在Pt/Al2O3催化剂上苯的内扩散对负0.9级动力学的影响

在Pt/Al₂O₃催化剂上用外循环反应器研究了内扩散对苯完全氧化动力学的影响,当用30～40目(即0.45～0.60mm)催化剂时反应在动力学区域进行.若O₂过量时则动力学区域苯的完全氧化可用-0.9级速率方程描述.当催化剂粒径增至φ6×5mm时,反应在内扩散区域进行并变为一0.1级反应.催化剂有效因子η在0.24～0.12之间.在同一温度下,η_实验随苯分压p_苯的增加而增大;而p_苯相近时,η_实验则随温度的升高而减小.动力学区域的反应活化能为55.5kJ/mol,内扩散区域的反应活化能为34.9kJ/mol,其值约为动力学区域的活化能与苯分子扩散活化能的算术平均值.

The Influence of Internal Diffusion of Benzene on the Kinetics of - 0. 9th Order over Pt/Al2O3 Catalyst

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.