Study of the mobility of lattice oxygen in complex oxide catalysts for partial oxidation of propylene to acrolein

The amount of oxygen in the lattice of solids that participates in the elem entary stages of partial propylene oxidation is determined for two types of Co-Mo-Bi-Fe-Sb-K-O catalysts (I, II) differing in the method of introducti on of antimony and potassium. Two independent methods are used: (1) on the basis of the yield of the oxygen-containing products of propylene oxidation by oxygen of the catalyst in a pulse regime and (2) with the use of Moessb auer spectroscopy. Coincidence of the results obtained by both methods indi cates that the active oxygen of the catalyst lattice is formed during redox transformations of iron(III) molybdate entering the composition of the cat alysts. Data on the reduction of the catalysts in a pulse regime at various temperatures, which were processed in the framework of the diffusion model , allowed the estimation of the rate constants for diffusion of the lattice oxygen. An increase in the mobility of the lattice oxygen in catalyst I, w hich is modified with a small amount of antimony as compared to catalyst II , results in an increase in the overall productivity of the sample and in a decrease in the selectivity of propylene oxidation to acrolein. This corre lates with the increase in the total amount of the lattice oxygen participa ting in the process.