CrOx–SiO2 Catalysts in Nonoxidative Propane Dehydrogenation: Effect of Adding Cerium Dioxide

Abstract

The effect that introduction of cerium oxide into oxide systems based on chromium and silicon exerts on the catalytic properties of these systems in nonoxidative propane dehydrogenation in a flow-through system with a fixed catalyst bed was studied. The characteristics of the catalysts CrO_x–SiO₂ and CrO_x–CeO₂–SiO₂, both containing 9 wt % CrO_x assuming the Cr₂O₃ stoichiometry, were compared. The СеО₂ content of the ternary system was 52 wt %. The catalysts were characterized by X-ray diffraction analysis, scanning electron microscopy, Raman spectroscopy, electron paramagnetic resonance, X-ray photoelectron spectroscopy, temperature-programmed reduction with hydrogen, and thermal analysis. In the initial period of the reaction, the catalyst containing CeO₂ demonstrated higher propane conversion at 500 and 550°С and higher deactivation rate compared to CrO_x–SiO₂. Both catalysts can be regenerated by treatment in an air stream at 550°С for 30 min. Cerium dioxide favors the reduction of chromium in high oxidation states to form active reaction sites, Cr³⁺ ions, ensures higher dispersity of the chromium oxides, and favors partial oxidation of coke deposits in the initial period of the catalyst operation.