Catalytic hydrodeoxygenation of anisole as lignin model compound over supported nickel catalysts

Abstract

Catalytic hydrodeoxygenation (HDO) of anisole, a methoxy-rich lignin model compound, has been investigated over a series of Ni-containing (10wt% loading) catalysts with activated carbon, SBA-15, SiO2, and γ-Al2O3 supports, in order to understand their ability for removal of OCH3 from anisole. This catalytic reaction had been carried out in an autoclave at 180–220°C and 0.5–3.0MPa H2 pressure. Nickel-catalyzed aromatic ring-hydrogenation compared with the subsequent demethylation and deoxygenation is the fastest step in HDO of anisole under the present reaction conditions. Among these catalysts, the aromatic ring-saturated cyclohexyl methyl ether is mainly obtained over Ni/AC, while the Ni/SiO2 displayed the highest activity in HDO of anisole (selectivity to deoxygenated products >95%). Differences in HDO efficiency among the catalysts are attributed not only to variations in the dispersion of the active phase, but also to the acid sites which may contribute to the cleavage of CO bonds. It has also been shown that the activity toward oxygen-removal strongly depended on reaction temperature and the conversion of anisole favors the production of oxygen-free aromatics by the direct demethoxylation pathway at the relatively low H2 pressure.