Fe2O3上AsH3催化氧化反应机理的理论研究

本文采用密度泛函理论方法研究了Fe₂O₃上AsH₃的催化氧化反应机理.该反应以Fe₂O₃中的两个Fe原子为不同的活性中心进行研究，每个活性中心均设计了3个步骤. AsH₃分子依次与3个O₂分子在催化剂上相互作用分别形成中间体H₃AsO₂、H₃AsO₄及最终产物H₃AsO₆.研究发现，当氧化反应发生在1号铁原子(Fe1)附近，其速度控制步骤活化自由能垒为49.99 kcal/mol;当氧化反应发生在2号铁原子(Fe2)附近，其活化自由能垒为21.20 kcal/mol,与直接氧化(50.14 kcal/mol)相比大大降低.可见AsH₃在Fe₂O₃上的催化氧化反应更易发生在Fe2附近.

Theoretical Study on the Mechanism of the Catalytic Oxidation of AsH3 on Fe2O3

The mechanism of the catalytic oxidation of arsine hydrogen (AsH3) on Fe2O3 was studied by density functional theory. The reactions with two Fe atoms in Fe2O3 were used as different active centers, and each active center was designed with 3 steps. The AsH3 molecule interacted with three O2 molecules in sequence on the catalyst to form intermediates H3AsO2, H3AsO4, and the final product H3AsO6. It is found that when the oxidation reaction occurs near the iron atom (Fe1), the activation free energy barrier for the rate control step is 49.99 kcal/mol, while when the oxidation reaction occurs near the iron atom (Fe2), the activation free energy barrier is 21.20 kcal/mol, which is geatly reduced compared with direct oxidation (50.14 kcal/mol). It can be seen that the catalytic oxidation reaction of AsH3 is more likely to occur near Fe2.