scholarly journals Computational Studies on the Thermodynamic and Kinetic Parameters of Oxidation of 2-Methoxyethanol Biofuel via H-Atom Abstraction by Methyl Radical

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Mohamed A. Abdel-Rahman ◽  
Tarek M. El-Gogary ◽  
Nessreen Al-Hashimi ◽  
Mohamed F. Shibl ◽  
Kazunari Yoshizawa ◽  
...  
Keyword(s):  
Kinetic Parameters ◽  
Energy Surface ◽  
Elevated Temperatures ◽  
State Theory ◽  
Rate Coefficients ◽  
Methyl Radical ◽  
Energy Barriers ◽  
Oxidation Of Organic Compounds ◽  
Thermodynamic And Kinetic Parameters ◽  
Kinetics Of

Abstract In this work, a theoretical investigation of thermochemistry and kinetics of the oxidation of bifunctional 2-Methoxyethanol (2ME) biofuel using methyl radical was introduced. Potential-energy surface for various channels for the oxidation of 2ME was studied at density function theory (M06-2X) and ab initio CBS-QB3 levels of theory. H-atom abstraction reactions, which are essential processes occurring in the initial stages of the combustion or oxidation of organic compounds, from different sites of 2ME were examined. A similar study was conducted for the isoelectronic n-butanol to highlight the consequences of replacing the ϒ CH2 group by an oxygen atom on the thermodynamic and kinetic parameters of the oxidation processes. Rate coefficients were calculated from the transition state theory. Our calculations show that energy barriers for n-butanol oxidation increase in the order of α ‹ O ‹ ϒ ‹ β ‹ ξ, which are consistent with previous data. However, for 2ME the energy barriers increase in the order α ‹ β ‹ ξ ‹ O. At elevated temperatures, a slightly high total abstraction rate is observed for the bifunctional 2ME (4 abstraction positions) over n-butanol (5 abstraction positions).

scholarly journals Theoretical study of the addition and hydrogen abstraction reactions of the methyl radical with formaldehyde and hydroxymethylene

2018 ◽  
Vol 83 (10) ◽  
pp. 1113-1122
Author(s):  
Huu Nguyen ◽  
Xuan Nguyen
Keyword(s):  
Transition State Theory ◽  
Energy Surface ◽  
Theoretical Study ◽  
Hydrogen Abstraction ◽  
Single Point ◽  
State Theory ◽  
Hydrogen Atom Abstraction ◽  
Methyl Radical ◽  
Variational Transition State Theory ◽  
Kinetics Of

The mechanism, thermochemistry and kinetics of the addition and hydrogen-atom abstraction reactions of the methyl radical with formaldehyde and hydroxymethylene were investigated by ab initio calculations. The potential energy surface (PES) of the reactions were calculated by single point calculations at the CCSD(T)/6-311++G(3df,2p) level based on geometries at the B3LYP/6-311++G(3df,2p) level. The rate constants of various product channels were estimated by the variational transition state theory (VTST) and are discussed for the seven reactions in the temperature range of 300?2000 K and at 101325 Pa pressure. The calculated results showed that all the hydrogen abstraction reactions are more favorable than the addition ones.

scholarly journals Effect of ammonia and water molecule on OH + CH3OH reaction under tropospheric condition

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Mohamad Akbar Ali ◽  
M. Balaganesh ◽  
Faisal A. Al-Odail ◽  
K. C. Lin
Keyword(s):  
Water Molecule ◽  
Energy Surface ◽  
Rate Coefficient ◽  
Water Concentration ◽  
State Theory ◽  
Rate Coefficients ◽  
Hydrogen Atoms ◽  
Experimental And Theoretical Studies ◽  
Effective Reaction ◽  
Effective Reaction Rate

AbstractThe rate coefficients for OH + CH3OH and OH + CH3OH (+ X) (X = NH3, H2O) reactions were calculated using microcanonical, and canonical variational transition state theory (CVT) between 200 and 400 K based on potential energy surface constructed using CCSD(T)//M06-2X/6-311++G(3df,3pd). The results show that OH + CH3OH is dominated by the hydrogen atoms abstraction from CH3 position in both free and ammonia/water catalyzed ones. This result is in consistent with previous experimental and theoretical studies. The calculated rate coefficient for the OH + CH3OH (8.8 × 10−13 cm3 molecule−1 s−1), for OH + CH3OH (+ NH3) [1.9 × 10−21 cm3 molecule−1 s−1] and for OH + CH3OH (+ H2O) [8.1 × 10−16 cm3 molecule−1 s−1] at 300 K. The rate coefficient is at least 8 order magnitude [for OH + CH3OH(+ NH3) reaction] and 3 orders magnitude [OH + CH3OH (+ H2O)] are smaller than free OH + CH3OH reaction. Our calculations predict that the catalytic effect of single ammonia and water molecule on OH + CH3OH reaction has no effect under tropospheric conditions because the dominated ammonia and water-assisted reaction depends on ammonia and water concentration, respectively. As a result, the total effective reaction rate coefficients are smaller. The current study provides a comprehensive example of how basic and neutral catalysts effect the most important atmospheric prototype alcohol reactions.

scholarly journals Thermodynamics and kinetics of DNA nanotube polymerization from single-filament measurements

2015 ◽  
Vol 6 (4) ◽  
pp. 2252-2267 ◽  
Author(s):  
Rizal F. Hariadi ◽  
Bernard Yurke ◽  
Erik Winfree
Keyword(s):  
Kinetic Parameters ◽  
Single Filament ◽  
Common Features ◽  
Thermodynamics And Kinetics ◽  
Polymer Models ◽  
Thermodynamic And Kinetic Parameters ◽  
Model Sharing ◽  
Dna Nanotube ◽  
Kinetics Of

Single-filament measurement of the thermodynamic and kinetic parameters of DNA nanotube assembly supports a polymerization/depolymerization model sharing common features with cytoskeletal polymer models.

scholarly journals Estudo cinético da abstração do hidrogênio do acetato de metila

2020 ◽  
Author(s):  
Leandro da Silva Pereira ◽  
Leonardo Baptista
Keyword(s):  
Transition State Theory ◽  
Methyl Esters ◽  
Hydrogen Abstraction ◽  
State Theory ◽  
Basis Set ◽  
Rate Coefficients ◽  
Dft Methods ◽  
Carbon Chains ◽  
Kinetics Of ◽  
Good Agreement

Biodiesel is a fuel formed by methyl esters with large carbon chains. The investigation of the hydrogen abstraction reactions of small methyl esters can be helpful to the improvement and development of kinetics models of biodiesel combustion. For this reason, the present study aims to study the thermochemistry and kinetics of hydrogen abstraction of methyl ethanoate using DFT methods and transition state theory. The abstraction reactions by O2, O, HO2, and H were studied with the B3LYP-D3 and M06-2X functionals with cc-pVDZ, ccpVTZ, aug-cc-pVDZ, and aug-cc-pVTZ basis set. At 298 K, the rate coefficients evaluated are in good agreement with the literature’s coefficients and the faster reaction occurs in the presence of O atoms. The hydrogen abstraction by O2 molecule it is not important at 298 K, but should be included in the present study since it should be important at higher temperatures.

scholarly journals Theoretical studies on the kinetics of the hydrogen-abstraction reactions from 1,3,5-trioxane and 1,4-dioxane by OH radicals

2020 ◽  
Vol 45 ◽  
pp. 146867831989925 ◽  
Author(s):  
Vahid Saheb ◽  
Aidin Bahadori
Keyword(s):  
Transition State ◽  
Transition State Theory ◽  
Hydrogen Abstraction ◽  
Transition States ◽  
State Theory ◽  
Rate Coefficients ◽  
Cyclic Ethers ◽  
Oh Radicals ◽  
Kinetics Of ◽  
Bonded Complexes

Theoretical investigations have been performed on the kinetics of bimolecular hydrogen-abstraction reactions of 1,3,5-trioxane and 1,4-dioxane cyclic ethers with OH radicals. Hydrogen abstraction from both axial and equatorial positions of 1,3,5-trioxane and 1,4-dioxane was considered. Optimization of the structures, and the calculation of energies, vibrational frequencies and moments of inertia for all the stationary points including reactants, hydrogen-bonded complexes, transition states and products were carried out using density functional theory at the M06-2X level together with the MG3S basis set. Single-point energy calculations on the optimized points were obtained at the CBS-QB3 level. The calculations show that the title reactions proceed through relatively strong hydrogen-bonded complexes due to the hydrogen bonding between the OH radicals and the oxygen atoms of the cyclic ethers. A two-transition state model (an inner tight transition state and an outer loose transition state) was employed to compute the hydrogen-abstraction rate coefficients. The rate coefficients were also computed using conventional transition state theory considering a tight transition state for the purpose of comparison. It was found that when the reactions proceed via inner transition states with relative energies higher than the reactants, the computed rate coefficients are underestimated by conventional transition state theory.

Abstraction and addition kinetics of C2H radicals with CH4, C2H6, C3H8, C2H4, and C3H6: CVT/SCT/ISPE and hybrid meta-DFT methods

2015 ◽  
Vol 17 (5) ◽  
pp. 3142-3156 ◽  
Author(s):  
Manas Ranjan Dash ◽  
B. Rajakumar
Keyword(s):  
Density Functional ◽  
Transition State Theory ◽  
State Theory ◽  
Rate Coefficients ◽  
Dft Methods ◽  
Functional Theory ◽  
Variational Transition State Theory ◽  
Wide Range ◽  
P Rate ◽  
Kinetics Of

Rate coefficients for the reactions of C2H radicals with methane (k1), ethane (k2), propane (k3), ethylene (k4), and propylene (k5) were computed using canonical variational transition state theory (CVT) coupled with hybrid-meta density functional theory (DFT) over a wide range of temperatures from 150 to 5000 K.

scholarly journals Kinetics of the Reactions of Ozone with Halogen Atoms in the Stratosphere

Atmosphere ◽  
2021 ◽  
Vol 12 (8) ◽  
pp. 1053
Author(s):  
S. Vijayakumar ◽  
Duminda S. Ranasinghe ◽  
David M. Wilmouth
Keyword(s):  
Potential Energy ◽  
Potential Energy Surfaces ◽  
Transition State Theory ◽  
State Theory ◽  
Rate Coefficients ◽  
Variational Transition State Theory ◽  
Halogen Atoms ◽  
Reaction Cycles ◽  
Energy Surfaces ◽  
Kinetics Of

It is well established that reaction cycles involving inorganic halogens contribute to the depletion of ozone in the atmosphere. Here, the kinetics of O3 with halogen atoms (Cl, Br, and I) were investigated between 180 and 400 K, expanding the temperature range relative to prior studies. Canonical variational transition state theory including small curvature tunneling correction (CVT/SCT) were considered, following the construction of the potential energy surfaces. MRCI + Q/aug-ano-pVTZ//MP2/aug-cc-pV(T + d)Z and MRCI + Q/aug-ano-RCC-VTZP//MP2/aug-cc-pV(T + d)Z levels of theory were used to calculate the kinetic parameters. Calculated rate coefficients were used to fit the Arrhenius equations, which are obtained to be k1 = (3.48 ± 0.4) × 10−11 exp[(−301 ± 64)/T] cm3 molecule−1 s−1, k2 = (3.54 ± 0.2) × 10−11 exp[(−990 ± 35)/T] cm3 molecule−1 s−1 and k3 = (1.47 ± 0.1) × 10−11 exp[(−720 ± 42)/T] cm3 molecule−1 s−1 for the reactions of O3 with Cl, Br, and I atoms, respectively. The obtained rate coefficients for the reactions of O3 with halogen atoms using CVT/SCT are compared to the latest recommended rate coefficients by the NASA/JPL and IUPAC evaluations. The reactivity trends and pathways of these reactions are discussed.

Influence of medium on alkaline hydrolysis of succinic acid monomethyl and monopropyl esters

1980 ◽  
Vol 45 (11) ◽  
pp. 2873-2882
Author(s):  
Vladislav Holba ◽  
Ján Benko
Keyword(s):  
Succinic Acid ◽  
Kinetic Parameters ◽  
Alkaline Hydrolysis ◽  
Specific Interactions ◽  
Nonaqueous Media ◽  
The Media ◽  
Kinetics Of ◽  
Hydrolysis Of

The kinetics of alkaline hydrolysis of succinic acid monomethyl and monopropyl esters were studied in mixed aqueous-nonaqueous media at various temperatures and ionic strengths. The results of measurements are discussed in terms of electrostatic and specific interactions between the reactants and other components of the reaction mixture. The kinetic parameters in the media under study are related to the influence of the cosolvent on the solvation sphere of the reactants.

Kinetics of temperature-programmed reactivation of a hydrodesulphurization catalyst

1983 ◽  
Vol 48 (12) ◽  
pp. 3340-3355 ◽  
Author(s):  
Pavel Fott ◽  
Pavel Šebesta
Keyword(s):  
Carbon Dioxide ◽  
Thermal Analysis ◽  
Differential Thermal Analysis ◽  
Thin Layer ◽  
Kinetic Parameters ◽  
Diffusion Region ◽  
Reaction Heat ◽  
Gaseous Products ◽  
Temperature Programmed ◽  
Kinetics Of

The kinetic parameters of reactivation of a carbonized hydrodesulphurization (HDS) catalyst by air were evaluated from combined thermogravimetric (TG) and differential thermal analysis (DTA) data. In addition, the gaseous products leaving a temperature-programmed reactor with a thin layer of catalyst were analyzed chromatographically. Two exothermic processes were found to take part in the reactivation, and their kinetics were described by 1st order equations. In the first process (180-400 °C), sulphur in Co and Mo sulphides is oxidized to sulphur dioxide; in the second process (300-540 °C), in which the essential portion of heat is produced, the deposited carbon is oxidized to give predominantly carbon dioxide. If the reaction heat is not removed efficiently enough, ignition of the catalyst takes place, which is associated with a transition to the diffusion region. The application of the obtained kinetic parameters to modelling a temperature-programmed reactivation is illustrated on the case of a single particle.

Rotational de-excitations of C3H+ (1Σ+) by collision with He: new ab initio potential energy surface and scattering calculations

2020 ◽  
Vol 494 (4) ◽  
pp. 5675-5681 ◽  
Author(s):  
Sanchit Chhabra ◽  
T J Dhilip Kumar
Keyword(s):  
Potential Energy ◽  
Potential Energy Surface ◽  
Ab Initio ◽  
Cross Sections ◽  
Energy Surface ◽  
Molecular Ions ◽  
Basis Set ◽  
Rate Coefficients ◽  
Close Coupling ◽  
Collisional Rate Coefficients

ABSTRACT Molecular ions play an important role in the astrochemistry of interstellar and circumstellar media. C3H+ has been identified in the interstellar medium recently. A new potential energy surface of the C3H+–He van der Waals complex is computed using the ab initio explicitly correlated coupled cluster with the single, double and perturbative triple excitation [CCSD(T)-F12] method and the augmented correlation consistent polarized valence triple zeta (aug-cc-pVTZ) basis set. The potential presents a well of 174.6 cm−1 in linear geometry towards the H end. Calculations of pure rotational excitation cross-sections of C3H+ by He are carried out using the exact quantum mechanical close-coupling approach. Cross-sections for transitions among the rotational levels of C3H+ are computed for energies up to 600 cm−1. The cross-sections are used to obtain the collisional rate coefficients for temperatures T ≤ 100 K. Along with laboratory experiments, the results obtained in this work may be very useful for astrophysical applications to understand hydrocarbon chemistry.

Sign in / Sign up

Export Citation Format

Share Document