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首页> 外文期刊>RSC Advances >Catalytic oxidation of CO on metals involving an ionic process in the presence of H2O: the role of promoting materials
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Catalytic oxidation of CO on metals involving an ionic process in the presence of H2O: the role of promoting materials

机译：H2O存在下涉及离子过程的金属的催化氧化：促进材料的作用

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A new catalytic oxidation of CO involving an ionic process in the presence of H2O is proposed on a Pt-catalyst with specific promoting materials (co-catalysts). Oxidation of CO is very slow at room temperature on ordinary Pt-catalysts such as Pt/SiO2, Pt/Al2O3, Pt/TiO2, Pt/Graphite, and Pt/carbon nano-tube (CNT), and H-2 or H2O have no effect on the reaction. However, in the presence of specific co-catalysts, the oxidation of CO is markedly enhanced by H-2 or H2O, so that highly selective preferential oxidation (PROX) of CO in H-2 is attained. The role that co-catalysts play in the oxidation of CO enhanced by H-2 or H2O was clarified by the experiments with Pt supported on CNT and carbon nano-fiber (CNF) that had Ni-MgO and FeOx at their one terminal end, respectively. Oxidation of CO was markedly enhanced by H-2 on the Pt/CNT and Pt/CNF, but no enhancement was observed on the Pt/CNT-p and Pt/CNF-p, where the CNT-p and CNF-p were purified by removing Ni-MgO and FeOx. Similar enhancement of the oxidation of CO by H-2 or H2O was observed on FeOx/Pt/TiO2 and FeOx/Au/TiO2, although no enhancement was observed on the Pt/TiO2 and Au/TiO2 catalysts. The in situ DRIFT spectra of the FeOx/Pt/TiO2 catalyst (Fe : TiO2 : Pt - ca. 100 : 100 : 1) during reaction in a flow of (CO + O-2 + H-2) suggested the rate-determining slow step was HCOO(a) + OH(a) -> CO2 + H2O. The oxidation of CO enhanced by H2O/D2O and H-2/D-2 showed a common hydrogen isotope effect of r(H)/r(D) = 1.4-1.5. The highly selective oxidation of CO in H-2 on the Pt/CNT and Pt/CNF catalysts strongly suggests efficient transport of ionic intermediates from Ni-MgO or FeOx to Pt over the hydrophobic CNT and CNF surface according to the local potential gradient. According to this mechanism, selectivity in the preferential oxidation of CO in H-2 is defined by the turnover number of a H2O molecule forming CO2 during its residence time on the catalyst, which is essentially different from the selectivity based on competitive adsorption and/or reaction. The role of the H2O molecule is as a kind of messenger molecule or a molecular catalyst to promote the reaction on the surface expressed by the equation n(CO + 1/2O(2)) + H2O -> nCO(2) + H2O. In this mechanism, the selectivity is given by n/(n + 1). Curious phenomena previously observed in the PROX reaction of CO in H-2 on various catalysts are well explained by the mechanism including an ionic process proposed in this paper.
机译：在具有特异性促进材料（共催化剂）的PT催化剂上，提出了在H 2 O存在下涉及离子过程的CO的新催化氧化。在室温下CO的氧化在普通Pt催化剂上非常慢，例如Pt / SiO 2，Pt / Al 2 O 3，Pt / TiO 2，Pt /石墨和Pt /碳纳米管（CNT），H-2或H2O具有对反应没有影响。然而，在特定的助催化剂存在下，H-2或H 2 O明显增强CO的氧化，从而实现了H-2中的CO的高度选择性优先氧化（Prox）。通过在其一个终端的CNT和碳纳米纤维（CNF）上支持的CNT和碳纳米纤维（CNF）上的实验，阐明了催化剂在CO增强的CO氧化中发挥的作用。分别。在PT / CNT和PT / CNF上通过H-2显着增强了CO的氧化，但在PT / CNT-P和PT / CNF-P上没有观察到增强，其中CNT-P和CNF-P纯化通过去除Ni-MgO和Feox。在Feox / Pt / TiO 2和Feox / Au / TiO 2上观察到H-2或H 2 O的同样提高CO通过H-2或H 2 O，尽管在Pt / TiO 2和Au / TiO 2催化剂上没有观察到增强。在（CO + O-2 + H-2）的反应期间，Feox / Pt / TiO2催化剂（Fe：TiO2：Pt-Ca.100：100：100：100：100：100：100：100）的原位漂移光谱提出了速率确定慢步骤是HCOO（A）+ OH（A） - > CO2 + H2O。通过H 2 O / D2O和H-2 / D-2增强的CO氧化显示出R（H）/ R（D）= 1.4-1.5的常见氢同位素效应。在PT / CNT和PT / CNF催化剂上的H-2中的CO在H-2中的高度选择性氧化强烈地表明，根据局部电位梯度，在疏水CNT和CNF表面上，将离子中间体的离子中间体的有效转运到PT。根据该机制，H-2中CO中的优先氧化中的选择性由H2O分子形成CO 2的成交量数而定义在催化剂上的停留时间，其基本上不同于基于竞争性吸附和/或/或基于竞争性吸附的选择性反应。 H 2 O分子的作用是一种促进由等式N（CO + 1 / 2O（2））+ H 2 O - > NCO（2）+ H 2 O表示的表面上的反应的信使分子或分子催化剂。在该机制中，选择性由n /（n + 1）给出。在各种催化剂上在H-2上的CO的PRX反应中观察到的奇异现象是通过本文提出的离子过程的机制很好地解释了。

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  • 来源
    《RSC Advances》 |2015年第2期|共11页
  • 作者

    Tanaka Ken-Ichi; He Hong; Yuan Youzhu;

  • 作者单位

    Chinese Acad Sci Ecoenvironm Sci Res Ctr Beijing 100085 Peoples R China;

    Chinese Acad Sci Ecoenvironm Sci Res Ctr Beijing 100085 Peoples R China;

    Xiamen Univ Coll Chem &

    Chem Engn State Key Lab Phys Chem Solid Surfaces Xiamen 361005 Peoples R China;

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  • 正文语种 eng
  • 中图分类 化学;
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