REFeO~3上CO氧化Redox机理的控制步骤

用柠檬酸配合法制备REFeO~3 (RE=la, Pr, Nd, Sm, Eu, Gd, 及Dy)。用XRD测定了REFeO~3的钙钛矿结构。用CO还原脉冲及O~2氧化脉冲证实REFeO~3上CO氧化为Redox机理。用外循环流动无梯度反应器研究CO氧化稳态动力学。动力学方程中的参数用正交设计法估计。催化剂用CO还原的速率常数k~1比还原了的催化化剂用O~2再氧化速率常数k~2要大, k~1/k~2值在4.22～133之间, 这说明在REFeO~3上CO氧化的控制步骤为还原催化剂的再氧化。用脉冲法得到的CO转化率(X~C~O)比O~2的转化率(X~O~2)要大。脉冲法证实稳态动力学控制步骤的结论。Redox动力学方程式(9)可简化为控制步骤方程式(11)。催化剂还原速度常数与一定P~C~O及P~O~2下的反应速度呈近似的线性关系。在REFeO~3上CO氧化存在补偿效应。

The control step of redox mechanism for oxidation of CO over REFeO~3 catalysts

REFeO~3 (RE=La, Pr, Nd, Sm, Eu, Gd, Tb and Dy) were prepared by the complex method with citric acid. The perovskite structure for REFeO~3 was determined with XRD. The Redox mechanism for oxidation of CO was proven by the pulse method of reduction with CO and reoxidation with O~2 over REFeO~3 catalyst. The steady-state kinetics of oxidation for CO has been investigated with external circulation flow reactor. The parameters of kinetic equation were estimated by the method of orthogonal design. The rate constants of reduction for catalysts with CO, k~1, were more than the rate constants of reoxidation for reduced catalysts with O~2, k~2. The ratios of k~1 and k~2 varied within the range of 4.24～133, which showed that the control step for oxidation of CO over REFeO~3 was the reoxidation step of reduced catalyst. The conversions of CO, X~C~O, were more than the conversions of O~2, X~O~2, with pulse method. These pulse data proved the conclusion of control step for the steady-state kinetics. The Redox equation (9) can be simplified to the equation of control step (11). The linear relationship between the rate constants of reduction for catalysts and the reaction rate at the constants of partial pressures P~C~O and P~O~2 over REFeO~3 catalysts was approximately. The oxidation of CO over REFeO~3 has compensation effect.