Two-step catalytic conversion of lignocellulose to alkanes

Abstract

Direct conversion of lignocellulose to alkanes is challenged by the complex and recalcitrant nature of the starting material. Generally, alkanes are obtained from one of the main lignocellulose constituents (cellulose, hemicellulose or lignin) after their separation, and platform chemicals derived therein. Here we describe a two-step methodology, which uses unprocessed lignocellulose directly, targeting a mixture of alkanes. The first step involves the near-complete conversion of lignocellulose to alcohols, using a copper doped porous metal oxide (Cu-PMO) catalyst in supercritical methanol. The second step comprises a novel solvent exchange procedure and the exhaustive hydrodeoxygenation (HDO) of the complex mixture of aliphatic alcohols, obtained upon depolymerization, to C 2 -C 10 alkanes by either HZSM-5 or Nafion at 180 C in conjunction with Pd/C in dodecane. This describes an unprecedented two-step process from lignocellulose to hydrocarbons, with an overall carbon yield of 50%.

Copper-nickel mixed oxide catalysts from layered double hydroxides for the hydrogen-transfer valorisation of lignin in organosolv pulping

“…Cu-bearing porous metal oxides (PMO) formed by the calcination of layered double hydroxides (LDH) have been presented as effective catalysts for the depolymerisation of lignin in supercritical methanol [38][39][40]. These materials have also been proved effective in catalytic transfer hydrogenolysis of lignocellulosic biomass, furfural, 5-hydroxymethylfurfural, and ethanol Guerbet reaction to butanol [41][42][43][44][45]. Supercritical methanol was often used in previous studies of hydrogen transfer on biomass components [46][47][48].…”

Boosted Hydrodeoxygenation of Lignin-Derived Phenolics to Cycloalkanes with a Complex Copper Acid Catalyst

“…Two processes are primarily involved in the conversion of lignin to cyclohexanes. First, the highly integrated raw lignin material is depolymerized into aromatics with smaller molecular weights through the selective cleavages of the particular linkages within lignin frameworks (e.g., β-O-4, α-O-4, and 4-O-5). − Then, the aromatics are saturated with hydrogen, accompanied by the removal of the attached oxygen-containing functional groups (e.g., hydroxyl, methoxyl) through the hydrode­oxygenation (HDO) reactions, which is referred to as the upgrading of lignin derivatives. ,,, In comparison with lignin depolymerization, the upgrading of lignin-derived aromatics involves more complicated reaction networks, with higher requirements for the effectiveness, stability, and compatibility of the catalytic system. ,, In this context, a variety of catalytic systems have been developed for the upgrading of lignin derivatives. For example, Shafaghat et al.…”

Enhanced Upgrading of Crude Lignin Bio-Oil to Jet Fuel Precursors with a Moderate Organic Acid-Modified Copper Catalyst

“…1,5,6 Afterward, hydrodeoxygenation (HDO) of crude bio-oil is performed to improve its properties as fuels via saturating the aryls and removing the oxygen-containing functional groups (mainly hydroxyl and methoxyl). 1,7 The depolymerization of lignin can be achieved by many means, including hydrogenolysis, oxidation, pyrolysis, hydrolysis, enzymolysis, etc. 1 However, the further upgrading of crude bio-oil can only be accomplished through the HDO process, which involves more complicated reaction pathways and thus raise higher requirements for the activity, stability, and compatibility of the catalytic system.…”

“…The transformation of lignin to cycloalkanes and cycloalcohols primarily involves two processes. The highly integrated raw lignin is first depolymerized into crude bio-oil via the selective cleavage of C–O and C–C linkages between lignin interunits. ,, Afterward, hydrodeoxygenation (HDO) of crude bio-oil is performed to improve its properties as fuels via saturating the aryls and removing the oxygen-containing functional groups (mainly hydroxyl and methoxyl). , The depolymerization of lignin can be achieved by many means, including hydrogenolysis, oxidation, pyrolysis, hydrolysis, enzymolysis, etc . However, the further upgrading of crude bio-oil can only be accomplished through the HDO process, which involves more complicated reaction pathways and thus raise higher requirements for the activity, stability, and compatibility of the catalytic system. , In these regards, the design and development of high-performance catalytic systems for the HDO of crude lignin bio-oil are particularly important for the efficient conversion of lignin to fuels.…”