Catalytic Activity of V–Sn Oxides for Oxidation Reactions

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Abstract
The rate of oxidation of C3H6, C2H4, C3H8, and CO has been investigated over V–Sn oxides of various compositions. The rate shows two maxima at V–Sn(V/Sn=2/1) and (1/8) oxides. Comparison between the rate of reduction of the oxides with C3H6 and that of the corresponding catalytic oxidation suggests that the oxygen species responsible for oxidation differs for V–Sn(2/1) and V–Sn(1/8) oxides. The amount of oxygen desorbed in the temperature range 400–530 °C varies with the composition of the V–Sn oxides, showing a maximum at V–Sn(2/1) oxide. With V–Sn(1/8) oxide, little or no oxygen desorption is observed. On the basis of these results together with those of structural studies, it is concluded that the rate maximum with V–Sn(2/1) oxide arises from formation of an amorphous material from which lattice oxygen is easily released, while the rate maximum with V–Sn(1/8) oxide is associated with the presence of V4+ ions dissolved in SnO2.