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Formation and Reactions of NH4NO3 during Transient and Steady-State NH3-SCR of NOx over H-AFX Zeolites: Spectroscopic and Theoretical Studies
ACS Catalysis ( IF 11.3 ) Pub Date : 2020-01-29 , DOI: 10.1021/acscatal.9b05151 Hiroe Kubota 1 , Chong Liu 1 , Takashi Toyao 1, 2 , Zen Maeno 1 , Masaru Ogura 3 , Naoto Nakazawa 4 , Satoshi Inagaki 4 , Yoshihiro Kubota 4 , Ken-ichi Shimizu 1, 2
ACS Catalysis ( IF 11.3 ) Pub Date : 2020-01-29 , DOI: 10.1021/acscatal.9b05151 Hiroe Kubota 1 , Chong Liu 1 , Takashi Toyao 1, 2 , Zen Maeno 1 , Masaru Ogura 3 , Naoto Nakazawa 4 , Satoshi Inagaki 4 , Yoshihiro Kubota 4 , Ken-ichi Shimizu 1, 2
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Operando infrared (IR) spectroscopy and density functional theory (DFT) calculations were combined to investigate the selective catalytic reduction (SCR) of NOx by NH3 over H-AFX zeolites. The steady-state kinetics shows that SCR reactions involving NO2 proceed much more rapidly than those of NO. Data from in situ IR combined with online mass spectrometry under transient conditions demonstrate that Brønsted acid sites (BASs) promote the reaction of NO2 with NH3 to form N2, H2O, and NH4NO3 at low temperatures (50–150 °C). In combination with DFT results, these data suggest that NO promotes the reduction of NH4NO3 to NH4NO2, which then decomposes into N2 and H2O. Therefore, the accumulation of NH4NO3 in the zeolite is inhibited by NO. Furthermore, when NO is absent, NH4NO3 decomposition into N2O and H2O occurs only at high temperatures (>200 °C). A comparison of H-AFX and Cu-AFX implies that Cu sites are not active for the reduction of NO2 by NH3 and that BASs are responsible for the NH3-SCR reactions involving NO2.
中文翻译：
H-AFX分子筛上NO x的瞬态和稳态NH 3 -SCR期间NH 4 NO 3的形成和反应：光谱学和理论研究
Operando红外（IR）光谱和密度泛函理论（DFT）计算合并调查选择性催化还原（SCR）的NO X由NH 3在H-AFX沸石。稳态动力学表明，涉及NO 2的SCR反应比NO进行的快得多。瞬态条件下原位红外结合在线质谱的数据表明，布朗斯台德酸位（BASs）促进了NO 2与NH 3的反应形成N 2，H 2 O和NH 4 NO 3在低温（50–150°C）下。与DFT结果组合，这些数据表明，NO促进NH的还原4 NO 3至NH 4 NO 2，然后分解成Ñ 2和H 2 O.因此，NH的积聚4 NO 3在沸石是抑制否。此外，当NO为不存在，NH 4 NO 3分解成N 2 O和H ^ 2 O仅在高温（> 200℃）时发生。H-AFX和Cu-AFX的比较表明，铜位对于通过NH 3还原NO 2无效。BAS负责涉及NO 2的NH 3 -SCR反应。
更新日期：2020-01-29
中文翻译：
H-AFX分子筛上NO x的瞬态和稳态NH 3 -SCR期间NH 4 NO 3的形成和反应：光谱学和理论研究
Operando红外（IR）光谱和密度泛函理论（DFT）计算合并调查选择性催化还原（SCR）的NO X由NH 3在H-AFX沸石。稳态动力学表明，涉及NO 2的SCR反应比NO进行的快得多。瞬态条件下原位红外结合在线质谱的数据表明，布朗斯台德酸位（BASs）促进了NO 2与NH 3的反应形成N 2，H 2 O和NH 4 NO 3在低温（50–150°C）下。与DFT结果组合，这些数据表明，NO促进NH的还原4 NO 3至NH 4 NO 2，然后分解成Ñ 2和H 2 O.因此，NH的积聚4 NO 3在沸石是抑制否。此外，当NO为不存在，NH 4 NO 3分解成N 2 O和H ^ 2 O仅在高温（> 200℃）时发生。H-AFX和Cu-AFX的比较表明，铜位对于通过NH 3还原NO 2无效。BAS负责涉及NO 2的NH 3 -SCR反应。
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