In-situ generated hydrogen for selective hydrogenolysis of lignin catalyzed by Mg-Al mixed oxides with nested Ni nanoparticles

Abstract

Conversion of lignin to valuable chemicals without external hydrogen presents a significative but challengeable endeavor. Herein, an efficient approach has been proposed for the lignin hydrogenolysis with in-situ hydrogen in the presence of Ni nanoparticles nested in layered double oxides (LDOs). 84.4 % conversion of lignin was achieved over 30Ni-Mg₃Al-LDOs, affording a 21.3 % yield of monomers, and 38.0 % of which was identified as 4-ethylphenol. Catalyst characterizations revealed that this excellent performance of lignin conversion should be ascribed to the highly dispersed Ni nanoparticles, strong interfacial interactions between Ni and LDOs, and suitable basicity of catalysts. Furthermore, the roles of the solvent (1,4-dioxane aqueous solution) and the lignin methoxyl groups as hydrogen resources were distinguished, and the former acted as an initial hydrogen to promote lignin depolymerization, and the latter was responsible for the high yield of 4-ethylphenol. In addition, a plausible reaction pathway for lignin hydrogenolysis has been proposed.