A comprehensive comparative study on SAPO-34 and ZSM-5 catalyst for the conversion of ethanol-to-light olefins

Abstract This study aims to compare the catalytic performance of ZSM-5 and SAPO-34 zeolite catalysts in the conversion of ethanol. Through experiments conducted at different temperatures (773 and 673 K), it was found that SAPO-34 initially exhibits superior propylene selectivity compared to ZSM-5. However, the propylene yield on SAPO-34 gradually decreases, while the ethylene yield increases with time on stream. Density functional theory calculations were employed for the investigation of the reaction mechanism. The results indicate that the SAPO-34 catalyst surface favors propylene desorption, which is beneficial for its initial high propylene selectivity. Nevertheless, the smaller pore structure of SAPO-34 limits the effective diffusion of products, leading to product accumulation within the pores and potentially causing catalyst coking and deactivation. By combining the experimental results with theoretical calculations, this study not only explored the selectivity difference between SAPO-34 and H-ZSM-5 in ethanol conversion reaction but also revealed the influence of different molecular sieve catalyst structures on product distribution and catalyst stability.