Enhancement of the production of bio-aromatics from bamboo pyrolysis: Wet torrefaction pretreatment coupled with catalytic fast pyrolysis

Light aromatics are important organic building blocks in the chemical industry which can be produced by catalytic fast pyrolysis (CFP) of biomass. In this work, wet torrefaction pretreatment (WTP) was employed to improve the quality of bamboo by synergistic effect of deoxygenation and demineralization. Then, CFP was employed to produce bio-aromatics by using zeolite (e.g. HZSM-5, HY, Al-MCM-41, and USY) as catalyst. Results showed that WTP temperature (180–260 °C) had more significant influence on the mass yields of torrefied products compared to WTP duration (30–150 min). The maximum deoxygenation rate was 49.36% at WTP conditions of 260 °C and 150 min, and the maximum demineralization rate followed the order of 96.29% (K) > 94.54% (Na) > 90.33% (Mg) > 89.22% (Ca). Among the five types of zeolite catalyst tested, HZSM-5 (25) was the best catalyst to obtain bio-aromatics due to its unique pore size and reasonable acidity. The maximum yield of aromatics (25.46 ×107 a.u./mg) was obtained at the WTP temperature of 220 °C, biomass-to-catalyst ratio of 3:1, and CFP temperature of 850 °C. Toluene was the more favored monocyclic aromatic hydrocarbon formed during CFP compared to xylene and benzene.