Recent applications of nickel and nickel-based bimetallic catalysts for hydrodeoxygenation of biomass-derived oxygenates to fuels

Abstract

The hydrodeoxygenation (HDO) of biomass-derived oxygenates to fuels is an effective way to reduce the negative environmental impact resulting from the dependence on fossil energy. However, the complexity in the feedstock compositions (e.g. acids, phenols, esters) and the presence of large amounts of water, cause significant challenges to the design of HDO catalysts. Nickel and nickel-based bimetallic catalysts have been extensively investigated for HDO due to their high activity and low price over the past years. Lots of valuable information about the structure of catalysts (e.g. active sites, synergy among various sites) and HDO reactions (e.g. reaction routes, kinetics) has been found. In this mini-review, we first summarize the preparation methods of nickel and nickel based bimetallic catalysts and the strategies to improve the HDO performance. The mechanisms and kinetics on HDO of typical oxygenates (aromatic oxygenates, furanic compounds, carboxylic acids and esters) over different catalysts are compared to reveal how the synergistic effects among different functionalities enhance the HDO performance. Solvent effects, the mutual influence among oxygenates and HDO of raw feedstocks over nickel and nickel-based bimetallic catalysts are discussed as well. Finally, we recommend several directions for further research on nickel and nickel-based bimetallic catalysts for HDO reactions.