A facile strategy to prepare ZSM-5-based composites with enhanced light olefin selectivity and stability in the HTO process

Abstract

In this study, the influence of different ZSM-5 composite materials (ASA, γ-alumina, η-Al₂O₃, SiO₂, and attapulgite) and their performance in the n-hexane catalytic cracking process in a fixed bed microreactor at 550 °C under atmospheric pressure was studied. XRD, FT-IR spectroscopy, NH₃-TPD, BET, FE-SEM, and TG analyses were performed to characterize the catalysts. The result of the n-hexane to olefin process indicated that the A2 catalyst (γ-alumina composition with ZSM-5) showed the highest conversion of 98.89%, highest propylene selectivity of 68.92%, highest yield of light olefins of 83.84%, and highest propylene to ethylene ratio of 4.34. The reason for the significant increase in all these factors and the lowest amount of coke in this catalyst is the use of γ-alumina, which increased the hydrothermal stability and resistance to deactivation, improved the acidic properties with a strong to weak acid ratio of 0.382, and increased the mesoporosity to 0.242. This study indicates the effect of the extrusion process and the composition and the major effect of the properties of this material on the physicochemical properties and distribution of the product.