Selective Catalytic Reduction of N 2 O by CO over Fe-Beta Zeolites Catalysts: Influence of Iron Species Distribution
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ORIGINAL ARTICLE
Selective Catalytic Reduction of N2O by CO over Fe‑Beta Zeolites Catalysts: Influence of Iron Species Distribution Jie Zeng1 · Yazhou Wang1 · Fan Diao1 · Lei Qiu1 · Huazhen Chang1 Received: 30 June 2020 / Accepted: 30 August 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract In this paper, selective catalytic reduction (SCR) of N2O by CO was investigated over Fe-beta zeolites catalysts. The catalysts were prepared by wet ion-exchange (IE), impregnation (IM) and solid state ion-exchange (SSIE) methods. These catalysts were characterized by XRD, UV–vis DR spectroscopy, H2-TPR, TPD and in-situ DRIFTS. At 350 °C, more than 90% N2O conversion could be obtained over the Fe-beta-IE catalyst. The activity for N 2O removal of Fe-beta-IE was higher than Fe-beta-IM and Fe-beta-SSIE catalysts. The UV–vis spectra showed that 84.2% of isolated Fe(III) ion appeared on Fe-betaIE catalyst. It indicated that the isolated F e(III) ions might be considered as the active sites for N 2O reduction. Besides, in the presence of H2O, the activities in CO-SCR for N2O removal over Fe-beta catalysts were inhibited, which might be due to the hydroxylation deactivation of iron species and excess accumulation of carbonates. Graphic Abstract
Keywords Nitrous oxide · CO-SCR · Iron species · Preparation methods · Effect of H2O
1 Introduction
* Huazhen Chang [email protected] 1
School of Environment and Natural Resources, Renmin University of China, Beijing 100872, China
Nitrous oxide (N2O) could destroy the ozone layer and exacerbate global warming [1, 2]. Many departments, such as agriculture, transportation and industry, face the great challenge for the control of N2O emission [3]. It was worthy noted that a third of N 2O emission in the chemical industry was generated from adipic acid and nitric acid plants [4, 5].
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Thermal decomposition, catalytic decomposition and selective catalytic reduction (SCR) technologies are often used for N2O elimination [6, 7]. Generally, N2O catalytic decomposition is an economical and efficient technology because no reducing agents are required. For N2O decomposition, it started with the dissociation of N 2O [Step (1)] [8], followed by the recombination and desorption of O2 [Step (2) or (3)]. This reaction could be described as follows [9, 10]:
N2 O → N2 + O∗
(1)
Eley−Rideal (E−R) mechanism∶ N2 O + O∗ → N2 + O2 + ∗ (2) Langmuir−Hinshelwood (L−H) mechanism∶ O∗ + O∗ → O2 + 2∗
(3)
where * shows an active site of catalysts. However, the conversion of N2O decomposition was difficult to improve, due to the limit of reaction temperature. The presence of reductants could accelerate the removal of O* in active sites of the catalysts, leading to the decrease of operation temperature. Therefore, catalytic reduction technologies (e.g. NH3-SCR, CO-SCR and HC-SCR) are widely investigated for the low-temperature removal of N2O [11–13]. Delahay et al. [14] found that CO was the most efficient reductant
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