Decoupling reaction network and designing robust VOx/Al2O3 catalyst with suitable site diversity for promoting CO2-mediated oxidative dehydrogenation of propane

Abstract

Detailed thermodynamic analysis was utilized to decouple the complex reaction network of CO2-mediated oxidative dehydrogenation (CO2-ODH) of propane and unravel critical catalyst design requirements. Inspired by the unmatched ability of boron-based catalysts in limiting cracking and overoxidation reaction pathways, we exploited controlled integration of both VOx and BOx active phases onto a γ-Al2O3 support and constructed a highly efficient CO2-ODH catalyst via scalable mechanochemical synthesis route. The solvent- and template-free synthetic design strategy regulated crucial properties of the catalysts and endowed suitable site diversity as evidenced from N2-adsorption analysis, XRD, HRTEM, Raman analysis, NH3-TPD, H2-TPR, and UV–Vis diffuse reflectance spectroscopy. Consequently, excellent propane conversion and propylene yield of 61 and 34 % respectively over 12 h time on stream (TOS) at 650 °C were realized with a catalyst composed of 5 wt% vanadium and 7 wt% boron. In situ DRIFT measurement revealed insight into the dynamic changes on the catalyst surface and the corresponding evolution of reaction intermediates during the CO2-ODH process. Overall, the thermodynamic investigation re-emphasized the critical importance of effective kinetic control while the synthetic protocol illustrated a promising avenue for rational design of CO2-ODH catalysts to harness the unique advantages of boron and metal oxide-based catalysts simultaneously.