Upgrading of biomass by bamboo vinegar-assisted wet torrefaction pretreatment for the highly production of bio-aromatics through catalytic fast pyrolysis

Bamboo vinegar (BV), as the waste liquid by-product during the bamboo carbonization process, was employed as the reaction solution during biomass wet torrefaction pretreatment (WTP) to upgrade the quality of poplar wood (PW) in terms of the deoxygenation and demineralization. Then, the catalytic fast pyrolysis (CFP) was carried out on torrefied PW to produce the value-added bio-aromatics using the Zn modified hierarchical HZSM-5. Results showed that the higher WTP temperature was favored for the synergistic deoxygenation and demineralization of PW with the maximum deoxygenation and demineralization rates of 48.68 % for O, 94.96 % for Na, 97.68 % for K, 77.45 % for Mg, and 82.73 % for Ca at 260 ºC. In addition, the model organic components (e.g., acetic acid and phenol) in BV had synergistic effect on promoting the demineralization rate, among which the acetic acid model component was the most effective one. During CFP, the parent HZSM-5 was modified by the different alkali treatments (NaOH, Na₂CO₃, and TPAOH (tetrapropylammonium hydroxide)) and the different loading amounts (1 _wt.% to 7 _wt.%) of Zn. It was found that the NaOH desilication treatment coupled with Zn loading amount of 3 % was the best combination to produce the highest yield of aromatics due to the suitable pore size and acidity. Furthermore, the mild BV-assisted WTP condition at 180 ºC coupled with CFP at 800 ºC with the catalyst-to-torrefied PW at 3:1 was the optimal condition for production of bio-aromatics with 34.32 %.