Influence of preparation method on catalytic properties of mixed calcium-cobalt

Mixed calcium-cobalt orthophosphates of the formula Ca3-xCOx(PO4)(2), with 0 less than or equal to x less than or equal to 1.1, were prepared by coprecipitation and solid-state reaction. Structural characterization showed that, in both cases, the solids obtained resulted from substitution of some Ca2+ ions by Co2+ ions in the beta-Ca-3(PO4)2 structure. The solubility limit of cobalt in this structure corresponded to x = 0.31. The morphology of these compounds was investigated by surface-area measurements and scanning electron microscopy. When tested in the 2-propanol decomposition reaction, the maximum activity in dehydrogenation was obtained with the compound corresponding to cobalt maximum solubility in beta-Ca-3(PO4)2 structure. Higher activities were obtained for samples prepared by coprecipitation.