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首页> 外文期刊>Physical chemistry chemical physics: PCCP >In situ XAS and IR studies on Cu:SAPO-5 and Cu:SAPO-11: the contributory role of monomeric linear copper(I) species in the selective catalytic reduction of NO_x by propene
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In situ XAS and IR studies on Cu:SAPO-5 and Cu:SAPO-11: the contributory role of monomeric linear copper(I) species in the selective catalytic reduction of NO_x by propene

机译：Cu：SAPO-5和Cu：SAPO-11的原位XAS和IR研究：单体线性铜（I）物种在丙烯选择性催化还原NO_x中的作用

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Cu:SAPO-5 and Cu:SAPO-11 were prepared by conventional and hydrothermal ion exchange. Copper incorporation is increased six-fold by hydrothermal ion exchange relative to conventional methods. In all cases, the amount of copper taken up by SAPO-11 is superior to uptake in SAPO-5. Copper is divalent and in tetragonally-distorted octahedral environments in the as-prepared samples independent of the method of incorporation for both systems. The local structures about the metal and the valence states associated with the different steps in the selective catalytic reduction of NO_x in the presence of propene (SCR-HC) have been investigated using X-ray absorption spectroscopy (XAS). For both the Cu:SAPO-5 and Cu:SAPO-11 systems, heating in helium partially autoreduces copper(II) to copper(I). Following activation in oxygen, propene causes further reduction to copper(I) in all four samples as shown by the evolution of an intense pre-edge diagnostic feature. XANES analysis reveal this to be characteristic of monomeric linear two coordinate copper(I) species. This is a prime example of a pre-edge peak with such a high intensity being observed in the solid state. This is supported by IR where peaks attributed to bidentate copper were observed for Cu:SAPO-ll/HT. For all four samples NO_x partially reoxidises the copper(I) formed in the helium and propene steps. Ion exchanged Cu: SAPO-5 and Cu: SAPO-11 exhibit low activity in reducing NO_x by propene in an oxygen rich environment. The role of the copper ion during NO adsorption was studied using in situ infra red spectroscopy. The activity of copper exchanged materials is governed by both the degree of reducibility of copper(II) and the ease of reversing the valence states with the structural characteristics of the parent materials playing a crucial role.
机译：通过常规和水热离子交换制备Cu：SAPO-5和Cu：SAPO-11。相对于常规方法，通过水热离子交换，铜的结合增加了六倍。在所有情况下，SAPO-11吸收的铜量都优于SAPO-5的吸收量。铜是二价的，并且在制备的样品中呈四边形畸变的八面体环境，而与两种系统的掺入方法无关。使用X射线吸收光谱法（XAS）研究了在丙烯存在下选择性催化还原NO_x的金属的局部结构和与不同步骤相关的化合价（SCR-HC）。对于Cu：SAPO-5和Cu：SAPO-11系统，在氦气中加热都会部分自动将铜（II）还原为铜（I）。在氧气中活化后，丙烯会导致所有四个样品中的铜（I）进一步还原，这表现为强烈的边缘诊断特征。 XANES分析表明这是单体线性二配位铜（I）物种的特征。这是前边缘峰的主要示例，在固态下观察到如此高的强度。 IR支持了这一点，其中在Cu：SAPO-11 / HT中观察到归因于双齿铜的峰。对于所有四个样品，NO_x都会部分重新氧化在氦气和丙烯步骤中形成的铜（I）。离子交换的Cu：SAPO-5和Cu：SAPO-11在富氧环境中通过丙烯还原NO_x的活性较低。使用原位红外光谱研究了铜离子在NO吸附过程中的作用。铜交换材料的活性受铜（II）的还原度和化合价态容易程度的控制，母体材料的结构特征起着至关重要的作用。

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