Impact of phosphorus and nitrogen on structure and catalytic performance of VZrPON oxynitrides in the ammoxidation of 3-picoline

Novel P-containing oxynitrides VZrPON were tested besides their VZrPO oxide precursors in the ammoxidation of 3-picoline and compared with P-free VZrON catalysts for analysing the influence of both incorporated P and N on the catalytic performance. Results of XRD, XPS, ³¹P and ⁵¹V MAS NMR as well as of simultaneous in situ-EPR/UV–vis/Raman studies during nitridation have shown that the incorporation of phosphorus enhances the V dispersion, reduces vanadium partially even down to V³⁺ and leads to the formation of a crystalline ZrV_2?xP_xO₇ phase for Zr/V ? 0.5 with V sites surrounded by four O atoms only. N is preferentially incorporated in the vicinity of P, thus, suppressing the formation of VN moieties. These facts may be a reason why the incorporation of P does not markedly improve the catalytic performance of VZrPON catalysts.