Investigation on the cleavage of β-O-4 linkage in dimeric lignin model compound over nickel catalysts supported on ZnO-Al2O3 composite oxides with varying Zn/Al ratios

Abstract

Catalytic depolymerization of lignin is still a challenge due to its low conversion and repolymerization of the reactive intermediates. Reductive depolymerization over supported nickel catalysts with probable surface acidic and basic properties is a very promising process. It is therefore very important to investigate the effect of acidity and basicity of the supports on catalytic reactivity. In this paper, we synthesized a series of nickel based catalysts supported on ZnO-Al2O3 composites with varying Zn/Al atom ratios (Zn/Al=2, 3, 5, ∞) and tested their catalytic performances over a model compound 2-phenoxy-1-phenylethanone containing β-O-4 bond. All these catalysts showed 100% conversion by reacting at 250°C for 2h under 2MPa of H2. Higher selectivity towards ethylcyclohexane could be obtained over the catalyst Ni/ZnO-Al2O3-5. The possible cleavage pathways of selective oxidized β-O-4 ether linkage have been proposed.