Effects of heat-treatment atmosphere and temperature on cobalt species in Co/Al2O3 catalyst for propane dehydrogenation

Co-based catalysts have attracted increasing attention as promising catalysts for propane dehydrogenation (PDH) because of their C–H bond activation ability. Co species in Co/Al2O3 are present in various forms, such as Co3O4, CoAl2O4, CoO, and metallic Co. However, the catalytic properties of the various Co species in PDH are unclear. In this work, we prepare Co/Al2O3 with different compositional distribution of Co species by heat-treating the supported Co precursor under O2, Ar, and H2 atmospheres at temperatures between 500 and 600 °C. H2-treated Co/Al2O3 results in superior performance compared to O2- and Ar-treated catalysts. This is attributed to the relatively high Co surface concentration and relatively high ratio of tetrahedral Co2+ stabilized in CoAl2O4 to the total Co species. A detailed study shows that both tetrahedral Co2+ and metallic Co in Co/Al2O3 are active for PDH, but the former is more selective.