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Selective catalytic reduction

About: Selective catalytic reduction is a research topic. Over the lifetime, 10502 publications have been published within this topic receiving 226291 citations.


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Journal ArticleDOI
TL;DR: In this paper, the location of copper cations in the zeolite pores and the effect of temperature on these sites and on framework stability were investigated using Rietveld refinement of variable-temperature XRD synchrotron data.
Abstract: Nitrogen oxides (NOx) are a major atmospheric pollutant produced through the combustion of fossil fuels in internal combustion engines. Copper-exchanged zeolites are promising as selective catalytic reduction catalysts for the direct conversion of NO into N2 and O2, and recent reports have shown the enhanced performance of Cu-CHA catalysts over other zeolite frameworks in the NO decomposition of exhaust gas streams. In the present study, Rietveld refinement of variable-temperature XRD synchrotron data obtained for Cu-SSZ-13 and Cu-SSZ-16 is used to investigate the location of copper cations in the zeolite pores and the effect of temperature on these sites and on framework stability. The XRD patterns show that the thermal stability of SSZ-13 is increased significantly when copper is exchanged into the framework compared with the acid form of the zeolite, H-SSZ-13. Cu-SSZ-13 is also more thermally stable than Cu-SSZ-16. From the refined diffraction patterns, the atomic positions of atoms, copper locations a...

369 citations

Journal ArticleDOI
TL;DR: In this article, a series of MoO3-doped CeO2/TiO2 catalysts were investigated for the selective catalytic reduction of NO,c by NH3(NH3-SCR).
Abstract: A series of MoO3-doped CeO2/TiO2 catalysts prepared by the impregnation method were investigated for the selective catalytic reduction of NO,c by NH3(NH3-SCR). It was found that CeO2-MoO3/TiO2 catalyst is much more active than CeO2/TiO2 for NH3-SCR and the optimum MoO3 loading is 5%. The mechanistic cause of the promoting effect of MoO3 on the activity of CeO2/TiO2 catalyst for NH3-SCR was studied using in situ diffuse reflectance infrared transform spectroscopy (DRIFTS). The results revealed that the highly dispersed molybdenum on CeO2-MoO3/TiO2 catalyst not only resulted in more Brensted acid sites formed on the catalyst surface, but also reduced the thermal stability of the inactive nitrate specie, leaving more active sites available for the adsorption of NH3, both of which are favorable for the promotion of SCR activity. (C) 2013 Elsevier B.V. All rights reserved.

368 citations

Journal ArticleDOI
TL;DR: In this article, the effects of SO2 poisoning on the selective catalytic reduction of NO by NH3 over a Ce/TiO2 catalyst were studied and the analytical results indicate that there was no obvious change in the crystal structure of the different samples; however, the specific area decreased with SO 2 poisoning time, and sulfates were formed and preferentially diffused from the surface to a bulk phase during the poisoning process.
Abstract: The effects of SO2 on the selective catalytic reduction of NO by NH3 over a Ce/TiO2 catalyst were studied. Conversion of NO remained above 90% in the presence of 100 ppm SO2 at 350 °C for 48 h. However, when 180 ppm SO2 was added at 300 °C, NO conversion only remained above 90% during the first 12 h and then gradually decreased with time. Characterizations of fresh and SO2-poisoned Ce/TiO2 catalysts were carried out using Brunauer−Emmett−Teller method, ion chromatography, X-ray photoelectron spectroscopy, and X-ray diffraction. The analytical results indicate that there was no obvious change in the crystal structure of the different samples; however, the specific area decreased with SO2 poisoning time. Sulfates were formed and preferentially diffused from the surface to a bulk phase during the poisoning process. Temperature-programmed desorption and diffuse reflectance infrared Fourier-transform spectroscopy results show that in the presence of O2, SO2 could react with NH3 to form NH4HSO4, which is deposi...

367 citations

Journal ArticleDOI
TL;DR: Diffuse reflectance infrared Fourier transform spectroscopy studies showed that the synergetic effect between Mn and Ce contributes to the formation of reactive intermediate species, thus promoting the NH3-SCR to proceed.
Abstract: Mn-Ce-Ti mixed-oxide catalyst prepared by the hydrothermal method was investigated for the selective catalytic reduction (SCR) of NOx with NH3 in the presence of oxygen. It was found that the environmentally benign Mn-Ce-Ti catalyst exhibited excellent NH3-SCR activity and strong resistance against H2O and SO2 with a broad operation temperature window, which is very competitive for the practical application in controlling the NOx emission from diesel engines. On the basis of the catalyst characterization, the dual redox cycles (Mn4+ + Ce3+ Mn3+ + Ce4+, Mn4+ + Ti3+ Mn3+ + Ti4+) and the amorphous structure play key roles for the high catalytic deNO(x) performance. Diffuse reflectance infrared Fourier transform spectroscopy studies showed that the synergetic effect between Mn and Ce contributes to the formation of reactive intermediate species, thus promoting the NH3-SCR to proceed.

362 citations

Patent
Kenichi Tsujimoto1, Shinya Hirota1
25 Feb 2008
TL;DR: In this article, an internal combustion engine with an HC treatment catalyst having the function of adsorbing the HC in the exhaust gas is arranged upstream of the NOx selective reducing catalyst.
Abstract: An internal combustion engine wherein an HC treatment catalyst (12) having the function of adsorbing the HC in the exhaust gas is arranged upstream of the NOx selective reducing catalyst (14), an urea aqueous solution fed from the reducing agent feed valve (15) is arranged upstream of the HC treatment catalyst (12), urea, and NOx contained in the exhaust gas, and HC adsorbed on the HC treatment catalyst 12 are reacted with each other to form intermediate products having cyano groups, oximes, and amino groups, and these intermediate products are sent to the NOx selective reducing catalyst (14).

361 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023311
2022632
2021546
2020583
2019604
2018595