Abstract
Anaerobic oxidation of isobutane was studied using MgV 2O 6, Mg 2V 2O 7 and Mg 3V 2O 8. Isobutene, a small amount of CO x , and trace amount of oxygen containing compounds were formed. CO 2 was formed mainly at the beginning of the reaction and decreased with reaction time. Catalytic activity of Mg 2V 2O 7 was slightly higher than that of MgV 2O 6 but the CO x formation over MgV 2O 6 was more than over Mg 2V 2O 7. Mg 3V 2O 8 was the least active. Therefore, Mg 2V 2O 7 is the most suitable for oxidative hydrogenation of isobutane under the anaerobic reaction conditions. The equilibration between 16O 2 and 18O 2 over MgV 2O 6 was faster than over Mg 2V 2O 7 or Mg 3V 2O 8 at 673 K. The rate of equilibration between 18O 2 and lattice oxygen over MgV 2O 6 was similar to that over Mg 2V 2O 7, which was faster than over Mg 3V 2O 8. Highest yield of isobutene formation over Mg 2V 2O 7 would come from the character of Mg 2V 2O 7, in which mobility of the lattice oxygen is great but surface reaction of isobutane was not so fast. Higher activity for isobutene formation may come from the nature of Mg 2V 2O 7, of which mobility of the lattice oxygen is great but surface reaction of isobutane was not so much fast. Mn, Cr, Fe, Ni and Co can be introduced into Mg 2V 2O 7 to give a single phase. Substitution of Co, Cu and Cr for Mg increased the activity of Mg 2V 2O 7 for isobutane oxidation and substitution of Ni and Mn scarcely affected the activity but substitution of Fe and Zn decreased the activity. Substitution of all the metal ions slightly increased the isobutene selectivity. MgO, MgV 2O 4 and Mg 3V 2O 8 were observed in the sample after the anaerobic oxidation of isobutane. Cu containing catalyst was reduced to give Cu metal.
Published Version
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