Study Of CuO/CeO₂-ZrO₂ Catalysts And Preparation Of Monolith Catalysts For Water-gas Shift Reaction

The first objective of this paper was to examine the effect of ZrO₂ on the structure and properties of CeO₂ supported Cu based catalyst to develop higher catalytic activity and stability catalysts for water-gas shift reaction. Another objective was to explore the effect of preparation procedures including the modification of cordierite substrate, the composition, pH and milling time of the coating slurry, and the optimal loadings for Cu based monolith catalyst on the catalytic properties.The low-temperature performance of catalysts has been shown to be strongly dependent on the preparation parameters. We find well parameters through series of experiments, as follows: metallic nitrate concentration 0.25mol/l, parallel co-precipitation, reaction temperature 60 ℃, pH>10 during precipitation and washing 12 times with deionized water.To understand how zirconia effect the structure and performance of CuO/CeO2-ZrO2 catalysts, XRD, N₂ physical adsorption, TPR and XPS analysis were carried out. And the steady kinetics of the water gas shift reaction over Cu/CeO₂ and CuO/CeO₂-ZrO₂ catalysts was investigated as well.It was found that the addition of ZrO₂ can all improve surface area of catalysts and ameliorate pore structure. With increasing of Zr content, the pore distribution of catalysts was centralized to smaller pore about 1.9nm gradually. Besides, modified appropriate ZrO₂ can boost the reduction of CuO and CeO₂, can availably restrain ceria crystallite growing, and can keep higher copper dispersion in the course of catalyzing WGSR process. When ZrO₂ content is 10at.% in catalysts, Cu/CeO₂-ZrO₂ catalyst exhibits higher activity for WGS reaction, with 73.7 % CO conversion at 200 ℃, and its activation energy is lower 7.04kJ/mol than Cu/CeO₂. Above all, the catalysts doped with zirconia showed higher activity and stability may be due to appropriate aperture and good redox ability which was resulted from the increasing of the surface oxygen vacancy concentration.To determine the optimal preparation procedures for Cu based monolith catalyst, BET, SEM and catalytic activity evaluation on WGSR were performed. The detailed parameters were listed as follows: cordierite without modified by acid; the coating slurry was composed with active catalyst powder, related salt as binding agent (the ratio of catalyst powder and salt is 4.5:1), triethanolamine as temporary binder, and citric acid to control pH at 4; 8 hours is good for the milling time; and the optimal washcoat loadings is 40%⁵0%. Monolith catalyst prepared as above exhibits higher activity for WGS reaction, with 68.5% CO conversion at 200 °C, 95.3% CO conversion at 350°C.