CATALYTIC OXIDATIVE COUPLING OF METHANE ON METAL-OXIDES .1. EFFECT OF OXIDATION-STATE OF BISMUTH AND REVERSIBILITY OF LATTICE OXYGEN ON ACTIVITY IN BARIUM LANTHANUM BISMUTH OXIDES

Oxidation of methane was studied for a number of oxides containing bismuth viz. Ba2LaBiO6, Ba1-xLaxBiO3 (0 less-than-or-equal-to x less-than-or-equal-to 0.7), Y0.5Bi1.5O3 and Bi2O3. These oxides were selected in order to determine the influence of (a) oxidation state and structural environment of bismuth in an oxide lattice and (b) reversibility of lattice oxygen on catalytic activity. C2H6, C2H4, CO2 and H2O were the only products detected for these oxides in the temperature range of 723-1023 K at a gas hourly space velocity of 10 000 h-1 (1 atm and 298 K) using a feed composition of 20% CH4, 5% O2 and 75% of Ar. The percentage methane conversion per unit area and selectivities of some of the oxides were found to be higher than those of La2O3 and 1% Li/MgO. No correlation was found to exist between the oxidation state of bismuth in these oxides and their catalytic activity. However, a correlation exists between the reversibility of lattice oxygen and catalytic activity for the series Bal-xLaBiO3 (0 less-than-or-equal-to x less-than-or-equal-to 0.7)