REDOX MECHANISM OF PROPYLENE OXIDATION OVER Bi2Mo3O12-Bi2O3 CATALYST

The kinetics of propylene oxidation over Bi2Mo3O12-Bi2O2 catalyst in a differental flow reactor has been investigated. The partial pressures of propylene and oxygen coverd the range of 0.05-0.95 atm and 0.07-0.80 atm, respectively. Keeping their partial pressures less than 0.30 atm, the rate of acrolein formation took first order for propylene and 0.5 order for oxygen. The apparent activation energy was 30.1 kcal/mol. On the other hand, the kinetics of acrolein formation did not follow any power rate equation when the partial pressure of propylene or oxygen became large than 0.30 atm. A maximum rate of acrolein formation appeared. The results of thermo-desorption indicated that molecular propylene can adsorbed on the catalyst of the oxidation state below 150 degrees C. At higher temperature range (300 degrees C), no molecular propylene can exist on the catalyst and thhe species of desorptionwill be acrolein, carbon monoxide and dioxide. Molecular oxygen can not exist on the catalyst over a wide temperature range of 25 degrees C-500 degrees C. It is suggested that the acrolein formation may be via a redox mechanism in which the rate-limiting step is the reaction between two species on thhe catalyst surface.