Ethylene Combustion Research Articles

Surface in situ Co-Mn modification over LaMnO3 perovskite with enhanced activity for ethane combustion

Catalytic combustion is one of effective ways to remove short-chain alkanes. In this study, we elaborately designed a novel catalyst of in situ Co-Mn decorated LaMnO3 perovskite for ethane catalytic combustion, in which extra Mn and Co species were introduced via acidic KMnO4 and Co(NO3)2 solution precipitation method. The addition of Mn and Co could not only slightly etch LaMnO3, thereby increasing specific surface area and redox property, but also generate new active phase CoMn2O4, thus accelerating reaction. Among all the as-prepared catalysts, CMO/LMO-0.5 exhibited admirable ethane removal efficiency with a T90 of 365 °C, a reaction rate of 0.46 mmol·g−1·h−1, a TOF value of 0.64 mmol·g−1·h−1, and excellent hydrothermal stability and reusability. Moreover, according to in situ DRIFTS, a possible pathway was proposed. This work can rationalize an alternative approach to develop an active catalyst for short-chain alkanes catalytic combustion or other catalytic systems.

Large-Eddy Simulation of Supersonic Combustion in a Mach 2 Cavity Model Scramjet Combustor

In this study, we report on reactive large-eddy simulations (LESs) of flow and combustion in the U.S. Air Force Research Laboratory Research Cell 19 cavity-based scramjet combustor. This case involves the combustion of ethylene that is injected into a cavity. It has previously been studied experimentally with multiple techniques, including particle image velocimetry, hyperspectral imagining, and laser-induced breakdown spectroscopy, as well as numerically using hybrid Reynolds-averaged Navier–Stokes/LES. Here, we build on the existing knowledge and provide an in-depth investigation of the flow and combustion using a pure LES approach. A range of fuel injection rates are studied, as well as the nonreacting case. This way we can disseminate how different amounts of combustion and the associated volumetric expansion affect the shear layer above the cavity, the recirculation zone, and the downstream shock train. For example, an additional shock train emerges from the start of the cavity when combustion is present, and it grows in intensity with increasing fueling rate from 50 to 110 slpm. For the cases studied, good agreement is found between the LES and experiments. The primary flow features, such as the shock train, primary and secondary cavity recirculation regions, and shear-layer lift due to exothermicity, are found to evolve similarly with increasing fueling rate in the experiments and the LES. This enables the use of the more complete LES results to further investigate the flow and combustion physics.

Reaction Rate Rules of Intramolecular H-Migration Reaction Class for RIORIIOO·Radicals in Ether Combustion.

The intramolecular H-migration reaction of RIORIIOO· radicals constitute a key class of reactions in the low-temperature combustion mechanism of ethers. Despite this, there is a dearth of direct computations regarding the potential energy surface and rate constants specific to ethers, especially when considering large molecular systems and intricate branched-chain structures. Furthermore, combustion kinetic models for large molecular ethers generally utilize rate constants derived from those of structurally similar alcohols or alkane fuels. Consequently, chemical kinetic studies involve the calculation of energy barriers and rate rules for the intramolecular H-migration reaction class of RIORIIOO· radicals, which are systematically conducted using the isodesmic reaction method (IRM). The geometries of the species participating in these reactions are optimized, and frequency calculations are executed using the M06-X method in tandem with the 6-31+G(d,p) basis set by the Gaussian 16 program. Moreover, the M06-2X/6-31+G(d,p) method acts as the low-level ab initio method, while the CBS-QB3 method is utilized as the high-level ab initio method for calculating single-point energies. Rate constants at the high-pressure-limit are computed based on the reaction class transition state theory (RC-TST) by ChemRate program, incorporating asymmetric Eckart tunneling corrections for intramolecular H-migration reactions across a temperature range of 500 to 2000 K. It was found that the isodesmic reaction method gives accurate energy barriers and rate constants, and the rate constants of the H-migration reaction for RIORIIOO· radicals diverge from those of comparable reactions in alkanes and alcohol fuels. There are significant disparities in energy barriers and rate constants across the entire reaction classes of the H-migration reaction for RIORIIOO· radicals, necessitating the subdivision of the H-migration reaction into subclasses. Rate rules are established by averaging the rate constants of representative reactions for each subclass, which is pivotal for the advancement of accurate low-temperature combustion reaction mechanisms for ethers.

Mechanistic insights into ethylene catalytic combustion and CO2 formation in vinyl acetate synthesis

Vinyl acetate is a crucial monomer for the production of polyvinyl alcohol and polyvinyl acetate, with extensive applications in the photovoltaic and pharmaceutical industries. CO2 is the primary by-product in the synthesis of vinyl acetate, significantly burdening the separation process and impacting the ecological environment. Reducing CO2 generation at the source is an effective solution. In the vinyl acetate synthesis process, CO2 is primarily produced through the catalytic combustion of ethylene. However, the reaction mechanism of ethylene catalytic combustion on Pd-based catalysts in vinyl acetate synthesis remains incomplete, with existing mechanisms presenting certain limitations. Therefore, further investigation into the reaction mechanism of ethylene catalytic combustion leading to CO2 formation on Pd-based catalysts is necessary.This study employs density functional theory to calculate the reaction mechanism of ethylene catalytic combustion on the Pd(100) surface, obtaining elementary reaction kinetics data. Based on these data, the kinetic Monte Carlo method was used to investigate the reaction process of ethylene catalytic combustion, revealing the predominant pathway for CO2 formation. This research provides targeted strategies for catalyst modification. It aims to improve the understanding of the reaction mechanism of ethylene catalytic combustion in vinyl acetate synthesis, reduce the consumption of ethylene in by-product formation, enhance vinyl acetate yield and ethylene utilization, and ultimately decrease CO2 production, thereby lowering carbon emissions.

Influence of Dimethyl Ether Combustion in the Compression-Ignition Engine on the Peak and Effective Measures of the Vibroacoustic Process and Toxic Compounds Emission

Influence of Dimethyl Ether Combustion in the Compression-Ignition Engine on the Peak and Effective Measures of the Vibroacoustic Process and Toxic Compounds Emission

Soot evolution in ethylene combustion catalyzed by electric field: experimental and ReaxFF molecular dynamics studies

In this study, an electric field (E-field) was used to regulate the formation and oxidation of soot in combustion. In the procedure, an E-field is applied to the ethylene non-premixed flame, the flame is stretched horizontally and the flame height is reduced. By comparing the partially premixed flame to eliminate the effect of the E-field on the increase of combustion temperature caused by premixing, transmission electron microscope (TEM) detection revealed that the soot particles were more dispersed in the action of E-field, the “core-shell” structure of soot disappeared, and the markedly improved oxidation rate of soot in the flame. The evolution process of soot in ethylene combustion was studied by reactive molecular dynamics. The 9 ns simulation was performed at E-field strengths of 0, 0.001, and 0.1 V/Å by three successive modelings. The results showed that the E-field reduced the growth of the largest molecule in the system and increased the coagulation time of the initial soot particles. With increasing E-field strength, the “core-shell” structure of soot gradually broke. An increased hydrogen-carbon ratio and decreased number of six-membered rings are the internal factors for the more scattered structure of soot, which allows the soot to be more easily oxidized.

Investigation on combustion and emission characteristics of diesel polyoxymethylene dimethyl ethers blend fuels with exhaust gas recirculation and double injection strategy

As a kind of renewable and high oxygen content fuel, polyoxymethylene dimethyl ether (PODE) can be added in diesel to realize energy saving and emissions reduction. To evaluate the combustion and emission characteristics of a diesel engine fueled with diesel and diesel/PODE mixtures, exhaust gas recirculation (EGR) and main-pilot injection strategies with various injection timings were applied. PODE was blended with diesel by volume to form mixtures which were marked as D100 (pure diesel), D90P10 (90% diesel + 10% PODE), and D80P20 (80% diesel + 20% PODE). The results showed that the ignition delay (ID) and combustion duration (CD) of D80P20 were the shortest because of the highest cetane number (CN) and high oxygen content of PODE, indicating more concentrated heat release. At low and medium loads, D80P20 achieved the highest peak heat release ratio (PHRR) and peak combustion temperature (PCT) among the three fuels, and it was 14.3% and 3.6% higher than those of D100. PODE blending with diesel can significantly reduce particulate matter (PM) and D80P20 has the lowest PM emissions at all loads. Compared with D100, both PM and nitrogen oxide (NOx) emissions of PODE blends decreased simultaneously with 20% EGR at all loads. With the increase of pilot-main interval, the ID and CD of all test fuels increased, while the NOx and PM emissions decreased. The conclusions of the present research provide a state of the application in light-duty engines fueled with diesel/PODE blends in future work.

Pyrolysis and oxidation mechanisms of ethylene and ethanol blended fuel based on ReaxFF molecular dynamics simulation

To gain detailed atomic-level insights into the reaction mechanisms associated with the oxy-fuel combustion of ethylene and ethanol, ReaxFF reactive force field molecular dynamics simulations were performed to analyze the behavior of their high-temperature pyrolysis and oxidation. Results showed that the main reaction of pure ethylene involves the formation of long carbon chains by C–C polymerization in an oxygen-free environment. The polycondensation-cyclization of long carbon chains significantly contributes to the formation of polycyclic aromatic hydrocarbons (PAHs). The addition of ethanol enriches the initial reaction pathways of ethylene. For instance, ethanol participates in the following reactions: C2H4 + C2H6O → C4H10O, C2H6O + C2H4 → C2H5 + C2H5O, and C2H6O + C2H4 → C2H5 + H2O + C2H3. Ethanol inhibits the growth of long carbon chains, with a more pronounced effect at higher ethanol concentrations. In an oxygen atmosphere, the decay rate of ethylene decreases significantly, and its main reaction pathway involves dehydrogenation and oxidation with the assistance of OH, HO2, H, and O2. The final products are released in the form of CO, CO2, and H2O. In addition, the formation of soot particles is mainly divided into three steps: (i) ethylene aggregates to form long carbon chains, (ii) rearrangement and cyclization of long carbon chains, and (iii) growth of PAHs.

Simulation of DME-O2 Combustion in a Hollow Cone Impinging Jet Combustor for Direct-Fired Supercritical CO2 Power Cycle

ABSTRACT Combustion is critical in the direct-fired supercritical CO2 power cycle. A hollow cone impinging jet combustor is designed. Instead of methane, dimethyl ether is used as the fuel for the direct-fired supercritical CO2 cycle, with a higher hydrocarbon ratio and oxygen. The dimethyl ether combustion process is simulated by Fluent, based on the k-ε turbulence model and Eddy-Dissipation Concept combustion model, combined with the dimethyl ether combustion mechanism. The effects of the CO2 recycling ratio, the excess oxygen coefficient, and in-combustor pressure are investigated to support improving combustion performance. The results indicate that the recycled CO2 intensifies the movement of the mixture in the combustor, reduces the peak temperature, and makes temperature distribution more uniform. As the excess oxygen coefficient increases, the peak temperature is enhanced, and the combustion is more sufficient. The effect of in-combustor pressure is complex. On the one hand, increasing in-combustor pressure reduces the jet penetration and inhibits the contact between dimethyl ether and O2, leading to a lower peak temperature. On the other hand, it prolongs the residence time of the high-temperature exhaust, making the reaction between dimethyl ether and O2 more sufficient. The optimal operating condition of the combustor is a CO2 recycling ratio of 0.95, an excess oxygen coefficient of 1.20, and an in-combustor pressure of 30 MPa. Moreover, the obtained combustion products parameters, such as temperature, component concentration, and mass flow rate, can guide the performance analysis for the direct-fired supercritical CO2 power cycle.

Investigation of the Combustion Properties of Ethylene in Porous Materials Using Numerical Simulations

As industrial modernization advances rapidly, the need for energy becomes increasingly urgent. This paper aims to enhance the current burner design by optimizing the combustion calorific value, minimizing pollutant emissions, and validating the accuracy of the burner model using experimental data from previous studies. The enhanced porous medium burner model is used to investigate the burner’s combustion and pollutant emission characteristics at various flow rates, equivalence ratios, combustion orifice sizes, and porosity of porous media. In comparison with the previous model, the combustion traits during ethylene combustion and the emission properties of pollutants under various operational circumstances have been enhanced with the enhanced porous medium burner model. The maximum temperature of ethylene combustion in the enhanced model is 174 k higher than that before the improvement, and the CO emissions are reduced by 31.9%. It is believed that the findings will serve as a guide for the practical implementation of porous media combustion devices.

The kinetics and warm flame chemistry associated with radiative extinction of spherical diffusion flames

Several studies have found that microgravity diffusion flames with sufficient heat loss cool until they extinguish at a critical temperature near 1130 K. In this work, the associated chemical kinetics are explored for spherical diffusion flames burning ethylene. The flames are simulated with a transient numerical model with detailed chemistry, transport, and radiation. This incorporates the UCSD mechanism with 57 species and 270 reactions. Species concentrations, reaction rates, and heat release rates are examined. Upon ignition, the peak temperature is above 2000 K, but this decreases until extinction due to radiative losses. This allows the chemistry to be studied over a wide range of peak temperatures for the same fuel and oxidiser. When the peak temperature is high, the dominant chemistry is similar to that for typical normal-gravity ethylene diffusion flames. There are two distinct zones: an ethylene pyrolysis zone and an oxidation zone, and negligible reactant leakage. The ethylene mainly reacts with H and OH. The concentration of OH in the ethylene pyrolysis zone is high due to the long residence times and reactions of CO2 and H2O with H. As the flame cools and the peak temperature approaches the critical extinction temperature, there is increased reactant leakage leading to higher O, OH, and HO2 concentrations on the fuel side. Most reactions shift towards the oxidiser side and there is large overlap between the two zones. Reactions involving HO2 become more significant and the large consumption rates of H by HO2 increase the concentrations of OH and O on the fuel side. The appearance of warm flame chemistry delays extinction but is not sufficiently exothermic to prevent it.

An experimental and molecular simulation study on the soot formation characteristics and mechanism in hydrogen-ammonia blended ethylene combustion

Extinction measurement and thermophoretic sampling techniques were employed to investigate the soot formation characteristics in H2-NH3 blended C2H4 combustion. And the formation mechanism of benzene (A1) was analyzed using reactive molecular dynamics simulation (ReaxFF MD), unveiling the chemical coupling effects on soot formation at the molecular level. As the hydrogen/ammonia (H2/NH3) ratio decreases, the flame height decreases gradually, the flame brightness noticeably darkens, and the dark non-sooting core continuously increases. The maximum of soot volume fraction (fvmax) gradually decreases and shifts from the flame wing towards the flame centerline. Addition of H2-NH3 leads to an increase in the proportion of small-sized fringes and fringe tortuosity, resulting in an increase in the oxidation activity and a decrease in the fv. The largest soot particle contains a small amount of nitrogen atom (N). Some of these N atoms replace hydrogen atom (H) to bond with carbon ring, while others substitute for carbon atom (C) to form nitrogen ring, ultimately resulting in nitrogen-containing polycyclic aromatic hydrocarbons (PAHs) and nitrogen-containing soot. The reduction in the H2/NH3 ratio leads to a reduction in C in the largest soot particle, which more effectively inhibits soot formation and graphitization. On the other hand, it increases the N and nitrogen ring in the largest soot particle. It is possible that the increase in NH3 proportion favors N in competition with H for active sites on soot particles. A1-+H↔A1 is the most crucial reaction pathway of A1 formation. As the H2/NH3 ratio increases, H2 concentration significantly rises, leading to an enhancement in the forward reaction rate. Furthermore, the competition for H between H2 and NH3 by NH3+H↔NH2+H2 results in a chemical coupling effect on soot formation.

Chemical kinetics analysis of ammonia/dimethyl ether combustion under water addition conditions

Ammonia has gained considerable interest as a high-energy-density, zero-carbon fuel with potential as a clean energy source for future applications. Nonetheless, its widespread industrial use is constrained by challenges associated with low flammability and elevated levels of NOx emissions. To address the low flammability issue, this study introduces dimethyl ether (DME), a fuel known for its high laminar flame speed, into pure ammonia combustion systems. Moreover, we implement moderate and low-temperature diffusion combustion by incorporating water vapor into high-temperature air, aiming to minimize NOx emissions. We examined the effects of NH3/DME and water vapor mixing ratios on variables including laminar flame speed, key free radicals, NO emissions, and reaction pathways. Computational simulations were conducted using the PREMIX module within Chemkin Pro based on a modified Meng model, which was initially validated against experimental data. Our results indicate that increasing DME concentrations lead to a notable rise in laminar flame speed and the concentration of O, H, and OH radicals. Concurrently, NO concentrations also increased due to DME's oxygen-bearing nature, which enhances the oxidation of N-containing radicals. Conversely, elevating the water vapor content results in reduced laminar flame speed, decreased free radical peaks, and diminished NO emissions. Rate of production analyses reveal that specific reactions, such as HNO + HNO + H2, HNO + OHNO + H2O, and NH + ONO + H, significantly contribute to NO formation by consuming active O, H, and OH radicals.

Surface exposure engineering on LaMnO3@Co2MnO4 for high-efficiency ethane catalytic combustion

Higher specific surface area and abundant surface oxygen vacancies are considered to be essential to the catalytic combustion. Herein, we elaborately fabricated an innovative catalyst on the basis of LaMnO3@Co2MnO4 under a controllable selective dissolution (SD) treatment for ethane catalytic combustion. La element in perovskite could effectively protect the spinel system as a sacrifice, with MnO2 covering on the spinel surface, thereby enhancing the activity and stability. In combination with XPS, in-situ DRIFT and various characterization results, this acid corrosion could provide induce better reducibility, larger specific surface area, higher Mn4+ and Co3+content and more oxygen vacancies, which played a significant role in promoting the adsorption, activation and decomposition of ethane. Among all as-prepared catalysts, the optimal performance for catalytic ethane combustion was achieved on LMO@CMO-10 catalyst. The T90 of LMO@CMO-10 was 341 °C under space velocity of 80,000 mL·g−1·h−1. This work not only fabricated the catalyst system with higher specific surface area and more oxygen vacancy by SD method, but also provided a potential strategy for the preparation of highly active catalysts.

Application of absorption-line blackbody distribution functions for H2O-CO2 mixtures for the spectral integration of the radiative transfer equation with the SLW model

This study presents the generation and evaluation of absorption-line blackbody distribution functions for mixtures (ALBDF-M) of CO2 and H2O. These functions are employed in the spectral integration of the radiative transfer equation in the framework of the spectral line-based weighted-sum-of-gray-gases (SLW) model. The proposed approach avoids the need to model the mixture of gases when dealing with ALBDFs obtained for pure H2O and CO2 species, which is the methodology currently adopted in the SLW literature. The ALBDF-M can be used with any development of the SLW model to manage local variations of the thermodynamic state conditions. In the present study, both the rank (RC-) and the locally correlated (LC-) SLW methodologies are employed with the ALBDF-M for an uncouple solution of an axisymmetric field that is representative of the combustion of ethylene diluted with H2O. Comparisons with line-by-line (LBL) solutions show that using the ALBDF-M provides an improvement in the accuracy when compared to the standard methodology to combine the ALBDFs generated for CO2 and H2O individually.

Influence of bromination arrangement and level on the formation of polybrominated dibenzo-p-dioxins and dibenzofurans from pyrolysis and combustion of polybrominated diphenyl ethers: Mechanisms and kinetics

Controlling the emission of polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs) presents a huge challenge in the thermo-chemical conversion of halogenated waste. It is crucial to understand the formation of PBDD/Fs to effectively control their emissions. This paper utilizes density functional theory calculations to comprehensively explore the mechanisms and kinetics of PBDD/Fs formation using 65 polybrominated diphenyl ethers (PBDEs) with varying bromination arrangements and levels. The study uncovers two new pathways for the formation of PBDFs from PBDEs, i.e., two-step H2 elimination and ether-ketone isomerization at ortho-C(H) sites. These pathways are applicable to PBDEs with specific bromination arrangements. In the case of some PBDEs, their initial energy barriers are comparable to the generally accepted direct HBr elimination. It is found that low-brominated PBDEs have a higher risk of forming PBDD/Fs, while high-brominated PBDEs are more likely to break ether bonds and generate polybromobenzenes. The study also investigates the effects of polymer materials and metals on the formation of PBDD/Fs from PBDEs to explain the high yield of PBDD/Fs in the co-treatment of PBDEs with polymers and metals. The involvement of polymers and metals significantly reduces the energy barriers for the formation of PBDD/F precursors, namely ortho-phenyl-type radicals, accelerating the formation of PBDD/Fs. This study markedly advances the present understanding of the transformation of PBDEs into PBDD/Fs and provides theoretical guidance for reducing pollutant emissions in the thermal treatment and cleaner conversion of PBDE-containing waste.

A comprehensive experimental and kinetic modeling study of methyl tert-butyl ether combustion

A comprehensive understanding of the combustion chemistry of methyl tert‑butyl ether (MTBE) is of key importance in its application as an additive in gasoline fuels. Ignition delay times (IDTs) of MTBE/air mixtures have been measured in both a high-pressure shock tube (HPST) and in a rapid compression machine (RCM) at equivalence ratios of 0.5, 1.0, and 2.0 in air, at pressures of 10 and 30 bar over the temperature range 600 – 1350 K. Species profiles for MTBE oxidation were obtained in a jet-stirred reactor (JSR) at 1 bar, at equivalence ratios of 0.5, 1.0, and 2.0 in the temperature range 700 – 1100 K.A detailed reaction mechanism, comprising 813 species and 4319 reactions, has been developed and predicts well all of the experimental data obtained in this work and also texisitng literature data. Pressure- and temperature-dependent rate constants for the MTBE unimolecular elimination reaction producing isobutene and methanol were calculated using high-level ab-initio calculations. A sensitivity analysis reveals that this elimination reaction is important, and significantly inhibits fuel reactivity at temperatures above 1300 K. At intermediate temperatures (850 – 1300 K), the reaction MTBE + ȮH = TĊ4H8OCH3 + H2O plays a crucial role in promoting the reactivity of MTBE oxidation, whereas the reaction MTBE + ȮH = TC4H9OĊH2 + H2O is the most inhibiting reaction. At low temperatures (600 – 850 K), the isomerization reaction of TC4OCȮ2–1 ⇌ TĊ4OCO2H-2 significantly promotes the reactivity. Conversely, the reaction 2TC4OCȮ2–1 ↔ 2TC4OCȮ-1 + O2 inhibits reactivity the most. The NTC behavior in MTBE oxidation can be explained by the competition between the reactions involving the formation and consumption of cyclic ethers from TĊ4H8OCH3 radicals and the reactions associated with the formation and consumption of carbonyl hydroperoxide species.

Comparison of the performance of ethylene combustion mechanisms

Ethylene is a key intermediate in the combustion and pyrolysis of larger hydrocarbons. A large set of literature experimental data covering wide ranges of conditions on ethylene combustion was collected: ignition delay times measured in shock tubes (1160 data points in 114 data series) and rapid compression machines (83/5); concentration measurements carried out in jet-stirred reactors (1586/157) and flow reactors (649/59); and laminar burning velocities (882/59). 14 detailed reaction mechanisms were investigated using the collected experimental data. The results show significant differences between the performances of the various mechanisms. The four best-performing mechanisms are Aramco-2.0-2016, Aramco-3.0-2018, Yang-2020 and NUIGMech-1.1-2020 based on all included experimental data. The best-performing model Aramco-2.0-2016 was further investigated by local sensitivity analysis. Several reaction steps were found to be important for simulating the experiments: many reactions of the hydrogen, syngas and C1 hydrocarbons oxidation systems, furthermore reactions C2H3 + O2 = CH2CHO + O and C2H4 + OH = C2H3 + H2O which are specific for ethylene combustion.

Revealing the Nature of Active Oxygen Species and Reaction Mechanism of Ethylene Epoxidation by Supported Ag/α-Al2O3 Catalysts.

The oxygen species on Ag catalysts and reaction mechanisms for ethylene epoxidation and ethylene combustion continue to be debated in the literature despite decades of investigation. Fundamental details of ethylene oxidation by supported Ag/α-Al2O3 catalysts were revealed with the application of high-angle annular dark-field-scanning transmission electron microscopy-energy-dispersive X-ray spectroscopy (HAADF-STEM-EDS), in situ techniques (Raman, UV-vis, X-ray diffraction (XRD), HS-LEIS), chemical probes (C2H4-TPSR and C2H4 + O2-TPSR), and steady-state ethylene oxidation and SSITKA (16O2 → 18O2 switch) studies. The Ag nanoparticles are found to carry a considerable amount of oxygen after the reaction. Density functional theory (DFT) calculations indicate the oxidative reconstructed p(4 × 4)-O-Ag(111) surface is stable relative to metallic Ag(111) under the relevant reaction environment. Multiple configurations of reactive oxygen species are present, and their relevant concentrations depend on treatment conditions. Selective ethylene oxidation to EO proceeds with surface Ag4-O2* species (dioxygen species occupying an oxygen site on a p(4 × 4)-O-Ag(111) surface) only present after strong oxidation of Ag. These experimental findings are strongly supported by the associated DFT calculations. Ethylene epoxidation proceeds via a Langmuir-Hinshelwood mechanism, and ethylene combustion proceeds via combined Langmuir-Hinshelwood (predominant) and Mars-van Krevelen (minor) mechanisms.

Adaptation of the Kinetical Scheme to Ethylene Combustion Conditions at Temperatures Above 1200 K

In the paper authors present original methods for analyzing the kinetic scheme and reaction rateconstants for calculation of the ignition delay time and the laminar velocity of the combustion wave forC2H4–O2–Ar and C2H4-air mixtures. The kinetic scheme under consideration will further be applied inproblems of plasma-assisted combustion in a supersonic flow using a discharge. After made changes to thereaction system, a good agreement between the calculation results and experimental data was obtained.