Spectroscopic identification and catalytic relevance of NH4+ intermediates in selective NOx reduction over Cu-SSZ-13 zeolites
Spectroscopic identification and catalytic relevance of NH4+ intermediates in selective NOx reduction over Cu-SSZ-13 zeolites
复制标题
Cu-SSZ-13 沸石选择性 NOx 还原中 NH4 中间体的光谱鉴定和催化相关性
DOI：
10.1016/j.chemosphere.2020.126272
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发表时间：
2020-07-01
期刊：
影响因子：
8.8
通讯作者：
Chen, Peirong
中科院分区：
文献类型：
--
作者：
Rizzotto, Valentina;Chen, Dongdong;Chen, Peirong
柴油机尾气中有害氮氧化物（NOx）的还原是环境保护的关键挑战之一，采用铜交换菱沸石（即Cu-CHA，包括Cu-SSZ-13和Cu-SAPO-34）作为催化剂，通过NH3辅助选择性催化还原（NH3-SCR）可以实现NOx的还原。了解Cu-CHA在NH3-SCR催化中的氧化还原化学对于进一步提高NOx还原效率至关重要。本文制备了一系列具有不同Cu离子交换水平的Cu-SSZ-13催化剂，通过X射线衍射、漫反射紫外-可见光谱和以NH3为探针分子的程序升温脱附等技术对其进行了全面表征，并在稳态条件下的NH3-SCR反应中进行测试。原位研究漫反射红外傅里叶变换光谱（DRIFTS），补充与densityfunctional理论计算，提供了坚实的证据，形成铵离子（NH 4+）的中间体产生的还原铜+由共吸附的NH3和NO分子CuSSZ-13。NH 4（+）中间体的催化相关性，如通过在NH3/NO气氛中预处理的Cu-SSZ-13上NO转化率的增加所证明的，可以归因于促进Cu-再氧化的紧密耦合的Cu+/NH 4（-）对的形成，并且因此促进整个NH3-SCR过程。该研究为提高Cu-CHA分子筛催化剂的NH3-SCR效率开辟了一条新的途径。(C)2020爱思唯尔有限公司保留所有权利。
Reduction of harmful nitrogen oxides (NOx) from diesel engine exhausts is one of the key challenges in environmental protection, and can be achieved by NH3-assisted selective catalytic reduction (NH3-SCR) using copper-exchanged chabazite zeolites (i.e. Cu-CHA, including Cu-SSZ-13 and Cu-SAPO-34) as catalysts. Understanding the redox chemistry of Cu-CHA in NH3-SCR catalysis is crucial for further improving the NOx reduction efficiency. Here, a series of Cu-SSZ-13 catalysts with different Cu ion exchange levels were prepared, thoroughly characterized by different techniques such as X-ray diffraction, diffuse reflectance ultraviolet-visible spectroscopy and temperature-programmed desorption using NH3 as a probe molecule, etc., and tested in NH3-SCR reactions under steady-state conditions. In situ studies by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), supplemented with densityfunctional theory calculations, provided solid evidence for the formation of ammonium ion (NH4+) intermediates resulting from the reduction of Cu2+ to Cu+ by co-adsorbed NH3 and NO molecules on CuSSZ-13. Catalytic relevance of the NH4(+) intermediates, as demonstrated by an increase of NO conversion over Cu-SSZ-13 pre-treated in NH3/NO atmosphere, can be attributed to the formation of closely coupled Cu+/NH4(-) pairs promoting the Cu- re-oxidation and, consequently, the overall NH3-SCR process. This study thus paves a new route for improving the NH3-SCR efficiency over Cu-CHA zeolite catalyst. (C) 2020 Elsevier Ltd. All rights reserved.