MoVTeNbO multifunctional catalysts: Correlation between constituent crystalline phases and catalytic performance

The characterization (SBET, XPS, XRD, SAED, HREM) and the catalytic performance in the propane oxidation of MoVTeNbO mixed metal oxides catalysts, synthesized by three different preparation procedures, are comparatively presented. Te2M20O57, Te0.33MO3.33 (M=Mo, V, Nb) and Mo5O14-type phases were observed in the most active and selective catalysts. In addition to these, new Te-containing crystalline phases, i.e., M17O47 (cell parameters a=2.16nm, b=1.96nm and c=0.39nm) and an unidentified phase deriving from the tetragonal tungsten bronze (TTB) type structure with cell parameters a=2aTTB and c=cTTB, have also been observed in samples prepared from a slurry containing vanadyl sulphate, although they presented a low catalytic activity. The catalytic performance of MoVTeNbO multifunctional catalysts is related to the presence of Te2M20O57-type phase (M=Mo, V, and Nb), although cooperation between phases must also exist. However, a certain composition or composition range is necessary to achieve the best catalytic performance, since the chemical composition of Te2M20O57-type phase changes in every catalyst. Te2M20O57-type phase with a Te0.32(Mo0.79Nb0.11V0.10)5O14 composition has been found in the most active and selective catalyst whereas Te0.6(Mo0.72Nb0.14V0.13)5O14 is the constituent in the less active and selective one, the rest of the catalysts presenting intermediate both Te/Mo ratio and catalytic performance.