PARTIAL OXIDATION OF PROPANE OVER V-P-O CATALYSTS AND PROMOTERS

Over the catalyst containing (VO)2P2O7 and beta*-VOPO4, C3H8 was oxidized to acetic and acrylic acids with the selectivities of 30-36% and 30-38%, respectively. The addition of La2O3 and Dy2O3 onto the catalyst brought about an increase in the rate of carboxylic acids formation and its selectivity. The formation rate of the carboxylic acids gave a maximum at 10-20 at% of La content. Enhanced selectivity of carboxylic acids was observed upon the addition of Bi2O3. The selectivity of acetone extrapolated to 0 sec of W/F was estimated to about 6%, suggesting that there is a reaction path to acetone via isopropenyl radical, isopropenylperoxyl radical. Temperature programmed desorption spectra of NH3 and CO2 from the V-P-O catalysts with and without La2O3 indicated that the addition of La2O3 increased the amount of both weaker acidic sites and weaker basic sites. Comparing the formation rates of partial oxidation products over the La2O3 containing catalyst and that containing no La2O3 in the oxidation of C3H8, C3H6, and acrylic acid, it is concluded that added La2O3 mainly accelerates the rate of reaction via isopropenylperoxyl radical.