Preferential oxidation of CO in H2 rich stream (PROX) over gold catalysts supported on doped ceria: effect of preparation method and nature of dopant

The reaction of PROX over nanosized gold catalysts, supported on ceria doped with FeOx, MnOx and CoOx, was investigated. The modified ceria supports were synthesized by co-precipitation (CP) and by mechanochemical activation (MA). The catalysts were characterized by XRD, HRTEM and TPR. When the CP preparation method was applied a deeper insertion of dopant in ceria structure occurs, while with the MA the formation of separate dopant oxide phases occurs (XRD and HRTEM data). On the basis of TPR results the most probable oxidative state of dopant ions was suggested. The catalytic test showed that gold catalysts on MA ceria supports, modified with FeOx and MnOx, can be selected as the most promising ones for PROX among the studied catalysts. The obtained differences in catalytic behaviour cannot be related to the effect of gold because using both preparation modes a high dispersion of gold particles was evidenced by HRTEM. The reason could be searched in the support structure and properties depending on the dopant nature and on the preparation method. In the case ofMAtechnique, beside gold on ceria (modified with Fe and Mn), the gold on separate FeOx and MnOx phases could also contribute to the high PROX activity and selectivity. On the contrary, the presence of Co3O4 phase could be the reason for the low catalytic activity and selectivity observed with Co-containing gold catalyst, prepared by MA.