Impact of acid washing and torrefaction on biomass pyrolysis characteristics and product distribution

Abstract

This work examined a new coupled pretreatment method was investigated, namely, coupled pretreatment by aqueous phase bio-oil (APBO) acid washing and torrefaction, aimed at enhancing the quality of bio-oil and improving hydrocarbon selectivity during catalytic fast pyrolysis (CFP) of wheat straw. The experimental results showed that APBO was more effective in removing AAEMs compared to acetic acid, the removal of K was as high as 98.77 %. Torrefaction, on the other hand, decreases the O content and the O/C molecular molar ratio. Thermogravimetry analysis (TGA) results showed that the coupled pretreatment method raised the maximum loss rate of the samples suggesting the promotion of cellulose and hemicellulose pyrolysis. Coupled pretreatment resulted in a decrease in acids and ketones and an increase in sugars and phenols in the pyrolyzed bio-oil. Upon adding the HZSM-5 catalyst after the coupled pretreatment, hydrocarbon production was significantly enhanced, leading to an increase in hydrocarbon yield from 28.06 % in the original sample to 49.5 % in the coupled pretreated sample. This coupled pretreatment method presents a novel approach for achieving high-quality and selective bio-oil conversion during CFP of biomass.