Characterization of CeO2-supported Cu-Pd bimetallic catalyst for the oxygen-assisted water-gas shift reaction
Characterization of CeO2-supported Cu-Pd bimetallic catalyst for the oxygen-assisted water-gas shift reaction
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DOI：
10.1016/j.jcat.2008.08.018
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发表时间：
2008-12-10
影响因子：
7.3
通讯作者：
Song, Chunshan
中科院分区：
文献类型：
--
作者：
Fox, Elise B.;Velu, Subramani;Song, Chunshan
我们最近的工作表明，以尿素凝胶法制备的纳米CeO 2为载体的Cu-Pd/CeO 2催化剂对氧助水煤气变换反应是有效的。采用EXAFS、XRD、TPR、CO化学吸附和原位XPS等表征技术，研究了Cu和Pd在CuPd/CeO 2催化剂（含20- 30wt%Cu和0.5- 1wt%Pd）中的作用。在Pd/CeO 2单组分催化剂中添加Cu或Pd/Cu/CeO 2单组分催化剂，可提高CO转化的催化活性和催化剂的稳定性，特别是在低于200 ℃的低温下进行OWGS反应时。单金属Cu/CeO 2的TPR显示在两个不同的区域（大约150和250 ℃）中负载在CeO 2上的CuO被还原。在加入Pd后，高温峰消失，并且在约150 ° C的单步中发生还原。原位XPS研究表明，在Cu的2 p峰向较低的结合能（BE）的位移与随之而来的位移在Pd的3d峰向较高的BE。还原时发生Pd向内扩散到CeO 2载体中。另一方面，当I存在于样品中时，发生Cu的向内扩散。这些观察结果表明，在这些催化剂中存在的Cu和Pd之间的协同相互作用，这可能是负责提高催化剂的活性和稳定性的CuPd/CeO_2 TiO_2催化剂。铜的EXAFS分析表明，在铜边缘没有明显的Cu-Pd合金形成的证据。EXAFS结果表明，还原态CuPd/CeO_2催化剂中Pd的边缘为PdCu合金，Pd原子仅被Cu原子包围. (C)2008年爱思唯尔公司All rights reserved.
Our recent work demonstrated that Cu-Pd bimetallic catalyst supported on a nano-crystalline CeO2 synthesized by urea gelation method is effective for oxygen-assisted water-gas shift (OWGS) reaction. The present study focuses on the roles of Cu and Pd in CuPd/CeO2 bimetallic catalysts containing 20-30 wt% Cu and 0.5-1 wt% Pd used in the OWGS reaction employing a combined bulk and surface characterization techniques such as EXAFS, XRD, TPR, CO chemisorption, and in situ XPS. The catalytic activity for CO conversion and the stability of catalyst during on-stream operation increased by the addition of Cu to Pd/CeO2 or Pd to Cu/CeO2 monometallic catalysts, especially when the OWGS reaction was performed at low temperatures, below 200 degrees C. The TPR of monometallic Cu/CeO2 showed reduction of CuO supported on CeO2 in two distinct regions, around 150 and 250 degrees C. The high temperature peak disappeared and reduction occurred in a single step around 150 degrees C upon Pd addition. In situ XPS studies showed a shift in Cu 2p peaks toward lower binding energy (BE) with concomitant shift in the Pd 3d peaks toward higher BE. An inward diffusion of Pd into the CeO2 support occurred upon reduction. On the other hand, inward diffusion of Cu occurred when I'd was present in the sample. These observations indicated the existence of synergistic interactions between Cu and Pd in these catalysts which could be responsible for the improved catalytic activity and stability of CuPd/CeO2 bimetallic catalyst. The EXAFS analysis of Cu showed no clear evidence of Cu-Pd alloy formation at the copper edge. However, evidence for PdCu alloy was shown in the Pd edge, and Pd atoms are surrounded only by Cu atoms in the reduced CuPd/CeO2 bimetallic catalyst as revealed by EXAFS. (C) 2008 Elsevier Inc. All rights reserved.