Ruoxuan Bai, Rongkun Jiang, Zixiao Yu, Junqi Wang, Yiqing Zeng and Shule Zhang
{"title":"Temperature sensitive long-term stability of MnOx/TiO2 catalysts for selective catalytic reduction of NOx with NH3 at low temperature†","authors":"Ruoxuan Bai, Rongkun Jiang, Zixiao Yu, Junqi Wang, Yiqing Zeng and Shule Zhang","doi":"10.1039/D5NJ01932J","DOIUrl":null,"url":null,"abstract":"<p >A number of efforts have been made to improve the NH<small><sub>3</sub></small>-SCR activity of MnO<small><sub><em>x</em></sub></small> based catalysts at low temperature, but few studies have focused on their long-term stability. In this study, MnO<small><sub><em>x</em></sub></small>/TiO<small><sub>2</sub></small> (MnTi) catalysts prepared <em>via</em> wet impregnation were subjected to 30-h long-term stability tests under laboratory conditions to investigate their stability for the selective catalytic reduction (NH<small><sub>3</sub></small>-SCR) of NO<small><sub><em>x</em></sub></small> at low temperatures (80–200 °C), and combined with XRD, BET, XPS, H<small><sub>2</sub></small>-TPR, and <em>in situ</em> DRIFTS analysis to elucidate deactivation mechanisms. The results show that the reaction temperature has a great influence on the formation, decomposition, and transformation of nitrate species. Nitrate species, especially stable nitrate species, continuously accumulate on the catalyst surface at relatively low temperatures (≤160 °C in this work), which might block the active sites and hinder the conversion of Mn<small><sup>3+</sup></small> to Mn<small><sup>4+</sup></small>, thereby leading to deactivation of the MnTi catalyst. In contrast, nitrate species on the catalyst surface can react or decompose rapidly at a high enough temperature (≥200 °C in this work), which facilitates the exposure of active sites and dynamic equilibrium of the Mn<small><sup>4+</sup></small>/Mn<small><sup>3+</sup></small> redox cycle, resulting in the high long-term stability. We expect that this work will arouse researchers’ attention toward the long-term stability of NH<small><sub>3</sub></small>-SCR catalysts in the study of improving their catalytic activity at low temperature.</p>","PeriodicalId":95,"journal":{"name":"New Journal of Chemistry","volume":" 29","pages":" 12875-12883"},"PeriodicalIF":2.5000,"publicationDate":"2025-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"New Journal of Chemistry","FirstCategoryId":"92","ListUrlMain":"https://pubs.rsc.org/en/content/articlelanding/2025/nj/d5nj01932j","RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"CHEMISTRY, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
Abstract
A number of efforts have been made to improve the NH3-SCR activity of MnOx based catalysts at low temperature, but few studies have focused on their long-term stability. In this study, MnOx/TiO2 (MnTi) catalysts prepared via wet impregnation were subjected to 30-h long-term stability tests under laboratory conditions to investigate their stability for the selective catalytic reduction (NH3-SCR) of NOx at low temperatures (80–200 °C), and combined with XRD, BET, XPS, H2-TPR, and in situ DRIFTS analysis to elucidate deactivation mechanisms. The results show that the reaction temperature has a great influence on the formation, decomposition, and transformation of nitrate species. Nitrate species, especially stable nitrate species, continuously accumulate on the catalyst surface at relatively low temperatures (≤160 °C in this work), which might block the active sites and hinder the conversion of Mn3+ to Mn4+, thereby leading to deactivation of the MnTi catalyst. In contrast, nitrate species on the catalyst surface can react or decompose rapidly at a high enough temperature (≥200 °C in this work), which facilitates the exposure of active sites and dynamic equilibrium of the Mn4+/Mn3+ redox cycle, resulting in the high long-term stability. We expect that this work will arouse researchers’ attention toward the long-term stability of NH3-SCR catalysts in the study of improving their catalytic activity at low temperature.