NaZr_2(PO_4)_3族载体负载的单钯三效催化剂的表征及催化活性研究

Characterization and Activity Tests of Palladium-only Three-way Catalysts Supported on NaZr_2(PO_4)_3 Carriers

具有低热膨胀特性的NaZr2(PO4)3(简称NZP)族材料是一类具有相同晶体结构但化学组成不同的新型抗热震催化剂载体材料,对用浸渍法制备的由NZP族载体负载的单钯三效催化剂进行了BET、XRD、TPR表征和活性评价,初步研究了不同化学组成的NZP族载体对单钯催化剂的物性和三效催化活性的影响。结果显示:组成为KZr2(PO4)3的载体负载的单钯催化剂1%Pd/KZr2(PO4)3对CO、CH和NOx的起燃温度分别为245℃、290℃和267℃,组成为CaZr4(PO4)6的NZP族载体经过15%CeO2改性后能够有效提高Pd的分散性,单钯催化剂1%Pd/15%CeO2-CaZr4(PO4)6的活性和空燃比窗口明显改善。此外,由NZP族载体负载的单钯催化剂表现出对NOx具有较好的催化还原活性,361℃下NOx的转化率达到100%。

NaZr2 （PO4）3 （简称 NZP） family materials with low thermal expansion coefficients are a new type of thermal shock resistance cartier which has the same crystalline structure but different chemical composition. In this paper, three way catalysts containing 1% Pd and supported on NZP family carriers such as KZr2 （PO4）3 and CaZr4 （PO4）6 were prepared by impregnation method. The physical properties of these catalysts were characterized by BET, XRD and TPR, and their activity was evaluated. The lighting temperatures of 1% Pd/KZr2 （PO4）3 for CO, CH and NOx are 245℃, 290℃ and 267℃, respectively. The dispersion of palladium can be improved efficiently by adding CeO2 into 1%Pd/ CaZr4（PO4）6, and the activity of 1%Pd/15% CeO2-CaZr4 （PO4）6 is increased as well as the ratio of air to fuel is widened. In addition, palladium-only catalysts supported on NZP family carriers show higher catalytic reduction activity to NOx, and the conversion of NOx is 100% at 360℃.