Effects of nano-structured CoMo catalysts on hydrodeoxygenation of fast pyrolysis oil in supercritical ethanol

Abstract

Effects of in-house prepared CoMo catalysts supported on various nano-structured materials (activated carbon, γ-alumina, HZSM-5, MCM-41 and SBA-15) and a commercial catalyst of Ru/C were compared for hydrodeoxygenation (HDO) of fast pyrolysis oil (PO) in supercritical ethanol at 300 and 350°C. All catalysts proved to be effective for significantly reducing the molecular weight of the PO by HDO treatment at 350°C. Although Ru/C catalyst produced the highest oil yield at both temperatures (66.6wt% at 300°C and 61.0wt% at 350°C) with the lowest and negligible coke formation (<1wt%), the catalyst is very expensive and difficult for regeneration, so it is not a viable catalyst for bio-oil upgrading on a large scale. Among all the supported CoMo catalysts, CoMo/MCM-41 produced the highest yield of oil products (light oil (OL)+heavy oil (HO)) of the highest H/C molar ratio. With this catalyst, the oil yield attained 61.9wt% at 300°C and 57.8wt% at 350°C, and the spent catalyst after regeneration produced almost the same oil yields as the fresh one. In addition, CoMo catalysts supported on MCM-41 and SBA showed better resistance to coke/carbon deposition in the HDO process, compared with CoMo catalysts supported on HZSM-5 and Al2O3.