Preparation of aluminovanadate oxynitride catalysts: characterisation of a dinitrogen intermediate phase by DRIFTS, XPS, TGA.

The nitridation of aluminovanadate oxide precursors in order to obtain new acid-base catalysts is studied. The results show that an intermediate phase appears during thermal nitridation under ammonia flow. This phase, involved in the nitridation mechanism, induces a) DRIFTS bands due to stretching between two nitrogen atoms (nu N drop N) at 2100 cm(-1), b) an XPS N1s binding energy peak at 403 eV, c) an overweight during thermal oxidation followed by TGA. Most probably these fingerprints can be attributed to metal dinitrogen interaction (M-NN), but the presence of azide intermediates can not be ruled out.