N2O Decomposition Research Articles

Waste eggshell to valuable Co3O4/eggshell material as an efficient catalyst for catalytic decomposition of N2O under simulated real tail gases

Co3O4 shows excellent catalytic activity for N2O decomposition, in which it is urgently needed to develop novel efficient catalysts/supports with cheap and environmentally-friendly properties. Herein, Co3O4 nanoparticles decorated eggshell catalysts (Co3O4/eggshell-GR, Co3O4/eggshell-IM, and Co3O4/eggshell-DP) were prepared using simple grinding, impregnation, and deposition-precipitation methods, where waste eggshells were used as an effective support and reaction-promoter. The results indicated that the preparation methods significantly influenced the catalytic activity of Co3O4/eggshell catalysts; the highest activity was obtained over the Co3O4/eggshell-DP. The activity of Co3O4/eggshell-DP was comparable to that of pure Co3O4. More importantly, its specific activity was about 7.3 times that of Co3O4 at 400 °C. The examined Co3O4/eggshell-DP also displayed outstanding stability and anti-poisoning property in NO, O2, and/or H2O-containing atmospheres. It was also verified that the excellent activity of Co3O4/eggshell-DP correlated with the unique structure of the eggshell and the close incorporation between CaCO3 and Co3O4. The Co3O4/eggshell-DP catalyst owned abundant Co3O4 nanoparticles, more Co3+ species, and excellent redox performance, promoting the conversion of N2O at a lower temperature. The presence of abundant surface basic sites and a larger amount of oxygen vacancies also facilitated the catalytic efficiency of Co3O4/eggshell-DP.

Impact of ROS 2 Node Composition in Robotic Systems

The Robot Operating System 2 (ROS 2) is the second generation of ROS representing a step forward in the robotic framework. Several new types of nodes and executor models are integral to control where, how, and when information is processed in the computational graph. This paper explores and benchmarks one of these new node types - the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Component</i> node - which allows nodes to be composed manually or dynamically into processes while retaining separation of concerns in a codebase for distributed development. Composition is shown to achieve a high degree of performance optimization, particularly valuable for resource-constrained systems and sensor processing pipelines, enabling distributed tasks that would not be otherwise possible in ROS 2. In this work, we briefly introduce the significance and design of node composition, then our contribution of benchmarking is provided to analyze its impact on robotic systems. Its compelling influence on performance is shown through several experiments on the latest Long Term Support (LTS) ROS 2 distribution, Humble Hawksbill.

Insights into reaction pathway induced by d orbital occupancy on cobalt supported boron nitride for N2O catalytic decomposition

Nitrous oxide (N2O), as a typical greenhouse gas, is urgent to be eliminated to address the global climate issue. Developing low-temperature N2O decomposition catalysts is crucial for mitigating greenhouse gas emissions. Herein, we propose a Cobalt-supported boron nitride (Co-BN) catalyst with a low reaction energy barrier (1.37 eV) using density functional theory calculations. The coordination environment is critical to the reaction mechanism and energy barrier, where the CoN3 configuration (Co coordinated with three N atoms) triggers the Eley-Rideal (E-R) mechanism, but the CoB3 configuration (Co coordinated with three B atoms) engenders the Langmuir-Hinshelwood (L-H) mechanism. Fundamentally, the reaction mechanism is dominated by d orbital occupancy. Following the adsorption of *O intermediate, a fully filled d orbital is realized on *O-CoN3, which prevents N2O from bonding with Co, thus following the E-R mechanism through directly interacting with *O specie. Conversely, the partially unoccupied d orbital is identified on *O-CoB3, provinding the bonding site on Co for N2O molecule, thereby leading to the L-H mechanism. Our work provides a novel N2O decomposition catalyst theoretically, and the insights into the relationship between d orbital occupancy and the reaction mechanism, would pave a new avenue for the design of N2O decomposition catalysts.

Highly effective and energy-saving adsorption-microwave catalytic decomposition of NO with novel high-adsorption-capacity adsorbent in a two-stage fixed-bed reactor

It is a great challenge to achieve high efficiency and low energy consumption denitrification without adding reducing agent at low temperature. Herein, we developed MgCo2O4-BaCO3/AC carbon-based composites as novel and cheap adsorbents with high adsorption capacity to fill the first section of two-stage fixed-bed reactor to form adsorption bed, and MgCo2O4-40%BaCO3 as catalyst was filled in the second section as catalyst bed. Significantly, under the condition of excess O2, the adsorption capacity of 20%MC-0.5Ba/AC for NO was as high as 40.2 mg/g, and the conversion of adsorbed NO was as high as 99.7% under microwave irradiation at 250 °C. The denitrification efficiency of the two-stage fixed bed reactor was much higher than that of the one-stage fixed bed reactor. The energy efficiency of adsorption-decomposition method was 14 times higher than that of direct decomposition method. Interestingly, the activated carbon was not consumed during the whole reaction process, so no secondary pollution such as CO and CO2 was produced. More importantly, despite the presence of SO2, CO2 or H2O in the inlet gas, 20%MC-0.5Ba/AC still showed excellent adsorption capacity for NO, and the absorbed NO could be successfully decomposed, demonstrating excellent resistance to SO2, CO2 and H2O. This work presents a new route for denitrification technology with high efficiency, low energy consumption and no secondary pollution, and provides guidance for rational design of adsorbents with high adsorption capacity for NO.

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.

Highly Rotationally Excited N2 Reveals Transition-State Character in the Thermal Decomposition of N2O on Pd(110).

We employ time-slice and velocity map ion imaging methods to explore the quantum-state resolved dynamics in thermal N2O decomposition on Pd(110). We observe two reaction channels: a thermal channel that is ascribed to N2 products initially trapped at surface defects and a hyperthermal channel involving a direct release of N2 to the gas phase from N2O adsorbed on bridge sites oriented along the [001] azimuth. The hyperthermal N2 is highly rotationally excited up to J = 52 (v″ = 0) with a large average translational energy of 0.62 eV. Between 35 and 79% of the estimated barrier energy (1.5 eV) released upon dissociation of the transition state (TS) is taken up by the desorbed hyperthermal N2. The observed attributes of the hyperthermal channel are interpreted by post-transition-state classical trajectories on a density functional theory-based high-dimensional potential energy surface. The energy disposal pattern is rationalized by the sudden vector projection model, which attributes to unique features of the TS. Applying detailed balance, we predict that in the reverse Eley-Rideal reaction, both N2 translational and rotational excitation promote N2O formation.

Bipropellant Enabled Solid Oxide Fuel Cell Stack Power Supply: Energy Agility for Space Vehicles

A Solid Oxide Fuel Cell (SOFC) system capable of running on the same fuel and oxidizer as an onboard bipropellant thruster can create enhanced operational flexibility. If a spacecraft needs thrust, the bipropellant can be ignited to provide thrust. If a spacecraft needs electric power, the spacecraft can consume bipropellant to generate auxiliary power. In this work, the proven bipropellant pair ammonia (NH3) and nitrous oxide (N2O) are shown to be a viable fuel and oxidant for SOFCs, as in situ thermal NH3 cracking will generate H2 and N2O decomposition will generate O2. A 5 cell SOFC stack produced 89 W when fueled with NH3 and N2O. The results of this study demonstrate the potential for a bifunctional spacecraft system that can satisfy both operational power and on-orbit maneuverability requirements.

NiCoAl-Based Monolithic Catalysts for the N2O Intensified Decomposition: A New Path towards the Microwave-Assisted Catalysis

Nitrous oxide (N2O) is considered the primary source of NOx in the atmosphere, and among several abatement processes, catalytic decomposition is the most promising. The thermal energy necessary for this reaction is generally provided from the external side of the reactor by burning fossil fuels. In the present work, in order to overcome the limits related to greenhouse gas emissions, high heat transfer resistance, and energy losses, a microwave-assisted N2O decomposition was studied, taking advantages of the microwave’s (MW) properties of assuring direct and selective heating. To this end, two microwave-susceptible silicon carbide (SiC) monoliths were layered with different nickel–cobalt–aluminum mixed oxides. Based on the results of several characterization analyses (SEM/EDX, BET, ultrasound washcoat adherence tests, Hg penetration technique, and TPR), the sample showing the most suitable characteristics for this process was reproduced in the appropriate size to perform specific MW-assisted catalytic activity tests. The results demonstrated that, by coupling this catalytic system with an opportunely designed microwave heated reactor, it is possible to reach total N2O conversion and selectivity of a highly concentrated N2O stream (50 vol%) at T = 550 °C, the same required in the conventionally heated process to remove N2O from a less concentrated gas stream (20 vol%).

Chemical Titration of Promoted Ag/α‐Al2O3 Ethylene Epoxidation Catalysts

AbstractWe enumerate the active site density for a promoted Ag/α‐Al2O3 ethylene epoxidation catalyst (35 wt.% Ag) by using trifluoroethanol as a chemical titrant. Trifluoroethanol, when introduced into the reactant stream, deprotonates to deposit stable trifluoroethoxy or trifluoromethyl groups on the Ag surface and inhibits ethylene oxide (EO) rates, thus enabling us to assess catalytic site densities. Active site densities vary between 52 and 69 μmolTFE gcat−1 across different chlorine coverages (0–0.4 monolayers) and different oxygen concentrations (2.5–7.7 mol%) in the reactor feed. Site densities measured by in situ trifluoroethanol chemical titration are distinct compared to those evaluated using ex‐situ N2O decomposition (12.3 μmolN2O gcat−1) suggesting that dynamic restructuring of the Ag surface under reaction conditions may render pre‐reaction chemisorption measurements insufficient to accurately enumerate the active sites relevant for ethylene epoxidation.

Assessing catalytic rates of bimetallic nanoparticles with active-site specificity: A case study using NO decomposition

Bimetallic alloys have emerged as an important class of catalytic materials and span a wide range of shapes, sizes, and compositions. The combinatorics across this wide materials space makes predicting catalytic turnovers of individual active sites challenging. Herein, we introduce the stability of active sites as a descriptor for site-resolved reaction rates. The site stability unifies structural and compositional variations in a single descriptor. We compute this descriptor by using coordination-based models trained with density functional theory (DFT) calculations. Our approach enables instantaneous predictions of catalytic turnovers for nanostructures up to 12 nm in size. Using NO decomposition as the probe reaction, we identify sites on AuPt nanoparticles that, because of local structure and composition, yield rates that are one to two orders of magnitude higher than those from sites on monometallic Pt. By prescribing specific sizes, morphologies, and compositions of optimal catalytic nanoparticles, our method guides experiments toward designing bimetallic catalysts with optimal turnovers.

Direct decomposition of nitrous oxide by rhodium supported on ZrSnO4

Novel catalysts of Rh/ZrSnO4 were synthesized, and their catalytic activities for the direct decomposition of nitrous oxide (N2O) were investigated. ZrSnO4 with an [Formula: see text]-PbO2-type structure was used as a promoter, since the oxygen supply from its lattice was expected to facilitate N2O decomposition. Among the prepared catalysts, 1.0 wt.% Rh/ZrSnO4 exhibited the highest catalytic activity: N2O was completely decomposed at [Formula: see text]C. This activity was higher than those for 1.0 wt.% Rh/ZrO2 and 1.0 wt.% Rh/SnO2, indicating that the ZrSnO4 solid promoted N2O decomposition. In addition, the 1.0 wt.% Rh/ZrSnO4 catalyst featured high durability in the presence of O2, CO2, and H2O vapors.

A novel fluidized-bed-electrode solid-oxide-fuel-cell reactor for N2O catalytic decomposition

Global warming potential (GWP) of N2O is 310 times that of CO2. However, conventional solid oxide fuel cell (SOFC) cathode catalytic N2O decomposition has been observed to have a low conversion rate, leading to uneven temperature distribution on the cathode surface. To address this issue, we proposed a novel gas–solid phase fluidized bed catalytic electrode for N2O decomposition in a SOFC system. The fluidized bed material was prepared using cerium oxide particles coated with lanthanum, strontium, and iron (CeO2-LSF). The N2O conversion rate was 99.78% at 720 °C. By assisting particle fluidization with argon, compared to the case of fixed bed electrode, the peak power density improved by a maximum of 39.86% at 670 °C. This improvement was due to mass transfer enhancement by particle fluidization, thereby reducing the concentration polarization of the SOFC. Furthermore, the maximum temperature difference inside the reactor decreased significantly from 92 °C to 42 °C when the cathode particles were fluidized. The reactor can achieve high-efficiency decomposition of N2O while simultaneously improving fuel cell power density and operational reliability.

The catalytic performance of Ba-Ce-Cu catalysts for N2O decomposition

Series of Ba-Ce-Cu catalysts were prepared by citric acid method and used for N2O decomposition, and the doping effects of Ba and Ce on CuO were studied. It was found that the activity and the tolerance of the catalyst to the impurity gases (NO, O2, H2O) can be effectively modified by the doping components. The Ba0.2Cu displayed much high activity to the reaction due to the significant effect of Ba stabilizing the active Cu+ species in the catalyst, but low tolerance to NO. The Ba0.2Ce0.5Cu catalyst exhibited not only higher catalytic activity compared with the Ba0.2Cu due to the synergistic effect of Ba and Ce, but also strong tolerance to NO, as the CeO2 in the catalyst could remove the adsorbed NOx species from the Cu+ through forming barium nitrate and catalyzing the latter decomposition.

Catalytic decomposition of NO using molten gallium: an experimental and computational study

Molten gallium (Ga) catalyzes the direct decomposition of NO. In a bubble column reactor, NO decomposition was conducted by injecting NO-containing bubbles into molten Ga at elevated temperatures (> 400 °C), and > 90% conversion was achieved in only ∼ 0.2 s of residence time at 550 °C. Computational analysis showed that despite the weak binding energy of NO to Ga surface (34.4 kJ/mol), thermodynamically favored NO* dissociation on Ga (−138.3 kJ/mol) facilitated decomposition. Although Ga surfaces can be poisoned by O* generated by the dissociation of NO*, introducing reduction gas promoted OH* formation (−51.1 kJ/mol) on the surface and subsequent H2O desorption, and consequently reactivated the Ga surface. NO decomposition and catalyst regeneration using reducing gas was repeated over 15 cycles in a single droplet reactor, and NO conversion was stably maintained. Experimental and computational results support the potential use of molten Ga as a catalyst for the direct decomposition of NO.

Highly active catalysts of mesoporous Ce-Cr-mAl2O3 and reaction mechanism for N2O-assisted oxidative dehydrogenation of ethylbenzene to styrene

The mesoporous Cr-mAl2O3 and Ce-Cr-mAl2O3 catalysts were prepared via a one-pot hydrothermal process for the N2O-assisted ethylbenzene (EB) selective oxidation to styrene, which was viewed as both a greenhouse recycling method and a new process for styrene (ST) production. It was found that 7Cr-mAl2O3 provided superior catalytic performance with respect to ST among Cr oxide-doped catalysts and that the Ce modification could further increase the ST yield to 54%. To clarify the promoting effect and mechanism of Ce-Cr species on catalytic performance, numerous types of characterization, particularly in-situ DRIFTS, were used. Results indicated that the favorable reducibility of catalyst was crucial for N2O activation. Carbon deposition was unavoidable during the reaction process, but adding Ce-Cr could reduce the stability of the deposited carbon and relief its detrimental effect on catalytic performance. The suitable surface acidity and high relative content of Cr6+ and Oα could be responsible for the excellent catalytic performance of Ce-7Cr-mAl2O3. In-situ DRIFTS not only identified the coupling effect between EB dehydrogenation and N2O decomposition but also proposed the possible reaction pathway that the adsorbed N2O reacted with the EB molecule, thereby providing a good explanation for the promoting effects of high content of N2O on the activity of Ce-7Cr-mAl2O3.

Numerical simulation of nitrogen oxides and carbon monoxide emissions of biodiesel diffusion flame

Biodiesel is one of the most promising fossil fuel replacements for automotive engines, furnaces, and turbines due to its sustainability, energy savings, and reduced carbon emissions. While commonly reported in engine studies, nitrogen oxides (NOx) and carbon monoxide (CO) released from combustion of biodiesel have not been studied in laminar diffusion flames. This numerical study examines the concentrations of NOx and CO emissions of the laminar biodiesel diffusion flames at different carbon flow rates and then compares its emissions with those of two liquid hydrocarbon fuel surrogates, n-heptane and iso-octane. A consistent carbon flow rate of 17.2 g/h is applied at the fuel inlet to compare the NOx and CO emissions of the three liquid fuels. The results show that biodiesel diffusion flame produces greater NOx and CO emissions with increasing carbon flow rate. At the same flow rate, n-heptane produces the greatest NO with 2.1% greater than biodiesel and 4.2% greater than iso-octane. The primary pathway for generating NO in biodiesel flame is the prompt pathway, with significant contributions from the thermal and NO2 decomposition pathways. While the NO productions in n-heptane and iso-octane flames are predominantly through the thermal pathway. It is also observed that biodiesel produces the greatest CO emission with 3.2% more than those of n-heptane and iso-octane. The oxidisation reaction of CO, CO + OH = CO2 + H primarily controls the CO mass fraction in the product for all fuels.

Experimental and kinetic study of N2O thermal decomposition in pressurized oxy-combustion

Pressurized oxy-combustion is regarded as a promising carbon capture technology for mitigating global warming. In addition, N2O is a significant greenhouse gas in pressurized oxy-combustion at moderate temperatures, with a Global Warming Potential 310 times that of CO2. It is important to study the formation and control of N2O in pressurized oxy-combustion. In this paper, the effects of CO2 atmosphere, pressure, temperature, residence time, and O2 concentration on N2O decomposition were investigated in a pressurized plug flow reactor. The results show that CO2 atmosphere significantly promotes N2O decomposition compared to N2 atmosphere. Increasing temperature accelerates the decomposition of N2O, with 1023–1223 K being the main decomposition temperature range. The decomposition efficiency of N2O increases with increasing pressure, while its increase becomes slow at above 5 bar. N2O decomposition efficiency in CO2 atmosphere decreases slightly as O2 concentration increases. The experimental results were compared to the kinetic modeling results calculated using GRI3.0 and GLA2018 mechanism, respectively. The modeling results show that GRI3.0 mechanism accurately predicts the decomposition of N2O at 1 bar while overestimates the decomposition at elevated pressures, while GLA2018 mechanism significantly underestimates the decomposition at all tested pressures. Further Rate-of-production analysis shows that the main reaction of N2O decomposition is N2O(+M) = N2 + O + M, which becomes the dominant reaction especially at elevated pressures. An enhanced third-body efficiency of 3 for CO2 was incorporated into the reaction N2O(+M) = N2 + O(+M) in GLA2018, which could predict the decomposition of N2O at elevated pressure accurately. The above results indicate that the decomposition of N2O is significantly enhanced in pressurized oxy-combustion.

Modeling of a Two-Bed Reactor for Low-Temperature Removal of Nitrogen Oxides in Nitric Acid Production

In this study, the modeling of the low-temperature catalytic abatement of NOX and N2O from tail gases in a weak nitric acid plant utilizing a single-pressure 0.716 MPa system was performed. A one-reactor concept assumes that in the first bed, NOX is reduced by ammonia on a commercial vanadia–alumina catalyst, and in the second bed, N2O is decomposed on a proprietary nickel–cobalt catalyst. The kinetics of N2O decomposition on a Cs/Ni0.1Co2.9O4 catalyst was experimentally studied in an isothermal flow reactor. The reaction rate constants were determined by varying the residence time and temperature; these data formed the basis for modeling kinetics and heat and mass transport in an adiabatic reactor in which the low-temperature mitigation of nitrogen oxides occurred. Taking into account the given spatial limitations inside the reactor and the allowable temperatures, the layer heights were evaluated to ensure a residual NOX and N2O content of less than 50 ppm. Catalyst loading using layers in a commercial reactor was estimated for the tail-gas flow rates of 46,040–58,670 m3/h. Simulations showed that the optimum inlet temperature was 260 °C; in this case, the NOX and N2O conversion targets were achieved in the range of 46,040–58,670 m3/h while adhering to catalyst bed height and outlet temperature limitations.

How hydroxyapatite governs surface Cu(II) and Fe(III) structuring: Effects in the N2O decomposition under highly oxidant atmosphere

In this work, we present copper- or iron-loaded hydroxyapatite samples as active catalysts in the direct N2O decomposition reaction. Hydroxyapatite, functionalized with increasing amount of Cu(II) or Fe(III) species (from 3 to 9 wt%), were characterized by XRPD, DR UV-Vis, XPS, CO-adsorption followed by FT-IR, TEM-EDS, and tested in the N2O decomposition. Stability tests (550 °C, 72 h), reusability, resistance to sulfur (50 ppm) and to alkali (ca. 1 wt% of K or Ba) completed the study of the catalyst performances. Copper catalysts showed superior performances than iron counterparts. The structural evolution of the metal species with loading plays a critical role in the catalytic behavior. In the case of Fe-catalysts, a gradual Fe-coverage of HAP surface resulted in an increasing trend in the activity. Conversely, for Cu-catalysts high activity and selectivity were associated with a moderate structuration of Cu(II) in the form of nanoparticles with size of around 1.6 nm.

Entropy Generation and Exergy Assessment of Methane–Nitrous Oxide Diffusion Flames in a Triple-Port Burner

A triple-port burner was used in this study, and a numerical simulation was employed to investigate the entropy generation rate of CH4–N2O diffusion flames at the R ratio = 1 . Here, R ratio refers to the ratio of the oxidizer flow velocity to the fuel flow velocity. In order to scrutinize the decomposition effect of N2O on entropy generation, an oxygen-enriched gas with the same nitrogen to oxygen ratio as N2O (N-to- O = 2 ) was used in CH4–N2–O2 diffusion flames. Besides, because the N2O could decompose into the oxygen-enriched gas, the oxygen-enriched effect was also studied by the CH4–air diffusion flames that were conducted in this research. The entropy generation rate comprises of three items in this study, including heat conduction, mass diffusion, and chemical reaction. As a result, the different reaction pathways would take part in the major reaction pathway in CH4–N2O diffusion flames, causing more entropy generation rate being produced through the more intense reactions in CH4–N2O diffusion flames. The irreversibility in CH4–air diffusion flames are dominated through heat conduction and chemical reaction, which is an identical result in CH4–N2–O2 diffusion flames. However, in CH4–N2O diffusion flames, chemical reactions dominated the irreversibility because of the more intense reaction caused by the thermal effect of N2O decomposition. As a result, the decomposition effect of N2O influences the availability of CH4–N2O diffusion flames.