Synergistic enhancement of bio-oil quality through hydrochloric or acetic acid-washing pretreatment and catalytic fast pyrolysis of biomass

Peanut shells were used as raw materials, and the synergistic effects of various acid pretreatments and catalytic pyrolysis for biomass were comprehensively studied. The results showed that the oil yield of 0.5 mol/L hydrochloric acid treatment was 44.75 wt%, and that of 0.5 mol/L acetic acid treatment was 43.40 wt%. The solid products decreased apparently after pretreatment. Acid-washing pretreatment and the subsequent catalytic pyrolysis of the pretreated biomass promoted the yield of aromatic in bio-oil. The yield of bio-oil gradually decreased while the gas yield increased with the increase of catalytic pyrolysis temperature. Ketones and anhydrosugars were also reduced in the bio-oil, while aromatics increased significantly, reaching the highest value of 19.62 wt% (0.5 mol/L hydrochloric acid treatment) and 19.30 wt% (0.5 mol/L acetic acid treatment) respectively at 600 ℃. Synergy effect facilitated the conversion of pyrolytic intermediates to gas and aromatics. Besides, the possible formation mechanism of bio-oil under different pyrolysis conditions is proposed. The study indicates the optimized combination could effectively improve the quality of bio-oil.