METHANOL ADSORPTION AND DEHYDROGENATION OVER STOICHIOMETRIC AND NONSTOICHIOMETRIC HYDROXYAPATITE CATALYSTS

On hydroxyapatite of stoichiometric composition (Ca/P = 1.65), methano l decomposes at 600 degrees C, in the absence of oxygen, to produce pr edominantly carbon monoxide. As the Ca/P ratio decreases, the selectiv ities to formaldehyde and dimethyl ether increase to ca. 80% at a valu e of Ca/P equal to 1.51. IR spectra show that methoxy groups are forme d on the surface of both the stoichiometric and non-stoichiometric cat alysts. Both IR and temperature-programmed desorption experiments sugg est that for the decomposition of methanol, acidic sites are required for the dissociative adsorption whereas basic sites facilitate the C-H bond scission via carboxylate groups and the consequent formation of CO and H-2.