Chemical Kinetic Model Research Articles

Steam reforming of methane in a gliding arc discharge reactor to produce hydrogen and its chemical kinetics study

A knife-type gliding arc discharge plasma reactor was developed for steam-methane reforming (SMR) H2 production. The kinetic model was established for industrial application. The effects of steam to carbon molar ratio, residence time and input power on SMR reactions were investigated. The experimental results indicated the S/C molar ratio of 2.01, the residence time of 13.8 s, and the input power of 36.0 W, the energy yield of hydrogen reached 173.6 L·(kW·h)−1, H2 and CO were also identified as the main gaseous products. Optical emission spectroscopy was used to diagnose chemically active species in plasma processes. The corresponding zero-dimensional chemical kinetic model was established, which includes 166 electron impact reactions and heavy particle reactions. The calculated results were in good agreement with the experimental results. The model results revealed the reaction CH4 + H → CH3 + H2 initiated by the H atom was the dominant reaction of CH4 conversion, and was also the main way of H2 generation.

A Hierarchical Theoretical Study of the Hydrogen Abstraction Reactions of H2/C1-C4 Molecules by the Methyl Peroxy Radical and Implications for Kinetic Modeling.

The hydrogen atom abstraction by the methyl peroxy radical (CH3O2) is an important reaction class in detailed chemical kinetic modeling of the autoignition properties of hydrocarbon fuels. Systematic theoretical studies are performed on this reaction class for H2/C1–C4 fuels, which is critical in the development of a base model for large fuels. The molecules include hydrogen, alkanes, alkenes, and alkynes with a carbon number from 1 to 4. The B2PLYP-D3/cc-pVTZ level of theory is employed to optimize the geometries of all of the reactants, transition states, and products and also the treatments of hindered rotation for lower frequency modes. Accurate benchmark calculations for abstraction reactions of hydrogen, methane, and ethylene with CH3O2 are performed by using the coupled cluster method with explicit inclusion of single and double electron excitations and perturbative inclusion of triple electron excitations (CCSD(T)), the domain-based local pair-natural orbital coupled cluster method (DLPNO-CCSD(T)), and the explicitly correlated CCSD(T)-F12 method with large basis sets. Reaction rate constants are computed via conventional transition state theory with quantum tunneling corrections. The computed rate constants are compared with literature values and those employed in detailed chemical kinetic mechanisms. The calculated rate constants are implemented into the recently developed NUIGMECH1.1 base model for kinetic modeling of ignition properties.

Nonequilibrium Dissociation and Recombination Models for Hypersonic Flows

A recombination reaction model for high-temperature chemical kinetics is analytically derived from ab initio simulation data. When atoms recombine, the kinetic rate model shows that product molecules favor high vibrational energy states. In this manner, recombination repopulates high vibrational energy states depleted by dissociation, in a high-temperature reacting gas. Coupling of internal energy relaxation, dissociation, and recombination results in depleted or overpopulated (relative to a corresponding Boltzmann distribution) vibrational energy distributions. Through a simple model, we show that non-Boltzmann behavior, in other words, depletion or overpopulation of high-energy states, is not only linked to thermal nonequilibrium but also chemical nonequilibrium. The mathematical derivation also indicates that the conventional approach for modeling recombination rates, where shock-tube dissociation rate measurements are combined with the principle of detailed balance, is incorrect. The complete analytical dissociation/recombination model embeds all relevant kinetic processes, including specific terms for translation/rotation/vibration/chemistry coupling, anharmonic and quasi-bound effects, and non-Boltzmann depletion and overpopulation effects. The model is a multitemperature model that can be used within computational fluid dynamics simulations with no appreciable increase in computational expense. Finally, because the model is analytical, containing separate terms for various physical effects, further model simplification could be performed depending on the flow conditions of interest.

Numerical Study on Flow and Heat Transfer of Supercritical Hydrocarbon Fuel in Curved Cooling Channel

The fluid flow and heat transfer of hydrocarbon fuel play a significant role in developing regenerative cooling technology for advanced aeroengines. Numerical simulations have been conducted to investigate the flow and heat transfer characteristics of China RP-3 aviation kerosene with pyrolysis in a 3D, 90° bend, square cooling channel around the cavity flame-holder of a scramjet. A chemical kinetic model, composed of 18 species and 24 reactions, was adopted to simulate the fuel pyrolysis process. Results indicate that the secondary flow enhances the mixing of the fluid, thus, the transports of heat and components are improved between the near-wall region and main flow field in the curved channel. Compared with a straight cooling channel, fuel conversion and heat-absorbing capacity are higher, and the heat transfer is effectively enhanced in a curved cooling channel. In addition, with the increasing inlet mass flow rate and the decreasing radius of curvature, the velocity of the secondary flow increases. The heat and components are easily transferred from the near-wall region to the main flow. The non-uniformities of fuel temperature and conversion at the cross section decreases, which is helpful for improving the utilization of the level of fuel heat-absorbing capacity, and beneficial for enhancing the heat transfer.

Low- and intermediate-temperature oxidation of dimethyl ether up to 100 atm in a supercritical pressure jet-stirred reactor

Understanding the low- and intermediate-temperature oxidation chemistry of oxygenated fuels like dimethyl ether (DME) at high pressure is paramount to the development of advanced engines with low carbon emissions. The supercritical pressure jet-stirred reactor (SP-JSR) recently developed at Princeton provides a new platform for conducting kinetic studies at low and intermediate temperatures at extremely high pressures with a uniform temperature distribution and a short flow residence time. This paper uses the SP-JSR to investigate DME oxidation at equivalence ratios of 0.175, 1.0, and 1.72, for pressures of 10 and 100 atm, and temperatures ranging from 400 to 900 K. The results demonstrate weakened NTC behavior at 100 atm relative to 10 atm due to increased flux through QOOH + O2 = O2QOOH relative to QOOH = 2 CH2O + OH at 100 atm. Furthermore, the intermediate-temperature oxidation window is shifted to lower temperatures at 100 atm. The experimental data are compared with several chemical kinetic models from the literature. The existing models are seen to agree quite well with the experimental data at 10 atm. However, the models fail to properly capture the NTC behavior at 100 atm. Reaction pathway analyses indicate that both the low- and intermediate-temperature chemistries are controlled by RO2 consumption pathways. The reaction rates for several of the important reactions, such as DME + OH = CH3OCH2 + H2O, H2O2 (+M) = 2 OH (+M), and 2 HO2 = 2 OH + O2 are updated in this work. The updated model improves the predictability for all key species compared to the original model.

Theoretical study of active secondary transport: Unexpected differences in molecular mechanisms for antiporters and symporters.

Successful functioning of biological cells relies on efficient translocation of different materials across cellular membranes. An important part of this transportation system is membrane channels that are known as antiporters and symporters. They exploit the energy stored as a trans-membrane gradient of one type of molecules to transport the other types of molecules against their gradients. For symporters, the directions of both fluxes for driving and driven species coincide, while for antiporters, the fluxes move in opposite directions. There are surprising experimental observations that despite differing only by the direction of transport fluxes, the molecular mechanisms of translocation adopted by antiporters and symporters seem to be drastically different. We present chemical-kinetic models to quantitatively investigate this phenomenon. Our theoretical approach allows us to explain why antiporters mostly utilize a single-site transportation when only one molecule of any type might be associated with the channel. At the same time, the transport in symporters requires two molecules of different types to be simultaneously associated with the channel. In addition, we investigate the kinetic constraints and efficiency of symporters and compare them with the same properties of antiporters. Our theoretical analysis clarifies some important physical-chemical features of cellular trans-membrane transport.

Elucidation of alveolar macrophage cell response to coal dusts: Role of ferroptosis in pathogenesis of coal workers' pneumoconiosis

Causal factors underlying coal workers' pneumoconiosis (CWP) have been variously attributed to the presence of carbon, crystalline silica and reduced iron (Fe) minerals, especially pyrite and Fe/Si-amorphous compounds. The aim of this research was to assess the role of iron in CWP and, more specifically, the cytotoxicity of coal dusts with different elemental composition towards alveolar macrophages (AMs). Survival rate of AMs, alteration in the production of pro-inflammatory cytokine TNF-α, MDA (the lipid peroxidation product) and intracellular GSH were assessed using commercial assay kits. The quantitative interaction between iron and GSH was investigated by developing a numerical model. The presence of various reduced Fe minerals (viz. pyrite and siderite) in coal dusts exhibited a consistently acute adverse impact on the viability of AMs and enhanced the production of TNF-α. The presence of the clinically available Fe chelator deferiprone (DFP) and the cytosolic antioxidant glutathione (GSH) significantly increased the viability of AMs exposed to Fe bearing coal dusts, suggesting coal dusts containing reduced Fe minerals were likely contributors to the initial stages of AM cytotoxicity via a ferroptosis related pathway. Chemical kinetic modeling indicated that these results may be attributed to an enhanced consumption of GSH as a result of Fe redox cycling. FeIIGSH and GS• produced from the interaction between ferric Fe and GSH facilitated the production of O2•− which further oxidized GSH via a direct reaction between GSH and GS• or GSO•. These results suggest that coal dusts containing reduced Fe minerals and Fe compounds may elevate acute inflammation levels in AMs, indicating that crystalline silica may not be the only hazard of concern in mining environments.

Construction of a Chemical Kinetic Model of Five-Component Gasoline Surrogates under Lean Conditions.

The requirements for improving the efficiency of internal combustion engines and reducing emissions have promoted the development of new combustion technologies under extreme operating conditions (e.g., lean combustion), and the ignition and combustion characteristics of fuels are increasingly becoming important. A chemical kinetic reduced mechanism consisting of 115 species and 414 elementary reactions is developed for the prediction of ignition and combustion behaviors of gasoline surrogate fuels composed of five components, namely, isooctane, n-heptane, toluene, diisobutylene, and cyclohexane (CHX). The CHX sub-mechanism is obtained by simplifying the JetSurF2.0 mechanism using direct relationship graph error propagating, rate of production analysis, and temperature sensitivity analysis and CHX is mainly consumed through ring-opening reactions, continuous dehydrogenation, and oxygenation reactions. In addition, kinetic parameter corrections were made for key reactions R14 and R391 based on the accuracy of the ignition delay time and laminar flame velocity predictions. Under a wide range of conditions, the mechanism’s ignition delay time, laminar flame speed, and the experimental and calculated results of multi-component gasoline surrogate fuel and real gasoline are compared. The proposed mechanism can accurately reproduce the combustion and oxidation of each component of the gasoline-surrogate fuel mixture and real gasoline.

Variable pressure JSR study of low temperature oxidation chemistry of n-heptane by synchrotron photoionization mass spectrometry

Low temperature oxidation chemistry is crucial in the auto-ignition process of internal combustion engines. The development of laboratory based reactors and diagnostic systems promotes understanding of the low temperature oxidation mechanism. This work develops a variable pressure jet-stirred reactor (VP-JSR) platform working from one to ten bar. Compared to previous high pressure studies which routinely use gas chromatography to analyze low temperature oxidation products, the difference in this work is the possibility of probing intermediates by synchrotron vacuum ultraviolet photoionization mass spectrometry via molecular beam sampling. The setup was validated by repeating n-heptane low temperature oxidation experiments at one and ten bar, respectively. Good agreement was observed between the data in this work and the data in the literature. A much more detailed species pool was probed compared to the literature study, including H2O2, carbonyl acids, alkylhydroperoxides, and keto-hydroperoxides. As a first demonstration of the usefulness of this design, the low temperature oxidation of n-heptane with initial fuel mole fraction of 0.005, residence time of 2 s, and equivalence ratio of 1.0 was studied at one, five, and ten bar. The preliminary results, including reactants, final products, and the initial low temperature oxidation intermediates, are discussed. The VP-JSR system developed in this work is valuable for study of the fuel chemistry from one to ten bar, to develop and examine chemical kinetic models, and to guide the development of the reaction system at even higher pressures, such as those in engine function and supercritical conditions.

Energy and environmental risk assessments of poultry manure sustainable solution: An industrial case study in Singapore

Despite the potential of poultry manure as a sustainable waste stream, poultry manure is unsatisfactorily utilized due to the lack of public confidence in both food safety and environmental concerns. In this paper, the energy, environmental and microbial risk assessments of an industrial-scale chicken manure gasification plant in Singapore are demonstrated to overcome the barriers of poultry manure utilization and standardize the management practice. The gasification products and performances are analyzed and optimized based on a numerical chemical reaction kinetics model. The life-cycle assessment results show that the gasification-based treatment has less greenhouse gas emissions than direct land application and anaerobic digestion approaches. Finally, the quantitative microbial risk assessment shows that all the potential pathogenic hazards in chicken manure can be removed through the gasification process, which proves the safety of chicken manure biochar for further agricultural applications and shows the potential infection risk of direct land application.

Computational studies on the reactions of thiols, sulfides and disulfides with hydroperoxides. Relevance for jet fuel autoxidation

Density Functional Theory calculations (DFT) are reported on the reactions of hydroperoxides with different classes of sulfur: thiols (RSH), sulfides (RSR) and disulfides (RSSR), all of which are important trace species in the auto-oxidation of jet fuel. It is shown that thiols can react under auto-oxidation conditions with hydroperoxides to form sulfonic acids and alcohols. In contrast, it is shown that disulfide species are more likely to form thiyl radicals, which are less likely to be important for the direct autoxidation of fuels due to prohibitive reaction barriers. The reaction mechanisms reported here for sulfur oxidation and the associated calculated thermodynamic data can be used to extend the applicability of current chemical kinetic models for fuel autoxidation, which are currently treated as a single elementary reaction despite the range of sulfur species found in fuels.

An Investigation of the Kinetic Modeling and Ignition Delay Time of Methanol—Syngas Fuel

The recycling of exhaust heat in internal combustion engines to dissociate the methanol, followed by its blending with methanol to produce engine fuel, is promising for improving the efficiency of engines, and reducing emissions. The kinetic model MEOHSYNGAS1.0 for the methanol–syngas fuel is proposed by reducing the detailed chemical kinetic model (Mech15.34). Shock tube experiments are conducted to measure the ignition delay time of methanol blended with dissociated methanol gas at different dissociated methanol ratios (0, 30, 50, and 100%). The model is validated by the experimental data of the present work and with data from the literature. The effects of the equivalence ratio, pressure, and dissociated methanol ratio on the ignition delay time are investigated through reaction path analysis and sensitivity analysis. When the dissociated methanol ratio does not surpass 50%, the ignition delay time increases with the increase in the dissociated methanol ratio, which is more obvious in the low temperature range, and but decreases with the increase in temperature.

Autonomous kinetic modeling of biomass pyrolysis using chemical reaction neural networks

Modeling the burning processes of biomass such as wood, grass, and crops is crucial for the modeling and prediction of wildland and urban fire behavior. Despite its importance, the burning of solid fuels remains poorly understood, which can be partly attributed to the unknown chemical kinetics of most solid fuels. Most available kinetic models were built upon expert knowledge, which requires chemical insights and years of experience. This work presents a framework for autonomously discovering biomass pyrolysis kinetic models from thermogravimetric analyzer (TGA) experimental data using the recently developed chemical reaction neural networks (CRNN). The approach incorporated the CRNN model into the framework of neural ordinary differential equations to predict the residual mass in TGA data. In addition to the flexibility of neural-network-based models, the learned CRNN model is interpretable, by incorporating the fundamental physics laws, such as the law of mass action and Arrhenius law, into the neural network structure. The learned CRNN model can then be translated into the classical forms of biomass chemical kinetic models, which facilitates the extraction of chemical insights and the integration of the kinetic model into large-scale fire simulations. We demonstrated the effectiveness of the framework in predicting the pyrolysis and oxidation of cellulose. This successful demonstration opens the possibility of rapid and autonomous chemical kinetic modeling of solid fuels, such as wildfire fuels and industrial polymers.

Pyrolysis and oxidation of a light naphtha fuel and its surrogate blend

An experimental and kinetic study on pyrolysis and oxidation of a real light naphtha fuel and its surrogate blend were conducted. Based on the chemical functional group method, a three-component surrogate blend for the target naphtha was formulated, which contains 64.2 mol% iso-pentane, 21.0 mol% n-hexane, and 14.8 mol% methylcyclopentane. The pyrolysis and oxidation characteristics of the target naphtha fuel and the formulated surrogate were compared using a jet-stirred reactor (JSR) at the equivalence ratios of 0.5, 1.0, 2.0 and ∞, across the temperature range from 700 to 1100 K, and at atmospheric pressure. Mole fractions of the three components, oxygen, hydrogen, CO, CO2, and C1-C4 hydrocarbons were measured by gas chromatograph. Similar global reactivities between the two test fuels were observed in both pyrolysis and oxidation experiments. In addition, a detailed chemical kinetic model was constructed and validated against the species mole fraction profiles measured in JSR experiments. The present model can provide reasonable prediction of the experimental measurements of the species mole fractions in pyrolysis and oxidation of the surrogate blend. Uncertainty-weighted sensitivity analysis indicates that the model prediction of the consumption of the three components of the surrogate blend in pyrolysis are dominated by the rate constants for H-abstraction reactions of isopentane, n-hexane, methylcyclopentane and propene by H atom and methyl radical. The model predictions of the oxidation reactivity of the surrogate blend mainly depend on H-abstraction reactions from the three surrogate components by HO2 radical at 800 K, while the H-abstraction reactions from aldehyde and alkene intermediates become more significant at 950 K.

Challenges in Kinetic modeling of ammonia pyrolysis

Ammonia pyrolysis reactions have implications for its ignition and oxidation in engines and gas turbines. In the present work, the chemistry of ammonia pyrolysis is investigated by kinetic modeling and theory. Rate constants for key reactions are carefully evaluated based on available experimental and theoretical results. The high pressure limit k1,∞ for NH2 + H (+M) ⇄ NH3 (+M) (R1) is calculated to be essentially the collision frequency, indicating that dissociation of ammonia in combustion processes will be at or close to the low pressure limit even at engine and gas turbine conditions. The chemical kinetic model is validated against reported shock tube measurements of NH3, NH2, and NH in ammonia pyrolysis. Predictions are in good agreement with observations for dilute conditions (≤ 0.5% NH3), but the model appears to underpredict the NH3 consumption rate at longer times in less dilute mixtures. At short reaction times, thermal dissociation of NH3, together with the NH3 + H reaction, controls conversion. At longer times, secondary reactions involving NH2 and NH become important due to their impact on the radical pool. Predictions become sensitive to formation and consumption of diazene (tHNNH and cHNNH). Several of the key steps in the ammonia pyrolysis mechanism are radical-radical reactions that are difficult to measure accurately and challenging to calculate theoretically, and a more comprehensive experimental characterization is desirable to support further model development.

Thermal and Catalytic Decomposition of 2-Hydroxyethylhydrazine and 2-Hydroxyethylhydrazinium Nitrate Ionic Liquid

To develop chemical kinetics models for the combustion of ionic liquid-based monopropellants, identification of the elementary steps in the thermal and catalytic decomposition of components such as 2-hydroxyethylhydrazinium nitrate (HEHN) is needed but is currently not well understood. The first decomposition step in protic ionic liquids such as HEHN is typically the proton transfer from the cation to the anion, resulting in the formation of 2-hydroxyethylhydrazine (HEH) and HNO3. In the first part of this investigation, the high-temperature thermal decomposition of HEH is probed with flash pyrolysis (<1400 K) and vacuum ultraviolet (10.45 eV) photoionization time-of-flight mass spectrometry (VUV-PI-TOFMS). Next, the investigation into the thermal and catalytic decomposition of HEHN includes two mass spectrometric techniques: (1) tunable VUV-PI-TOFMS (7.4-15 eV) and (2) ambient ionization mass spectrometry utilizing both plasma and laser ionization techniques whereby HEHN is introduced onto a heated inert or iridium catalytic surface and the products are probed. The products can be identified by their masses, their ionization energies, and their collision-induced fragmentation patterns. Formation of product species indicates that catalytic surface recombination is an important reaction process in the decomposition mechanism of HEHN. The products and their possible elementary reaction mechanisms are discussed.

The prediction of nitric oxide conversion by dielectric barrier discharge using an artificial neural network model

NO conversion to NO2 by DBD (Dielectric Barrier Discharge) was investigated in the N2/O2/NO system. Since NO2 could be generated from NO oxidation by O species, the increase of specific energy input (SEI), function of discharge power and residence time, facilitated the production of O radicals, promoting NO2 production. However, high temperature accomplished by DBD inhibit the NO2 generation to some extent. Also, the conversion is affected by stoichiometric ratio, i.e., oxygen content and inlet NO concentration, which makes a challenge to characterize and predict the products using traditional methods, such as chemical kinetic model. To address above problem, an artificial neural network (ANN) model was developed to predict NO conversion by DBD in the N2/O2/NO system. The experimental data was adopted to train the proposed ANN model in order to simulate and predict the concentrations of NO, NO2, N2O and NOx during reactions. Good agreement was observed between the simulated results and the validated tests. The ANN model showed that inlet NO concentration plays a dominant role in NO2 generation, accounting for 36.22%, followed by residence time and discharge power, which were 26.25% and 23.52%, respectively. O2 content has marginal effect, taking 14.01%. As a byproduct, N2O was much more affected by stoichiometric ratio, which accounted for 64.75%, compared to 35.25%, belonging to discharge power and residence time.

Experimental investigation of the NOx formation and control during the self-sustaining incineration process of N-containing VOCs (DIMETHYLFORMAMIDE)

An experimental investigation was conducted on N,N-dimethylformamide (DMF) pyrolysis at medium-temperature followed by extremely fuel-lean combustion. Furthermore, the NH3-SNCR (Selective non-catalytic reduction) method was studied to control NOx produced in DMF oxidation. Jet-stirred reactors (JSRs) were used in experimental investigation, because the uniform gas-phase mixing state formed by high-speed turbulence in JSR makes the validation of detailed models easier. The major gaseous species produced by pyrolysis, oxidation, and SNCR, namely H2, N2, CO, CO2, NOx, N2O, HCN, and CxHy, are quantified because the mechanism of NOx reduction will be elaborated using these species. The results show that the main nitrogen-containing pyrolysis products are HCN and N2, taking up 65% and 25% of DMF nitrogen, while carbon-containing pyrolysis products are mostly CO, CH4 and HCN. The HCN concentration increases significantly by 42.13% as pyrolysis time increases from 1.5 to 7 s. In oxidation, HCN and N2O concentration peaks are at 650 °C and 750 °C respectively, and NO concentration increases as temperature enhances when it is over 800 °C. A higher ratio of NO/N2O concentration was shown in oxidation of the higher equivalence ratio. The de-NOx efficiency of NH3-SNCR on oxidation flue gas peaked in range 825–875 °C, and as the NH3/NO ratio increased to more than 2.5, NO removal rate tended to reach the maximum of about 50%. The N2O removal rate rose significantly as temperature exceeded 900 °C in SNCR. The results shows the feasibility of NO emission control with DMF containing VOCs incineration in current industrial applications·NH3-SNCR at 825–875 °C shows significant de-NOx effect, but not a proper solution to limit N2O emission at the same time. This study could provide guidance for designing and optimizing the incinerator parameters and its de-NOx system, as well as provide validation data for future chemical kinetic model capable of predicting DMF combustion.

Lumped chemical kinetic modelling of raw and torrefied biomass under pressurized pyrolysis

Accurate prediction of the yield and composition of pyrolysis products is an important requirement for the design and operation of pyrolysis reactors and gasifiers. In this paper, a new semi-global kinetic reaction scheme is proposed to predict the composition of pyrolytic volatiles (classified as main chemical family groups), non-condensable gases and char derived from both raw and torrefied biomass for a wide range of operating conditions. The model is based on an adjustable mechanistic reaction scheme, which includes a combination of three different sub-mechanisms for the primary pyrolysis of three reference biopolymers (cellulose, hemicelluloses and lignin) and the secondary pyrolysis of their respective intermediates. The extent of primary/secondary reactions is varied according to the main process features (linear heating rate, temperature, pyrolysis time, volatile residence time and pressure). The secondary reactions in the scheme involve liquid-phase reactions of high molecular weight intermediates (producing non-condensable gases, water vapour and secondary char) as well as homogeneous and heterogeneous gas-phase conversion of primary volatiles. The model predictions were validated using experimental data obtained from fast pyrolysis in different micropyrolyzers (at 500–600 °C and heating rates of 27 and 110 °C/s, respectively) and slow pyrolysis in a laboratory-scale high-pressure fixed bed reactor (at 400–600 °C, 7 °C/min and 1, 15 and 30 bar). In general, the comparison of model outputs and experimental data were satisfactory, and the model predicted accurate trends in product distribution for changes of the lignocellulosic composition (the pre-removal of hemicelluloses in the case of torrefied biomass), heating rate and pressure. The model correctly predicted a significant increase in char yield (14.6 wt%) when torrefied instead of raw biomass was pyrolyzed due to the significance of char-forming reactions during pyrolysis of torrefied biomass. Moreover, the model’s reliability was proven through its accurate prediction of various condensate groups in bio-oil produced in a micropyrolyzer (maximum deviation < 4 wt%). Corresponding to the experimental data, the model predictions showed that the effect of pressure was most significant in the range of 1–15 bar (bio-oil yield decreased by 5.4 wt%), whereas no significant effect in bio-oil yield was evident for a pressure increase in the range of 15–30 bar. The CO2 and CO yields were slightly under-predicted by around 3 wt%, attributed to the catalytic effects of inherent inorganics on secondary cracking reactions which were not considered in the reaction scheme. Future work should focus on the validation of the model at temperatures below 400 °C.

Modeling electron beam irradiation of methane

AbstractWe built a chemical kinetic model for the electron beam irradiation of methane and report simulation results with dose rates ranging from 2 to 200 kGy s–1 at 298 K and 1 atm pressure. The model contains 92 species and 778 gas‐phase reactions. We report the time evolution of concentrations of stable products (including H2, C2H6, C3H8, C2H4, C3H6, C4H10, C2H2, and C3H4) as well as some radicals and ions. We discuss how yields of products depend on dose rate and how they change during the course of irradiation. To understand the processes controlling product formation, we quantify the extent to which various reactions produce and destroy major products and the key radicals and ions. Normalized sensitivity coefficients are computed for the production of stable products to gain further insight into factors controlling product yields. We were able to reduce the mechanism to 63 species and 331 reactions while incurring less than 5% error in the final concentrations of stable products.