Direct Catalytic Decomposition Research Articles

Ambient atmospheric application and influencing factors of ozone catalytic decomposition materials in a channel test

Surface ozone pollution is a significant environmental problem. In addition to the control of ozone precursors, direct catalytic decomposition of ozone is an effective control method with broad prospects. At present, the evaluation of the ozone decomposition performance of catalysts is typically performed in the laboratory, and the lack of scientific evaluation means to apply them to complex ambient atmosphere limits the practical application of ozone removal catalysts. Here, we devised a new evaluation method for ozone catalytic decomposition materials in the ambient atmosphere that can comprehensively evaluate the influence of various factors in the ambient atmosphere on performance. The results showed that ozone catalytic decomposition materials can maintain a decomposition efficiency of more than 20% in ambient atmosphere. The decomposition efficiency is mainly affected by distance, the closer the distance; the higher the decomposition efficiency. In addition, the concentration of ozone in the environment also affects the decomposition efficiency and shows a positive correlation. As the ozone concentration increased, the decomposition efficiency increased. An increase in relative humidity can cause a decline in decomposition efficiency, but this effect is eliminated with a decrease in humidity. In addition, the ozone catalytic decomposition materials can reduce the ozone concentration in the environment from 160 μg/m3to less than 100 μg/m3, which can play a great role in environmental ozone pollution control.

Density Functional Theory Study of Mechanism of Reduction of N2O by CO over Fe-ZSM-5 Zeolites

Nitrous oxide (N2O) is an industrial waste gas (e.g., from the production of adipic acid), which damages the ozone layer and causes the greenhouse effect. Density functional theory calculations were employed to investigate the mechanism of direct catalytic decomposition of N2O and selective catalytic reduction (SCR) of N2O by CO over Fe-ZSM-5 zeolites. Two stable Fe-active sites with six-membered ring structures on Fe-ZSM-5 were considered. The calculations indicate that the decomposition of N2O is affected by the coordination environment around Fe and can occur through two reaction pathways. However, there is invariably a more considerable energy hurdle for the initiation of the second stage of N2O decomposition. When CO participated in the reaction, it showed good reactivity and stability, the reaction energy barriers of the rate-limiting step were reduced by roughly 20.57 kcal/mol compared to the direct catalytic decomposition of N2O. CO exhibited a superior electron-donating ability and orbital hybridization performance during the reaction, which enhanced the cyclicity of the N2O reduction catalytic process. Our calculations confirmed the significant role of CO in N2O reduction over Fe-ZSM-5 observed in previous studies. This study provides a valuable theoretical reference for exploring CO-SCR methods for N2O reduction over Fe-based zeolite catalysts.

Progress and challenges in nitrous oxide decomposition and valorization.

Nitrous oxide (N2O) decomposition is increasingly acknowledged as a viable strategy for mitigating greenhouse gas emissions and addressing ozone depletion, aligning significantly with the UN's sustainable development goals (SDGs) and carbon neutrality objectives. To enhance efficiency in treatment and explore potential valorization, recent developments have introduced novel N2O reduction catalysts and pathways. Despite these advancements, a comprehensive and comparative review is absent. In this review, we undertake a thorough evaluation of N2O treatment technologies from a holistic perspective. First, we summarize and update the recent progress in thermal decomposition, direct catalytic decomposition (deN2O), and selective catalytic reduction of N2O. The scope extends to the catalytic activity of emerging catalysts, including nanostructured materials and single-atom catalysts. Furthermore, we present a detailed account of the mechanisms and applications of room-temperature techniques characterized by low energy consumption and sustainable merits, including photocatalytic and electrocatalytic N2O reduction. This article also underscores the extensive and effective utilization of N2O resources in chemical synthesis scenarios, providing potential avenues for future resource reuse. This review provides an accessible theoretical foundation and a panoramic vision for practical N2O emission controls.

Low-temperature direct decomposition of NO over Rh/NC-MnFe catalyst: activity, stability and mechanism

As the ideal NO removal technology, the biggest challenge associated with the direct catalytic decomposition of NO is the development of highly active deNOx catalysts at low temperatures.

In-situ polymerization intercalation of montmorillonite to achieve Co3O4 barrier dispersion for direct catalytic decomposition of N2O

Herein, the Co-MMT (Co3O4-montmorillonite) catalysts were prepared by coordination-deposition (Co(0.015)-MMT-2(CD)) and deposition-precipitation method (Co(0.015)-MMT-2 (DP)) for the N2O direct decomposition, respectively. The structure, texture, and surface properties of the catalysts are characterized by XRD, TEM, FT-IR, Raman, XPS, and so on. The results show that compared with Co(0.015)-MMT-2(DP), Co(0.015)-MMT-2(CD) achieves barrier dispersion of active phase (Co3O4) by using the layer structure of montmorillonite and has a smaller Co3O4 crystal size, richer oxygen vacancy and higher content of Co2+Oh. In addition, the results of DFT calculation and kinetic calculation indicate that Co2+Oh possesses higher reaction activity than Co2+Td and Co3+Oh, and the TOF value of Co(0.015)-MMT-2(CD) at 400 ℃ is 3 times higher than that of Co(0.015)-MMT-2(DP). Therefore, the Co(0.015)-MMT-2(CD) catalyst shows excellent catalytic activity and tolerance to impurity gases (H2O, NO, and O2), and it can maintain 100% conversion at least 50 h for the direct catalytic decomposition of N2O.

Advances in Catalytic Decomposition of N2O by Noble Metal Catalysts

Nitrous oxide (N2O) is an environmental pollutant that has a significant greenhouse effect and contributes to the depletion of the ozone layer. To address the issues caused by N2O, direct catalytic decomposition of N2O to N2 and O2 has been demonstrated as one of the most efficient methods for its removal. Various metals, particularly noble metals, including Rh, Ru, Pd, Pt, Au, and Ir, have been widely used and investigated as catalysts to facilitate this transformation. Therefore, this review aims to provide an overview of the advances in noble metal-based catalysts studied in recent years. The comprehensive discussion includes the influence of multiple factors, such as catalyst supports, preparation methods, additives, and impurity gases (such as O2, H2O, SO2, NO, and CO2) on the performance of versatile catalysts. Furthermore, this review offers insights into the future trends of catalyst systems for the direct catalytic decomposition of N2O.

Effect of cobalt modification onto a Beta zeolite for the direct catalytic decomposition of dimethyl sulfide

For the development of small-scale desulfurization processes such as fuel cell systems, catalytic decomposition of dimethyl sulfide (DMS) to H2S without H2 addition was investigated using a Co/H-Beta zeolitic catalyst, with its acidity controlled via post-synthesis modification. The protonated zeolite (H-Beta) exhibited little catalytic activity at 400 °C, but Co modification significantly promoted DMS decomposition, with a high H2S yield of 50% observed. The optimum Co amount was equivalent to half of the ion-exchange capacity of the original H-Beta zeolite. While the Co/SiO2 did not display catalytic activity, and thus, the coexistence of acid and Co ion sites is necessary in DMS decomposition. The Co species were introduced at the cation sites of the zeolite, suppressing Co sulfurization, which contributed to the high catalytic activity.

Non-thermal Plasma Synergizes High-Alkalinity Hydroxyapatite Supported RhFe Bimetallic Catalyst for Direct Catalytic Decomposition of N2O at Low Temperature

Non-thermal Plasma Synergizes High-Alkalinity Hydroxyapatite Supported RhFe Bimetallic Catalyst for Direct Catalytic Decomposition of N2O at Low Temperature

Effect of Zinc on the Structure and Activity of the Cobalt Oxide Catalysts for NO Decomposition

Co4−iZniMnAlOx mixed oxides (i = 0, 0.5 and 1) were prepared by coprecipitation, subsequently modified with potassium (2 or 4 wt.% K), and investigated for direct catalytic NO decomposition, one of the most attractive and challenging NOx abatement processes. The catalysts were characterised by atomic absorption spectroscopy, powder X-ray diffraction, Raman and infrared spectroscopy, temperature-programmed reduction by hydrogen, the temperature-programmed desorption of CO2 and NO, X-ray photoelectron spectroscopy, scanning electron microscopy, the work function, and N2 physisorption. The partial substitution of cobalt increased the specific surface area, decreased the pore sizes, influenced the surface composition, and obtained acid-base properties as a result of the higher availability of medium and strong basic sites. No visible changes in the morphology, crystallite size, and work function were observed upon the cobalt substitution. The conversion of NO increased after the Co substitution, however, the increase in the amount of zinc did not affect the catalytic activity, whereas a higher amount of potassium caused a decrease in the NO conversion. The results obtained, which were predominantly the acid-base characteristics of the catalyst, are in direct correlation with the proposed NO decomposition reaction mechanisms with NOx− as the main reaction intermediates.

Direct decomposition of NO over 8MR in high silica Cu-LTA zeolite: A DFT study on reaction mechanisms, thermodynamics and kinetics

NO is a principal air pollutant that has received increasing attention due to its harmful impact on the environment and human health. Direct catalytic decomposition of NO to N2 is a process that carries promising potential with further development of metal-exchanged zeolitic catalysts, while the challenge lies with the thermal durability of the catalysts. Several reports have cited Cu-loaded high silica to aluminium ratio (SAR) Linde Type A (LTA) zeolites to be effective deNOx catalysts with their high catalytic activity and hydrothermal stability, but the detailed mechanisms by which it acts are still poorly understood. In this study, both the Eley-Rideal (E-R) and Langmuir-Hinshelwood (L-H) processes were discussed to elucidate a feasible reaction pathway that allows NO to be directly converted to N2O over the loaded-Cu in the eight-member ring (8MR) of the high silica LTA. The results have indicated that the L-H process is the most favourable pathway for the given temperature window (298.15–900 K). In addition, as the oxidation intermediate Cu-O hindered the desired NO conversion, multiple gaseous components (NO, CO, N2) that frequently existed in the catalytic process were considered for residual O (Ores) removal. NO and CO were both determined to be more favourable than N2 as reductants for the Ores removal, in consideration of their kinetic and thermodynamic characters. As a result, the high silica Cu-LTA showed catalytic feasibility in direct NO conversion from mechanistic insights.

Carbon/iron by-product from catalytic methane decomposition as recyclable Fenton catalyst for pollutant degradation

Direct catalytic decomposition of methane (CDM) has been studied as a possible emission-free hydrogen production route for over 100 years. However, the high cost of catalyst regeneration limits its practical applications. Here, we demonstrate that the solid by-product from CDM using Fe ore catalysts comprising carbon nano onions encapsulated with magnetic Fe cores (Fe@C) can serve as efficient and recyclable Fenton catalysts for pollutant degradation. Fe@C/H2O2 has better performance than FeSO4/H2O2 at similar Fe concentrations and can be used to decompose various pollutants. Mechanistic studies reveal that graphitic carbon layers and encapsulated Fe0 contribute to their high catalytic activity. Further, Fe@C can be easily recovered from an aqueous solution and reused due to the encapsulated magnetic Fe particles. Over three reused cycles, Fe@C/H2O2 only yields 1/8 of Fe sludges compared to FeSO4/H2O2, significantly reducing Fe sludge treatment costs. Overall, Fe@C demonstrates excellent application potentials in water and wastewater treatment, making H2 production via CDM economically more viable.

Intensification of catalytic reaction of nitrous oxide decomposition into a replaceable wall-coated microreactor using electrophoretic deposition method

The novel replaceable wall-coated micro-reactor has been introduced to eliminate the hazardous nitrous oxide by utilizing the direct catalytic decomposition method. The commercial Pd/ γ-Al2O3 catalyst (containing 0.5 wt.% Pd) is coated on SUS304 stainless steel microchannels walls by using electrophoretic deposition (EPD) and then investigated at the temperature range of 300-400 °C. The main scope of this study is to define the optimum parameters affecting EPD such as deposition time, electrophoretic voltage, and solvent as the suspension media to reach the complete decomposition of nitrous oxide. The catalytic activity of the coated microchannels is verified at various gas hourly space velocities (GHSV). The nitrous oxide decomposition is enhanced 300% by raising the deposition time from 1 minute to 3 minutes and then remarkably is declined 80% at times higher than 3 minutes. The optimum electrophoretic deposition parameters including deposition time of 3 minutes at the voltage of 120 V in the range of 30-160 V and isopropanol as the solvent, resulting in 100% decomposition of nitrous oxide at 400 °C and GHSV of 1000 mL h−1 g−1cat . Moreover, the performance of the wall-coated micro-reactor at optimum EPD conditions compared to the equivalent packed-bed reactor caused 40% improvement in nitrous oxide decomposition and its energy consumption is 33.3% lower than packed-bed reactor for equal N2O decomposition.

Membrane Catalysis: N2O Decomposition over La0.2Sr0.8Ti0.2Fe0.8O3–δ Membrane with Oxygen Permeability

AbstractCompared to conventional heterogeneous catalysis, membrane catalysis can facilitate in situ removal of inhibiting species on a catalyst, therefore effectively increases the reaction rate. Herein, kinetically controlled decomposition of N2O was studied employing a La0.2Sr0.8Ti0.2Fe0.8O3–δ (LSTF) perovskite membrane, and the direct catalytic N2O decomposition over membrane surface was compared with membrane catalysis of N2O decomposition involving in situ oxygen removal. In the case of membrane catalysis, oxygen produced from N2O conversion can be in situ removed by using a LSTF oxygen‐permeable membrane, thus increasing the amount of surface active sites for N2O decomposition. By sweeping hydrogen at one side of the membrane to consume the permeated oxygen from the other side N2O conversion was improved.

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.

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.

The correlation of NO chemisorption adsorption with its directly catalytic dissociation pathway on β-MnO2(1 1 0) and (1 0 1) surfaces

MnO2-based oxide catalysts have recently drawn so much attention owing to its good catalytic activity for NOx direct catalytic decomposition at low-temperature. As the reaction mechanism of NO direct catalytic decomposition on different MnO2 surfaces is not yet clear, it is important to understand the influence of different crystal surfaces of β-MnO2 on catalytic activity for NO decomposition. The correlation of NO chemisorption with its dissociation pathways on β-MnO2(110) and (101) surfaces are investigated based on density functional theory (DFT) with Vienna Ab-initio Simulation Package (VASP). The calculation results have shown that NO prefers to be adsorbed on β-MnO2(110) instead of β-MnO2(101) surface. The analysis results of density of states and differential charge density indicate that the interaction between NO and β-MnO2(110) surface is stronger and the adsorbed NO had more charge transfer with β-MnO2(110) surface. The effective activation energies of the possible NO dissociation pathways on the β-MnO2(110) and (101) surfaces are 2.57 and 3.07 eV, respectively. The lower energy barrier on β-MnO2(110) must be associated with the bridge adsorption of NO and more electrons transfer from NO to the surface, which is conducive to the breaking of N-O bond.

Blue hydrogen and carbon nanotube production via direct catalytic decomposition of methane in fluidized bed reactor: Capture and extraction of carbon in the form of CNTs

The current study reports a regenerative approach for producing blue hydrogen (COx-free) and carbon nanotubes (CNTs) from natural gas (methane). The multi-metallic nickel-based copper and zinc promoted catalyst with an optimal composition (60%Ni-5%Cu-5%Zn/Al2O3) was synthesized in the laboratory and used for the pyrolysis of methane in a fluidized bed reactor under bubbling conditions. Fluidized bed reactor hydrodynamics and CNT extraction were well-thought-out while designing the catalyst. The separation of the CNTs and partial regeneration of the spent catalyst was performed using the ultrasonication technique. The regeneration ability of the catalyst was examined by performing multiple reaction-regeneration cycles. The regenerated catalyst regained its full activity, and >90% methane conversion was achieved with high-quality CNTs (o.d 60–80 nm, length 5 μm). State-of-the-art characterization tools like 3D-Raman mapping, high-resolution electron microscopy, EDX mapping were utilized to analyze CNTs. 3D-Raman map consists of 29,200 spectra ensured the uniformity and purity of grown CNTs.

Boosting nitrous oxide direct decomposition performance based on samarium doping effects

A series of Sm-doped Co3O4 catalysts for the N2O direct catalytic decomposition were synthesized by the sol–gel method using citric acid as a chelating agent and urea as a combustion agent. The doping of Sm significantly altered the activity of N2O decomposition on the Co3O4 catalyst. Sm was incorporated into the Co3O4 matrix, leading to the distortion of Co3O4 lattice with the spinel configuration maintained. Sm-doping can effectively promote the oxygen vacancy generation, and the electron interaction between Co and Sm species occurred as the Co3+ + Sm2+ ↔ Co2+ + Sm3+ redox cycle. Combined with in situ Raman and in situ NAP-XPS results proposed that this redox cycle is the main reason that the Sm-doping accelerates the high-efficiency N2O decomposition.

Pd Supported on ZSM-5 with different ratios of Si/Al as catalysts for direct catalytic decomposition of methane

Hydrogen and filamentous carbon have been produced by direct catalytic decomposition of methane. ZSM-5 Zeolite with ratios of Si/Al (25, 140, and 750) was used as a support in 0.5 wt% Pd/ZSM-5 catalysts. Fresh and spent Pd/ZSM-5 catalysts were characterized by XRD, SEM, TGA and CHN analyses. The hydrogen formation rates for the catalysts were Pd/ZSM-5 (25) < Pd/ZSM-5 (140) < Pd/ZSM-5 (750). The CHN analysis showed wt% of the carbon that was deposited, over the catalysts, during the reaction run to be 15.6, 17.1, and 34.3 for Pd/ZSM-5 (25), Pd/ZSM-5 (140), and Pd/ZSM-5 (750), respectively. The SEM images revealed that filamentous carbon was produced. It appears that the zeolite support in different Si/Al ratios led to form different sizes of palladium particles and palladium dispersion over ZSM-5 support. It is suggested that the catalyst activity be ascribed to the palladium particles size and its dispersion over ZSM-5.

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...