催化学报 ›› 2016, Vol. 37 ›› Issue (1): 83-90.DOI: 10.1016/S1872-2067(15)60913-5

• 新型多孔催化材料专栏 • 上一篇    下一篇

CeO2纳米管负载Pd纳米颗粒催化CO低温氧化

吴静谧a, 曾亮b, 程党国a, 陈丰秋a, 詹晓力a, 巩金龙b   

  1. a 浙江大学化学工程与生物工程学院, 生物质化工教育部重点实验室, 浙江杭州310027;
    b 天津大学化工学院, 绿色合成与转化教育部重点实验室, 天津化学化工协同创新中心, 天津300072
  • 收稿日期:2015-04-30 修回日期:2015-05-27 出版日期:2015-12-26 发布日期:2015-12-26
  • 通讯作者: 程党国, 巩金龙
  • 作者简介:程党国, 巩金龙
  • 基金资助:

    国家自然科学基金(21376209, 21376169); 浙江省自然科学重点基金(LZ13B060004); 浙江省重点科技创新团队计划(2013TD07); 高等学校学科创新引智计划(B06006).

Synthesis of Pd nanoparticles supported on CeO2 nanotubes for CO oxidation at low temperatures

Jingmi Wua, Liang Zengb, Dangguo Chenga, Fengqiu Chena, Xiaoli Zhana, Jinlong Gongb   

  1. a Key Laboratory of Biomass Chemical Engineering of Ministry of Education, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou 310027, Zhejiang, China;
    b Key Laboratory for Green Chemical Technology of Ministry of Education, School of Chemical Engineering and Technology, Tianjin University; Collaborative Innovation Center of Chemical Science and Engineering, Tianjin 300072, China
  • Received:2015-04-30 Revised:2015-05-27 Online:2015-12-26 Published:2015-12-26
  • Supported by:

    This work was supported by the National Natural Science Foundation of China (21376209, 21376169), Zhejiang Provincial Natural Science Foundation (LZ13B060004), Program for Zhejiang Leading Team of S&T Innovation (2013TD07), and Program of Introducing Talents of Discipline to Universities (B06006).

摘要:

高效负载型Pd催化剂的制备及其在CO低温氧化反应中的机理探究是近年来的研究热点.普遍认为,Pd催化剂上的CO氧化反应遵循Langmuir-Hinshelwood机理:首先,CO吸附于Pd物种表面; 然后,CO与催化剂表面的晶格氧发生反应转化为CO2,反应发生在金属-载体界面.另外,高分散的Pd活性物种有利于CO氧化反应.同时载体的形貌、暴露的晶面、氧空位以及孔结构等都是影响催化剂活性的重要因素.CeO2纳米管具有独特的管状特征和较高的比表面积,是一种潜在的CO低温氧化催化剂载体.
本文利用乙醇还原法,以CeO2纳米管为载体,制备不同Pd含量的Pd/CeO2-nanotube纳米催化剂,并利用N2吸附脱附、X射线衍射(XRD)、透射电子显微镜(TEM)、CO程序升温脱附(CO-TPD)、X射线光电子能谱(XPS)等表征手段,探索纳米催化剂载体形貌对CO氧化反应活性的影响.氮气吸脱附结果表明,Pd/CeO2-nanotube具有较高的比表面积(58.0m2/g),且存在介孔结构.XRD表征发现,Pd/CeO2-nanotube的衍射峰对应立方萤石型结构的CeO2的(111),(200),(220),(311)等晶面.TEM结果表明,Pd/CeO2-nanotube具有均匀的纳米管形貌,其外径为40-60nm,Pd纳米颗粒均匀分散在其表面.CO-TPD结果表明,Pd/CeO2-nanotube在110oC附近具有很强的脱附峰,在370oC和600oC附近分别具有较宽和较弱的脱附峰,这表明该催化剂具有较多的吸附位,且具有很强的CO吸附能力; CO不可逆吸附量计算结果表明,该催化剂上的Pd具有很高的表面分散度(23.3%),Pd颗粒尺寸为7.3nm.XPS表征显示,Pd以Pd2+的形式分散于CeO2纳米管的表面,且与载体发生相互作用,存在Pd-O-Ce键;同时该催化剂表面存在丰富的Ce3+,为反应提供更多的氧空位.0.9Pd/CeO2-nanotube纳米催化剂在CO氧化反应中表现出优良的活性,能在100℃实现CO的完全转化; 通过计算发现,该催化剂具有较高的TOF值(0.63s-1),由Arrhenius曲线可得到该催化剂的活化能为26.5kJ/mol.
综上可见:金属活性组分的尺寸和分散度、载体的结构特征、CO吸附能力以及金属-载体间的相互作用决定催化剂的性能.Pd/CeO2-nanotube的高比表面积有利于Pd的分散; 其强CO吸附能力有利于CO吸附于Pd物种表面; 催化剂表面丰富的Ce3+能为反应提供更多的氧空位,Pd-O-Ce键的形成能增强金属-载体间的相互作用,有利于CO与催化剂表面晶格氧发生反应.同时催化剂介孔结构有利于反应气体和产物气体的吸附和扩散,因此,Pd/CeO2-nanotube纳米催化剂在CO氧化反应中表现出优良的活性.

关键词: 氧化铈纳米管, 钯纳米颗粒, 金属-载体相互作用, 一氧化碳氧化, 低温

Abstract:

Developing efficient supported Pd catalysts and understanding their catalytic mechanism in CO oxidation are challenging research topics in recent years. This paper describes the synthesis of Pd nanoparticles supported on CeO2 nanotubes via an alcohol reduction method. The effect of the support morphology on the catalytic reaction was explored. Subsequently, the performance of the prepared catalysts was investigated toward CO oxidation reaction and characterized by Nitrogen sorption, X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and CO-temperature-programmed desorption techniques. The results indicated that the catalyst of Pd on CeO2 nanotubes exhibits excellent activity in CO oxidation at low temperatures, due to its large surface area, the high dispersion of Pd species, the mesoporous and tubular structure of the CeO2-nanotube support, the abundant Ce3+, formation of Pd-O-Ce bonding, and enhanced metal-support interaction on the catalyst surface.

Key words: Cerium oxide nanotube, Palladium nanoparticle, Metal-support interaction, Carbon monoxide oxidation, Low temperature