Kirienko P. Effect of the composition of metal-oxide catalysts Pd (Pt)-MxOy/cordierite (M: Co, Cu) on their activity in CO, NO, O2, hexane redox reactions

The thesis is devoted to development of structured catalysts with a low concentration of noble metals and with optimal structural and functional characteristics for the processes of emissions purification in internal-combustion engines from CO, NOx and CnHm and for the selective reduction of O2 by hydrogen in the presence of NO. The dependence of Pd (Pt)-MxOy/cordierite catalytic activity on composition and preparation method has been investigated. It has been found that increased oxide catalyst activity in redox reactions, after doping Pd, is caused by raised mobility of surface oxygen owing to the formation of complex active centers, including cations of 3d-transition metal and palladium. It has been shown that order of CeO2 introduction in the Pd-Co3O4/cordierite catalytic composition significantly affect the catalytic activity in the reactions of conversion of CO, NO and hexane. The best effect has been achieved with simultaneous introduction of oxides Co3O4 and CeO2, and caused by more intense interaction of oxides because of increased dispersion of components. The negative effect of second support on the activity of Pd-Co3O4, caused by strong interaction between the active component and the second support, has been found in CO and hexane oxidation reactions. The influence of palladium concentration and nature of 3d-transition metal oxides (Co, Cu, Ni) and oxides of rare earth elements (La2O3, CeO2) on the selectivity of the catalyst has been investigated in the process of O2 hydrogenation in the presence of NO. It has been shown that Pd and La2O3 have enhanced the activity and selectivity of Co3O4/cordierite towards reduction of O2 by hydrogen in the presence of NO.