Active Zn Species Nest in Dealumination Zeolite Composite for Propane Dehydrogenation.

Propane dehydrogenation (PDH) has attracted the attention of numerous researchers because of its great potential industrial value. But the existing industrial catalytic systems used metals are environmental unfriendly or expensive such as Cr- and Pt- based catalysts. Herein, a series of catalysts with different contents Zn loading on zeolite composite composed of Beta and Mordenite (named as BMZ) were prepared, and XRD, UV–vis, SEM, TEM, NH3-TPD, N2 adsorption–desorption measurement, 29Si NMR, XPS and FT-IR were employed to characterize the physicochemical properties of the as-prepared catalysts. The results display that as compared with the BMZ, dBMZ (obtained from BMZ by acid treatment) serving as a carrier contributes to giving well-dispersed Zn species with framework Zn and ultrasmall Zn nanoclusters. The interaction between the silanol nest formed by dealuminization resulted from the acid treatment and the metal zinc species, not only realizes the active metal high dispersion and anchoring, but also endows the active metal sites with excellent properties for sintering resistance and renewability. As a typical representative, dBMZ-15 catalyst (loading 15% Zn on dBMZ) shows excellent catalytic performances in PDH with a propane initial conversion of 38.6% and an average propylene selectivity more than 80%. The results also exhibit dBMZ-x has a good renewability for three successive PDH cycles at 530 ℃, and further suggest an excellent PDH catalyst for potential industrial application. Dealumination by acid treatment results in the formation of a large number of silanol nests, which reacts with Zn precursors and promotes the formation of framework Zn species. The introduced mesopores by acid treatment also contributes to the formation of ultra-small Zn nanoclusters. The Zn species anchored in framework or confined in hierarchical pores not only help to improve the catalytic performances for high catalytic activity along with high propylene selectivity, but also to offer the catalyst with a high resistance sintering and renewability during PDH. [ABSTRACT FROM AUTHOR]