Catalytic Decomposition Of N2O Research Articles

Catalytic Decomposition of N2O and NO

As generally known, nitrogen oxides NOx (NO, NO2) and nitrous oxide (N2O) are significant pollutants [...]

A Review on the Catalytic Decomposition of NO by Perovskite-Type Oxides

Direct catalytic decomposition of NO has the advantages of being a simple process, producing no secondary pollution, and being good for the economy, which has attracted extensive research in recent years. Perovskite-type mixed oxides, with an ABO3 or A2BO4 structure, are promising materials as catalysts for NO decomposition due to their low cost, high thermal stability, and, of course, their good catalytic performances. In this review, the influence factors, such as A-site substitution, B-site substitution and reaction conditions on the catalytic performance of catalysts have been expounded. The reaction mechanisms of direct NO decomposition are also discussed. Finally, major conclusions are drawn and some research challenges are highlighted.

Cooperative effect of Pt single-atoms and nanoparticles supported on carbonaceous materials: Catalytic NO decomposition as a probe reaction

Activated carbon containing highly dispersed platinum (Pt/C with ca. 1 wt.%) catalyst was synthesized according to the simple sonochemistry route followed by a drying step in air at 130 °C. STEM-HAADF micrographs indicate the presence of Pt single atoms (SAs) homogeneously dispersed on the activated carbon. The catalytic decomposition of NO has been investigated on samples pre-reduced at 250 °C and 500 °C. The Pt SAs remain stable and exhibit a surprisingly high activity which does not reflect the usually observed structure-sensitivity of NO dissociation. In addition, remarkable catalyst stability is observed after reaction at 650 °C in the presence of water. On the other hand, pre-reduction at 500 °C induces a strong deactivation related to a coalescence process with the subsequent generation of large Pt clusters, despite some small metal nanoparticles are still present in the sample. Accordingly, the structure-sensitivity of this reaction is restored. All these observations have been rationalized through the examinations of various reaction mechanisms.

Investigation of Different Apatites-Supported Co3O4 as Catalysts for N2O Decomposition

Two types of apatite supports including hydroxyapatite (HAP) and fluorapatite (FAP) were prepared by the co-precipitation method. Supported Co catalysts with the above carriers were synthesized from Co(NO3)2·6H2O via the impregnation method. The catalytic activity for N2O decomposition was investigated using a continuous flowing microreactor system. The catalytic results demonstrated that the Co/HAP exhibited more excellent catalytic activity as well as the impurity gas (H2O, O2, and NO) resistance capability than the Co/FAP in the temperature range of 300–600 °C. Furthermore, the physicochemical properties of Co/HAP and Co/FAP were determined by several relevant characterization methods. The obtained experimental results revealed that Co/HAP possessed larger specific surface area, more ion-exchanged Co2+ and stronger oxygen desorption capacity than Co/FAP, which are the key factors for high N2O decomposition activity. Moreover, compared with Co/FAP, Co/HAP has not only more basic content, but also higher basic site density, which may be also conducive to enhance the electron donating ability of Co2+, thereby promoting the N2O catalytic decomposition.

Co/Hydroxyapatite catalysts for N2O catalytic decomposition: Design of well-defined active sites with geometrical and spacing effects

Different methods including ion exchange, impregnation and hydrothermal method were used to prepare Co/hydroxyapatite catalysts with various Co species. The catalytic activities for N2O decomposition were studied. It was concluded that Co2+ⅡOh existed in Co(1.2)-IE prepared by ion exchange is more active than Co2+Td, Co3+Oh and Co2+Ⅰ obtained by impregnation and hydrothermal methods, respectively. Meanwhile, Co(1.2)-IE shows better stability and stronger resistance against 2.0 vol.% O2 or 2.3 vol.% H2O in the feed gas. The higher catalytic activity of Co2+ⅡOh is attributed to its octahedral coordination geometrical structure, which make Co2+ⅡOh tend to donate electrons to activate N2O. Furthermore, the closer spacing distance between two Co2+ⅡOh sites can facilitate the combination and desorption of oxygen species. The above mentioned reasons ultimately lead to the increased catalytic activity. Finally, the results of density functional theory calculations indicate that the Co2+ⅡOh possesses the highest d-band center, which means the excellent catalytic activity.

Effect of Potassium Salt Types On The Performance of Cu-ZSM-5 For The Catalytic Decomposition of NO

Effect of Potassium Salt Types On The Performance of Cu-ZSM-5 For The Catalytic Decomposition of NO

Environmental Reactions of Air-Quality Protection on Eco-Friendly Iron-Based Catalysts

A series of iron functionalized hydroxyapatite (Fe/HAP) samples with different metal loading (2 < wt.% Fe < 13) was prepared by a flash ionic exchange procedure from iron(III) nitrate as precursor and tested in some environmental air-quality protection reactions such as the catalytic reduction of NOx by NH3 (NH3-SCR), catalytic oxidation of NH3 (NH3-SCO) and catalytic N2O decomposition. The catalytic performances of the Fe/HAP catalysts were determined under flow conditions as a function of temperature and using reactant concentrations typical of polluting gaseous emissions from industrial vents. Physico-chemical characterization with various techniques of study (UV-DR and Mössbauer spectroscopies, NH3 titration, N2-physisorption, and XRPD analyses) provided valuable information on Fe-speciation, acidity, morphology, and structure of the samples. In general, highly dispersed Fe3+ centers were the predominant species, irrespective of Fe-loading, while just low percentage (≤15%) of FexOy nanoclusters (2 < size/nm < 4) was detected on the samples. As expected, the differences in iron concentration produced a diversified effect of both catalyst properties and catalytic activity, comprising the conversion and selectivity profiles, different for each reaction considered. The obtained results indicate a good potentiality for the eco-friendly Fe-catalysts for some environmental reactions of air protection.

N2O decomposition properties of Ru catalysts supported on various oxide materials and SnO2

Nitrous oxide (N2O) is a stratospheric ozone depleting greenhouse gas that has global warming potential. As the catalytic decomposition of N2O is one of the most promising techniques for N2O emissions abatement, in this study, for this purpose the properties of Ru supported on various oxide materials were investigated under excess O2 conditions, and the identities of the N2O adsorption species on the catalysts were confirmed. To clarify the correlation between the catalytic properties and N2O decomposition activity, the supported Ru catalysts were characterised by means of powder X-ray diffraction, X-ray fluorescence measurements, energy-dispersive X-ray mapping and several gas sorption techniques. The results showed that the redox properties for Ru (RuO2) at low temperature are closely associated with N2O decomposition activity. The local structures, optimal Ru loading and N2O adsorption species of the novel Ru/SnO2 catalysts were studied and they showed high activity for N2O decomposition.

Cobalt Based Catalysts on Alkali-Activated Zeolite Foams for N2O Decomposition

In this work, we studied the effect of alkali-activated zeolite foams modifications on properties and catalytic activity of cobalt phases in the process of catalytic decomposition of N2O. The zeolite foam supports were prepared by alkali activation of natural zeolite followed by acid leaching and ion exchange. The cobalt catalysts were synthesised by a different deposition technique (direct ion exchange (DIE) and incipient wetness impregnation (IWI) method of cobalt on zeolite foams. For comparison, catalysts on selected supports were prepared and the properties of all were compared in catalytic tests in the pellet form and as crushed catalysts to determine the effect of internal diffusion. The catalysts and supports were in detail characterized by a variety of techniques. The catalyst activity strongly depended on the structure of support and synthesis procedure of a cobalt catalyst. Ion exchange method provided active phase with higher surface areas and sites with better reducibility, both of these factors contributed to higher N2O conversions of more than 80% at 450 °C. A large influence can also be attributed to the presence of alkali metals, in particular, potassium, which resulted in a modification of electronic and acid base properties of the cobalt oxide phase on the catalyst surface. The promotional effect of potassium is better reducibility of cobalt species.

Effects of support materials and Ir loading on catalytic N2O decomposition properties

N2O is a stratospheric ozone-depleting greenhouse gas with a global warming potential. The catalytic decomposition of N2O is one of the most promising and economical techniques to reduce the amount of the gas in the atmosphere. In the present study, the effects of support materials and Ir loading on the catalytic N2O decomposition properties were comprehensively investigated. The decomposition activity is closely associated with the Ir dispersion which is estimated using pulsed CO chemisorption. In addition, NO-TPD profiles and in situ FTIR spectra revealed a correlation between the adsorption properties of N2O/NOx and the catalytic N2O decomposition activity.

Nature of active Fe species and reaction mechanism over high-efficiency Fe/CHA catalysts in catalytic decomposition of N2O

Fe/CHA catalysts for N2O decomposition with various Fe loadings (Fe/SAPO-34 and Fe/SSZ-13) were synthesized by a solid-state ion exchange method. Under the same reaction conditions, obviously superior activities of Fe/CHA catalysts were observed in comparison with the current state-of-the-art Fe/zeolite, i.e., Fe/FER. Meanwhile, Fe/CHA catalysts exhibited a robust high-temperature hydrothermal stability. The characterization results and density functional theory (DFT) calculations indicated that the dispersion of Fe species over Fe/CHA catalysts was strongly influenced by the nature of the support, although SAPO-34 and SSZ-13 have similar morphology. Combined with the catalytic performance, dinuclear [HO–Fe–O–Fe–OH]2+ species were identified as the most active Fe species for Fe/CHA catalysts in the N2O decomposition reaction. Furthermore, the dimeric Fe species in SSZ-13 were more active than those in SAPO-34, due to lower Fe–O binding energies. Finally, DFT calculations provided a comprehensive understanding of the N2O decomposition mechanism over Fe/CHA catalysts.

Effect of Water Vapor on Catalytic Decomposition of NO over Cu–ZSM-5: A Mechanism and Kinetic Study

Cu–ZSM-5 has great potential for the direct catalytic decomposition of NO in flue gas. However, NO conversion is significantly inhibited in the presence of water vapor, and the mechanism for this i...

Direct catalytic decomposition of N2O over bismuth modified NiO catalysts

Direct catalytic decomposition is a promising technology to control the emission of nitrous oxide (N2O) during fossil fuel combustion and various chemical industries. In this study, a series of NiO catalysts modified with different metal oxides (MaNiOb) were prepared by the co-precipitation method and employed for the direct catalytic decomposition of N2O. Bismuth (Bi) species was confirmed to be the most optimal promoter and the Bi0.1NiO1.15 catalyst with a Bi/Ni molar ratio of 0.1 exhibited the best activity over the temperature range of 300−450 °C. The addition of Bi species also promoted the steam resistance capability of the NiO catalyst. Moreover, the physicochemical properties of pure and Bi-modified NiO catalysts were further determined by several characterization methods. The surface areas and capacity of oxygen adsorption/desorption over the catalyst were noticeably improved with the doping of Bi species. Besides, the presence of doped-Bi facilitated the creation of both Ni3+ and surface oxygen vacancies on NiO, which promoted the performance of N2O decomposition. Whereas, the excessive Bi species would accumulate to form large Bi2O3 grains, which diminished the surface areas and covered the active sites on the catalysts, leading to the rapid degradation of N2O catalytic decomposition.

Co3O4 supported on bone-derived hydroxyapatite as potential catalysts for N2O catalytic decomposition

Natural hydroxyapatite (nHAP) obtained from roasted pork bone was used as carrier of Co3O4 to prepare Co/nHAP catalyst for N2O catalytic decomposition. For the sake of contrast, the catalytic activity of Co3O4 supported on synthetic HAP (Co/HAP-Syn) and pure Co3O4 were also investigated. Activity tests indicate that the Co/nHAP could achieve higher catalytic activity than Co/HAP-Syn and pure Co3O4, even in impurity gases, as well as superior stability. The characterization results concluded that, compared with those on Co/HAP-Syn, the sizes of Co3O4 particles on Co/nHAP are smaller, which may contribute to enhance the quantity of active sites. More importantly, the existence of K, Na and Mg elements on the nHAP derived from bone can weaken the CoO bond and increase the amount of oxygen vacancies. All these factors could promote the catalytic activity as well as less inhibition affected by impurity gases. To the best of our knowledge, this is the first report on N2O catalytic decomposition making use of abandoned bones as effective support material, which can develop a sustainable and promising solution to the growing problem of environment.

A New Dynamic Approach for N2O Decomposition by Pre‐reduced Rh/CeZrOx Catalysts

AbstractThis study deals with the catalytic decomposition of N2O into harmless N2 and O2, in view of its potential application to decrease the pollution from internal combustion engines. The key of this work was to pre‐reduce a Rh/CeZrOx catalyst under a H2 based atmosphere, in order to enhance the amount of oxygen vacancies in the ceria‐based support. The results demonstrated that both, Rh species and oxygen vacancies of the ceria‐based support catalyze the N2O decomposition reaction. However, the presence of high concentrations of H2O and O2 strongly inhibited the catalytic activity. Nevertheless, small O2 concentrations maintained the performance. Therefore, the pre‐reduced Rh/CeZrOx could be potentially used for the reduction of N2O emitted by internal combustion engines working in stoichiometric conditions. In addition, a short injection of a reducing agent (e. g. H2) allowed to partially recover the initial catalytic activity of the system. All in all, this study proposes a new potential approach to mitigate the overall N2O greenhouse gas emissions.

Nytrox as “Drop-in” Replacement for Gaseous Oxygen in SmallSat Hybrid Propulsion Systems

A medical grade nitrous oxide (N2O) and gaseous oxygen (GOX) “Nytrox” blend is investigated as a volumetrically-efficient replacement for GOX in SmallSat-scale hybrid propulsion systems. Combined with 3-D printed acrylonitrile butadiene styrene (ABS), the propellants represent a significantly safer, but superior performing, alternative to environmentally-unsustainable spacecraft propellants like hydrazine. In a manner analogous to the creation of soda-water using dissolved carbon dioxide, Nytrox is created by bubbling GOX under pressure into N2O until the solution reaches saturation. Oxygen in the ullage dilutes N2O vapor and increases the required decomposition energy barrier by several orders of magnitude. Thus, risks associated with inadvertent thermal or catalytic N2O decomposition are virtually eliminated. Preliminary results of a test-and-evaluation campaign are reported. A small spacecraft thruster is first tested using gaseous oxygen and 3-D printed ABS as the baseline propellants. Tests were then repeated using Nytrox as a “drop-in” replacement for GOX. Parameters compared include ignition reliability, latency, initiation energy, thrust coefficient, characteristic velocity, specific impulse, combustion efficiency, and fuel regression rate. Tests demonstrate Nytrox as an effective replacement for GOX, exhibiting a slightly reduced specific impulse, but with significantly higher volumetric efficiency. Vacuum specific impulse exceeding 300 s is reported. Future research topics are recommended.

Effects of zirconia crystal phases on the catalytic decomposition of N2O over Co3O4/ZrO2 catalysts

Two ZrO2 supports with either monoclinic (m-ZrO2) or tetragonal (t-ZrO2) crystal phases were obtained under hydrothermal reaction conditions. ZrO2-supported Co3O4 catalysts (Co3O4/m-ZrO2 and Co3O4/t-ZrO2) were subsequently prepared through an impregnation-loading route. The effects of zirconia crystal phases on the catalytic decomposition of N2O over Co3O4/ZrO2 catalysts were investigated in the presence or absence of contaminants (O2/H2O/NO) in the feed gas. The catalytic results indicated that Co3O4/m-ZrO2 was more active than Co3O4/t-ZrO2 during N2O decomposition. ZrO2 supports and/or Co3O4/ZrO2 catalysts were characterized via multitudinous techniques to explore the relationships between the structures, catalytic activities, and active sites of samples. The experimental results confirmed that there were more Co oxides dispersed on m-ZrO2 than t-ZrO2, and Co3O4/m-ZrO2 had superior textural properties than Co3O4/t-ZrO2. Furthermore, Co3O4/m-ZrO2 possessed a relatively higher redox Co2+/Co3+ activity, more surface Co2+, and more surface oxygen vacancies than Co3O4/t-ZrO2 due to strong interactions between the m-ZrO2 support and active Co oxides. m-ZrO2 also contributed to the formation of stable Co2+. Moreover, the Co3O4/m-ZrO2 surface contained abundant basic sites that helped improve the electron-donating ability of Co2+ which further decreased the activation energy for N2O decomposition.

Catalytic Decomposition of N2O in Air Flows of Gas-Purification Systems in Radiochemical Industries

Catalytic Decomposition of N2O in Air Flows of Gas-Purification Systems in Radiochemical Industries

Catalytic decomposition of N2O on PdxCuy alloy catalysts: A density functional theory study

The density functional theory (DFT) calculations were performed to investigate the catalytic activities of Pd, Cu, and PdxCuy alloy catalysts for N2O reduction reaction (NRR). The activation and dissociation of N2O on PdxCuy catalysts were explored. The rate-determining step for the NRR was the dissociation of N2O into N2 and O. The electronic structure of PdxCuy alloys was determined by both ligand and strain effects, but was not closely related to the catalytic activity for NRR because two kinds of surface Pd and Cu atoms are differently involved in active sites for molecular adsorption and dissociation. Owing to the different role of Pd and Cu in NRR, the PdCu catalyst had both strong N2O adsorption strength and easier N2O dissociation than did pure and Pd3Cu catalysts, and therefore had the highest catalytic activity for NRR among the PdxCuy alloy catalysts. These fundamental findings were further applied to predict the thermal and electrochemical NRR.

Preparation and evaluation of iron nanoparticles embedded CNTs grown on ZSM-5 as catalysts for NO decomposition

Due to their high activity and selectivity, single-atoms based catalysts for oxygen removal and wastewater treatment have received enormous attentions in academia and industry. The present work sought to extend the single-atom catalyst concept to NO decomposition. A series of catalysts with highly dispersed iron nanoparticles embedded in carbon nanotubes grown on a ZSM-5 zeolite were prepared using an induced growth method, by pyrolysing melamine and ferric nitrate precursors impregnated on ZSM-5 at 900 °C. The catalysts were then tested for their catalytic activity in NO decomposition using a fixed-bed reactor operating at 300 °C and were shown to be able to completely decompose NO under the test conditions. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), BET, Raman and temperature-programmed oxidation (TPO) were used to study the effects of molar ratio of ferric nitrate to melamine on the active species, sample structures and NO decomposition mechanism. An increase in the molar ratio of melamine to iron nitrate led to an improvement to the dispersibility of iron nanoparticles and enhancement of NO decomposition. The use of ZSM-5 increased the dispersion of iron, thus enhancing the catalytic decomposition of NO. The characterisation of the used catalysts revealed that it was possible to regenerate the catalytic activity by doping and pyrolysing the deactivated catalysts with melamine, with no significant difference to that of the fresh catalysts.