scholarly journals Byproduct Analysis of SO2 Poisoning on NH3-SCR over MnFe/TiO2 Catalysts at Medium to Low Temperatures

Catalysts ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 265 ◽  
Author(s):  
Tsungyu Lee ◽  
Hsunling Bai
Keyword(s):  
Reaction Temperature ◽  
Catalytic Reduction ◽  
No Oxidation ◽  
Ammonium Salts ◽  
Oxidation Reactions ◽  
No Conversion ◽  
Nh3 Scr ◽  
So2 Poisoning ◽  
No Consumption ◽  
Nh3 Oxidation

The byproducts of ammonia-selective catalytic reduction (NH3-SCR) process over MnFe/TiO2 catalysts under the conditions of both with and without SO2 poisoning were analyzed. In addition to the NH3-SCR reaction, the NH3 oxidation and the NO oxidation reactions were also evaluated at temperatures of 100–300 °C to clarify the reactions occurred during the SCR process. The results indicated that major byproducts for the NH3 oxidation and NO oxidation tests were N2O and NO2, respectively, and their concentrations increased as the reaction temperature increased. For the NH3-SCR test without the presence of SO2, it revealed that N2O was majorly from the NH3-SCR reaction instead of from NH3 oxidation reaction. The byproducts of N2O and NO2 for the NH3-SCR reaction also increased after increasing the reaction temperature, which caused the decreasing of N2-selectivity and NO consumption. For the NH3-SCR test with SO2 at 150 °C, there were two decay stages during SO2 poisoning. The first decay was due to a certain amount of NH3 preferably reacted with SO2 instead of with NO or O2. Then the catalysts were accumulated with metal sulfates and ammonium salts, which caused the second decay of NO conversion. The effluent N2O increased as poisoning time increased, which was majorly from oxidation of unreacted NH3. On the other hand, for the NH3-SCR test with SO2 at 300 °C, the NO conversion was not decreased after increasing the poisoning time, but the N2O byproduct concentration was high. However, the SO2 led to the formation of metal sulfates, which might inhibit NO oxidation reactions and cause the concentration of N2O gradually decreased as well as the N2-selectivity increased.

scholarly journals Insight into Platinum Poisoning Effect on Cu-SSZ-13 in Selective Catalytic Reduction of NOx with NH3

Catalysts ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 796
Author(s):  
Huawang Zhao ◽  
Lei Han ◽  
Yujie Wang ◽  
Jiandong Zheng
Keyword(s):  
Catalytic Reduction ◽  
No Oxidation ◽  
Oxidation Reactions ◽  
Hydrothermal Aging ◽  
N2o Formation ◽  
Poisoning Effect ◽  
Nh3 Oxidation ◽  
Reduction Of Nox ◽  
Parallel Reactions ◽  
Insight Into

Platinum’s (Pt) poisoning effect on Cu-SSZ-13 and its regeneration were investigated. The Pt enhanced the parallel reactions, such as NH3 oxidation and NO oxidation reactions, which decreased the deNOx activities. In the temperature range below 330 °C, the deactivation of Cu-SSZ-13 by Pt poisoning was primarily caused by the overconsumption of NH3, due to the enhanced NH3-selective oxidation reaction, while the formation of NOx in NH3 oxidation and NO oxidation into NO2 further aggravated the degradation when the temperature was above 460 °C. The non-selective NH3 oxidation and non-selective NOx catalytic reduction reactions resulted in increased N2O formation over Pt-doped samples. The transformation of Pt0 into PtOx after hydrothermal aging recovered the deNOx activities of the Pt-poisoned samples.

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.

scholarly journals Deactivation of Cu/SSZ-13 NH3-SCR Catalyst by Exposure to CO, H2, and C3H6

Catalysts ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 929 ◽  
Author(s):  
Auvray ◽  
Mihai ◽  
Lundberg ◽  
Olsson
Keyword(s):  
Flow Reactor ◽  
Catalytic Reduction ◽  
Plug Flow ◽  
Acid Sites ◽  
Drift Spectroscopy ◽  
Scr Catalyst ◽  
Nh3 Scr ◽  
Scr Catalysts ◽  
Nh3 Oxidation ◽  
Diffuse Reflectance Infrared

Lean nitric oxide (NOx)-trap (LNT) and selective catalytic reduction (SCR) are efficient systems for the abatement of NOx. The combination of LNT and SCR catalysts improves overall NOx removal, but there is a risk that the SCR catalyst will be exposed to high temperatures and rich exhaust during the LNTs sulfur regeneration. Therefore, the effect of exposure to various rich conditions and temperatures on the subsequent SCR activity of a Cu-exchanged chabazite catalyst was studied. CO, H2, C3H6, and the combination of CO + H2 were used to simulate rich conditions. Aging was performed at 800 °C, 700 °C, and, in the case of CO, 600 °C, in a plug-flow reactor. Investigation of the nature of Cu sites was performed with NH3-temperature-programed desorption (TPD) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) of probe molecules (NH3 and NO). The combination of CO and H2 was especially detrimental to SCR activity and to NH3 oxidation. Rich aging with low reductant concentrations resulted in a significantly larger deactivation compared to lean conditions. Aging in CO at 800 °C caused SCR deactivation but promoted high-temperature NH3 oxidation. Rich conditions greatly enhanced the loss of Brønsted and Lewis acid sites at 800 °C, indicating dealumination and Cu migration. However, at 700 °C, mainly Brønsted sites disappeared during aging. DRIFT spectroscopy analysis revealed that CO aging modified the Cu2+/CuOH+ ratio in favor of the monovalent CuOH+ species, as opposed to lean aging. To summarize, we propose that the reason for the increased deactivation observed for mild rich conditions is the transformation of the Cu species from Z2Cu to ZCuOH, possibly in combination with the formation of Cu clusters.

scholarly journals Improvement of Alkali Metal Resistance for NH3-SCR Catalyst Cu/SSZ-13: Tune the Crystal Size

Catalysts ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 979
Author(s):  
Zexiang Chen ◽  
Meiqing Shen ◽  
Chen Wang ◽  
Jianqiang Wang ◽  
Jun Wang ◽  
...  
Keyword(s):  
Alkali Metal ◽  
Crystal Size ◽  
Catalytic Reduction ◽  
Side Reaction ◽  
Physical Structure ◽  
Metal Resistance ◽  
Structure Characterization ◽  
Simple Method ◽  
Nh3 Scr ◽  
Nh3 Oxidation

To improve the alkali metal resistance of commercial catalyst Cu/SSZ-13 for ammonia selective catalytic reduction (NH3-SCR) reaction, a simple method to synthesize Cu/SSZ-13 with a core–shell like structure was developed. Compared with smaller-sized counterparts, Cu/SSZ-13 with a crystal size of 2.3 μm exhibited excellent resistance to Na poisoning. To reveal the influence of the crystal size on Cu/SSZ-13, physical structure characterization (XRD, BET, SEM, NMR) and chemical acidic distribution (H2-TPR, UV-Vis, Diethylamine-TPD, pyridine-DRIFTs, EDS) were investigated. It was found that the larger the crystal size of the molecular sieve, the more Cu is distributed in the crystal core, and the less likely it was to be replaced by Na to generate CuO. Therefore, a 2.3 μm sized Cu/SSZ-13 well-controlled the reactivity of the side reaction NH3 oxidation and the generation of N2O. The result was helpful to guide the extension of the service life of Cu/SSZ-13.

scholarly journals High Resistance of SO2 and H2O over Monolithic Mn-Fe-Ce-Al-O Catalyst for Low Temperature NH3-SCR

Catalysts ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1329
Author(s):  
Shijie Hao ◽  
Yandi Cai ◽  
Chuanzhi Sun ◽  
Jingfang Sun ◽  
Changjin Tang ◽  
...  
Keyword(s):  
Low Temperature ◽  
Catalytic Reduction ◽  
No Conversion ◽  
Nh3 Scr ◽  
Chemisorbed Oxygen ◽  
Scr Of No ◽  
Ft Ir ◽  
Redox Ability ◽  
First Time ◽  
Successive Operation

Monolithic Mn-Fe-Ce-Al-O catalyst with honeycomb cordierite ceramic as a carrier was reported for the first time for low temperature deNOx application. In the reaction of selective catalytic reduction (SCR) of NO with NH3, a NO conversion of above 80% at 100 °C was obtained. Notably, the catalyst also showed excellent resistance against SO2 and H2O. About 60% NO conversion was maintained after successive operation in the mixed stream of SO2 and H2O for 168 h. The Brunner−Emmet−Teller (BET) measurement, SEM, EDS, thermogravimetric analysis (TG), FT-IR, and XPS results of the used catalysts indicated that certain amounts of ammonium sulfate was formed on the surface of the catalyst. XPS results revealed that partial of Fe2+ was oxidized to Fe3+ during the reaction process, and Fe2+ species have strong redox ability, which can explain the decrease in activity after reaction. In addition, SO2 and H2O induced a transformation of Ce from Ce4+ to Ce3+ on the surface of the catalyst, which increased the amount of chemisorbed oxygen. Owing to these factors, the addition of Ce and Fe species contributes to excellent resistance of the catalyst to SO2 and H2O.

scholarly journals SO2 Poisoning and Recovery of Copper-Based Activated Carbon Catalysts for Selective Catalytic Reduction of NO with NH3 at Low Temperature

Catalysts ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1426
Author(s):  
Marwa Saad ◽  
Agnieszka Szymaszek ◽  
Anna Białas ◽  
Bogdan Samojeden ◽  
Monika Motak
Keyword(s):  
Activated Carbon ◽  
Selective Catalytic Reduction ◽  
Active Sites ◽  
Catalytic Reduction ◽  
Incipient Wetness Impregnation ◽  
Exhaust Gas ◽  
Impregnation Method ◽  
No Conversion ◽  
So2 Poisoning ◽  
Carbon Catalysts

A series of materials based on activated carbon (AC) with copper deposited in various amounts were prepared using an incipient wetness impregnation method and tested as catalysts for selective catalytic reduction of nitrogen oxides with ammonia. The samples were poisoned with SO2 and regenerated in order to analyze their susceptibility to deactivation by the harmful component of exhaust gas. NO conversion over the fresh catalyst doped with 10 wt.% of Cu reached 81% of NO conversion at 140 °C and about 90% in the temperature range of 260–300 °C. The rate of poisoning with SO2 was dependent on Cu loading, but in general, it lowered NO conversion due to the formation of (NH4)2SO4 deposits that blocked the active sites of the catalysts. After regeneration, the catalytic activity of the materials was restored and NO conversion exceeded 70% for all of the samples.

scholarly journals Co-precipitation Synthesized MnOx-CeO2 Mixed Oxides for NO Oxidation and Enhanced Resistance to Low Concentration of SO2 by Metal Addition

Catalysts ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 519 ◽  
Author(s):  
Jiaming Shao ◽  
Fawei Lin ◽  
Yan Li ◽  
Hairong Tang ◽  
Zhihua Wang ◽  
...  
Keyword(s):  
Calcination Temperature ◽  
Conversion Efficiency ◽  
Mixed Oxides ◽  
No Oxidation ◽  
Precipitation Method ◽  
No Conversion ◽  
So2 Poisoning ◽  
Negative Effect ◽  
Co Precipitation ◽  
Metal Addition

NO oxidation was conducted over MnOx-CeO2 catalysts, which were synthesized by the co-precipitation method. The calcination temperature and third metal doping were the main considerations. MnCe catalysts calcined at 350 °C and 450 °C attained the highest NO conversion efficiency, compared to 550 °C. XRD results suggested that the higher the calcination temperature, the higher the crystallization degree, which led to a negative effect on catalytic activity. Subsequently, Sn, Fe, Co, Cr, and Cu were separately doped into MnCe composites, but no improvement was observed for these trimetallic catalysts in NO conversion. Nevertheless, MnCeSn, MnCeFe, and MnCeCo still exhibited a desirable NO conversion efficiency, so they were tested under SO2 addition together with MnCe catalyst. Among them, MnCeFe exhibited the highest NO conversion after whole poisoning testing. XPS results indicated that Fe could protect Mn and Ce metal oxides from being reduced during SO2 poisoning process. Furthermore, in in-situ DRIFTS measurement, part of nitrate species maintained undestroyed on the MnCeFe catalyst surface after SO2 poisoning. These characteristics reinforced that Fe dropping would achieve better performance under SO2 atmosphere.

scholarly journals Cu-IM-5 as the Catalyst for Selective Catalytic Reduction of NOx with NH3: Role of Cu Species and Reaction Mechanism

Catalysts ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 221
Author(s):  
Guangying Fu ◽  
Junwen Chen ◽  
Yuqian Liang ◽  
Rui Li ◽  
Xiaobo Yang ◽  
...  
Keyword(s):  
Reaction Mechanism ◽  
Selective Catalytic Reduction ◽  
Low Temperatures ◽  
Catalytic Reduction ◽  
Oxidation Activity ◽  
Paramagnetic Resonance ◽  
Nh3 Scr ◽  
Nh3 Oxidation ◽  
Diffuse Reflectance Infrared

The role of Cu species in Cu ion-exchanged IM-5 zeolite (Cu-IM-5) regarding the performance in selective catalytic reduction (SCR) of NOx with NH3 (NH3-SCR) and the reaction mechanism was studied. Based on H2 temperature-programmed reduction (H2-TPR) and electron paramagnetic resonance (EPR) results, Cu–O–Cu and isolated Cu species are suggested as main Cu species existing in Cu-IM-5 and are active for SCR reaction. Cu–O–Cu species show a good NH3-SCR activity at temperatures below 250 °C, whereas their NH3 oxidation activity at higher temperatures hinders the SCR performance. At low temperatures, NH4NO3 and NH4NO2 are key reaction intermediates. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) suggests a mixed Eley–Rideal (E–R) and Langmuir–Hinshelwood (L–H) mechanism over Cu-IM-5 at low temperatures.

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.

scholarly journals Sb-Containing Metal Oxide Catalysts for the Selective Catalytic Reduction of NOx with NH3

Catalysts ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1154
Author(s):  
Qian Xu ◽  
Dandan Liu ◽  
Chuchu Wang ◽  
Wangcheng Zhan ◽  
Yanglong Guo ◽  
...  
Keyword(s):  
Metal Oxides ◽  
Selective Catalytic Reduction ◽  
Lewis Acid ◽  
Catalytic Reduction ◽  
No Oxidation ◽  
Bronsted Acid ◽  
Brønsted Acid ◽  
Nh3 Scr ◽  
Brönsted Acid ◽  
Nh3 Adsorption

Sb-containing catalysts (SbZrOx (SbZr), SbCeOx (SbCe), SbCeZrOx (SbCeZr)) were prepared by citric acid method and investigated for the selective catalytic reduction (SCR) of NOx with NH3 (NH3-SCR). SbCeZr outperformed SbZr and SbCe and exhibited the highest activity with 80% NO conversion in the temperature window of 202–422 °C. Meanwhile, it also had good thermal stability and resistance against H2O and SO2. Various characterization methods, such as XRD, XPS, H2-TPR, NH3-TPD, and in situ diffuse reflectance infrared Fourier transform (DRIFT), were applied to understand their different behavior in NOx removal. The presence of Sb in the metal oxides led to the difference in acid distribution and redox property, which closely related with the NH3 adsorption and NO oxidation. Brønsted acid and Lewis acid were evenly distributed on SbCe, while Brønsted acid dominated on SbCeZr. Compared with Brønsted acid, Lewis acid was slightly active in NH3-SCR. The competition between NH3 adsorption and NO oxidation was dependent on SbOx and metal oxides, which were found on SbCe while not on SbCeZr.

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