催化学报 ›› 2017, Vol. 38 ›› Issue (3): 607-616.DOI: 10.1016/S1872-2067(17)62781-5

• 论文 • 上一篇    

载体硫酸化对柴油机尾气催化剂Pt/Ce-Zr活性和稳定性的影响

顾蕾a, 陈晓a, 周瑛b, 朱秋莲b, 黄海凤a, 卢晗锋b   

  1. a 浙江工业大学环境学院, 浙江杭州 310014;
    b 浙江工业大学化学工程学院, 浙江杭州 310014
  • 收稿日期:2016-12-08 修回日期:2017-01-04 出版日期:2017-03-18 发布日期:2017-03-22
  • 通讯作者: Haifeng, Hanfeng Lu
  • 基金资助:

    国家自然科学基金(21506194,21676255);浙江省自然科学基金(LY16B070011);浙江省科技厅项目(2017C33106,2017C03007).

Propene and CO oxidation on Pt/Ce-Zr-SO42- diesel oxidation catalysts: Effect of sulfate on activity and stability

Lei Gua, Xiao Chena, Ying Zhoub, Qiulian Zhub, Haifeng Huanga, Hanfeng Lub   

  1. a College of Environmental Engineering, Zhejiang University of Technology, Hangzhou 310014, Zhejiang, China;
    b Institute of Catalytic Reaction Engineering, College of Chemical Engineering, Zhejiang University of Technology, Hangzhou 310014, Zhejiang, China
  • Received:2016-12-08 Revised:2017-01-04 Online:2017-03-18 Published:2017-03-22
  • Supported by:

    This work was supported by the National Natural Science Foundation of China (21506194, 21676255), the Provincial Natural Science Foundation of Zhejiang Province (LY16B070011), and the Commission of Science and Technology of Zhejiang Province (2017C33106, 2017C03007).

摘要:

近年来,随着大气环境污染问题日益严重,汽车尾气排放受到政府越来越严苛的控制.柴油车排气成分主要包括碳氢化合物(HC)、一氧化碳(CO)、氮氧化物(NOx)、微粒(PM)和二氧化硫(SO2),因此常用的尾气后处理系统有颗粒捕获器(DPF)、氧化型催化转换器(DOC)以及NOx选择还原系统(SCR),在处理尾气时三者联合使用.其中柴油机氧化型催化剂(DOC)是汽车尾气后处理装置的重要组成部分,主要用于氧化CO,HC和NO,可以将CO和HC氧化成无害的CO2和H2O,将NO氧化成NO2,为后续SCR反应提供条件.
柴油机排气温度一般较低(150-400℃),特别是在冷启动阶段,排气温度可降低到100℃左右,要求催化剂具有良好的低温催化活性.此外,由于柴油中存在少量含硫有机化合物,经过燃烧分解,使得柴油机尾气中含有少量SO2,对催化剂又有钝化作用,因此催化剂的抗硫性也是需要关注的重点.
本文采用浸渍法制备Pt/Ce-Zr-SO42-催化剂,考察了催化剂载体硫酸化以及Pt和H2SO4的负载顺序对催化剂催化氧化C3H6和CO的活性及抗硫性的影响,并且对Pt/Ce-Zr-SO42-催化剂进行了一系列表征,探究其物理化学性质.结果表明,SO42-的添加能有效提高催化剂活性.Pt/CZ-10S对C3H6和CO的T90(转化率为90%时的温度)相较于Pt/CZ催化剂降低了约75℃,另外,Pt/CZ-10S催化剂也表现出较好的抗硫稳定性,在含硫尾气中240℃反应20 h后,其对C3H6和CO的转化率仍保持在95%以上.CO-TPD和XPS分析结果显示,Ce-Zr-SO42-载体上Pt的分散度增加,增加的Pt颗粒可以产生更多新的活性位点(Pt&+-(SO42-&- couples),从而表现出优异的催化活性.此外,硫酸化后催化剂表面酸性的变化也是其抗硫性能提高的原因.

关键词: 柴油车尾气氧化催化剂, Pt/Ce-Zr-SO42-催化剂, 抗硫性, 催化氧化

Abstract:

Platinum/cerium-zirconium-sulfate (Pt/Ce-Zr-SO42-) catalysts were prepared by wetness impregnation. Catalytic activities were evaluated from the combustion of propene and CO. Sulfate (SO42-) addition improved the catalytic activity significantly. When using Pt/Ce-Zr-SO42- with 10 wt% SO42-, the temperature for 90% conversion of propene and CO decreased by 75℃ compared with Pt/Ce-Zr. The conversion exceeded 95% at 240℃ even after 0.02% sulfur dioxide poisoning for 20 h. Temperature-programmed desorption of CO and X-ray photoelectron spectroscopy analyses revealed an improvement in Pt dispersion onto the Ce-Zr-SO42- support, and the increased number of Pt particles built up more Pt&+-(SO42-)&- couples, which resulted in excellent activity. The increased total acidity and new Brönsted acid sites on the surface provided the Pt/Ce-Zr-SO42- with good sulfur resistance.

Key words: Diesel oxidation catalyst, Pt/Ce-Zr-SO42- catalyst, Sulfur resistance, Catalytic oxidation