TiO2-Supported catalysts with ZnO and ZrO2 for non-oxidative dehydrogenation of propane: mechanistic analysis and application potential

Abstract

Non-oxidative dehydrogenation of propane is one of the most promising technologies for propene production in terms of environmental impact and sustainability. The purpose of the present study was to develop environmentally friendly and low-cost alternatives to currently applied Pt- or CrO_x-based catalysts. Rutile TiO₂-based catalysts with supported ZnO_x and ZrO_x species were established to show promising performance under industrially relevant conditions. The amount of propene produced within 3 h on propane stream at 550 °C over the optimized catalyst with 2 wt% Zn and 5.6 wt% Zr is close to that obtained over commercial-like K–CrO_x/Al₂O₃ and the state-of-the-art Cu/YZrO_x catalyst. The selectivity to propene over our catalyst was about 95% at a propane conversion of about 23%. The kind of active sites and the effect of ZrO₂ addition on catalyst performance and physicochemical properties were elucidated owing to the application of complementary characterisation techniques such as XRD, N₂ physisorption, HRTEM, EDX, XPS, X-ray absorption spectroscopy, NH₃-TPD, CO-TPR, Raman and O₂-TPO. ZnO_x clusters with 1–3 Zn atoms were concluded to be the active sites. ZrO₂ enhances their intrinsic activity and inhibits the formation of the inactive rhombohedral ZnTiO₃ phase.