Special Issue "Catalytic Decomposition of N2O and NO"

A special issue of Catalysts (ISSN 2073-4344). This special issue belongs to the section "Environmental Catalysis".

Deadline for manuscript submissions: 31 December 2020.

Special Issue Editor

Prof. Dr. Lucie Obalová
Website SciProfiles
Guest Editor
Institute of Environmental Technology, VŠB – Technical University of Ostrava, 17. listopadu 15, 708 33 Ostrava, Czech Republic
Interests: Chemical and reactor engineering, Environmental catalysis and photocatalysis, Adsorption on solids, Kinetics and mechanisms of chemical reaction, Abatement of N2O and NOx from waste gases

Special Issue Information

Dear Colleagues,

Nitrogen oxides NOx (NO, NO2) and N2O are significant pollutants and more than 90% of emitted NOx from stationary sources is NO. Various techniques have been developed for NO elimination, such as commercially commonly used selective catalytic reduction of NOx (SCR) and selective noncatalytic reduction of NOx (SNCR). In particular, less efficient SNCR technology will no longer be appropriate due to the tightening of emission limits. Compared to that, SCR NOx technology is very effective, but its disadvantage, like that of SNCR, is the need to add a reducing agent (ammonia, urea), which increases costs, causes undesirable ammonia slip, and requires increased safety precautions. From this perspective, the direct catalytic decomposition of NO without a reducing agent is a challenge. Mixed oxides with alkaline metal promoters appear to be active for this reaction, but there are a number of issues that need to be addressed. These are the stability of catalysts, sufficient activity at industrially suitable temperatures, and suppression of inhibition of the reaction by oxygen and other components present in the waste gases.

Well known greenhouse gas N2O is emitted from some processes together with NOx. Even in this case, a direct catalytic decomposition is the elegant method for reducing its emissions. This technology is now at the stage of its first commercial applications, for example, in nitric acid plants. However, there is still space for increasing its efficiency through the modification of the active site, deposition of the active phase on suitable support, etc.

Another issue is an indoor and outdoor environment, where nitrogen oxides can be decomposed in the presence of suitable semiconductor materials and light with appropriate wavelength and intensity. Research findings focusing on the fundamental exploration of the syntheses, characterizations, and applications of various types of catalysts for N2O or NO catalytic or photocatalytic decomposition, as well as new knowledge about the mechanism and industrial-scale development of catalysts are of prime importance to this Special Issue.

Prof. Dr. Lucie Obalová
Guest Editor

Manuscript Submission Information

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Keywords

  • Direct NO catalytic decomposition
  • N2O catalytic decomposition
  • Photocatalytic decomposition of nitrogen oxides
  • Semiconductor photocatalysts, TiO2
  • Mixed oxide catalysts
  • Supported catalysts
  • Effect of promoters
  • Zeolites
  • Relation between methods of preparation, physicochemical and catalytic properties
  • Reaction mechanism and kinetics

Published Papers (7 papers)

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Research

Open AccessArticle
Two-Stage Catalytic Abatement of N2O Emission in Nitric Acid Plants
Catalysts 2020, 10(9), 987; https://doi.org/10.3390/catal10090987 - 01 Sep 2020
Abstract
Different variants for abatement of N2O emission from nitric acid plants with the use of catalysts developed at Łukasiewicz-INS were analyzed. Activity tests on a pilot scale confirmed the high activity of the studied catalysts. A two-stage catalytic abatement of N [...] Read more.
Different variants for abatement of N2O emission from nitric acid plants with the use of catalysts developed at Łukasiewicz-INS were analyzed. Activity tests on a pilot scale confirmed the high activity of the studied catalysts. A two-stage catalytic abatement of N2O emission in nitric acid plants was proposed: by high-temperature decomposition in the nitrous gases stream (HT-deN2O) and low-temperature decomposition in the tail gas stream (LT-deN2O). The selection of the optimal variant for abatement of N2O emission depends on the individual characteristics of the nitric acid plant: ammonia oxidation parameters, construction of ammonia oxidation reactor and temperature of the tail gas upstream of the expansion turbine. It was shown that the combination of both deN2O technologies, taking into account their technological constraints (dimensions of the catalyst bed), allows for a greater abatement of N2O emission, than the use of only one technology. This solution may be economically advantageous regarding the high prices of CO2 emission allowances. Full article
(This article belongs to the Special Issue Catalytic Decomposition of N2O and NO)
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Open AccessFeature PaperArticle
Magnesium Effect in K/Co-Mg-Mn-Al Mixed Oxide Catalyst for Direct NO Decomposition
Catalysts 2020, 10(8), 931; https://doi.org/10.3390/catal10080931 - 13 Aug 2020
Abstract
Emission of nitric oxide represents a serious environmental problem since it contributes to the formation of acid rain and photochemical smog. Potassium-modified Co-Mn-Al mixed oxide is an effective catalyst for NO decomposition. However, there are problems related to the thermal instability of potassium [...] Read more.
Emission of nitric oxide represents a serious environmental problem since it contributes to the formation of acid rain and photochemical smog. Potassium-modified Co-Mn-Al mixed oxide is an effective catalyst for NO decomposition. However, there are problems related to the thermal instability of potassium species and a high content of toxic and expensive cobalt. The reported research aimed to determine whether these shortcomings can be overcome by replacing cobalt with magnesium. Therefore, a series of Co-Mg-Mn-Al mixed oxides with different Co/Mg molar ratio and promoted by various content of potassium was investigated. The catalysts were thoroughly characterized by atomic absorption spectroscopy (AAS), temperature-programmed reduction by hydrogen (TPR-H2), temperature-programmed desorption of CO2 (TPD-CO2), X-ray powder diffraction (XRD), N2 physisorption, species-resolved thermal alkali desorption (SR-TAD), and tested in direct NO decomposition with and without the addition of oxygen and water vapor. Partial substitution of magnesium for cobalt did not cause an activity decrease when the optimal molar ratio of K/Co on the normalized surface area was maintained; it means that the portion of expensive and toxic cobalt can be successfully replaced by magnesium without any decrease in catalytic activity. Full article
(This article belongs to the Special Issue Catalytic Decomposition of N2O and NO)
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Open AccessFeature PaperArticle
Direct Decomposition of NO over Co-Mn-Al Mixed Oxides: Effect of Ce and/or K Promoters
Catalysts 2020, 10(7), 808; https://doi.org/10.3390/catal10070808 - 20 Jul 2020
Abstract
Co-Mn-Al mixed oxides promoted by potassium are known as active catalysts for the direct decomposition of nitric oxide (NO). In this study, the answer to the following question has been considered: does the presence of cerium in K-promoted Co-Mn-Al catalysts substantially affect the [...] Read more.
Co-Mn-Al mixed oxides promoted by potassium are known as active catalysts for the direct decomposition of nitric oxide (NO). In this study, the answer to the following question has been considered: does the presence of cerium in K-promoted Co-Mn-Al catalysts substantially affect the physical-chemical properties, activity, and stability in direct NO decomposition? The Co-Mn-Al, Co-Mn-Al-Ce, and Co-Mn-Al-Ce-K mixed oxide catalysts were prepared by the precipitation of corresponding metal nitrates with a solution of Na2CO3/NaOH, followed by the washing of the precipitate and calcination. Two other catalysts were prepared by impregnation of the Ce-containing catalysts with Co and Co+K nitrates. After calcination, the solids were characterized by chemical analysis, XRD, N2 physisorption, FTIR, temperature-programmed reduction, CO2 and O2 desorption (H2-TPR, CO2-TPD, O2-TPD), and X-ray photoelectron spectrometry (XPS). Cerium and especially potassium occurring in the catalysts affected the basicity, reducibility, and surface concentration of active components. Adding cerium itself did not contribute to the increase in catalytic activity, whereas the addition of cerium and potassium did. Catalytic activity in direct NO decomposition depended on combinations of both reducibility and the amount of stronger basic sites determined in the catalysts. Therefore, the increase in cobalt concentration itself in the Co-Mn-Al mixed oxide catalyst does not determine the achievement of high catalytic activity in direct NO decomposition. Full article
(This article belongs to the Special Issue Catalytic Decomposition of N2O and NO)
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Open AccessArticle
Contrasting Effects of Potassium Addition on M3O4 (M = Co, Fe, and Mn) Oxides during Direct NO Decomposition Catalysis
Catalysts 2020, 10(5), 561; https://doi.org/10.3390/catal10050561 - 19 May 2020
Cited by 1
Abstract
While the promotional effect of potassium on Co3O4 NO decomposition catalytic performance is established in the literature, it remains unknown if K is also a promoter of NO decomposition over similar simple first-row transition metal spinels like Mn3O [...] Read more.
While the promotional effect of potassium on Co3O4 NO decomposition catalytic performance is established in the literature, it remains unknown if K is also a promoter of NO decomposition over similar simple first-row transition metal spinels like Mn3O4 and Fe3O4. Thus, potassium was impregnated (0.9–3.0 wt.%) on Co3O4, Mn3O4, and Fe3O4 and evaluated for NO decomposition reactivity from 400–650 °C. The activity of Co3O4 was strongly dependent on the amount of potassium present, with a maximum of ~0.18 [(µmol NO to N2) g−1 s−1] at 0.9 wt.% K. Without potassium, Fe3O4 exhibited deactivation with time-on-stream due to a non-catalytic chemical reaction with NO forming α-Fe2O3 (hematite), which is inactive for NO decomposition. Potassium addition led to some stabilization of Fe3O4, however, γ-Fe2O3 (maghemite) and a potassium–iron mixed oxide were also formed, and catalytic activity was only observed at 650 °C and was ~50× lower than 0.9 wt.% K on Co3O4. The addition of K to Mn3O4 led to formation of potassium–manganese mixed oxide phases, which became more prevalent after reaction and were nearly inactive for NO decomposition. Characterization of fresh and spent catalysts by scanning electron microscopy and energy dispersive X-ray analysis (SEM/EDX), in situ NO adsorption Fourier transform infrared spectroscopy, temperature programmed desorption techniques, X-ray powder diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) revealed the unique potassium promotion of Co3O4 for NO decomposition arises not only from modification of the interaction of the catalyst surface with NOx (increased potassium-nitrite formation), but also from an improved ability to desorb oxygen as product O2 while maintaining the integrity and purity of the spinel phase. Full article
(This article belongs to the Special Issue Catalytic Decomposition of N2O and NO)
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Open AccessArticle
Atomic-Level Dispersion of Bismuth over Co3O4 Nanocrystals—Outstanding Promotional Effect in Catalytic DeN2O
Catalysts 2020, 10(3), 351; https://doi.org/10.3390/catal10030351 - 22 Mar 2020
Abstract
A series of cobalt spinel catalysts doped with bismuth in a broad range of 0–15.4 wt % was prepared by the co-precipitation method. The catalysts were thoroughly characterized by several physicochemical methods (X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), Raman spectroscopy (µRS), X-ray [...] Read more.
A series of cobalt spinel catalysts doped with bismuth in a broad range of 0–15.4 wt % was prepared by the co-precipitation method. The catalysts were thoroughly characterized by several physicochemical methods (X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), Raman spectroscopy (µRS), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption analyzed with Brunaer-Emmett-Teller theory (N2-BET), work function measurements (WF)), as well as aberration-corrected scanning transmission electron microscopy (STEM) coupled with energy-dispersive X-ray spectroscopy (EDX) and electron energy-loss spectroscopy (EELS). The optimal bismuth promoter content was found to be 6.6 wt %, which remarkably enhanced the performance of the cobalt spinel catalyst, shifting the N2O decomposition (deN2O) temperature window (T50%) down from approximately 400 °C (for Co3O4) to 240 °C (for the 6.6 wt % Bi-Co3O4 catalyst). The high-resolution STEM images revealed that the high activity of the 6.6 wt % Bi-Co3O4 catalyst can be associated with an even, atomic-level dispersion (3.5 at. nm−2) of bismuth over the surface of cobalt spinel nanocrystals. The improvement in catalytic activity was accompanied by an observed increase in the work function. We concluded that Bi promoted mostly the oxygen recombination step of a deN2O reaction, thus demonstrating for the first time the key role of the atomic-level dispersion of a surface promoter in deN2O reactions. Full article
(This article belongs to the Special Issue Catalytic Decomposition of N2O and NO)
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Open AccessArticle
Bulk, Surface and Interface Promotion of Co3O4 for the Low-Temperature N2O Decomposition Catalysis
Catalysts 2020, 10(1), 41; https://doi.org/10.3390/catal10010041 - 30 Dec 2019
Cited by 4
Abstract
Nanocrystalline cobalt spinel has been recognized as a very active catalytic material for N2O decomposition. Its catalytic performance can be substantially modified by proper doping with alien cations with precise control of their loading and location (spinel surface, bulk, and spinel-dopant [...] Read more.
Nanocrystalline cobalt spinel has been recognized as a very active catalytic material for N2O decomposition. Its catalytic performance can be substantially modified by proper doping with alien cations with precise control of their loading and location (spinel surface, bulk, and spinel-dopant interface). Various doping scenarios for a rational design of the optimal catalyst for low-temperature N2O decomposition are analyzed in detail and the key reactivity descriptors are identified (content and topological localization of dopants, their redox vs. non-redox nature and catalyst work function). The obtained results are discussed in the broader context of the available literature data to establish general guidelines for the rational design of the N2O decomposition catalyst based on a cobalt spinel platform. Full article
(This article belongs to the Special Issue Catalytic Decomposition of N2O and NO)
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Open AccessArticle
Photocatalytic Decomposition of N2O by Using Nanostructured Graphitic Carbon Nitride/Zinc Oxide Photocatalysts Immobilized on Foam
Catalysts 2019, 9(9), 735; https://doi.org/10.3390/catal9090735 - 30 Aug 2019
Cited by 2
Abstract
The aim of this work was to deposit cost-effective g-C3N4/ZnO nanocomposite photocatalysts (weight ratios of g-C3N4:ZnO from 0.05:1 to 3:1) as well as pure ZnO and g-C3N4 on Al2O3 [...] Read more.
The aim of this work was to deposit cost-effective g-C3N4/ZnO nanocomposite photocatalysts (weight ratios of g-C3N4:ZnO from 0.05:1 to 3:1) as well as pure ZnO and g-C3N4 on Al2O3 foam and to study their photocatalytic efficiency for the photocatalytic decomposition of N2O, which was studied in a home-made batch photoreactor under ultraviolet A irradiation (λ = 365 nm). Based on the photocatalysis measurements, it was found that photocatalytic decomposition of N2O in the presence of all the prepared samples was significantly higher in comparison with photolysis. The photoactivity of the investigated nanocomposite photocatalysts increased in the following order: g-C3N4/ZnO (3:1) ≈ g-C3N4/ZnO (0.45:1) ≤ g-C3N4/ZnO (2:1) ZnO < g-C3N4 < g-C3N4/ZnO (0.05:1). The g-C3N4/ZnO (0.05:1) nanocomposite showed the best photocatalytic behavior and the most effective separation of photoinduced electron–hole pairs from all nanocomposites. The key roles played in photocatalytic activity were the electron–hole separation and the position and potential of the valence and conduction band. On the other hand, the specific surface area and band gap energy were not the significant factors in N2O photocatalytic decomposition. Immobilization of the photocatalyst on the foam permits facile manipulation after photocatalytic reaction and their repeated application. Full article
(This article belongs to the Special Issue Catalytic Decomposition of N2O and NO)
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: Magnesium effect in K/Co-Mg-Mn-Al mixed oxide catalyst for direct NO decomposition
Authors: K. Karásková, K. Pacultová, A. Klegová, D. Fridrichová, T. Kiška, K. Jirátová, L. Obalová
Abstract:Alkali metal promoted Co-Mn-Al mixed oxide catalysts were tested for direct NO decomposition. In this study, the effect of Mg partly substituting Co in the Co4MnAlOx mixed oxide catalyst subsequently modified by different potassium amount, maintaining (CoxMgy)/Mn/Al molar ratio constant, was studied. Prepared catalysts were characterized by XRD, BET, TPR-H2, TPD-CO2 and tested for direct NO decomposition in inert gas and in the presence of oxygen.

 

Title: Bulk and surface promotion of Co3O4 nanocrystals as a sensible tool for controlling the catalytic N2O decomposition
Authors: S. Wójcik, G. Grzybek, P. Stelmachowski, Z. Sojka, A. Kotarba
Abstract: Cobalt spinel nanocrystals, even in their bare state, have been recognized as a very active catalytic material for N2O decomposition. Their catalytic performance can be substantially modified by controlling the faceting of the nanocrystals and/or by proper doping with alien cations. These may located either in the bulk of the catalyst or on its surface. A particular attention is placed on the role of the tetra and octahedral interstitials, and the impact of the surface promoters as a potential hosting sites for the dopants. Both doping scenarios are analyzed in detail in the context of a rational design of the optimal active phase for an efficient low temperature N2O decomposition. The obtained experimental results are discussed in the broader context of the available literature data to establish the state-of-the-art of N2O decomposition over cobalt spinel catalysts.

 

Title: Atomic-level dispersion of bismuth over Co3O4 nanocrystals – outstanding promotional effect in catalytic deN2O
Authors: S. Wójcik1, T. Thersleff2*, K. Gębska1, G. Grzybek1, A. Kotarba1
Affiliation: 1Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387 Krakow, Poland 2Department of Materials and Environmental Chemistry, Stockholm University, Svante Arrhenius & friends 16C 114 18 Stockholm, Sweden
Abstract: A series of cobalt spinel catalysts doped with bismuth in a broad range of 0 – 12 wt. % was prepared by the co-precipitation method. Catalysts were thoroughly characterized by several physicochemical methods (XRF, XRD, µRS, XPS, BET, WF), while the emphasis was put on the high resolution transmission electron microscopy (STEM, HAADF) coupled with EDX and EELS spectroscopies. The optimal concertation of the bismuth promoter was found to be 0.08 at.% (7.2 wt.%), which remarkably enhanced the performance of Co3O4, shifting down the deN2O temperature window by spectacular ΔT≈160°C. Since the addition of Bi results in work function increase, it is suggested that Bi promotes mostly the oxygen recombination step of the deN2O reaction. Microscopic observations allowed for revealing that the high activity of Bi-Co3O4 catalyst is associated with an even, atomic-level dispersion of bismuth promoter over the surface of cobalt spinel nanocrystals. The key role of atomic-level dispersion of the surface promoter in deN2O is pointed out for the first time.

Title: Direct Decomposition of NO over Co-Mn-Al mixed oxides: effect of Ce or Ce, K promotErs
Authors: Květa Jirátová, Kateřina Pacultová, Kateřina Karásková, Jana Balabánová, Martin Koštejn, and Lucie Obalová
Affiliation: Institute of Chemical Process Fundamentals of the CAS, v.v.i., 165 02 Praha 6, Rozvojová 135, Czech Republic
Abstract: Co–Mn–Al mixed oxides promoted by potassium are known as active catalysts for direct decomposition of nitric oxide (NO). In this study, answer to the following question have been searched: Does presence of cerium in the K-promoted Co–Mn–Al catalysts affect substantially physical-chemical properties, activity, and stability in direct NO decomposition? The Co–Mn–Al, Co-Mn-Al-Ce and Co-Mn-Al-Ce-K mixed oxide catalysts were prepared by the precipitation of corresponding metal nitrates with a solution of Na2CO3/NaOH, followed by the washing of the precipitate, and calcination. Two other catalysts were prepared by impregnation of the Ce-containing catalysts with Co and Co+K nitrates. After calcination, the solids were characterized by chemical analysis, XRD, N2 physisorption, FTIR, temperature programmed reduction, CO2 and O2 desorption (H2-TPR, CO2-TPD, O2-TPD), and X-ray photoelectron spectrometry (XPS). Cerium and especially potassium occurring in the catalysts affected basicity, reducibility, and surface concentration of active components. Adding cerium itself did not contribute to the increase of catalytic activity, whereas adding of cerium and potassium did. Catalytic activity in direct NO decomposition depended on combinations of both reducibility and the amount of stronger basic sites determined in the catalysts. Therefore, the increase of cobalt concentration itself in the Co-Mn-Al mixed oxide catalyst is not determining for achievement of high catalytic activity in direct NO decomposition.

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