催化学报 ›› 2017, Vol. 38 ›› Issue (8): 1406-1412.

• 论文 • 上一篇    下一篇

制备方法对LaMnO3上氯乙烯催化燃烧性能的影响

王丽a, 谢鸿凯a, 王杏丹a, 张桂珍b, 郭杨龙a, 郭耘a, 卢冠忠a   

  1. a 华东理工大学化学与分子工程学院工业催化研究所, 先进功能材料重点实验室, 上海 200237;
    b 北京工业大学环境与能源工程学院化学与化学工程系, 北京 100124
  • 收稿日期:2017-04-11 修回日期:2017-05-12 出版日期:2017-08-18 发布日期:2017-08-04
  • 通讯作者: 郭耘
  • 基金资助:

    国家重点基础研究发展计划(2013CB933201);国家自然科学基金(21207037,21577035);上海市科委项目(15DZ1205305).

Preparation of LaMnO3 for catalytic combustion of vinyl chloride

Li Wanga, Hongkai Xiea, Xingdan Wanga, Guizhen Zhangb, Yanglong Guoa, Yun Guoa, Guanzhong Lua   

  1. a Key Laboratory for Advanced Materials and Research Institute of Industrial Catalysis, School of Chemistry & Molecular Engineering, East China University of Science and Technology, Shanghai 200237, China;
    b Department of Chemistry and Chemical Engineering, College of Environmental and Energy Engineering, Beijing University of Technology, Beijing 100124, China
  • Received:2017-04-11 Revised:2017-05-12 Online:2017-08-18 Published:2017-08-04
  • Supported by:

    This work was supported by the National Basic Research Program of China (2013CB933201), the National Natural Science Foundation of China (21207037, 21577035) and the Commission of Science and Technology of Shanghai Municipality (15DZ1205305).

摘要:

含氯挥发有机物(CVOCs)广泛用于化工原料以及有机溶剂,由于其毒性大,难降解,直接排放可引起严重的空气污染问题,采用催化燃烧的技术可以实现CVOCs高效净化,其关键在于高活性和高稳定性的催化剂.CVOCs净化催化剂主要有负载型贵金属催化剂、(复合)氧化物催化剂和复合分子筛催化剂.我们以具有高稳定性的LaMnO3钙钛矿为研究对象,主要考察了不同制备方法对于氯乙烯催化燃烧性能的影响;并通过XRD,Raman,N2-吸附脱附,O2-TPD,H2-TPR,ICP-AES,XPS等表征方法研究催化剂的结构和物化性能.
性能评价结果表明,MnO2虽具有良好的催化性能,但LaMnO3催化剂则具有更好的循环稳定性.同时,制备方法对LaMnO3催化剂上氯乙烯催化燃烧的性能有显著的影响,其活性高低的顺序为:溶胶凝-胶法(SG) > 共沉淀法(CP) > 硬模版剂法(HT) > 水热法(HM),其中LaMnO3-SG催化剂在182℃时氯乙烯的转化率即可达到90%.
XPS结果表明,不同的制备方法导致LaMnO3催化剂表面La和Mn的富集程度不同,并显著影响了催化剂表面Mn离子的价态、分布和氧空穴的数量.其中,LaMnO3-SG催化剂具有最高的表面Mn4+浓度,其对应的氯乙烯催化燃烧活性最高.而对于LaMnO3-HM催化剂,La(OH)3的生成导致其具有最高的表面La/Mn比(2.29)和最低的表面Mn4+浓度.由XPS计算氧空穴浓度可知,LaMnO3-SG催化剂氧空穴浓度(1.03)远高于LaMnO3-HM催化剂表面的氧空穴浓度(0.07),进而LaMnO3-SG在O2-TPD中表现出更高的O2脱附量.进一步分析可知Mn4+离子浓度与氧空穴浓度成正相关的关系,即:Mn4+离子浓度越高,则表面氧空穴浓度越高.而催化剂表面氧空穴浓度越高,则有利于氧在催化剂表面的吸附和活化,从而使得催化剂表面氧物种的浓度增加,这与O2-TPD结果一致.同时,制备方法对催化剂氧化还原性能也有显著的影响,由H2-TPR所得催化剂的耗氢量顺序为:LaMnO3-SG > LaMnO3-CP > LaMnO3-HT > LaMnO3-HM,这与它们催化活性的顺序一致.结合XPS和H2-TPR结果可知,催化剂表面Mn4+/Mn3+比例高,则催化剂的氧化还原能力也越强.
以上分析表明,LaMnO3催化剂的催化活性与催化剂表面Mn4+浓度和氧空穴数量相关.具有较高的Mn4+浓度有利于氯乙烯在催化剂表面吸附;而氧空穴数量的增加有利于氧在催化剂表面的吸附和活化,从而提高氯乙烯催化燃烧的反应性能.

关键词: LaMnO3, 氯乙烯, 催化燃烧, 低温, 制备方法

Abstract:

LaMnO3 was prepared by citrate sol-gel, coprecipitation, hard template, and hydrothermal methods, respectively, and its catalytic performance for the combustion of vinyl chloride was investigated. N2 adsorption-desorption, X-ray diffraction (XRD), Raman spectroscopy (Raman), O2 temperature programmed desorption (O2-TPD), H2 temperature programmed surface reaction (H2-TPR) and X-ray photoelectron spectroscopy (XPS) were used to characterize the physicochemical properties of the LaMnO3 samples. The preparation methods had obvious effects on the distribution of oxygen and manganese species on the catalyst surface. The reaction followed the suprafacial mechanism; the activity corresponded with the high amount of Mn4+ and adsorbed oxygen species. LaMnO3 prepared by the citrate sol-gel method had the best performance for vinyl chloride combustion with T90 of 182℃. The optimal activity was attributed to the improved redox capability of Mn4+/Mn3+. More available adsorbed oxygen and Mn4+ species on the surface were mainly responsible for the remarkable enhancement of the catalytic activity.

Key words: LaMnO3, Vinyl chloride, Catalytic combustion, Low temperature, Preparation method