STUDY OF FEPO4 CATALYST

FePO4 catalyst with and without Pd impregnation has been prepared and studied for its temperature induced crystallization and identification of the phases formed during hydrogen reduction using Fe-57 Mossbauer and XRD techniques. Amorphous FePO4 transforms to a hexagonal form at almost-equal-to 875 K. The reduction of amorphous FePO4 takes place at almost-equal-to 575 K and leads to the formation of Fe2P2O7. The presence of palladium metal over ferric phosphate facilitates the reduction. Unlike amorphous FePO4, reduction of crystalline FePO4 takes place via the formation of an intermediate phase having delta = 1.15 mm/sec and DELTAEq = 4.39 mm/sec. An ammonia adsorption-desorption study of FePO4 catalyst reveals that both Bronsted and Lewis acid sites are present. The catalyst loses its Bronsted acid sites upon calcination at almost-equal-to 875 K. During oxidative dehydrogenation of isobutyric acid to methacrylic acid, the amorphous FePO4 catalyst is converted to Fe7(PO4)6 and Pd metal facilitates this conversion. (C) 1994 Academic Press, Inc.