scholarly journals Modified Layered Silicas as Catalysts for Conversion of Nitrogen Pollutants in Flue Gases—A Review

Catalysts ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 644
Author(s):  
Lucjan Chmielarz ◽  
Roman Dziembaj
Keyword(s):  
Catalytic Reduction ◽  
Surface Acidity ◽  
Flue Gases ◽  
Catalytic Materials ◽  
Nh3 Scr ◽  
Selective Catalytic Oxidation ◽  
Reduction Of Nox ◽  
Layered Clay ◽  
Nitrogen Pollutants ◽  
Mesoporous Structures

This paper is focused on the recent achievements in the studies of modified layered zeolites and cationic layered clay minerals. These materials are very promising catalysts in green chemistry processes, such as selective catalytic reduction of NOx with ammonia (NH3-SCR) and selective catalytic oxidation of ammonia to dinitrogen (NH3-SCO). Special attention is paid to the roles of the micro- and mesoporous structures of the catalytic materials, the type and location of deposited transition metals, as well as surface acidity in the design of effective catalysts for the NH3-SCR and NH3-SCO processes. The majority of the presented analysis is based on the authors’ research.

scholarly journals Ferrierite and Its Delaminated Forms Modified with Copper as Effective Catalysts for NH3-SCO Process

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4885
Author(s):  
Aneta Święs ◽  
Małgorzata Rutkowska ◽  
Andrzej Kowalczyk ◽  
Urbano Díaz ◽  
Antonio E. Palomares ◽  
...  
Keyword(s):  
Copper Oxide ◽  
Ammonia Oxidation ◽  
Catalytic Reduction ◽  
Surface Acidity ◽  
Selective Reduction ◽  
Exchange Method ◽  
Copper Species ◽  
Selective Catalytic Oxidation ◽  
Catalytically Active ◽  
Copper Cations

Ferrierites and their delaminated forms (ITQ-6), containing aluminum or titanium in the zeolite framework, were synthetized and modified with copper by an ion-exchange method. The obtained samples were characterized with respect to their chemical composition (ICP-OES), structure (XRD, UV-Vis DRS), textural parameters (N2-sorption), surface acidity (NH3-TPD), form and reducibility of deposited copper species (UV-Vis DRS and H2-TPR). Ferrierites and delaminated ITQ-6 zeolites modified with copper were studied as catalysts for the selective catalytic oxidation of ammonia to dinitrogen (NH3-SCO). It was shown that aggregated copper oxide species, which were preferentially formed on Ti-zeolites, were catalytically active in direct low-temperature ammonia oxidation to NO, while copper introduced into Al-zeolites was present mainly in the form of monomeric copper cations catalytically active in selective reduction of NO by ammonia to dinitrogen. It was postulated that ammonia oxidation in the presence of the studied catalysts proceeds according to the internal-selective catalytic reduction mechanism (i-SCR) and therefore the suitable ratio between aggregated copper oxide species and monomeric copper cations is necessary to obtain active and selective catalysts for the NH3-SCO process. Cu/Al-ITQ-6 presented the best catalytic properties possibly due to the most optimal ratio of these copper species.

scholarly journals Catalytic Activity Of Cu/η-Al2O3 Catalysts Prepared From Aluminum Scraps In The NH3-SCO and in the NH3-SCR of NO

2021 ◽  
Author(s):  
Nawel Jr ◽  
Thabet Makhlouf ◽  
Gerard Delahay ◽  
Hassib Tounsi
Keyword(s):  
Catalytic Oxidation ◽  
Catalytic Reduction ◽  
Impregnation Method ◽  
Wet Impregnation ◽  
Reduction Of No ◽  
Evaporation Method ◽  
Nh3 Scr ◽  
Scr Of No ◽  
Selective Catalytic Oxidation ◽  
Wet Impregnation Method

Abstract Copper loaded η-alumina catalysts with different copper contents have been prepared by impregnation/evaporation method. The catalysts were characterized by XRD, FTIR, BET, UV–vis, H2-TPR and evaluated in the selective catalytic reduction of NO by NH3 and in the selective catalytic oxidation of NH3. The characterization techniques showed that the impregnation/evaporation method permits to obtain highly dispersed copper oxide species on the η-alumina surface when low amount of copper is used (1wt. % and 2 wt.%). The wet impregnation method made it possible to reach a well dispersion of the copper species on the surface of the alumina for the low copper contents Cu(1)-Al2O3 and Cu(2)-Al2O3. The latter justifies the similar behavior of Cu(1)-Al2O3) and Cu(2)-Al2O3 in the selective catalytic oxidation of NH3 where these catalysts exhibit a conversion of NH3 to N2 of the order of 100% at T > 500°C.

scholarly journals In Situ DRIFTS Studies of NH3-SCR Mechanism over V2O5-CeO2/TiO2-ZrO2 Catalysts for Selective Catalytic Reduction of NOx

Materials ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 1307 ◽  
Author(s):  
Yaping Zhang ◽  
Xiupeng Yue ◽  
Tianjiao Huang ◽  
Kai Shen ◽  
Bin Lu
Keyword(s):  
Selective Catalytic Reduction ◽  
Catalytic Reduction ◽  
Nox Reduction ◽  
Oxygen Storage ◽  
In Situ Drifts ◽  
Nh3 Scr ◽  
Nh3 Adsorption ◽  
Reduction Of Nox ◽  
Zro2 Catalyst

TiO2-ZrO2 (Ti-Zr) carrier was prepared by a co-precipitation method and 1 wt. % V2O5 and 0.2 CeO2 (the Mole ratio of Ce to Ti-Zr) was impregnated to obtain the V2O5-CeO2/TiO2-ZrO2 catalyst for the selective catalytic reduction of NOx by NH3. The transient activity tests and the in situ DRIFTS (diffuse reflectance infrared Fourier transform spectroscopy) analyses were employed to explore the NH3-SCR (selective catalytic reduction) mechanism systematically, and by designing various conditions of single or mixing feeding gas and pre-treatment ways, a possible pathway of NOx reduction was proposed. It was found that NH3 exhibited a competitive advantage over NO in its adsorption on the catalyst surface, and could form an active intermediate substance of -NH2. More acid sites and intermediate reaction species (-NH2), at lower temperatures, significantly promoted the SCR activity of the V2O5-0.2CeO2/TiO2-ZrO2 catalyst. The presence of O2 could promote the conversion of NO to NO2, while NO2 was easier to reduce. The co-existence of NH3 and O2 resulted in the NH3 adsorption strength being lower, as compared to tests without O2, since O2 could occupy a part of the active site. Due to CeO2’s excellent oxygen storage-release capacity, NH3 adsorption was weakened, in comparison to the 1 wt. % V2O5-0.2CeO2/TiO2-ZrO2 catalyst. If NOx were to be pre-adsorbed in the catalyst, the formation of nitrate and nitro species would be difficult to desorb, which would greatly hinder the SCR reaction. All the findings concluded that NH3-SCR worked mainly through the Eley-Rideal (E-R) mechanism.

A novel Ce–Sb binary oxide catalyst for the selective catalytic reduction of NOx with NH3

2016 ◽  
Vol 6 (22) ◽  
pp. 8063-8071 ◽  
Author(s):  
Zhiming Liu ◽  
Haiyan Liu ◽  
Hui Zeng ◽  
Qi Xu
Keyword(s):  
Selective Catalytic Reduction ◽  
Oxide Catalyst ◽  
Catalytic Reduction ◽  
Surface Acidity ◽  
Synergetic Effect ◽  
Binary Oxide ◽  
Redox Property ◽  
Reduction Of Nox

The synergetic effect between Sb and Ce not only increases the surface acidity of the catalyst but also enhances the redox property, both of which contribute to improving NH3-SCR activity.

scholarly journals Preparation and Performance of Cerium-Based Catalysts for Selective Catalytic Reduction of Nitrogen Oxides: A Critical Review

Catalysts ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 361
Author(s):  
Ming Cai ◽  
Xue Bian ◽  
Feng Xie ◽  
Wenyuan Wu ◽  
Peng Cen
Keyword(s):  
Nitrogen Oxides ◽  
Selective Catalytic Reduction ◽  
Catalytic Reduction ◽  
Surface Acidity ◽  
Catalytic Performance ◽  
Synthesis Methods ◽  
Preparation Methods ◽  
Nh3 Scr ◽  
Nox Control ◽  
And Performance

Selective catalytic reduction of nitrogen oxides with NH3 (NH3-SCR) is still the most commonly used control technology for nitrogen oxides emission. Specifically, the application of rare earth materials has become more and more extensive. CeO2 was widely developed in NH3-SCR reaction due to its good redox performance, proper surface acidity and abundant resource reserves. Therefore, a large number of papers in the literature have described the research of cerium-based catalysts. This review critically summarized the development of the different components of cerium-based catalysts, and characterized the preparation methods, the catalytic performance and reaction mechanisms of the cerium-based catalysts for NH3-SCR. The purpose of this review is to highlight: (1) the modification effect of the various metal elements for cerium-based catalysts; (2) various synthesis methods of the cerium-based catalysts; and (3) the physicochemical properties of the various catalysts and clarify their relations to catalytic performances, particularly in the presence of SO2 and H2O. Finally, we hope that this work can give timely technical guidance and valuable insights for the applications of NH3-SCR in the field of NOx control.

Application of ReOx/TiO2 Catalysts with an excellent SO2 tolerance in selective catalytic reduction of NOx by NH3

2021 ◽  
Author(s):  
Yanke Yu ◽  
Xianfang Yi ◽  
Jiali Zhang ◽  
Zhaojian Tong ◽  
Changwei Chen ◽  
...  
Keyword(s):  
Selective Catalytic Reduction ◽  
Catalytic Reduction ◽  
Reduction Of No ◽  
Nh3 Scr ◽  
So2 Adsorption ◽  
Vanadium Based Catalysts ◽  
Reduction Of Nox ◽  
So2 Tolerance

Non-vanadium-based catalysts with high SO2 tolerance are still challenging to date in selective catalytic reduction of NO by NH3 (NH3-SCR) and SO2 adsorption is the foremost step for the deactivation...

scholarly journals Recent Progress on Improving Low-Temperature Activity of Vanadia-Based Catalysts for the Selective Catalytic Reduction of NOx with Ammonia

Catalysts ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1421
Author(s):  
Zhihua Lian ◽  
Yingjie Li ◽  
Wenpo Shan ◽  
Hong He
Keyword(s):  
Low Temperature ◽  
Selective Catalytic Reduction ◽  
Large Scale ◽  
Recent Progress ◽  
Catalytic Reduction ◽  
Future Research ◽  
Synthesis Methods ◽  
Nh3 Scr ◽  
Reduction Of Nox ◽  
Commercial Applications

Selective catalytic reduction of NOx with NH3 (NH3-SCR) has been successfully applied to abate NOx from diesel engines and coal-fired industries on a large scale. Although V2O5-WO3(MoO3)/TiO2 catalysts have been utilized in commercial applications, novel vanadia-based catalysts have been recently developed to meet the increasing requirements for low-temperature catalytic activity. In this article, recent progress on the improvement of the low-temperature activity of vanadia-based catalysts is reviewed, including modification with metal oxides and nonmetal elements and the use of novel supports, different synthesis methods, metal vanadates and specific structures. Investigation of the NH3-SCR reaction mechanism, especially at low temperatures, is also emphasized. Finally, for low-temperature NH3-SCR, some suggestions are given regarding the opportunities and challenges of vanadia-based catalysts in future research.

scholarly journals The Latest Research Progress of NH3-SCR in the SO2 Resistance of the Catalyst in Low Temperatures for Selective Catalytic Reduction of NOx

Catalysts ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1034 ◽  
Author(s):  
Caixia Liu ◽  
Huijun Wang ◽  
Ziyin Zhang ◽  
Qingling Liu
Keyword(s):  
Selective Catalytic Reduction ◽  
Low Temperatures ◽  
Catalytic Reduction ◽  
Complex Oxide ◽  
Research Progress ◽  
Preparation Methods ◽  
Nh3 Scr ◽  
So2 Resistance ◽  
Reduction Of Nox ◽  
Further Development

The selective catalytic reduction (SCR) has been widely used in industrial denitrification owing to its high denitrification efficiency, low operating costs, and simple operating procedures. However, coal containing a large amount of sulfur will produce SO2 during combustion, which makes the catalyst easy to be deactivated, thus limiting the application of this technology. This review summarizes the latest NH3-SCR reaction mechanisms and the deactivation mechanism of catalyst in SO2-containing flue gas. Some strategies are summarized for enhancing the poison-resistance through modification, improvement of support, the preparation of complex oxide catalyst, optimizing the preparation methods, and acidification. The mechanism of improving sulfur resistance of catalysts at low temperatures is summarized, and the further development of the catalyst is also prospected. This paper could provide a reference and guidance for the development of SO2 resistance of the catalyst at low temperatures.

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