Insight into the catalytic mechanism of N-doped carbon nanotubes supported CoNi bimetallic catalyst boosts the base-free oxidative esterification of furfural

Abstract

Developing active and affordable catalysts for the transformation of biomass platform into value-added chemicals have drawn tremendous attention. Herein, we have successfully prepared a CoNi bimetallic nitrogen-doped carbon nanotubes (CNTs) catalyst, manifesting outstanding catalytic performance for furfural oxidative esterification under base-free conditions (methyl furoate yield >99%), and great recyclability (5th recycle). Importantly, an impressive methyl furoate formation rate of around 1980 μmolmethyl furoate·gcat−1·h−1 was achieved, to the best of our knowledge, the result represents one of the highest methyl furoate formation rates. The results revealed that the doping of Ni into the CoxNiy-CNTs catalyst brings about more active sites. Fourier transforms infrared spectrometer results suggest that the Ni-Nx sites are responsible for the adsorption of the substrate with tilted or vertical adsorption. Furthermore, the introduction of Ni facilitates the improvement of basicity, which in turn promotes the β-hydride elimination. All of these active sites boost the overall activity of the catalyst for the oxidative esterification of furfural.