Demetallation and reduction induced ultra-dispersed PtZn alloy confined in zeolite for propane dehydrogenation

Abstract

Developing efficient bimetallic Pt-based catalyst is highly desired for propane dehydrogenation (PDH) process. Typical co-impregnation method often results in inhomogeneous distributions of metal species on supports. Herein, we reported a facile method to support PtZn bimetal alloy nanoparticles onto Beta zeolite, mainly existing as highly dispersed Pt1Zn1 alloy species. Zn@Beta was first synthesized by hydrothermal method with the aid of ethylenediamine (EDA), leading to the introduction of Zn atoms into zeolite lattice. An impregnation process was subsequently employed to support Pt species. During this process, skeleton Zn atoms migrated out of the framework and were then reduced together with Pt in flowing H2, leading to the formation of PtZn alloy with mainly Pt1Zn1 structures. Cs-corrected high-angle annular dark-field scanning transmission election microscope and X-ray absorption fine structure analyses revealed that this method was more conducive to the formation of PtZn alloy compared with the co-impregnation method. The obtained catalyst of 0.3Pt1Zn@Beta exhibited initial propane conversion of 36.8% and propylene selectivity of 99.3% combined with low deactivation rate (0.004 h–1) over 24 h with propane WHSV of 4.7 h–1 at 550 °C. The catalyst also exhibited good PDH performance in a long-term reaction (180 h) and robustness during regeneration reactions by simply flushing hydrogen.