The effect of potassium on the balance of metal–acid site in Pt/Al2O3 catalysts and their n-hexane dehydrogenation performance

Abstract

To reduce the side reactions and increase olefin selectivity in the dehydrogenation process, a series of low-loaded Pt-based catalysts supported on θ-Al₂O₃ (with or without potassium (K) modification) were prepared. The K modification effect on the n-hexane dehydrogenation performances of Pt/Al₂O₃ catalysts was investigated using various techniques. The added K species selectively occupied the strong acid sites on the Pt/Al₂O₃ surface, leading to not only the regulated surface acid properties but also the modified metallic function. Specifically, adding an appropriate amount of K reduced the number of acid sites and increased the electron cloud density of Pt sites, leading to enhanced selectivity and stability. Furthermore, the moderate amount of acid sites kept Pt highly dispersed and provided a suitable geometric structure, resulting in good activity. Herein, the Pt–0.8K/Al₂O₃ catalyst with suitable metal–acid site balance shows an n-hexane conversion of 25% with over 70% C₆ olefin selectivity. More importantly, a significantly low deactivation rate at 500 °C for 30 h is superior to most previously reported ones.