Multi-Functional Cascade Catalysis of Itaconic Acid

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Multi-Functional Cascade Catalysis of Itaconic Acid Hydrodeoxygenation to 3-Methyl-Tetrahydrofuran Dae Sung Park, Omar A. Abdelrahman, Katherine P Vinter, Patrick Howe, Jesse Q. Bond, Theresa M. Reineke, Kechun Zhang, and Paul J. Dauenhauer ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.8b01743 • Publication Date (Web): 04 Jun 2018 Downloaded from http://pubs.acs.org on June 4, 2018

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ACS Sustainable Chemistry & Engineering

Multi-Functional Cascade Catalysis of Itaconic Acid Hydrodeoxygenation to 3-Methyl-Tetrahydrofuran Dae Sung Park1,2, Omar A. Abdelrahman1, Katherine P. Vinter1, Patrick M. Howe , Jesse Q. Bond3, Theresa M. Reineke1,2, Kechun Zhang1,2, Paul J. Dauenhauer1,2* 3

1

University of Minnesota, Department of Chemical Engineering and Materials Science, 421 Washington Ave. SE, Minneapolis, MN 55455. 2 Center for Sustainable Polymers, Department of Chemistry, University of Minnesota, Smith Hall, 207 Pleasant St. SE, Minneapolis, MN 55455. 3 Syracuse University, Department of Biomedical and Chemical Engineering, 223 Link Hall, Syracuse, NY 13244. *Corresponding Author: [email protected]

Keywords:

Itaconic acid, Isoprene, Tetrahydrofuran, Hydrogenation, Bimetallic, Biomass

Abstract.

Hybrid production of isoprene from biomass-derived sugar as a feedstock for renewable rubber is a three-part process comprising glucose fermentation to itaconic acid, liquid-phase hydrodeoxygenation to 3-methyl-tetrahydrofuran followed by vapor-phase dehydra-decyclization to isoprene. Here we investigate multifunctional catalyst design for itaconic acid hydrodeoxygenation to 3-methyl-tetrahydrofuran. The production of 3-methyl-tetrahydrofuran from itaconic acid is a multistep process involving hydrogenation, acid-catalyzed dehydration, and hydrodeoxygenation of multiple organic functionalities. A detailed kinetic analysis of this multi-step reaction network over a Pd/C catalyst revealed a kinetic bottleneck in the reduction of methyl-γ-butyrolactone to 1,4-methyl butanediol, which was accelerated through the use of Re as an oxophillic promoter. Varying ratios of Pd:Re indicated a maximum overall rate of lactone ring opening with a 3.5:1.0 Pd:Re ratio, likely due to the combined capability of Pd to hydrogenate double bonds and Re to open the lactone ring. Applying this insight, the overall rate of itaconic acid hydrodeoxygenation to 3-methyltetrahydrofuran increased by more than an order of magnitude.

Park, et al.

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Introduction.

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Biomass-derived carboxylic acids are attractive platforms for their versatility in the

production of fuels and chemicals 1,2. Renewable carboxylic acids (C1~C5) are commonly produced by the fermentation of carbohydrates, and some bio-based acids (succinic acid, lactic acid, itaconic acid) already exist as commercial biological processes1. Itaconic acid, a C5-unsaturated dicarboxylic acid, and the related mesaconic acid are such platform chemicals which have a wide range of applications in the production of synthetic fibers, coatings, adhesives, binders, and a replacement for petroleum-based acrylic and methacrylic acids 3,4,5. One other important derivative from itaconic acid is 3-methyl-tetrahydrofuran (3-MTHF)6,7, which has attracted attention as a promising fuel component and green solvent. We recently demonstrated a new chemical pathway for the production of isoprene via the dehydra-decyclization of 3-MTHF, resulting in 70% selectivity to isoprene (90% selectivity to isoprene + pentadiene) at a conversion of 25%8. This enables the production of isoprene, a precursor for car tires and other polymers, from renewable carbon resources such as lignocellulosic biomass. The conversion of itaconic acid to 3-MTHF involves a series of aqueous-phase hydrogenation, hydrodeoxygenation and dehydration reactions9,10 as depicted in Scheme 1. The C=C double bond in itaconic acid is first reduced to methylsuccinic acid (MSA). MSA is then transformed to the intermediate, methyl-4-hydroxybutyric acid, by hydrodeoxygenation of the C=O bond in carboxylic acid, after which methy-4-hydroxybutyric acid is converted to α-methyl-ɤ-butyrolactone (MGBL) via an intra-molecular esterification. Further hydrogenation of MGBL leads to the formation methyl-1,4butanediol (MBDO), which is subsequently dehydrated to 3-MTHF8, 11 , 12 . These sequential hydrogenation and dehydration reactions require a combination of multiple catalytic functions (hydrogenation, ring-opening, and dehydration) to enable the one-pot conversion of itaconic acid to 3MTHF.

Park, et al.


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Y: 80 % [8] Pd-Re/C 3-Methyltetrahydrofuran (3-MTHF)

Itaconic acid (IA)

Metal

H2

H+

2-methyl-1,4-butanediol (MBDO)

Methylsuccinic acid (MSA)

Metal

-H2O

2H2 -H2O

H2

Metal

-H2O H+ Methyl-4-hydroxybutyric acid (MHBA)

Methyl-γ-butyrolactone (MGBL)

Scheme 1. Cascade hydrodeoxygenation of itaconic acid (IA) to 3-methyltetrahydrofuran (3-MTHF) by combined metal-metal-acid catalysis.

Few studies exist on the production of 3-MTHF from itaconic acid, where the focus has been more on converting itaconic acid to MGBL and/or MBDO. Geilen et al.11 examined the hydrogenation of itaconic acid by Ru-complexes with phosphine ligand and hydrogen gas (10 MPa) at 195 °C. The use of the bidentate ligand 1,4-diphenylphosphinobutane (dppb) resulted in 93% yield of MGBL using THF solvent, while a Ru/triphos catalyst led to a 93% yield in MBDO with dioxane as a solvent. The use

of

additives

(p-TsOH

and

NH4PF6)

in

Ru-complexes

with

1.1.1-

tris(diphenylphosphinomethyl)ethane ‘triphos’ ligand resulted in 97% yield of 3-MTHF. The hydrogenation of IA catalyzed by heterogeneous Ru/TiO2 conducted at 150 °C and 35 bar of hydrogen resulted in 90.4% yield of MGBL13. The hydrogenation of MGBL has also been reported over Rh/C, Re/C, Ir/Al2O3, and Ru/Al2O3, where all the catalysts were selective to 3-MTHF (92-97%) at relatively low (2-36%) conversion14. We previously reported on catalysts that were found to be active for the hydrogenation of itaconic acid to MGBL, MGBL to MBDO and dehydration of MBDO to 3-MTHF12. Pd/C was found to provide the highest yield to MGBL (82%) from IA over a temperature range of 160 – 240 °C with 70 – 140 bar of hydrogen. Higher yields of MGBL hydrogenation to MBDO could be achieved at lower Park, et al.



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temperatures, 80 – 120 °C, over the Ru/C catalyst with 79% yield of MBDO. At higher temperatures, hydrogenolysis of MBDO led to undesirable over-hydrogenated products. The dehydration of MBDO catalyzed by Sn-BEA performed at 200 °C resulted in 90% yield to 3-MTHF with about ~100% selectivity8. More recently, we demonstrated the one-pot conversion of itaconic acid to 3-MTHF using a Pd-Re bimetallic catalyst supported on carbon, achieving 80% yield to 3-MTHF at 200 °C and 70 bar H28. Pd was active and selective for sequential hydrogenation of both C=C and C=O bonds (IA to MGBL) without significant over-hydrogenation, but it was not particularly active for ring-opening MGBL to produce MBDO. A second metal, Re, can provide dual capabilities of ring-opening to MBDO and acidic sites for dehydration to 3-MTHF (Scheme 1). In this work, we evaluate the kinetics of the aqueous-phase hydrogenation and dehydration of IA to 3-MTHF using Pd/C and Pd-Re/C bimetallic catalysts. Individual reaction steps are evaluated to determine the overall rate-limiting reaction, and the Pd-Re supported metal catalyst is varied in metal loading to identify the optimal ratio of Pd:Re in the cascade reaction sequence. Kinetic studies of hydrogenation are conducted experimentally in a high-pressure batch reactor over a range of temperatures, 120 – 250 °C, and hydrogen partial pressures, 800 – 1750 psig, using monometallic 10 wt% Pd/C catalyst.

The kinetics of acid-catalyzed dehydration of MBDO to 3-MTHF are further

studied in a micro-volume vial reactor. The role of the Re promoter for ring-opening and dehydration in the hydrogenation of MGBL to form 3-MTHF is discussed.

Experiments. Materials.

Itaconic acid (IA, > 99 %), 2-methylsuccinic acid (MSA, > 99 %), and 2-

methyl-1,4-butanediol (MBDO, > 97 %) were obtained from Sigma-Aldrich. 3-Methyltetrahydrofuran (3-MTHF) and α-methyl-ɤ-butyrolactone (MGBL, > 98 %) were purchased from TCI America and used for analytical standards and chemical reactants. The 10 wt% Pd/C and 5 wt% Pd/C were obtained from Sigma-Aldrich and used as heterogeneous catalysts in the overall sequential hydrogenation. Ammonium perrhenate (NH4ReO4, > 99%, Sigma-Aldrich) and palladium nitrate (Pd(NO3)2, Sigma-Aldrich) were used as metal precursors to synthesize monometallic and bimetallic Park, et al.


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xPd-yRe/C catalysts with varying x:y ratios. A 10 wt% Re /C catalyst was prepared by incipient wetness impregnation using an activated carbon support (Alfa Aesar). The Pd-Re/C bimetallic catalysts supported on carbon were prepared by the incipientwetness impregnation method. An aqueous solution of palladium nitrate (Pd(NO3)2) was impregnated with a volume of 2.0 mL/g of carbon support.

The sample was dried at 100 °C for 12 hr; then a

solution of ammonium perrhenate (NH4ReO4) was used to impregnate a Pd/C sample. The catalysts were then dried at 100 °C for 12 hr and reduced at 400 °C in 10 % H2/Ar for three hours. Reaction measurements.

Hydrogenation reactions were performed in a 100 mL high-

pressure and temperature batch reactor (model 4598HPHT, Parr Instrument Co.). In each test, 0.3 – 1.0 g of reactant (IA, MSA, and MGBL) with 0.02 – 0.10 g of catalyst (Pd/C and Pd-Re/C) were added to the reactor, where water was used as a solvent. IA to MSA hydrogenation was conducted at low temperatures (30 – 40 °C) under 3.4 – 20 bar of hydrogen gas. Hydrogenation of MSA and MGBL were conducted at high temperatures (120 – 180 °C and 200 – 250 °C, respectively) under 54 – 120 bar of H2. Prior to starting the reaction, the reactor was twice purged with N2 to remove any residual air. The reactor was then heated to the desired reaction temperature with vigorous stirring (1,000 rpm) before being pressurized with hydrogen gas. Liquid samples were collected using a reactor sampling port every 10 to 30 minutes. Products were identified using GC-MS (Agilent 7890A connected with Triple-Axis MS detector, Agilent 5975C) and quantified by gas chromatography (GC, Agilent 7890A) equipped with a capillary column (HP-Plot Q, 30 m × 320 mm × 0.5μm) and a quantitative carbon detector (QCD, PolyarcTM, Activated Research Company) / FID combination15,16. All experimental data exhibited a carbon balance of at least 90%. Dehydration of MBDO to 3-MTHF was conducted in a micro vial reactor at temperatures ranging from 120 to 180 °C. A reactant sample of 50-180 μg of MBDO was added to 3.0 mL of water and introduced to a 5.0 mL micro vial reactor. A stock solution of 18.8 mmol L-1 sulfuric acid was prepared using 98.0% of sulfuric acid (Sigma Aldrich) and HPLC water (Fischer Scientific). 100-200 μL (3.13 – 12.5 mmol) of stock solution were added to the reaction solution, after which point the Park, et al.



reactor was heated to the desired temperature. Catalyst Characterization. Metal surface area and dispersion of Pd/C, Re/C and xPd-yRe/C catalysts were investigated with CO-chemisorption using a Quantachrome (ChemBET Pulsar TPR/TPD) automated chemisorption analyzer. Typically, 100-150 mg of sample was loaded into a Ushaped quartz reactor and reduced at 400 °C for two hours using a stream of 5% H2 and balance N2, then cooled down to 35 oC. CO chemisorption was performed at 35 °C by sequential 50 μL pulses of pure CO until the point of saturation, evidenced by a constant signal of CO detected as detected by an in-line thermal conductivity detector. Pd, Re and Pd-Re metal dispersions were calculated assuming a one-to-one stoichiometry of adsorbed CO to metal atoms. Nitrogen adsorption–desorption experiments were carried out for calculation of total surface area of the catalysts. A Micromeritics (ASAP 2020) analyzer was used for the physisorption technique, and the total surface area was calculated based on the Brunauer–Emmett–Teller (BET) method. Elemental analysis of the supported metal catalysts was performed using inductively coupled plasma optical emission spectroscopy (ICP-OES) at Galbraith Laboratories (Knoxville, TN) using a Perkin Elmer (Optima 5300V) atomic emission spectrometer.

To determine the extent of leaching of

metal catalysts in solution, the aqueous product was sampled (after 24 hr reaction at 200 °C with 70 bar H2) and characterized for Pd and Re content with ICP-MS at the University of Minnesota.

Results and Discussion.

To better understand the design of an effective catalyst for the

conversion of IA to 3-MTHF, it was first necessary to develop an understanding of the underlying kinetics of the reaction network. We therefore investigated the apparent kinetics of the aqueous phase hydrogenations, hydrogenolysis and dehydration steps involved in the process by measuring rates, apparent reaction orders and activation energies for each reaction. This approach identified the kinetic bottleneck and led to a catalyst design strategy for enhancing the slowest reaction, lactone ring opening. Hydrogenation of IA to MSA on Pd/C. Hydrogenation of the C=C bond in IA to form MSA over the Pd/C catalyst was found to be relatively facile, as evidenced by complete conversions at ambient temperatures and short reaction times (

Multi-Functional Cascade Catalysis of Itaconic Acid

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