Ferrierite and Its Delaminated and Silica-Intercalated Forms Modified with Copper as Effective Catalysts for NH3-SCR Process

The main goal of the study was the development of effective catalysts for the low-temperature selective catalytic reduction of NO with ammonia (NH3-SCR), based on ferrierite (FER) and its delaminated (ITQ-6) and silica-intercalated (ITQ-36) forms modified with copper. The copper exchange zeolitic samples, with the intended framework Si/Al ratio of 30 and 50, were synthetized and characterized with respect to their chemical composition (ICP-OES), structure (XRD), texture (low-temperature N2 adsorption), form and aggregation of deposited copper species (UV-vis-DRS), surface acidity (NH3-TPD) and reducibility (H2-TPR). The samples of the Cu-ITQ-6 and Cu-ITQ-36 series were found to be significantly more active NH3-SCR catalysts compared to Cu-FER. The activity of these catalysts in low-temperature NH3-SCR was assigned to the significant contribution of highly dispersed copper species (monomeric cations and small oligomeric species) catalytically active in the oxidation of NO to NO2, which is necessary for fast-SCR. The zeolitic catalysts, with the higher framework alumina content, were more effective in high-temperature NH3-SCR due to their limited catalytic activity in the side reaction of ammonia oxidation.

Download Full-text

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

Materials ◽

10.3390/ma13214885 ◽

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.

Download Full-text

Spherical Al-MCM-41 Doped with Copper by Modified TIE Method as Effective Catalyst for Low-Temperature NH3-SCR

Molecules ◽

10.3390/molecules26061807 ◽

2021 ◽

Vol 26 (6) ◽

pp. 1807

Author(s):

Aleksandra Jankowska ◽

Andrzej Kowalczyk ◽

Małgorzata Rutkowska ◽

Marek Michalik ◽

Lucjan Chmielarz

Keyword(s):

Low Temperature ◽

Ion Exchange ◽

Ammonia Oxidation ◽

Surface Acidity ◽

Ammonia Solution ◽

Exchange Method ◽

Copper Species ◽

Nh3 Scr ◽

Side Process ◽

Mcm 41

Aluminum containing silica spherical MCM-41 was synthesized and modified with copper by the template ion-exchange method (TIE) and its modified version, including treatment of the samples with ammonia solution directly after template ion-exchange (TIE-NH3). The obtained samples were characterized with respect to their chemical composition (ICP-OES), structure (XRD), texture (low temperature N2 sorption), morphology (SEM-EDS), form and aggregation of deposited copper species (UV-vis DRS), reducibility of copper species (H2-TPR), and surface acidity (NH3-TPD). The deposition of copper by the TIE-NH3 method resulted in much better dispersion of this metal on the MCM-41 surface comparing to copper introduced by TIE method. It was shown that such highly dispersed copper species, mainly monomeric Cu2+ cations, deposited on aluminum containing silica spheres of MCM-41, are significantly more catalytically effective in the NH3-SCR process than analogous catalysts containing aggregated copper oxide species. The catalysts obtained by the TIE-NH3 method effectively operated in much broader temperature and were less active in the side process of direct ammonia oxidation by oxygen.

Download Full-text

Modeling Species Inhibition of NO Oxidation in Urea-SCR Catalysts for Diesel Engine NOx Control

ASME 2010 Internal Combustion Engine Division Fall Technical Conference ◽

10.1115/icef2010-35054 ◽

2010 ◽

Author(s):

Maruthi Devarakonda ◽

Russell Tonkyn ◽

Diana Tran ◽

Jong Lee ◽

Darrell Herling

Keyword(s):

Low Temperature ◽

Kinetic Models ◽

Catalytic Reduction ◽

No Oxidation ◽

Dissociation Kinetics ◽

Scr Catalysts ◽

Fast Scr ◽

Standard Scr ◽

Heavy Duty Diesel ◽

Nox Control

Urea-selective catalytic reduction (SCR) catalysts are regarded as the leading NOx aftertreatment technology to meet the 2010 NOx emission standards for on-highway vehicles running on heavy-duty diesel engines. However, issues such as low NOx conversion at low temperature conditions still exist due to various factors, including incomplete urea thermolysis, inhibition of SCR reactions by hydrocarbons and H2O. We have observed a noticeable reduction in the standard SCR reaction efficiency at low temperature with increasing water content. We observed a similar effect when hydrocarbons are present in the stream. This effect is absent under fast SCR conditions where NO ∼ NO2 in the feed gas. As a first step in understanding the effects of such inhibition on SCR reaction steps, kinetic models that predict the inhibition behavior of H2O and hydrocarbons on NO oxidation are presented in the paper. A one-dimensional SCR model was developed based on conservation of species equations and was coded as a C-language S-function and implemented in Matlab/Simulink environment. NO oxidation and NO2 dissociation kinetics were defined as a function of the respective adsorbate’s storage in the SCR catalyst. The corresponding kinetic models were then validated on temperature ramp tests that showed good match with the test data.

Download Full-text

The Role of SO3 Poisoning in CU/SSZ-13 NH3-SCR Catalysts

Catalysts ◽

10.3390/catal9090741 ◽

2019 ◽

Vol 9 (9) ◽

pp. 741 ◽

Cited By ~ 1

Author(s):

Wang ◽

Hou ◽

Yan ◽

Zhang ◽

Wang ◽

...

Keyword(s):

Copper Sulfate ◽

Active Sites ◽

Catalytic Reduction ◽

Copper Ions ◽

Acid Resistance ◽

Temperature Program Reduction ◽

Copper Species ◽

Nh3 Scr ◽

Scr Catalysts

To reveal the role of SO3 poisoning in Cu/SSZ-13 NH3-SCR catalysts, fresh and sulfated Cu/SSZ-13 catalysts were prepared in the presence or absence of SO3 flux. The deactivation mechanism is probed by the changes of structural, copper species, and selective catalytic reduction (SCR) activity. The variations concentrate on the changes of copper species as the Chabazite (CHA) framework of Cu/SSZ-13 catalysts could keep intact at high ratios of SO3/SOx. The thermal gravimetric analyzer (TGA) results reveal that the copper sulfate formed during sulfation and the amounts of sulfate species increased with an increase in the SO3/SOx ratio. In contrast to the changing trend of copper sulfate, temperature program reduction (H2-TPR), and electron paramagnetic resonance (EPR) results manifest that, since the number of active copper ions declines with an increase of the SO3/SOx ratio, the active sites transform to these inactive species during sulfation. Due to the combination of NH3-SCR activity and the kinetic tests, it is shown that the decreased number of active sites is responsible for the declined SCR activity at low temperature. As Cu/SSZ-13 catalysts show excellent acid-resistance ability, our study reveals that the Cu/SSZ-13 catalyst is a good candidate for NOx elimination, especially when SO3 exists.

Download Full-text

Precursor Effect on Mn-Fe-Ce/TiO2 Catalysts for Selective Catalytic Reduction of NO with NH3 at Low Temperatures

Catalysts ◽

10.3390/catal11020259 ◽

2021 ◽

Vol 11 (2) ◽

pp. 259

Author(s):

Siva Sankar Reddy Putluru ◽

Leonhard Schill ◽

Anker Degn Jensen ◽

Bernard Siret ◽

Frank Tabaries ◽

...

Keyword(s):

Low Temperature ◽

Selective Catalytic Reduction ◽

Photoelectron Spectroscopy ◽

Catalytic Reduction ◽

Reduction Of No ◽

X Ray ◽

Nh3 Scr ◽

Fast Scr ◽

Oxide Phases ◽

Temperature Programmed

Preparation of Mn/TiO2, Mn-Fe/TiO2, and Mn-Fe-Ce/TiO2 by the deposition-precipitation (DP) method can afford very active catalysts for low-temperature NH3-SCR (selective catalytic reduction of NO with NH3). The effect of precursor choice (nitrate vs. acetate) of Mn, Fe, and Ce on the physiochemical properties including thermal stability and the resulting SCR activity were investigated. The resulting materials were characterized by N2-Physisorption, XRD (Powder X-ray diffraction), XPS (X-ray photoelectron spectroscopy), H2-TPR (temperature-programmed reduction with hydrogen), and the oxidation of NO to NO2 measured at 300 °C. Among all the prepared catalysts 5MnAce/Ti, 25Mn0.75AceFe0.25Nit/Ti, and 25Mn0.75AceFe0.20NitCe0.05Ace/Ti showed superior SCR activity at low temperature. The superior activity of the latter two materials is likely attributable to the presence of amorphous active metal oxide phases (manganese-, iron- and cerium-oxide) and the ease of the reduction of metal oxides on TiO2. Enhanced ability to convert NO to NO2, which can promote fast-SCR like pathways, could be another reason. Cerium was found to stabilize amorphous manganese oxide phases when exposed to high temperatures.

Download Full-text

Modeling Species Inhibition of NO Oxidation in Urea-SCR Catalysts for Diesel Engine NOx Control

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4002894 ◽

2011 ◽

Vol 133 (9) ◽

Cited By ~ 6

Author(s):

Maruthi Devarakonda ◽

Russell Tonkyn ◽

Diana Tran ◽

Jong Lee ◽

Darrell Herling

Keyword(s):

Low Temperature ◽

Kinetic Models ◽

Catalytic Reduction ◽

No Oxidation ◽

Particulate Filter ◽

Dissociation Kinetics ◽

Scr Catalysts ◽

Fast Scr ◽

Standard Scr ◽

Heavy Duty Diesel

Urea-selective catalytic reduction (SCR) catalysts are regarded as the leading NOx aftertreatment technology to meet the 2010 NOx emission standards for on-highway vehicles running on heavy duty diesel engines. However, issues such as low NOx conversion at low temperature conditions still exist due to various factors, including incomplete urea thermolysis, inhibition of SCR reactions by hydrocarbons, and H2O. We have observed a noticeable reduction in the standard SCR reaction efficiency at low temperature with increasing water content. We observed a similar effect when hydrocarbons are present in the stream. This effect is absent under fast SCR conditions where NO∼NO2 in the feed gas. As a first step in understanding the effects of such inhibition on SCR reaction steps, kinetic models that predict the inhibition behavior of H2O and hydrocarbons on NO oxidation are presented in the paper. A one-dimensional SCR model was developed based on the conservation of species equations and was coded as a C-language S-function and implemented in MATLAB/SIMULINK environment. NO oxidation and NO2 dissociation kinetics were defined as a function of the respective adsorbate’s storage in the Fe–zeolite SCR catalyst. The corresponding kinetic models were then validated on temperature ramp tests that showed good match with the test data. Such inhibition models will improve the accuracy of the model based control design for integrated diesel particulate filter-SCR aftertreatment systems.

Download Full-text

Enhanced Catalytic Performance of Hierarchical MnOx/ZSM-5 Catalyst for the Low-Temperature NH3-SCR

Catalysts ◽

10.3390/catal10030311 ◽

2020 ◽

Vol 10 (3) ◽

pp. 311 ◽

Cited By ~ 1

Author(s):

Jing Shao ◽

Shuyuan Cheng ◽

Zhaoxu Li ◽

Bichun Huang

Keyword(s):

Low Temperature ◽

Pore Structure ◽

Catalytic Reduction ◽

Surface Acidity ◽

Ammonium Hydroxide ◽

Catalytic Performance ◽

Nh3 Scr ◽

Hierarchical Pore Structure ◽

So2 Resistance ◽

Hierarchical Pore

A ZSM-5 zeolite with a hierarchical pore structure was synthesized by the desilication-recrystallization method using tetraethyl ammonium hydroxide (TEAOH) and cetyltrimethylammonium bromide (CTAB) as the desilication and structure-directing agents, respectively. The MnOx/ZSM-5 catalyst was synthesized by the ethanol dispersion method and applied for the low-temperature selective catalytic reduction of NOx with NH3. The results showed that NOx conversion of the hierarchical MnOx/ZSM-5 catalyst could reach 100% at about 120 °C and could be maintained in the temperature range of 120–240 °C with N2 selectivity over 90%. Furthermore, the hierarchical MnOx/ZSM-5catalyst presented better SO2 resistance performance than the traditional catalyst in the presence of 100 ppm SO2 at 120 °C. XRD, SEM, TEM, XPS, BET, NH3-TPD, and TG were applied to characterize the structural properties of the MnOx/ZSM-5 catalysts. These results showed that the MnOx/ZSM-5 catalyst had micropores (0.78 nm) and mesopores (3.2 nm) leading to a larger specific surface area, which improved the mass transfer of reactants and products while reducing the formation of sulfates. The better catalytic performance over hierarchical MnOx/ZSM-5 catalyst could be attributed to the higher concentration of Mn4+ and chemisorbed oxygen species and higher surface acidity. The improved SO2 resistance was related to the catalyst’s hierarchical pore structure.

Download Full-text

Insight into the Promoting Role of Er Modification on SO2 Resistance for NH3-SCR at Low Temperature over FeMn/TiO2 Catalysts

Catalysts ◽

10.3390/catal11050618 ◽

2021 ◽

Vol 11 (5) ◽

pp. 618

Author(s):

Huan Du ◽

Zhitao Han ◽

Xitian Wu ◽

Chenglong Li ◽

Yu Gao ◽

...

Keyword(s):

Low Temperature ◽

Catalyst Surface ◽

Impregnation Method ◽

In Situ Drifts ◽

Tio2 Catalyst ◽

Nh3 Scr ◽

Nh3 Adsorption ◽

So2 Resistance ◽

Fast Scr

Er-modified FeMn/TiO2 catalysts were prepared through the wet impregnation method, and their NH3-SCR activities were tested. The results showed that Er modification could obviously promote SO2 resistance of FeMn/TiO2 catalysts at a low temperature. The promoting effect and mechanism were explored in detail using various techniques, such as BET, XRD, H2-TPR, XPS, TG, and in-situ DRIFTS. The characterization results indicated that Er modification on FeMn/TiO2 catalysts could increase the Mn4+ concentration and surface chemisorbed labile oxygen ratio, which was favorable for NO oxidation to NO2, further accelerating low-temperature SCR activity through the “fast SCR” reaction. As fast SCR reaction could accelerate the consumption of adsorbed NH3 species, it would benefit to restrain the competitive adsorption of SO2 and limit the reaction between adsorbed SO2 and NH3 species. XPS results indicated that ammonium sulfates and Mn sulfates formed were found on Er-modified FeMn/TiO2 catalyst surface seemed much less than those on FeMn/TiO2 catalyst surface, suggested that Er modification was helpful for reducing the generation or deposition of sulfate salts on the catalyst surface. According to in-situ DRIFTS the results of, the presence of SO2 in feeding gas imposed a stronger impact on the NO adsorption than NH3 adsorption on Lewis acid sites of Er-modified FeMn/TiO2 catalysts, gradually making NH3-SCR reaction to proceed in E–R mechanism rather than L–H mechanism. DRIFTS.

Download Full-text