Catalytic Decomposition Of Nitrous Oxide Research Articles

Effect of ammonia addition on the dispersion and activity of supported copper species on porous silica–alumina hollow spheres for catalytic decomposition of nitrous oxide

In this work, we investigated the influence of ammonia addition in the immersion process of active species on the dispersion and activity of copper-supported porous hollow silica–alumina sphere catalysts for the decomposition of nitrous oxide.

Influence of Co3O4-based catalysts on N2O catalytic decomposition and NO conversion.

This study investigated the effect of different Co3O4-based catalysts on the catalytic decomposition of nitrous oxide (N2O) and on nitric oxide (NO) conversion. The experiments were carried out using various reaction temperatures, alkaline solutions, pH, mixing conditions, aging times, space velocities, impregnation loads, and compounds. The results showed that Co3O4 catalysts prepared by precipitation methods have the highest catalytic activity and N2O conversion, even at low reaction temperatures, while the commercial nano and powder forms of Co3O4 (CS) have the lowest performance. The catalysts become inactive at temperatures below 400°C, and their activity is strongly influenced by the mixing temperature. Samples without stirring during the aging process have higher catalytic activity than those with stirring, even at low reaction temperatures (200-300°C). The catalytic activity of Co3O4 PM1 decreases with low W/F values and low reaction temperatures. Additionally, the catalyst's performance tends to increase with the reduction process. The study suggests that cobalt-oxide-based catalysts are effective in N2O catalytic decomposition and NO conversion. The findings may be useful in the design and optimization of catalytic systems for N2O and NO control. The results obtained provide important insights into the development of highly efficient, low-cost, and sustainable catalysts for environmental protection.

Ability of Shirasu‐based Material for Adsorption of Metal Ions and Its Promotion for Catalytic Decomposition of Nitrous Oxide

AbstractThis work investigated ability of Shirasu‐based material for adsorption of metal ions and their promotion effect for catalytic decomposition of nitrous oxide. Catalytically active cobalt and copper species were adsorbed on the Shirasu‐based material by immerse process of aqueous matal solutions. In all the Co/Cu ratios (Co/(Co+Cu)=1, 0.75, and 0.5), cobalt species were preferentially adsorbed on the Shirasu‐based material. The cobalt species tended to be adsorbed on the silica sites of the sample with Co/(Co+Cu)=0.75. and the catalyst exhibited the highest activity for decomposition of nitrous oxide. Introduced nitrous oxide was completely decomposed at the reaction temperatures above 673 K.

N2O Adsorption and Photochemistry on Ceria Surfaces

Catalytic decomposition of nitrous oxide (N2O) is one of the most promising ways to control N2O emissions, the dominant ozone-depleting substance and the third most potent greenhouse gas. We have investigated the adsorption and photoinduced decomposition of N2O on macroscopic monocrystalline CeO2(111) surfaces by polarization-dependent infrared reflection absorption spectroscopy (IRRAS) in conjunction with core-level (XPS Ce 3d and NEXAFS) and valence band (Ce 4f) spectroscopy as well as DFT+U calculations. The IRRAS results at 110 K show that the νas(NNO) asymmetric stretching vibration of adsorbed N2O exhibits band splitting at relatively low N2O coverage in p-polarized spectra. This band splitting is attributed to polarization-dependent shifts of absorption bands. On reduced ceria (111) surfaces, the desorption energy (0.37 eV) of N2O extracted by IRRAS is found to be higher than on oxidized surfaces. This increasing binding energy is attributed to the attractive coupling with Ce3+ cations formed via surface Ce4+ reduction by by polarons that migrate from the bulk. The photoreaction cross section (with ultraviolet (UV) light = 365 nm at T = 120 K) of the reduced ceria (110) surfaces determined by IRRAS (5 × 10–19 cm2) confirms their much higher activity than that of the reduced CeO2(111).

Fabrication of copper supported porous silica–alumina hollow spheres for catalytic decomposition of nitrous oxide

Copper supported porous silica–alumina hollow sphere catalysts were prepared using surfactant micelles to control the size distribution of interparticle spaces in the hollow sphere shells.

The investigation of the efficient replaceable microreactor into the catalytic decomposition of N2O over Pd/anodic γ-Al2O3 /Al

A novel replaceable microreactor was designed to investigate the catalytic decomposition of nitrous oxide. The replaceable microchannel plate was coated using 1wt.% Pd/anodic γ-Al2O3. The anodization method was adopted to prepare the anodic γ-Al2O3 on the aluminum microchannel plate. Palladium was loaded on anodic γ-Al2O3 support by wet impregnation technique. The morphology, thickness, structure, reduction behavior, surface area, and the catalytic performance of the catalyst were characterized via field emission scanning electron microscope (FE-SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD), transmission electron microscopy (TEM), H2 temperature-programmed reduction (H2-TPR) and Brunauer-Emmett-Teller (BET) surface area analysis. The performance of the prepared catalyst into the replaceable microreactor was experimentally investigated through nitrous oxide decomposition reaction in the temperature range of 280-340 °C and various GHSV of 1000, 2000, and 3000 mL h−1 gcat−1. Complete conversion of N2O decomposition was achieved at the temperature of 340∘C, atmospheric pressure, and a GHSV of 1000 mL h−1gcat−1. The results indicated that Pd/anodic γ-Al2O3 catalyst is promising to eliminate the dangerous emissions of nitrous oxide greenhouse gas in the chemical industry via direct catalytic decomposition. Furthermore, the proposed elliptical replaceable microreactor is effective for complete N2O decomposition as it requires lower amounts of catalyst and energy compared to the other conventional reactors.

Coordination and activation of nitrous oxide by iron zeolites

Iron-containing zeolites are heterogeneous catalysts that exhibit remarkable activity in the selective oxidation of inert hydrocarbons and catalytic decomposition of nitrous oxide (N2O). The reduction of N2O is critical to both these functions, but experimental data tracking the iron active sites during N2O binding and activation are limited. Here, the N2O-ligated Fe(ii) active site in iron-exchanged zeolite beta is isolated and characterized by variable-temperature Mössbauer, diffuse reflectance UV-vis-NIR and Fourier transform infrared spectroscopy. N2O binds through the terminal nitrogen atom with substantial backbonding from the Fe(ii) centre at low temperature. At higher temperatures, the Fe–N2O interaction is weakened, facilitating isomerization to the O-bound form, which is competent in O-atom transfer. Density functional theory calculations show the geometric and electronic structure requirements for N2O binding and activation. A geometric distortion imposed by the zeolite lattice plays an important role in activating N2O. This highlights a mechanism for structural control over function in Fe-zeolite catalysts.

The catalytic decomposition of nitrous oxide and the NO + CO reaction over Ni/Cu dilute and single atom alloy surfaces: first-principles microkinetic modelling

Density functional theory calculations and microkinetic modelling reveal that well-engineered Ni/Cu dilute alloys are promising for the catalytic reduction of NO by CO.

Catalytic Decomposition of Nitrous Oxide for Use in Hybrid Rocket Motors

In recent years, there has been significantly increased interest in using nitrous oxide as an oxidizer in hybrid rocket motor systems. The attraction of nitrous oxide is its low relative toxicity and high vapor pressure, potentially enabling self-pressurizing systems. Its decomposition is highly exothermic with a large energy barrier, typically requiring high temperature (700°C) to achieve appreciable decomposition rates. One solution is to use a catalyst to enable decomposition at significantly lower temperatures. This Paper uses a commercially available rhodium-based catalyst in a custom test cell to decompose nitrous oxide at temperatures well below the uncatalyzed self-sustaining decomposition temperature. This Paper also demonstrates that decomposition using the tested catalyst is direct to and at all temperature ranges observed and is incomplete with residual present at lower temperatures. Further, this Paper couples our test cell with a counterflow burner to ignite and burn hydroxyl-terminated polybutadiene fuel with the decomposed nitrous oxide and evaluate performance via fuel regression rate at a variety of conditions. The fuel autoignites when the gas exit temperature reaches 750°C, and regression rate is shown to increase with both mass flux and temperature.

Hydrothermal microwave‐assisted synthesis of LaFeO3 catalyst for N2O decomposition

AbstractLanthanum orthoferrite powders were synthesized via one‐step hydrothermal reactions under mild conditions using microwave and conventional heating. The use of microwave irradiation during the synthesis allows one to obtain nanocrystalline LaFeO3 with a higher yield and reduced crystallite and particle size within a 16 times shorter duration (3 hours) at a lower temperature of 220°C as compared to the conventional heating. The catalytic decomposition of nitrous oxide was performed over both samples, it was shown that the sample obtained under microwave conditions demonstrates enhanced activity as a catalyst: N2O decomposes completely at 700°C over the catalyst formed at microwave conditions, while the comparative catalyst prepared by conventional heating reaches a lower conversion of only 60% at the same temperature and catalytic reaction conditions.

Fabrication of Hollow Spheres of Copper-Cerium Composite Oxide for Catalytic Decomposition of Nitrous Oxide

Fabrication of Hollow Spheres of Copper-Cerium Composite Oxide for Catalytic Decomposition of Nitrous Oxide

Fabrication of copper supported on hollow silica–alumina composite spheres for catalytic decomposition of nitrous oxide

In this work, we fabricated copper supported on hollow silica–alumina composite spheres for catalytic decomposition of nitrous oxide. The copper supported on the hollow spheres was obtained by impregnation of the active copper species on the hollow silica–alumina composite sphere support prepared by the template method using spherical polystyrene particles. The supported copper catalysts on the hollow spheres showed higher conversion of nitrous oxide than supported copper catalyst on fine silica–alumina composite particles. The catalyst activity was significantly improved by adjusting impregnation temperature, and the supported copper catalyst impregnated at 353 K exhibits around 75% of nitrous oxide conversion at 573 K. The results of the DR UV–Vis spectra, the EDX analysis, and nitrogen adsorption measurement indicate that the highly active catalyst consisted of high ratio of isolated copper ions inside the shell of the hollow spheres.

Preparation of LaNiO3 perovskite by oxalate and carbonate precursor method for utilization as catalyst for high-temperature decomposition of N2O

The mixed oxide LaNiO3 with perovskite structure was prepared by two relatively new and unconventional methods including preparation and thermal decomposition of mixed metal oxalate or carbonate precursors. The intermediates were prepared by reaction in a highly concentrated suspension (paste). The thermal decomposition conditions of these intermediates were described, and the final calcination temperatures were determined, which were done using thermal analysis methods and X-ray diffraction. During the decomposition of mixed carbonates, one-phase LaNiO3 is produced directly, and in case of decomposition of oxalates, a mixture of LaNiO3 and La2O3 is produced due to the formation of La2O2CO3 during the heating. Catalytic decomposition of nitrous oxide at high temperature (650–930 °C) and high loading (GHSV = 350,000 h−1) has shown high LaNiO3 activity, even at lower temperatures. The results were compared with the same compound obtained by co-precipitation and by solid-state reaction. Methods of preparation based on decomposition of oxalate and carbonate intermediates lead to the preparation of materials with appropriate composition, morphology, specific surface and high catalytic activity.

Catalytic Decomposition of Nitric Oxide by LaCoO3 Nano-particles Prepared by Rotary CVD

Catalytic direct decomposition of NO by perovskite-type catalysts has attracted much attention for the various possible components and the unique structure. LaCoO3 nanoparticles were precipitated on α-Al2O3 micro powders by rotary chemical vapor deposition (rotary CVD) and its catalytic performance for the decomposition of NO was investigated. LaCoO3 nano-particles with 100 nm in average diameter and 1.5% in mass were uniformly dispersed on α-Al2O3 powder. The conversion of NO increased with increasing temperature from 400 to 950 °C, and reached 28.7% at 950 °C. The gas velocity of transformed NO on LaCoO3 nano-particles catalyst per mass unit was 7.7 mL/(g min), showing a good catalytic activity over the calculated results of pure catalysts. After five times of aging performance experiments, the NO conversion kept the same value, showing a good aging performance and thermal stability.

Removal of Greenhouse Gas (N2O) by Catalytic Decomposition on Natural Clinoptilolite Zeolites Impregnated with Cobalt

In this work, natural zeolite, clinoptilolite were treated with acid (0.6 N HCl; code “Z-AM”) and alkaline solutions (1.5 N NaOH; code “Z-BM”). Thereafter, non-modified (as parent zeolite; code “Z-NM”) and modified zeolites were impregnated with cobalt using wet incipient impregnation method (Codes: “Z-AM-Co-0.5,1,1.5”, “Z-BM-Co-0.5,1,1.5”, “Z-NM-Co-0.5,1,1.5”). The prepared zeolites were characterized by XRD, ICP-OES, BET, NH3-TPD and H2-TPR. Also, these materials were studied for the catalytic decomposition of nitrous oxide (a greenhouse gas) to nitrogen and oxygen. The obtained results showed that the applied modifications had no significant influence (destruction) on the main structure of the zeolites including clinoptilolite, quartz and cristobalite. In addition results showed that acid modification increases the nitrous oxide decomposition because of surface area increment and the higher amount of CO/Al as well as the strong acid sites of this zeolite compared to other zeolites. Also, experiments showed that the main active species in nitrous oxide decomposition are mono-atomic (Co2+ cations) and other species exhibit much lower activity. In conclusion, natural clinoptilolite zeolites treated with acid and impregnated with Cobalt (Z-AM-CO-1.5) could be a very effective and cost-benefit catalyst for reducing N2O as a greenhouse gas, due to its very low price, high chemical stability and high availability.

Synthesis of a novel catalyst with nano metal core/carbon shell by a facile pre-complexation strategy and its application in enhanced catalytic decomposition of nitric oxide

In this work, a novel and facile pre-complexation strategy was reported for the synthesis of carbon-metal catalyst for the first time. The carbon-metal catalyst (SF250) was obtained by thermal-activating pre-complexation of ferric chloride and sodium salicylate. The HRTEM and XRD showed that SF250 contained nanometer particles with core of FeOOH and shell of carbon species. When SF250 was applied in selective catalytic reduction of nitric oxide (NO), it resulted in outstanding efficiency and long-term stability: the removal of NO was 99.8% with a fluctuation of 0.8%; moreover, the SF250 maintained high efficiency of removal for more than 3000min at 400°C. The analyses of EELS and TG-MS suggested that solid-phase and gas-type carbons both participated in reduction of NO, thus resulting in the excellent activity at low temperature. The solid-phase carbon included the active species with great reducibility distributed on the core-shell interface. The gas-type carbon included CO and benzene radicals. Therefore, our work has suggested a novel method for the synthesis of catalyst with core-shell structure by simple operation and low-cost precursors, together with excellent activity toward catalytic reduction of NO.

Recent Advances in Catalytic Decomposition of N2O on Noble Metal and Metal Oxide Catalysts

Catalytic decomposition of nitrous oxide (N2O) is one of the most efficient methods for the removal of N2O which is of high greenhouse potential and ozone-depleting property. Recent progress in the decomposition of N2O has been reviewed with the focus on noble meal and metal oxide catalysts. The influence factors, such as catalyst support, preparation method, alkali metal additives and the reaction conditions (including O2, H2O, SO2, NO and CO2), on the performance of deN2O catalysts have been discussed. Finally, future research direction for the catalytic decomposition of N2O is proposed.

Effective catalytic decomposition of nitrous oxide over highly active and stable bimetallic CoIn-mordenite zeolite

In this study, a bimetallic CoIn-mordenite (MOR) catalyst was prepared via simple wet ion exchange, and its ability to decompose nitrous oxide (N2O) was examined. The incorporation of a trace amount of In into Co-MOR catalyst greatly enhanced its catalytic activity and stability. CoIn-MOR decomposed more than 90% of N2O at 450 °C under simulated conditions of typical nitric acid emissions, and high activity was maintained for longer than 100 h under these strict conditions. The excellent activity of the bimetallic CoIn-MOR catalyst was attributed to strong synergistic effect between In and Co, which re-located cobalt oxides into β ion exchange sites. Those β-type Co ions are the most active sites for N2O decomposition due to the cooperation of N2O splitting by two neighboring Co ions in MOR. Higher amount of surface NOx species are in situ formed, which facilitate the removal of atom O and result in NO-assisted N2O decomposition and greatly improves the activity. Moreover, extended X-ray absorption fine structure analysis indicated that β-type Co ions exhibited stronger coordination to framework oxygens after. In addition, preventing their migration into CoOx clusters. Thus, high activity was maintained.

Theoretical investigation of novel two-step decomposition of nitric oxide over Fe(II) ion-exchanged zeolites using DFT calculations

A new method for the direct catalytic decomposition of nitric oxide (NO) is proposed in order to overcome several well-known problems toward its practical use. In this novel methodology, NO is first selectively adsorbed on Fe(II) ion-exchanged zeolites (LTA, MFI, and FAU) in the presence of excess oxygen; the concentrated NO in the zeolite microchannels is then decomposed by low-energy irradiation. The NO molecule is selectively adsorbed on Fe(II)–zeolites under the excess oxygen conditions, and that NO bond cleavage is more likely to occur for NO on Fe(II) than in the gas phase, because Fe(II) supplies an electron into an orbital of the NO molecule. A dinitrosyl species formed on Fe(II) sites in zeolites is decomposed via a N2O intermediate with lower activation energy. Achieving a closer distance between the two nitrogen atoms of two NO molecules by concentrating them on Fe(II) in zeolitic microcages is key to accelerate the decomposition with greatly reduced energy requirements. Based on these results, a catalytic redox cycle of Fe(II) in zeolites for NO decomposition is proposed, where the largest activation energy (the rate-determining step) is for the reaction 2NO→N2O+O (ca. 160kJ/mol), which is higher than that of NO decomposition on Cu-ZSM-5 (ca. 135kJ/mol). It is proposed that imitating the molecular mechanism of fungal nitric oxide reductase (P450nor) by utilizing an adjacent proton on Fe(II) ion-exchanged proton-form zeolite, the required energy for 2NO→N2O+O decreases further (ca. 40kJ/mol), allowing for successful reaction initiation with low-energy irradiation such as microwaves.

A dopant-mediated recombination mechanism in Fe-doped TiO2 nanoparticles for the photocatalytic decomposition of nitric oxide

The photon-assisted adsorption and catalytic decomposition of nitric oxide (NO) over undoped and Fe-doped TiO2 nanoparticles have been investigated by in situ diffuse reflectance infrared Fourier transformed (DRIFT) spectroscopy, in situ X-ray photoelectron spectroscopy (XPS) and on-line NOx analysis. The DRIFT spectra and on-line NOx analysis reveal that the usual photo-oxidation of NO to NO2 is strongly suppressed by the Fe dopant. This is found to be caused by the photo-reduction of Fe3+ to Fe2+, which is an effective adsorption site for nitric oxide species. The DRIFT spectra indeed reveal a new band at 1805cm−1, which is assigned to the NO stretch vibration in a Fe2+(NO)2 complex. Instead of producing NO2, photo-generated hydroxyl radicals oxidize the Fe2+ back to Fe3+. This causes the NO to desorb again, effectively closing an NO-mediated recombination loop. These results support the recently proposed reaction mechanisms for the photocatalytic decomposition of NO over undoped and Fe-doped TiO2, and provide new insights for the development of highly selective photocatalysts based on doped metal oxides.