Kinetic Modeling Study Research Articles

Thermal Decomposition and Explosion Characteristics of Benzoyl Peroxide: An Experimental and Kinetic Modeling Study

ABSTRACT Benzoyl peroxide (BPO), commonly used in industry, with highly susceptible to thermal decomposition and explosion. It is essential to understand its explosive properties and to develop a comprehensive chemical kinetic model. This work investigates the thermal decomposition and explosion characteristics and analyze the explosion products. A kinetics model for BPO was developed using quantum chemistry methods. By integrating reaction kinetics and thermodynamic mechanisms from the Reaction Mechanism Generator (RMG) and ReaxFF molecular dynamics simulation, the kinetic mechanism of small molecules was introduced, optimizing the BPO reaction kinetic model. This analysis revealed additional pathways and changes in reaction intermediates. The kinetic model accurately predicts BPO explosion behavior when compared with experimental results for various BPO concentrations.

A kinetic modelling study of ammonia oxidation in a flow reactor

A kinetic modelling study of ammonia oxidation in a flow reactor

Experimental and kinetic modelling study for unconventionally lean and rich methane flames at atmospheric pressure

Experimental and kinetic modelling study for unconventionally lean and rich methane flames at atmospheric pressure

An experimental and kinetic modeling study of NO oxidation over Pt/Al2O3 catalysts: Effects of co-fed propane and Pt particle size

An experimental and kinetic modeling study of NO oxidation over Pt/Al2O3 catalysts: Effects of co-fed propane and Pt particle size

Experimental and kinetic modeling study of oxidative degradation of benzene and phenol in supercritical water.

Benzene and phenol are representative aromatic compounds existing commonly in wastewater. The kinetics of oxidative degradation of benzene and phenol in supercritical water have been investigated in a flow reactor at 823K and 250atm, with the excess oxygen ratio ranging from 0.5 to 2.0. For supercritical water oxidation of benzene, CO2 was observed as the main product accounting for the largest fraction of the reacted carbon. Its concentration was higher than that of CO under all conditions, even at the initial reaction periods where benzene conversions were low. The phenol conversion was found to accelerate with increasing excess oxygen ratio, exhibiting strong dependence on oxygen concentration. CO2 and CO were the major gaseous products with comparable concentrations, and C2H2 was also formed in considerable amounts. A comprehensive chemical kinetic model was developed based on a gas-phase mechanism, and its performance was further validated by comparing to experimental data from different sources. The model reproduced the benzene and phenol conversions and CO concentration fairly well, but underpredicted the CO2 yield and overpredicted the C2H2 yield slightly. Reaction mechanisms were then inferred through kinetic analyses, emphasizing the importance of C6H5OO and C6H5O radicals. Finally, the kinetic characteristics of benzene and phenol oxidation in supercritical water and gas-phase environments were compared.

Monte Carlo study of the two-dimensional kinetic Ising model under a nonantisymmetric magnetic field

Monte Carlo study of the two-dimensional kinetic Ising model under a nonantisymmetric magnetic field

Efficient magnetic adsorption of polystyrene nanoplastic from aqueous solutions by eco-friendly Fe3O4 nanoparticles: Removal, kinetic and isotherm modeling studies

Efficient magnetic adsorption of polystyrene nanoplastic from aqueous solutions by eco-friendly Fe3O4 nanoparticles: Removal, kinetic and isotherm modeling studies

An experimental and kinetic modeling study of the ignition of methane/n-decane blends

An experimental and kinetic modeling study of the combustion of methane/n-decane blends is performed. Ignition delay times (IDTs) of the pure fuels in addition to their blends are measured using both a shock tube and a rapid compression machine at three different methane/n-decane (mol%) compositions of 99/1 (M99D1), 95/5 (M95D5), and 80/20 (M80D20) in ‘air’, over the temperature range of 610–1495 K, at a pressure of 30 bar. A new chemical kinetic mechanism, GalwayMech1.0, is proposed to describe the combustion of these blends and is validated against the new IDT data including 1st-stage and total IDTs as well as existing experimental n-decane data available in the literature. Sensitivity analyses reveal that H-atom abstraction from n-decane by methyl peroxy radicals (CH3Ȯ2) play an important role in promoting blend reactivity at intermediate temperatures, which is not observed for pure n-decane. By investigating the effect of the n-decane concentration on the ignition characteristics, we found that the low ignition temperature limit is extended with increasing n-decane content with a non-linear reactivity-promoting effect. Flux analyses reveal that CH4 oxidation in the blends is initiated via CH4 + ȮH = ĊH3 + H2O, driven by the ȮH radicals produced from the early oxidation of n-decane and the CH3Ȯ2 radicals formed from CH4 oxidation which subsequently accelerates nC10H22 consumption via H-atom abstraction. Comparisons of CH4/nC10H22 and H2/nC10H22 blends from a previous study demonstrate consistently higher reactivity for hydrogen blending compared to methane and that the magnitude of this increase diminishes with increasing n-decane content. Finally, we also compare our current model predictions of our new data with other n-decane models available in the literature.

A detailed analysis of the key steps of the cyclopentene autoignition mechanism from calculated RRKM rate constants associated with ignition delay time simulations

Cyclopentene, a prototype for studying the combustion chemistry of cyclic olefins, appears in the oxidation of cyclic hydrocarbons and can provide key information in the understanding of the formation of polycyclic aromatic hydrocarbons. The ▪ addition to the double-bond is one of the main steps in low-temperature oxidation mechanisms of unsaturated organic compounds. In the case of cyclopentene, addition of ▪ yields a hydroxycyclopentyl radical, that can further react with O2. In this work, we studied the potential energy surface and reaction rates for the subsequent reactions of O2 with the hydroxycyclopentyl radical. The temperature and pressure dependence of the rate constants were determined using master equation simulations, with microcanonical rate coefficients calculated by RRKM theory. The potential energy surface was extracted from high-level electronic structure theory, based on geometries and frequencies obtained using density functional theory. Our results indicate that a Waddington-type mechanism, which produces glutaraldehyde and regenerates ▪ , is the dominant reaction pathway. However, at low-temperatures, a secondary pathway leading to the formation of epoxycyclopentanol and ▪ becomes equally significant. The thermochemistry of all ▪ radicals involved were also evaluated. The kinetic and thermodynamic data were incorporated into a comprehensive mechanism of cyclopentene autoignition, in order to simulate the associated ignition delays. The updated reaction mechanism resulted in shorter ignition delays compared to the non-updated mechanism. Sensitivity analysis was performed to identify the primary contributors.Novelty and Significance StatementCyclopentene is an important intermediate in the oxidation of cyclic olefins and serves as a precursor in the formation of polycyclic aromatic hydrocarbons. Kinetic modeling studies require detailed information on elementary reactions, much of which is typically unavailable from experiments. The novelty and significance of this study lie in the theoretical calculations of rate constants for key reactions in the oxidation of cyclopentene and their evaluation within the comprehensive mechanism proposed by Lokachari et al. The results demonstrate that the studied reactions significantly influence the ignition delays of cyclopentene at low temperatures. Furthermore, the data presented here can be applied in future studies focusing on the oxidation of cyclic olefins.

An experimental and kinetic modeling study on the auto-ignition of ammonia/butan-1-ol mixtures

Ignition delay times (IDTs) of ammonia(NH3)/butan-1-ol mixtures with NH3/butan-1-ol mole ratios of 100/0, 95/5, 90/10 and 70/30 were measured behind reflected shock waves in a shock tube over a range of experimental conditions: temperature range of 1100 – 2000 K, pressures of 0.14 and 0.5 MPa, equivalence ratios of 0.5, 1.0 and 2.0. A new NH3/butan-1-ol reaction mechanism, capable of predicting the experimental results reliably, was developed. Chemical kinetic analyses were performed with the model. It is demonstrated that increasing the content of butan-1-ol in the reaction system results in a non-linear trend of shortening on the IDTs of mixtures, adding 5 % molar fraction of butan-1-ol results in shortening rates of over 70 %. As the butan-1-ol blending ratio increases from 5 % to 30 %, the discrepancy in IDT of the mixture between equivalence ratios of 0.5 and 1.0 diminishes while it remains more pronounced between equivalence ratios of 1.0 and 2.0. The presence of butan-1-ol does not change the oxidation pathways of the NH3 mixture. R72(NH3 + M = NH2 + H + M) and R75(NH2 + HO2 = NH3 + O2) are key reactions to activate chain reactions of the NH3 mixture during the initial reaction stage, for a temperature of 1500 K, a pressure of 0.14 MPa, and an equivalence ratio of 1.0. Reactive radicals produced through the process of butan-1-ol oxidation result in a significant increase in the initial dehydrogenation consumption rate of NH3, by a factor of 5 ∼ 6 powers of ten, accelerating chain reactions.

Application of a magnetic graphene nanocomposite modified with 5-aminoisophthalic acid amine group for chromium (VI) adsorption from aqueous solutions: kinetic and thermodynamic studies

ABSTRACT Polymer nanocomposites are composite materials that incorporate nanomaterials, such as magnetic graphene oxide (mGO), into a polymer matrix. To enhance its adsorption capacity, the surface of mGO nanoparticles was polymerised by a 5-aminoisophthalic acid amine group (mGO-AIPA) through a simplified co-precipitation method. The structural and morphological characteristics of the synthesised nanoparticles were evaluated through techniques such as X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Field emission scanning electron microscopy (FESEM), Thermogravimetric analysis (TGA), and Vibrating sample magnetometer (VSM). Response surface method (RSM) was used to evaluate the effectiveness of mGO-AIPA nanocomposite in removing chromium (VI) ions by examining variables such as solution of pH, contact time, adsorbent dose and initial concentration. Also, the study of kinetic models, adsorption isotherms and thermodynamic modelling of the process were evaluated. The results found that the mGO-AIPA nanocomposite has the maximum removal of chromium (VI) ions from the aqueous solution by 83.11% in optimal conditions including pH 3.5, contact time of 35 min, an adsorbent dosage of 25 mg g−1 and an initial concentration of 55 mg L−1. The pseudo-second-order kinetic and Langmuir isotherm models had a better fit with the experimental data of adsorption and the maximum adsorption capacity of chromium (VI) the base of the Langmuir model was 90.91 mg g−1. Moreover, the thermodynamic analysis indicated that the process was exothermic and nonspontaneous process, implying that it was energetically unfavourable. These findings suggest that the mGO-AIPA nanocomposite has a high performance as an effectual adsorbent to eliminate chromium heavy metal from an aqueous medium.

Evaluation of Biochemical Methane Potential and Kinetics of Organic Waste Streams for Enhanced Biogas Production

Organic waste has the potential to produce methane gas as a substitute for petrol-based fuels, while reducing landfilling and possible environmental pollution. Generally, anaerobic digestion (AD) is used only in wastewater treatment plants as a tertiary stage of sewage sludge treatment, generating a fraction of the energy that such process plants require. In this study, four different wastes—food waste (FW), dairy industry waste (DIW), brewery waste (BW), and cardboard waste (CBW)—were tested for biogas production. The biochemical methane potential (BMP) of each sample was evaluated using an automatic methane potential system (AMPTS). Operating parameters such as pH, temperature, total solids, and volatile solids were measured. Experiments on the anaerobic digestion of the samples were monitored under mesophilic conditions (temperature 37 °C, retention time 30 days). Specific methane yields (SMYs), as well as the theoretical methane potential (BMPth), were used to calculate the biodegradability of the substrates, obtaining the highest biodegradability for BW at 95.1% and producing 462.3 ± 1.25 NmL CH4/g volatile solids (VS), followed by FW at an inoculum-to-substrate ratio (ISR) of 2 at 84% generating 391.3 NmLCH4/g VS. The BMP test of the dairy industry waste at an inoculum-to-substrate ratio of 1 was heavily inhibited by bacteria overloading of the easily degradable organic matter, obtaining a total methane production of 106.3 NmL CH4/g VS and a biodegradability index of 24.8%. The kinetic modeling study demonstrated that the best-fitting model was the modified Gompertz model, presenting the highest coefficient of determination (R2) values, the lowest root means square error (RMSE) values for five of the substrates, and the best specific biogas yield estimation with a percentage difference ranging from 0.3 to 3.6%.

An experimental and kinetic modeling study on the ignition property of an alternative gas to liquid jet fuel

Alternative jet fuel from Fischer-Tropsch (FT) synthesis represents an important kind of aviation fuel in the near future. However, the combustion properties of FT jet fuel have not been fully explored yet. Herein, this work reports an experimental and kinetic modeling study on the ignition characteristics of a coal-derived FT jet fuel. To facilitate its usage as a “drop-in” fuel in current aircraft and infrastructure, a blended fuel of the present FT fuel with a traditional RP-3 jet fuel with relatively high aromatic hydrocarbons is also prepared and studied. Specifically, a shock tube facility is employed to measure the ignition delay times (IDTs) of the FT, RP-3, and the blended jet fuels under the combustion conditions, i.e., temperature ranging from 1000–1800 K, pressure at 3 and 10 bar, equivalence ratio at 0.5, 1.0, and 2.0. Two-dimensional gas chromatography (GC × GC) analysis is adopted to determine the chemical compositions of the FT and RP-3 jet fuels, which is then used to aid the development of surrogate models. Most importantly, the contemporary combustion chemical kinetic mechanism via detailed generation, automatic generation, lumping, decoupling and HyChem methods are employed to model the IDTs, and the mechanism reproducibility of these mechanisms are systematically compared. The present work should be valuable to understand the chemical structure effect on alternative jet fuels and also provides important information for the development of different kinds of combustion kinetic mechanisms.

Elimination of methylene blue dye from the aqueous solution using waste fig fruit as an activated carbon: a case study of nonlinear adsorption isotherm models and kinetic models

Elimination of methylene blue dye from the aqueous solution using waste fig fruit as an activated carbon: a case study of nonlinear adsorption isotherm models and kinetic models

Unveiling the low‐temperature oxidation chemistry of dipropyl carbonate

AbstractDialkyl carbonates (DACs) own an environmentally friendly synthesis route, making them potential candidates as alternative fuels. However, for DACs to be widely accepted as an alternative fuel, a comprehensive understanding of their combustion behavior is essential. Dipropyl carbonate (DPrC) represents a transition from short‐chain to mid‐chain carbonates, understanding its combustion behaviors holds significance in unraveling the combustion chemistry of carbonates. In this study, the oxidation of DPrC was investigated with the initial fuel mole fraction of 0.5% at three equivalence ratios of 0.5, 1.0, and 2.0 within a temperature range of 550–1100 K in a jet‐stirred reactor for the first time. Gas chromatography was utilized for the quantitative detection of reactants, intermediates, and products. A detailed DPrC mechanism was first developed, and good agreements between measurements and simulations were obtained. A notable negative temperature coefficient (NTC) behavior was first observed in the oxidation of DACs. Such NTC phenomenon occurred at fuel‐lean conditions in the temperature range of 620–660 K, while only a weak low‐temperature consumption was observed at the stoichiometric condition. Kinetic modeling studies showed that this unique low‐temperature chemistry of DPrC can be attributed to the differences in the RO2 isomerization reactions between DPrC and short‐chain DACs. The RO2 isomerization via a six‐member ring transition state could happen in DPrC oxidation but not in dimethyl carbonate and diethyl carbonate oxidation, due to the different fuel molecular structure. Therefore, the subsequent reaction pathways via QOOH → O2QOOH → HO2Q = O + OH → OQ = O + OH were promoted and two OH radicals were released in this process. Moreover, it is conceivable that mid or long‐chain DACs could also exhibit an NTC phenomenon due to the increased potential for RO2 isomerization via a six‐ or seven‐member ring transition state, thereby increasing the likelihood of RO2 isomerization occurrence.

Nocturnal atmospheric synergistic oxidation reduces the formation of low-volatility organic compounds from biogenic emissions

Abstract. Volatile organic compounds (VOCs) are often subject to synergistic oxidation by different oxidants in the atmosphere. However, the exact synergistic-oxidation mechanism of atmospheric VOCs and its role in particle formation remain poorly understood. In particular, the reaction kinetics of the key reactive intermediates, organic peroxy radicals (RO2), during synergistic oxidation is rarely studied. Here, we conducted a combined experimental and kinetic modeling study of the nocturnal synergistic oxidation of α-pinene (the most abundant monoterpene) by O3 and NO3 radicals as well as its influences on the formation of highly oxygenated organic molecules (HOMs) and particles. We find that in the synergistic O3 + NO3 regime, where OH radicals are abundantly formed via decomposition of ozonolysis-derived Criegee intermediates, the production of CxHyOz HOMs is substantially suppressed compared to that in the O3-only regime, mainly because of the depletion of α-pinene RO2 derived from ozonolysis and OH oxidation by those arising from NO3 oxidation via cross reactions. Measurement–model comparisons further reveal that the cross-reaction rate constants of NO3-derived RO2 with O3-derived RO2 are on average 10–100 times larger than those of NO3-derived RO2 with OH-derived RO2. Despite a strong production of organic nitrates in the synergistic-oxidation regime, the substantial decrease in CxHyOz HOM formation leads to a significant reduction in ultralow- and extremely low-volatility organic compounds, which significantly inhibits the formation of new particles. This work provides valuable mechanistic and quantitative insights into the nocturnal synergistic-oxidation chemistry of biogenic emissions and will help to better understand the formation of low-volatility organic compounds and particles in the atmosphere.

Hybrid composite beads of chitosan/graphene oxide for dye adsorption: characterizations, kinetic modeling and toxicity study

The current study aimed to the preparation of graphene oxide impregnated chitosan– polyvinyl alcohol hybrid beads (GO/CS-PVA) for the removal of Reactive Black 5 (RB5) dye from wastewater solutions, presenting them as a cost-effective alternative for wastewater treatment. These hybrid beads were fabricated using a dripping technique in an aqueous solution. The surface and structure of the material before and after adsorption process were studied by analyzing FTIR spectroscopy and Scanning electron microscope (SEM) as well as adsorption capacity was also evaluated. The results proved the successful synthesis of GO/CS-PVA beads and elucidated the physical adsorption mechanism of RB5. SEM images revealed uniform spherical beads with a rough surface, approximately 752 μm in diameter. Additionally, the evaluation of adsorption capacity showed that the optimum condition for RB5 adsorption is at pH = 3 while the kinetic investigations revealed that the adsorption process adhered to the pseudo-second-order model, indicating a chemisorption reaction. Furthermore, an increase in temperature from 25 to 65 °C enhanced the maximum adsorption capacity of GO/CS-PVA beads by 34%. The cytotoxic effect of the hybrid as measured on adipose derived stem cells via the MTT assay was negligible. In conclusion, it was proved that the eco-friendly GO/CS-PVA beads adsorbents can efficiently remove RB5 from wastewater in practical applications.

Efficient photocatalytic degradation of chloramphenicol from contaminated water over rGO@MoS2 nanocomposites

Antibiotics-based effluents pose a severe threat to the natural ecosystem by acting as reservoirs for the growth of drug-resistant bacteria if untreated. Herein, a facile and scalable approach was developed to engineer photocatalysts associating reduced graphene oxide (rGO) and molybdenum disulfide (rGO@MoS2) that were used for the degradation of chloramphenicol (CAP) from contaminated water under UV-light. The hydrothermally produced rGO@MoS2 catalysts contain CO, COH, and COC functional groups that contribute to the binding of CAP onto their surface. The rGO surface modification with MoS2 layers offers a high surface area for light absorption. Results show that the rGO@MoS2 catalyst (1:1 w/w) exhibits the highest degradation efficiency (DE) of 86 % within 180 min of light exposure at neutral pH. Further, the kinetic modelling studies for CAP degradation by rGO@MoS2 1:1 showed high linearity with pseudo-first order kinetics (R2 ∼ 0.9). The isotherm modelling studies correspond to Langmuir isotherm (R2 ∼ 0.99), suggesting monolayer-type interaction of CAP with the photocatalyst surface during photodegradation. Furthermore, the mechanism of degradation elucidated using scavenging experiments showed the involvement of both holes (h+) and electrons (e−) that contribute to the degradation of CAP by generating reactive oxygen species (ROS) like OH● and O2●− radicals. The applicability of the rGO@MoS2 photocatalyst towards the degradation of CAP was tested in Ganga water, wherein a similar ∼86 % CAP removal was observed. Furthermore, the photocatalyst was found to be stable and could be reused five times. Overall, these findings demonstrate the usefulness of the rGO@MoS2 1:1 composite as an efficient photocatalyst that can be used for the degradation of harmful organic pollutants from water bodies to provide a safer and cleaner environment.

Effect of 4,4′-dialkyl-2,2′-bipyridine ligands on the hydrolysis of dichlorodioxomolybdenum(VI) catalyst precursors and the switch from homogeneous epoxidation to heterogeneous systems

Molybdenum catalysts have been industrially recognized for decades for liquid phase epoxidation, which is an important chemical reaction process, since epoxides are used for many industrial applications. In this work, molybdenum oxide hybrid catalysts, prepared by a reflux hydrolysis methodology, performed effectively as heterogeneous catalysts or reaction-induced self-separating catalysts under mild reaction conditions; in the two cases, the catalyst separation and reuse are facilitated. Specifically, catalysts with the general formula [MoO3(L)], possessing polymeric chain-like (L = 4,4′-dimethyl-2,2′-bipyridine (1)) or oligomeric (L = 4,4′-dinonyl-2,2′-bipyridine (2)) structures comprising corner-sharing {MoO4N2} units, were synthesized and characterized by various complementary techniques (ATR FT-IR, Raman, 13C{1H} CP MAS NMR spectroscopy, PXRD, SEM, TGA, elemental analysis, ICP-OES and N2 sorption isotherms). Small chemical differences in the organic synthesis precursor had important structure directing effects on the type of hybrid material formed. The hybrids promoted olefin epoxidation with H2O2 or tert-butylhydroperoxide (TBHP) as oxidant. For example, 1 catalyzed the conversion of biobased olefins (70 °C) and lignin-based isoeugenol (50 °C) with TBHP to useful bioproducts, in heterogeneous phase, leading to an epoxide yield of 100 % for DL-limonene (3:1 M molar ratio of 1,2-epoxy-p-menth-8-ene to 1,2:8,9-diepoxy-p-menthane), 81 % epoxide yield for fatty acid methyl esters, and 80 % Licarin A selectivity at 40 % isoeugenol conversion. For dienes (DL-limonene, methyl linoleate), kinetic modelling studies suggested that the formation of the monoepoxides was faster than that of diepoxides, accounting for enhanced monoepoxide selectivity.

Facile synthesis of zeolitic‐imidazole framework‐67 (ZIF‐67) for the adsorption of indigo carmine dye

AbstractThis study aims to synthesize ZIF‐67 for the adsorption of indigo carmine (I.C.) dye. ZIF‐67 materials were synthesized under different conditions and the synthesis condition of ZIF‐67 giving the best adsorption efficiency was obtained. In batch adsorption studies, pH, adsorbent amount, contact time, initial dye concentration, and temperature effects were investigated. Adsorption data were applied to Langmuir, Freundlich, and Temkin isotherm models. The best correlation value was obtained in Langmuir isotherm (R2 = 0.999). The adsorption of I.C. dye with ZIF‐67 occurred in a monolayer with a homogeneous surface according to Langmuir isotherm. The highest adsorption capacity value of ZIF‐67 metal–organic framework for I.C. dye was found as 370 mg/g. Kinetic model studies were also performed and pseudo first‐order, pseudo second‐order, and intraparticle diffusion models were used. Pseudo second‐order was the best fitting kinetic model to the data (R2 = 0.997). Adsorption mechanisms of ZIF‐67 for I.C. dye include electrostatic interaction, π–π interaction, and hydrogen bonding. Thermodynamic studies showed that I.C. removal by ZIF‐67 is an exothermic and spontaneous process. ZIF‐67 was characterized by X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FT‐IR), field emission scanning electron microscope (FE‐SEM), and N2 adsorption–desorption. The surface area of synthesized ZIF‐67 was found 1493 m2 g−1. The salt concentration effect on I.C. adsorption by ZIF‐67 was also investigated, showing an increase in adsorption capacities with increasing salt concentration. The regeneration study was carried out and after 5 cycles, the reduction in efficiency was 21%.