Hydrodeoxygenation of fast pyrolysis oil with novel activated carbon-supported NiP and CoP catalysts

Abstract

Catalytic hydrodeoxygenation (HDO) has been considered as a promising technical route to upgrade fast pyrolysis oil to liquid transportation fuels. In this work, a series of active and inexpensive catalysts were synthesized for bio-oil HDO, i.e., activated carbon (AC)-supported nickel phosphide and cobalt phosphide catalysts, with a metal/P molar ratio varying from 5/2, 3/2, 1/1, 1/2, 1/3. For comparison, AC-support pure metal catalysts without P were also prepared. Effects of phosphorus content on HDO performance of the catalysts were investigated on a 100 mL bench-scale reactor system using a wood-derived pyrolysis oil at 300 °C and initial hydrogen pressure of 50 bar for 3 h. The results showed that the properties of the upgraded bio-oils were greatly affected by the phosphorus content in both Ni and Co catalysts. The best performance seemed to be achieved with the catalysts at a metal/P molar ratio of about 3/2. Moreover, 0.5 wt% of Ru was further added to the catalysts at a metal/P molar ratio of 3/2 and to the pure metal catalysts. The addition of a small amount of Ru was found to markedly decrease the relative molecular weight of the upgraded bio-oils, and achieved high quality bio-oil products similar to that obtained with an expensive commercially available 5 wt% Ru/C catalyst.