Role of cerium in promoting the stability of CuHM catalyst against HCl to reduce NO with NH3
Role of cerium in promoting the stability of CuHM catalyst against HCl to reduce NO with NH3
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DOI：
10.1016/j.apcata.2006.06.044
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发表时间：
2006-09
影响因子：
5.5
通讯作者：
J. Choung;I. Nam
中科院分区：
文献类型：
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作者：
J. Choung;I. Nam
为了提高在NH3-SCR反应条件下当HCl存在于进料气流（主要来自废物焚烧炉）中时铜离子交换的丝光沸石（CuHM）催化剂的耐氯性，将第二金属，特别是铈，与Cu一起沿着另外交换到催化剂上。它防止Cu（II）离子通过HCl从催化剂表面蒸发，并显著改善催化剂失活。在450°C的反应温度下已经观察到来自CeCuHM催化剂的铜损失，而来自不含Ce的CuHM催化剂的铜损失在350°C开始。Ce简单地稳定催化剂表面上的Cu（II）离子，该催化剂表面通常被认为是本发明反应体系的活性反应位点。采用X射线吸收近边光谱（XANES）、扩展X射线吸收精细结构（EXAFS）、同步辐射X射线衍射（SR-XRD）和X射线光电子能谱（XPS）等方法研究了Ce对CuHM催化剂上Cu（II）离子的稳定作用。SR-XRD结果表明，在催化剂失活过程中，CeCuHM催化剂的晶胞参数变化小于未添加Ce的CuHM催化剂。类似地，如通过XPS所鉴定的，CeCuHM催化剂表面上的Cu（II）较少转化为Cu（I）离子。Ce离子和Ce-Cl化合物在催化剂表面的形成降低了催化剂的平均电负性，增加了分子筛骨架中晶格氧的电荷，从而提高了催化体系中Cu-O键的稳定性。
To enhance the chlorine tolerance of copper ion exchanged mordenite (CuHM) catalyst under NH3-SCR reaction condition when HCl exists in the feed gas stream, mainly from a waste incinerator, a second metal, particularly cerium, has been additionally exchanged onto the catalyst along with Cu. It prevents Cu(II) ion from being evaporated from the catalyst surface by HCl and significantly improves the catalyst deactivation. The loss of copper from CeCuHM catalyst has been observed at a reaction temperature of 450°C, while that from CuHM catalyst without Ce begins at 350°C. Ce simply stabilizes Cu(II) ion on the catalyst surface, generally recognized as an active reaction site for the present reaction system. X-ray absorption near edge spectroscopy (XANES), extended X-ray absorption fine structure (EXAFS), synchrotron radiation X-ray diffraction (SR-XRD), and X-ray photoelectron spectroscopy (XPS) have been employed to identify the stabilization of Cu(II) ion on CuHM catalyst by Ce. As confirmed by SR-XRD, the lattice parameters of the unit cell of CeCuHM catalyst are less altered than those of CuHM catalyst without Ce during the course of the catalyst deactivation. Similarly, as identified by XPS, Cu(II) on the surface of CeCuHM catalyst is less transformed to Cu(I) ions. Ce ions and Ce–Cl compounds formed on the catalyst surface may decrease the average electronegativity of the catalyst and increase the charge of the lattice oxygen in the zeolite framework, resulting in an enhancement of the stability of the Cu–O bond in the present catalytic system.