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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.

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.

The synthesis of pyrrolidinones from reductive amination of levulinic acid (LA) with primary amines is reported. Pyrrolidinones have various applications such as surfactants, pharmaceutical intermediates, dispersants, and solvents. The half-sandwich Cp*Ir complex (Cp* is 1,2,3,4,5-pentamethylcyclopenta-1,3-diene) coordinated by bipyridine ligand bearing both dimethylamino and ortho-hydroxyl groups showed high catalytic activity for the reductive amination of LA. A range of primary amines, such as aromatic and benzyl amines, were readily converted to corresponding pyrrolidinones in good yields.

A highly efficient activated carbon supported cobalt based catalyst for Fischer-Tropsch synthesis was constructed. The catalyst was prepared by incipient wetness co-impregnation. The obtained catalyst was activated by multistep activation processes, which was composed of reduction of calcined sample in H2, syngas treatment, carburization in CO, and re-reduction in H2 successively. The multistep activation processes derived catalyst (CoZr/AC-RSCR) demonstrated far higher CO conversion and lower CH4 selectivity than those of conventional H2 reduction derived catalyst (CoZr/AC-R). The excellent performance of CoZr/AC-RSCR catalyst resulted from its higher amount of exposed active sites and the dominant hexagonal closed-packed (hcp) metallic cobalt phases. Furthermore, the catalytic performance could be further improved by tuning the content of hcp metallic cobalt phase stacking using the proper and effective treatment conditions of the multistep activation method. Finally, extremely high productivity of the mixture of alcohols and hydrocarbons with carbon number larger than 5 (194.6 g/h·kg-cat.) was acquired over CoZr/AC catalyst.

Breaking the recalcitrant structure of native crystalline cellulose is an energy demanding rate liming step in the production of glucose from cellulosic biomass. Mix-milling of lignocellulosic substrates (with P2O5) dramatically increased glucose yield. In this work, the changes of physicochemical characteristics (morphology, structure, degree of polymerization (DP), solubility) of cellulose during mix-milling (with P2O5) are correlated with glucose yield in the subsequent chemical hydrolysis process. The mix-milling enables highly efficient breakdown of cellulose I crystalline to smaller amorphous particles with low DP, which is recrystallized into cellulose II structure after water-wetting. As a result, the mix-milled cellulose (MMC) shows higher hydrolysis reactivity than that of single-milled cellulose (SMC). The results showed that small particle size, low DP, higher solubility and cellulose II content are correlated with the hydrolysis reactivity of cellulose.

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.

Diketones are ubiquitous blocks for organic synthesis. This work shows a highly active catalyst for the production of diketone 1-hydroxyhexane-2,5-dione (HHD) by hydrogenation of 5-hydroxymethylfurfural (5-HMF), a biobased platform chemical. Half-sandwich Cp*Ir complexes with ortho-hydroxyl group functionalized bipyridine ligands were synthesized and found to exhibit remarkably high catalytic activity for this reaction in acidic water. The HHD formation rate was further increased when the bipyridine ligands of Cp*Ir complexes were modified by an electron-donating group. A bipyridine ligand with both dimethylamino and ortho-hydroxyl groups achieved a HHD formation turnover frequency (TOF) of 31 560 h–1 by H2 and a TOF of 6140 h–1 by formic acid, representing 180-fold and 3 000-fold over the activities of the best reported results, respectively.

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 new method for one-step synthesis of ketones from biobased 5-hydroxymethylfurfural (5-HMF) and its derivatives is reported. Bipyridine coordinated Cp*-Iridium(III) complexes (Cp*, 1,2,3,4,5-pentamethylcyclopenta-1,3-diene) exhibit highly efficient catalytic performance for hydrogenation/hydrolytic ring opening of 5-HMF and derivatives to produce ketones. The catalytic mechanism is proposed to proceed via carbonyl hydrogenation, hydroxyl group promoted and directed hydrolytic furan ring opening, followed by hydrogenation of α,β-unsaturated carbonyl compound based on the experimental and independent events’ statistical calculation results.

The catalytic isomerization of aldoses to ketones is an important fundamental step for the transformation of cellulosic biomass to biobased chemicals and liquid fuels. The results of this work reveal for the first time the distinctive coordination chemistry features of four classes of metal chlorides, CrCl3, VCl3, FeCl3, and PtCl2 in 1-butyl-3-methylimidazolium chloride ([BMIM]Cl), that are well correlated to the drastically different catalytic performances of the metal chlorides in the isomerization of glucose. The relative bond strengths and the number of ligands to which the metal ions are coordinated by oxygen atoms of different sources and by chloride were studied by probing model compounds with in situ far-infrared (FIR) and by reaction studies. The superior performance of CrCl3 for this reaction is now distinguished from that of other metal chlorides, on the basis of its selective Cr(III) ene-diol coordination chemistry. We also offer new insights into the mechanism involved in the conversion of gl...

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.

In this work, new strategies involving organic bases were evaluated to depolymerize lignin to reduced molecular fragments in aqueous medium. NaOH as an inorganic base was also investigated as a reference. Full nature lignin samples were used for the study. As research tools to unravel the complexity of the macro lignin structure and bulky molecular size under this study, size exclusion chromatography and high resolution mass spectrometric analysis, typically used for protein characterizations, were used to follow the progress of lignin depolymerisation by measuring the molecular weight distribution of the products and determining the key molecular mass fingerprints, respectively. The results show that sodium phenoxide and guanidine carbonate are effective catalysts for lignin depolymerization. It is observed that the organic bases enhance the oxy-cleavage effect of H 2 O 2 , which is strongest with guanidine carbonate.

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.

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.

An effective reductive cleavage of inert aryl C—O bonds that employs iron(III) acetylacetonate as the catalyst precursor and LiAlH4 as the reducing agent is developed.

Ionic liquids with anions of strong hydrogen-bond basicity have been broadly reported in the literature as effective solvents for the dissolution of the components of lignocellulosic biomass. The key attributes of various ionic liquids are reviewed with a focus on their structural and functional properties related to biomass dissolution capacity. A number of the most studied ionic liquids with high solubility for cellulose and lignin have often been found not suited for catalytic conversions of these biomass components. Metal chlorides in chloride-based ionic liquids are robust catalyst systems for efficient cellulose and lignin conversions. Emerging leads in the literature related to the use of ionic liquids for catalytic conversions of cellulose, cellulosic carbohydrates, and lignin are discussed.

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.

The hydrolytic cleavage of β-O-4 ether bonds in lignin model compounds, guaiacylglycerol-β-guaiacyl ether (GG) and veratrylglycerol-β-guaiacyl ether (VG), was studied in 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) with metal chlorides and water. FeCl3, CuCl2, and AlCl3 were found to be effective and functioned catalytically in cleaving the β-O-4 bond of GG, although a number of other metal chlorides are considerably less active. AlCl3 functioned more effectively in cleaving the β-O-4 bond of VG than did FeCl3 and CuCl2. After 120 min at 150 °C, GG conversion reached 100%, and about 70% of the β-O-4 bonds of GG were hydrolyzed, liberating guaiacol, in the presence of FeCl3 and CuCl2, while about 80% of the β-O-4 bonds of GG were hydrolyzed in the presence of AlCl3 with 100% GG conversion. About 75% of the β-O-4 bonds of VG were hydrolyzed in the presence of AlCl3 after 240 min at 150 °C. The catalytic activity is associated with the hydrochloric acid, working as the acid catalyst, formed in situ by the...

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.

The catalytic performance of anion modified zirconia catalysts, such as sulfated zirconia (SO4/ZrO2) and tungstated zirconia (WO3/ZrO2), was evaluated for the upgrading of oleic acid (OA). In the presence of an aromatic compound, two main reactions occurred on the catalysts: the skeletal isomerization of OA and the arylation of OA with aromatics. The activity of the SO4/ZrO2 was more than triple of that of the WO3/ZrO2. At 250 °C, OA/(SO4/ZrO2)(wt/wt) = 5, the OA conversion and the arylation selectivity reached their maximal values and the isomerization selectivity was the lowest when the toluene to OA (toluene/OA) molar ratio was about 6. When mesitylene was used instead of toluene, the OA conversion and the arylation selectivity decreased, probably because of a steric effect. An attempt to reuse the SO4/ZrO2 by solvent washing after a run was not so successful, while calcination at 630 °C in air recovered the activity completely.

We report the synthesis of bis(hydroxylmethylfurfuryl)amine (BHMFA) from 5-hydroxymethylfurfural (5-HMF) by reacting 5-HMF with primary amines in the presence of homogeneous Ru(II) catalysts having sterically strained ligands. BHMFA is a group of furan-based monomers that offer great potential to form functional biopolymers with tunable properties. A range of primary amines, such as aliphatic and benzyl amines, are readily converted with 5-HMF to form the corresponding BHMFA in good yields. The reaction proceeds through reductive amination of 5-HMF with primary amine to form secondary amine, followed by reductive amination of 5-HMF with in situ generated secondary amine to produce BHMFA.

Catalytic aldose isomerization to ketose is an important reaction for the utilization of cellulosic biomass. However, a fundamental understanding and knowledge base involved in this reaction remains lacking in the literature. In this chapter, we provide a focused review of the most studied solvent-based catalytic system involving metal halides for glucose isomerization to fructose and further to 5-hydroxymethhylfurfral (5-HMF). Results from studies by different physical techniques are critically reviewed. A differentiation of the coordination chemistry of different metal chlorides obtained by various physical techniques is established to rationalize the drastically different catalytic pathways by the metal chloride catalysts. The performance of metal chloride catalysts for the isomerization of aldose to ketose is found to correlate with their coordination chemistry. Solvents play an important role in determining the coordination structures for the metal ions, which critically affect the catalysis of the metal chloride precursors. Undesired side products are related to the reaction pathways corresponding to the nature of the coordination of metal ions with different oxygen sources in the substrates and the products.

An unusual inverse temperature-dependent pathway was discovered for cellulose decrystallization in trifluoroacetic acid (TFA). Cellulose was completely decrystallized by TFA at 0 °C in less than 2 hours, a result not achieved in 48 hours at 25°C in the same medium. The majority of TFA used in cellulose decrystallization was recycled via a vacuum process. The small remaining amount of TFA was diluted with water to make a 0.5% TFA solution and used as a catalyst in dilute acid hydrolysis. After one minute, under batch conditions at 185 °C, the glucose yield reached 63.5% without production of levulinic acid. In comparison, only 15.0% glucose yield was achieved in the hydrolysis of untreated cellulose by 0.5% H2SO4 under the same condition. Further improvement of glucose yield is possible by optimizing reaction conditions. Alternatively, the remaining TFA can be completely removed by water while keeping the regenerated cellulose in a highly amorphous state. This regenerated cellulose is much more reactive than untreated cellulose in hydrolysis reactions, but still less reactive than corn starch. The lower temperatures and shorter reaction times with this activated cellulose makes it possible to reduce operating costs and decrease byproduct yields such as HMF and levulinic acid.

Replacing petroleum feedstocks by biomass requires efficient methods to convert carbohydrates to a variety of chemical compounds. We report the catalytic conversion of sugars giving high yield to 5-hydroxymethylfurfural (HMF), a versatile intermediate. Metal halides in 1-alkyl-3-methylimidazolium chloride are catalysts, among which chromium (II) chloride is found to be uniquely effective, leading to the conversion of glucose to HMF with a yield near 70%. A wide range of metal halides is found to catalyze the conversion of fructose to HMF. Only a negligible amount of levulinic acid is formed in these reactions.

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.

Two types of ionic liquids, 1-alkyl-3-methylimidazolium [AMIM] tetrafluoroborate and hexafluorophosphate and trimethylamine hydrochloride (AlCl3−TMAC), were demonstrated to be potentially applicable for sulfur removal from transportation fuels. EMIMBF4 (E = ethyl), BMIMPF6 (B = butyl), BMIMBF4, and heavier AMIMPF6 showed high selectivity, particularly toward aromatic sulfur and nitrogen compounds, for extractive desulfurization and denitrogenation. The used ionic liquids were readily regenerated either by distillation or by water displacement of absorbed molecules. The absorbed aromatic S-containing compounds were quantitatively recovered. Organic compounds with higher aromatic π-electron density were favorably absorbed. Alkyl substitution on the aromatic rings was found to significantly reduce the absorption capacity, as a result of a steric effect. The cation and anion structure and size in the ionic liquids are important parameters affecting the absorption capacity for aromatic compounds. At low concen...

The hydrolysis of β--O--4 bonds in two lignin model compounds was studied in an acidic ionic liquid, 1-H-3-methylimidazolium chloride. The β--O--4 bonds of both guaiacylglycerol-β-guaiacyl ether and veratrylglycerol-β-guaiacyl ether underwent catalytic hydrolysis to produce guaiacol as the primary product with more than 70 % yield at 150 °C. Up to 32 wt % substrate concentration could be treated in the system without a decrease in guaiacol production. The ionic liquid could be reused without loss of activity in guaiacol production from both guaiacylglycerol-β-guaiacyl ether and veratrylglycerol-β-guaiacyl ether. A possible mechanism accounting for the guaiacol production is presented.

Lignin depolymerization is a necessary process step in utilizing the carbohydrates in biomass and in potentially converting the lignin into a chemical feedstock. Lignin contains several aryl-alkyl ether linkages and the β-O-4 linkage is dominant among lignins. Base-mediated cleavage of the β-O-4 bond in a lignin model compound, guaiacylglycerol-β-guaiacyl ether, is reported. Ionic liquids have shown promise in a variety of biomass processes and this study explores the potential to use an ionic liquid solvent (1-butyl-2,3-dimethylimidazolium chloride) and non-aqueous bases in cleaving the β-O-4 bond. N-bases of varying basicity and structure were used at temperatures up to 150°C. The cleavage reaction was not found to be catalytic. Among all the tested N-bases, 1,5,7-triazabicyclo[4.4.0]dec-5-ene was the most active, leading to more than 40% β-O-4 ether bond cleavage, and the higher activity is probably associated with the exposed nature of the N-atoms.