The oxidative demethylation of toluene. II. Kinetics of the reduction of bismuth uranate by toluene

The kinetics of the reduction of bismuth uranate by toluene have been studied in micro-pulse and micro-flow reactors and in a thermobalance, at toluene mole fractions between 0.003 and 0.122 and temperatures between 455 and 527 °C. During the reduction the Bi₂UO₆ is converted into metallic bismuth and UO₂. In the overall reaction rate both the chemical reaction rate at the surface and the rate of oxygen diffusion through the lattice of the solid play a role. A kinetic model comprising these two steps is derived. It appears that Bi₂UO₆ contains two types of lattice oxygen, viz, approximately 2% of a nonselective oxygen with D = 3 × 10^-22 m² sec^-1 and a diffusion energy of activation E = 26 kcal mole^-1, and a more selective oxygen with D = 3 × 10^-20 m² sec^-1 and E = 63 kcal mole^-1 (at 470 °C). Some evidence is found for bismuth uranate having a shear structure, the small amount of nonselective oxygen occupying positions in the shear planes.