THE CONTROL STEP OF REDOX MECHANISM FOR O XIDATION 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 orthogo nal design. The rate constants of reduction for catalysts with CO, k(1 ), were more than the rate contants of reoxidation for reduced catalys ts with O-2, k(2). The ratios of k(1) to k(2) varied within the range of 4.24-133, which showed that the control step for oxidation of CO ov er REFeO(3) was the reoxidation step of reduced catalyst. The conversi ons of CO, X(CO), were more than the conversions of O-2, X(O2), with p ulse method. These pulse data proved the conclusion of control step fo r 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 constsnts of partial pressures P-CO and P-O2 over REFeO(3) cataly sts was approximately. The oxidation of CO over REFeO(3) has compensat ion effect.