AlCl_(3)和GaCl_(3)上AsH_(3)催化氧化反应机理的理论研究

A theoretical study of the mechanism of AsH_(3) catalytic oxidation on AlC_(3)and GaCl_(3)

采用密度泛函方法研究了AsH_(3)与O_(2)的反应机理以及在催化剂AlCl_(3)和GaCl_(3)上该反应的催化氧化反应机理.途径Ⅰ为AsH_(3)与一分子O_(2)反应生成H_(3)AsO_(2),该途径分2步完成,第2步为速度控制步骤.途径Ⅱ为H_(3)AsO_(2)与另一分子O_(2)反应生成H_(3)AsO_(4),该途径分4步完成,其中第4步的活化自由能垒最高,为50.14 kcal/mol.途径Ⅲ和IV分别为AlCl_(3)和GaCl_(3)上AsH_(3)与O_(2)的反应途径.计算结果表明在这2种催化剂上,AsH_(3)与O_(2)反应的活化自由能垒均降低,约为12~15 kcal/mol.

The reaction mechanism of AsH_(3) with O_(2) and the catalytic oxidation reaction mechanism of AsH_(3) on AlCl_(3) and GaCl_(3) were studied by the density functional method.Pathway I is the reaction of AsH_(3) with a molecule of O_(2) to generate H_(3)AsO_(2).Two steps are included in this pathway and the second step is the rate-controlling step.In Pathway II,the product is H_(3)AsO_(4) by the reaction of H_(3)AsO_(2) with a molecule of O_(2).The pathway is completed in four steps,and the fourth step has the highest energy barrier,which is 50.14 kcal/mol.Pathways III and IV are the reaction paths of AsH_(3) and O_(2) on AlCl_(3) and GaCl_(3),respectively.The calculation results show that the free energy barrier of the reaction between AsH_(3) and O_(2) is reduced on AlCl_(3) and GaCl_(3),about 12~15 kcal/mol.