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The biomass valorization is of great importance as an alternative for the production of transport fuels and fine chemicals. Furfural hydrogenation to furfuryl alcohol is a prevailing industrial route for the utilization of hemicellulose component of biomass. The toxicity of the chromium species in commercial copper chromite catalyst for furfuryl alcohol production motivates the development of efficient chromium-free catalyst. Thus, a highly efficient silica supported copper catalyst is developed in this study. The catalyst is prepared by freeze drying of a gel precursor that is synthesized by ammonia evaporation, followed by calcination and H2 reduction. The catalyst exhibits higher furfural hydrogenation activity than oven dried catalyst, commercial copper chromite catalyst and a plant supplied commercial silica supported copper catalyst. The catalyst also shows good stability. The superior performance of the freeze dried catalyst has resulted from its developed pore structure and higher amount of Cu0 as well as Cu+ active sites.

We report a facile atom assembly of heterometallic bi-/tri-atom clusters (Pt1,2Cu1) starting from mono-metallic atoms (Pt1) in a protective PDMS-PEG layer.

The PdII–Cl–CuI complex and HCl have evolved as catalytically active species from paired PdCl2–CuCl2/[BMim]Cl in catalytic hydrolysis of β-1,4-glycosidic bonds in cellulose.

The rapid consumption of fossil resources and the grim environmental situation encourage the application of renewable and clean energy resources. Conversion of biomass, which is a kind of renewable, CO2 neutral as well as abundant reserves carbon containing resource, is significantly important. The production of fuels from biomass by means of gasification and Fischer-Tropsch synthesis is one of the most promising routes for industrial applications. The wax-free liquid fuels synthesis directly from H2-deficient syngas similar to bio-gas is highly advantageous for reducing investment and operating cost. Thus, the Mn-promoted meso-ZSM-5 supported cobalt catalyst was applied for the production of wax-free liquid fuels by catalytic H2-deficient syngas conversion in this study. The performance of the reaction was influenced obviously by Mn content. The cobalt dispersion increased with the addition of Mn, whereas the reduction degree decreased after Mn doping. Then, the balance between the dispersion and reduction degree led to the change in CO uptake followed a volcanic curve. The catalyst with moderate amount of Mn (1 wt%) had the suitable cobalt particle size and the maximum CO uptake. Thus, the highest CO conversion was obtained over Co-1Mn/meso-ZSM-5 catalyst thanks to its maximum exposed active sites. The appropriate amount of Mn addition also resulted in the decreasing of CH4 selectivity. The highest space time yield of liquid fuels was acquired over the Co-1Mn/meso-ZSM-5 catalyst from H2-deficient syngas conversion under the moderate conditions.

The lignocellulosic biomass utilization is a feasible way to obtain alternative fuels and chemicals. Xylitol as an ideal sweetener is one of the top twelve value-added chemicals derived from biomass. Xylitol is also used in the pharmaceutical and cosmetics industries. Thus, the production of xylitol from biomass is significantly important. A silica supported nickel catalyst derived from nickel phyllosilicate for efficient aqueous phase xylose hydrogenation to xylitol was developed in this study. Higher xylose conversion was observed over the nickel phyllosilicate derived catalyst compared to nickel oxide derived nickel catalyst prepared by impregnation and commercial Raney Ni catalyst. The excellent xylitol selectivity (approximately 99 %) was also obtained over the nickel phyllosilicate derived catalyst. The differences in structure and property resulted from different preparation methods were investigated by means of XRF, N2 physisorption, XRD, FT-IR, H2-TPR, TEM as well as H2-TPD. The higher nickel dispersion of nickel phyllosilicate derived catalysts, which could be synthesized by ammonia evaporation and deposition-precipitation using Na2CO3 as precipitator, led to higher xylose conversion. In addition, the phyllosilicate derived nickel catalyst demonstrated outstanding stability. Consequently, phyllosilicate derived nickel catalyst is promising for the industrial application for the production of xylitol form xylose aqueous hydrogenation thanks to its higher activity and selectivity as well as good stability.

Although numerous efforts have been made in direct syngas conversion to higher alcohols via Fischer–Tropsch synthesis, the higher alcohols distribution remains a challenge. Here, we introduce alkaline earth metal oxide as promoter into activated carbon supported cobalt catalyst to tune distribution of higher alcohols. With the addition of Mg, the distribution of C2-5 alcohols increase from 41.2 to 75.8% accompanying with distribution of C6-18 alcohols decrease from 52.8 to 14.0%. Ba-promoted Co based catalyst (CoBa/AC) presents similar alcohols distribution to un-promoted catalyst, while the alcohol selectivity over CoBa/AC is higher than Co/AC. For promoted catalysts, the distribution of C6-18 alcohols increased in the order of Mg

An in situ generated AuIII catalyst is found to catalyze the direct oxidation of CH4 to C1 oxygenates in 1-ethylimidazolium bis-(trifluoromethylsulfonyl)amide ([Eim][NTf2]) at 90 °C. The formation ...

Selectively producing chemicals from cellulosic carbohydrate pyrolysis in large quantities is challenging, especially anhydro-monosaccharides with double-ring, triple-ring, and furan/pyran structures. Formation of these sugar derivatives greatly improves when the pyranose ring opening is inhibited during pyrolysis, which is accomplished by chemically replacing the hydroxyl group at the anomeric carbon with an alkoxy group. A simpler ring-locking approach is required for scalable chemical production, however. In this work, we demonstrate that introducing Na2SO4 and H2SO4 to glucose pyrolysis significantly increases levoglucosan (LGA) formation, from a 6% yield to as high as 40% at 350 °C. With H2SO4 as the acid catalyst, Na+ acts to inhibit the ring opening. Glucose pyrolysis with different alkali metal cations (Li+, Na+, K+, Rb+ and Cs+) gives different reaction products, which can be explained largely by an ionic electronegativity effect. Weaker electronegativity promotes the formation of a ring-opened product such as 5-hydroxymethylfurfural (HMF), and stronger electronegativity increases the formation of sequential dehydration products like levoglucosenone (LGO). Sodium has the optimum ionic electronegativity for preferential association with the ring oxygen. The Na2SO4/H2SO4 combination improved LGA yields for all carbohydrate substrates tested (up to 70%), including lignocellulose. These findings highlight the potential of using alkali metal salts to produce anhydrosugars in high yields from cellulosic carbohydrate pyrolysis.

Humin formation is one of the key issues that hinders economical 5-HMF production from hexose sugars such as glucose and fructose. In this work, the mechanism of humin formation in glucose/fructose conversion to HMF was studied in an ionic liquid system (1-butyl-3-methylimidazolium chloride, [BMIM]Cl) with CrCl3 as the catalyst. Elemental analysis, XRD, FT-IR, and TEM were applied to study the molecular structure and morphology of the solid humins. The possible intermediates to form solid humins were investigated by HPLC-MS. We synthesized furanic model compounds that mimic the experimentally identified humin intermediates to investigate the mechanism of humin growth at an early stage. The results showed that a furan compound bearing a hydroxymethyl and an electron-donating group was unstable due to three types of reactions: (1) bimolecular ether formation reactions; (2) intermolecular addition reaction; (3) furan ring opening reaction with water. The stability of a furan compound in [BMIM]Cl was increased when the hydroxymethyl group of a furan compound was protected by a methyl group, and the stability was further enhanced with an additional electron-withdrawing group (such as an aldehyde group) on the furan ring. Protecting the hydroxymethyl group of 5-HMF with a methyl group allows easy separation of the products from the [BMIM]Cl solvent through extraction.

Furfuryl alcohol, a vital intermediate for the production of foundry resins, fragrances, pharmaceuticals and pesticide, is produced by hydrogenation of furfural in gas phase or liquid phase. The furfuryl alcohol production in gas phase over silica supported copper catalyst is favored thanks to the environmental and technical advantages. The effect of preparation methods of silica supported copper catalysts on the structure and performance was investigated by means of ICP, N2 physisorption, ex-situ/in-situ XRD, in-situ XPS, FT-IR, H2-TPR, TEM, N2O titration, TG as well as furfural hydrogenation. The results indicated that the different catalyst synthesis strategies led to the diverse copper species in the calcined samples and disparate Cu0 surface area as well as different molar ratio of Cu+/(Cu+ + Cu0) in the fresh samples. The performance of impregnation derived sample was poorer than that of commercial CuCr-Strem catalyst. The catalysts prepared by deposition precipitation and ion exchange exhibited similar performance to the CuCr-Strem. The ammonia evaporation derived catalyst (Cu/SiO2-EA) showed superior performance in the activity, selectivity and stability among all the studied catalysts. The excellent performance was related to the highest surface area of Cu0, smallest copper particle size, large surface area and pore volume as well as appropriate higher Cu+/(Cu+ + Cu0) ratio. Furthermore, all the copper catalysts went through deactivation, which was caused by carbon deposition, during the reaction. Owing to the largest amount of Cu0 sites and large SBET, the Cu/SiO2-EA exhibited the slowest deactivation rate.

This review covers the characteristics of pyrolysis and catalytic pyrolysis bio-oils by focusing on the fundamental factors that determine bio-oil upgradability. The abundant works on the subject of bio-oil production from lignocellulosic biomass were studied to establish the essential attributes of the bio-oils for assessment of the oil stability and upgradability. Bio-oils from catalytic pyrolysis processes relating to catalysts of different compositions and structures are discussed. A general relationship between the higher heating value and the oxygen content in the catalytic pyrolysis oils exists, but this relationship does not apply to the thermal pyrolysis oil. Reporting bio-oil yield is meaningful only when the oxygen content of the oil is measured because the pyrolytic oil stability is mainly determined by the oxygen content. Isoenergy plot that associates bio-oil yield with oxygen content is presented and discussed.

Expensive cellulase and complex detoxification procedures increase the cost of biomass lactic acid fermentation. Therefore, it is of great significance to develop a robust method to ferment lactic acid using biomass by avoiding cellulase and detoxification. This study demonstrates the advantage of combining mechanocatalytic P

Selective hydrocleavage of aromatic C O bond while preserving the aromatic ring is a desired catalytic process in hydrodeoxygenation (HDO) of biomass derived aromatic oxygenates to high value biochemicals. Guaiacol with typical methoxy and phenolic hydroxyl groups is a representative aromatic di-oxygenates of lignin fragments. Sub-nanometer sized silver, a poor hydrogenation metal catalyst, was found to initiate H2 dissociation and H spillover onto anatase TiO2 (TiO2-A) surface. The spillover hydrogen enhanced the partial reduction of TiO2-A surface at a substantially lowered temperature as compared to the reduction of TiO2-A by molecular H2. The reduction of TiO2-A surface by spillover hydrogen was enhanced at Ag loading as low as 0.01 wt% on TiO2-A. The ratio of spillover H to Ag was as high as 675 at Ag loading of 0.01 wt% and the ratio decreased with increasing Ag loading. We found that the yield of phenolic products was linearly correlated with the amount of spillover hydrogen that created oxygen vacancy (Ov) through partial reduction of TiO2-A surface. Methanol was formed as the main side-product, indicating that the direct hydrocleavage of aromatic C-OCH3 in guaiacol is favored over that of aromatic C-OH on the created site.

A bubbling fluidized bed pyrolyzer was integrated with an in-situ honeycomb as a catalytic upgrading zone for the conversion of biomass to liquid fuels. In the upgrading zone, zeolite coated ceramic honeycomb (ZCCH) catalysts consisting of ZSM-5 (Si/Al = 25) were stacked and N2 or recycled non-condensable gas was used as a carrier gas. Ground corncob particles were fast pyrolyzed in the bubbling bed using fine sand particles as a heat carrier and the resulting pyrolysis vapors were passed on-line over the catalytic upgrading zone. The influence of carrier gas, temperature, and weight hourly space velocity (WHSV) of catalyst on the oil product properties, distribution and mass balance were studied. Using ZCCH effectively increased the hydrocarbon yield and the heating value of the dry oil, especially in the presence of the recycled noncondensable gas. Even a low usage of zeolite catalyst at WSHVof 180 h‒1 was effective in upgrading the pyrolysis oil and other light olefins. The highest hydrocarbon (⩾C2) and liquid aromatics yields reached to 14.23 and 4.17 wt-%, respectively. The undesirable products including light oxygenates, furans dramatically decreased in the presence of the ZCCH catalyst.

The synthesis of furan compounds by renewable carbohydrates has emerged as an important path toward biomass utilization. 5-Hydroxymethylfurfural (5-HMF) and furfural are two typical furan products from cellulosic and hemicellulosic materials, of which the primary components (hexoses and pentoses) undergo selective dehydration. It is worth noting that hemicellulose is rich in not only pentoses but also hexoses, indicating the feasibility of producing 5-HMF and furfural simultaneously. However, research on the production of 5-HMF from hemicellulose-derived hexoses remains lacking. Mannose, a major hexose component of hemicellulose, has been previously found to be a suitable feedstock for 5-HMF production in the presence of homogeneous catalysts, such as metal salts. In this work, Cr-, Al- and Sn/MCM-41 catalysts were prepared by a simple impregnation method and characterized. The conversion of mannose into 5-HMF was evaluated in dimethyl sulfoxide (DMSO) solvent. It was found that the as-synthesized Sn/MCM-41 catalyst showed a superior activity to Cr/MCM-41 and Al/MCM-41. Mannose could be effectively converted into 5-HMF with a yield of ∼45% and ∼88% conversion at 150 °C after 60 min, which were comparable to reported results over heterogeneous catalysts. The as-synthesized Sn/MCM-41 catalyst was also efficient for the conversion of glucose and fructose with reasonable 5-HMF yields. The Sn/MCM-41 catalyst could be reused for eight consecutive cycles without significant loss of catalytic activity.

Phosphorus pentoxide (P2O5)/metal chloride mixtures could significantly improve 5-HMF yield and selectivity for the catalytic conversion of fructose under mild conditions, whereas neither P2O5 nor tested metal chloride alone gave reasonable performances. A maximum 5-HMF yield of 75% with ∼85% selectivity could be achieved within 30 min at 80 °C.

The rates of Bronsted-acid-catalyzed reactions of ethyl tert-butyl ether, tert-butanol, levoglucosan, 1,2-propanediol, fructose, cellobiose, and xylitol were measured in solvent mixtures of water with three polar aprotic cosolvents: γ-valerolactone; 1,4-dioxane; and tetrahydrofuran. As the water content of the solvent environment decreases, reactants with more hydroxyl groups have higher catalytic turnover rates for both hydrolysis and dehydration reactions. We present classical molecular dynamics simulations to explain these solvent effects in terms of three simulation-derived observables: (1) the extent of water enrichment in the local solvent domain of the reactant; (2) the average hydrogen bonding lifetime between water molecules and the reactant; and (3) the fraction of the reactant accessible surface area occupied by hydroxyl groups, all as a function of solvent composition. We develop a model, constituted by linear combinations of these three observables, that predicts experimentally determined rate constants as a function of solvent composition for the entire set of acid-catalyzed reactions.

Producing bio-intermediates from lignocellulosic biomass with minimal process steps has a far-reaching impact on the biofuel industry. We studied the metal chloride catalyzed aldol condensation of furfural with acetone under conditions compatible with the upstream polysaccharide conversions to furfurals. In situ far infrared spectroscopy (FIR) was applied to guide the screening of aldol condensation catalysts based on the distinguishing characteristics of metal chlorides in their coordination chemistries with carbonyl-containing compounds. NiCl2, CoCl2, CrCl3, VCl3, FeCl3, and CuCl2 were selected as the potential catalysts in this study. The FIR results further helped to rationalize the excellent catalytic performance of VCl3 in furfural condensation with acetone, with 94.7% yield of biofuel intermediates (C8, C13) in 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) solvent. Remarkably, addition of ethanol facilitated the acetal pathway of the condensation reaction, which dramatically increased the desired product selectivity over the furfural pathway. Most significantly, we demonstrate for the first time that VCl3 catalyzed aldol condensation in acidic medium is fully compatible with upstream polysaccharide hydrolysis to monosaccharide and the subsequent monosaccharide isomerization and dehydration to furfurals. Our preliminary results showed that a 44% yield of biofuel intermediates (C8, C13) can be obtained in one-pot conversion of xylose catalyzed by paired metal chlorides, CrCl2 and VCl3. A number of prior works have shown that the biofuel intermediates derived from the one-pot reaction of this work can be readily hydrogenated to biofuels.

The production of furfuryl alcohol from furfural hydrogenation in gas phase is of great significance for the valorization of biomass. The existing catalyst for this transformation suffers from high cost and complex preparation process. Thus, a highly efficient copper catalyst was developed by a simple impregnation method using ethanolamine modified granular silica as carrier. The catalytic performance was related to the amount of ethanolamine used in modification. Highly dispersed copper with uniform particle size distribution was obtained from appropriate amount of ethanolamine modified granular silica. The ethanolamine modified granular silica (mass ratio between ethanolamine and silica was 3 in the initial modification mixture) supported copper catalyst exhibited the best performance in terms of catalyst lifetime thanks to its maximum amount of Cu0 sites and largest amount of Cu+ sites. A slow deactivation of the catalyst after extended time on stream evaluation is attributed to carbon deposition and slow copper sintering.

The inhibition of lignin phenolics on fermenting microbes has become one of the major barriers in developing an economically viable process for cellulosic ethanol production. In this study, the toxicity to yeast cells and the inhibition to the very high gravity (VHG) fermentation of the phenolic compounds were investigated in the absence or presence of polyethylene glycol (PEG). It was found that the inhibitory effects of phenolic compounds on VHG ethanol fermentation depend on the activity of their hydroxyl (–OH) hydrogen. 250 g L−1 PEG-1000 detoxified 2.0 g L−1 guaiacol in the fermentation broth, and boosted the ethanol concentration from 131 g L−1 to 173 g L−1. The inhibitory effect of 5.0 g L−1 guaiacol on ethanol fermentation was also alleviated, and the ethanol concentration was increased from 51 g L−1 to 151 g L−1 after detoxification with 250 g L−1 PEG-1000. The 1H-NMR of hydroxyl group (–OH) of phenolic compounds in PEG revealed the role of hydrogen bonding formation on the in situ detoxification mechanism of PEG, and the order in the strength of the intermolecular hydrogen bond between phenolic compounds and PEG. Furthermore, the kinetics of VHG ethanol fermentation in the presence of phenolic compounds were determined. The obtained kinetic model (phenolic compounds inhibitory effect) fits well the kinetics of ethanol production from lignocellulosic hydrolyzates using batch VHG ethanol fermentation technology.

The selective production of platform chemicals from thermal conversion of biomass-derived carbohydrates is challenging. As precursors to natural products and drug molecules, anhydrosugars are difficult to synthesize from simple carbohydrates in large quantities without side products, due to various competing pathways during pyrolysis. Here we demonstrate that the nonselective chemistry of carbohydrate pyrolysis is substantially improved by alkoxy or phenoxy substitution at the anomeric carbon of glucose prior to thermal treatment. Through this ring-locking step, we found that the selectivity to 1,6-anhydro-β-D-glucopyranose (levoglucosan, LGA) increased from 2% to greater than 90% after fast pyrolysis of the resulting sugar at 600 °C. DFT analysis indicated that LGA formation becomes the dominant reaction pathway when the substituent group inhibits the pyranose ring from opening and fragmenting into non-anhydrosugar products. LGA forms selectively when the activation barrier for ring-opening is significantly increased over that for 1,6-elimination, with both barriers affected by the substituent type and anomeric position. These findings introduce the ring-locking concept to sugar pyrolysis chemistry and suggest a chemical-thermal treatment approach for upgrading simple and complex carbohydrates.

A novel pretreatment method-concerted ionic liquid (CIL) pretreatment was proposed and the mechanism of CIL pretreatment to overcome the recalcitrance of biomass was investigated in this study. The CIL refers to a combination of a protic ionic liquid (PIL) pyrrolidinium acetate ([Pyrr][AC]) and an aprotic ionic liquid (AIL) 1-butyl-3-methylimidazolium acetate ([BMIM][AC]) in varied proportion. In the CIL system, [Pyrr][AC] selectively dissolves lignin from biomass and [BMIM][AC] dissolves part of cellulose and hemicelluloses. Besides lignin, hemicelluloses are also an important factor of biomass recalcitrance. Optimized [BMIM][AC] fraction in the CIL pretreatment resulted in the efficient removal of lignocellulose complex while [Pyrr][AC] selectively fractionated lignin component. CILs exhibited superior efficiency in overcoming the recalcitrance of eucalyptus bark over that of the individual constituent ionic liquids. Compared to pretreatments by individual ILs of the pair, the CIL pretreatment increased the glucose yield by 30% from the cellulose of eucalyptus bark. High cellulose conversion of 91% (wt%) was achieved from enzymatic conversion of eucalyptus bark by optimizing the lignin and hemicelluloses removal.

Ionic liquids have been widely studied as effective reaction media for the conversion of glucose or cellulose to 5-hydroxymethhylfurfural (5-HMF). However, the recovery of 5-HMF from ionic liquids, typically carried out by extraction, has been encountered with very low extraction efficiency, which limited the reusability of the solvents. Through this work, based on the model biphasic system that consists of 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) as the ionic liquid phase and methyl isobutyl ketone (MIBK) as the extractant phase, the dominant force that suppresses the extraction efficiency of 5-HMF was identified as being the strong hydrogen bonding between 5-HMF and [BMIM]Cl. Solvent mediation with functional promoters have been established as a new strategy to shift this force, resulting in improved extraction efficiency of 5-HMF from the ionic liquid. For example, with ethanol as a promoter, the distribution coefficient of 5-HMF was about 10 times higher than that without a promoter.

Biodiesel is a sustainable and environmentally compatible diesel fuel substitute that presents certain limitations, particularly low-temperature flow properties, which are attributable to its long fatty chain structure. Branched alkyl derivates such as tertiary butyl ethers are efficient biodiesel additives for improved cold flow behaviour of biodiesel. In this study, tert-butoxymethylfurfural (tBMF) is synthesised as a biodiesel additive through etherification of 5-hydroxymethylfurfural (5-HMF), a non-edible biomass-derived building block, with isobutene (IB) on a series of acid zeolites and liquid acids. The catalytic activity and selectivity of a zeolite catalyst involve not only optimisation of the number and strength of its acidic sites and adsorption properties but also promotion of its internal pore space. Efficient solvent systems did not include extremely weakly polar or strongly polar solvents but included moderately polar solvents, such as glycol dimethyl ether which presents suitable hydrophilic/hydrophobic properties. The HY zeolite with a SiO2/Al2O3 mole ratio of 12 in combination with glycol dimethyl ether solvent exhibited an excellent tBMF selectivity of 94 mol% with 59 mol% 5-HMF conversion after 3 h of reaction at 60 °C. Side reactions of 5-HMF dimerisation and the IB oligomerisation were minimal under mild reaction conditions. The activity of the deactivated catalyst was fully recovered by calcination in air, and a detailed deactivation mechanism was proposed.

A series of amine-sulfonate functionalized ionic liquids (ASF-ILs) were synthesized, characterized, and evaluated for the dissolution of model biopolymers (cellulose, xylan, kraft lignin and lignosulfonate). The ASF-ILs were prepared in high atomic efficiency. Most of the ASF-ILs dissolve kraft lignin and lignosulfonate efficiently at 373 K, with solubilities of 0.220–0.385 g for kraft lignin and of 0.150–0.290 g for lignosulfonate per gram of ASF-ILs. In contrast, xylan and cellulose are scarcely soluble (

Increasing the glucose loading in the 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) ionic liquid containing a dissolved CrCl3 catalyst system led to excessive formation of humins and a serious decrease in the 5-hydroxymethylfurfural (5-HMF) yield. A biphasic system containing glycol dimethyl ether (GDE) as the extraction phase, and [BMIM]Cl/CrCl3/glucose in combination with a partitioned amount of GDE and an appropriate amount of water as the reaction phase was found to be highly efficient for the reaction; CrCl3 catalyzed the formation of 5-HMF in 64.5 mol% yield from a very high glucose concentration (80 wt% with respect to the ionic liquid) at 108 °C. This 5-HMF yield in the [BMIM]Cl–GDE–H2O ternary biphasic system nearly doubled that obtained in the single [BMIM]Cl/CrCl3/glucose reaction phase. Importantly, the GDE phase contained about 56% of the generated 5-HMF without detectable contamination by the ionic liquid or carbohydrates. GDE served multiple functions: as a hydrogen-bond acceptor, it exhibited excellent extraction performance for 5-HMF; due to its low boiling point and suitable solubility saturation point in the ionic liquid, a sustained GDE bubbling phenomenon in the ionic liquid phase was observed that promoted the rate of inter-phase mass-transfer of 5-HMF in reactions; and GDE mediated the [BMIM]Cl phase to a reduced viscosity. In addition, an appropriate amount of water in the ternary system promoted the extraction efficiency of 5-HMF and also lowered the viscosity of [BMIM]Cl/glucose. The ionic liquid–organics–water ternary biphasic system has been demonstrated for high 5-HMF productivity and separation efficiency.

a b s t r a c t While chromium trichloride hydrate (CrCl3·6H2O) effectively catalyzed the isomerization of glucose into fructose in aqueous solution, a general product selectivity behavior was observed independent of reaction variables such as reaction time, temperature, catalyst loading, halide ion, and initial glucose concentra- tion. By studying the mixed solution of dimethylsulfoxide (DMSO) and water at varied DMSO/H2O ratios, it was found that deviation from the general water-phase fructose yield curve, with concomitant 5- hydroxymethylfurfral (HMF) formation, occurred when the fructose concentration in available water became sufficiently high in DMSO rich solvent mix. Therefore, tuning the solvent system was the most effective approach to change the product distribution from CrCl3·6H2O catalyzed glucose conversion. The apparent activation energy of glucose conversion in the studied system was estimated to be 58.6 kJ mol −1 . Special attention was also given to gain some mechanistic insights by control experiments with simple model compounds and additives, 13 C NMR and UV-vis spectroscopic analyses.

The production of 5-Hydroxymethylfurfural (HMF) from hexoses is a stoichiometric dehydration process. Water content in a solvent is expected to play an important role in HMF formation by affecting the equilibrium and the reaction kinetics. In this work, the impact of water content on the catalytic conversion of glucose was investigated in detail in different dimethylsulfoxide (DMSO)/H2O mixtures (vw = 0–1) with chromium trichloride hexahydrate (CrCl36H2O) as the catalyst at 110–130 C. Water content in the binary mix was found to dominantly affect the product distribution. Anhydrous DMSO system is favored for HMF formation from glucose but caused a number of side reactions, especially the undesired dehydration of glucose into cellobiose. Adding an appropriate amount of water in DMSO (vw = 0.17–0.50) was found to significantly suppress the undesired dehydration side reactions while preserving high HMF yield over the CrCl36H2O catalyst, therefore remarkably improving the total selectivity of HMF and fructose from glucose conversion. While CrCl36H2O was essential in isomerizing glucose into fructose, hydrochloric acid (HCl) from CrCl36H2O hydrolysis in DMSO/H2O mixed system catalyzed the dehydration of in situ formed fructose to HMF. Although effective water removal was pronounced toward improving HMF yield from hexose dehydration in previous work, the results of this work indicate that a controlled amount of water in the non-aqueous system is favorable to drive the thermodynamic equilibrium for high HMF yield and desired product selectivity, providing reference information on designing a one-pot process for HMF synthesis from cellulosic materials.

A cobalt catalyst has been demonstrated, for the first time, to be effective for the reductive cleavage of inert aromatic C O bonds with high selectivity. Compared with previous Ni catalysts, the cobalt catalyst reported here is more commercially available and air-stable.

Fuel ethanol is an attractive alternative to fossil-based fuels or fuel additives. Very-high-gravity (VHG) ethanol fermentation is a promising technology to reduce energy consumption in distillation. However, yeast cells subjected to a high concentration of ethanol and osmotic stress readily lose cell viability, resulting in reduced ethanol productivity. Here we report the beneficial effect of fully water-soluble polyethylene glycol (PEG) in chemically exo-protecting yeast cells during fermentation, resulting in largely boosted cell vitality and tolerance to high ethanol concentration. The final ethanol concentration and the yeast cell viability were substantially increased as compared to PEG-free fermentation. The recovered exo-protected yeast was further demonstrated to continue to deliver superior bio-catalytic performance in subsequent fermentations over that recovered from PEG-free broth. Furthermore, the water-soluble PEG was readily recycled for reuse after distillation of ethanol.

In this work, the complex dichlorobis(2,9-dimethyl-1,10-phenanthroline)ruthenium(II) (Ru(DMP)2Cl2) was found to effectively catalyze the direct reductive amination of bio-based 5-hydroxymethylfurfural (5-HMF) in the presence of H2 (g) in ethanol solvent. Good product yields (66–95%) were obtained from a broad substrate scope of primary and secondary amines.

Impurities present in commercially available ionic liquids display prominent catalytic functions toward carbohydrate conversion. Little conversion was observed at 180 °C with high purity [EMIM]Cl ionic liquid whereas significant conversion was observed for ionic liquids of lower purity levels. Addition of metal halides to high purity [EMIM]Cl catalyze cellulose conversion with drastically different product selectivities dependent on the metal ions. CuCl2 is an active catalyst for hydrolyzing cellulose and further degrading the products. CrCl2 is an active and a selective catalyst for the formation of 5-hydroxymethylfurfural (5-HMF). CrCl2 also helps stabilize the 5-HMF product. FeCl2 does not show catalytic activity. Metal impurities in ionic liquid correlate to the activities observed when similar metals were added to high purity ionic liquids.

Ionic liquids based on the 1-methylimidazolium cation with chloride, bromide, hydrogen sulfate, and tetrafluoroborate counterions along with 1-butyl-3-methylimidazolium hydrogen sulfate were employed to degrade two lignin model compounds, guaiacylglycerol-β-guaiacyl ether and veratrylglycerol-β-guaiacyl ether. The acidity of each ionic liquid was approximated using 3-nitroaniline as an indicator to measure the Hammett acidity (H 0 ). While all of the tested ionic liquids were strongly acidic (H 0 between 1.48 and 2.08), the relative acidity did not correlate with the ability of the ionic liquid to catalyze β-O-4 ether bond hydrolysis. The reactivity of the model compounds in the ionic liquids is dependent not only on the acidity, but also on the nature of the ions and their interaction with the model compounds.

Efficient hydrolytic depolymerization of crystalline cellulose to sugars is a critical step and has been a major barrier for improved economics in the utilization of cellulosic biomass. A novel catalytic system involving CuCl2 (primary metal chloride) paired with a second metal chloride, such as CrCl2, PdCl2, CrCl3 or FeCl3 in 1-ethyl-3-methylimidazolium chloride ([EMIM]Cl) ionic liquid solvent has been found to substantially accelerate the rate of cellulose depolymerization under mild conditions. These paired metal chlorides are particularly active for the hydrolytic cleavage of 1,4-glucosidic bonds when compared to the rates of acid-catalyzed hydrolysis at similar temperatures (80–120 ◦C). In contrast, single metal chlorides with the same total molar loading showed much lower activity under similar conditions. Experimental results illustrate the dramatic effect of the second metal chloride in the paired catalytic system. An array of characterization techniques, including electron paramagnetic resonance (EPR) spectroscopy, differential scanning calorimetry (DSC), X-ray absorption fine structure (XAFS) spectroscopy, and X-ray absorption near edge structure (XANES) spectroscopy, in combination with theoretical calculations at the DFT level, was used to reveal a preliminary understanding of possible mechanisms involved in the paired CuCl2/PdCl2 catalytic system. We discovered that Cu(II) was reduced during the course of the reaction to Cu(I) only in the presence of a second metal chloride and a carbohydrate source such as cellulose in the ionic liquid system. Our results suggest that Cu(II) generates protons by hydrolysis of water to catalyze the depolymerization step, and serves to regenerate Pd(II) reduced to Pd(0) by side reactions. Pd(II) likely facilitates the depolymerization step by coordinating the catalytic protons, and also promotes the formation of hydroxymethylfurfural (HMF). Our results also suggest that the C2-proton

A commercial Beta-type zeolite was studied for upgrading unsaturated fatty acids, a renewable feedstock. Catalyst calcination and additive addition were investigated aiming to improve the catalytic activity for the skeletal isomerization of oleic acid. Calcination at a temperature around 450 °C instead of the commonly used 550 °C generated catalysts with relatively low surface areas but high activities, which is attributed to the high Bronsted acidity as revealed by FTIR characterization. Addition of a small amount of water (2–5 wt% of fatty acid) to the fatty acid promoted the conversion, but any further increase in the amount of water would result in a catalytic activity loss. Although methanol did not show a promoting effect for the isomerization, the methyl ester of oleic acid showed a higher conversion than oleic acid on the same catalyst. The poisoning effect of the carboxylic group on oleic acid was demonstrated by the comparison of the isomerization reactions of oleic acid and 1-octadecene.

Fatty acids are an important class of feedstock for the production of many chemicals, such as surfactants, lubricants, biodiesel, etc. Fatty acids derived from vegetable oils and animal fats typically have linear aliphatic chain, and are therefore called linear fatty acids. Products based on branched fatty acids offer many attractive properties over those based on linear ones, e.g. low melting points and low viscosity. Catalytic skeletal isomerization of linear fatty acids to branched ones is particularly important for industrial production of branched fatty acids. This paper for the first time reveals the key properties of the most active zeolite catalysts for this reaction. Among many solid acid catalysts studied, acidic Beta zeolites were found to stand out in their performance for the reaction. In this work, several acidic Beta zeolites (HBeta) from commercial sources were evaluated for their performance in fatty acid skeletal isomerization. The activities of these zeolites under identical test conditions were found to vary in a wide range, even with similar silica to alumina molar ratios (SAR). A combination of characterization techniques was used to systematically investigate the most critical property of the zeolites responsible for the observed superior activity. All the HBeta zeolites in this study have high crystallinity. Pore size distribution of the zeolites was identified to be the most important factor that unambiguously correlates the catalyst activity to the amount of mesopores in the HBeta zeolites.

Cotton linters were partially hydrolyzed in dilute acid and the morphology of remaining macrofibrils was studied with scanning electron microscopy (SEM) under various magnifications. The crystalline region in cellulose is composed of microfibril bundles instead of separated microfibrils. These microfibril bundles in the macrofibrils were exposed by removing amorphous cellulose on and near the surface of the macrofibers. XRD suggests that the microfibril bundles have diameters of 20–30 nm. Cellulose apparent crystallinity was not altered by hydrolysis, as indicated by XRD and NMR results. These facts suggest that amorphous cellulose in the bulk (not on the surface) is not accessible to hydrolysis and that microfibril bundles are hydrolyzed through a surface reaction process. The observed agglomerization of macrofibers could be the result of the high surface potential from the remaining microfibrils or acid catalyzed intermolecular surface dehydration between macrofibrils.