催化学报

催化学报 ›› 2017, Vol. 38 ›› Issue (3): 475-488.DOI: 10.1016/S1872-2067(17)62749-9

• 论文 • 上一篇    下一篇

Pt-CeO2/SiO2催化剂用于室温湿空气中CO氧化反应

Shirish S. Punde, Bruce J. Tatarchuk   

  1. 奥本大学化学工程系, 亚拉巴马州奥本市, 美国
  • 收稿日期:2016-08-05 修回日期:2016-08-29 出版日期:2017-03-18 发布日期:2017-03-22
  • 通讯作者: Shirish S. Punde
  • 基金资助:

    This work was supported by US Army contract (W56HZV-05-C0686) at Auburn University administered through TARDEC.

Pt-CeO2/SiO2 catalyst for CO oxidation in humid air at ambient temperature

Shirish S. Punde, Bruce J. Tatarchuk   

  1. Department of Chemical Engineering, Auburn University, Auburn, AL, USA
  • Received:2016-08-05 Revised:2016-08-29 Online:2017-03-18 Published:2017-03-22
  • Supported by:

    This work was supported by US Army contract (W56HZV-05-C0686) at Auburn University administered through TARDEC.

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摘要：

开发室温CO氧化催化剂的主要挑战是CO自中毒和慢的表面动力学，同时湿气的存在也可导致催化剂失活.本文开发了高活性CeO2促进的Pt基催化剂4%Pt-12%CeO2/SiO2，用于室温湿气（湿度10%-90%，25℃）中CO氧化反应，在低CO浓度（< 500 ppm）和高CO浓度（> 2500 ppm）时，CO转化率高于99%.优化了催化剂制备变量，如Pt和CeO2负载量、CeO2沉积方法、CeO2和Pt前驱体的干燥和焙烧条件.采用CO/H2化学吸附、O2-H2滴定、X射线衍射和BET比表面积测定表征了催化剂的表面特性，并将其与催化剂活性相关联.
结果表明，CeO2沉积方法对催化剂活性影响显著，当用浸渍法沉积CeO2时，所得催化剂的反应速率（5.77 μmol/g/s）比用沉积沉淀法（1.96 μmol g-1 s-1）或CeO2嫁接法（1.31 μmol g-1 s-1）制得催化剂的高3倍.O2-H2滴定结果表明，当用浸渍法沉积CeO2时，CeO2和Pt的紧密结合导致了催化剂的高活性.催化剂载体的选择也非常重要，硅胶负载的催化剂活性（5.77 μmol g-1 s-1）是氧化铝负载的（1.05 μmol g-1 s-1）5倍.当反应受内扩散控制时，催化剂载体的粒径和孔结构影响非常大.另外，CeO2和Pt前驱体的干燥和焙烧条件对催化剂活性的影响至关重要.当Pt和CeO2含量分别大于2.5和15 wt%时，所得催化剂在室温条件下活性高（TOF > 0.02 s-1），稳定性好（反应15 h，CO转化率 ≥ 99%）.

关键词: 一氧化碳氧化, 催化剂, 铂, 二氧化铈, 二氧化硅, 前驱体, 氢氧滴定, 化学吸附, 程序升温还原

Abstract:

CO self-poisoning and slow surface kinetics pose major challenges to a CO oxidation catalyst that should work at ambient temperature. Furthermore, the presence of moisture would cause passivation of the catalyst. A highly active ceria promoted Pt catalyst (4%Pt-12%CeO2/SiO2; conversion ≥ 99% at low (< 500 ppm) and high (> 2500 ppm) CO concentrations was developed for CO oxidation at ambient temperature in humid air. Catalyst preparation variables such as Pt and CeO2 loading, ceria deposition method, drying and calcination conditions for the ceria and Pt precursors were optimized experimentally. The activity was correlated with surface properties using CO/H2 chemisorption, O2-H2 titration, X-ray diffraction and BET surface area analysis. The method of CeO2 deposition had a significant impact on the catalytic activity. CeO2 deposition by impregnation resulted in a catalyst that was three times more active than that prepared by deposition precipitation or CeO2 grafting. O2-H2 titration results revealed that the close association of ceria and Pt in the case of CeO2 deposition by impregnation resulted in higher activity. The catalyst support used was also crucial as a silica supported catalyst was five times more active than an alumina supported catalyst. The particle size and pore structure of the catalyst support were also crucial as the reaction was diffusion controlled. The drying and calcination conditions of the ceria and Pt precursors also played a crucial role in determining the catalytic activity. The Pt-CeO2/SiO2 catalysts with Pt > 2.5 wt% and CeO2 > 15 wt% were highly active (TOF > 0.02 s-1) and stable (conversion ≥ 99% after 15 h) at ambient conditions.

Key words: Carbon monoxide oxidation, Catalyst, Platium, Ceria, Silica, Precursor, O2-H2 titration, Chemisorption, Temperature-programmed reduction