Selective Hydrogenolysis of Lignin Catalyzed by the Cost-Effective Ni Metal Supported on Alkaline MgO

Abstract

Bulk chemicals produced from renewable resources are receiving considerable attention due to the increase in sustainable practices. In this study, a novel, efficient, and sustainable strategy has been proposed to produce versatile petroleum-based monophenols from the natural aromatic polymer, lignin, via the selective cleavage of its specific chemical linkages by a cost-effective catalyst, Ni/MgO. The results demonstrate that 93.4% of lignin is converted, yielding 15.0% monophenols in the presence of 20% Ni/MgO. Importantly, 42.3% of these volatile chemicals are found to be 4-ethyl phenol (the yield is 6.31%), a widely used fine chemical currently obtained from the petrochemical industry. Further comparative investigations on the raw and recovered lignin using heteronuclear single quantum correlation-nuclear magnetic resonance (HSQC-NMR), Fourier transform infrared (FT-IR), quantitative 13C NMR, and the alkaline nitrobenzene oxidation method reveal that the selective breakage of the ester bond between the p-hydroxyphenyl structural unit and the other fragments followed by decarboxylation is responsible for the good performance of the 4-ethyl phenol formation process. Therefore, the results of this work would provide new insights for producing value-added petrochemicals from renewable lignin.