Detailed Kinetic Mechanism Research Articles

Automated adaptive chemistry for Large Eddy Simulations of turbulent reacting flows

Large Eddy Simulations (LES) of turbulent reacting flows carried out with detailed kinetic mechanisms have a key role for the discovery of the physical and chemical processes occurring in combustion systems, and are essential for the development of efficient, stable, and non-pollutant technologies. Nevertheless, these simulations require a large amount of computational resources, making their utilization for large-scale systems, such as industrial burners and gas turbines, impractical. In this work, we combine state-of-the-art machine learning algorithms and model reduction methods to deliver a fully automated strategy for performing LES with adaptive chemistry. This strategy is based on the Sample-Partitioning Adaptive Chemistry (SPARC) algorithmic procedure, which consists of four steps: the generation of a training dataset, its partitioning in clusters, the generation of a set of reduced chemical mechanisms specifically tailored to each cluster and, lastly, the numerical simulation of the case of interest with adaptive chemistry enabled by an on-the-fly classification of every grid point.The SPARC approach has already been demonstrated to substantially reduce the computational effort of reactive flows simulations. However a non-negligible level of user interventions is needed, upon which the method’s success critically depend. Therefore, with the goal of boosting the performance of this workflow and minimise the user-specified degrees of freedom, we plug in and exploit the Local Principal Component Analysis augmented with an automated Bayesian-optimised search for optimal clustering solutions, and the Computational Singular Perturbation method with an additional layer of automation based on the Tangential Stretching Rate for minimally-sized reduced mechanisms. We employ a cheap and easy-to-generate 1-dimensional-flames training database and we demonstrate the efficiency, accuracy and robustness of this strategy with an application to LES of the Adelaide Jet in Hot Coflow (AJHC) burner, a turbulent reacting flow exhibiting intense turbulence-chemistry interactions.

Probing the kinetic sensitization effect of NO2 on ethylene oxidation

Exhaust gas recirculation (EGR) has been widely equipped in modern engines for pollutant emission abatement. NOx present in EGR can greatly influence fuel combustion properties in engine operation. Ethylene (C2H4) is well-known a critical intermediate formed via β-scission reactions of alkyl radicals in the pyrolysis and oxidation of hydrocarbons, thus investigating the mutual effects of C2H4 and NOx is beneficial to engine design as well as hierarchically developed strategy of the chemical kinetic model. This study investigated the auto-ignition behavior of C2H4/air mixtures containing different levels of NO2 (0 ppm, 200 ppm, 500 ppm, 3000 ppm) in a high-pressure shock tube at pressures of 1 atm and 24 atm, temperatures of 820–1300 K and different equivalence ratios of 0.5, 1.0 and 2.0. The results showed that the addition of NO2 significantly promoted auto-ignition at high pressure, while only limited effects at low pressure. A detailed kinetic mechanism was proposed based on a hierarchically developed strategy, and it successfully reproduced the experimental data over the entire test conditions. Flux and sensitivity analyses were implemented to explore the sensitization effect of NO2 addition on the ignition kinetics of C2H4. The analysis revealed that NO2 mainly affects the reaction pathway of ĊH2CHO radical, leading to the formation of HONO. The additional generation of ȮH radicals through HONO = NO + ȮH and NO + HȮ2 = NO2 + ȮH accelerate the auto-ignition of C2H4. At low pressure, the decrease in the rate constant of HONO decomposition weakens the role of NO2.

Detailed kinetic mechanism for nitrocellulose low temperature decomposition

In the current investigation a detailed kinetic scheme of nitrocellulose (NC) is developed. Despite being studied for decades, NC did not have a detailed model yet. Thanks to Reaction Mechanism Generator open-source software a NC decomposition scheme has been generated. Optimizations of that model have been performed including intermediates thermodynamic properties calculations with Gaussian 16 at the B3LYP 6-31G(d,p) level of theory. Model reduction and decomposition computations were achieved with Chemkin-Pro. NC detailed mechanism has been optimized thanks to experimental data available in the literature, by slightly adjusting some rate constants of relevant chemical reactions. For instance, mean deviation of NO molar fraction is about 5.64% showing that the model follows the general trend of measured results. The final NC model consists in 62 species and 803 gas phase reactions. Eventually, NC and hexogen (RDX) models have been merged to predict overpressures obtained experimentally on a RDX-NC propellant. Numerical and experimental results have been confronted regarding the ignition temperature, initial pressure and surrounding gas nature. Computed results have been congruent when compared to experimental data, especially under argon atmosphere with an ignition temperature of 1173 K. Evidences from global trends indicate that the developed model can provide encouraging computations results for future research and investigations.

Modification of Detailed Kinetic Mechanism for Aromatic Hydrocarbon Formation during C3–C4 Hydrocarbon Pyrolysis

Modification of Detailed Kinetic Mechanism for Aromatic Hydrocarbon Formation during C3–C4 Hydrocarbon Pyrolysis

Shock-tube CO measurements during the pyrolysis of ethylene carbonate

Ethylene carbonate (EC) is a key component of the flammable electrolyte in lithium-ion batteries. In this study, the pyrolysis of ethylene carbonate was investigated by measuring CO time histories near atmospheric pressure and in highly diluted conditions (0.999 He/Ar). The performance of a recent detailed chemical kinetics mechanism from Kanayama et al., 2022, was evaluated, and noticeable discrepancies were found, possibly indicating missing reaction pathways. A tentative model was proposed by merging the EC sub-mechanism from the Kanayama study with a recent model for linear carbonate pyrolysis from the authors (Grégoire et al., 2023). This tentative model includes the addition of several missing reactions for oxirane pyrolysis, and a couple of reactions for acetaldehyde and EC thermal decomposition were modified within their error uncertainties. The resulting model presents better predictions overall, but room for improvement remains. This study highlights the need to further study the pyrolysis chemistry of EC as well as acetaldehyde, which is a major intermediate component from EC pyrolysis under our conditions.

A dedicated reduced kinetic model for ammonia/dimethyl-ether turbulent premixed flames

Ammonia (NH3) as a promising energy vector receives growing interest to reduce carbon emissions in combustion applications. Co-firing with dimethyl ether (DME) is an outstanding route to enhance the combustion properties of ammonia. In this study, a reduced model for NH3/DME blend fuels made up of 48 species and 294 reactions was developed starting from a detailed kinetic mechanism. The overall agreement of the reduced model compared with both experimental data and predictions from the original one are good, in terms of ignition delay times, laminar flame speeds, species mole fraction profiles, and S-curves for a variety of NH3/DME mixtures. Additionally, the fidelity of the reduced model has been further evaluated by comparing with other detailed kinetic models from the literature. Using this reduced mechanism, a parametric analysis of one-dimensional flames reveals a trade-off in terms of emissions (NOx vs. CO2), equivalence ratios, and flame propagation characteristics. The ultimate objective of this study is to investigate ignition and turbulent flame dynamics. As a first step in this direction, a turbulent premixed flame of a rich NH3/DME mixture with 25% DME content is investigated by direct numerical simulation (DNS) using the reduced mechanism, and conditional averages are analyzed. This work paves the way for future systematic studies of turbulent NH3/DME flames by DNS.

Detailed kinetic mechanism of polyoxymethylene dimethyl ether 3 (PODE3). Part I: Ab initio thermochemistry and kinetic predictions for key reactions

In recent years, polyoxymethylene dimethyl ether 3 (PODE3) has emerged as a promising fuel additive to mitigate soot emissions in diesel engines, garnering significant research attention. Several detailed kinetic mechanisms of PODE3 have been developed to investigate its reaction pathways and to simulate its combustion process. Typically, these mechanisms employ analogy methods based on rate constants derived primarily from PODE1 sub-mechanisms. However, in this study, we present, for the first time, high-level ab initio quantum chemical calculations directly on PODE3 itself. (1) The bond dissociation energies (BDEs) of all CH and CO bonds in dimethyl ether (DME) and PODEn (n = 1–5) were calculated using combined compound methods (CBS-APNO/G3/G4). (2) The obtained BDE results were then utilized to investigate the unimolecular decomposition reactions of PODE3, demonstrating good agreement with previous Molecular Dynamics simulation results. (3) The rate constants of hydrogen abstraction reactions of PODE3 by H˙,C˙H3,CH3O˙,O˙H,HO˙2,O2 were calculated with all possible pre-reaction or post-reaction complexes identified. The rate constants of the H-atom abstraction reactions were found to primarily depend on the energy barriers following the order: O˙H>CH3O˙>H˙>C˙H3>HO˙2>O2. However, the abstraction by H˙ can dominate as temperature increases. (4) The rate constants of β-scission and isomerization reactions of PODE3 radicals were also computed. The calculated β-scission reaction rates supported the suitability of the rate analogy for PODEn, employing the long-chain PODE3. The energy barriers of the isomerization reactions with long chain transition states were comparable to the energy barrier of the β-scission reactions and are much lower than that in the case of PODE1 radicals. (5) The thermochemistry properties of all involved species, including PODE4–5 and their radicals, were calculated with the combined compound methods (CBS-APNO/G3/G4) for further combustion modeling. Considering PODE3′s nature as a long-chain PODEn, the rate constants computed for PODE3 can serve as a solid foundation for developing detailed mechanisms for PODE4–5.

Experimental and kinetic study on aromatic formation in counterflow diffusion flames of methane and methane/ethylene mixtures

Aromatics are molecular soot precursors, yet detailed kinetic mechanisms describing their formation in flame environments are insufficient even for the simplest hydrocarbon fuel of methane. Considering the building roles of methane-related chemistry in current hierarchically-structured mechanisms, the present study is devoted to the chemistry of aromatic formation in CH4 flames. We established a series of incipiently sooting methane counterflow diffusion flames (CDF) and characterized their thermochemical structures including the scalar fields of temperature, concentrations of major species, C2–C4 minor intermediates, benzene, large aromatic species, and soot volume fraction. The measurement techniques include tunable diode laser absorption spectroscopy (TDLAS), gas chromatography–mass spectrometer (GC–MS) and laser induced incandescence (LII). The experimental dataset was then used to assess various recently proposed kinetic mechanisms. The results showed that the literature mechanisms tested would significantly overpredict benzene formation in CH4 CDFs (up to a factor of 10). In addition, none of the tested mechanisms could capture the experimentally observed suppressing effects of CH4 addition on the formation of aromatic species in C2H4 CDFs. Potential reactions responsible for the model failures are discussed. The main contributions of this study are to: 1) identify the limitations of existing aromatic mechanisms when applied to methane CDFs; 2) clarify potential reactions/pathways related to model deficiencies; 3) provide novel experimental dataset covering both gas-phase speciation and soot for methane CDFs. It is our hope that the present data and analysis would deepen our understanding on benzene formation chemistry, and contribute to the refinement of aromatic formation predictive models.

Community analysis of bifurcation maps of diluted hydrogen combustion in well stirred reactors

This article focuses on applying an automatic procedure for inspecting detailed kinetic mechanisms to predict key species/reactions playing a dominant role in the dynamic behaviour of regime transitions of combustion systems. We adopted a novel analysis method of kinetic mechanisms built by coupling the bifurcation analysis, which identifies the different regimes occurring with a change of the parameters, with algorithms typical of Artificial Intelligence, specifically the Community Analysis, which identifies within a large set of individuals (the chemical species) common behaviour patterns. Then we showed that this method is capable of automatically extracting meaningful information to identify the key species responsible for the dynamic behaviour and change of regimes observed in the solution maps of a combustion system. Application to a diluted hydrogen combustion system is illustrated as a first validation bench. It reveals that the recognition of state change is effective when based on proper indexes. On the full range of the parameter investigated, the inlet mixture temperature, when adopting an index correlated to the heat release rate, different community partitions were identified for each of the three regions with different dynamic behaviour. The most complex community partitions, with three communities, arise in the first two regions of lower temperature. The partition simplifies in the region of the higher parameter values where the system shows steady solutions without oscillations. The change in the link of atomic hydrogen, OH, and H2O2 with the remaining species is identified in the regime transitions.

Upcycling of the Used Cigarette Butt Filters through Pyrolysis Process: Detailed Kinetic Mechanism with Bio-Char Characterization.

Thermo-chemical conversion via the pyrolysis of cigarette butt (CB) filters was successfully valorized and upcycled in the pre-carbonization and carbonization stages. The pre-carbonization stage (devolatilization) of the precursor material (cellulose acetate filter, r-CAcF) was analyzed by micro-scale experiments under non-isothermal conditions using TG-DTG-DTA and DSC techniques. The results of a detailed kinetic study showed that the decomposition of r-CAcF takes place via complex mechanisms, including consecutive reaction steps and two single-step reactions. Consecutive stages include the α-transition referred to as a cellulose polymorphic transformation (cellulose I → II) through crystallization mechanism changes, where a more thermodynamically ordered system was obtained. It was found that the transformation rate of cellulose I → II ('cellulose regeneration') is strongly affected by the presence of alkali metals and the deacetylation process. Two single-step reactions showed significant overlapping behavior, which involves a nucleation-controlled scission mechanism (producing levoglucosan, gaseous products, and abundant radicals) and hydrolytic decomposition of cellulose by catalytic cleavage of glycosidic bonds with the presence of an acidic catalyst. A macro-scale experiment showed that the operating temperature and heating rate had the most notable effects on the total surface area of the manufactured carbon. A substantial degree of mesoporosity with a median pore radius of 3.1695 nm was identified. The presence of macroporosity on the carbon surface and acidic surface functional groups was observed.

NH3 oxidation and NO reduction by NH3 in N2/Ar and CO2 atmospheres

Impact of using CO2 or N2/Ar as bath gas, representative respectively of oxy-fuel or air combustion scenarios, has been evaluated on the oxidation of ammonia under a variety of operating conditions in a combined experimental and simulation study. Variables of relevance as temperature and oxygen stoichiometry have been considered at atmospheric pressure and under carefully controlled experimental conditions. Additionally, the impact of the presence of NO, which can be formed from ammonia oxidation, has also been evaluated. The experimental results obtained have been simulated with significant success with a detailed literature kinetic mechanism, which has been further used to interpret the main experimental observations. The results obtained are of interest in the power and energy industry, and can be used for guiding the co-firing of NH3 and carbon containing fuels.

Numerical simulation of nano-aluminum ignition in oxygen and steam environments

The ignition characteristics of nano-aluminum (nano-Al) in oxygen and steam environments were numerically studied in this work. A detailed kinetic mechanism of nano-Al combustion was developed, and the effects of initial reaction temperature, ignition pressure, the phase of reactant, and the ratio of O2 and H2O in the oxidizer on the oxidation performance of aluminum (Al) were analyzed in detail. Numerical results show that increasing the initial temperature promotes the ignition of liquid-phase Al, while the promotion is not significant for gas-phase Al ignition. The oxidation of liquid-phase Al is significantly slower than that of gas-phase Al, and the phase transition reaction of liquid-phase Al exhibits a typical endothermic process, which results in a temperature drop before ignition. The increase of initial reaction pressure can accelerate the consumption of both liquid-phase Al and gas-phase Al in the ignition process. The oxidizability of O2 is much larger than that of H2O, and the oxidation of Al becomes slower by adding H2O in the oxidizer. The rate of production (ROP) was performed to deeply realize the reaction pathways of Al consumption and main products formation. The reaction Al + O2 = AlO + O is the key reaction pathway in the Al-O2 ignition process, while the reaction Al + H2O = AlOH + O plays a more important role in the Al-H2O ignition process. In the all ignition cases, Al2O2 is a key intermediate species since it is the main precursor of gaseous Al2O3, and liquid-phase Al2O3 formed by the phase transition reaction of gaseous Al2O3 is the dominant final product.

Local sensitivity informed anisotropic sparse grid method for uncertainty quantification of chemical kinetics

The determination of rate coefficient parameters in detailed chemical kinetic mechanisms through experiments often suffers from avoidable aleatory uncertainty, while the use of reduced mechanisms, based on various reduction methods, introduces epistemic uncertainty. Both sources of uncertainty pose significant challenges for modeling and numerical simulation, highlighting the need for calibrating these uncertain parameters to achieve robust chemical mechanisms in the next generation. However, the high-dimensional parameter space of chemical kinetic mechanisms remains a significant obstacle in uncertainty computing. The Anisotropic Sparse Grid (ASG) technique has been successful in dealing with high-dimensional uncertainty problems, but it lacks prior knowledge of anisotropy. To address this issue, we propose the Local Sensitivity-Informed Anisotropic Sparse Grid (LSIASG) method, which utilizes local sensitivity as prior information for the ASG method, thereby accelerating the entire uncertainty quantification process. We test the LSIASG method on a theoretical model, a detailed hydrogen kinetic mechanism, and a methane mechanism and demonstrate that it can capture high-dimensional uncertainty characteristics, including expectation and deviation.

Mechanism study on the auto-ignition and reaction kinetic characteristics of hydrogen/n-dodecane mixture under mid and high temperature conditions

To acquire the ignition promotion methods for scramjet engine, the auto-ignition and reaction kinetic characteristics of hydrogen/n-dodecane mixture under mid and high temperatures were revealed by detailed chemical kinetic mechanism and experimental data. The results illuminated that the increases of n-dodecane's content and ϕ significantly declined the ignition delay time (IDT) of hydrogen mixture (by two orders of magnitude at most) at mid-temperature high-pressure (T = 950 K&p = 40 bar). The addition of n-dodecane induced the OH radical formation in initial stage and the advance of fuel's H-abstraction reactions (hydrogen: R3, n-dodecane: R2741/R2742/R2743/R2746). Whereas, the corresponding reduction in hydrogen content inhibited the establishment of active radical pool in dual-fuel reaction system before ignition time point. The ignition promoting effect of advanced initial reaction stage overweighted the ignition inhibiting effect of weakened rapid reaction stage in mid-temperature low-reactivity dual-fuel reaction system. Interestingly, at high-temperature high-pressure (T = 1300 K&p = 40 bar), the IDT firstly decreased (by 18.8%), and then continuously increased (by 105.3% at most) with the elevating n-dodecane's content. The minor addition of n-dodecane (1% of mole fraction) at high-temperature had a similar ignition promoting effect as that at mid-temperature. Whereas, the further reduction in hydrogen content dramatically suppressed the formation of active radical pool (H/OH/HO2/H2O2), which overweighted the ignition promoting effect of slightly advanced initial reaction stage. In other words, the hydrogen played a more critical role than the n-dodecane in high-temperature reaction system due to the originally high reactivity of hydrogen. The auto-ignition properties of hydrogen/n-dodecane mixture relied on the competition relationship of initial and rapid reaction stages under specific thermodynamic conditions and blending ratios. This investigation not only reveals internal interaction mechanism between fuels and active radicals in hydrogen/n-dodecane reaction system, but also provides fundamental insights for the precisely ignition promition methods of hydrogen/aviation-kerosene dual-fuel scramjet engine.

Measurements of the laminar burning velocities of small alkyl esters using the heat flux method: A comparative study

Consistent datasets of the laminar burning velocity, LBV, for homologous fuels are indispensable for the elucidation of the structure-reactivity trends and the development and validation of pertinent detailed kinetic models. In the present study, all available LBV measurements for small alkyl esters obtained using the heat flux method have been reviewed. New results of the LBV for methyl propionate + air flames employing this method have been acquired at atmospheric pressure and initial gas temperatures from 298 to 348 K over equivalence ratios, ɸ = 0.7–1.5. Earlier experimental data for alkyl esters scattered across non-archival reports were re-examined and corrected when necessary. To prove the validity of the correction, additional LBV measurements for methyl formate and methyl butanoate were performed as well, and successfully demonstrated the consistency of the data obtained using different installations over an extended period of time. Then, the LBV of different families, such as methyl esters of various acids, formates, and acetates, along with isomers, were compared and structure-reactivity trends were assessed. Furthermore, the detailed kinetic mechanism of the authors was expanded by the reactions of methyl propionate and successfully compared with the LBV measurements for methyl formate, methyl acetate, methyl propionate, and ethyl formate. Distinct reactions controlling their flame propagation were revealed using sensitivity analysis and the origin of their rate constants is briefly discussed.

A numerical investigation of effects of chemical kinetic mechanisms on the structure of turbulent jet diffusion H2/air flame with Lagrangian PDF method

Many physical phenomena characteristic of reactive flows are controlled by the detail of the chemical kinetics of combustion. These include, for example, the ignition and extinction of a flame and the formation of polluting species. These phenomena require the use of detailed kinetic schemes including hundreds of species and thousands of reactions.The main objective of this work is to highlight the influence of chemical kinetics on the structure of turbulent jet diffusion H2/air flame. Five improved hydrogen kinetic mechanisms have been tested in order to validate, compare and evaluate their effect on the scalar and dynamic fields of such flames. The effect of number particles used in Lagrangian PDF method on the temperature evoltution is also studied. A hybrid method, PDF Lagrangian coupled to the RSM turbulence model, is used in this work, for the numerical simulation. The micro-mixing term of the TPDF is modeled by the EMST model. This model, which describes well the physical process of mixing, has shown its capabilities to give good numerical results. The impact of these mechanisms on the numerical results of scalar and dynamic fields was discussed and compared with the experimental data. The scalar field is well influenced by the choice of the chemical kinetic mechanism. This is not the case of the dynamic field. A good agreement with experience is observed for detailed kinetic mechanisms. However, it has been noticed that simple and reduced mechanisms give also satisfactory results, particularly the reduced kinetic mechanism R12 wich includes 12 reaction and can be considered as a compromise among the five kinetic mechanisms. These mechanisms allows for a significant reduction in CPU time and storage memory. It was also observed that, for the two chemical kinetic mechanisms R12 and R27, the number of particles only affects the radial evolution.

Comprehensive study of autoignition characteristics of propane

Ignition delay times (IDT) for stoichiometric propane (C3H8) diluted with nitrogen were measured in a shock tube facility under reflected shock wave conditions at pressures ranging from 1 to 10 atm and temperatures between 850 and 1500 K. The experiments were limited to a maximum pressure of 10 atm due to the facility’s constraints. In addition, numerical simulations were conducted using several detailed kinetic mechanisms at pressures from 1 to 30 atm and three equivalence ratios (φ = 0.5, 1, and 2) to provide comparative insights. The results indicated that IDT decreases as pressure increases, with a more significant reduction observed between 1 and 10 atm compared to 10 to 30 atm. While most models exhibited similar trends and minimal discrepancies, the GRI Mech 3.0 mechanism demonstrated a slower prediction of ignition delay times at temperatures below 1250 K. In contrast, the POLIMI model exhibited a relatively faster prediction at temperatures above 1250 K, with the deviation between the two models becoming more pronounced as pressure increased. A comparative analysis revealed that the experimental predictions of propane autoignition behavior were in good agreement with the results obtained using the ARAMCO 3.0 mechanism. To further understand the chemistry governing the autoignition process of C3H8, a sensitivity analysis was performed for a stoichiometric mixture at three distinct temperatures (850 K, 1200 K, and 1550 K).

An experimental and kinetic modeling study on low-temperature oxidation of gasoline and diesel/polyoxymethylene dimethyl ether (OME3) blends

In this work, the low-temperature oxidation of polyoxymethylene dimethyl ether (OME3) with multi-component surrogates for diesel (DS:60%n-heptane/20%cyclohexane/20%toluene) and gasoline (GS:20%n-heptane/60%iso-octane/20%toluene) blends was investigated respectively using a jet-stirred reactor (JSR) with a temperature range of 500–950 K, constant fuel fraction of 0.008, residence time (τ) of 2 s and near atmospheric pressure. Two detailed multi-component kinetic mechanisms were established to describe the low-temperature oxidation characteristics and the interaction of blended fuels. Generally, the oxidation process of highly-reactive OME3 and n-heptane is inhibited, while that of inactive fuels, including iso-octane, cyclohexane and toluene, are triggered and enhanced in various degrees in the blends. The OH radical acts as a bridge between high and low reactivity components. It is of interest that n-heptane reveals a quite different low-temperature oxidation behavior in diesel (DS) and gasoline (GS) surrogate respectively. In GS, the low-temperature oxidation of n-heptane is significantly inhibited, while in DS, the inhibition is mild, mainly due to the much different low-temperature oxidation characteristics of iso-octane and cyclohexane. As for OME3, it mainly improves the reactivity of the blends in the negative temperature coefficient (NTC) process. As for low-reactivity fuels of iso-octane and toluene, their low-temperature oxidations are completely triggered and dominated by highly-reactive fuels due to their weak OH build-up ability. On the contrary, when the low-temperature oxidation of cyclohexane is triggered, its self-enhancement also plays a crucial role in addition to the promoting effect from highly-reactive fuels. Therefore, cyclohexane reveals a promoting-ignition effect on the blended fuels, while iso-octane and toluene act as an inhibiting-ignition factor in blends.

A Comprehensive Monte Carlo Model of the Grafting of Maleic Anhydride onto Polypropylene with Experimental Validation

AbstractA Monte Carlo model is employed to investigate the grafting of maleic anhydride onto polypropylene using a peroxide initiator. The study aimed to develop a comprehensive model that considered a very detailed kinetic mechanism, including chain transfer to polymer, homopolymerization as well as several copolymer reactions. The relative importance of these reactions is evaluated using a sensitivity analysis, which identified homopolymerization, β‐scission, chain grafting, and termination by disproportionation as the most influential reactions. The kinetic constants of these reactions are tuned to fit reported experimental data using the Surface Response Method. The model considers a pseudo‐homogeneous reaction medium and predicts average molecular weights, degree of grafting, molecular weight distribution, and grafting distribution. Furthermore, model simulations provided useful information about the impact of initial concentrations of reactants and reaction time on the molecular properties of the grafted polymer.

Exploring pyrolysis of the aromatics in shale oil by experimental study and kinetic modelling

In this work, the main aromatics in shale oil from retorting Huadian oil shale and the functional groups during the pyrolysis of shale oil were studied experimentally. The aromatics in shale oil are mainly monocyclic aromatic hydrocarbons (MAHs). Alkylbenzenes are the most abundant in MAHs of shale oil. Then, nonylbenzene was selected as representative to explore the pyrolysis mechanism through theoretical calculation and kinetic modelling due to the activity of its alkyl side-chain and the abundance in alkylbenzenes of shale oil. The bond dissociation energies (BDE) of the C–C and C–H bonds were calculated using the CBS-QB3 quantum chemistry method to study its thermostability. Finally, the detailed pyrolysis kinetic mechanism of nonylbenzene was written by the GRI-Mech3.0 mechanism. A large number of the kinetic parameters were computed by the group-additivity method. In addition, the kinetic parameters of these two non-negligible retroene reactions of nonylbenzene were calculated by the CBS-QB3 method to develop the kinetic model. In summary, the pyrolysis mechanism can improve the understanding of shale oil reactivity due to that it could be chosen as a model compound for novel surrogate shale oil model and has a significant guidance on the development of the kinetic model of alkylbenzenes.