Ni–Al/CoOx-catalyzed hydrodeoxygenation of 5-hydroxymethylfurfural into 2,5-dimethylfuran at low temperatures without external hydrogen

Abstract

Catalytic hydrodeoxygenation of 5-hydroxymethylfurfural into 2,5-dimethylfuran has received great interest in recent years. In this work, a ternary Ni–Al/CoOx-1 catalyst was fabricated, which provided 96% yield of DMF from in situ hydrodeoxygenation of HMF under mild reaction conditions. XRD, TEM and TPR revealed that the addition of Al to the Ni–Co bimetallic system could make the structure more stable and improve the dispersion of Ni and Co species. XPS, CO-DRIFTS and EPR verified that an enhanced electron transfer from Co species to Ni occurred on Ni–Al/CoOx-1. Reaction mechanism studies unraveled that the Al addition results in promoting in situ H₂ production from 2-propanol and accelerating the aldehyde group hydrogenation to a hydroxymethyl group and the subsequent hydrogenolysis into a methyl group, due to the formation of a charge separated metal-couple-site (Ni^δ−–Co^δ+) and stronger Lewis acid sites in Ni–Al/CoOx-1. In addition, this ternary Ni–Al/CoOx-1 catalyst exhibits superior recyclability without significant loss of activity for 7 cycles.