Tarit Nimmanwudipong

Upgrading of lignin-derived bio-oils by catalytic hydrodeoxygenation

The incentive for use of renewable resources to replace fossil sources is motivating extensive research on new and alternative fuels derived from biomass. Bio-oils derived from cellulosic biomass offer the prospect of becoming a major feedstock for production of fuels and chemicals, and lignin is a plentiful, underutilized component of cellulosic biomass. Lignin conversion requires depolymerization and removal of oxygen. Likely processes for lignin conversion involve depolymerization (e.g., by pyrolysis) and catalytic upgrading of the resultant bio-oils. A major goal of the upgrading is catalytic hydrodeoxygenation (HDO), which involves reactions with hydrogen that produce hydrocarbons and water. The aim of this review is to present a critical introduction to HDO chemistry focused on compounds derived from lignin, including a summary of HDO reactions and those that accompany them, with a comparison of catalysts addressing their activities, selectivities, and stabilities. The reactions are evaluated in terms of reaction pathways of compounds representative of lignin-derived bio-oils, including anisole, guaiacol, and phenol. The review includes recommendations for further research and an attempt to place HDO in a context of options for renewable fuels and chemicals, but it does not provide an economic assessment.

Engineering Non‐sintered, Metal‐Terminated Tungsten Carbide Nanoparticles for Catalysis

Transition-metal carbides (TMCs) exhibit catalytic activities similar to platinum group metals (PGMs), yet TMCs are orders of magnitude more abundant and less expensive. However, current TMC synthesis methods lead to sintering, support degradation, and surface impurity deposition, ultimately precluding their wide-scale use as catalysts. A method is presented for the production of metal-terminated TMC nanoparticles in the 1-4 nm range with tunable size, composition, and crystal phase. Carbon-supported tungsten carbide (WC) and molybdenum tungsten carbide (Mo(x)W(1-x)C) nanoparticles are highly active and stable electrocatalysts. Specifically, activities and capacitances about 100-fold higher than commercial WC and within an order of magnitude of platinum-based catalysts are achieved for the hydrogen evolution and methanol electrooxidation reactions. This method opens an attractive avenue to replace PGMs in high energy density applications such as fuel cells and electrolyzers.

Effective hydrodeoxygenation of biomass-derived oxygenates into unsaturated hydrocarbons by MoO3 using low H2 pressures

Effective hydrodeoxygenation of biomass-derived oxygenates is achieved with MoO3 to produce unsaturated hydrocarbons, converting linear ketones and cyclic ethers to olefins, and cyclic ketones and phenolics to aromatics with high yields. The catalyst is selective for C–O bond cleavage and operates using low H2 pressures (≤1 bar). We show that deactivation can be minimised by tuning hydrogen partial pressure, that original activity can be recovered by calcination, and that catalytic activity can be maintained in the presence of water. Theoretical calculations are used to elucidate reaction pathways and highlight the role of oxygen vacancies in the deoxygenation process.

Catalytic conversion of compounds representative of lignin-derived bio-oils: a reaction network for guaiacol, anisole, 4-methylanisole, and cyclohexanone conversion catalysed by Pt/γ-Al2O3

The conversion of compounds representative of lignin and lignin-derived bio-oils (guaiacol, anisole, 4-methylanisole, and cyclohexanone), catalysed by Pt/Al2O3 in the presence of H2 at 573 K is described by a reaction network indicating a high selectivity for platinum-catalysed aromatic carbon–oxygen bond cleavage accompanied by acid-catalysed methyl group transfer reactions.