【作者】 甄小娟；

【导师】 王军；

【作者基本信息】 天津大学 ， 化学工程， 2007， 硕士

【摘要】 以Pt、Rh、Pd贵金属为主的三效催化剂是控制汽油车尾气污染的重要方法。单钯（Pd）催化剂由于具有相对低廉的价格、丰富的资源和良好的低温催化活性,成为汽车尾气三效催化剂的研究热点之一。本论文针对Pd/CZ/Al₂O₃模型催化剂,对制备单钯催化剂的的浸渍工艺和参数进行了研究和优化,为汽油车尾气单钯催化剂的研发提供理论支持。本论文采用浸渍法,考察了Pd前驱液浓度、浸渍次数,浸渍次序和焙烧次序对催化剂的催化活性和动态储放氧性能的影响;结合XRD、BET、TPR和贵金属分散度等表征手段,分析了贵金属形貌,贵金属与载体作用对催化剂的三效催化性能、动态储放氧性能的影响。研究表明:前驱液浓度和浸渍次数与催化剂的催化活性不是单调递增或递减的关系,存在最优的前驱液浓度和浸渍次数有利于提高催化剂的催化性能和储放氧性能。分散度表征结果表明最优的前驱液浓度和浸渍次数提高了Pd的分散度,增加了催化剂的表面活性位,增强了Pd的抗烧结能力。浸渍次序和焙烧次序结果表明Pd与CZ作用对CO转化有利,Pd与Al₂O₃作用对HC和NO转化有利,TPR结果显示Pd的浸渍次序影响了新鲜催化剂中Pd与载体的作用方式,高温老化后Pd在载体上的分布趋于一致。更多还原

【Abstract】 Comparing with Pt and Rh, Pd is more abundant in resource, cheaper and better at light-off performance among the three kinds of rare-mental active components of TWC catalyst, and the Pd-only catalyst is playing more and more important role in the automotive emission control materals.This paper investigated the impregnation technics of Pd/CZ/Al₂O₃ catalyst, optimized the technics parameters and provided data for the further study of Pd-only catalyst.The paper prepared the Pd/CZ/Al₂O₃ catalyst by impregnation method. The effect of Pd precursor concentration, the number of single-dipping, Pd addition order and calcining sequence on the three-way catalytic activity and dynamic oxygen storage capacity of the catalysts were studied and analysed combining with XRD, BET, TPR and noble metals dispersion.The results of Pd precursor concentration and the number of single-dipping show that: There is not a monotony increase or decrease by degrees of Pd precursor concentration or the single-dipping number versus the three-way catalytic activity, but they have optimized values. Noble metal dispersion shows that Pd dispersion is elevated at that value, the active sites is increased and the agglomeration of Pd particle is prevented.The results of Pd addition order and calcining sequence indicate that: Pd/CZ interaction has an advantage over the conversion of CO while Pd/Al₂O₃ interaction has an advantage over the conversion of HC and NO. TPR result shows that the interaction mode between Pd and carrier is affected by Pd addition order and calcined sequence before aging and the distribution of Pd over the catalysts keeps consistent after aged.更多还原