Producing BTX aromatics-enriched oil from biomass derived glycerol using dealuminated HZSM-5 by successive steaming and acid leaching as catalyst: Reactivity, acidity and product distribution

We have investigated both the GTA (glycerol to aromatics) reaction routes and aromatic products distributions over a series of dealuminated HZSM-5 catalysts to produce BTX aromatics-enriched oil from biomass derived glycerol. As the acid site density in dealuminated HZSM-5 catalysts decreased, the induction period of GTA process became longer. The GTA reaction route was almost unaffected over HNO3 treated HZSM-5 catalyst. However, the liquid route of GTA procedure was enhanced while the gas route was restrained over steaming dealuminated HZSM-5 catalyst. The mild HNO3 treatment could preferentially remove the non-shape selective acid sites from HZSM-5 extra-framework, promoting BTX aromatics formation. In contrast, dealumination by harsh steaming transformed HZSM-5 framework tetrahedral Al species (FAL) into EFAl species, leading to a decrease in the BTX aromatics yields together with an increment in the yields of trimethylbenzene and durene. Furthermore, the steaming treatment created an intramesopore structure, which improved the diffusion property in the GTA process, resulting in an improved life span of dealuminated HZSM-5 catalyst. The successive steaming and HNO3 leaching over HZSM-5 could not only extract the EFAl species formed in 3 h 500 °C/HZSM-5 sample, reopening the EFAl-blocked micropores, but also create intracrystalline mesopores, as a consequence, non-shape selective catalytic side reactions and coking were restrained simultaneously during the GTA process, so the resulting catalyst produced BTX aromatics-enriched oil from biomass derived glycerol and exhibited significantly prolonged catalyst lifetime.