Synthesis Of YSZ-Al₂O₃mixed Oxides And Study On Their Catalytic Properties

As the standards for automotive exhaust emission have got stricter and stricter,which requiring better advanced activity and thermal stability of automotive catalysts.YSZ-Al2O3mixed oxides have many unique characteristics such as strong acid site,large specific surface area and high thermal stability, YSZ-Al2O3mixed oxides havebeen used in the petrochemical industry.In this dissertation, the factors affect the dispersion of zirconia, physical andchemical performance of YSZ-Al2O3mixed oxides, such as the content of zirconia,precipitants, solvent, temperature, pH, surfactants were studied, when YSZ-Al2O3mixed oxides were synthesized with the deposition-precipitation and solvothermalmethod.A series of YSZ-Al2O3mixed oxides were prepared by many preparationmethods with the best effect factors. Then the affect adding manganese additives oncatalyst performance was studied. The phase composition, texture property, dispersionof noble metals and redox property of the materials and catalysts were studied by BET,XRD, O2-TPD, H2-TPR and CO pulse chemisorption. The activities for the reactionNO and CO of catalysts after calcined at different temperatures were measured.The results indicate that the particles of zirconia with high distribution on thesurface of Al2O3in the YSZ-Al2O3mixed oxides can be prepared by thedeposition-precipitation methods using urea as precipitant. when the mass percent ofzirconia is20%, the surface area of YSZ-Al2O3mixed oxides calcined at800℃for4h is183m2/g,and then change to82m2/g after calcined at1000℃for4h.When pHis9.0. Zirconium ion can not be completely settle down by using Ammoniumcarbonate as precipitant. The surface area of the YSZ-Al2O3mixed oxides prepared bysolvothermal method using the Non-polar solvent are larger than those using the polarsolvent. The YSZ-Al2O3mixed oxides prepared by hydrothermal method have largersurface area and better thermal stability, when the pH is7.0. The surface area andthermal stability of the YSZ-Al2O3mixed oxides can be improved by adding5wt%PEG-6000as surfactant. The YSZ-Al2O3mixed oxides prepared by the method mixing the precipitation method and the hydrothermal method have larger surfacearea and better thermal stability in which the particles of ZrO2with high distributionon the surface of Al2O3.The surface area of YSZ-Al2O3mixed oxides calcined at800℃for4h is188m2/g,and then change to90m2/g after calcined at1000℃for4h.The results show that the the YSZ-Al2O3mixed oxides in which the particles ofZrO2with high distribution on the surface of Al2O3can effectively inhibit theinteraction between alumina and rhodium The thermal stability of carrier materialsand the distribution of Rh on carrier materials were improved. The redox property andactivity of catalysts were improved. Adsorbed oxygen and lattice oxygen weresignificantly increased by adding manganese additives.The activity of the catalystswere improved.