瞬变应答法研究苯催化氧化的反应机理

MECHANISTIC STUDIES ON CATALYTIC OXIDATION OF BENZENE BY A TRANSIENT RESPONSE METHOD

采用瞬变应答法研究了苯在钒催化剂上催化氧化的反应机理。通过对应答曲线的分析,证明氧首先被催化剂表面吸附,然后以较慢的速率转化为晶格氧,这一步是苯催化氧反应速率的控制步骤。吸附氧是生成 CO 和 CO_2的氧源;晶格氧是生成顺酐的氧源。气相苯不直接参与反应,但以较快的速率可逆吸附于催化剂上,吸附的苯与晶格氧反应生成中间物 IN,IN 进一步氧化生成顺酐。顺酐可逆吸附于催化剂上,其介吸速率较慢。中间物和吸附的顺酐对反应起阻滞作用。

The mechanism of catalytic oxidation of benzene has been studied by applying a transient response method.A model of the reaction mechanism is proposed.In the model,oxygen is assumed to be adsorbed by the catalyst at first,then it converts into lattice oxygen with a slow rate,which is the controUing rate of the overall oxidation of benzene.The benzene in gas phase does not take part in reaction but is adsorbed at the surface of catalyst with a rapid rate.The adsorbed benzene reacts with lattice oxygen to form an intermediate IN,which,in turn,is oxidized to maleic anhydride. The desorption of maleic anhydride is relatiVely slow.