•Enthalpies during the active pyrolysis of chitin and chitosan were revealed by DSC.•Potentials of chitin and chitosan to organonitrogen chemicals were evaluated by Py-GC/MS.•Selectivity of pyrazine compounds from chitosan pyrolysis was up to 22.99%.•Selectivity of acetamido acetaldehyde from chitin pyrolysis was up to 27.27%.Thermogravimetric characteristics of chitin and chitosan and their potentials to produce value-added organonitrogen chemicals were separately evaluated via TG/DSC-FTIR and Py-GC/MS. Results shown that chitin had the better thermal stability and higher activation energy than chitosan because of the abundant acetamido group. Furthermore, the dominated volatilization in active pyrolysis of chitin contributed to its endothermic property, whereas the charring in chitosan led to the exothermal. During fast pyrolysis, the acetamido group in chitin and chitosan was converted into acetic acid or acetamide. Typical products from chitosan pyrolysis were aza-heterocyclic chemicals, i.e. pyridines, pyrazines, and pyrroles, with the total selectivity of 50.50% at 600 °C. Herein, selectivity of pyrazine compounds was up to 22.99%. These aza-heterocyclic chemicals came from the nucleophilic addition reaction of primary amine and carbonyl. However, main reaction during chitin pyrolysis was ring-opening degradation, which led to the formation of acetamido chemicals, especially acetamido acetaldehyde with the highest selectivity of 27.27% at 450 °C. In summary, chitosan had the potential to produce aza-heterocyclic chemicals, and chitin to acetamido chemicals.

•Four typical β-O-4 lignin dimers with different side-chain structures were synthesized.•Cα–OH, Cα = O and Cγ–OH groups greatly affected the hydrothermolysis of lignin dimers.•New dimers were formed via the intramolecular elimination reactions•New dimers further affected on the products distribution and selectivity.•The reaction pathways for the hydrothermolysis of β-O-4 lignin dimers were proposed.Hydrothermal-controlled selective cleavage of CβO and CαCβ bonds was well realized via modification the side-chain structure of lignin. To elucidate the reaction pathway and the origin of selectivity, the sites of the benzylic alcohol (Cα–OH) and benzylic ketone (CαO) on the cleavage mechanisms of βO4 lignin dimers were investigated. Results clearly demonstrated the hydrothermolysis process could be divided into three stages: (1) intramolecular elimination reactions, (2) the cleavage of CαCβ or CβO bonds and (3) secondary reactions of intermediates. Reaction pathways were highly susceptible to the side-chain structure. The CαCβ and CβO bonds of 1-(4-hydroxy-3-methoxyphenyl)-2-(2-methoxyphenoxy)-ethanone tended to directly cleave and form aromatic monomers. However, many different species dimers were produced via the intramolecular elimination reactions when the hydroxyl group was introduced at the Cα or Cγ position, which participated in a variety of reaction mechanisms, resulting in more complex products distribution. In addition, the results also indicated that dehydration of Cα-OH group significantly facilitated the cleavage of CβO bonds, but oxidation of the Cα-OH into Cα = O group weakened the CαCβ bond. Based on the compositions and structures of products, several cleavage pathways of dimers were proposed, explaining well the origin of selectivity.Download high-res image (116KB)Download full-size image

•Side-chain structures affect H-, G- and S secondary pyrolysis routes.•Aryl-CHO group removal is the major side-chain-conversion for aldehydes.•Adding the amount of aryl-OCH3 promotes removal of aryl-CHO group.•Reaction pathways for secondary pyrolysis routes are proposed.Thermal reactions of six monomeric aromatics (typical primary pyrolytic products of β-O-4 lignin dimers) were studied in a closed ampoule reactor (N2/400–600 °C/120 s) to obtain the information on secondary pyrolysis pathway of products. The result showed that the secondary pyrolysis of monomeric aromatics mainly included two pathways: polymerization and side-chain-conversion, and the polymerization were more competitive under all the test conditions. The amount of -OCH3 group was an essential factor on the reactivity of monomeric aromatics, and the introduction of -OCH3 group enhanced the conversion of monomeric aromatics. In the presence of -CHO group on the p-position of aryl-OH, the removal of -CHO group was major side-chain-conversion reaction during the pyrolysis process. Adding the amount of -OCH3 group was beneficial for promotion the breakage of aryl-CHO bond; instead, when the p-position of phenolic hydroxyl group was -COCH3 group, the cleavage of aryl-COCH3 bond was inhibited, where radical induced rearrangement of aryl-OCH3 group into aryl-CH3 group firstly happened and as the major side-chain-conversion reaction. Besides, new reactant intermediates, which were directly formed via side-chain-conversion of initial samples, could further decompose to other aromatic monomers, and influenced the products distribution and selectivity via a series of reactions.

•A simple and effective ZnCl2 hydrate pretreatment was developed in this study.•ZnCl2 hydrate pretreatment generated highly digestible pretreated solid.•BSA additive showed great potential for reducing cellulase dosage.•High yield sugar was obtained after pretreatment and enzymatic hydrolysis.Enhancement of eucalyptus enzymatic saccharification by synergy of ZnCl2 hydrate pretreatment and bovine serum albumin (BSA) was investigated in this study. The result showed that the ZnCl2 hydrate pretreatment could not only selectively extract up to ∼100% of the hemicellulose from eucalyptus, but also convert portion of high crystalline cellulose I into low crystalline cellulose II, which both beneficial for enhancing subsequent pretreated solids enzymatic saccharification. The addition of BSA into enzymatic hydrolysis step could significantly promote the glucose release from pretreated solids, especially, under the low enzyme loading. Furthermore, the material balance indicated that the highest glucose yield of this study was 35.5 g/100 g raw material, which representing 90.3% of glucose in raw eucalyptus, combined with the xylose yield, 13.9 g/100 g eucalyptus, it can be concluded that ZnCl2 hydrate pretreatment offered the potential to co-produce xylose and glucose from eucalyptus.Download high-res image (70KB)Download full-size image

This study explored the direct conversion of black liquor acid sediment (BLAS) into phenolics by hydrothermolysis. Experiments were successfully performed in a batch-type reactor at temperature of 260 to ∼340 °C over 0–120 min. Depending on the reaction conditions, four products (bio-oil phase containing most of the phenolics, aqueous phase, char, and a small amount of gas) were formed and analyzed by element analysis, Fourier transform infrared spectroscopy (FT-IR), gas chromatography mass spectrometry (GC-MS), gas chromatography (GC), and pyrolysis-gas chromatography mass spectrometry (Py-GC/MS). The total bio-oil yield was 16–26 wt % based on dry BLAS (D-BLAS), in which the main monomeric compounds were 2-methoxyphenol, 2, 6-dimethoxyphenol, and catechol, with yields of 0.74–1.66, 0.28–4.03, and 0–7.08 wt % based on lignin in the BLAS (BLAS-L), respectively. Analysis of char suggested BLAS-L occurred by hydrothermolytic depolymerization to give aryl-ether linkages (β-O-4 and α-O-4 bonds), hydroxyl and carbonyl groups, and aromatic rings. Finally, the reactions were almost complete because the char had no functional groups of lignin at the optimal reaction condition (300 °C and 30 min).

Conversion of eucalyptus cellulose into 5-hydroxymethylfurfural (5-HMF) by using Lewis acid catalyst in biphasic system was investigated in this study. The results show that the tetrahydrofuran/water biphasic system was more conducive to convert the eucalyptus cellulose into 5-HMF comparing to the single aqueous system. InCl3, a water-compatible Lewis acid, has the best catalytic effect. The highest yield of 5-HMF from eucalyptus cellulose is up to 45.05 mol%, which is a slight higher than that from microcrystalline cellulose. It can be ascribed to the lower crystallinity of isolated eucalyptus cellulose. The optimum conditions for catalytic conversion of eucalyptus cellulose into 5-HMF are at 200 °C for 2 h with 10 % InCl3 dosage. Additionally, the effect of recycling the whole biphasic system which contains InCl3, NaCl, H2O and THF indicated that the 5-HMF yield was gradually decreased as the cycle times increased, the possible reason could be due to the loss of partial InCl3 catalyst during the separation and distillation process.

AbstractBACKGROUNDBagasse, a kind of agricultural residue having high sugar content, has been considered a promising feedstock to produce bio-ethanol. However, the natural structure of bagasse makes it difficult to use this material to produce bio-ethanol directly. Efficient pretreatment is necessary to break down the natural sealed structure of bagasse and sequential enzymatic hydrolysis can release maximum sugars.RESULTSIn order to enhance sugar recovery from bagasse, ethanol-based organosolv auto-catalyzed pretreatment followed by enzyme hydrolysis was investigated in this study. The maximum xylose recovery from the prehydrolysate was 10.31 g per 100 g bagasse, and among them 78.08% existed in the form of xylo-oligosaccharides. The highest glucose recovery in the enzymatic hydrolysate was 40.29 g per 100 g bagasse, representing 92.20% of glucose in the bagasse material. In terms of total sugars (combined xylose and glucose both in prehydrolysate and enzymatic hydrolysate), 56.98 g per 100 g bagasse, representing 83.67% of the total sugars in the bagasse biomass were obtained at 195 °C for 30 min with 40% ethanol. Corresponding concentrations of 5-HMF, and furfural in the prehydrolysate were only 0.32 and 0.97 g L−1, respectively, which indicated that detoxification may not be required in the next fermentation step. Besides the sugars, about 84.27% of lignin in the bagasse material can also be recovered in the form of ethanol–lignin or enzymatic hydrolysis lignin.CONCLUSIONSEthanol-based organosolv auto-catalyzed pretreatment could enhance the enzymatic digestibility of bagasse due to the removal of hemicelluloses and lignin, to finally realize high sugar recovery from bagasse. © 2016 Society of Chemical Industry

Although o-quinonemethide (6-methylene-2,4-cyclohexadien-1-one) has been proposed as a key intermediate in char formation during the pyrolysis of guaiacol (2-methoxyphenol), direct evidence of this (e.g., spectroscopic data) has not yet been provided. Using in situ FTIR spectroscopy, the pyrolysis of guaiacol was investigated from 30 °C to 630 °C at 40 °C/min. The IR profiles showed direct evidence of o-quinonemethide production at about 350 °C, which vanished rapidly at around 420 °C in the vapor phase, indicating char formation. In addition, at 400 °C, salicyl aldehyde was observed, which decomposed slowly at about 500 °C. In combination with the known products of guaiacol pyrolysis, these results allowed the major reaction pathways of guaiacol pyrolysis to be discerned. Density functional theory calculations were performed, and the results were found to be in good agreement with the experimentally obtained IR profiles. These findings provide guidance on how to suppress secondary reactions of guaiacol during lignin pyrolysis.

•H3PO4 and CrCl3 are coupled as a mixed catalyst and used for glucose conversion.•Synergistic catalytic effect is observed in mixed H3PO4–CrCl3 catalyst system.•A kinetic model was developed to describe glucose conversion and LA formation.•Activation energies derived from current model are obvious lower than previous study.Conversion the glucose to levulinic acid (LA) using various homogeneous Brønsted acids or Lewis acids in a batch reactor has been investigated in this study. The results show that coupling of CrCl3 and H3PO4 as a mixed catalyst has a positive synergistic catalytic effect on glucose conversion to LA compared with single CrCl3 or H3PO4 catalyst. Both the reaction time and temperature have strong effect on glucose conversion and LA formation, the highest LA yield of 54.24% was obtained from 100% glucose conversion at 170 °C for 240 min. Furthermore, a simplified kinetic model was developed to describe the behavior of glucose conversion and LA formation based on the pseudo homogeneous first-order model, and the results show that this model is in good agreement with the experiment data. The reaction rate constants for glucose decomposition, hydroxymethylfurfural (HMF) conversion, and LA formation are all increased with elevated temperature, the activation energies for glucose dehydration into HMF and HMF rehydration to LA were 65.4 and 60.6 kJ/mol, respectively, significantly lower than previous reports in the measure of single homogeneous Brønsted acid or Lewis acids.

•The effect of different substituents on pyrolytic β-ether cleavage was studied.•The yields of guaiacol and 2-methoxy-benzaldehyde reflected the degree of cleavage of the CβO and CαCβ bond.•Oxidation of the CαOH group to CαO facilitated cleavage of the CαCβ bond.•New dimers were found and further affected products’ distribution and selectivity.The cleavage of intermolecular linkages in lignin is a crucial yet complicated factor to properly deconvolute during the pyrolysis of lignin; thus, four typical β-O-4 lignin dimer compounds with different substituents on Cα and Cβ position (including CαO, CαOH and CβCH2OH groups) were synthesized. The results showed that a CβCH2OH group greatly inhibited the generation of volatile products, and promoted the generation of char. When the CαO group existed alone, the volatility of model compounds reached a maximum of ∼94 mass-%. At low temperatures (<300 °C), the cleavage of intermolecular linkages dominated, followed by secondary pyrolysis of primary products to various gases (e.g., CO2, CH4, CO). Guaiacol and 2-methoxy-benzaldehyde, two typical products, displayed yields that reflected the degree of cleavage of the CβO and CαCβ bonds. It was confirmed that oxidation of the CαOH group to CαO facilitated cleavage of the CαCβ bond and favored formation of 2-methoxy-benzaldehyde. In addition, new dimers that were intermediates during the pyrolysis process were formed via intermolecular elimination reactions that further affected products distribution and selectivity.

A simple method was demonstrated to oxidize glucose into gluconic acid in a concentrated FeCl3 solution. The maximum gluconic acid yield (52.3%) was achieved in the 40% FeCl3 solution at 110 °C in 4 hours. Formic and acetic acids were the main coproducts with an yield of 10–20%.

•Vanillin, vanillic acid and vanillyl alcohol were selected as lignin models.•Pyrolysis mechanism was revealed via combined Py-GC/MS and DFT calculations.•Two different competing degradation reactions were recognized in the three models.•Priority of common and specific degradation was different depending on the models.•The occurrence conditions of synergy and radical-induced pathway was studied.In this work, vanillin, vanillic acid and vanillyl alcohol were selected as guaiacyl-type monomeric model compounds to study the secondary pyrolysis mechanism of lignin. Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) was used to characterize products derived from the pyrolysis of lignin model compounds. Based on the free-radical theory, it was speculated that the pyrolysis of lignin model compounds concerned two processes: common degradation and specific degradation. By applying the density functional theory (DFT) method to study the detailed reaction pathways and energy changes, it revealed that the potential energy of the synergy process was lower than that of the radical-induced process during the functional group removal. Thereby CO, CO2, and HCHO were preferentially released along the synergy route. The enthalpy changes and experimental yields of products from the further degradation of guaiacol were basically consistent. Furthermore, the distinction of the potential energy between common degradation and specific degradation of each lignin model compound under various temperatures contributed to the different priority of the two degradation processes, as well as the different yields and species of pyrolytic products.

As promising and environmentally friendly catalysts, tungsten-containing heteropoly acids combined with supported noble metals were used for one-pot hydrothermal conversion of cellulose into polyols in the presence of pressurized hydrogen. The microcrystalline cellulose was completely converted over a mixed catalyst consisting of a low concentration of phosphotungstic acid (PTA) (0.03 wt%) and Ru/activated carbon (Ru/AC) via an one-pot hydrothermal reaction, with an ethylene glycol (EG) yield of up to 53.1% under optimal conditions. The catalytic activity of the mixed catalyst gradually decreased with increasing reaction runs, which could be mainly ascribed to the aggregation of Ru/AC particles, and to the coverage of the active sites of Ru due to the deposition of organic materials. Cellobiose was used as a model feedstock for a comparative study on the reaction pathways of the conversion of cellulose, and the results revealed that catalytic conversion of cellobiose consisted of at least three important parallel reactions under the present hydrothermal conditions, which were also most likely involved during the catalytic conversion of cellulose for EG production. Effective control of these reactions would be helpful to further maximize the EG yield during the catalytic conversion of cellulose.

The oxidative pyrolysis of black liquor solids (BLS), alkali lignin (AL), and enzymatic hydrolysis/mild acidolysis lignin (EMAL) from the same Cunninghamia lanceolata was studied by pyrolysis coupled with gas chromatography-mass spectrometry (Py-GC-MS) at 600 °C in air atmosphere. A closed tubular reactor was used to study the oxidative pyrolysis of the three samples. The effect of reaction time on the product was investigated. It was found that oxygen dramatically promoted the decomposition of lignin. Guaiacol and 4-methyl-guaiacol were the top two products in BLS and AL, whereas coniferyl aldehyde and 4-vinyl-guaiacol were the top two yields in EMAL. The yield of noncondensable gas increased with the reaction time, whereas the yield of phenolic compounds decreased quickly after 60 s in AL and EMAL.

Cellulose could be efficiently converted into sorbitol in the presence of hydrogen and an extremely low phosphoric acid concentration over a magnetic catalyst. Effects of various process conditions toward the conversion efficiency were discussed in greater detail. X-ray powder diffraction analysis indicated the essential properties of prepared catalysts. A sorbitol yield of 68.07% was obtained at 488 K with a catalyst dosage of 20%. The experiments showed that Ni4.63Cu1Al1.82Fe0.79 sustained better activity after being reused 3 or 4 times.

Acetic acid ethanol-based organosolv pretreatment of sugar cane bagasse was performed to enhance enzymatic hydrolysis. The effect of different parameters (including temperature, reaction time, solvent concentration, and acid catalyst dose) on pretreatment prehydrolyzate and subsequent enzymatic digestibility was determined. During the pretreatment process, 11.83 g of xylose based on 100 g of raw material could be obtained. After the ethanol-based pretreatment, the enzymatic hydrolysis was enhanced and the highest glucose yield of 40.99 g based on 100 g of raw material could be obtained, representing 93.8% of glucose in sugar cane bagasse. The maximum total sugar yields occurred at 190 °C, 45 min, 60:40 ethanol/water, and 5% dosage of acetic acid, reaching 58.36 g (including 17.69 g of xylose and 40.67 g of glucose) based on 100 g of raw material, representing 85.4% of total sugars in raw material. Furthermore, characterization of the pretreated sugar cane bagasse using X-ray diffraction and scanning electron microscopy analyses were also developed. The results suggested that ethanol-based organosolv pretreatment could enhance enzymatic digestibilities because of the delignification and removal of xylan.

Many factors affect the characteristics of stickies and their removal from deinked paper pulp. Because most papers have a specific service lifetime and because there is often a time lag between collection and processing for paper recycling, the adhesives on the collected papers can age. This study investigates the effects of the aging of pressure-sensitive adhesives on stickies properties and their removal efficiency during paper recycling. Adhesives coated on the surface of label paper were subjected to accelerated aging with specialized equipment and introduced into paper as the origin of stickies. The results showed that adhesive aging deteriorated the adhesion performance, surface physicochemical characteristics, and elasticity of the stickies particles. The aging had a direct effect on particle size during recycling unit operations. The removal efficiencies of adhesive contaminants during screening and flotation were reduced as a result of adhesive aging. Heterogeneity in the aging composition of stickies mixtures also had a negative effect on their removal behavior.

Recently, research on the production and transformation of sorbitol has become exciting in chemical industry and in catalysis studies for its broad applications. It opens up a new path for achieving sustainable energy supply and chemicals production. Here we mainly review the catalytic routes for the synthesis of sorbitol and conversion of sorbitol into high value-added compounds such as lower alcohols, paraffins, isosorbide, and other derivatives. Meanwhile, some promising and valuable research directions are suggested based on the major challenges emerged in current research, such as the development of efficient magnetic catalysts, microwave heating, and other hydrogen sources.

The pyrolysis behaviors of corn stalk and its three real components (i.e. hemicellulose, cellulose, and lignin) have been investigated with the techniques of TG-MS and Py-GC/MS. The thermal behavior and the evolution profiles of major volatile fragments from each sample pyrolysis have been discussed in depth, while paying close attention to the impact and contributions of each component on the raw material pyrolysis. It was found that pyrolysis of the corn stalk was a comprehensive reflection of its three main components both on thermogravimetric characteristics and on products distribution and their formation profiles. Hemicellulose definitely made the greatest contribution to the formation of acids and ketones at around 300 °C. Cellulose was more dedicated to the products of furans and small molecule aldehydes in a short temperature range 320–410 °C. While lignin mainly contributed to produce phenols and heterocyclic compounds over a wider temperature range 240–550 °C. The experimental results obtained in the present work are of interest for further studies on selective fast pyrolysis of biomass into energy and chemicals.Highlights► Each actual component of corn stalk was used for pyrolysis studies. ► Thermochemical stabilities of samples were first compared under the same conditions. ► Py-GC/MS and TG-MS used in combination to provide more pyrolysis information. ► Impact and contributions of components on raw material pyrolysis were discussed.

Chemical components of methylbenzene/ethanol extractives of Eucalyptus grandis were identified by GC/MS and different methylbenzene/ethanol solutions (9/1, 4/1, 2/1, 1/1, 1/2) were used to describe their distinctions. The distributions of micro particles in each extractive were studied simultaneously. The results show that there were significant differences between the various extractives, although the extractives were essentially the same, i.e., alcohols, alkanes, esters and acids. With the increase of ethanol composition in the solutions, the total amount of extractives increased; in solvent with higher amounts of ethanol, some acidic structures or acids, such as glutaric acid, could be seen. An investigation of micro particles indicated that the distribution of particle size of each sample did not change greatly between the solutions. A slight decrease in size was seen with the reduction in the amount of methylbenzene.

This study demonstrates a headspace gas chromatographic(HS-GC) technique for the determination of residual epichlorohydrin (ECH) and generated 1,3-dichloro-2-propanol (DCP) in synthesis process of 3-chloro-2-hydroxypropyltrimethylammonium chloride (CHTAC). By a weight-based sampling method, coupled with significant dilution in 15.8% sodium sulfate and 0.1% silver nitrate mixed solution rapidly, the sample for HS-GC analysis is prepared. Based on the reaction stoichiometry, the conversion (R) of CHTAC during the synthesis process can be calculated from sampling weight and GC peak area. The results showed that the method has a good measurement precision (RSD < 2.5%) and accuracy (recovery = 101–104%) for the quantification of both ECH and DCP in the process samples. The present method is simple and accurate, which can be used for the efficient determination of the CHTAC conversion in the synthesis research.

Products derived from bamboo EMAL pyrolysis were investigated by means of pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and the effects of temperature and catalyst (sodium chloride, permutite) on the yields of pyrolysis products were probed in detail. The results showed that thermal degradation of EMAL mainly occurred at the temperature range from 250 °C to 600 °C, and both the temperature and catalyst in EMAL pyrolysis were important factors in the formation or inhibition of products. The products that derived from p-hydroxyphenylpropanoid, guaiacylpropanoid, and syringylpropanoid of lignin units by pyrolytic reactions were classified as the heterocycle (2,3-dihydrobenzofuran), phenols, a small quantity of acetic acid and furans, etc. With an increase of pyrolysis temperature, the amount fraction of 2,3-dihydrobenzofuran (DHBF) decreased from 66.26% to 19.15%. Moreover, when the additive catalyst increased from 5% to 20%, permutite catalyst improved in the formation of DHBF from19.15% to 24.19%, whereas NaCl catalyst was effective to inhibit the production of DHBF from 19.15% to 13.08%. Permutite promoted the production of coke from EMAL pyrolysis, conversely, NaCl had an inhibiting effect on the generation of coke. And NaCl catalyst had a significant catalytic effect on raising or reducing of the product yields in bamboo lignin pyrolysis.

The structural characteristics of hemicelluloses isolated from delignified wheat straw were investigated by ion chromatography, FT-IR and NMR. The pyrolytic characteristic and the products at different temperatures were studied by TG and pyrolysis gas chromatography and mass spectrometry (py-GC/MS). The results showed wheat straw hemicelluloses were mainly consisting of arabinoxylan and uronic acids, the typical structure of straw hemicelluloses. The TG and DTG curves suggested the mass loss of hemicelluloses mainly happened between 190 and 315 °C and formed a 24 wt.% residue at 700 °C. The result of py-GC/MS revealed that the volatile products at different temperatures varied greatly and the main products of hemicellulose pyrolysis were acetic acid, carbon oxide, 2-furaldehyde, cyclopenten-1-one derivatives and small amounts of aromatic compounds which were very useful chemicals.

•Five lignin were extracted by different processes.•The isolated lignin was introduced to assess their influence on enzymatic digestibility of cellulose fibers.•The inhibition of lignin content and enzyme loading was different.•The proposed process made a contribution to understand how lignin influence cellulose enzymatic digestibility.The different physical and chemical properties of lignin might have various effects on the enzymatic hydrolysis of lignocellulosic substrates. In this study, the influence of lignin on enzymatic digestibility of cellulose was assessed. Addition of 20% (4 g/L) isolated enzymatic lignin (lignin 2 and 3) and kraft lignin (lignin 4) resulted in 5–20% drop of glucose yield, depending on lignin sources. The inhibitory effect of lignin was abated as the enzyme loading increased from 10 to 20 FPU/g dry substrate. However, the increasing lignin amount to 40% (8 g/L) did not appear to further decrease the cellulose hydrolysis efficiency. Ethanol lignin (lignin 1) and calcium lignosulfonate (lignin 5) had no negative effect on the enzymatic hydrolysis of cellulose at cellulase loading of 10 or 20 FPU/g dry substrate, the increasing lignin content to 40% presented 6.2% increase of glucose yield. The results indicated that different lignin had significantly influence on the enzymatic hydrolysis, which was confirmed by analysis in chemical composition, elemental analysis, functionality, and thermogravimetry.Download high-res image (165KB)Download full-size image

Ru/C catalyst and extremely low phosphoric acid were used for direct conversion of cellobiose into sorbitol under hydrogen atmosphere. Effects of various parameters and catalyst reuse on the reaction performance were investigated in detail. An optimized sorbitol yield of 87.1% was attained at 458 K and 3 MPa H2 for 1 h with catalyst usage of 15% in 0.05 wt.% phosphoric acid. The physicochemical properties of used Ru/C catalysts were characterized with various techniques to explore the specific causes for deactivation.Download full-size imageHighlights► A feasible catalytic process was proposed for conversion of cellobiose into sorbitol. ► The reaction system was of high efficiency and environmentally friendly. ► The specific inactivation process of Ru/C catalyst was investigated in detail.

•Molecular weight of lignin was not affected on the volatile product species.•Low molecular weight lead to the yields of CH4, CO2, phenol and alkyl phenol increased.•High molecular weight favored the generation of guaiacol and alkyl guaiacol.The effects of molecular weight on the pyrolysis products properties of alkali lignin were investigated by using thermogravimetric analyzer coupled with Fourier transform infrared spectrometry (TG-FTIR) and tube furnace. Four lignin samples, including pure alkali lignin (AL), more than 10 kDa lignin fraction (AL-10kDa), 5–10 kDa lignin fraction (AL-5kDa) and 1–5 kDa lignin fraction (AL-1kDa) were firstly prepared by ultrafiltration membrane technology. Then the thermal behavior and volatile evolution patterns of the four lignin samples were investigated by TG-FTIR, and the component properties of condensable and incondensable products obtained from tube furnace were characterized by the gas chromatography/mass spectroscopy (GC/MS) and gas chromatography (GC). TG-FTIR results indicated that the molecular weight of lignin was not significantly affected on the evolution temperature ranges and volatile product species, while has an obviously effect on the total yields of CH4, CO2, phenols and aromatics products. GC/MS and GC results indicated that low molecular weight helps to crack the methoxy groups of lignin leading to the yields of CH4, CO, CO2, phenol and alkyl phenol increased, while high molecular weight favored the generation of guaiacol and alkyl guaiacol. Meanwhile, the effect of molecular weight on the yields of aromatics was also affected by the pyrolysis temperature.