(20c) CO2 Assisted Oxidative Dehydrogenation of Propane to Propylene over Fluidizable MoO3/La2O3-?Al2O3 Catalysts

This study investigated the catalytic performance of a novel fluidizable MoO₃ supported on La₂O₃-γAl₂O₃ composite for oxidative dehydrogenation (ODH) of propane to propylene with and without CO₂. The La₂O₃-γAl₂O₃ composites were synthesized by a coprecipitation method, while the active MoO₃ was deposited by an incipient wetness impregnation approach. The incorporation of La₂O₃ controlled both the acidity and reducibility of the catalysts, as revealed by NH₃-TPD and H₂-TPR analysis, respectively. The N₂ adsorption/desorption isotherms analysis indicated the mesoporous pore size distribution of the catalysts. The ODH of propane experiments were developed in a fluidized CREC Riser Simulator by feeding propane with or without CO₂. The performance of the synthesized catalysts was found to be a function of the La₂O₃ content of the support. In general, the propane conversion declined slightly, while propylene selectivity increased with the increasing La₂O₃ content. It was hypothesized that the presence of basic La₂O₃ reduced the acidity and the non-selective sites of γ-Al₂O₃, which were responsible for deep oxidation of propylene and propane. Among the studied catalysts, MoO₃/La₂O₃-γAl₂O₃1:2 displayed the highest propylene yield of 28.2 % at 600 ℃ in the absence of CO₂. However, a superior yield of 35.2% was achieved over the same catalyst by the introduction of CO₂-admixture in the feed at 550 ℃.