C6 Sugar Alcohols by Hydrolytic Hydrogenation of

Subscriber access provided by UNIVERSITY OF TOLEDO LIBRARIES

Article

Production of C5/C6 sugar alcohols by hydrolytic hydrogenation of raw lignocellulosic biomass over Zr based solid acids combined with Ru/C Qiying Liu, Tao Zhang, Yuhe Liao, Chi-Liu Cai, Jin Tan, Tiejun Wang, Songbai Qiu, Minghong He, and Longlong Ma ACS Sustainable Chem. Eng., Just Accepted Manuscript • Publication Date (Web): 26 May 2017 Downloaded from http://pubs.acs.org on May 28, 2017

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 free 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 accessible to all readers and 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.

ACS Sustainable Chemistry & Engineering 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 44

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 Sustainable Chemistry & Engineering

Production of C5/C6 sugar alcohols by hydrolytic hydrogenation of raw lignocellulosic biomass over Zr based solid acids combined with Ru/C ,1

Qiying Liu* , Tao Zhang1,2, Yuhe Liao1, Chiliu Cai1, Jin Tan1, Tiejun Wang1, Songbai Qiu1, Minghong He1, Longlong Ma*,1 1

CAS Key Laboratory of Renewable Energy, Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou, 510640, P. R. China 2 Nano Science and Technology Institute, University of Science and Technology of China, Suzhou, 215123, P.R. China Qiying Liu, No.2 Wushan Nengyuan Road, Tianhe District, Guangzhou, 510640, China; Tao Zhang, 1. No.2 Wushan Nengyuan Road, Tianhe District, Guangzhou, 510640, China; 2. No.166 Renai Road, High Education District, Dushuhu, Suzhou, Suzhou, 215123, China; Yuhe Liao, No.2, Wushan Nengyuan Road, Tianhe District, Guangzhou, 510640, China; Chiliu Cai, No.2, Wushan Nengyuan Road, Tianhe District, Guangzhou, 510640, China; Jin Tan, No.2, Wushan Nengyuan Road, Tianhe District, Guangzhou, 510640, China; Tiejun Wang, No.2, Wushan Nengyuan Road, Tianhe District, Guangzhou, 510640, China; Songbai Qiu, No.2, Wushan Nengyuan Road, Tianhe District, Guangzhou, 510640, China; Minghong He, No.2, Wushan Nengyuan Road, Tianhe District, Guangzhou, 510640, China; Longlong Ma, No.2, Wushan Nengyuan Road, Tianhe District, Guangzhou, 510640, China; Corresponding author: Qiying Liu, Tel: +86-20-37029721, Fax: +86-20-87057737, E-mail: [email protected]; Longlong Ma, Tel: +86-20-87057673, Fax: +86-20-87057673, E-mail: [email protected];

1

ACS Paragon Plus Environment


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

Abstract: Producing chemicals from lignocellulosic biomass is important in view of the huge availability of biomass and positive environment significance by reducing carbon emission due to fast carbon cycle during biomass growth and applications. Here, we prepared zirconium based solid acids for hydrolytic hydrogenation of raw lignocelluloses to co-produce C5/C6 sugar alcohols (the important platform for downstream chemicals and fuel production) as combined with commercial Ru/C. Among these solid acids, the amorphous zirconium phosphate (ZrP) presented the largest acidic sites with medium and strong acidity as majority, showing the highest goal sugar alcohols yield of 70% at optimal reaction condition. During pennisetum transformation, this combined catalyst was reusable despite the activity of the second run was lower than the initial one and the activity could be recovered by re-calcination of spent ZrP. The primary structure of survived lignin was remained after cellulose and hemi-cellulose were converted, showing the significance for fractional biomass applications if considered the further transformation of lignin. Key words: Biomass, Sugar alcohol, Hydrolytic hydrogenation, Solid combined catalyst

2


Page 2 of 44

Page 3 of 44

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


Introduction Lignocellulosic biomass produced by photosynthesis is the most abundant, renewable resource in nature.1 Using lignocellulosic biomass as the feedstock to produce C5/C6 sugar alcohols which are widely used for downstream chemicals and fuels production, is of importance and attracted considerable concerns regarding to the positive environment and resource significance.2 Among kinds of biomass resources, cellulose and hemi-cellulose possess about 60-80% of total weight.3 Thus efficient conversion of cellulose and hemi-cellulose into C5/C6 sugar alcohols are the key for biomass application. Traditionally, C5/C6 sugar alcohols (mainly xylitol and sorbitol) were mainly depended on hydrogenation of glucose/xylose at mild reaction conditions.4,5 Although high target products yield can be obtained by using supported metal catalysts, the limited sugars from fermentation of edible starches are necessary for this process. Comparatively, using cellulosic biomass to produce C5/C6 sugar alcohols shows significant source preference. Microcrystalline and ball-milled cellulose are the most used feedstock for producing sorbitol by hydrolytic hydrogenation, due to the relatively simple molecular structure and less side products.6 The catalysts used in this process mainly contained acidic catalysts for cellulose hydrolysis and metal catalysts for glucose hydrogenation to sugar alcohols.7,8 Mineral acids such as H2SO4,9 HCl,9 H3PO49,10 and heteropoly acids11,12 combined with Ru, Pd, Ir and Pt7,13-18 catalysts showed high sugar alcohol yields because of the efficient hydrolysis for cellulose by the above mentioned acids. However, these homogeneous acids are hardly recovered and result in waste water emission. Supported metals Ru, Ir, Pt, Ni and Rh on acidic supports were also used as bi-functional catalysts for this process, but the sugar alcohol yield and/or cellulose conversion are relatively low.19-22 Very recently, Fukuoka 3



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

et al. prepared biomass derived carbon based catalyst for eucalyptus hydrolysis to sugars.23 This catalyst was highly efficient to obtain the target sugars yield of more than 90%. In addition, hemi-cellulose was also used as the feedstock to produce the corresponding sugar alcohols. Due to the amorphous nature, hemi-cellulose is easily hydrolysed and hydrogenated to the goal products with the yield of more than 80% under relatively mild conditions.24,25 Comparing to cellulose, raw lignocellulosic biomass has more complex structure which mainly consists of cellulose, hemi-cellulose and lignin. Converting the former two components into C5/C6 sugar alcohols (mainly xylitol and sorbitol) by hydrolytic hydrogenation is more feasible based on resource priority. Different kinds of raw biomass such as beet fibre and inulin (starch biomass), hardwood powder, wood chips, bagasse, rice husk, wheat straw and birch wood, etc. were used as the feedstock to directly produce sugar alcohols by using supported Ru, Pt and Pt contained bi-metal catalysts.26-31 Sugar alcohols yield is generally dependent on class and component content of original biomass, and high sorbitol/xylitol yield of 50% could be obtained with assistance of water soluble heteropoly acid for efficiently decomposing cellulose and hemicellulose.28,30 Using solid acids for this process shows significance owing to their easily recovering, but relative research is rarely reported hitherto. Metal phosphates showed wide applications in hydrolysis of lignocellulosic biomass and dehydration of monosaccharides to furan derivatives as particular solid acid catalyst.32,33 Followed by our previous work for cellulose transformation to C6 sugar alcohols,34,35 we used kinds of raw lignocellulosic biomass as the feedstock to co-produce C5/C6 sugar alcohols by different zirconium based solid acid combined with commercial Ru/C in aqueous phase. The solid acids were screened based on their activity and target products yield. The process parameters of typical 4


Page 4 of 44

Page 5 of 44

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


biomass were studied and the possible reaction pathway was discussed based on the synergistic effect of acid and metal catalyst.

Experimental section Catalyst preparation 5 wt% Ru/C and ZrO2 were purchased from Aladdin Industrial Inc. (Shanghai, China). ZrO2 was calcined at 723 K for 4 h before use. Zirconium phosphate (ZrP) was prepared by precipitation of ZrOCl2.8H2O with NH4H2PO4 at the P/Zr molar ratio of 2. The flocculent mixture was stirred for 1 h and then filtered. The white precipitate was washed with deionized water until the pH of the filtrate of 7, and was then dried at 373 K overnight. Before reaction, the ZrP was calcined at 673 K for 4 h in air. Comparatively, the 5 wt% Ru/ZrP was prepared by initial wetness impregnation. 0.135 g RuCl3.xH2O (Ru > 37%) was dissolved in 30 ml H2O to form a homogenous solution under agitation. 1 g freshly calcined ZrP was then introduced into the solution. The mixture was stirred for 5 h at room temperature followed by removing water at 333 K. The solid remained was dried at 373 K overnight and calcined at 673 K for 4 h. Prior to reaction, the catalyst was reduced at 623 K for 2 h by flowing H2. SiO2-ZrO2 composite oxide was prepared by our previous report.36 Briefly, Zr(OH)4 precipitate was obtained by adding NH3·H2O into ZrOCl2·8H2O solution with continuous agitation. Si(OH)4 was prepared by the same procedure but with NH4NO3 saturated solution as the precipitator. The NH4NO3 saturated solution was directly added to the Na2SiO3 solution. Zr(OH)4 and Si(OH)4 were then blended with vigorous stirring at a molar ratio of Si/Zr = 3. The mixed precipitate was aged at

5



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

348 K. After filtered and fully washed by deionized water, the solid was dried at 393 K and calcined at 773 K for 5 h before use. SO42-/ZrO2 was prepared by a typical procedure. 5 g ZrO2 (bought from Aladdin Industrial Inc., Shanghai, China) pre-calcined at 723 K was dispersion in 50 ml H2O under agitation for several minutes. 50 ml, 0.5 M of H2SO4 solution was then introduced. The mixed solution was further aged for 1 h at ambient temperature. The solid was recovered by filtering, drying at 353 K and calcined at 873 K for 3 h before use. WO3/ZrO2 catalyst was prepared by initial wetness impregnation. 0.27 g ammonium metatungstate hydrate ((NH4)6H2W12O40.nH2O) dissolved in 20 ml H2O, then 5 g ZrO2 (obtained from Aladdin Industrial Inc., Shanghai, China) pre-calcined at 723 K was introduced into the above solution under continuous stirring. After 3 h, the excessive water was removed by evaporating at 333 K. The obtained solid was dried at 373 K overnight and calcined in air at 923 K for 3 h prior to reaction. The WO3 loading in the final catalyst was calculated as 5% by weight. Catalyst characterization X-ray powder diffraction (XRD) diffractogram of sample was measured by a X-ray diffractometer (X’Pert Pro MPD, Philip) with Cu Kα radiation (λ=0.154 nm) operated at 40 kV and 100 mA. BET specific surface area was measured by N2 isothermal adsorption-desorption profiles at 77 K with using a QUADRASORB SI-MP-10/PoreMaster 33 analyzer equipped with QuadraWin software. The mesoporous volume and pore size distribution were calculated by the desorption branch using BJH method.

6


Page 6 of 44

Page 7 of 44

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


Ammonia-temperature programmed desorption (NH3-TPD) was conducted in a U-tube quartz reactor

using

an

ASIQACIV200-2

automatic

physical/chemical

adsorption

analyzer

(Quantachrome, US). MS was used to determine the effluent NH3 from catalyst. The quantitative analysis of acidic sites was performed by using a calibration loop of 250 µl. H2-chemisorption of Ru/C catalyst was tested with using a Quantachrome-ASIQACIV200-2 automated gas sorption analyzer. The catalyst was treated at 573 K for 2 h under hydrogen atmosphere. To clean the catalyst surface, the samples were further heated to 623 K for 0.5 h under nitrogen, and then cooled to 323 K for the H2-chemisorption test. TEM images were gained on a Gatan Ultra scan camera and a JEOL JEM-2100F instrument operated at 200 kV. The sample was ultrasonically dispersed in ethanol, and drops of the suspension were placed on a carbon-coated copper grid and then dried in air. SEM images were recorded using an S-4800 instrument operated at 2 kV. The samples were placed on a conductive carbon tape adhered to an aluminum sample holder. EDS was used to determine the P/Zr molar ratio of ZrP. Elemental analyses for Zr and Ru were performed by inductively coupled plasma atomic emission spectroscopy (ICP-AES) on a Plasma-Spec-Ⅱ spectrometer. The filtrate was collected after hydrothermal pretreatment and diluted by water to the appropriate concentration to meet the detecting range of the instrument. FT-IR spectra were recorded on a Bruker TENSOR27 spectrometer with a resolution of 4 cm-1. The samples were pelleted with KBr before measurement. The pyridine absorbed FT-IR spectra were recorded on the same instrument. Prior to measurement, the self-supported pellet was pretreated at 673 K for 1 h in He and then cooled to 423 K for recording the pristine FT-IR 7



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

spectrum. Afterwards, the pyridine vapor was introduced into the cell at 423 K and kept for 2 h until the saturated state was achieved. The excess pyridine was purged by He at the same temperature for 12 h. The spectra were obtained by subtracting the pristine ones. TG analyses were implemented on a NETZSCH-STA 409PC DSC-SP Thermal analyzer by increasing the temperature from 300 K to 1000 K at 10 K/min under an air flow rate of 30 ml/min. Biomass transformation 0.5 g solid acid, 0.1 g 5 wt% Ru/C, 1 g biomass (40-60 mesh and dried at 378 K to remove the moisture) and 50 ml H2O were added into a 100 mL stainless steel autoclave. Before reaction, the reactor was flushed with hydrogen for several times to remove the residue air and pressurized to 6 MPa of hydrogen pressure at room temperature. Then, the reactor was heated to a given temperature under rigor agitation and kept at the given temperature for a certain period. After reaction, the reactor was quickly cooled to room temperature with iced water. The product mixture was separated by filtration, and the water soluble products were detected by HPLC instrument. For reusability, the mixed catalyst (ZrP and Ru/C) was recovered by centrifuging from reaction mixture, thoroughly rinsed by de-ionic water and directly used for the next cycle without any treatment. 93 wt% of the collected catalyst mixture could be recovered by drying at 373 K followed by calcination at 673 K, showing the efficiency of this separation procedure. The liquid was obtained by a 0.22 µm syringe filter for HPLC analysis and the solid residue was rinsing by de-ionic water, dried in vacuum for further analysis. After reaction, the dissolved total organic carbon (TOC) was analysed by using an element analyser (vario EL cube, Germany). The liquid was obtained by centrifuging catalyst followed by filtering solid residue, and then was diluted to a proper concentration for the TOC measurement. 8


Page 8 of 44

Page 9 of 44

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


Materials and product analysis Five raw biomass materials (switchgrass, corncob, cornstalk, pennisetum and sugarcane bagasse) were collected from Guangdong province, China. These materials were air-dried and grinded to 40-60 mesh before measurement. Analytic graded glucose and xylose were purchased from Aladdin Industrial Inc. (Shanghai, China). Microcrystalline cellulose (MCC, Avicel○ R PH101, Fluka) was obtained from Sigma-Aldrich and dried overnight at 343 K prior to use. Biomass composition. The moisture in raw materials was determined by drying at 378 K until constant weight obtained. The content of ash was analysed by completely combusting the materials at 823 K for 4 h in air. The extractives in biomass were determined by Soxhlet extraction with 95 % ethanol contained aqueous solution. The contents of glucan, xylan and lignin of raw materials were determined according to the laboratory analytical procedure (LAP) for biomass analysis offered by the US National Renewable Energy Laboratory (NREL).37 The total sugars in the pretreatment liquid were calculated after a secondary hydrolysis of oligosaccharide into monosaccharide with 4 wt% sulfuric acid at 394 K for 45 min.

38

Sugars and other degradation

products were quantitatively determined by HPLC instrument. The content of lignin was calculated by subtracting moisture, total sugars, ash and extractives from raw biomass. The content of inorganic elements in biomass materials were determined by Wavelength Dispersive X-ray Fluorescence Spectrometer (AXIOS mAX petro, Netherlands). Product analysis. The aqueous products were detected by high performance liquid chromatography (HPLC; Waters e2695, Refractive Index Detector, RID 2414). A SUGAR SH1011 column (8 mm*300 mm) was used to analyse the polyols and sugars with using 0.5%

9



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 10 of 44

H2SO4 aqueous solution as the mobile phase. External standard method was used for quantification. The biomass conversion was determined by the weight difference of biomass before and after reaction, and was calculated as given by:

Conversion (%) =

where:

m biomass,0

residual

m biomass,0 − m biomass × 100% m biomass,0

(1)

is the weight of biomass charged in the reactor, m biomass is the weight of

biomass

after

reaction,

mbiomass

and

was

m biomass = m residue − m catalyst where:

calculated

as

follows: (2)

mresidue is the weight of solid residue after reaction; m catalyst is the weight of charged

solid catalysts (solid acid and Ru/C). The yield of product originated from cellulose and hemi-cellulose was determined by the carbon moles in product and the carbon moles in the cellulose and hemi-cellulose charged in the reactor (the content of cellulose and hemi-cellulose was determined by biomass composition). The yield was calculated as given by:

Yproduct，i(%) =

Cproduct，i C cellulose + Chemi −

cellulose

(3)

× 100%

where: C product ，i is the carbon moles of product i; C cellulose

and C hemi - cellulose are the

carbon moles of cellulose and hemi-cellulose charged in reactor, respectively, which were calculated as follows:

Ccellulose =

m cellulose ×6 M(C6H10O5)

C hemi - cellulose =

(4)

m hemi - cellulose ×5 M(C5H8O4)

(5)

10


Page 11 of 44

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


wh1ere: M(C6H10O5) and M(C5H8O4) are the molecule weight of anhydroglucose and anhydroxylose unit, respectively.

Results and discussion Composition analysis of raw lignocellulosic biomass Table S1 gave the glucan, xylan and lignin contents in different lignocellulosic biomass. Although these contents varied by different species, the cellulose (mainly glucan) and hemi-cellulose (mainly xylan) were in the range of 34-39% with sugarcane bagasse having the maximum and 17-31% with corncob showing the maximum, respectively. The lignin content of biomass varied in 14-26% and switchgrass possessed the largest one. In addition, all the biomass contained water residue of 6-11% and extractives mainly including protein and lipid species with the total content of 3-10%. The ash residue was obtained by combusting biomass at 823 K to remove organic species. As shown in Table S2, the elements were mainly composed of K, Si, Ca, Mg, Al and Fe with the former three as the majority. Besides, trace amount of P was also detected but the contents were lower than 10 ppm no matter what kind of biomass was measured. Pennisetum conversion to sugar alcohols For lignocellulosic biomass transformation to C5/C6 sugar alcohols in aqueous solution and H2 atmosphere, acid is necessary to hydrolyze cellulose and hemi-cellulose macromolecules to the relative C5/C6 sugars followed by hydrogenation to the target products over metal catalyst. Owing to the complex of sugar composition in a raw lignocellulosic biomass (glucose in cellulose and xylose, glucose, arabinose and galactose in hemi-cellulose) and sugar isomerization to another one during acid catalysed depolymerisation (for example, from glucose to fructose)39,40, we proposed the possible glucose, fructose and galactose as C6 sugars and the relative hydrogenated sorbitol, 11



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

mannitol and galactitol as C6 sugar alcohols; similarly, the xylose and arabinose were defined as C5 sugars, and the corresponding xylitol and arabitol were indicated as C5 sugar alcohols. The blank experiment was first implemented without using catalyst (Table 1). The pennisetum conversion was lower than 10% with minor C5/C6 sugars observed, indicating the essential role of catalyst in this process. We prepared different zirconium contained solid acids for co-producing C5 and C6 sugar alcohols from pennitsetum (a typical breeding grass for renewable chemical and fuel production) as combined with the commercial Ru/C. Due to that acid catalysed hydrolysis of cellulose and hemi-cellulose to relative sugars is proposed as the rate-determined step as comparing to sugars hydrogenation,9,13 it’s reasonable for focusing on Ru/C as the hydrogenation catalyst and carried out the influence of solid acids on this process. As shown in Table 1, only 17% of pennisetum conversion was obtained by using ZrO2, meanwhile, the total C5/C6 sugar alcohols yield was about 12% with minor C6 sugars intermediate (mainly glucose and trace fructose and galactose) and hydrogenolysis products such as erythritol, glycerol, 1,2-propanediol and ethylene glycol. Among sugar alcohols, the C5 counterparts presented as the majority, indicating that amorphous hemi-cellulose is more easily hydrolyzed to the relative sugars served as precursor for C5 sugar alcohols when comparing to the crystalline cellulose.28,39 Over SiO2-ZrO2 and WO3/ZrO2 catalysts, the both increased activities and C5/C6 sugar alcohols yield were observed. Meanwhile, the enhanced side products by sugar/sugar alcohol hydrogenolysis were obtained over WO3/ZrO2. This is possibly responsible for the W species promoted hydrocracking of sugar intermediates and/or target sugar alcohols to the small molecular C2-C4 polyols.41 When SO42-/ZrO2 was used, both pennisetum conversion and total target sugar alcohols yield were significantly increased to 49% and 48%, respectively. Meanwhile, the increased C6 sugars intermediate and the reduced C2-C4 12


Page 12 of 44

Page 13 of 44

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


hydrogenolysis products were observed as comparing to WO3/ZrO2. Interestingly, the pennisetum conversion of 54% and the highest C5/C6 sugar alcohols yield of 61% were obtained by using ZrP as the solid acid. It’s noted that no C5 sugars intermediate was detected over all solid acids, again demonstrating the easier hydrolysis of hemi-cellulose and hydrogenation of C5 sugars. The sole Ru/C was used for this process and much lower activity was observed as comparing to the combined catalyst, implying that acid catalyst plays the important role in obtaining the target products with high yield by enhancing polysaccharides hydrolysis. Comparatively, over the only ZrP without Ru/C, despite the pennisetum conversion was about 40%, the target C5/C6 sugar alcohols were trace amount due to the absence of metal for hydrogenation. In addition to the C5 and C6 sugars with the yield of about 7%, the dehydration products 5-hydroxymethyl furfural (the yield of 5%), furfural (the yield of 2%) and rehydration product levulinic acid (the yield of 12%) and trace amount formic acid/acetic acid (the total yield of 3%) were detected. This low yields is ascribed to the fact that the sugar intermediates and/or furan derivatives can be easily condensed into humins in acidic environment and single aqueous phase. We measured the textural and acidic properties of solid catalysts in Table 2. The commercial ZrO2 showed low surface area of 21 m2/g and its pore volume and size were 0.04 ml/g and 28 nm, respectively. Meanwhile, its acid density was the lowest 0.12 mmol/g with the weak acidity of below 523 K based on NH3 desorption peak. After supporting WO3 and H2SO4, the textural properties changed a little, but the acid density and strength remarkably increased. For SiO2-ZrO2 prepared by sol-gel technology, the surface area and volume were the largest among those five solid acids and the pore size was about 8 nm. The acid density was 0.62 mmol/g with the weak acidity (the NH3 desorption peak was below 623 K). ZrP showed large surface area of more than 13



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

120 m2/g with moderate pore volume and size. Interestingly, the acid density presented the maximal 1.75 mmol/g with the medium and strong acidity as majority (Figure 4C). Dependent on the results in Table 2, it seems that pennisetum conversion and sugar alcohol products yield are not straightforward to the surface area and porosity, but determined by the acidic properties of solid acids with those possessing more acidic sites and strong acidity showing the higher activity and target products yield. The Ru/ZrP was tested under the same reaction condition (Table 1), but the obviously reduced activity and target sugar alcohols yield were observed as comparing to ZrP combined with Ru/C. This is due to that supporting Ru on ZrP decreased the acidic sites as well as the acidity of Ru/ZrP besides the lower dispersion of Ru to Ru/C, despite its similar textural properties to pure ZrP (Table 2 and Figure S1). After reaction by ZrP combined with Ru/C, we collected the solid residue by centrifuging catalyst followed by filtration, rinsing with de-ionic water to remove organic compounds (this process was repeated for three times) and drying in vacuum at 323 K for 8 h. The composition analysis showed that cellulose and hemi-cellulose in pennisetum were largely converted and lignin was remained lignin as the majority (Table S1), indicating this combined catalyst is highly efficient for converting polysaccharides into sugar alcohols. As indicated in Figure 1A, the pristine pennisetum surface was dense and rather smooth (the inset in Figure 1A). After reaction, the surface became loose, porous and irregular blocks were observed, which is due to the tracks remained by inner hemi-cellulose and cellulose hydrolysis. Furthermore, the groups in survival lignin residue were detected by FT-IR (Figure 1B). The substituted phenolic ring (1609 cm-1, 1512 cm-1, 1211 cm-1 and 1110 cm-1) and carbonyl group (1705 cm-1) in lignin linked by esters were clearly observed. Meanwhile, a broad peak at 3410 cm-1 and a peak at 2930 cm-1 proposed the 14


Page 14 of 44

Page 15 of 44

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


existence of phenolic OH groups and side hydrocarbon chains of phenolic ring, respectively, which are well consistent with the previous report.42 These findings demonstrated that the primary lignin structure was basically kept after the cellulose and hemi-cellulose was converted, showing significance for fractional and comprehensive utilization of biomass if considering further applications of lignin component. The balance of acid and metal is the key for obtaining the target C5/C6 sugar alcohols in this process. According to the previous reports,21,25 the influence of molar ratios of surface acid density in ZrP (determined by NH3-TPD) to surface Ru atom in fresh Ru/C (determined by dispersion by H2-chemisorption) on C5/C6 sugar alcohols yield were conducted to monitor this balance (Figure 2 and Table S3). When no ZrP was introduced, the both yields were lower than 7%, demonstrating the essential role of acidic ZrP for effectively hydrolysing cellulose and hemi-cellulose. As ZrP was added with increasing amounts, the both yields raised significantly. The highest C5 and C6 sugar alcohols yield was observed at the ratio of 28.6 and 34.7, respectively. However, as the ratio was further increased, the both yields reduced but the C5 sugar alcohols dropped more remarkably. Comparing to C6 sugar alcohols, the maximal C5 sugar alcohols obtained at relatively low acid to metal ratio indicated that the easy decomposition of hemi-cellulose need less acid and more metal. In this process, the monosaccharide intermediates encounter competitive acid-catalysed degradation and metal-catalysed hydrogenation simultaneously. It’s possible that the excessive acid resulted in the sugar intermediates subjected to the other acid-catalysed reactions rather than being hydrogenated to sugar alcohols, showing the reduced C5/C6 sugar alcohols. The results are consistent with the previous report.25

15



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

Taking the ZrP combined with Ru/C showed the best performance in pennisetum conversion to C5/C6 sugar alcohols, we further implemented controlled experiments including reaction temperature, time, H2 pressure and pennisetum concentration with focusing on this catalyst. As shown in Figure 3A, the pennisetum conversion increased with rising the reaction temperature from 443 K to 488 K, and the maximum C5/C6 sugar alcohols yield was obtained at 473 K. At low temperatures, C5 and C6 sugars presented as intermediates while with significantly reduced for C6 sugars and vanished for C5 sugars at the temperatures of higher than 473 K. The high temperature also resulted in the increased side products such as C2-C4 polyols from sugars and sugar alcohols, and isosorbide from sorbitol dehydration over acid catalyst.43 Considering more side products were detected at 473 K, we implemented the experiments at 458 K to more clearly monitor the intermediates tendency and possibly higher sugar alcohols yield at different time. As shown in Figure 3B, the pennisetum conversion and C5/C6 sugar alcohols yield increased with increasing reaction time and obtained the highest ones of 58% and 70%, respectively, at the time of 6 h. More than 20% of C5 sugars were observed but no obvious C6 sugars were detected at initial reaction. This is due to that the amorphous hemi-cellulose encompassed around crystalline cellulose firstly contact the catalyst and thus lead to the preferable conversion to the relative sugars. As reaction proceeded, the C2-C4 polyols increased but the total yield was no more than 5%, indicating the hydrogenolysis is supressed at the temperature of 458 K. The influence of H2 pressure was presented in Figure 3C. Because H2 was consumed by hydrogenation, the higher H2 pressure promoted cellulose and hemi-cellulose transformation with obtaining the increased conversion and target sugar alcohols yield. On the other hand, the hydrogenolysis products was significantly reduced from initial 17% to final 4% as the H2 pressure increased from 4 MPa to 8 16


Page 16 of 44

Page 17 of 44

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


Mpa, which is responsible for the restraint of such kind volume expanded hydrogenolysis. In Figure 3D, we also implemented pennisetum concentration test over the same combined catalyst. As the concentration increased from 1% to 5% by weight, the pennisetum conversion reduced from nearly 60% to 32% and the C5/C6 sugar alcohols yield decreased from 68% to 38%, demonstrating this combined catalyst can be adaptable to high biomass concentration for producing target sugar alcohols. As the concentration was further increased to 10%, the pennisetum conversion and the total sugar alcohols yield reduced to 16% and 11%, respectively, and the C5/C6 sugars presented as the major intermediates, indicating incomplete conversion as well as partial hydrogenation occurred as large amount feedstock used in this case. Despite the individual C5/C6 sugar alcohol yield are lowered than the previously reports with using cellulose/hemi-cellulose as the feedstock,16,17,25 the total yield of 70% produced from the raw biomass over the current solid combined catalyst is comparable to the previous report which was obtained in methanol and higher reaction temperature.30 Considering lignin could be possibly degraded into oligomeric species and dissolved in water under the present reaction condition (these species can not be detected by HPLC), the TOC analyses of aqueous product mixture were carried out to calculate carbon balance. The carbon balance was higher than 90% for all experiments investigated, indicating less 10% of lignin is depolymerized into dissolved oligomers. For this process (Figure S3), hemi-cellulose in raw biomass is firstly hydrolysed to C5 and C6 sugars followed by easily hydrogenation to the corresponding sugar alcohols, owing to its amorphous nature and outer location. On the other hand, due to the huge hydrogen bonds and crystalline nature, cellulose hydrolysis is relatively slow, resulting in the slow release and 17



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

consumption of glucose over the current solid acid combined with metal catalyst. Besides the main pathway for producing target sugar alcohols, sugar intermediates and sugar alcohols could further convert into C2-C4 small polyols by C-C bond cleavage. The high sugar alcohols yield produced means the good balance between polysaccharides hydrolysis over ZrP and sugars hydrogenation over Ru/C. Particularly, no obvious furfural by xylose dehydration and 5-hydroxymethyl furfural by C6 sugars dehydration were detected, indicating that the humins, which are generally proposed from polymerization of furans,44 is significantly suppressed. This is further evidenced by the comparing experiment with using cellulose as the feedstock over the same combined catalyst (this is because the black humins could be easily resolved from the white cellulose if humins were produced). The photograph after reaction showed that no black solid was observed in solution and on the wall (the black solid in bottom is originated from Ru/C, Figure S4), demonstrating no humins formed over the present catalyst. The physicochemical properties of ZrP and Ru/C catalyst were showed in Figure 4 and 5, respectively. The ZrP synthesized by our technology was amorphous regarding to the XRD pattern. The TEM images showed that its particle size was hardly resolved, and the HRTEM showed no well-defined lattice fringes, indicating the amorphous nature of ZrP. This is well consistent with the XRD measurement. NH3-TPD revealed that ZrP possesses one main desorption peak at 580 K with a wide shoulder extended to 850 K, which is responsible for significant medium and strong acidic sites on surface. From pyridine absorbed FT-IR of ZrP, the distinct absorbencies at 1545 cm-1 and 1450 cm-1 were observed, indicating Bronsted and Lewis acidic sites were concurrently presented on the pristine ZrP and the hydrothermally pretreated ZrP followed by recalcination (Figure 4D). The Lewis and Bronsted acidic sites are originated from the vacant orbits of Zr4+ 18


Page 18 of 44

Page 19 of 44

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


contained framework of four-coordination and P-OH groups, respectively.45,46 The minor Bronsted acid perhaps implies the existence of polyphosphates by dehydration of P-OH groups to form P-O-P bonds. For Ru/C, a broad and weak diffraction observed at the 2θ between 35 º-50 º, implying the highly dispersion of Ru on support surface with the particle size below the XRD measurement threshold, due to the large surface area of support (Table 2). The average Ru particle size were about 2 nm by further TEM measurement. Such tiny Ru particles are possibly responsible for the fast sugars hydrogenation, leading to the high sugar alcohols yield with suppressed dehydration side products. Owing to the C5 and C6 sugar intermediates were detected during biomass conversion. We implemented the comparative hydrogenation experiments by using glucose and xylose as the examples over ZrP and Ru/C catalyst (Figure 6). At the reaction time of 0.5 h, the both sugars conversions were more than 90% and the relative C6 and C5 sugar alcohol yields were more than 80%, respectively, with the both hydrogenolysis side products of less than 5%. As the time was elongated to 1 h, xylose/glucose was completely converted and about 90% of xylitol/sorbitol yield was obtained. These results indicate that over the present combined catalyst, the sugar intermediates from biomass hydrolysis could be rapidly hydrogenated to target products with high selectivity at short time. Moreover, we also used crystalline cellulose to produce C6 sugar alcohols at the same catalyst and reaction condition to pennisetum conversion. 56% of cellulose conversion and 44% of C6 sugar alcohols yield were obtained with the glucose intermediate and hydrogenolysis products below 3%. This means that our ZrP and Ru/C catalyst possess good hydrolysis and hydrogenation properties, promoting the production of sugar alcohols from biomass. It’s noted that no dehydration products of sorbitol and xylitol, such as sorbitan/isosorbide 19



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

and anhydroxylitol, were detected in the presence of acidic ZrP. This demonstrates that the target C5/C6 sugar alcohols produced from raw biomass are quite stable in the present catalyst and experimental conditions. The stability of ZrP and Ru/C catalyst was tested in Figure 7. For the second cycle, the pennisetum conversion reduced from the initial 55% to 44% with the sugar alcohols yield decreased from the initial 60% to 45%. After the third run, both conversion and sugar alcohols yield were comparable to the second cycle, indicating the stability of our combined catalyst. Due to the difficulty for testing the single ZrP or Ru/C reusability in this process, we evaluated the stability of ZrP by hydrothermal treatment of the fresh one at 473 K for 2.5 h followed by re-calcination at 673 K for 4 h. Combining with the fresh Ru/C, the pre-treated ZrP showed the comparable performance to the fresh one in terms of pennisetum conversion and sugar alcohols yield. Moreover, when using the fresh ZrP combined with the hydrothermal treated Ru/C at 473 K for 2.5 h without further calcination, the similar conversion and yield were still observed. This demonstrated that the activity loss for the first cycle is relative to ZrP, not Ru/C. We compared the P/Zr molar ratio of fresh and hydrothermal treatment ZrP by EDS during SEM measurements (Figure S5), and found that 3.1% of P was released into water during pre-treatment. This P loss is responsible for the reduced acidic sites that are necessary for cellulose/hemi-cellulose hydrolysis and thus results in the inferior performance when the second run was implemented.47 On the other hand, we collected the filter liquor after hydrothermal treatment of fresh ZrP and Ru/C and detected the possible Zr and Ru residues using ICP-AES. The results showed that the Zr and Ru loss were 1.5 ppm and 12 ppm, respectively, indicating that the both metal leaching is neglectable. Besides P loss, the XRD pattern and TEM images showed that 20


Page 20 of 44

Page 21 of 44

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


ZrP underwent the amorphous to crystalline transformation during hydrothermal treatment and re-calcination (Figure 8A and C).48 After hydrothermally treatment and re-calcination, however, the large acid density of 1.71 mmol/g and acid distribution (Table 2 and Figure 8D) are very similar to the fresh one. In ZrP, the Zr-O-P, P-OH and P-O-P groups were detected by FT-IR.49 After hydrothermal treatment, the primary Zr-O-P structure was retained but the P-O-P bonds reduced accompanied by the increased P-OH groups, indicating the P-O-P is hydrolysed to P-OH during the treatment.47 This hydrolysis resulted in weight increase, which is further demonstrated by TG measurement (Figure 8B). After hydrothermal treatment, the Ru particle was slightly increased in size, but still highly dispersed on C surface with the dispersion of 39% (Figure 9 and Table 2), indicating its hydrogenation performance of sugars could be preserved. This is well consistent with the result obtained by Figure 7. Overall, the remaining of large acidic sites with significant medium/strong acidity of ZrP and hydrothermally stable Ru/C explained the good reusability in this process. Different raw biomass conversion to sugar alcohols According to the highly efficiency of ZrP combined with Ru/C in pennisetum transformation to C5/C6 sugar alcohols, we further used this catalyst to test the other raw biomass (sugarcane bagasse, corncob, cornstalk, switchgrass) under the same reaction condition (Table 3). All the biomass conversion was more than 50%, implying more than 90% of cellulose and hemi-cellulose were converted. Meanwhile, the C5/C6 sugar alcohols yield is in the range of 30-50% based on biomass type. Among these sugar alcohols, xylitol and sorbitol are the main products with the both amounts of more than 80%. Besides, C6 sugar intermediate and C2-C4 polyols by hydrogenolysis were also detected but the both yields were below 10%. These results proposed 21



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

that our solid combined catalyst is generally efficient for transforming typical agricultural waste and energy plant to C5/C6 sugar alcohols. Here, we obtained the mixed C5/C6 sugar alcohols of high yield from raw biomass in aqueous phase. In view of industrial application, this mixture is hardly separated from each other. Considering hemi-cellulose could be easily converted at mild reaction conditions as compared with cellulose,25,28 a two-step transformation is possibly imagined, that is, the hemi-cellulose can be selectively converted at mild temperature, leaving the cellulose for the second conversion at elevated temperature. Thus, the purified C5 and C6 sugar alcohols could be obtained individually by choosing a proper separation procedure.

Conclusions We prepared different zirconium based ZrO2, SiO2-ZrO2, WO3/ZrO2, SO42-/ZrO2 and ZrP catalysts, and used as solid acids combined with commercial Ru/C for hydrolytic hydrogenation of pennisetum to C5/C6 sugar alcohols in aqueous phase. Among those solid acids, the amorphous ZrP possessed the largest acid density with medium and strong acidities, which was highly efficient for this process by promoting the rate-determined hydrolysis of polysaccharides. Under the optimal reaction condition, the highest goal sugar alcohols yield of 70% was obtained. The retaining of primary lignin structure after reaction showed significance for fractional applications of a lignocellulosic biomass considering the possible conversion of lignin residue. Besides pennisetum, the ZrP combined with Ru/C catalyst was generally efficient for conversion of other typical agricultural waste and energy plant. During reusability over this combined solid catalyst, the activity loss was observed due to P leaching in ZrP, but it can be recovered by re-calcination. The synergistic effect of acidic ZrP (cellulose/hemicellulose hydrolysis of raw biomass) and 22


Page 22 of 44

Page 23 of 44

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


metallic Ru/C (fast hydrogenation of the 23ingo23me2323 C5 and C6 sugar intermediates) was responsible for the high sugar alcohols yield by suppressing side products of dehydration and hydrogenolysis.

Supporting information XRD patterns, composition and inorganic element analysis of different lignocellulosic biomass, Photograph after cellulose transformation over ZrP and Ru/C catalyst, XRD and NH3-TPD analyses of Ru/ZrP, and EDS spectra of fresh and hydrothermally treated ZrP.

Author information Corresponding author

*E-mail:

[email protected].

Tel:

86-20-37029721;

Fax:

86-20-87057789;

[email protected]. Tel: 86-20-87057673; Fax: 86-20-87057673.

Notes The authors declare no competing financial interest.

Acknowledgements This work was financially supported by the National Natural Science Foundation of China (51376185, 51536009 and 51576199).

References (1) Zhang, S.; Maréchal, F.; Gassner, M. Process 23ingo23me23 and integration of fuel ethanol production from lignocellulosic biomass based on double acid hydrolysis. Energy Fuel. 2009, 23, 1759-1765. (2) Scholz, D.; Aellig, C.; Mondelli, C.; Perez-Ramirez, J. Continuous transfer hydrogenation of sugars to alditols with bioderived donors over Cu-Ni-Al catalysts. ChemCatChem 2015, 7, 23



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

1551-1558. (3) Palkovits, R.; Tajvidi, K.; Procelewska, J. Hydrogenolysis of cellulose combining mineral acids and hydrogenation catalysts. Green Chem. 2010, 12, 972-978. (4) Polykarpos, A. L.; Stamatia, K.; Andreas, D.; Simona, M. C.; Vasile, I. P.; Kostas, S. T. d-Glucose hydrogenation/hydrogenolysis reactions on noble metal (Ru, Pt)/activated carbon supported catalysts. Catal. Today 2015, 257, 281-290. (5) Negahdar, L.; Oltmanns, J. U.; Palkovits, S.; Palkovits, R. Kinetic investigation of the catalytic conversion of cellobiose to sorbitol. Appl. Catal. B 2014, 147, 677-683. (6) Liu, X. R.; Wang, X. C.; Yao, S. X.; Jiang, Y. J.; Guan, J.; Mu, X. D. Recent advances in the production of polyols from lignocellulosic biomass and biomass-derived compounds. RSC Adv. 2014, 4, 49501-49520. (7) Kobayashi, H.; Ito, Y.; Komanoya, T. Synthesis of sugar alcohols by hydrolytic hydrogenation of cellulose over supported metal catalysts. Green Chem. 2011, 13, 326-333. (8) Wang, D.; Niu, W. Q.; Tan, M. H.; Wu, M. B.; Zheng, X. J.; Li, Y. P.; Tsubaki, N. Pt nanocatalysts supported on reduced 24ingo24me oxide for selective conversion of cellulose or cellobiose to sorbitol. ChemSusChem 2014, 7, 1398-1406. (9) Fukuoka, A.; Dhepe, P. L. Catalytic conversion of cellulose into sugar alcohols. Angew. Chem. Int. Ed. 2006, 45, 5161-5163. (10) Geboers, J.; Van de Vyver, S.; Carpentier, K.; Jacobs, P.; Sels, B. F. Efficient hydrolytic hydrogenation of cellulose in the presence of Ru-loaded zeolites and trace amounts of mineral acid. Chem. Commun. 2011, 47, 5590-5592. (11) Geboers, J.; Van de Vyver, S.; Carpentier, K.; de Blochouse, K.; acobs, P.; Sels, B. F. Efficient 24


Page 24 of 44

Page 25 of 44

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


catalytic conversion of concentrated cellulose feeds to hexitols with heteropoly acids and Ru on carbon. Chem. Commun. 2010, 46, 3577-3579. (12) Palkovits, R.; Tajvidi, K.; Ruppert, A. M.; Procelewska, J. Heteropoly acids as efficient acid catalysts in the one-step conversion of cellulose to sugar alcohols. Chem. Commun. 2011, 47, 576-578. (13) Palkovits, R.; Tajvidi, K.; Procelewska, J.; Rinaldi, R.; Ruppert, A. Hydrogenolysis of cellulose combining mineral acids and hydrogenation catalysts. Green Chem. 2010, 12, 972-978. (14) Hilgert, J.; Meine, N.; Rinaldi, R.; Schüth, F. Mechanocatalytic depolymerization of cellulose combined with hydrogenolysis as a highly efficient pathway to sugar alcohols. Energy Environ. Sci. 2013, 6, 92-96. (15) Deng, T.; Liu, H. Promoting effect of SnOx on selective conversion of cellulose to polyols over bimetallic Pt-SnOx/Al2O3 catalysts. Green Chem. 2013, 15, 116-124. (16) Negoi, A.; Triantafyllidis, K.; Parvulescu, V. I.; Coman, S. M. The hydrolytic hydrogenation of cellulose to sorbitol over M (Ru, Ir, Pd, Rh)-BEA-zeolite catalysts. Catal. Today 2014, 223, 122-128. (17) Ennaert, T.; Geboers, J.; Gobechiya, E.; Courtin, C. M.; Kurttepeli, M.; Houthoofd, K.; Kirschhock, C. E.A.; Magusin, P. C. M. M.; Bals, S.; Jacobs, P. A.; Sels, B. F. Conceptual frame rationalizing the self-stabilization of H‑USY zeolites in hot liquid water. ACS Catal. 2015, 5, 754-768. (18) Ennaert, T.; de Beeck, B. O.; Vanneste, J.; Smit, A. T.; Huijgen, W. J. J.; Vanhulsel, A.; Jacobs, P. A.; Sels, B. F. The importance of pretreatment and feedstock purity in the reductive splitting 25



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

of (26ingo)cellulose by metal supported USY zeolite. Green Chem. 2016, 18, 2095-3105. (19) Jolle, V.; Chambon, F.; Rataboul, F.; Cabiac, A.; Pinel, C.; Guillon, E.; Essayem, N. Non-catalyzed and Pt/gamma-Al2O3-catalyzed hydrothermal cellulose dissolution-conversion: influence of the reaction parameters and analysis of the unreacted cellulose. Green Chem. 2009, 11, 2052-2060. (20) Liang, G.; Cheng, H. Y.; Li, W.; He, L. M.; Yu, Y. C.; Zhao, F. Y. Selective conversion of microcrystalline cellulose into hexitols on nickel particles encapsulated within ZSM-5 zeolite. Green Chem. 2012, 14, 2146-2149. (21) Van de Vyver, S.; Geboers, J.; Schutyser, W.; Dusselier, M.; Eloy, P.; Dornez, E.; Seo, J. W.; Courtin, C. M.; Gaigneaux, E. M.; Jacobs, P. A.; Sels, B. F. Tuning the acid/metal balance of carbon nanofiber-supported nickel catalysts for hydrolytic hydrogenation of cellulose. ChemSusChem 2012, 5, 1549-1558. (22) Pang, F. J.; Wang, A. Q.; Zheng, M. Y.; Zhang, Y. H.; Huang, Y. Q.; Chen, X. W.; Zhang, T. Catalytic conversion of cellulose to hexitols with mesoporous carbon supported Ni-based bimetallic catalysts, Green Chem. 2012, 14, 614-617. (23) Kobayashi, H.; Kaiki, H.; Shrotri, A.; Techikawara, K.; Fukuoka, A. Hydrolysis of woody biomass by a biomass-derived reusable heterogeneous catalyst. Chem. Sci. 2016, 7, 692-696. (24) Yi, G. S.; Zhang, Y. G. One-pot selective conversion of hemicellulose (xylan) to xylitol under mild conditions. ChemSusChem 2012, 5, 1383-1387. (25) Ennaert, T.; Feys, S.; Hendrikx, D.; Jacobs, P. A.; Sels, B. F. Reductive splitting of hemicellulose with stable ruthenium-loaded USY zeolites. Green Chem. 2016, 18, 5295-5304. (26) Park, D. S.; Yun, D.; Kim, T. Y.; Baek, J.; Yun, Y. S.; Yi, J. A mesoporous carbon-supported Pt 26


Page 26 of 44

Page 27 of 44

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


nanocatalyst for the conversion of lignocellulose to sugar alcohols. ChemSusChem 2013, 6, 2281-2289. (27) Yamaguchi, A.; Sato, O.; Mimura, N.; Hirosaki, Y.; Kobayashi, H.; Fukuoka, A.; Shirai, M. Direct production of sugar alcohols from wood chips using supported platinum catalysts in water. Catal. Commun. 2014, 54, 22-26. (28) Tathod, A. P.; Dhepe, P. L. Efficient method for the conversion of agricultural waste into sugar alcohols over supported bimetallic catalysts. Bioresour. Technol. 2015, 178, 36-44. (29) Guha, S. K.; Kobayashi, H.; Hara, K.; Kikuchi, H.; Aritsuka, T.; Fukuoka, A. Hydrogenolysis of sugar beet fiber by supported metal catalyst. Catal. Commun. 2011, 12, 980-983. (30) Van den Bosch, S.; Schutyser, W.; Vanholme, R.; Driessen, T.; Koelewijn, S. F.; Renders, T.; De Meester, B.; Huijgen, W. J. J.; Dehaen, W.; Courtin, C. M.; Lagrain, B.; Boerjanbc, W.; Sels, B. F. Reductive lignocellulose fractionation into soluble lignin-derived phenolic monomers and dimers and processable carbohydrate pulps. Energy Environ. Sci. 2015, 8, 1748-1763. (31) Li, C. Z.; Zheng, M. Y.; Zhang, A.; Zhang, Q. T. One-pot catalytic hydrocracking of raw woody biomass into chemicals over supported carbide catalysts: Simultaneous conversion of cellulose, hemicellulose and lignin. Energy Environ. Sci. 2012, 5, 6383-6390. (32) Asghari, F. S.; Yoshida, H. Dehydration of fructose to 5-hydroxymethylfurfural in sub-critical water over heterogeneous zirconium phosphate catalysts. Carbohydr. Res. 2006, 341, 2379− 2387. (33) Ordomsky, V. V.; van der Schaaf, J.; Schouten, J. C.; Nijhuis, T. A. Fructose dehydration to 5-hydroxymethylfurfural over solid acid catalysts in a biphasic system. ChemSusChem 2012, 27



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

5, 1812−1819. (34) Liao, Y. H.; Liu, Q. Y.; Wang, T. J.; Long, J. X.; Ma, L. L.; Zhang, Q. Zirconium phosphate combined with Ru/C as a highly efficient catalyst for the direct transformation of cellulose to C6 alditols. Green Chem. 2014, 16, 3305-3312. (35) Liao, Y. H.; Liu, Q. Y.; Wang, T. J.; Long, J. X.; Zhang, Q.; Ma, L. L.; Liu, Y.; Li, Y. P. Promoting hydrolytic hydrogenation of cellulose to sugar alcohols by mixed ball milling of cellulose and solid acid catalyst. Energy Fuel. 2014, 28, 5778-5784. (36) Zhang, X. H.; Zhang, Q.; Wang, T. J.; Ma, L. L.; Yu, Y. X. Hydrodeoxygenation of lignin-derived phenolic compounds to hydrocarbons over Ni/SiO2-ZrO2 catalysts. Bioresour. Technol. 2013, 134, 73-80. (37) Sluiter, J. B.; Ruiz, R. O.; Scarlata, C. J.; Sluiter, A. D.; Templeton, D. W. Compositional analysis of lignocellulosic feedstocks. 1. Review and description of methods, J. Agric. Food Chem. 2010, 58, 9043-9053. (38) Lv, S. L.; Yu, Q.; Zhuang, X. S.; Yuan, Z. H.; Wang, W.; Wang, Q.; Qi, W.; Tan, X. S. The influence of hemicellulose and lignin removal on the enzymatic digestibility from sugarcane bagasse. Bioenerg. Res. 2013, 6, 1128-1134. (39) Liu, S. B.; Okuyama, Y.; Tamura, M.; Nakagawa, Y.; Imai, A.; Tomishige, K. Selective transformation of hemicellulose (xylan) into n-pentane, pentanols or xylitol over a rhenium-modified iridium catalyst combined with acids, Green Chem. 2016, 18, 165-175. (40) Amada, Y.; Watanabe, H.; Hirai, Y.; Kajikawa, Y.; Nakagawa, Y.; Tomishige K. Production of biobutanediols by the hydrogenolysis of erythritol. ChemSusChem 2012, 5, 1991-1999. (41) Ji, N.; Zheng, M. Y.; Wang, A. Q.; Zhang, T.; Chen, J. G. G. Nickel-promoted tungsten 28


Page 28 of 44

Page 29 of 44

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


carbide catalysts for cellulose conversion: Effect of preparation methods. ChemSusChem 2012, 5, 939-944. (42) El Hage, R.; Brosse, N.; Navarrete, P.; Pizzi, A. Extraction, characterization and utilization of organosolv miscanthus lignin for the conception of environmentally friendly mixed tannin/lignin wood resins. J. Adhesion Sci. Technol. 2011, 25, 1549-1560. (43) Rose, M.; Palkovits, R. Isosorbide as a renewable platform chemical for versatile applicationsuQuo Vadis? ChemSusChem 2012, 5, 167-176. (44) Murzin, D. Y.; Murzina, E. V.; Tokarev, A.; Shcherban, N. D.; Wärnå, J.; Salmi, T.; Arabinogalactan hydrolysis and hydrolytic hydrogenation using functionalized carbon materials. Catal. Today 2015, 257, 169-176. (45) Dzyazko, Y. S.; Trachevskii, V. V.; Rozhdestvenskaya, L. M.; Vasilyuk, S. L.; Belyakov, V. N. Interaction of sorbed Ni(II) ions with amorphous zirconium hydrogen phosphate. Russ. J. Phys. Chem. A 2013, 87, 840−845. (46) Ordomsky, V. V.; Sushkevich, V. L.; Schouten, J. C.; van der Schaaf, J.; Nijhuis, T. A. Glucose dehydration to 5-hydroxymethylfurfural over phosphate catalysts. J. Catal. 2013, 300, 37−46. (47) Liu, Q. Y.; Liao, Y. H.; Wang, T. J.; Cai, C. L.; Zhang, Q.; Tsubaki, N.; Ma, L. L. One-pot transformation of cellulose to sugar alcohols over acidic metal phosphates combined with Ru/C. Ind. Eng. Chem. Res. 2014, 53, 12655−12664. (48) Sun, Z. G.; Liu, Z. M.; Xu, L.; Yang, Y.; He, Y. L. Hydrothermal synthesis and characterization of microporous crystals of trivalent metal-containing zirconium phosphates. Catal. Today 2004, 93-95, 639-643. (49) Sinhamahapatra, A.; Sutradhar, N.; Roy, B.; Pal, P.; Bajaj, H. C.; Panda, A. B. Microwave 29



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

assisted synthesis of fine chemicals in solvent-free conditions over mesoporous zirconium phosphate. Appl. Catal. B 2011, 103, 378-387.

30


Page 30 of 44

Page 31 of 44

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


Table and Figure captions Table 1 Conversion of pennisetum to sugar alcohols by different solid acids combined with Ru/C Table 2 The textural property and acid density of solid acid catalysts Figure 1 SEM image (A) and FT-IR spectrum (B) of lignin residue originated from pennisetum transformation Figure 2 Influence of molar acid/metal ratios on sugar alcohols yield in hydrolytic hydrogenation of pennisetum Figure 3 Processing parameters including reaction temperature (A), reaction time (B), reaction pressure (C) and biomass concentration (D) in conversion of pennisetum to sugar alcohols Figure 4 The physicochemical properties of fresh ZrP: (A) XRD pattern, (B) TEM image, (C) NH3-TPD profile and (D) pyridine absorbed FT-IR spectra (a, pristine ZrP and b, hydrothermally pretreated ZrP followed by recalcination) Figure 5 Properties of fresh commercial Ru/C: XRD pattern (A) and TEM image (B) Figure 6 Comparative experiments by using xylose, glucose and microcrystalline cellulose as the feedstock Figure 7 Test of catalytic stability in pennisetum conversion to sugar alcohols Figure 8 XRD pattern (A), TG curves (B), TEM images (C) and NH3-TPD profile of hydrothermally treated ZrP Figure 9 XRD pattern (A) and TEM image (B) of hydrothermally treated Ru/C Table 3 Conversion of diversified biomass to sugar alcohols over ZrP combined with Ru/C

31



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 44

Table 1 Conversion of pennisetum to sugar alcohols by different solid acids combined with Ru/C a Product yield (C-mol%) Conv. Solid acid (%) C6 SG C5 SG C6 SA C5 SA ERY GLY PD EG -b

7.9

2.0

6.1

-

-

-

-

-

-

ZrO2

16.8

1.9

-

3.3

9.6

0.2

0.5

0.3

0.1

SiO2-ZrO2

35.6

1.7

-

15.8

16.7

1.4

0.9

0.1

-

WO3/ZrO2

36.8

1.1

-

11.6

8.3

6.0

6.7

3.8

1.2

SO4 /ZrO2

48.8

3.0

-

22.5

25.4

3.2

1.2

2.3

0.3

ZrP

54.3

5.1

-

34.6

26.2

5.8

1.8

1.0

-

42.7

6.4

-

28.1

24.4

7.7

3.6

2.5

-

20.3

2.2

-

5.8

7.0

0.5

0.3

-

-

39.9

7.3

7.8

0.6

1.0

-

-

-

-

2-

Ru/ZrP

c

Ru/C Single ZrP a

d

Reaction conditions: 473 K, 6 Mpa of initial H2 pressure (room temperature), 2.5 h, pennisetum

1 g, H2O 50 ml, solid acid 0.5 g, Ru/C 0.1 g. b

No catalyst was introduced.

c

Catalyst loading 0.5 g.

d

The sole ZrP was introduced without Ru/C.

C6 SG: C6 sugar, C5 SG: C5 sugar, C6 SA: C6 sugar alcohol, C5 SA: C5 sugar alcohol, ERY: erythritol, GLY: glycerol, PD: 1,2-propanediol, EG: ethylene glycol.

32


Page 33 of 44

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


Table 2 The textural property and acid density of solid acid catalysts

Entry

Catalyst

Surface area a (m2/g)

Pore volume b (cm3/g)

Average pore diameter b (nm)

Acidic density c (mmol/g)

Dd

1

ZrO2

20.8

0.04

27.5

0.12

-

2

Spent ZrO2 e

23.2

0.05

30.0

0.10

-

3

SiO2-ZrO2

233.1

0.96

7.9

0.62

-

4

Spent SiO2-ZrO2 e

211.1

0.80

8.6

0.55

5

WO3/ZrO2

17.3

0.07

21.1

0.44

6

Spent WO3/ZrO2 e

19.9

0.06

23.8

0.29

a

b

7

SO42-/ZrO2

21.5

0.12

24.7

1.19

8

Spent SO42-/ZrO2 e

18.0

0.10

26.1

0.67

-

-

-

9

ZrP

126.7

0.31

4.8

1.75

-

10

Spent ZrP e

107.0

0.27

5.6

1.71

-

11

Ru/C

1125.4

0.28

3.8

-

0.51

12

Spent Ru/C e

982.1

0.25

4.3

-

0.39

13

Ru/ZrP

104.1

0.27

5.1

1.10

0.19

14

Spent Ru/ZrP e

87.2

0.22

6.1

0.90

0.13

The surface area was estimated by BET method using N2 at 77 K. The volume and average pore diameter indicate the mesoporous ones determined by using

desorption branch and BJH method. c

The acidic amount was calculated by NH3-TPD measurement and a calibration loop of 250 µl.

d

The dispersion of Ru by H2-chemisorption. Due to the Ru/C was hardly isolated from ZrP after

reaction, the spent Ru/C indicated that the fresh Ru/C was hydrothermally treated to simulate the

33



reaction at the condition in Table 1. e

The spent solid acids after hydrothermal treatment was conducted at 473 K for 2.5 h, followed by

drying and recalcination at the same temperature as to the preparation for the respective fresh ones. The spent Ru/C after hydrothermally treatment was dried and calcined at 623 K under N2 flow.

80

B

70 Transmittanse (a.u.)

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 44

60 50 2930 1110 1705 1512 1211 1609

40 3410

30 20 4000

3500

3000

2500

2000

1500

1000

500

-1

Wavenumber (cm )

Figure 1 SEM image (A) and FT-IR spectrum (B) of lignin residue originated from pennisetum transformation. The inset in (A) presented the pristine pennisetum.

34


Page 35 of 44

40 C6 SA

35

C5 & C6 SA yield (C-mol %)

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


30 25 C5 SA

20 15 10 5 0 0

5

10

15

20

25

30

35

40

45

50

55

nAcid/nRu

Figure 2 Influence of molar acid/metal ratios on sugar alcohols yield in hydrolytic hydrogenation of pennisetum. The molar ratio was determined by fixing Ru/C while changing ZrP. Reaction conditions: 473 K, 6 MPa of initial H2 pressure (room temperature), 2.5 h, pennisetum 1 g, H2O 50 ml.

35



100

90

70

80 70

60

60

50 50

40

40

30 20

30

10

20

0

Conversion & Yield (C-mol%)

70

80

Conversion (C-mol%)

Yield (C-mol%)

80

100 (A)

C6 sugar C5 sugar C6 sugar alcohol C5 sugar alcohol isosorbide C2-C4 byproduct

90

450

460

470

480

60 50 40 30 20 10

0

490

1

2

3

4

5

(D)

60


(C)

50 40 30 conversion C6 sugar C6 sugar alcohol C5 sugar alcohol C2-C4 byproduct

20 10 0 4

5

6

6

Time (h)

Temperature (K) 60

(B)

Conversion C6 sugar C5 sugar C6 sugar alcohol C5 sugar alcohol C2-C4 byproduct

0

10 440


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 44

7

conversion C6 sugar C5 sugar C6 sugar alcohol C5 sugar alcohol C2-C4 byproduct

50 40 30 20 10 0 0

8

2

4

6

8

10

pennisetum concentration (wt%)

Pressure (MPa)

Figure 3 Processing parameters including reaction temperature (A), reaction time (B), reaction pressure (C) and biomass concentration (D) in conversion of pennisetum to sugar alcohols. The reaction condition is the same to Table 1 apart from the individually varied parameter tested. For (B) the reaction temperature was 458 K and for (D) the concentration of 1%, 2%, 5% and 10% mean 0.5 g, 1 g, 2.5 g and 5 g pennisetum were introduced in 50 ml H2O, respectively.

36


Page 37 of 44

Intensity (a.u.)

A

10

20

30

40

50

60

70

80

2-Theta (degree)

C

Absorbency (a.u.)

D

Intensity (a.u.)

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


(a)

(b)

400

500

600

700

800

900

1000

1100

1700

1650

1600

1550

1500

1450

1400

-1

Temperature (K)

Wave number (cm )

Figure 4 The physicochemical properties of fresh ZrP: (A) XRD pattern, (B) TEM image, (C) NH3-TPD profile and (D) pyridine absorbed FT-IR spectra (a, pristine ZrP and b, hydrothermally pretreated ZrP followed by recalcination).

37



A

Intensity (a.u.)

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

20

30

40

50

60

70

80

2-Theta (degree)

Figure 5 Properties of fresh commercial Ru/C: XRD pattern (A) and TEM image (B).

38


Page 38 of 44

Page 39 of 44

conversion xylitol sorbitol glucose C2-C4 byproduct

100


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


80

60

40

20

0 x y

xyl los ose e-0 -1h .5h

glu

cos e

glu -0. 5h

cos e

-1h

cel lu

los e

-2. 5h

Figure 6 Comparative experiments by using xylose, glucose and microcrystalline cellulose as the feedstock. Reaction condition: feedstock 1 g, ZrP 0.5 g, Ru/C 0.1 g, H2O 50 ml, temperature 473 K, initial H2 pressure 6 MPa, reaction time 0.5 h and 1 h for xylose/glucose and 2.5 h for cellulose.

39



60 conversion C6 sugar alcohol C5 sugar alcohol

50 Conversion & Yield (C-mol%)

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

40 30 20 10 0 1

2

3

4

5

Catalyst stability test

Figure 7 Test of catalytic stability in pennisetum conversion to sugar alcohols. X-axis “1-3” indicates the catalyst stability by ZrP and Ru/C directly using in the next run; X-axis “4” indicates the fresh Ru/C combined with the re-calcined ZrP by hydrothermal treatment; X-axis “5” indicates the fresh ZrP combined with hydrothermally treated Ru/C. Reaction condition: 473 K, 6 MPa of initial H2 pressure (room temperature), 2.5 h, pennisetum 1 g, H2O 50 ml, ZrP 0.5 g, Ru/C 0.1 g.

40


Page 40 of 44

Page 41 of 44

1.02

A

B

1.00 0.98

Weight loss (%)

Intensity (a.u.)

0.96 0.94 0.92

fresh ZrP

0.90 0.88

hydrothermally treated ZrP

10

20

30

40

50

2-Theta (degree)

60

70

80

0.86 300

400

500

600

700

800

900

1000

Temperature (K)

D

Intensity (a.u.)

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


400

500

600

700

800

900

1000

1100

Temperature (K)

Figure 8 XRD pattern (A), TG curves (B), TEM images (C) and NH3-TPD profile of hydrothermally treated ZrP.

41



A Intensity (a.u.)

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

20

30

40

50

60

70

80

2-Theta (degree)

Figure 9 XRD pattern (A) and TEM image (B) of hydrothermally treated Ru/C.

42


Page 42 of 44

Page 43 of 44

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


Table 3 Conversion of diversified biomass to sugar alcohols over ZrP combined with Ru/C Yield (C-mol%) Conv. Biomass a (%) C6 SG C6 SA C5 SA a ERY GLY PD EG Sugarcane

57.5

6.9

Switchgrass

55.6

10.3

Corncob

57.9

8.1

Cornstalk

50.8

10.0

bagasse

25.3

26.6

(85.0%)

(90.1%)

18.8

14.2

(81.2%)

(88.0%)

14.6

15.3

(79.9%)

(86.8%)

17.5

18.5

(83.7%)

(87.9%)

6.1

1.5

1.3

0.5

1.4

1.1

2.3

0.5

3.0

3.7

1.8

0.6

3.7

0.2

2.3

0.6

Reaction conditions: 473 K, 6 MPa of initial H2 pressure (room temperature), 2.5 h, biomass 1 g, H2O 50 ml, ZrP 0.5 g, Ru/C 0.1 g. C6 SG: C6 sugar, C6 SA: C6 sugar alcohol, C5 SA: C5 sugar alcohol, ERY: erythritol, GLY: glycerol, PD: 1,2-propanediol, EG: ethylene glycol. a

The data in the parenthesis means the sorbitol and xylitol percentage in total C6 and C5 sugar

alcohols, respectively.

43



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

Table of content: ZrP and Ru/C are highly efficient to produce C5/C6 sugar alcohols from raw biomass for getting the yield of 70% at 2.5 h.

Figure 1 of 9

44


Page 44 of 44

C6 Sugar Alcohols by Hydrolytic Hydrogenation of

Recommend Documents