The effect of sulfate species in propane dehydrogenation over Co/Al 2 O 3 catalysts was studied. On the one hand, the interaction between SO 42− and cobalt species leads to better dispersed cobalt oxide and restrains the reduction to metallic Co species, thereby inhibiting cracking reaction. On the other hand, the initial C–H bond activation and scission are facilitated on the electron-deficient cobalt and sulfate sites, resulting in dramatically improved dehydrogenation performance. XPS, MS and XRD results show that the reduction of sulfate species to SO 2 and consequently the loss of active cobalt species contribute to the irreversible deactivation of catalyst.