Oxidation of dodecane on vanadium-molybdenum catalysts

摘要

The catalytic oxidation of dodecane with air oxygen on individual and mixed vanadium-molybdenum (1 ? x)V_2O_5 · xMoO_3 oxide is studied over a temperature range of 250 to 400°C. It is shown that oxidation of dodecane to organic acids at 250°C produces undecylic acid C_(11)H_(26)COOH and carbon oxides, as products of the subsequent oxidation of formic acid. The most effective catalyst is a mixed oxide containing 75 mol % MoO_3 and 25 mol % V_2O_5. At 275–300°C, this catalyst provides the maximum yield of acids and a relatively low fraction of complete-oxidation products. Above 250°C, a mixture of acids and carbon oxides is formed, the yield of which increases with the temperature up to 300°C. As the temperature is increased still further, the yield of acids decreases due to their subsequent oxidation. The catalytic oxidation is accompanied by changes in the phase composition, morphology, and degree of crystallinity of the mixed-oxide catalysts. A possible mechanism of the catalytic process is considered.