催化剂载体对噻吩吸附和表面反应的影响

EFFECT OF SUPPORTS ON ADSORPTION AND SURFACE REACTION RATES OF THIOPHENE

应用动态分析方法考察了噻吩在Mo/Al_2O_3、Mo/SiO_2、Mo/TiO_2三种催化剂上的吸附和表面反应速率常数,实验结果表明:(1)载体对吸附和反应性能都有影响,其中对吸附影响更加突出。在任一载体上,K_A·k_r/k_a远小于1,表面反应是噻吩氢解的速率控制步骤,而吸附是平衡的;(2)由MoO_3载量对K_A及K_r的影响推测,对Mo/Al_2O_3催化剂,噻吩主要吸附于载体上,而氢解反应则发生在金属Mo上;对Mo/SiO_2催化剂,则吸附和反应都发生在Mo上;(3)用动态分析方法按两步反应机理获得的载体对K_p的影响规律与稳态法结果基本一致。

The adsorption and surface reaction rate coefficients of thiophene hydrogenolysis over Mo/SiO_2, Mo/Al_2O_3 and Mo/TiO_2 catalysts are measured by using dynamic analysis method. The results show: (1)There is an effect of supports on the adsorption and reaction of thiophene, of which on the former is more obvious. On each supports, K_A. k_r/k_a<<1, therefore, it is suggested that the rate-determining step of thiophene hydrogenolysis is the surface reaction and that adsorption eqilibrium can be assumed. (2)For Mo/Al_2O_3 catalyst, thiophene can be adsorbed on the support while hydrogenolysis of adsorbed thiophene takes place on Mo active sites. However, for Mo/SiO_2 catalyst, both adsorption and reaction proceed on the Mo activesites.(3)The effect of supports on the value of k_p obtained from dynamic analysis method with two-step mechanism is similar to that from steady method.