Properties of CrO_x/MCM-41 and Its Catalytic Activity in the Reaction of Propane Dehydrogenation in the Presence of CO₂

Propylene is an important raw material for the production of many valuable compounds, especially polypropylene, the consumption of which continues to grow every year. The reaction of oxidative dehydrogenation of propane, where carbon dioxide is used as a mild oxidant, is a promising method for producing propylene. At the same time, the problem of utilization of greenhouse gas CO2 is partially solved. The synthesis and analysis of the physicochemical properties of mesoporous silicate MCM-41 and supported catalysts CrOx/MCM-41 prepared on its basis were carried out. These catalysts were prepared using incipient wetness impregnation. The support and catalysts were characterized by the methods of low-temperature nitrogen adsorption, TG-DTA, XRD, SEM, TPR-H-2, UV/Vis diffuse reflectance spectroscopy, and small-angle X-ray scattering. It is shown that chromium is present in the samples simultaneously in the form of Cr3+ and Cr6+. The catalytic tests were performed in the range of 550-700 degrees C. The highest selectivity for propylene was observed for the 5%Cr/MCM-41 catalyst and was 76% at a temperature of 650 degrees C with a propane conversion of 20%. The deposited catalysts Cr/MCM-41 and Cr/SiO2 (Acros) were compared. The propylene selectivity for the MCM-41-supported catalyst was similar to 1.5 times higher than that for the SiO2-supported catalyst.