In-depth study of synergism between torrefaction and catalyst for balanced production of bio-oil from rice husk pyrolysis based on hydrocarbons production, energy yield and deoxygenation degree

Abstract

Previous studies concerning biomass to bio-oil mainly focused on hydrocarbons production, and how to balance the bio-oil production in terms of hydrocarbons production, energy yield and deoxygenation degree is a challenging issue. After the pretreatment of torrefaction, catalytic fast pyrolysis (CFP) was performed at two-zone fixed-bed reactor. The synergism between torrefaction and catalyst during torrefaction-catalytic fast pyrolysis (T-CFP) was investigated for the balanced production of bio-oil from rice husk. Firstly, the results of two catalysts（ZrO2/n-ZSM-5 and ZrO2/n-ZSM-5/attapulgite) indicated that the catalyst with the incorporation of attapulgite (ATP) could realize the balance between the acid and basic sites, which resulted in deeper deoxygenation. Then, the results of torrefaction-catalytic pyrolysis showed that, among three torrefaction temperatures adopted, mild torrefaction (210 °C) had better synergistic effects with both catalysts. Specifically, catalytic pyrolysis of biomass after mild torrefaction over both catalysts realized the enhancement of deoxygenation degree and energy yield. Moreover, with the pretreatment of mild torrefaction, the performance of ZrO2/n-ZSM-5/ATP turned out to be obviously superior to ZrO2/n-ZSM-5 in terms of hydrocarbons production (7.5%＞0.8%) and deoxygenation mode. Therefore, the combination of ZrO2/n-ZSM-5/ATP and mild torrefaction could achieve more balanced production of bio-oil from T-CFP process.