超声波振动在Ce-Zr-La/Al2O3及负载型Pd三效催化剂制备中的应用

制备了CeO2-ZrO2-La2O3/Al2O3材料, 在制备过程中使用超声波振动对材料进行处理, 并以此材料为载体制备了单Pd三效催化剂. 对所制备的载体进行了织构性能分析(BET)和X射线衍射(XRD)表征. 对催化剂进行了NO程序升温脱附(NO-TPD)及H2程序升温还原(H2-TPR)表征, 并对催化剂进行了活性测试. BET结果表明, 900 ℃焙烧后, 超声波振动处理的载体比表面积为130 m2·g-1, 而没有进行处理的载体比表面积为117 m2·g-1. 超声波处理的CeO2-ZrO2-La2O3/Al2O3材料介孔直径为11.4 nm, 相对较大, 载体更加稳定. XRD测试结果表明, 超声波处理的载体在1150 ℃焙烧5 h后仍然只有Ce0.5Zr0.5O2一个单一物相, 而未经过超声波处理的载体此时出现相分离, 体相中有θ-Al2O3出现. 以超声波处理材料为载体的Pd催化剂新鲜和老化后NO-TPD测试结果变化很小. H2-TPR测试中, 超声波振动处理的材料制备的催化剂中活性组分和载体的还原峰温较未超声处理材料制备的催化剂稍高, 而峰面积远大于未超声处理材料制备的催化剂. 活性测试结果说明, 由超声波振动处理过的载体制备的三效催化剂对汽车尾气中的三种污染物的起燃温度更低, 有更好的活性以及温度特性.

Application of Ultrasonic Vibrations in the Preparation of Ce-Zr-La/Al2O3 and Supported Pd Three-Way-Catalyst

CeO2-ZrO2-La2O3/Al2O3 (CZLA) was prepared by pretreatment with ultrasonic vibrations and Pd three-way-catalysts (TWCs) were then synthesized. Supports were characterized using Brunauer-Emmett-Teller(BET) and X-ray diffraction (XRD). Pd catalysts were characterized using NO-temperature programmed desorption (NO-TPD), H2-temperature programmed reduction (H2-TPR) and a catalytic activity test. The specific surface area of the uv-CZLA (CZLA with ultrasonic vibration) and the n-CZLA (CZLA without ultrasonic vibration) was 130 and 117 m2·g-1, respectively, after calcination at 900 ℃. The uv-CZLA material had larger pores of 11.4 nm and this made it more thermally stable than the n-CZLA. uv-CZLA supports were calcined at various temperatures and showed only one Ce0.5Zr0.5O2 phase. However, θ-Al2O3 was observed in n-CZLA after aging at 1150 ℃for 5 h. Almost no difference in NO-TPD was found for fresh and aged Pd/uv-CZLA catalysts. Results from the H2-TPR of the Pd/uv-CZLA catalyst showed a higher reductive peak temperature and a far larger reducing peak area than that of Pd/n-CZLA. Results of three-way reactions show that the catalyst prepared using ultrasonic vibration treatment possesses a lower light-off temperature for the removal of all three main pollutants in vehicle emissions and also a better temperature property.