Catalytic demethoxylation of lignin-derived alkylmethoxyphenols into alkylphenols over FeNi3/FeNi8O9.25 catalyst.

The hydrodemethoxylation (HDMO) of lignin-derived monophenolics to alkylphenols is a crucial step for the conversion of lignin bio-oil into chemicals. A new FeNi3 alloy catalyst was firstly prepared by being reduced in-suit from Fe, Ni oxides precursor. The FeNi3/FeNi8O9.25 catalyst prepared using optimal 12:88 of molar ratio of iron nitrate to nickel nitrate showed good catalytic activity and selectivity to HDMO of lignin-derived monophenolics. In the HDMO process of lignin-derived 4-propylguaiacol, FeNi3/FeNi8O9.25 contributed to a 94.53 % of conversion and a 90.67 % of demethoxylation selectivity under 0.4 MPa H2 at 280°C for 2 h. Compared with the Ni/Ni1O catalyst, the FeNi3/FeNi8O9.25 catalyst increased by 6.19 times and 2.35 times of the specific surface area and total acid amount, respectively. FeNi3(111) possessed lower adsorption energy to substrate and changed adsorption configuration of the benzene ring in tilted mode. Consequently, prepared catalyst facilitated the removal of methoxy group, as well as suppressing hydrogenation saturation of the benzene ring. Moreover, FeNi3/FeNi8O9.25 catalyst exhibited versatile capacity of HDMO to different lignin-derived monophenolics and high stability. This work offers a new strategy for constructing non-noble metallic alloy catalyst for highly selective HDMO reactions.