Reaction Mechanism Of Pyrolysis Research Articles

Kinetic reaction mechanism of lignocellulosic biomass oxidative pyrolysis based on combined kinetics

The kinetics knowledge of lignocellulosic biomass decomposition is essential to develop efficient thermochemical conversion technology. However, the simplification of reaction mechanisms in existing oxidative pyrolysis studies largely compromises the application of kinetic models. To explore more exact kinetic parameters and reaction mechanism of lignocellulosic biomass oxidative pyrolysis, an updated oxidative pyrolysis kinetic model (seven-step reaction combined kinetics model) coupled with an optimization algorithm is proposed. Based on a series of thermogravimetric experiments in an air atmosphere, the extra oxidative pyrolysis kinetic parameters are obtained by the Shuffled Complex Evolution method. The proposed kinetic model is validated based on the degradation process of each component (hemicellulose, cellulose, and lignin). Furthermore, the obtained kinetic parameters are applied to predict the oxidative pyrolysis behavior, and the predicted mass loss rate is in good agreement with the experimental data. Eventually, according to the key combined kinetics parameters, it is found that the oxidative pyrolysis mechanisms of hemicellulose, cellulose, and lignin correspond to the power law, nucleation & growth, and chemical reaction order, respectively, while the combustion of char corresponds to the reaction order mechanism.

Characterization of pyrolysis behavior for rigid polyurethane foam wastes with different densities through TGA-FTIR-DSC-MCC and Hill Climbing Optimization methods

Pyrolysis technology is one of the most effective thermal treatment methods recycling rigid polyurethane foam (RPUF) waste. To optimize pyrolysis recovery efficiency, quantifying the pyrolysis reaction kinetics and the heat required for the thermal treatment process is critical. This work focuses on establishing a systematic methodology to quantify pyrolysis reaction kinetics and thermodynamics for RPUF waste. RPUF waste with two different densities (RPUFρ100 and RPUFρ45) were investigated using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) under anaerobic atmosphere to measure mass and heat flow information. The obtained data were inversely analyzed using a numerical framework known as ThermaKin2Ds. Pyrolysis reaction mechanisms with four and three consecutive first-order reactions were developed to reproduce the TGA data for RPUFρ100 and RPUFρ45, respectively. The Hill Climbing Optimization Algorithm was employed to adjust the reaction kinetics for an improved agreement between the ThermaKin2Ds-reproduced and experimental data. Based on the heat flow data from DSC tests, the specific heat capacity of each condensed-phase component was determined by using the inverse modeling method. Additionally, the micro-scale combustion calorimeter was used to generate the heat release data that served as the target data for inversely determining the heats of complete combustion, hc, of each pyrolyzate. The established pyrolysis reaction models was further validated by predicting the TGA results collected under different external heating conditions. Subsequently, the generated combustion-inhibiting gases (CO2) and combustion-promoting gases (olefins, alkanes, carboxylic acids, etc.) were characterized through TGA coupled with Fourier-transform infrared spectroscopy (TG-FTIR). This allowed us to elucidate the gas-phase combustion phenomena observed in MCC experiments. This work provides a core set of parameters for optimizing the thermal treatment conditions of RPUF waste.

Pyrolysis and combustion reaction mechanisms of methyl palmitate with ReaxFF-MD method

As a substitute for fossil fuel, methyl palmitate (C17H34O2) has important scientific and practical significance to study its pyrolysis and combustion mechanism. In this paper, the ReaxFF-MD method is used to research the reaction mechanism and main products of C17H34O2. The effects of temperature and O2 on the decomposition, main products and reaction paths of C17H34O2 are analyzed to determine its reaction mechanism. The results show that the reaction activation energies of C17H34O2 in pyrolysis and combustion are 201.76 kJ/mol and 139.07 kJ/mol, respectively. The effect of temperature on C17H34O2 is greater than O2 on C17H34O2 at higher temperature. The basic reaction paths for the initial decomposition of C17H34O2 is that the CC, CO, and CH bonds are broken into smaller intermediates. In addition, the detailed distribution and generation paths of the main products C2H4, H2, H2O, CH2O, and so on are depicted to construct the reaction mechanism of C17H34O2.

Experimental and theoretical study of cyclopropanated fuel exo,exo-Tetracyclo[3.3.1.02,4.06,8]nonane pyrolysis in a jet-stirred reactor

Exo,exo-Tetracyclo[3.3.1.02,4.06,8]nonane (exo-TCN), a kind of cyclopropanated fuel with high tension three-membered ring, which has the characteristics of high density, high net heat of combustion and good low-temperature performance, is a potential high-energy-density liquid fuel. To deeply understand its combustion behavior, and lay a foundation for practical application, detailed experimental and theoretical study is necessary. The pyrolysis of exo-TCN was investigated in a jet-stirred reactor at a temperature range of 500–1010 K under atmospheric pressure with a residence time of 2 s. 54 products and intermediates ranging from m/z = 2–204 were identified and quantified by synchrotron vacuum ultraviolet photoionization mass spectrometry and online gas chromatography, the major products were hydrogen, ethylene, benzene, methane, propene, toluene and styrene. The potential energy surfaces of exo-TCN unimolecular decomposition reactions were calculated by quantum chemistry at CBS-QB3 level. It is found that the pyrolysis of exo-TCN experiences three stages. In the first stage, exo-TCN isomerizes into Tricyclo[3.3.1.02,4]non-6-ene (TCN-6) by ring expansion of the three-membered ring. In the second stage, TCN-6 generates two main isomers through ring expansion reactions, and decomposes into pyrolysis products. The third stage is the secondary reaction of the intermediate products. Finally, combined with the experimental results and theoretical calculation, the possible reaction mechanism of exo-TCN pyrolysis was proposed, and the related reaction rate constants were calculated.

Pyrolysis characteristics and reaction mechanism of intumescent fire-retardant coating with thermogravimetry/Fourier transform infrared analysis

A research of intumescent fire-retardant coating (IFRC) pyrolysis characteristics and reaction mechanism was conducted by thermogravimetric analysis coupled with Fourier transform infrared spectrometry analysis at various heating rates. The results demonstrate that the pyrolysis process of IFRC could be separated into two stages. In stage I, which occurs within the temperature range of 300–800 K, there is a mass loss of 8.5 %. The main gases released during this stage are NH3 and CH4. Moving on to stage II, which takes place within the temperature range of 800–1200 K, there is a significant mass loss of 42.9 %. The main gases released during this stage are CO2 and H2O. Through the use of FTIR spectra, the production amount of main four components ranked as follows: CO2 > H2O > CH4 > NH3. Especially, the reaction expressions were further speculated and proposed. Subsequently, the two aforementioned stages were utilized based on both model-free and model-fitting methods to ascertain the possible reaction mechanism.

Pyrolysis kinetics and thermodynamic behavior of pseudo components of raw and torrefied maple wood

ABSTRACT In this work, pyrolysis kinetics and thermodynamic behavior of pseudo components (PCs) of raw and torrefied maple wood (MW) were studied. The MW torrefaction experiments were conducted at 240°C and the pyrolysis process was performed under three distinct heating rates. Through the deconvolution procedure, three PCs, i.e. pseudo-hemicellulose (PC-HC), pseudo-cellulose (PC-CL), and pseudo-lignin (PC-LG), were identified. The activation energy (E α ) of PCs were evaluated using the Starink method, and the pyrolysis reaction mechanisms were analyzed using the Criado’s master plot method. Furthermore, three thermodynamic parameters were also calculated and discussed. Results showed that after torrefaction, the PC-HC content dropped from 47.30% to 7.90%, while the PC-CL and PC-LG contents increased from 33.67% to 55.72% and from 19.03% to 36.38%, respectively. The average E α of raw MW PC-HC, PC-CL and PC-LG were 114.56, 117.12 and 116.02 kJ/mol, respectively, whereas they were 92.86, 103.82 and 159.26 kJ/mol for torrefied PCs, respectively. The master plot results suggested that the pyrolysis of MW PCs involved different order-based models. In addition, the thermodynamic analysis revealed that the torrefied PC-HC required slightly less heat energy during pyrolysis. All these observations can be conducive to better understand the pyrolysis mechanisms of raw and torrefied MW PCs.

Thermal degradation properties, kinetic, thermodynamic and reaction mechanism of pyrolysis of biomass shells: pistachio, almond, walnut and hazelnut as bioenergy potential

Thermal degradation properties, kinetic, thermodynamic and reaction mechanism of pyrolysis of biomass shells: pistachio, almond, walnut and hazelnut as bioenergy potential

Stepped pyrolysis: A novel approach for enhanced adsorbency and carbon in Pigeon pea stalk char

This article introduces a novel technique, stepped pyrolysis, for thermal degradation of biomass. The differential thermogram (DTG) of pigeon pea stalk was deconvoluted into their intrinsic bioconstituents and these deconvoluted peaks were used to decide the different stages or steps to finalize the thermal protocol to be executed for stepped pyrolysis. The stepped pyrolysis and traditional pyrolysis of pigeon pea stalk were conducted and the characterisation of outputs was done. The obtained result for the char produced by the stepped pyrolysis method showed a reduction of 5% in the volatile matter and an increment of 5% in fixed carbon content, over the product of traditional pyrolysis. The stepped pyrolysis increased the iodine number by 17% while reducing the methylene blue values by 31% as compared to the traditional pyrolysis. A significant reduction in activation energy by 21% for FWO, 18% for KAS, and 26% for Starink methods were recorded for stepped, over traditional pyrolysis. The pyrolysis reaction mechanism of stepped and traditional pyrolysis methods followed the second-order (F2) and two-dimensional diffusion model (D2). The stepped pyrolysis method produced a better quality product with more micropores and carbon-rich char than the traditional method.

Pyrolysis characteristics, reaction mechanisms and gas emission of organic fireproof plugging materials by TG-FTIR-MS

Pyrolysis characteristics, reaction mechanisms and gas emission of organic fireproof plugging materials by TG-FTIR-MS

Investigations into extra-heavy crude oil pyrolysis under non-isothermal conditions: thermal characteristics, kinetics, and thermodynamic parameters

This study comprehensively investigated the pyrolysis characteristics, kinetics, and thermodynamic parameters of extra-heavy oil through thermogravimetry (TG) experiments. The TG results revealed a two-stage pyrolysis process, consisting of light-temperature pyrolysis (LTP) and high-temperature pyrolysis (HTP), in which the HTP was the primary mass loss interval, contributing roughly 53.5% of mass loss from 370 to 500 °C. The pyrolysis kinetics were obtained using Ozawa-Flynn-Wall (OFW) and Friedman methods. The results revealed that the main pyrolysis reaction mechanism shifted from volatilization to thermal cracking while the conversion degree exceeded 0.35. The thermodynamic parameters, including enthalpy (ΔH), Gibbs free energy (ΔG), and entropy (ΔS), were also calculated. The thermodynamic features showed that the pyrolysis process absorbed large amounts of energy to change the main reaction mechanism in the range of α = 0.4–0.6, and altered from an organized to a disordered state due to the disruption of intramolecular structure induced by the formation of coke while the conversion degree exceeded 0.6. These findings have the potential to offer a thorough comprehension of the pyrolysis mechanism of extra-heavy oil.

Comprehensive investigation on fast pyrolysis of waste Lotus shells to produce valuable products: Pyrolysis characteristics, reaction mechanism and economic analysis

Lotus shells (LS) represent an abundant, underutilized renewable resource with significant potential for producing bio-based fuels and chemicals. Pyrolysis emerges as an effective means to maximize the value derived from LS waste. This study assessed the behavior, kinetics of LS pyrolysis for bioenergy production through thermogravimetric analysis (TGA), model-free and model methods. The product distribution resulting from LS fast pyrolysis and the physicochemical properties of the derived products were comprehensively investigated. A plausible reaction mechanism for LS pyrolysis was proposed, followed by an estimation of the associated costs for bioenergy production through pyrolysis. The activation energy (Eα) for LS calculated through Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS), and Friedman (FR) methods was 197.36 kJ/mol, 193.66 kJ/mol, and 197.16 kJ/mol, respectively. The kinetic reaction model for LS pyrolysis was represented by the equation f(α) = α−26.59(1-α)12.35[-ln(1-α)]−27.26, indicating the dominance of a diffusion model and nucleation mechanism in the LS pyrolysis process. Notably, the fast pyrolysis bio-oil derived from LS mainly comprised phenols (34.73 % at 300 °C), acids (42.33 % at 600 °C), and nitrogenous compounds (27.40 % at 800 °C), and the gaseous products primarily consisted of H2, CH4, CxHy, CO, and CO2. Biochar derived from LS exhibited abundant functional groups and mesoporous structure, and its moderate C/N ratio and low H/C ratio indicated potential for soil remediation. Furthermore, the high heating value (21.55–27.01 MJ/kg) of LS biochar exceeded that of Zhaotong lignite, demonstrating its favorable combustion characteristics. This study lays the theoretical foundation for the efficient treatment and high-value utilization of Lotus shells.

Effects of pressure and heating rate on coal pyrolysis: A study in simulated underground coal gasification

Underground coal gasification (UCG) is a promising technology which in-situ converts coal into fuel gases through controlled chemical reactions. In order to precisely control coal pyrolysis and increase the char yield, it is vital to understand the influences of operating factors such as heating rate and pressure, on coal pyrolysis. In this study, the effects of heating rate and pressure on the char formation of bituminous coal pyrolysis are investigated. The reaction mechanism of coal pyrolysis and the solid-state kinetic model are firstly reviewed. Subsequently, thermal experiments are conducted to study the effects of heating rate and pressure on coal pyrolysis characteristics. Moreover, the connection between the dominant coal pyrolysis reaction type and corresponding solid-state kinetic model is revealed. An empirical model of coal pyrolysis rate, pressure, and heating rate is also developed, which can be used to quantitatively predict pyrolysis rates under varying heating rate and pressure conditions. The results show that the optimal heating rate for char generation is at around 10 °C/min. On the other hand, when the pressure exceeds 2 MPa, it will enhance the char production by obstructing the physical release of volatiles and has insignificant impact on the reaction type. This study contributes to our understanding of the coal pyrolysis mechanism, and the proposed empirical model can provide valuable insights for optimizing operating parameters during UCG process.

Reaction mechanism and microkinetics of 1-hexene catalytic pyrolysis on HZSM-5: A first-principles study

Catalytic pyrolysis is an important way of integrating refining and petrochemical processes, as it efficiently converts FCC gasoline into propylene. Enhancing the selectivity of propylene production remains a major focus in this field. To enhance the selectivity of propylene in catalytic pyrolysis of olefin, the reaction mechanism, the microkinetics of the catalytic pyrolysis of 1-hexene, as well as the effect of acid strength were investigated using the density functional theory. The optimal paths to light olefins are determined, in which β-scission reaction is the rate controlling step to produce propylene in 1-hexene cracking paths. Meanwhile, increasing the acid strength will reduce the apparent activation energy of the reaction and facilitate the path to propylene production than the path to ethylene production. The microkinetic modeling shows that the system rate controlling step gradually shifts from a high-energy-barrier reaction to an adsorption reaction of reactants as the reaction temperature increases. In addition, the proportion of monomolecular mechanisms is larger than the bimolecular mechanism under high temperature conditions and the yield of propylene reaches maximum at 750 K, which helps optimize operating temperature for catalytic pyrolysis of 1-hexene. The work can offer new insights into the mechanism of catalytic pyrolysis of olefins and provide a theoretical guide for designing highly active catalysts for such reactions.

Insights into the Reaction Kinetics of Hydrazine-Based Fuels: A Comprehensive Review of Theoretical and Experimental Methods

While researchers have extensively studied the initial decomposition mechanism of Monomethylhydrazine (MMH, CH3NHNH2) in the MMH/dinitrogen tetroxide (NTO) system, the investigation of Unsymmetrical Dimethylhydrazine (UDMH, (CH3)2NNH2) has been limited due to its high toxicity, corrosiveness, and deterioration rate. Hence, the effects of UDMH’s deterioration products on combustion performance and gas-phase combustion reaction mechanisms remain unclear. This comprehensive review examines the existing research on the reaction kinetics of the three widely used hydrazine-based self-ignition propellants: Hydrazine (HZ, N2H4): MMH: and UDMH, emphasizing the necessity for further investigation into the reaction kinetics and mechanisms of UDMH. It also discusses the implications of these findings for developing safer and more efficient rocket propulsion systems. Additionally, this review underscores the importance of utilizing computational chemistry theory to analyze hydrazine-based fuels’ combustion and decomposition properties, constructing detailed pyrolysis and combustion reaction mechanisms to optimize rocket engine fuel performance and environmental concerns.

Average molecular structure model of shale kerogen: Experimental characterization, structural reconstruction, and pyrolysis analysis

Shale can be both a source rock and a reservoir rock, which is a typical self-generating and self-storing type of oil accumulation. Its main organic component is kerogen. Using molecular dynamics (MD), a realistic kerogen molecular structure model is an alternative to experimental and analytical-only approaches for studying shale organic matter's microscopic properties. Therefore, it is useful to establish an average molecular structure model for shale kerogen. Moreover, the pyrolysis mechanism of shale kerogen is of great significance for developing and utilizing shale mineral resources. In this study, geochemical and spectroscopic measurements such as the elemental analysis, 13C nuclear magnetic resonance spectroscopy (13C NMR), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) were used to obtain information about the carbon skeleton, aliphatic structures, and aromatic structures of the kerogen. Following information analysis and molecular fragment splicing, a 2D molecular structure model of kerogen from the Nanpu shale, with the chemical formula C199H240O20N6S2 and molecular weight of 3096 Daltons was constructed. After that, the accuracy of the 2D structure was verified by comparing the 13C NMR spectra simulated by the 2D structure to the experimental spectra. Using MD simulation, based on the kerogen density, 10 2D structures are then combined to create a realistic 3D molecular structure model of kerogen. Finally, pyrolysis analysis was performed based on the established 3D molecular structure model of kerogen to determine the effect of temperature on pyrolysis. Using the advantages of various technologies, this study not only provides a systematic method for establishing a realistic 3D molecular structure model of kerogen but also contributes to in-depth research on the reaction mechanism of kerogen pyrolysis, providing a reliable foundation for future research on the properties of shale at the molecular scale.

Reaction mechanism of stearic acid pyrolysis via reactive molecular dynamics simulation and TG-IR technology

Stearic acid provides a basis for developing renewable energy, such as solar energy and biomass energy. A thermogravimetric-infrared spectroscopy (TG-IR) experimental test is conducted to obtain the thermal decomposition progress and the main gaseous products of stearic acid. The result shows that small gaseous products (H2O, CO2, CO, alkanes, olefins, etc.) are released. Furthermore, the method of reactive molecular dynamics simulation (ReaxFF-MD) is utilized to look into the pyrolysis reaction mechanism of stearic acid. The main pyrolysis products of stearic acid received by ReaxFF-MD are C2H4, H2, C2H2, CH4, H2O, CO2, and CO, consisting of the result of the TG-IR test. The effect of the simulated system density and temperature on the distribution of main products is also explored. Also, the thermal kinetic analysis is conducted by the initial consumption of stearic acid under different temperatures. The primary reaction mechanism of stearic acid pyrolysis is that the stearic acid molecules dissociate through C–C bonds break to generate C2H4, CH4, C2H2, C3H6, and other small molecules and radicals, and a typical reaction mechanism scheme of stearic acid pyrolysis is presented. The results provide a reference for explaining the macroscopic explosion characteristics of dust at the microscopic mechanism level.

Novel insight of the thermal degradation kinetics, environmental impact and transformation behavior of heavy metals and chlorine of municipal solid waste incineration fly ash in nitrogen

Thermal treatment is an effective method to dispose of municipal solid waste incineration (MSWI) fly ash (FA), however, present research mainly focuses on the thermal behavior of FA in air, neglecting the investigation of FA pyrolysis characteristic in inert gases. The weight loss, phase transition, environmental impact, and conversion behavior of heavy metals and chlorine during the FA pyrolysis in N2 were measured using TG-FTIR-XRD-ICP-IC to increase understanding of the transformation process and decomposition features of FA in inert gas. The results demonstrated that CO2, NO, C-O(H), HCl, SO2, and H2O are emitted during FA pyrolysis due to the decomposition of inorganic salts and organic compounds. After being roasted at 1200 °C, the volatilization rates of As, Cr, Cd, Cu, Pb, and Zn were 56.71%, 34.75%, 99.56%, 83.41%, 96.22%, and 97.19%, respectively. However, the removal rate of Cl was only 51.43%, owing mostly to the formation of Ca2SiO4CaCl2 at high temperatures, which hampered chlorine volatilization. The kinetic of FA pyrolysis was investigated using FWO, KAS, and CR methods at heating rates of 10, 20, 30, and 40 °C/min, which suited the experimental data of each stage well. Chemical reaction (No. 2), assumed random nucleation and its subsequent growth (No. 11), and three-dimensional diffusion and spherical symmetry (No. 21) were the reaction control procedures of stages I, III and IV, with activation energies of 54.04, 213.03 and 280.85 kJ/mol, respectively. The degradation kinetics, environmental emissions, and reaction mechanisms of FA pyrolysis in the N2 atmosphere can provide a novel insight for pollution reduction and process optimization.

Constructing bifunctional porous nanosheets for efficient conversion of waste plastics into valuable hydrogen and carbons

Metal oxides as promoting materials can convert waste plastics into hydrogen (H2) fuel by microwave pyrolysis, solving ecological pollution worldwide, but their tendency of agglomeration and poor porosity limit further applications. Herein, we reported a two-dimensional (2D) metal oxide nanosheets with porous network for recycling high-purity hydrogen and carbon nanotubes from waste plastics in microwave-induced reaction. The 2D porous structure significantly improves the growing space of CNTs and enhances the ability of wave absorption, thereby exhibiting a remarkable H2 selectivity of 87.5% and high H2 yield of 60.2 mmol g−1 LDPE, as well as producing high-value CNTs. Moreover, the reaction mechanism for microwave-induced catalytic pyrolysis is proposed, where the Fe2O3 particles on composites facilitated the breakage of C-H bonds, contributing to the generation of H2. The current work provides new insights into the recovery of waste plastics by metal oxides through microwave pyrolysis.

Pyrolysis mechanism of β-d-glucopyranose as a model compound of cellulose: A joint experimental and theoretical investigation

This study aims to reveal the pyrolysis reaction mechanism and product formation pathway of cellulose by combining experimental and theoretical calculation results. First, pyrolysis experiments of glucose, cellobiose, and cellulose were conducted by combined thermogravimetry-Fourier infrared spectroscopy-gas chromatography-mass spectrometry (TG-FTIR-GC-MS). The results show that glucose and cellobiose have two obvious mass loss peaks in their pyrolysis processes and cellulose has only a distinct mass loss peak. In the severe weight loss stage, cellulose forms more H2O, CO2, alkanes, and carbonyl compounds than glucose and cellobiose. Then, β-d-glucopyranose was selected as a model compound of cellulose to carry out density functional theory (DFT) calculations. The formation mechanism of furan derivatives and carbohydrate derivatives was systematically studied. And their competitive relationship was revealed. A reaction network from β-d-glucopyranose to main products was constructed. Based on the concerted reaction mechanism, β-d-glucopyranose is easier to generate furfural, followed by furan, 1,4:3,6-dianhydro-α-d-glucopyranose, and levoglucosenone, and finally 2(5H)-furanone. Based on the H radical attack mechanism, β-d-glucopyranose is easier to form 1-(2-furanyl)-ethanone, followed by 5-methyl-2-furancarboxaldehyde, and finally 2-methyl-furan. Finally, the relationship between the functional groups and the pyrolysis behavior of β-d-glucopyranose was clarified by combining the product distribution detected in experiments and DFT calculations.

Analysis of methane pyrolysis experiments at high pressure using available reactor models

Most batch reactor methane thermal decomposition (MTD) studies have focused on sub-atmospheric pressures. In this study, MTD experiments were performed between 892 K and 1292 K and 4 atm inside a quasi-isothermal quartz batch reactor at residence times ranging from 0 to 300 s. At a given temperature, elevated pressure resulted in higher methane conversion compared with the sub-atmospheric conditions. A zero-dimensional, closed, isochoric, homogeneous gas-phase model was used to compare numerical predictions from available reaction mechanisms in literature to experimental data. It was found that most models accurately predict conversion at low pressure and high temperature and at high pressure and high temperature, but did not accurately predict methane, hydrogen, and intermediate species mole fractions at 4 atm and either 892 K or 1093 K. A reaction path analysis showed the reactions responsible for the delay in hydrogen formation at elevated pressure are 2CH3(+M)⟺ C2H6, C2H6 ＋ CH3⟺ C2H5 ＋ CH4, C2H6 ＋ H ⟺ C2H5 ＋ H2 and C2H5(+M)⟺ C2H4 ＋ H, where M is the collision partner. A gas-phase model accounting for the solid carbon shows that the observed discrepancy is not due to the unavailability of the carbon formation model but to slower reaction kinetics, especially at lower temperatures. The experimental data presented can be used to obtain a methane pyrolysis reaction mechanism suitable for high pressure conditions.