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REFeO3上CO氧化Redox机理的控制步骤
The Control Step of Redox Mechanism for Oxidation of CO Over REFeO3 Catalysts
【摘要】 用柠檬酸配合法制备REFeO3(RE=La,Pr,Nd,Sm,Eu,Gd,及Dy).用XRD测定了REFeO3的钙钛矿结构.用CO还原脉冲及O2氧化脉冲证实REFeO3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k1比还原了的催化剂用O2再氧化速率常数k2要大,k1/k2值在4.22~133之间,这说明在REFeO3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(Xco比O2的转化率(Xo2)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Pco及Po2下的反应速度呈近似的线性关系.在REFeO3上CO氧化存在补偿效应.
【Abstract】 REFeO3 (RE = La, Pr, Nd, Sm, Eu, Gd, Tb and Dy) were prepared by the complex method with citric acid. The perovskite structure for REFeO3 was determined with XRD. The Redox mechanism for oxidation of CO was proven by the pulse method of reduction with CO and reoxidation with O2 over REFeO3 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, k1, were more than the rate contants of reoxidation for reduced catalysts with O2, k2. The ratios of k1 to k2 varied within the range of 4.24 - 133, which showed that the control step for oxidation of CO over REFeO3 was the reoxidation step of reduced catalyst. The conversions of CO, XCO, were more than the conversions of O2, XO2 , with pulse method. These pulse data proved the conclusion of control step for the steady-state kinetics. The Redox equation (9) canbe 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 constsnts of partial pressures Pco and Po2 over REFeO3 catalysts was approximately. The oxidation of CO over REFeO3 has compensation effect.
- 【文献出处】 化学学报 ,Acta Chimica Sinica , 编辑部邮箱 ,1996年02期
- 【分类号】O643.3
- 【下载频次】60