Number of surface redox sites of V-Sb-O catalysts

The NARP technique was applied for the measurement of surface redox sites o f V-Sb-oxide catalysts. The profile of produced nitrogen in the NARP measur ement was composed of two parts; the initial sharp peak and the tailing par t, those represented the contribution of surface redox sites and regenerati on step of the redox sites with lattice oxygen, respectively. The surface c oncentration of redox sites determined from the initial sharp peak was almo st equivalent to the surface concentration of vanadium ions above surface S b/V ratio of 1.0. The role of V-O-Sb sites on VSbO4 surface as redox sites was suggested. The tailing part was broader than that of V2O5 at the same t emperature range because of the faster regeneration step relative to that i n V2O5. The surface concentration and the regeneration of redox sites stron gly depend on the preparation method.