions. At higher reaction temperatures and lower 1-butanol pressures the 1-butene (A2b) yield can be increased if a ZSM-5 catalyst is used.513 Zeolite catalysts showed most promising results for the dehydration of butanols (Scheme 82). AS reported by Chadwick and co-workers in 2010, n-butanol can be converted in one step to isobutylene (A3) via dehydration and skeletal isomerization over zeolite catalysts at higher temperatures.514,
515
Mechanistic insights for this important (co)-monomer in
polyolefin chemistry were given by Marin et al. in 2017.516, 517
ACS Paragon Plus Environment
138
Page 139 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
OH
Skeletal isomerization T> 573°C
Zeolite catalyst - H 2O A2b
n-butanol
Fermentation
Inorganic acid catalyst - H 2O
i-butanol
A3
Sugars
HO
Fermentation
Scheme 82. Syntheses of 1-butylene (A2b) and isobutylene (A3) from butanols.
Isobutylene (A3) is also accessibly by dehydration of isobutanol, obtained via fermentation,
518
with acid catalysts519-521 (Scheme 82). Bio-based isobutene (A3) is
industrially produced by Global Bioenergies (fermentative from sugars), Butamax (Joint Venture of BP and DuPont) and Gevo (both from isobutanol).522 The latter is cooperating with Lanxess for the European market whereby Lanxess plans the application of the isobutylene (A3) for a bio-based butyl rubber in the manufacturing of tyres.523,
524
Isobutylene is currently used for the production of rubbers, in particular halogenated rubbers.525 In addition, it is converted into methyl methacrylate, the monomer for Perspex.526
10.4 Styrene
ACS Paragon Plus Environment
139
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
O OH
Page 140 of 247
0.03 mol% Ru3(CO)12 200 °C, 4 h - CO2
Cinnamic acid
Classical process
Classical process A1 Benzene Bio-based
A4
Ethylbenzene
O OH
Hydrocinnamic acid
0.25 mol% PdCl2 4.4 mol% DPEphos 1 eq Piv2O 190 °C, 2 h - CO
Scheme 83. Syntheses for styrene (A4) from biomass.
Styrene (A4) is usually obtained by dehydrogenation of ethylbenzene. Approximately 85% of the worldwide produced ethylbenzene is dehydrogenated to styrene (A4) catalyzed by metal oxides.527 Thus the key to renewable A2 using conventional methods is a sustainable access to ethyl benzene e.g. from bio-based ethylene (A1) and benzene (Scheme 83). As mentioned above A1 is accessible from renewables while benzene and other aromatics are difficult to obtain from biomass. Catalytic pyrolysis of lignin is one possibility to obtain C6–C8 aromatics (benzene, toluene and xylenes – BTX).528 The yields for the aromatics are low thus the toluene and xylenes can be converted by dealkylation or disproportionation to benzene.529 Styrene (A4) can also directly be prepared e.g. by
ACS Paragon Plus Environment
140
Page 141 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
decarboxylation of cinnamic acid. Doll and co-workers reported the use Ru3(CO)12 (10 mol%) as a suitable catalyst at temperature 200°C achieving a styrene (A4) yield of 74%.530 Using hydrocinnamic acid derived from biomass Tolman and co-workers developed
a
dehydroxycarbonylation
protocol
with
PdCl2
and
bis[(2-
diphenylphosphino)phenyl] ether (DPEphos) to produce styrene (A4) in up to 87% yield.531 The direct synthesis of A4 by fermentation of glucose has been reported by Nielsen and co-workers.532
10.5 Limonene (A5) and Camphene (A6)
or
H
A5
A6
Scheme 84. Isomerization of pinene to limonene (A5) and camphene (A6).
Limonene (A5) is traditional used in the flavor and fragrance industry. The application of A5 is rapidly expanding and this includes its utilization as a monomer.533, 534 It can be
ACS Paragon Plus Environment
141
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 142 of 247
isolated directly by extraction from orange peel which is a waste product of the orange juice industry.535 Moreover, it can be produced biotechnologically from cheap sugars536 or glycerol537 using yeasts or Escherichia coli. Bowie and co-workers presented an enzymatic procedure starting from cheap and abundant sugars which could be feasible on industrial scale.538 Usually extracted from turpentine, α-pinene can be isomerized to limonene (A4) or camphene (A6) by acid catalysts (Scheme 84).539 Through suitable catalyst systems varying the strength, nature, and number of acid sites camphene (A6) or limonene (A4) are favored in liquid-phase systems.357 The use of solid acid catalysts in this reaction has been reviewed.364 An immobilized AlCl3 catalyst gave at a reaction temperature of 45°C a mixture consisting of 53% of limonene and 41% of camphene (A6).540 Lewis acidic sites favored the formation of camphene (A6) and other bicyclic terpenes from β-pinene, whereas Brönsted acidic sites led to the formation of monocyclic terpenes like limonene (A4).
541
β-Pinene can obtained by extraction from pines or kaffir lime peals in up to
30%.542 If β-pinene is used as substrate high yields of limonene (A4) up to 76% were obtained with a hierarchically acidic MCM-22 catalyst.543 Via the isomerization of this
ACS Paragon Plus Environment
142
Page 143 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
feedstock camphene (A6) can also be obtained from reactions with solid acid catalysts. 357, 364, 539
The common industrially used catalyst is sulfated titanium oxide (H2SO4/TiO2)
which has several disadvantages like leaching of sulfate groups and low selectivity to camphene (A6).544,
545
A high camphene (A6) yield of 66% was obtained under
continuous-flow conditions using a Au/γ-Al2O3 catalyst by Simakova and co-workers.546 If operating at high α-pinene concentrations coke formation and resulting catalyst deactivation was observed. Akgül et al. obtained a slightly lower camphene (A6) yield of 61% with an Fe3+-doped clinoptilotite in 2013.547
10.6 Long-chain alpha-olefins Several methods for the synthesis of long chain α-olefins from fatty acids have been reported including the direct cracking metathesis,548, 549 biosynthesis550, 551 as well as the heterogeneous and homogenous catalyzed deoxygenation of fatty acids.552-554 In 1976, Foglia and Barr reported the first catalytic decarbonylative dehydration of fatty acids e.g. stearic acid utilizing RhCl3 or PdCl2 in combination with Ph3P (table 19, entry 1).555 The reaction proceeds via the in situ formation of the corresponding acid anhydride and
ACS Paragon Plus Environment
143
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 144 of 247
subsequent decarbonylation. The first reaction step can be facilitated by the addition of acid anhydrides e.g. Ac2O as additives which lead to the formation of mixed anhydrides.556-558 Gooßen and co-workers reported a Pd-catalyst based on DPE-Phos which allows the performance of this reaction under considerably milder reaction conditions (entry 2).559 More recently, Chatterjee and Jensen reported a Pd/C based system also utilizing DPE-Phos as ligand (entry 3).560 The benefits of using bidentate phosphine ligands in combination with a heterogeneous palladium catalyst was studied by Ortuño and López using DFT-calculations.561 The bidentate phosphines create crowded cavities on the surface allowing a fast product release and thus preventing undesired side reactions whereas monodentate ligands block the metal surfaces leading to lower catalytic activity. Ryu et al. used Vaska’s Complex for the decarbonylative dehydration to obtain internal and terminal alkenes selectively. Operating at high temperatures of 250 °C in combination with KI as additive they converted stearic acid to the corresponding internal heptadecenes with an excellent overall yield of 91%. At lower reaction temperature the isomerization was hindered and heptadec-1-ene (A2c) was obtained in 80% yield and α-selectivity of 95% (entry 4).562 Hapiot and co-workers reported
ACS Paragon Plus Environment
144
Page 145 of 247 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
a similar protocol for the decarbonylative dehydrogenation utilizing [Ir(COD)Cl]2 as the catalyst.563 Notably, catalysts based on readily available and inexpensive metals like Fe564 or Ni565 also showed potential for the decarbonylative dehydration (entries 5 and 6). Further development with these systems is needed because low α-selectivities were achieved with the nickel catalysts and large amounts of additives were used.
Table 19. Stearic acid as chosen example for decarbonylative dehydration of fatty acids.
COOH 14
catalyst. (+additive) co-catalyst T, t, p
A2c
Stearic acid
entr
cat./
y
co-cat.
1
RhCl3
mol%)
PPh3 (10 mol%) PdCl2
2
(1
(3
DPE-Phosc
3
DPE-Phosc
additives
conditions
yield/ %
ref.
–
250°C, 5.5 h,
>99 (80)a
555
97
558
70
560
mol%) Ac2Ob (2 equiv) (9 NEt3 (1 equiv) 110 °C, 18 h
mol%) Pd/C
14
DMPUd (1mol%) (10 Ac2Ob (1 equiv) 250 °C, 0.25 h
mol%)
ACS Paragon Plus Environment
145
ACS Catalysis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
IrCl(CO)(PPh3)2
4
(5 Ac2Ob (2 equiv) KI (0.5 equiv)
mol%) FeCl2
5
(10
mol%)
DPPPente
(20
mol%)
Ac2Ob (1 equiv) KI (1 equiv) PPh3
NiI2
6
(2.8
Page 146 of 247
160 °C, 5 h
80
562
2.0 84
564
250 °C, 3 h,
p(CO)= MPa
(0.14
mol%) equiv)
Cu(OTf)2 (2.8 mol%) TMDSf
(0.8
190 °C, 16 h
66g
565
equiv) a
PdCl2
(1mol%),
2h.
bAc
2O:
Acetic
anhydride.
cDPE-Phos:
Bis[(2-
diphenylphosphino)phenyl] ether; dDMPU 1,3-dimethyl-tetrahydro-2(1H)-pyrimidinone. eDPPPent=
1,5-bis(diphenylphosphino)pentane.
fTMDS=
1,1,3,3-
tetramethyldisiloxane. gα-selectivity=
