Hydrogenolysis of Lignin and C–O Linkages Containing Lignin-Related Compounds over an Amorphous CoRuP/SiO2 Catalyst

Abstract

Efficient depolymerization of C–O linkages is essential for converting lignin into fuels and higher value-added chemicals. In this work, CoRuP/SiO2, an amorphous Ru-Co phosphide composite, was fabricated for the efficient hydrogenolysis of ether linkages. The 4–O–5 and α–O–4 linkages containing lignin-related compounds, such as diphenyl ether, benzyl phenyl ether, 3-methyl diphenyl ether, and dibenzyl ether, are selected as representatives of linkages in lignin. Under mild conditions, Ru-containing metallic phosphides have high-performance for the catalytic depolymerization of C–O linkages. Compared with other catalysts, CoRuP/SiO2 shows an outstanding selectivity for benzene and excellent efficiency in depolymerizing diphenyl ethers, yielding only a small amount of by-products. Furthermore, the total acidity shows a linear relationship with the hydrogenolysis reactivity in cleaving aromatic ether bonds. The mechanisms for the catalytic hydrogenolysis of 4–O–5 and α–O–4 bonds over CoRuP/SiO2 are proposed. Moreover, two-dimensional heteronuclear single quantum coherence nuclear magnetic resonance spectroscopic analysis demonstrates that CoRuP/SiO2 could effectively depolymerize C–O bonds of lignin. These dominant hydrogenolysis products from lignin have excellent potential in the production of high value-added drugs or pharmaceutical intermediates. The hydrogenolysis of lignin can be a highly efficient alternative to the existing method of lignin utilization.