Preparation of various hierarchical HZSM-5 based catalysts for in-situ fast upgrading of bio-oil

Abstract

Hierarchical HZSM-5 zeolites were prepared by desilication of commercial HZSM-5 in aqueous NaOH solutions with the assistance of tetrapropylammonium hydroxides (TPAOH), and applied for the catalytic upgrading of bio-oil derived from the fast pyrolysis of sunflower stalk. The hierarchical HZSM-5 by using 0.2 M NaOH with 0.25 M TPAOH for the desilication exhibited the best catalytic performance and the relative total peak area related to the aromatic hydrocarbons reached 65.8% with a yield of the detected aromatic hydrocarbons up to 45.2 mg/g-bio-oil. With the assistance of 0.25 M TPAOH for the desilication, the formation of mesopores became highly controllable, resulting in the increase in the surface area and maintainment of enough acid amounts, however, the coking on the surface of catalyst was not hindered. To solve the coking problem and increase the aromatic hydrocarbons production, the hierarchical HZSM-5 with the best performance was modified by various metals. It is found that 0.25 wt% Cu loaded hierarchical HZSM-5 increased the yield of the detected aromatic hydrocarbons up to 54.5 mg/g-bio-oil with a decrease in the coke formation.