Oxidation of isobutane over complex oxides containing V, Nb, Ta, and Mo under aerobic and anaerobic reaction conditions Original Research Article

Isobutane oxidation over single metal oxides of V, Nb, Ta, and Mo and over their complex oxides was studied. The most active was V2O5, while medium activity was shown by LaVO4, BiVO4, CaV2O6, Ta2O5, TaV2O6, ZnNb2O6, Nb2O5, MgV2O6, YVO4, Cu2V2O7, MoO3 and MnNb2O5. The less active oxides were Na2MoO4 and Ag2MoO4. Isobutane was oxidized mainly to isobutene and COx, but isobutene selectivity was generally lower than 50% below 673 K. Relatively high isobutene selectivity was shown by MgTa2O6, TaV2O6, and ZnNb2O6. Methacroleine was only obtained over MoO3 and methanol was formed only over V2O5 and Cu2V2O7. Acetic acid was formed over certain V-containing oxides. No oxygen-containing products were formed over Nb- and Ta-containing oxides. On a unit surface area basis, Nb2O5 and Ta2O5 have higher oxidizing activity than V2O5 and MoO3.Isobutane oxidation was studied in the absence of gaseous O2 over MV2-type complex oxides. Catalytic activity was determined as follows: image. MgV2O6 is the most selective for isobutene formation. Combination to easily redoxable metal ions tends to accelerate the deep oxidation process. There may be a threshold for the initial reaction rate of lattice oxygen per unit surface area for selective isobutene formation. Selective isobutene formation continued until a reduction of MgV2O6 by at least 4.5%, had finished and the reduced catalyst was recovered by the calcination at 773 K. Selective formation of isobutene made it possible to combine oxidations of isobutane with MgV2O6 and with the oxidations of reduced catalysts. Article Outline