Effect of coking and propylene adsorption on enhanced stability for Co2+-catalyzed propane dehydrogenation

The effects of Si-additive modification on nonoxidative propane dehydrogenation (PDH) over γ-Al2O3 sheet-supported isolate Co2+ catalysts have been investigated. Si addition cannot change the nanosheet structure and tetrahedral Co2+ coordination of the Co catalysts; nonetheless, it introduces a number of moderate-strength acid sites by the formation of composite SiAl oxides. Promoted catalytic stability is achieved on Si-modified Si–Co–Al2O3 in comparison with the Si-free Co–Al2O3 catalyst. In spite of similar total content and H/C ratios of deposited coke species on these two spent catalysts, a relatively lower graphitization degree and a higher ratio of highly reactive coke species are observed on the Si–Co–Al2O3 catalyst. Furthermore, the co-feeding of C3H6 significantly changes the coking reaction rates but not the coke distributions on Co-based catalysts. The C3H6 temperature-programmed desorption profiles and in situ diffuse reflectance infrared Fourier transform spectra suggest that the interaction of C3H6 with Co catalysts can be affected by Si modification tuning the coking property and the catalytic stability of Co2+–Al2O3-based catalysts for the PDH reactions.