锆钛复合氧化物的制备及用作Pt三效催化剂载体的性能

用共沉淀法制备了Zr_0.5Ti_0.5O₂复合氧化物, 考察了沉淀时的pH值、温度及焙烧温度对样品织构性能的影响. 分别用BET、XRD、NH₃-TPD 对样品的织构、结构性能和表面酸性进行了表征. 将经过不同温度焙烧后的样品作为载体制备成Pt/Zr_0.5Ti_0.5O₂催化剂, 考察了催化剂对C₃H₈、CO、NO 的催化性能, 并与传统的以La-Al₂O₃为载体的Pt/La-Al₂O₃汽车尾气三效催化剂进行了比较. 结果表明: 当沉淀时的pH=11、温度为25℃、焙烧温度为550℃时, 所制得的样品具有较好的织构性能(比表面积为195m²· ^-1、孔容为0.28mL·g ^-1)、较强的表面酸性和较宽的酸度分布; 用该样品制备的汽车尾气三效催化剂与传统的以La-Al2O3作载体的Pt/La-Al₂O₃催化剂相比, 具有更好的HC和CO催化性能和优异的NO转化性能.

Preparation of Titanium-Zirconium Mixed Oxide and its Catalytic Performance of Pt Three-way Catalysts

Zr_0.5 Ti_0.5 O₂ mixed oxides were prepared by co-precipitation method. The effects of pH value, precipitation temperature and calcination temperature of Zr_0.5 Ti_0.5O ₂ on its specific surface area, pore size, pore volume and surface acidity were investigated. The samples calcined at 500℃, 550℃, 600℃, 650℃, 700℃, 800℃ for 2h, were characterized by means of BET, X-ray diffraction (XRD) and NH3-temperature programmed desorption (NH₃-TPD). Using the Zr_0.5Ti_0.5O₂ and La-Al₂O₃ as catalyst carriers, and the activities of Pt/Zr_0.5 Ti_0.5O₂ and Pt/La-Al₂O₃ catalysts were evaluated in the simulated gas. The results show that when the pH is 11, precipitation temperature is 25℃, calcination temperature is 550℃, Zr_0.5Ti_0.5O₂ exhibits the highest specific surface area(195m²·^-1), larger pore volume(0.28mL·g ^-1), proper surface acidic amount and acidity. Compared with Pt/La-Al₂O₃, Pt/Zr_0.5Ti_0.5O₂ exhibits excellent low-temperature catalytic activity and lower the light-off temperature of hydrocarbon (234℃) and carbon monoxide (203℃) and nitrogen oxides (213℃). At the same time, it is found that the Pt/Zr_0.5Ti_0.5O₂ catalysts significantly improve the conversion for nitrogen oxides.