催化学报 ›› 2016, Vol. 37 ›› Issue (10): 1721-1728.DOI: 10.1016/S1872-2067(16)62469-5

• 论文 • 上一篇    下一篇

氧化铈促进的高效Au/Al2O3催化剂制备及其催化CO选择氧化反应性能

苗雨欣, 王静, 李文翠   

  1. 大连理工大学化工学院, 精细化工国家重点实验室, 辽宁大连 116024
  • 收稿日期:2016-04-26 修回日期:2016-05-20 出版日期:2016-10-21 发布日期:2016-10-22
  • 通讯作者: Wen-Cui Li
  • 基金资助:

    国家重点基础研究发展计划(973计划,2013CB934104);国家自然科学基金(21225312,U1303192).

Enhanced catalytic activities and selectivities in preferential oxidation of CO over ceria-promoted Au/Al2O3 catalysts

Yu-Xin Miao, Jing Wang, Wen-Cui Li   

  1. State Key Laboratory of Fine Chemicals, School of Chemical Engineering, Dalian University of Technology, Dalian 116024, Liaoning, China
  • Received:2016-04-26 Revised:2016-05-20 Online:2016-10-21 Published:2016-10-22
  • Contact: Wen-Cui Li
  • Supported by:

    This work was supported by the National Basic Research Program of China (973 Program, 2013CB934104) and the National Natural Science Foundation of China (21225312, U1303192).

摘要:

近年来,伴随全球能源危机的加剧,以及温室效应和细颗粒物等一系列环境问题出现,各国研究者正努力寻求和开发可持续利用的新能源来代替传统的化石能源.燃料电池具有能量转化效率高、对环境排放低和污染小等优点,作为一种新的环境友好型技术而广受关注.在众多的燃料电池中,质子交换膜燃料电池(PEMFC)因具有能量效率高和工作窗口温度低等优势而备受关注.但是,PEMFC燃料以H2为主,主要来源是烃类的重整气,但其中痕量的CO(10 ppm)将会引起Pt电极中毒,导致PEMFC性能迅速下降,因此如何有效地祛除富氢气体中的CO并尽可能减少H2的消耗具有重要研究价值.目前,CO选择氧化法(CO-PROX)是公认的最简单、廉价和有效的办法之一.CO的消除通常选用霍加拉特催化剂,虽然Cu基催化剂具有低廉的成本和较好的CO催化氧化性能,但是当反应中有H2O和CO2存在时,其活性会迅速下降.Au催化剂具有优异的低温CO催化氧化性能,但在PEMFC的工作温度窗口为80-120℃时,随着反应温度提高,H2与CO之间的竞争吸附变强,采用单组分Au催化剂难于在80-120℃内使CO完全氧化.因此,设计并制备高效的Au催化剂来提高其在PEMFC工作温度(80-120℃)条件下CO-PROX反应活性和选择性仍然是目前该方向的难点.
氧化铈(CeO2)是一种重要的稀土化合物,由于Ce具有独特的4f电子层结构,Ce3+/Ce4+在一定条件下可以相互转化,具有较高的储放氧能力,即能够在富氧条件下储存氧,在贫氧条件下释放氧.CeO2是一种重要的氧化反应催化剂载体,是三效催化剂的主要组成部分,在净化汽车尾气方面稀土元素具有独特的优势,广泛应用于CO氧化和NOx消除等领域中.最近,本课题组以自制的氧化铝为载体,制备了K掺杂的Au-Cu/Al2O3催化剂,其在CO-PROX反应中具有较好的催化活性和稳定性.本文在此基础上,利用Au与CeO2之间的相互作用,制备了CeO2掺杂的Au/CeO2/Al2O3催化剂和K掺杂的Au-Cu/CeO2/Al2O3催化剂.表征结果发现,催化剂中Au和Au-Cu纳米粒子的尺寸均一,平均粒径分别为2.4 ± 0.4和2.8 ± 0.4 nm.与Au/Al2O3催化剂相比,Ce掺杂的Au催化剂具有更高的金属分散度,拓宽了其CO完全转化时的反应温度窗口(30-70℃).对所制备的Au催化剂进一步通过拉曼光谱、H2程序升温还原和CO-红外光谱等手段分析和CO-PROX催化性能测试,可以证实Au-Cu/CeO2/Al2O3催化剂中各组分在CO-PROX反应中所起的作用.结果表明,CeO2的掺杂能增强活性组分与载体之间的相互作用,有助于提高Au-Cu纳米粒子的分散度,此外还能提高Au催化剂的还原性能,其表面形成的氧空位提高了CO-PROX反应的催化性能.Cu物种的引入显著增强了CO在Au催化剂上吸附能力.综上所述,CeO2组分对Au/Al2O3催化剂的促进作用体现在:(1)有效锚定Au和Au-Cu纳米粒子;(2)提供CO-PROX反应中的活性氧物种.

关键词: 金催化, 氧化铈, 氧化铝, 一氧化碳选择氧化, 沉积沉淀法

Abstract:

The preferential oxidation of CO (CO-PROX) is a hot topic because of its importance in pro-ton-exchange membrane fuel cells (PEMFCs). Au catalysts are highly active in CO oxidation. However, their activities still need to be improved at the PEMFC operating temperatures of 80-120℃. In the present study, Au nanoparticles of average size 2.6 nm supported on ceria-modified Al2O3 were synthesized and characterized using powder X-ray diffraction, nitrogen physisorption, transmission electron and scanning transmission electron microscopies, temperature-programmed hydrogen reduction (H2-TPR), Raman spectroscopy, and in situ diffuse-reflectance infrared Fourier-transform spectroscopy. Highly dispersed Au nanoparticles and strong structures formed by Au-support interactions were the main active species on the ceria surface. The Raman and H2-TPR results show that the improved catalytic performance of the Au catalysts can be attributed to enhanced strong metal-support interactions and the reducibility caused by ceria doping. The formation of oxygen vacancies on the catalysts increased their activities in CO-PROX. The synthesized Au catalysts gave excellent catalytic performances with high CO conversions (>97%) and CO2 selectivities (>50%) in the temperature range 80-150℃.

Key words: Gold catalysis, Ceria, Alumina, Preferential oxidation of carbon monoxide Deposition-precipitation