Bimetallic Ni-Re catalysts for the efficient hydrodeoxygenation of biomass-derived phenols

Abstract

The development of non-noble metal-based catalysts for the hydrodeoxygenation (HDO) upgrading of biomass pyrolysis oils is crucial for realizing the cost-effective biofuel production. In this paper, we report on the enhanced HDO activity of the rhenium-promoted nickel catalysts (Ni-Re) for the HDO of a pyrolysis oil model compound, guaiacol. The catalyst screening studies revealed that the Ni-Re displayed a considerably higher HDO activity than other monometallic (Ni, Re, Cu, Co) and bimetallic catalysts (Cu-Re, Co-Re), highlighting its unique catalytic property. In order to optimize the catalytic activity and reveal the structure-activity relationship of the Ni-Re catalysts, the effects of the Ni/Re ratio and type of support (SiO2, TiO2, and ZrO2) on the catalyst structure and HDO activity were investigated in detail. The results showed that the addition of rhenium to nickel altered both geometric and electronic structures of nickel significantly. The Ni-Re/SiO2 catalyst with a Ni/Re ratio of 0.315 achieved similar to 95% yield of the desired deoxygenation product, cyclohexane, at 523 K and 30 bar-H-2 after 5 hours. Novelty Statement The upgrading of biomass pyrolysis oils to hydrocarbon fuels oftentimes requires the use of noble metal catalysts and harsh reaction conditions (e.g., high H-2 pressure), all of which greatly increase the process cost. In this work, a highly active and nonprecious metal-based catalyst, bimetallic Ni-Re/SiO2, is developed for the cost-effective upgrading of biomass-derived phenols to deoxygenated hydrocarbon fuels at low temperature and low pressure.