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.

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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 hydrolysis of the metal chlorides. A dehydration product and dimer products from GG were detected and proposed as the possible intermediate products in the GG reaction. One possible acid-catalyzed pathway accounting for the guaiacol production from GG is presented.

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.

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.

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A general direct reductive amination of bio-based 5-HMF with amines is catalyzed by a Ru-complex in ethanol solution under H2 pressure.

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 glucose to 5-hydroxymethylfurfural (5-HMF). In situ FIR is established as a powerful tool in the study of the coordination chemistry of metal complexes in ionic liquids.