Preparation of Sm-doped Cu-Ce high sulphur-resistant CO oxidation catalysts by combustion co-precipitation method

Abstract

Cu-Ce catalysts have been extensively studied owing to their excellent low-temperature CO oxidation activity. However, they are prone to deactivation in the presence of both water vapor and sulfur. In this study, Ce-Cu-Sm CO oxidation catalysts with enhanced sulfur resistance were synthesized by Sm doping using three methods: combustion, co-precipitation, and acid solution synergistic co-precipitation. The mechanism underlying the improved sulfur resistance was investigated using XRD, TEM, N₂ adsorption and desorption, XPS, H₂-TPR, and CO-TPD techniques. The results revealed that, under the coexistence of 1% CO, 10% H₂O, and 0.01% SO₂, the 20Ce-5Cu-4Sm-CG catalyst (prepared via acid solution synergistic co-precipitation) maintained a 100% CO oxidation efficiency for 220 min at 220 °C and a space velocity of 60000 mL/(g·h). After 280 min, the performance of the 20Ce-5Cu-4Sm-CG catalyst decreased to 70%, which was 1.3 times and 2.5 times higher than that of the 20Ce-5Cu-4Sm-C and 20Ce-5Cu-C catalysts prepared by the co-precipitation method, respectively. Characterization analysis revealed that Sm doping increased the CeO₂ crystal size to a certain extent and reduced the specific surface area of the catalyst. However, it also enhanced the concentrations of Ce³⁺, Cu⁺, and surface oxygen atoms, as well as the ratio of O_α and the number of oxygen vacancies in the CeO₂ lattice, which collectively improved the ability of the catalyst to oxidize CO under sulfur-containing atmosphere. The acid solution combustion synergistic co-precipitation method not only enhanced these five key properties for CO oxidation mentioned above, but also facilitated the formation of coordination complexes with the acid solution and Sm ions during combustion. These complexes were incorporated into the CeO₂ lattice to form a homogeneous solid solution, which made the catalyst particle size more uniform and the specific surface area larger, and eliminated the adverse effects of Sm doping on the surface structure. As a result, the oxidation ability of the catalyst was further improved. In summary, the 20Ce-5Cu-4Sm catalyst, prepared via the acid solution combustion and co-precipitation method, exhibits excellent sulfur resistance and enhances the performance of non-precious metal oxide CO oxidation catalysts for applications in sulfur-containing environments.