Catalytic reforming of cellulose pyrolysis volatiles over hierarchical HZSM-5: Mechanism of a protective effect of tetrapropylammonium (TPA+) during alkali treatment

A series of HZSM-5 with hierarchical pores was obtained by using a modified NaOH treatment method. This modification incorporated the use of tetrapropylammonium bromide. Furthermore, their catalytic performance for reforming of cellulose pyrolysis volatiles at 600 °C was investigated. TPAB-assisted alkali treatment increased the mesoporosity, relative crystallinity, and surface integrity of ZSM-5. Additionally, a significant portion of the acidic sites was preserved. The 0.1TPAB-0.2AT, treated with 0.1 M TPAB and 0.2 M NaOH, yielded the highest light aromatics at 156.9 mg/g. The coking resistance of the catalyst was also improved. Tetrapropylammonium (TPA + ) achieves surface protective desilication by selectively adsorbing Si(0Al) on the zeolite. Subsequently, the continuous adsorption of TPA + leads to mesopore formation within the zeolite. This continuous restriction on desilication limits the increase in mesopore volume, resulting in a relatively abundant and uniform distribution of smaller mesopores on ZSM-5. This mechanism holds promise for future synthesis of highly mesoporous ZSM-5.