Renewable lignin-based carbon nanofiber as Ni catalyst support for depolymerization of lignin to phenols in supercritical ethanol/water

Abstract

Lignin represents the most abundant source of renewable aromatic resources, and depolymerization of lignin has been shown to be a prominent challenge in the production of low-molecular-mass aromatic chemicals. Herein, we report the preparation of Ni/LCNF catalyst by which Ni nanoparticles were inlaid in lignin-based carbon nanofibers (LCNF) to improve stability of the catalyst and adjust the interaction between the metal and its support. We also present its use in lignin depolymerization. The use of 10%Ni/LCNF catalyst resulted in exceptionally high yields of light lignin fragments (87%) and phenols (7%). The average molecular weight (Mw) of light lignin residue was significantly lower than that of the untreated lignin, and there was clear evidence of lignin depolymerization. Preliminary recycling studies showed that the Ni/LCNF catalyst could maintain its activity for over three recycling cycles; its selectivity towards phenols remained unchanged. The present method, in which Ni nanoparticles were inserted or partially embedded in carbon materials to avoid Ni nanoparticle aggregation, sintering and loss during lignin depolymerization, is an alternative way that can be applied to maximize the utilization of lignin.