Preparation And Catalytic Performance Of Pd-Cu-Cl_x/Al₂O₃ For Low Temperature CO Oxidation

Low temperature CO catalytic oxidation is an important reaction because of its wild applications of military, industry, environment production and daily life. When catalyst was used in natural environment, the inevitable thing was the negative influence of moisture, halogen compounds, SO2, CO2 and some on. Hence, the improvement of catalytic activity and stability over CO oxidation catalyst is a very important subject for academic value and practical significance.In this paper, the influence of preparation method for physicochemical and catalytic properties of Pd-Cu-Clx/Al2O3 catalyst was studied. The physicochemical and catalytic properties were characterized by BET, XRD, H2-TPR, TEM, EDS and ICP-OES; the adsoption and reaction condition on catalyst surface was investigated by in situ DRIFTS; the apparent activation energy and the adsoption of H2O and CO on the surface were discussed by kinetics characters and DFT calculations, respectively. The main results as follows:A two-step impregnation method was designed to prepare the Pd-Cu-Clx/Al2O3(PCC-TI) catalyst. The influence of solvents, additives, the third component, calcination temperature and copper contents were investigated.The results show that, in the presence of 3.1% moisture, the 1.7wt%Pd-3.3wt%Cu-Clx/Al2O3that calcined at 300℃ exhibits the best activity, the CO was completely convert at 10℃.PCC-TI/ethanol (ethanol as the solvent) shows the best activity and stability compared with the Pd-Cu-Clx/Al1O2catalysts prepared by wet impregnation (WI) and NH3 coordination-impregnation (CI) methods, which due to the stronger interaction between Pd and Cu species and the higher dispersion of Cu species on the catalyst surface.The influence of moisture and CO over PCC-TI/ethanol was investigated. The result shows that the catalytic performance was inhibited by high concentration of moisture and CO.The former was coming from the excessive -OH groups occupied on the Al2O3 surface active sites, and the latter might be originated from the covering of carbonates on the catalyst surface. The deactivation was also studied under high moisture condition. The result shows that, when moisture concentration was low, the deactivation was associated with the aggregation of Cu species. And under the higher moisture condition, the deactivation was resulted from the aggregation, production of CuCl phase and the covering of carbonates on the catalyst surface.