Oxidative Dehydrogenation of Propane on Hydroxyapatite‐Supported Cobalt Catalysts

Abstract

AbstractHydroxyapatite (HAp)‐supported cobalt catalysts have been evaluated in the oxidative dehydrogenation of propane to propene (ODHP). The morphology of the HAp supports and the cobalt immobilization mechanisms strongly influence the surface accessibility of cobalt species and their dispersion. A calibration curve obtained from NO‐TPD experiments for the cobalt‐exchanged materials allowed us to derive their cobalt surface densities. These values were used to better compare the evolution of propane conversion and propene selectivity, as well as to analyze the parameters governing these performances. Co3O4 nanoparticles formed by the strong electrostatic adsorption process are poorly selective in propene compared to isolated Co2+ cations immobilized by the cationic exchange mechanism. The isolated Co species exhibit a turnover frequency per Co atom that is two orders of magnitude higher than that reported for Co‐based systems in previous studies. This much better performance is attributed to (i) the promotion of HAp basicity by cobalt incorporation as shown by the model MBOH conversion, (ii) the complete surface accessibility of the isolated Co2+ cations, and (iii) the close proximity between the Co2+ redox centers and the basic sites, as investigated by DFT.