Insight into the noble-metal-free NiCoAl catalyst boosting the reductive esterification of furancarboxylic acid to methyl 2-tetrahydrofuroate

Abstract

Reduction of high oxidation level furancarboxylic acid (FA) with the retention of the carboxyl group is particularly important for the utilization, however, it has been rarely explored over non-precious catalysts and is challenging. Here, we demonstrate an excellent noble-metal-free trimetallic NiCoAl catalyst for the reductive esterification of FA to methyl 2-tetrahydrofuroate (MeTHFC), which delivers the complete conversion of FA and MeTHFC yield of up to 99%. More importantly, Ni0.5Co0.5Al could offer YMeTHFC > 90% over five reusability cycles. Detailed investigations suggest that the high activity originates from the synergistic of Ni-Co alloys sites and acid sites in Ni0.5Co0.5Al. The Ni-Co alloy sites were mainly responsible for the adsorption and dissociation of H2, which in turn improved hydrogenation activity, while the acid sites facilitated the esterification of FA and the adsorption and further activation of the furan ring. This work provides an eco-friendly noble-metal-free catalyst to enrich the strategies for the reductive esterification process.