Abstract: The influence of internal diffusion of benzene on the kinetics of complete oxidation of benzene over Pt/Al₂O₃catalyst has been investigated by the external circulation reactor. The reaction took place in the kinetic region when the catalyst with 0. 45-0. 60 mm was used. The kinetics of complete oxidation of benzene was described by the rate equation of -0. 9th order with respect to benzene under the condition of excess of partial pressure of oxygen in the kinetic region. When the catalyst was increased to φ6 × 5 mm the reaction took place in the internal diffusion region and its reaction order changed to -0. 1st order. The values of effectiveness factors (η) of the catalyst were determined experimentally to be 0. 24 -1. 20. η_expincreased with the raise of the partial pressure of benzene at a constant temperature, and η_expdecreased with the raise of temperature at a constant partial pressure of benzene.The activation energy of complete oxidation of benzene is 55. 5 kJ/mol in the kinetic region. When the reaction is controlled by the internal diffusion, the activation energy of reaction is 34. 9 kJ/ mol, and is equal to the arithmetic mean of activation energies of kinetic region and molecular diffusion of benzene approximately.

Key words: Benzene, Complete oxidation, Internal diffusion, Pt/Al₂O₃catalyst