Hyun Sub Kim , Hwangho Lee , Hongbeom Park , Inhak Song , Do Heui Kim
{"title":"了解用于低温 NH3-SCR 的氧化锰-沸石杂化催化剂上的布氏/路易斯酸位点的作用","authors":"Hyun Sub Kim , Hwangho Lee , Hongbeom Park , Inhak Song , Do Heui Kim","doi":"10.1016/S1872-2067(24)60112-9","DOIUrl":null,"url":null,"abstract":"<div><div>Although metal oxide-zeolite hybrid materials have long been known to achieve enhanced catalytic activity and selectivity in NO<sub><em>x</em></sub> removal reactions through the inter-particle diffusion of intermediate species, their subsequent reaction mechanism on acid sites is still unclear and requires investigation. In this study, the distribution of Brønsted/Lewis acid sites in the hybrid materials was precisely adjusted by introducing potassium ions, which not only selectively bind to Brønsted acid sites but also potentially affect the formation and diffusion of activated NO species. Systematic <em>in situ</em> diffuse reflectance infrared Fourier transform spectroscopy analyses coupled with selective catalytic reduction of NO<sub><em>x</em></sub> with NH<sub>3</sub> (NH<sub>3</sub>-SCR) reaction demonstrate that the Lewis acid sites over MnO<sub><em>x</em></sub> are more active for NO reduction but have lower selectivity to N<sub>2</sub> than Brønsted acids sites. Brønsted acid sites primarily produce N<sub>2</sub>, whereas Lewis acid sites primarily produce N<sub>2</sub>O, contributing to unfavorable N<sub>2</sub> selectivity. The Brønsted acid sites present in Y zeolite, which are stronger than those on MnO<sub><em>x</em></sub>, accelerate the NH<sub>3</sub>-SCR reaction in which the nitrite/nitrate species diffused from the MnO<sub><em>x</em></sub> particles rapidly convert into the N<sub>2</sub>. Therefore, it is important to design the catalyst so that the activated NO species formed in MnO<sub><em>x</em></sub> diffuse to and are selectively decomposed on the Brønsted acid sites of H-Y zeolite rather than that of MnO<sub><em>x</em></sub> particle. For the physically mixed H-MnO<sub><em>x</em></sub>+H-Y sample, the abundant Brønsted/Lewis acid sites in H-MnO<sub><em>x</em></sub> give rise to significant consumption of activated NO species before their inter-particle diffusion, thereby hindering the enhancement of the synergistic effects. Furthermore, we found that the intercalated K<sup>+</sup> in K-MnO<sub><em>x</em></sub> has an unexpected favorable role in the NO reduction rate, probably owing to faster diffusion of the activated NO species on K-MnO<sub><em>x</em></sub> than H-MnO<sub><em>x</em></sub>. This study will help to design promising metal oxide-zeolite hybrid catalysts by identifying the role of the acid sites in two different constituents.</div></div>","PeriodicalId":9832,"journal":{"name":"Chinese Journal of Catalysis","volume":"65 ","pages":"Pages 79-88"},"PeriodicalIF":15.7000,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Understanding the roles of Brønsted/Lewis acid sites on manganese oxide-zeolite hybrid catalysts for low-temperature NH3-SCR\",\"authors\":\"Hyun Sub Kim , Hwangho Lee , Hongbeom Park , Inhak Song , Do Heui Kim\",\"doi\":\"10.1016/S1872-2067(24)60112-9\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><div>Although metal oxide-zeolite hybrid materials have long been known to achieve enhanced catalytic activity and selectivity in NO<sub><em>x</em></sub> removal reactions through the inter-particle diffusion of intermediate species, their subsequent reaction mechanism on acid sites is still unclear and requires investigation. In this study, the distribution of Brønsted/Lewis acid sites in the hybrid materials was precisely adjusted by introducing potassium ions, which not only selectively bind to Brønsted acid sites but also potentially affect the formation and diffusion of activated NO species. Systematic <em>in situ</em> diffuse reflectance infrared Fourier transform spectroscopy analyses coupled with selective catalytic reduction of NO<sub><em>x</em></sub> with NH<sub>3</sub> (NH<sub>3</sub>-SCR) reaction demonstrate that the Lewis acid sites over MnO<sub><em>x</em></sub> are more active for NO reduction but have lower selectivity to N<sub>2</sub> than Brønsted acids sites. Brønsted acid sites primarily produce N<sub>2</sub>, whereas Lewis acid sites primarily produce N<sub>2</sub>O, contributing to unfavorable N<sub>2</sub> selectivity. The Brønsted acid sites present in Y zeolite, which are stronger than those on MnO<sub><em>x</em></sub>, accelerate the NH<sub>3</sub>-SCR reaction in which the nitrite/nitrate species diffused from the MnO<sub><em>x</em></sub> particles rapidly convert into the N<sub>2</sub>. Therefore, it is important to design the catalyst so that the activated NO species formed in MnO<sub><em>x</em></sub> diffuse to and are selectively decomposed on the Brønsted acid sites of H-Y zeolite rather than that of MnO<sub><em>x</em></sub> particle. For the physically mixed H-MnO<sub><em>x</em></sub>+H-Y sample, the abundant Brønsted/Lewis acid sites in H-MnO<sub><em>x</em></sub> give rise to significant consumption of activated NO species before their inter-particle diffusion, thereby hindering the enhancement of the synergistic effects. Furthermore, we found that the intercalated K<sup>+</sup> in K-MnO<sub><em>x</em></sub> has an unexpected favorable role in the NO reduction rate, probably owing to faster diffusion of the activated NO species on K-MnO<sub><em>x</em></sub> than H-MnO<sub><em>x</em></sub>. This study will help to design promising metal oxide-zeolite hybrid catalysts by identifying the role of the acid sites in two different constituents.</div></div>\",\"PeriodicalId\":9832,\"journal\":{\"name\":\"Chinese Journal of Catalysis\",\"volume\":\"65 \",\"pages\":\"Pages 79-88\"},\"PeriodicalIF\":15.7000,\"publicationDate\":\"2024-10-01\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Chinese Journal of Catalysis\",\"FirstCategoryId\":\"92\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/S1872206724601129\",\"RegionNum\":1,\"RegionCategory\":\"化学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q1\",\"JCRName\":\"CHEMISTRY, APPLIED\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Chinese Journal of Catalysis","FirstCategoryId":"92","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S1872206724601129","RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"CHEMISTRY, APPLIED","Score":null,"Total":0}
Understanding the roles of Brønsted/Lewis acid sites on manganese oxide-zeolite hybrid catalysts for low-temperature NH3-SCR
Although metal oxide-zeolite hybrid materials have long been known to achieve enhanced catalytic activity and selectivity in NOx removal reactions through the inter-particle diffusion of intermediate species, their subsequent reaction mechanism on acid sites is still unclear and requires investigation. In this study, the distribution of Brønsted/Lewis acid sites in the hybrid materials was precisely adjusted by introducing potassium ions, which not only selectively bind to Brønsted acid sites but also potentially affect the formation and diffusion of activated NO species. Systematic in situ diffuse reflectance infrared Fourier transform spectroscopy analyses coupled with selective catalytic reduction of NOx with NH3 (NH3-SCR) reaction demonstrate that the Lewis acid sites over MnOx are more active for NO reduction but have lower selectivity to N2 than Brønsted acids sites. Brønsted acid sites primarily produce N2, whereas Lewis acid sites primarily produce N2O, contributing to unfavorable N2 selectivity. The Brønsted acid sites present in Y zeolite, which are stronger than those on MnOx, accelerate the NH3-SCR reaction in which the nitrite/nitrate species diffused from the MnOx particles rapidly convert into the N2. Therefore, it is important to design the catalyst so that the activated NO species formed in MnOx diffuse to and are selectively decomposed on the Brønsted acid sites of H-Y zeolite rather than that of MnOx particle. For the physically mixed H-MnOx+H-Y sample, the abundant Brønsted/Lewis acid sites in H-MnOx give rise to significant consumption of activated NO species before their inter-particle diffusion, thereby hindering the enhancement of the synergistic effects. Furthermore, we found that the intercalated K+ in K-MnOx has an unexpected favorable role in the NO reduction rate, probably owing to faster diffusion of the activated NO species on K-MnOx than H-MnOx. This study will help to design promising metal oxide-zeolite hybrid catalysts by identifying the role of the acid sites in two different constituents.
期刊介绍:
The journal covers a broad scope, encompassing new trends in catalysis for applications in energy production, environmental protection, and the preparation of materials, petroleum chemicals, and fine chemicals. It explores the scientific foundation for preparing and activating catalysts of commercial interest, emphasizing representative models.The focus includes spectroscopic methods for structural characterization, especially in situ techniques, as well as new theoretical methods with practical impact in catalysis and catalytic reactions.The journal delves into the relationship between homogeneous and heterogeneous catalysis and includes theoretical studies on the structure and reactivity of catalysts.Additionally, contributions on photocatalysis, biocatalysis, surface science, and catalysis-related chemical kinetics are welcomed.