Catalytic Performance Of PdCl₂-CuCl₂/Al₂O₃Catalysts For Low-temperature CO Oxidation

The low-temperature CO oxidation has been widely used in the ordinary life, military and industrial, so the study of the catalysts with high performance for CO oxidation has been drawn great attention. In the practical application, the water in the reaction gas is very difficult to be excluded. Thus, it is very important to research the influence of water on the catalytic activity and stability of catalyst.In the paper, PdCl2-CuCl2/Al2O3catalysts were prepared and the activity and stability were investigated for low-temperature CO oxidation. The physical and chemical properties of the catalysts were characterized by XRD, H2-TPR, N2absorption-desorption. ICP-AES. XPS and in situ DRIFTS. The main results were as follows.(1) Supported Wacker catalysts exhibit the high activity for low temperature CO oxidation, but the high concentration water in the reaction atmosphere could lead to the deactivation of the catalyst. The study showed that the deactivation was aroused by the adsorption and deposition of H2O on the catalyst surface, which induced the aggregation and migration of Cu species into the pore of catalyst. It weakened the interaction between Pd and Cu species, and decreased re-oxidation ability of the low valence Pd0to Pd2+, which blocked the redox cycling and resulted in the decrease of the activity for CO oxidation.(2) The surface of catalyst was modified by organic amines and surfactant to improve the stability. The best catalyst showed stable CO conversion of75%within24h.(3) The surface modification of catalysts by surfactant didn’t change the catalyst structure and physical properties. Compared with the reference catalyst, the Pd and Cu species in the modified catalyst were difficult to be reduced. However, Cu+species could be more easily oxidized, which accelerated the reaction of Cu2++Pd+/Pd0â†'Cu++Pd2+and promote the redox cycle of the catalyst. The surface modification also retarded the adsorption of H2O on the surface of catalyst and promoted adsorption of CO, which enhanced the stability of catalyst under the condition of high relative humidity.