Bio-aromatics production from biomass by a two-step method of torrefaction and catalytic pyrolysis

Bio-aromatics is an important building blocks for preparation of the various industrial products which can be produced from the two-step method of torrefaction and catalytic pyrolysis. In this work, the effect of dry torrefaction pretreatment (DTP) and wet torrefaction pretreatment (WTP) on the properties of corn stalk (CS) were investigated. Then, the dual-catalyst catalytic fast pyrolysis (DC-CFP) was utilized to transform the treated CS into light aromatics by using the Al 2 O 3 and the metal (Zn, Ga, and Fe) modified hierarchical HZSM-5 as catalyst. Results indicated, WTP was effective in removing 50.23 % of the oxygen content in CS and 92.14 % of the AAEMs in comparison to DTP. DTP and WTP both favorved for the enhancement of production of light aromatics with the optimal temperature of 240ºC and 210ºC, respectively, but CFP of WTP-treated CS had higher yield of light aromatics compared to that of the DTP-treated CS due to the better quality and higher effective hydrogen-to-carbon ratio (H/C eff ) in WTP-treated CS. Among the three types of metal (Zn, Ga, and Fe) modified hierarchical HZSM-5 and the four types of metal oxides (Al 2 O 3 , SiO 2 , MgO, and CaO), the combination of the dual-catalyst of Al 2 O 3 and Zn modified hierarchical HZSM-5 (Zn/HZ-0.3 M) presented the best synergistic effect on producing the light aromatics. • Dry and wet torrefaction remarkably improve the quality of biomass. • High demineralization rate achieved after wet torrefaction pretreatment. • Mild dry and wet torrefaction temperature could obtain high yield of bio-aromatics. • Wet torrefied biomass yielded more aromatics than dry torrefied biomass. • Synergistic effect occurred between metal oxide and Zn-modified HZSM-5.