Аннотация:Catalysts of the general composition CrOx–ZrO2–SiO2 were prepared by two procedures: (1) one-step precipitation of all the components and (2) introduction of CrOx by impregnation of the ZrO2–SiO2 support. The CrOx content was varied from 4 to 9 wt % in terms of the Cr2O3 stoichiometry. The catalysts were characterized by X-ray diffraction analysis, Raman spectroscopy, X-ray photoelectron spectroscopy, temperature-programmed reduction with hydrogen, thermal analysis, and electron microscopy. The catalytic activity of the catalysts in nonoxidative propane dehydrogenation in a flow-through system with a fixed catalyst bed was compared. The one-step synthesis method ensures uniform distribution of chromium oxides in the catalyst. The presence of the silica precursor in the course of precipitation inhibits the Cr2O3 and ZrO2 crystallization and ensures close contact of coordination-unsaturated Zr4+ sites with Cr3+ sites on the surface; therefore, the catalysts prepared by the one-step method are more active. The low activity of the catalysts prepared by impregnation is caused by the formation of coarse Cr2O3 particles heterogeneously distributed on the surface. In the course of nonoxidative propane hydrogenation, the surface of the catalysts undergoes coking, which leads to a decrease in their activity. Short treatment in air at 550°С virtually fully restores the activity of the catalysts prepared by the one-step method.
