scholarly journals Copper-Iron Bimetal Ion-Exchanged SAPO-34 for NH3-SCR of NOx

Catalysts ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 321 ◽  
Author(s):  
Tuan Doan ◽  
Phong Dam ◽  
Khang Nguyen ◽  
Thanh Huyen Vuong ◽  
Minh Thang Le ◽  
...  
Keyword(s):  
Active Sites ◽  
Catalytic Reduction ◽  
Catalytic Performance ◽  
Physical Structure ◽  
Acid Sites ◽  
Tetraethylammonium Hydroxide ◽  
Nh3 Scr ◽  
Nox Conversion ◽  
Temperature Window ◽  
Scr Of Nox

SAPO-34 was prepared with a mixture of three templates containing triethylamine, tetraethylammonium hydroxide, and morpholine, which leads to unique properties for support and production cost reduction. Meanwhile, Cu/SAPO-34, Fe/SAPO-34, and Cu-Fe/SAPO-34 were prepared through the ion-exchanged method in aqueous solution and used for selective catalytic reduction (SCR) of NOx with NH3. The physical structure and original crystal of SAPO-34 are maintained in the catalysts. Cu-Fe/SAPO-34 catalysts exhibit high NOx conversion in a broad temperature window, even in the presence of H2O. The physicochemical properties of synthesized samples were further characterized by various methods, including XRD, FE-SEM, EDS, N2 adsorption-desorption isotherms, UV-Vis-DRS spectroscopy, NH3-TPD, H2-TPR, and EPR. The best catalyst, 3Cu-1Fe/SAPO-34 exhibited high NOx conversion (> 90%) in a wide temperature window of 250–600 °C, even in the presence of H2O. In comparison with mono-metallic samples, the 3Cu-1Fe/SAPO-34 catalyst had more isolated Cu2+ ions and additional oligomeric Fe3+ active sites, which mainly contributed to the higher capacity of NH3 and NOx adsorption by the enhancement of the number of acid sites as well as its greater reducibility. Therefore, this synergistic effect between iron and copper in the 3Cu-1Fe/SAPO-34 catalyst prompted higher catalytic performance in more extensive temperature as well as hydrothermal stability after iron incorporation.

scholarly journals Numerical Investigation on the Intraphase and Interphase Mass Transfer Limitations for NH3-SCR over Cu-ZSM-5

Processes ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 1966
Author(s):  
Shiyong Yu ◽  
Jichao Zhang
Keyword(s):  
Pressure Drop ◽  
Catalytic Reduction ◽  
Nox Reduction ◽  
Catalytic Performance ◽  
No Oxidation ◽  
Relative Pressure ◽  
Nh3 Scr ◽  
Nox Conversion ◽  
Nh3 Adsorption ◽  
Media Channels

A systematic modeling approach was scrutinized to develop a kinetic model and a novel monolith channel geometry was designed for NH3 selective catalytic reduction (NH3-SCR) over Cu-ZSM-5. The redox characteristic of Cu-based catalysts and the variations of NH3, NOx concentration, and NOx conversion along the axis in porous media channels were studied. The relative pressure drop in different channels, the variations of NH3 and NOx conversion efficiency were analyzed. The model mainly considers NH3 adsorption and desorption, NH3 oxidation, NO oxidation, and NOx reduction. The results showed that the model could accurately predict the NH3-SCR reaction. In addition, it was found that the Cu-based zeolite catalyst had poor low-temperature catalytic performance and good high-temperature activity. Moreover, the catalytic reaction of NH3-SCR was mainly concentrated in the upper part of the reactor. In addition, the hexagonal channel could effectively improve the diffusion rate of gas reactants to the catalyst wall, reduce the pressure drop and improve the catalytic conversion efficiencies of NH3 and NOx.

Transition metal ions regulate the catalytic performance of Ti0.8M0.2Ce0.2O2+x for the NH3-SCR of NO: the acidic mechanism

RSC Advances ◽  
2015 ◽  
Vol 5 (10) ◽  
pp. 7597-7603 ◽  
Author(s):  
Yuesong Shen ◽  
Yun Su ◽  
Yifan Ma
Keyword(s):  
Transition Metal Ions ◽  
Catalytic Performance ◽  
Acid Sites ◽  
Acid Strength ◽  
Maximum Activity ◽  
Lewis Acid Sites ◽  
Nh3 Scr ◽  
Scr Of No ◽  
Temperature Window ◽  
Active Temperature

The maximum activity is dependent on the number of Lewis acid sites, and the active temperature window is dependent on the acid strength.

Plasma-Treated Ce/TiO2-Palygorskite Catalyst for the NH3-SCR of NOx

2019 ◽  
Vol 41 (1) ◽  
pp. 90-90
Author(s):  
Kaige Chen Kaige Chen ◽  
Ruoyu Chen Ruoyu Chen ◽  
Zhe Tang Zhe Tang ◽  
Hui Cang Hui Cang ◽  
Qi Xu Qi Xu
Keyword(s):  
Thermal Plasma ◽  
Active Sites ◽  
Alkali Metals ◽  
Performance Test ◽  
Catalytic Performance ◽  
Acid Sites ◽  
Efficient Catalyst ◽  
Nh3 Scr ◽  
Chemisorbed Oxygen ◽  
Non Thermal Plasma

Ce/TiO2-Palygorskite ternary composites were fabricated as an efficient catalyst for medium and low temperature NH3-SCR reaction and the optimal mass proportion (Ti:Pal=1:3) of this catalyst was confirmed by the catalytic performance test, in order to improve the surface dispersion , which needed to be further disposed by the Non-thermal plasma , after that, it was activated by thermal treatment at 400⁰C for 4 h. Based on the results obtained by XRD, FE-SEM, TEM, NH3-TPD, UV-vis (DRS), XPS, the treatment of plasma was much essential for the transformation from Ce4+ to Ce3+ on the surface of Ce/TiO2-palygorskite, to increase surface chemisorbed oxygen, and the improved dispersion, which were highly favorable for denitration. At about 350⁰C, the best NO conversion was respectively 90.59 % and 96.78 % for the untreated and treated catalysts, the latter possessed higher N2 selectivity. Besides, according to the research results on alkali metals poisoning resistance of these catalysts, it was discovered, the treated-catalyst poisoned by sodium salt had the best resistance performance, which might be related with the modification of the Non-thermal plasma, leading to more dispersed surface acid sites, to get more active sites, meanwhile, the toxicity of K was stronger than Na.

scholarly journals Strikingly Distinctive NH3-SCR Behavior over Cu-SSZ-13 in the Presence of NO2

2021 ◽  
Author(s):  
Yulong Shan ◽  
Guangzhi He ◽  
Jinpeng Du ◽  
Yu Sun ◽  
Zhongqi Liu ◽  
...  
Keyword(s):  
Active Sites ◽  
Density Functional ◽  
Catalytic Reduction ◽  
Acid Sites ◽  
Zeolite Catalysts ◽  
Nh3 Scr ◽  
Highly Active ◽  
Small Pore ◽  
Standard Scr ◽  
Catalyst Systems

Abstract Commercial Cu-exchanged small-pore SSZ-13 (Cu-SSZ-13) zeolite catalysts are highly active for the selective catalytic reduction (SCR) of NOx with NH3, but distinct from other catalyst systems, their activity is unexpectedly inhibited in the presence of NO2. Here, we combined kinetic experiments, in-situ/operando X-ray absorption spectroscopy, and density functional theory (DFT) calculations to obtain direct evidence that under reaction conditions, strong oxidation by NO2 forces Cu ions to exist mainly as fixed framework Cu2+ species (fw-Cu2+), which impede the formation of dynamic binuclear Cu+ species that serve as the main active sites for the standard SCR (SSCR) reaction. As a result, the SSCR reaction is significantly inhibited by NO2 in the zeolite system, and the NO2-involved SCR reaction occurs with an energy barrier higher than that of the SSCR reaction on dynamic binuclear sites. Moreover, the NO2-involved SCR reaction tends to occur at the Brønsted acid sites (BAS) rather than the fw-Cu2+ sites. This work clearly explains the strikingly distinctive selective catalytic behavior in the zeolite system.

Influence of Aluminum Sources on Synthesis of SAPO-34 and NH3-SCR of NOx by as-Prepared Cu/SAPO-34 Catalysts

2020 ◽  
Vol 20 (5) ◽  
pp. 373
Author(s):  
Tuan Doan ◽  
Anh Dang ◽  
Dat Nguyen ◽  
Khanh Dinh ◽  
Phong Dam ◽  
...  
Keyword(s):  
Flow Reactor ◽  
Fixed Bed ◽  
Acid Sites ◽  
Hydrothermal Conditions ◽  
Exchange Method ◽  
Characterization Methods ◽  
Cu Content ◽  
Tetraethylammonium Hydroxide ◽  
Nh3 Scr ◽  
Scr Of Nox

The full article will be published in the English version of the  journal "Catalysis in Industry" No. 1, 2021.The synthesis of the microporous SAPO-34 molecular sieve goes from a combination of three templates: triethylamine, tetraethylammonium hydroxide, and morpholine under hydrothermal conditions. Two aluminum sources, namely aluminum hydroxide, and aluminum isopropoxide, were used exclusively to synthesize SAPO-34 zeolites. The effects of aluminum sources on the crystallization and physicochemical properties of SAPO-34 were studied thoroughly. The synthesized samples were characterized by using different characterization methods, including XRD, FE-SEM, N2 isotherm, EDS, and NH3-TPD. The results illustrate that the various sources of aluminum used for the synthesis of SAPO-34 materials extremely affect the crystallinity, morphology, and density of acid sites. Besides, the influence of aluminum sources on the performance of NH3-SCR technology was studied with Cu/SAPO-34 catalysts in a fixed-bed flow reactor. The two Cu/SAPO-34 catalysts promoted different NO and NH3 conversions between 200–600 °C though they share similar Cu content, which was loaded by the ion-exchange method in aqueous solution. In addition, the different Cu species in the two catalyst samples are surveyed by H2-TPR, while the EPR method is also used to assess the coordination of the copper element in the two catalysts.

scholarly journals The Study of C3H6 Impact on Selective Catalytic Reduction by Ammonia (NH3-SCR) Performance over Cu-SAPO-34 Catalysts

Catalysts ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1327
Author(s):  
Yingfeng Duan ◽  
Lina Wang ◽  
Yagang Zhang ◽  
Wei Du ◽  
Yating Zhang
Keyword(s):  
Reaction Rate ◽  
Catalytic Reduction ◽  
Catalytic Performance ◽  
Coke Deposition ◽  
In Situ Drifts ◽  
Nh3 Scr ◽  
Nox Conversion ◽  
Temperature Ranges ◽  
And Performance

In present work, the catalytic performance of Cu-SAPO-34 catalysts with or without propylene during the NH3-SCR process was conducted, and it was found that the de-NOx activity decreased during low temperature ranges (<350 °C), but obviously improved within the range of high temperatures (>350 °C) in the presence of propylene. The XRD, BET, TG, NH3-TPD, NOx-TPD, in situ DRIFTS and gas-switch experiments were performed to explore the propylene effect on the structure and performance of Cu-SAPO-34 catalysts. The bulk characterization and TG results revealed that neither coke deposition nor the variation of structure and physical properties of catalysts were observed after C3H6 treatment. Generally speaking, at the low temperatures (<350 °C), active Cu2+ species could be occupied by propylene, which inhibited the adsorption and oxidation of NOx species, confining the SCR reaction rate and causing the deactivation of Cu-SAPO-34 catalysts. However, with the increase of reaction temperatures, the occupied Cu2+ sites would be recovered and sequentially participate into the NH3-SCR reaction. Additionally, C3H6-SCR reaction also showed the synergetic contribution to the improvement of NOx conversion at high temperature (>350 °C).

scholarly journals Insights over Titanium Modified FeMgOx Catalysts for Selective Catalytic Reduction of NOx with NH3: Influence of Precursors and Crystalline Structures

Catalysts ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 560 ◽  
Author(s):  
Liting Xu ◽  
Qilei Yang ◽  
Lihua Hu ◽  
Dong Wang ◽  
Yue Peng ◽  
...  
Keyword(s):  
Mixed Oxides ◽  
Catalytic Reduction ◽  
Strong Acid ◽  
Catalytic Performance ◽  
Acid Sites ◽  
Side Reactions ◽  
Amorphous Iron ◽  
Nox Conversion ◽  
Surface Active ◽  
Strong Acid Sites

Titanium modified FeMgOx catalysts with different precursors were prepared by coprecipitation method with microwave thermal treatment. The iron precursor is a key factor affecting the surface active component. The catalyst using FeSO4 and Mg(NO3)2 as precursors exhibited enhanced catalytic activity from 225 to 400 °C, with a maximum NOx conversion of 100%. Iron oxides existed as γ-Fe2O3 in this catalyst. They exhibited highly enriched surface active oxygen and surface acidity, which were favorable for low-temperature selective catalytic reduction (SCR) reaction. Besides, it showed advantage in surface area, spherical particle distribution and pores connectivity. Amorphous iron-magnesium-titanium mixed oxides were the main phase of the catalysts using Fe(NO3)3 as a precursor. This catalyst exhibited a narrow T90 of 200/250–350 °C. Side reactions occurred after 300 °C producing NOx, which reduced the NOx conversion. The strong acid sites inhibited the side reactions, and thus improved the catalytic performance above 300 °C. The weak acid sites appeared below 200 °C, and had a great impact on the low-temperature catalytic performance. Nevertheless, amorphous iron-magnesium-titanium mixed oxides blocked the absorption and activation between NH3 and the surface strong acid sites, which was strengthened on the γ-Fe2O3 surface.

scholarly journals Ce and Zr Modified WO3-TiO2 Catalysts for Selective Catalytic Reduction of NOx by NH3

Catalysts ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 375 ◽  
Author(s):  
Wenyi Zhao ◽  
Zhaoqiang Li ◽  
Yan Wang ◽  
Rongrong Fan ◽  
Cheng Zhang ◽  
...  
Keyword(s):  
Selective Catalytic Reduction ◽  
Catalytic Reduction ◽  
Catalytic Performance ◽  
Acid Sites ◽  
Impregnation Method ◽  
Engine Exhaust ◽  
Operation Temperature ◽  
Nh3 Scr ◽  
Catalyst Composition ◽  
Contour Lines

A series of Ce and/or Zr modified WO3-TiO2 catalysts were synthesized by the impregnation method, which were employed for NH3-SCR reaction. The T50 contour lines of NOx were used to quickly optimize catalyst composition, the Ce20Zr12.5WTi catalyst was considered to be the optimization result, and also exhibited excellent NH3-SCR activity and thermal stability with broad operation temperature window, which is a very promising catalyst for NOx abatement from diesel engine exhaust. The excellent catalytic performance is associated with the formation of Ce-Zr solid solution. The introduction of Zr to CeWTi catalyst facilitated the redox of Ce4+/Ce3+ and the formation of more acid sites, more Ce3+ ions, more oxygen vacancies, larger quantities of surface adsorbed oxygen species and NH3, which were beneficial for the excellent selective catalytic reduction (SCR) performance.

scholarly journals Promoting Effect of Mn on In Situ Synthesized Cu-SSZ-13 for NH3-SCR

Catalysts ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1375
Author(s):  
Jinpeng Du ◽  
Jingyi Wang ◽  
Xiaoyan Shi ◽  
Yulong Shan ◽  
Yan Zhang ◽  
...  
Keyword(s):  
Low Temperature ◽  
Active Sites ◽  
Catalytic Reduction ◽  
Acid Sites ◽  
Promoting Effect ◽  
Nh3 Scr ◽  
Temperature Programmed ◽  
Diffuse Reflectance Infrared ◽  
Redox Ability

The effect of Mn impregnation on the NH3-SCR (selective catalytic reduction of NOx by NH3) activity of in situ synthesized Cu-SSZ-13 was investigated in this work. It was found that Mn addition could efficiently improve the low-temperature activity of Cu-SSZ-13. The optimal amount of Mn was 5 wt.%, and NOx conversion was improved by more than 20% over a temperature range of 120 °C to 150 °C. SEM (scanning electron microscopy), XRD (X-ray diffraction), N2 adsorption-desorption, H2-TPR (temperature programmed reduction of H2), NH3-TPD (temperature programmed desorption of NH3) and in situ DRIFTS (diffuse reflectance infrared Fourier transform spectroscopy) experiments were conducted to investigate the changes in the zeolite structure, active sites, acid sites and reaction mechanism. The impregnated MnOx species caused a decline in the crystallinity of Cu-SSZ-13 but markedly improved the redox ability. Nitrate and nitrite species were observed in the Mn-modified Cu-SSZ-13, and the formation of these species was thought to cause the observed increase in low-temperature NH3-SCR activity. The results show that the addition of Mn is a promising method for promoting the low-temperature catalytic activity of Cu-SSZ-13.

Investigation of the Performance of V-W Based Catalysts at Low Temperature for NOx Reduction with NH3

2011 ◽  
Vol 197-198 ◽  
pp. 811-816
Author(s):  
Xin Na Tian ◽  
You Hong Xiao ◽  
Wen Ping Zhang ◽  
Yong Wei Chen
Keyword(s):  
Low Temperature ◽  
Catalytic Reduction ◽  
Nox Reduction ◽  
Potential Method ◽  
Catalytic Performance ◽  
Metal Catalyst ◽  
Impregnation Method ◽  
Operation Temperature ◽  
Nox Conversion ◽  
Temperature Window

The most potential method of selective catalytic reduction (SCR) to remove NOx from diesel engine emissions is very effective in NOx reduction with an efficiency up to 95%. However, the current SCRs have a limitation on operation temperature and a narrow operation temperature window. In this paper, the V-W based catalysts were used in the investigation to improve the low temperature performance of NOx conversion by doping Cu and Mn into V-W based catalyst. The temperature range studied was between 150 °C and 550 °C with an interval of 50 °C. The honeycomb catalysts were prepared by an impregnation method. The study also included characterization of catalysts by BET, XRD, TPD and XPS methods.It is found that NOx conversion performance of the V-W based catalyst increases with the increase of reaction temperature. After the metal Cu or Mn doped into the catalyst, it offers an improvement in the catalytic performance. Among all the catalysts studied, the mixed metal catalyst of Cu-Mn-V-W catalyst is found the most potential one, not only because of its higher NOx conversion rate at a low temperature, but also because of its wider operation temperature window.

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