scholarly journals Effect of Ion-Exchange Sequences on Catalytic Performance of Cerium-Modified Cu-SSZ-13 Catalysts for NH3-SCR

Catalysts ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 997
Author(s):  
Yan Wang ◽  
Zhaoqiang Li ◽  
Zhiyong Ding ◽  
Na Kang ◽  
Rongrong Fan ◽  
...  
Keyword(s):  
Ion Exchange ◽  
Copper Ions ◽  
Reduction Process ◽  
Catalytic Performance ◽  
Adsorbed Species ◽  
Exchange Method ◽  
Coordination Environment ◽  
Nh3 Scr ◽  
Nox Conversion ◽  
Acidic Sites

Cerium-modified Cu-SSZ-13 catalysts were prepared by an aqueous ion-exchange method, and Ce and Cu were incorporated through different ion-exchange sequences. The results of NH3-SCR activity evaluations displayed that Cu1(CeCu)2 catalyst presented excellent catalytic activity, and over 90% NOx conversion was obtained across the temperature range of 200–500 °C. The characterization results showed that the ion-exchange sequence of Cu and Ce species influenced the crystallinity of the zeolites and the coordination of Al. A small amount of Ce could participate in the reduction process and change the location and coordination environment of copper ions. Furthermore, Ce-modified Cu-SSZ-13 catalysts possessed more acidic sites due to their containing replacement of Ce and movement of Cu in the preparation process. The cooperation of strong redox abilities and NH3 storage capacity led to the increase of active adsorbed species adsorption and resulted in better activity of Cu1(CeCu)2.

The role of various iron species in Fe-β catalysts with low iron loadings for NH3-SCR

2014 ◽  
Vol 4 (5) ◽  
pp. 1350-1356 ◽  
Author(s):  
Haiyan Liu ◽  
Jun Wang ◽  
Tie Yu ◽  
Shikuan Fan ◽  
Meiqing Shen
Keyword(s):  
Ion Exchange ◽  
Iron Species ◽  
Exchange Method ◽  
Nh3 Scr ◽  
Ion Exchange Method

A series of Fe-β catalysts, containing 0.17–0.52 wt% Fe, were prepared by a liquid ion-exchange method to study the influence of various iron species on NH3-SCR activity.

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 The Effect of Tourmaline on SCR Denitrification Activity of MnOx/TiO2 at Low Temperature

Catalysts ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1020
Author(s):  
Yizhe Helian ◽  
Suping Cui ◽  
Xiaoyu Ma
Keyword(s):  
Low Temperature ◽  
Catalytic Reduction ◽  
Catalytic Performance ◽  
Scr Catalyst ◽  
Highly Efficient ◽  
Nh3 Scr ◽  
Catalytic Material ◽  
Acidic Sites ◽  
Denitrification Activity ◽  
The Stability

Selective catalytic reduction (SCR) technology is the most widely used flue gas denitration technology at present. The stability of a catalyst is the main factor limiting the development of this technology. In this study, an environmentally friendly and highly efficient NH3-SCR catalyst was prepared by coprecipitation method from acidolysis residue of industrial waste and tourmaline. We found that the addition of tourmaline has an important impact on the denitration activity of the catalytic material. The NOx conversion exceeded 97% at 200 °C with the dosage of 10% tourmaline, which is about 7% higher than that without doping. The improvement of catalytic performance was mostly attributed to the permanent electrodes of tourmaline, which effectively promotes the dispersion of MnOx/TiO2 catalytic materials, increases the number of acidic sites and changes the valence distribution of manganese ions in products, which speeds up the diffusion of protons and ions, resulting in the acceleration of redox reaction. These as-developed tourmaline-modified MnOx/TiO2 materials have been demonstrated to be promising as a new type of highly efficient low-temperature NH3-SCR catalyst.

Effect of the Zeolitic Matrix on the Reduction Process of Cu2+ Cations in Clinoptilolite, Mordenite and Erionite

2014 ◽  
Vol 880 ◽  
pp. 48-52 ◽  
Author(s):  
Inocente Rodríguez-Iznaga ◽  
Vitalii Petranovskii ◽  
Miguel Ángel Hernández Espinosa ◽  
Felipe Castillón Barraza ◽  
Alexey Pestryakov
Keyword(s):  
Ion Exchange ◽  
Copper Nanoparticles ◽  
Copper Ions ◽  
Charge Transfer Band ◽  
Copper Ion ◽  
Reduction Process ◽  
The State ◽  
Hydrogen Flow ◽  
Resonance Band ◽  
Natural Clinoptilolite

Three different zeolites (erionite, mordenite and natural clinoptilolite) were used to study influence of zeolite topology on the state of copper during ion-exchange and following reduction in hydrogen flow. This comparative study clearly demonstrates the influence of used zeolite matrices on the process of implantation of copper nanospecies. Starting from the ion-exchange, the alterations in the state of Cu2+ ions start to be evident due to variations of the intensity of charge transfer band. Copper ions start to reduce at specific temperatures depending on the type of zeolite matrix. Copper plasma resonance band change its shape and position for different zeolites. In the case of Cu-CLI samples this band change both the shape and position for different temperature of reduction. These observations permit to suggest that the mechanism of copper ion reduction and agglomeration to form copper nanoparticles noticeably depend on the type of zeolite matrix. This mechanism is more complex for the Cu CLI than for the Cu-MOR and Cu-ERI systems. Copper nanoparticles formed at low temperatures in the case of Cu-CLI samples undergo changes while temperature of reduction grow.

Investigation on the stability of copper modification of SAPO-34 catalysts in NH3-SCR reaction after hydrothermal aging

2020 ◽  
Vol 98 (5) ◽  
pp. 236-243
Author(s):  
Xiaoxin Wu ◽  
Jiaxi Peng ◽  
Shaoming Yang ◽  
Wenyuan Xu
Keyword(s):  
Ion Exchange ◽  
Copper Oxide ◽  
Structural Stability ◽  
Solid State Nmr ◽  
Impregnation Method ◽  
Hydrothermal Aging ◽  
Exchange Method ◽  
Nh3 Scr ◽  
Ion Exchange Method ◽  
The Stability

The influence of hydrothermal aging on the structural stability of Cu-modified SAPO-34 prepared by ion-exchange and impregnation methods was studied. XRD, Ar adsorption at −196 °C, solid-state NMR, UV–vis, H2-TPR, and EPR were used to probe the structural properties of the catalysts. It was found that the precipitation of crystalline AlPO4 and SiO2, the appearance of mesopores, the migration of silicon to form siliceous islands, and the formation of copper oxide crystallites occurred in aged catalysts. Furthermore, more siliceous islands and copper oxide crystallites were present in the aged samples prepared by the impregnation method than in those prepared by the ion-exchange method. Therefore, the impregnated catalysts show a much poorer structural stability than the ion-exchanged catalysts, which leads to more serious deterioration in the NH3-SCR reaction after hydrothermal aging.

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.

Zn2+, Fe2+, Cu2+, Mn2+, H+ Ion-exchanged and Raw Clinoptilolite Zeolite Catalytic Performance in the Propane-SCR-NOx Process: A Comparative Study

2017 ◽  
Vol 16 (1) ◽  
Author(s):  
Naser Ghasemian ◽  
Cavus Falamaki
Keyword(s):  
Transition Metal ◽  
Catalytic Reduction ◽  
Reduction Process ◽  
Transition Metal Ions ◽  
Catalytic Performance ◽  
Metallic Ions ◽  
Product Gas ◽  
Maximum Conversion ◽  
Acidic Sites ◽  
Natural Clinoptilolite

AbstractAn investigation on the catalytic performance of various transition-metal ions-exchanged clinoptilolite zeolites in the propane selective catalytic reduction process of NOx(NO+NO2) is reported for the first time. The metallic ions include Zn2+, Fe2+, Cu2+and Mn2+. The catalytic performance of these materials was compared with the proton form and natural clinoptilolite zeolites. Compared with the raw and H-form clinoptilolite, the ion-exchanged zeolites shift the temperature corresponding to the maximum conversion around 50 °C towards lower temperatures, irrespective of the type of used transition-metal used. The maximum conversion is substantially enhanced especially in the case of Cu2+and Mn2+-exchanged zeolite. The enhanced activity is attributed to the creation of strong acidic sites, redox centers, enhanced specific surface area and residual extra framework Fe species. Ion-exchange with transition metals results in a distinct effect on the reduction of the CO concentration in the product gas stream. Cu2+exchanged clinoptilolite resulted in the smallest outlet concentration of CO, i. e. about 81 % reduction with respect to the protonated zeolite form.

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.

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