Hydrogenation of phenol by defective ZSM-5 supporting Ni catalyst to produce cyclohexanol

Abstract

Cyclohexanol is an essential intermediate in the chemical industry, which can be produced from hydrogenation of phenol. In this work, a defective ZSM-5 zeolite supporting Ni catalyst (Ni/D-ZSM) is prepared by sequenced nitric acid treatment, impregnation, and reduction. In conversion of phenol, the highly dispersed Ni with strong interaction with the defective Si-OH delivers relative higher adsorption and spillover of active hydrogen, thus promoting the hydrogenation of phenol. Moreover, owing to the unique coordination environment of Ni in defective ZSM-5 zeolite with moderate acid properties, the desorption of intermediate cyclohexanol is promoted. The turnover frequency (TOF) calculated based on the yield of cyclohexanol and amount of metal reveals that, the Ni/D-ZSM sample by 48 h acid treatment (Ni/D-ZSM-48) delivers TOF values up to 17.73 × 10-3·s−1. The designed Ni/D-ZSM-48 catalyst with relative low Ni loading of ∼ 5 wt% delivers equivalent (slightly higher) production rates of cyclohexanol with the ever-reported noble-metal samples (Rh, Ru etc.) and significantly higher than the transition-metal based catalysts.