Enhanced selectivity of propylene in butylene catalytic cracking over WZSM-5

摘要

W-ZSM-5 was synthesized by steam-assisted crystallization (SAC) method and used in butylene cracking. From the results of XRD, BET, NH3-TPD, SEM, Si-29 MAS NMR, Py-IR, UV-vis and H-2-TPR, we can conclude that most of tungsten are incorporated into framework of zeolite, and the prepared zeolites with the mole ratio of silicon and tungsten from 45 to 180, show high crystallinity. Compared with traditional ZSM-5, W-ZSM-5(90) exhibits similar textural and morphology properties and comparable acidity. But the introduced tungsten is in favor of the metathesis of ethylene and butylene to produce propylene. Thus, the conversion of butylene and the selectivity of propylene increased at the same reaction condition. Even though the selectivity of ethylene decreased, the side reactions were suppressed. W-ZSM-5(45) achieved the highest conversion (96 wt%) and selectivity of propylene (37 wt%). Fortunately, total yield of ethylene and propylene (55 wt%) over W-ZSM-5(45) is also the highest one among all tested catalysts, can be used as industrial catalyst for enhancing propylene yield.