In Situ Synergistic Catalysis by Nano-Ceo2 Oil Dispersoid Concerted with Zsm-5: Enhanced Catalytic Cracking for Light Olefins

Abstract

The metal modification of ZSM-5 by impregnation method has been widely researched and applied in industrial catalysis, but fundamental understanding of their structure-property relationships has still remained challenging, largely due to the cross influence from Brønsted and Lewis Acid Sites. Here, using the oil dispersed nano-CeO2 with surface modified in reactant hydrocarbon, we propose a method to strengthen the Brønsted acid in situ during catalytic cracking reaction, wherein the monoatomic Ce incorporated with ZSM-5 was observed. The material morphological evolvement and quantitative description of acid properties tuning were investigated to bridge the Ce deposition analytics and the mechanism exploration for activity promotion. Combining with the reaction kinetics study, this strategy was found to significantly promote the carbonium ion generation step in protonation (rate limit step) with much less load of Ce, lowered the apparent activation energy of ethylcyclohexane catalytic cracking by 41.1% without the influence from Lewis acid variation, and foregrounded the development of advanced zeolite modification mode for light olefins production. The molecular simulation revealed the insights of how polyvalent monoatomic Ce regulated the bond strength of AlO-H, and enhanced the proton donating ability of zeolite.

Keywords: nano-CeO2 oil dispersoid, monoatomic dispersion, zeolite modification, Brønsted acid tuning, HC protonation, proton donation