Facile synthesis of hierarchical nanocrystalline H[Fe,Al]ZSM-5 with boosted lifetime for DTG reactions

Abstract

Dimethyl ether to gasoline (DTG) process is an important way to obtain transportation fuels from non-petroleum routes due to the ever-decreasing fossil energy under “dual-carbon” background, and the development of catalyst with long lifetime remains an important challenge. Herein, the hierarchical nanocrystalline H[Fe,Al]ZSM-5 zeolites composed of loosely aggregated nanocrystals were prepared by adding a mesoporous template and prolonging the aging time, and their physicochemical properties and reactivity over the DTG reaction were investigated and compared with that of conventional H[Fe,Al]ZSM-5. The size of individual nanocrystals became smaller and more uniform, and the nanocrystals were loosely aggregated with abundant intercrystal mesopores, resulting in the significant enhancement of catalyst lifetime. Furthermore, the acid intensity of hierarchical nanocrystalline zeolites weakened, and the strong acid amount was reduced. DTG reaction results illustrated that the hierarchical nanocrystalline zeolite of Mes-ZSM-5 using a mesoporous template exhibited the longest lifetime (182 h) with 100% DME conversion, and gasoline yield remained more than 70%. Moreover, the C₅⁺ selectivity was up to 76.6%; meanwhile, the contents of aromatics, benzene and durene were as low as 40%, 0.6% and 1.7%, respectively. The obtained gasoline product had a higher RON (research octane numbers).