| The application of catalytic invert technique is the most effective method to realize automotive exhaust purification (over Euro-Ⅲstandard). High performance thulium modified alumina material (ACZO) is the pivotal component in the catalysts of automotive exhaust purification, and it has been applied in practice. High performance ACZO material need to have high thermal stability, high surface area and high oxygen-storage capacity. Catalytic invert instrument is near to the vent of the engine during practical application. ACZO material only having high oxygen-storage capacity and velocity is not enough. It needs to have the performance of high thermal stability and large surface area.γ-Al2O3 is one of supports of the catalysts which are the most far-ranging application. But the problem of thermal stability of Al2O3 is a long-term one which people is puzzled by, especially in the atmosphere of high temperature and vapor being present at. Al2O3 is easy to take place phase transition and sinter, and it evolves toα-phase being steady in thermodynamics and large particle causing a drastic decrease in the surface area. This is one of important reasons which contribute to the thermal deactivation of the catalysts. Therefore, investigation and exploitation of new thulium modified alumina material with high thermal stability and high surface area has importantly academic and practical significance for improving durability and cold-starting performance of three-way catalysts for automotive exhaust purification.The CexZr1-x-Al supports are synthesized by sol-gel methods, and the supports are dried by supercritical drying in alcohol. The Pd/CexZr1-x-Al catalysts are tested for exhaust pollution destruction. At the same time, bulk composition and redox behavior over these catalysts are characterized by some experiments. Some specific conclusions are drawn from this work as follows:1 The CexZr1-x-Al mixed oxides are prepared by Sol-gel and supercritical drying technique. The BET surface areas of CexZr1-x-Al (x≦0.75) are higher than 96m2/g.2 Automotive exhaust purification over Pd/CexZr1-x-Al (mol ratio) catalysts has been studied. The Pd/Ce0.75Zr0.25-Al catalyst exhibits the highest catalytic activity, thermal stability and oxygen-storage capacity. The catalytic activity is related with the reducibility of PdO dispersed on Ce-Zr-Al-rich grains and the capacity of oxygen desorption under lower temperature.3 Effects of Ce-Zr loading on exhaust pollution purification over Pd/Ce0.75Zr0.25-Al catalysts have been studied. When Ce-Zr loading is 18wt%, the catalyst exhibits the highest catalytic activity and oxygen-storage capacity for transition of CO, HC and NOx.4 Effects of Pd loading on exhaust pollution purification over Pd/Ce0.75Zr0.25-Al catalysts have been studied. As the quantity of Pd loading increases, the catalytic activity of the catalysts for transition of CO,HC and NOx obviously improves. But, when the quantity of Pd loading comes to 1%, the improvement of the catalytic activity is smaller. After the catalysts are calcined at 1100℃, dispersion states of PdO species on the catalysts of higher Pd-loading quantity take place remarkable change. Part of PdO species may have the phenomenon of redispersion.5 Effects of treatment temperature of supports and catalysts on exhaust pollution purification over Pd/Ce0.75Zr0.25-Al catalysts have been studied. Effect of treatment temperature of supports or catalysts on dispersion states of PdO species is different. After the catalysts are calcined at high temperature, dispersion states of PdO species have no intrinsical change, but effect of treatment temperature of supports on dispersion states of PdO species is remarkable. As treatment temperature of supports improves, quantity ofα-PdO species evidently decreases, while quantity ofβ-PdO species observably increases. Effect of treatment temperature of supports or catalysts on surface and crystal oxygen desorption is almostly same, and it is desided by thermal stability of supports. It depends on thermal stability of supports.6 Effects of the fountain of alumina on exhaust pollution purification over Pd/Ce0.75Zr0.25-Al catalysts have been studied. The Pd/Ce0.75Zr0.25-Al catalyst that alumina comes from Al(NO3)3·9H2O exhibits the higher catalytic activity, thermal stability and oxygen-storage capacity. The Pd/Ce0.75Zr0.25-Al catalyst that alumina comes from Al(NO3)3·9H2O has higher reducibility than The Pd/Ce0.75Zr0.25-Al catalyst that alumina comes from NaAlO2. Oxygen desorption and the fluidity of crystal oxygen of the former is better than the later.
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