Hydrothermal synthesis of vanadate-substituted hydroxyapatites, and catalytic properties for conversion of 2-propanol

M-vanadate hydroxyapatites and M-phosphate hydroxyapatites (M = Ca, Sr, and Pb) were synthesized at 110 °C for 14 h under a hydrothermal condition. The prepared powders were characterized by the ICP chemical analysis, the powder X-ray diffraction, the TEM observation, the nitrogen physisorption, the TG analysis, and the CO₂-TPD measurements. The catalytic properties for the reaction of 2-propanol depended on the component ions of the prepared hydroxyapatites. In an argon atmosphere, the acetone selectivity of the prepared hydroxyapatite catalysts increased in the following order: Ca < Sr < Pb and vanadate < phosphate. The catalytic activity values of M-vanadate hydroxyapatites were higher than those of M-phosphate hydroxyapatites, except for Sr-vanadate hydroxyapatite which decomposed during the reaction at 250 °C. Hydrogen was stoichiometrically produced with acetone over the M-phosphate hydroxyapatites and Pb-vanadate hydroxyapatite with strong basic sites.