Influence of the preparation method on the performance of Rh catalysts on CeO2 for WGS reaction

The present paper deals with the study concerning the CO removal from reforming H2-rich gas stream through WGS reaction over Rh-based catalysts supported on CeO2 carriers. CeO2 was prepared by two different methods: solution combustion synthesis (SCS) and hard template (HT); incipient wetness impregnation method was used to deposit the active metal on the carriers. The screening at powder level in a fixed bed micro-reactor highlighted that feeding 5% CO and 20% H2O (N2 balance) with the HT-prepared catalyst, CO conversion started at slightly lower temperature, but CH4 outlet concentrations were higher than those of the SCS-prepared one. With a simulated reformate mixture (5% CO + 20% H2O + 11% CO2 + 40% H2, N2 balance), the equilibrium WGS curve was exceeded for both catalysts (for the HT-prepared catalyst, CO conversion started at lower temperature and reached 100%), due to the parasite methanation reactions of both CO and CO2, favoured by the presence of a large hydrogen concentration in the reactor. A very high CH4 outlet concentration (max 18.6%) was measured for the HT-prepared catalyst. Then, tests at different weight space velocities WSV were carried out: with the SCS-prepared catalyst the best performance was obtained by lowering WSV.