Investigation on the mechanism of diffusion in mesopore structured ZSM-5 and improved heavy oil conversion

A large probe molecule, cumene, was chosen to study diffusion and adsorption on mesopore structured ZSM-5, using a high precision intelligent gravimetric analyzer. Compared with ZSM-5, a 2–3 order of magnitude increase in the diffusion coefficient of cumene was observed on the mesopore structured ZSM-5. The increased adsorption rate and the increased adsorption heat with increased cumene coverage, supported a mechanism of diffusion, phase transition, and re-arrangement of cumene molecules during the adsorption process on the mesopore structured ZSM-5. The introduced mesopores also decreased the diffusion–adsorption activation energy by a factor of 4.6. Consequently, although the amount of strong Brønsted acid sites decreased, the conversion of cumene on the mesopore structured ZSM-5 catalyst doubled compared to ZSM-5 catalyst, and the total light olefins yield increased by 2.47 wt% with Daqing heavy oil as a feedstock.