scholarly journals Well-Defined Surface Tungstenocarbyne complex through the Reaction of [W(≡CtBu)(CH2tBu)3] with CeO2 : a highly and stable precatalyst for NOx reduction with NH3 ≡

2021 ◽  
Author(s):  
Cherif Larabi ◽  
Cuirong chen ◽  
Nicolas Merle ◽  
marc charlin ◽  
Kai Chung Szeto ◽  
...  
Keyword(s):  
Organometallic Chemistry ◽  
Selective Catalytic Reduction ◽  
Catalytic Reduction ◽  
Nox Reduction ◽  
Active Phase ◽  
High Dispersion ◽  
Nh3 Scr ◽  
Reduction Of Nox ◽  
Surface Organometallic Chemistry

A novel well-defined precatalyst for ammonia selective catalytic reduction of NOx (NH3-SCR), [W(CtBu)(CH2tBu)3]/CeO2, was prepared by surface organometallic chemistry and characterized. Due to the high dispersion of the active phase,...

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.

scholarly journals Modified Zeolite Catalyst for a NOx Selective Catalytic Reduction Process in Nitric Acid Plants

Catalysts ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 450
Author(s):  
Magdalena Saramok ◽  
Agnieszka Szymaszek ◽  
Marek Inger ◽  
Katarzyna Antoniak-Jurak ◽  
Bogdan Samojeden ◽  
...  
Keyword(s):  
Nitric Acid ◽  
Selective Catalytic Reduction ◽  
Catalytic Reduction ◽  
Nox Reduction ◽  
Reduction Process ◽  
Active Phase ◽  
Catalytic Performance ◽  
Temperature Range ◽  
Nh3 Scr ◽  
Modified Clinoptilolite

Natural zeolite of the heulandite-type framework was modified with iron and tested as a catalyst for the selective catalytic reduction of nitrogen oxides with ammonia (NH3-SCR) in the temperature range of 150–450 °C. The catalyst was prepared at a laboratory scale in a powder form and then the series of experiments of its shaping into tablets was conducted. Physicochemical studies of the catalyst (N2 sorption at −196 °C, FT-IR, XRD, UV-vis) were performed to determine the textural and structural properties and identify the surface functional groups, the crystalline structure of the catalysts and the form and aggregation of the active phase. The activity tests over the shaped catalyst were performed industry-reflecting conditions, using tail gases from the pilot nitric acid plant. The influence of a temperature, catalyst load, and the amount of reducing agent (ammonia) on the NOx reduction process were investigated. The results of catalytic tests that were performed on model gas mixture showed that non-modified clinoptilolite exhibited around 58% conversion of NO at 450 °C. The temperature window of the shaped catalyst shifted to a higher temperature range in comparison to the powder sample. The catalytic performance of the shaped Fe-clinoptilolite in the industry-reflecting conditions was satisfactory, especially at 450 °C. Additionally, it was observed that the ratio of N2O concentration downstream and upstream of the catalytic bed was below 1, which indicated that the catalyst exhibited activity in both DeNOx and DeN2O process.

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 Selective catalytic reduction of NOx with NH3: opportunities and challenges of Cu-based small-pore zeolites

2021 ◽  
Author(s):  
Yulong Shan ◽  
Jinpeng Du ◽  
Yan Zhang ◽  
Wenpo Shan ◽  
Xiaoyan Shi ◽  
...  
Keyword(s):  
Selective Catalytic Reduction ◽  
Catalytic Reduction ◽  
Hydrothermal Stability ◽  
Catalyst Design ◽  
Scr Catalyst ◽  
Nh3 Scr ◽  
Small Pore ◽  
Fast Scr ◽  
Reduction Of Nox ◽  
Significant Opportunity

Abstract Zeolites, as efficient and stable catalysts, are widely used in the environmental catalysis field. Typically, Cu-SSZ-13 with small-pore structure shows excellent catalytic activity for selective catalytic reduction of NOx with ammonia (NH3-SCR) as well as high hydrothermal stability. This review summarizes major advances in Cu-SSZ-13 applied to the NH3-SCR reaction, including the state of copper species, standard and fast SCR reaction mechanism, hydrothermal deactivation mechanism, poisoning resistance, and synthetic methodology. The review gives a valuable summary of new insights on the matching between SCR catalyst design principles and the characteristics of Cu2+-exchanged zeolitic catalysts, highlighting the significant opportunity presented by zeolite-based catalysts. Principles for designing zeolites with excellent NH3-SCR performance and hydrothermal stability are proposed. On the basis of these principles, more hydrothermally stable Cu-AEI and Cu-LTA zeolites are elaborated as well as other alternative zeolites applied to NH3-SCR. Finally, we call attention to the challenges facing Cu-based small-pore zeolites that still need to be addressed.

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.

Effect of Formaldehyde in Selective Catalytic Reduction of NOx by Ammonia (NH3-SCR) on a Commercial V2O5-WO3/TiO2 Catalyst under Model Conditions

2020 ◽  
Vol 54 (19) ◽  
pp. 11753-11761
Author(s):  
Anh Binh Ngo ◽  
Thanh Huyen Vuong ◽  
Hanan Atia ◽  
Ursula Bentrup ◽  
Vita A. Kondratenko ◽  
...  
Keyword(s):  
Selective Catalytic Reduction ◽  
Catalytic Reduction ◽  
Tio2 Catalyst ◽  
Nh3 Scr ◽  
Reduction Of Nox

scholarly journals Ion Exchange of One-Pot Synthesized Cu-SAPO-44 with NH4NO3 to Promote Cu Dispersion and Activity for Selective Catalytic Reduction of NOx with NH3

Catalysts ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 882 ◽  
Author(s):  
Nana Zhang ◽  
Ying Xin ◽  
Qian Li ◽  
Xicheng Ma ◽  
Yongxin Qi ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Ion Exchange ◽  
Selective Catalytic Reduction ◽  
Inductively Coupled Plasma ◽  
Catalytic Reduction ◽  
One Pot ◽  
X Ray ◽  
Inductively Coupled ◽  
Nh3 Scr ◽  
Reduction Of Nox

Cu-containing CHA type (Cu-CHA) zeolites have been widely investigated owing to their excellent low-temperature activity and high hydrothermal stability in selective catalytic reduction of NOx with NH3 (NH3-SCR). Herein, a series of Cu-SAPO-44 zeolites were prepared by one-pot method with dual-amine templates and the subsequent ion exchange (IE) with NH4NO3. The effect of NH4NO3 treatment on Cu species was investigated by X-ray powder diffraction (XRD), N2 adsorption-desorption isotherm, inductively coupled plasma (ICP); field-emission scanning electron microscope (FE-SEM), high-resolution transmission electron microscope (HRTEM), X-ray absorption fine structure (XAFS), and H2-temperature-programmed reduction (H2-TPR). The results indicated that—besides the main SAPO-44 structure—the CuO phase was detected by XRD in original samples. After IE with NH4NO3, the Cu contents decreased greatly from ICP analysis. The removal of CuO agglomerations and the presence of highly dispersed CuO nanoparticles (~2.36 nm) were confirmed by SEM, TEM and H2-TPR. Furthermore, a significant increase in the proportion of isolated Cu2+ was derived from XAFS. As a result, the activity at higher temperature (≥350 °C) was improved a lot.

The Effect of Si/Al Ratio on Selective Catalytic Reduction of NOx with NH3 over Pt/Al-SBA-15

2008 ◽  
Vol 135 ◽  
pp. 61-64
Author(s):  
Min Kang ◽  
Jae Hyun Park ◽  
Eun Duck Park ◽  
Ji Man Kim ◽  
Dae Jung Kim ◽  
...  
Keyword(s):  
Selective Catalytic Reduction ◽  
Reaction Temperature ◽  
Low Temperatures ◽  
Catalytic Reduction ◽  
Pt Catalysts ◽  
Nh3 Scr ◽  
Nox Conversion ◽  
Reduction Of Nox

The selective catalytic reduction of NOx with NH3 (NH3-SCR) was investigated over Pt catalysts supported on various supports such as alumina, ZSM-5, SBA-15, and Al-SBA-15 with different amounts of alumina. Among them, Pt catalysts supported on Al-SBA-15 showed the higher NOx conversion at low temperatures than those of others. These also showed high NOx conversions over a wide reaction temperature. As the Si/Al ratio in Al-SBA-15 decreased, the NH3-SCR activity increased. This was closely related to the amount of strongly-adsorbed NH3.

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