Halloysite-Supported Cr-Based Catalysts for the CO2-Assisted Oxidative Hydrogenation of Propane

A series of chromium-based catalysts supported on halloysite/boehmite with varying Cr loadings (xCr/HNT/Al2O3, where x = 3, 5, and 7 wt %) were synthesized for the oxidative dehydrogenation of propane. The effects of calcination temperature (550–700°C) on the textural and structural properties of the supports were investigated. The support calcined at 550°C showed optimal properties, including a specific surface area of 143 m2/g, a pore volume of 0.26 cm3/g, and a crushing strength of 3.3 N/mm2. As the Cr loading and reaction temperature were increased, the selectivity toward the desired product (propylene) declined due to the intensification of side reactions such as cracking and hydrogenolysis, which produce methane, ethane, and ethylene. The optimum activity/selectivity balance was achieved with the catalyst that contained 5 wt % Cr. At 650°C this sample provided the highest propylene space-time yield (7.2 mol kg–1 h–1) and an optimal balance of propane conversion (40.7%) and propylene selectivity (66.2%).