Effect of the combined pretreatment of leaching and torrefaction on the production of bio-aromatics from rice straw via the shape selective catalytic fast pyrolysis

Abstract In this study, three type of pretreatment methods (single pretreatment of leaching, single pretreatment of torrefaction, combined pretreatment of leaching and torrefaction) were employed to improve the quality of rice straw. Three leaching agents, namely acid solution, phenol solution, and simulated light bio-oil (SBO), were used. Then, in order to obtain higher yield of benzene, toluene, and xylene (BTX), the pretreated biomass was pyrolyzed using Py-GC/MS. Effects of combined pretreatment (leaching and torrefaction) and shape selective catalytic fast pyrolysis (SS-CFP) on the production of aromatics were investigated. Results showed that the combined pretreatments have advantages of the separate pretreatments, that is, deashing and deoxygenation. Synergistic effect was found between acids and phenols in SBO with respect to the removal of alkali and alkaline earth metal species (AAEMs) from rice straw. This promotes the generation of volatile substances, which are upgraded to produce BTX under catalysis of HZSM-5. Among the pretreated samples, torrefied–leached samples have the highest selectivity for BTX (64.6%). In conclusion, combined pretreatment of leaching and torrefaction was more effective to improve the yield of BTX than the single pretreatment of leaching or torrefaction.