Upgrading of bio-oil from catalytic pyrolysis of pretreated rice husk over Fe-modified ZSM-5 zeolite catalyst

Catalytic pyrolysis of rice husk sample after combined washing-torrefaction pretreatment over Fe-modified ZSM-5 zeolite catalyst for bio-oil upgrading was investigated. This study shows the effects of Fe-modified ZSM-5 zeolite catalyst with different Fe loading and different pretreatment conditions from an integrated process of pretreatment and catalytic pyrolysis to improve the quality of bio-oil. The results indicated that with the increase of Fe loading, the yield of upgraded bio-oil decreased, while the relative content of hydrocarbons was enhanced obviously. The optimum Fe-modified ZSM-5 zeolite catalyst should be 4%Fe/ZSM-5 because excessive loading of Fe could affect the yield of upgraded bio-oil. Furthermore, it was found that during catalytic pyrolysis process with 4%Fe/ZSM-5, combined washing-torrefaction pretreatment had an obvious effect on promoting the production of hydrocarbons and further increasing the selectivity for BTX (benzene, toluene and xylenes), while severe torrefaction condition could significantly decrease the yield of upgraded bio-oil. Generally, combined washing-torrefaction pretreatment at mild torrefaction condition (210 and 240 °C in this study) was more suitable for upgrading of bio-oil from catalytic pyrolysis over Fe-modified ZSM-5 zeolite catalyst.