1
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Wu X, Hou Q, Huang J, Chai J, Zhang F. Exploring the OH-initiated reactions of styrene in the atmosphere and the role of van der Waals complex. CHEMOSPHERE 2021; 282:131004. [PMID: 34082313 DOI: 10.1016/j.chemosphere.2021.131004] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2021] [Revised: 05/19/2021] [Accepted: 05/23/2021] [Indexed: 06/12/2023]
Abstract
Reacting with OH provides a major sink for styrene in the atmosphere, with three possible pathways including OH-addition, H-abstraction and addition-dissociation reactions. However, the total rate coefficients of styrene + OH were measured as 1.2-6.2 × 10-11 cm3 molecule-1 s-1 under atmospheric conditions, varying by a maximum factor of 5. On the other hand, only one theoretical work reported this rate coefficient as 19.1 × 10-11 cm3 molecule-1 s-1, which exhibits up to 16 times that measured in laboratory studies. In the present study, the reaction kinetics of styrene + OH was extensively studied with high-level quantum chemical methods combined with RRKM/master equation simulations. In particular, we carried out theoretical treatments for the formation of pre-reaction Van der Waals complexes of styrene + OH, and examined their influence on the reaction kinetics. The total rate coefficient for styrene + OH is calculated to be 1.7 × 10-11 cm3 molecule-1 s-1 at 300 K, 1 atm. The main products are addβ (88.2%), add5 (6.9%), addα (1.9%) and add3 (1.7%). Using our computed rate coefficient and the global atmospheric hydroxyl radical concentration (2 × 106 radicals per cm3), the lifetime of styrene in the atmosphere is estimated at 8.0 h. The degradation of styrene might be negligible for the formation of ozone in the atmosphere based upon the photochemical ozone creation potentials calculation. The computed product yields indicate that addβ via subsequent reactions could significantly produce formaldehyde and benzaldehyde that were observed in previous experimental studies on styrene oxidation, and contribute to the formation of secondary organic aerosols.
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Affiliation(s)
- Xiaoqing Wu
- Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui, 230026, PR China; National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui, 230029, PR China
| | - Qifeng Hou
- Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui, 230026, PR China
| | - Jiabin Huang
- Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui, 230026, PR China
| | - Jiajue Chai
- Institute at Brown for Environment and Society, And Department of Earth, Environmental and Planetary Sciences, Brown University, 182 Hope St., Providence, RI, 02912, USA
| | - Feng Zhang
- Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui, 230026, PR China.
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2
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Mertens LA, Manion JA. Kinetics of isopropanol decomposition and reaction with H atoms from shock tube experiments and rate constant optimization using the method of uncertainty minimization using polynomial chaos expansions (MUM‐PCE). INT J CHEM KINET 2020. [DOI: 10.1002/kin.21428] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Laura A. Mertens
- Chemical Sciences Division National Institute of Standards and Technology Gaithersburg Maryland
| | - Jeffrey A. Manion
- Chemical Sciences Division National Institute of Standards and Technology Gaithersburg Maryland
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3
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Blázquez S, González D, García-Sáez A, Antiñolo M, Bergeat A, Caralp F, Mereau R, Canosa A, Ballesteros B, Albaladejo J, Jiménez E. Experimental and theoretical investigation on the OH + CH 3C(O)CH 3 reaction at interstellar temperatures (T=11.7-64.4 K). ACS EARTH & SPACE CHEMISTRY 2019; 3:1873-1883. [PMID: 31799490 PMCID: PMC6887536 DOI: 10.1021/acsearthspacechem.9b00144] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The rate coefficient, k(T), for the gas-phase reaction between OH radicals and acetone CH3C(O)CH3, has been measured using the pulsed CRESU (French acronym for Reaction Kinetics in a Uniform Supersonic Flow) technique (T = 11.7-64.4 K). The temperature dependence of k(T = 10-300 K) has also been computed using a RRKM-Master equation analysis after partial revision of the potential energy surface. In agreement with previous studies we found that the reaction proceeds via initial formation of two pre-reactive complexes both leading to H2O + CH3C(O)CH2 by H-abstraction tunneling. The experimental k(T) was found to increase as temperature was lowered. The measured values have been found to be several orders of magnitude higher than k(300 K). This trend is reproduced by calculations, with a special good agreement with experiments below 25 K. The effect of total gas density on k(T) has been explored. Experimentally, no pressure dependence of k(20 K) and k(64 K) was observed, while k(50 K) at the largest gas density 4.47×1017 cm-3 is twice higher than the average values found at lower densities. The computed k(T) is also reported for 103 cm-3 of He (representative of the interstellar medium). The predicted rate coefficients at 10 K surround the experimental value which appears to be very close to the low pressure regime prevailing in the interstellar medium. For gas-phase model chemistry of interstellar molecular clouds, we suggest using the calculated value of 1.8×10-10 cm3 molecule-1 s-1 at 10 K and the reaction products are water and CH3C(O)CH2 radicals.
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Affiliation(s)
- Sergio Blázquez
- Departamento de Química Física. Facultad de Ciencias y Tecnologías Químicas. Universidad de Castilla-La Mancha, Avda. Camilo José Cela, 1B. 13071 Ciudad Real, Spain
| | - Daniel González
- Departamento de Química Física. Facultad de Ciencias y Tecnologías Químicas. Universidad de Castilla-La Mancha, Avda. Camilo José Cela, 1B. 13071 Ciudad Real, Spain
| | - Alberto García-Sáez
- Departamento de Química Física. Facultad de Ciencias y Tecnologías Químicas. Universidad de Castilla-La Mancha, Avda. Camilo José Cela, 1B. 13071 Ciudad Real, Spain
| | - María Antiñolo
- Instituto de Investigación en Combustión y Contaminación Atmosférica (ICCA). Universidad de Castilla-La Mancha, Camino de Moledores s/n. 13071 Ciudad Real, Spain
| | - Astrid Bergeat
- Univ. Bordeaux, CNRS, Bordeaux INP, ISM, UMR 5255, F-33405 Talence, France
| | - Françoise Caralp
- Univ. Bordeaux, CNRS, Bordeaux INP, ISM, UMR 5255, F-33405 Talence, France
| | - Raphaël Mereau
- Univ. Bordeaux, CNRS, Bordeaux INP, ISM, UMR 5255, F-33405 Talence, France
| | - André Canosa
- Univ Rennes, CNRS, IPR (Institut de Physique de Rennes) - UMR 6251, F-35000 Rennes, France
| | - Bernabé Ballesteros
- Departamento de Química Física. Facultad de Ciencias y Tecnologías Químicas. Universidad de Castilla-La Mancha, Avda. Camilo José Cela, 1B. 13071 Ciudad Real, Spain
- Instituto de Investigación en Combustión y Contaminación Atmosférica (ICCA). Universidad de Castilla-La Mancha, Camino de Moledores s/n. 13071 Ciudad Real, Spain
| | - José Albaladejo
- Departamento de Química Física. Facultad de Ciencias y Tecnologías Químicas. Universidad de Castilla-La Mancha, Avda. Camilo José Cela, 1B. 13071 Ciudad Real, Spain
- Instituto de Investigación en Combustión y Contaminación Atmosférica (ICCA). Universidad de Castilla-La Mancha, Camino de Moledores s/n. 13071 Ciudad Real, Spain
| | - Elena Jiménez
- Departamento de Química Física. Facultad de Ciencias y Tecnologías Químicas. Universidad de Castilla-La Mancha, Avda. Camilo José Cela, 1B. 13071 Ciudad Real, Spain
- Instituto de Investigación en Combustión y Contaminación Atmosférica (ICCA). Universidad de Castilla-La Mancha, Camino de Moledores s/n. 13071 Ciudad Real, Spain
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4
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Liu D, Giri BR, Farooq A. Cyclic Ketones as Future Fuels: Reactivity with OH Radicals. J Phys Chem A 2019; 123:4325-4332. [PMID: 31020843 DOI: 10.1021/acs.jpca.9b00691] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
For a sustainable energy future, research directions should orient toward exploring new fuels suitable for future advanced combustion engines to achieve better engine efficiency and significantly less harmful emissions. Cyclic ketones, among bio-derived fuels, are of significant interest to the combustion community for several reasons. As they possess high resistance to autoignition characteristics, they can potentially be attractive for fuel blending applications to increase engine efficiency and also to mitigate harmful emissions. Despite their importance, very few studies are rendered in understanding of the chemical kinetic behavior of cyclic ketones under engine-relevant conditions. In this work, we have conducted an experimental investigation for the reaction kinetics of OH radicals with cyclopentanone and cyclohexanone for the first time over a wide range of experimental conditions ( T = 900-1330 K and p ≈ 1.2 bar) in a shock tube. Reaction kinetics was followed by monitoring UV laser absorption of OH radicals near 306.7 nm. Our measured rate coefficients, with an overall uncertainty (2σ) of ±20%, can be expressed in Arrhenius form as (in units of cm3 molecule-1 s-1): k1(CPO+OH)=1.20×10-10exp(-2115KT) (902-1297 K); k2(CHO+OH)=2.11×10-10exp(-2268KT) (935-1331 K). Combining our measured data with the single low-temperature literature data, the following three-parameter Arrhenius expressions (in units of cm3 molecule-1 s-1) are obtained over a wider temperature range: k1(CPO + OH) = 1.07×10-13(T300K)3.20exp(1005.7KT) (298-1297 K); k2(CHO+OH)=3.12×10-13(T300K)2.78exp(897.5KT) (298-1331 K). Discrepancies between the theoretical and current experimental results are observed. Earlier theoretical works are found to overpredict our measured rate coefficients. Interestingly, these cyclic ketones exhibit similar reactivity behavior to that of their linear ketone counterparts over the experimental conditions of this work.
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Affiliation(s)
- Dapeng Liu
- Clean Combustion Research Center, Physical Sciences and Engineering Division , King Abdullah University of Science and Technology , Thuwal 23955-6900 , Saudi Arabia
| | - Binod Raj Giri
- Clean Combustion Research Center, Physical Sciences and Engineering Division , King Abdullah University of Science and Technology , Thuwal 23955-6900 , Saudi Arabia
| | - Aamir Farooq
- Clean Combustion Research Center, Physical Sciences and Engineering Division , King Abdullah University of Science and Technology , Thuwal 23955-6900 , Saudi Arabia
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5
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Sebbar N, Bozzelli JW, Trimis D, Bockhorn H. Thermochemistry and kinetics of the 2‐butanone‐4‐yl CH
3
C(=O)CH
2
CH
2
• + O
2
reaction system. INT J CHEM KINET 2019. [DOI: 10.1002/kin.21276] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- N. Sebbar
- KIT‐ Karlsruhe Institute of TechnologyEngler‐Bunte‐Institut Karlsruhe Germany
| | - J. W. Bozzelli
- Department of Chemical Engineering, Chemistry and Environmental ScienceNew Jersey Institute of Technology Newark, New Jersey
| | - D. Trimis
- KIT‐ Karlsruhe Institute of TechnologyEngler‐Bunte‐Institut Karlsruhe Germany
| | - H. Bockhorn
- KIT‐ Karlsruhe Institute of TechnologyEngler‐Bunte‐Institut Karlsruhe Germany
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6
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Zhang RM, Truhlar DG, Xu X. Kinetics of the Toluene Reaction with OH Radical. RESEARCH (WASHINGTON, D.C.) 2019; 2019:5373785. [PMID: 31549067 PMCID: PMC6750082 DOI: 10.34133/2019/5373785] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/08/2018] [Accepted: 02/10/2019] [Indexed: 11/16/2022]
Abstract
We calculated the kinetics of chemical activation reactions of toluene with hydroxyl radical in the temperature range from 213 K to 2500 K and the pressure range from 10 Torr to the high-pressure limit by using multistructural variational transition state theory with the small-curvature tunneling approximation (MS-CVT/SCT) and using the system-specific quantum Rice-Ramsperger-Kassel method. The reactions of OH with toluene are important elementary steps in both combustion and atmospheric chemistry, and thus it is valuable to understand the rate constants both in the high-pressure, high-temperature regime and in the low-pressure, low-temperature regime. Under the experimental pressure conditions, the theoretically calculated total reaction rate constants agree well with the limited experimental data, including the negative temperature dependence at low temperature. We find that the effect of multistructural anharmonicity on the partition functions usually increases with temperature, and it can change the calculated reaction rates by factors as small as 0.2 and as large as 4.2. We also find a large effect of anharmonicity on the zero-point energies of the transition states for the abstraction reactions. We report that abstraction of H from methyl should not be neglected in atmospheric chemistry, even though the low-temperature results are dominated by addition. We calculated the product distribution, which is usually not accessible to experiments, as a function of temperature and pressure.
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Affiliation(s)
- Rui Ming Zhang
- Center for Combustion Energy, Department of Energy and Power Engineering, and Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Tsinghua University, Beijing 100084, China
| | - Donald G. Truhlar
- Department of Chemistry, Chemical Theory Center, and Minnesota Supercomputing Institute, University of Minnesota, Minneapolis, MN 55455-0431, USA
| | - Xuefei Xu
- Center for Combustion Energy, Department of Energy and Power Engineering, and Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Tsinghua University, Beijing 100084, China
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7
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Pelucchi M, Cavallotti C, Faravelli T, Klippenstein SJ. H-Abstraction reactions by OH, HO 2, O, O 2 and benzyl radical addition to O 2 and their implications for kinetic modelling of toluene oxidation. Phys Chem Chem Phys 2018; 20:10607-10627. [PMID: 29387837 DOI: 10.1039/c7cp07779c] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Alkylated aromatics constitute a significant fraction of the components commonly found in commercial fuels. Toluene is typically considered as a reference fuel. Together with n-heptane and iso-octane, it allows for realistic emulations of the behavior of real fuels by the means of surrogate mixture formulations. Moreover, it is a key precursor for the formation of poly-aromatic hydrocarbons, which are of relevance to understanding soot growth and oxidation mechanisms. In this study the POLIMI kinetic model is first updated based on the literature and on recent kinetic modelling studies of toluene pyrolysis and oxidation. Then, important reaction pathways are investigated by means of high-level theoretical methods, thereby advancing the present knowledge on toluene oxidation. H-Abstraction reactions by OH, HO2, O and O2, and the reactivity on the multi well benzyl-oxygen (C6H5CH2 + O2) potential energy surface (PES) were investigated using electronic structure calculations, transition state theory in its conventional, variational, and variable reaction coordinate forms (VRC-TST), and master equation calculations. Exploration of the effect on POLIMI model performance of literature rate constants and of the present calculations provides valuable guidelines for implementation of the new rate parameters in existing toluene kinetic models.
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Affiliation(s)
- M Pelucchi
- Department of Chemistry, Materials and Chemical Engineering "G. Natta", Politecnico di Milano, Milan, Italy.
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8
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Frija LM, Kuznetsov ML, Rocha BG, Cabral L, Cristiano MLS, Kopylovich MN, Pombeiro AJ. Organocatalyzed oxidation of benzyl alcohols by a tetrazole-amino-saccharin: A combined experimental and theoretical (DFT) study. MOLECULAR CATALYSIS 2017. [DOI: 10.1016/j.mcat.2017.09.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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9
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Liu D, Khaled F, Giri BR, Assaf E, Fittschen C, Farooq A. H-Abstraction by OH from Large Branched Alkanes: Overall Rate Measurements and Site-Specific Tertiary Rate Calculations. J Phys Chem A 2017; 121:927-937. [PMID: 28071058 DOI: 10.1021/acs.jpca.6b10576] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Reaction rate coefficients for the reaction of hydroxyl (OH) radicals with nine large branched alkanes (i.e., 2-methyl-3-ethyl-pentane, 2,3-dimethyl-pentane, 2,2,3-trimethylbutane, 2,2,3-trimethyl-pentane, 2,3,4-trimethyl-pentane, 3-ethyl-pentane, 2,2,3,4-tetramethyl-pentane, 2,2-dimethyl-3-ethyl-pentane, and 2,4-dimethyl-3-ethyl-pentane) are measured at high temperatures (900-1300 K) using a shock tube and narrow-line-width OH absorption diagnostic in the UV region. In addition, room-temperature measurements of six out of these nine rate coefficients are performed in a photolysis cell using high repetition laser-induced fluorescence of OH radicals. Our experimental results are combined with previous literature measurements to obtain three-parameter Arrhenius expressions valid over a wide temperature range (300-1300 K). The rate coefficients are analyzed using the next-nearest-neighbor (N-N-N) methodology to derive nine tertiary (T003, T012, T013, T022, T023, T111, T112, T113, and T122) site-specific rate coefficients for the abstraction of H atoms by OH radicals from branched alkanes. Derived Arrhenius expressions, valid over 950-1300 K, are given as (the subscripts denote the number of carbon atoms connected to the next-nearest-neighbor carbon): T003 = 1.80 × 10-10 exp(-2971 K/T) cm3 molecule-1 s-1; T012 = 9.36 × 10-11 exp(-3024 K/T) cm3 molecule-1 s-1; T013 = 4.40 × 10-10 exp(-4162 K/T) cm3 molecule-1 s-1; T022 = 1.47 × 10-10 exp(-3587 K/T) cm3 molecule-1 s-1; T023 = 6.06 × 10-11 exp(-3010 K/T) cm3 molecule-1 s-1; T111 = 3.98 × 10-11 exp(-1617 K/T) cm3 molecule-1 s-1; T112 = 9.08 × 10-12 exp(-3661 K/T) cm3 molecule-1 s-1; T113 = 6.74 × 10-9 exp(-7547 K/T) cm3 molecule-1 s-1; T122 = 3.47 × 10-11 exp(-1802 K/T) cm3 molecule-1 s-1.
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Affiliation(s)
- Dapeng Liu
- Clean Combustion Research Center, King Abdullah University of Science and Technology , Thuwal 23955, Kingdom of Saudi Arabia
| | - Fethi Khaled
- Clean Combustion Research Center, King Abdullah University of Science and Technology , Thuwal 23955, Kingdom of Saudi Arabia
| | - Binod R Giri
- Clean Combustion Research Center, King Abdullah University of Science and Technology , Thuwal 23955, Kingdom of Saudi Arabia
| | - Emmanuel Assaf
- Université Lille , CNRS, UMR 8522 - PC2A - Physicochimie des Processus de Combustion et de l'Atmosphère, F-59000 Lille, France
| | - Christa Fittschen
- Université Lille , CNRS, UMR 8522 - PC2A - Physicochimie des Processus de Combustion et de l'Atmosphère, F-59000 Lille, France
| | - Aamir Farooq
- Clean Combustion Research Center, King Abdullah University of Science and Technology , Thuwal 23955, Kingdom of Saudi Arabia
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10
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Khaled F, Giri BR, Szőri M, Mai TVT, Huynh LK, Farooq A. A combined high-temperature experimental and theoretical kinetic study of the reaction of dimethyl carbonate with OH radicals. Phys Chem Chem Phys 2017; 19:7147-7157. [DOI: 10.1039/c6cp07318b] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The reaction kinetics of dimethyl carbonate (DMC) and OH radicals were investigated behind reflected shock waves over the temperature range of 872–1295 K and at pressures near 1.5 atm.
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Affiliation(s)
- Fethi Khaled
- Clean Combustion Research Center
- Division of Physical Sciences and Engineering
- King Abdullah University of Science and Technology
- Thuwal 23955-6900
- Saudi Arabia
| | - Binod Raj Giri
- Clean Combustion Research Center
- Division of Physical Sciences and Engineering
- King Abdullah University of Science and Technology
- Thuwal 23955-6900
- Saudi Arabia
| | - Milán Szőri
- Institute of Chemistry
- Faculty of Materials Science and Engineering
- University of Miskolc
- H-3515 Miskolc
- Hungary
| | - Tam V.-T. Mai
- Institute for Computational Science and Technology
- SBI Building
- Quang Trung Software City
- Ho Chi Minh City
- Vietnam
| | - Lam K. Huynh
- International University
- Vietnam National University – HCMC
- Quarter 6
- Ho Chi Minh City
- Vietnam
| | - Aamir Farooq
- Clean Combustion Research Center
- Division of Physical Sciences and Engineering
- King Abdullah University of Science and Technology
- Thuwal 23955-6900
- Saudi Arabia
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11
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Wang H, You X, Blitz MA, Pilling MJ, Robertson SH. Obtaining effective rate coefficients to describe the decomposition kinetics of the corannulene oxyradical at high temperatures. Phys Chem Chem Phys 2017; 19:11064-11074. [DOI: 10.1039/c7cp00639j] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
This work analyzes the effect of overlapping eigenvalues on the high-temperature kinetics of a large oxyradical based on master equation solutions.
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Affiliation(s)
- Hongmiao Wang
- Center for Combustion Energy
- Tsinghua University
- Beijing
- China
- Key Laboratory for Thermal Science and Power Engineering of Ministry of Education
| | - Xiaoqing You
- Center for Combustion Energy
- Tsinghua University
- Beijing
- China
- Key Laboratory for Thermal Science and Power Engineering of Ministry of Education
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12
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Khaled F, Giri BR, Szőri M, Viskolcz B, Farooq A. An experimental and theoretical study on the kinetic isotope effect of C2H6 and C2D6 reaction with OH. Chem Phys Lett 2015. [DOI: 10.1016/j.cplett.2015.10.057] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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13
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Wang S, Li S, Davidson DF, Hanson RK. Shock Tube Measurement of the High-Temperature Rate Constant for OH + CH3 → Products. J Phys Chem A 2015; 119:8799-805. [PMID: 26230910 DOI: 10.1021/acs.jpca.5b05725] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The reaction between hydroxyl (OH) and methyl radicals (CH3) is critical to hydrocarbon oxidation. Motivated by the sparseness of its high-temperature rate constant data and the large uncertainties in the existing literature values, the current study has remeasured the overall rate constant of the OH + CH3 reaction and extended the measurement temperature range to 1214-1933 K, using simultaneous laser absorption diagnostics for OH and CH3 radicals behind incident and reflected shock waves. tert-Butyl hydroperoxide and azomethane were used as pyrolytic sources for the OH and CH3 radicals, respectively. The current study bridged the temperature ranges of existing experimental data, and good agreement is seen between the current measurement and some previous experimental and theoretical high-temperature studies. A recommendation for the rate constant expression of the title reaction, based on the weighted average of the high-temperature data from selected studies, is given by k1 = 4.19 × 10(1)(T/K)(3.15) exp(5270 K/T) cm(3) mol(-1) s(-1) ±30%, which is valid over 1000-2500 K.
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Affiliation(s)
- Shengkai Wang
- High Temperature Gasdynamics Laboratory, Mechanical Engineering Department, Stanford University, Stanford, California 94305, United States
| | - Sijie Li
- High Temperature Gasdynamics Laboratory, Mechanical Engineering Department, Stanford University, Stanford, California 94305, United States
| | - David F Davidson
- High Temperature Gasdynamics Laboratory, Mechanical Engineering Department, Stanford University, Stanford, California 94305, United States
| | - Ronald K Hanson
- High Temperature Gasdynamics Laboratory, Mechanical Engineering Department, Stanford University, Stanford, California 94305, United States
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14
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Badra J, Khaled F, Giri BR, Farooq A. A shock tube study of the branching ratios of propene + OH reaction. Phys Chem Chem Phys 2015; 17:2421-31. [DOI: 10.1039/c4cp04322g] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Branching ratios of the propene + OH reaction are determined by measuring the rate coefficients of the reaction of OH with propene and five deuterated isotopes of propene.
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Affiliation(s)
- Jihad Badra
- Clean Combustion Research Center
- Division of Physical Sciences and Engineering
- King Abdullah University of Science and Technology (KAUST)
- Thuwal 23955
- Saudi Arabia
| | - Fethi Khaled
- Clean Combustion Research Center
- Division of Physical Sciences and Engineering
- King Abdullah University of Science and Technology (KAUST)
- Thuwal 23955
- Saudi Arabia
| | - Binod Raj Giri
- Clean Combustion Research Center
- Division of Physical Sciences and Engineering
- King Abdullah University of Science and Technology (KAUST)
- Thuwal 23955
- Saudi Arabia
| | - Aamir Farooq
- Clean Combustion Research Center
- Division of Physical Sciences and Engineering
- King Abdullah University of Science and Technology (KAUST)
- Thuwal 23955
- Saudi Arabia
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15
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Affiliation(s)
- Sijie Li
- Department of Mechanical Engineering; Stanford University; Stanford CA 94305
| | - David F. Davidson
- Department of Mechanical Engineering; Stanford University; Stanford CA 94305
| | - Ronald K. Hanson
- Department of Mechanical Engineering; Stanford University; Stanford CA 94305
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16
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Badra J, Elwardany AE, Farooq A. Reaction rate constants of H-abstraction by OH from large ketones: measurements and site-specific rate rules. Phys Chem Chem Phys 2014; 16:12183-93. [DOI: 10.1039/c4cp01253d] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Reaction rate constants of the reaction of four large ketones with hydroxyl (OH) are investigated behind reflected shock waves using OH laser absorption.
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Affiliation(s)
- Jihad Badra
- Clean Combustion Research Center
- Division of Physical Sciences and Engineering
- King Abdullah University of Science and Technology (KAUST)
- Thuwal 23955, Saudi Arabia
- Saudi Aramco Research and Development Center
| | - Ahmed E. Elwardany
- Clean Combustion Research Center
- Division of Physical Sciences and Engineering
- King Abdullah University of Science and Technology (KAUST)
- Thuwal 23955, Saudi Arabia
| | - Aamir Farooq
- Clean Combustion Research Center
- Division of Physical Sciences and Engineering
- King Abdullah University of Science and Technology (KAUST)
- Thuwal 23955, Saudi Arabia
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17
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Li S, Dames E, Davidson DF, Hanson RK. High-Temperature Measurements of the Reactions of OH with Ethylamine and Dimethylamine. J Phys Chem A 2013; 118:70-7. [DOI: 10.1021/jp411141w] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Sijie Li
- Department of Mechanical
Engineering, Stanford University, Stanford, California 94305, United States
| | - Enoch Dames
- Department of Mechanical
Engineering, Stanford University, Stanford, California 94305, United States
| | - David F. Davidson
- Department of Mechanical
Engineering, Stanford University, Stanford, California 94305, United States
| | - Ronald K. Hanson
- Department of Mechanical
Engineering, Stanford University, Stanford, California 94305, United States
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18
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Pang GA, Hanson RK, Golden DM, Bowman CT. Experimental determination of the high-temperature rate constant for the reaction of OH with sec-butanol. J Phys Chem A 2012; 116:9607-13. [PMID: 22946741 DOI: 10.1021/jp306977e] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The overall rate constant for the reaction of OH with sec-butanol [CH(3)CH(OH)CH(2)CH(3)] was determined from measurements of the near-first-order OH decay in shock-heated mixtures of tert-butylhydroperoxide (as a fast source of OH) with sec-butanol in excess. Three kinetic mechanisms from the literature describing sec-butanol combustion were used to examine the sensitivity of the rate constant determination to secondary kinetics. The overall rate constant determined can be described by the Arrhenius expression 6.97 × 10(-11) exp(-1550/T[K]) cm(3) molecule(-1) s(-1), valid over the temperature range of 888-1178 K. Uncertainty bounds of ±30% were found to adequately account for the uncertainty in secondary kinetics. To our knowledge, the current data represent the first efforts toward an experimentally determined rate constant for the overall reaction of OH with sec-butanol at combustion-relevant temperatures. A rate constant predicted using a structure-activity relationship from the literature was compared to the current data and previous rate constant measurements for the title reaction at atmospheric-relevant temperatures. The structure-activity relationship was found to be unable to correctly predict the measured rate constant at all temperatures where experimental data exist. We found that the three-parameter fit of 4.95 × 10(-20)T(2.66) exp(+1123/T[K]) cm(3) molecule(-1) s(-1) better describes the overall rate constant for the reaction of OH with sec-butanol from 263 to 1178 K.
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Affiliation(s)
- Genny A Pang
- Department of Mechanical Engineering, Stanford University, Stanford, California 94305, USA.
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19
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Lam KY, Davidson DF, Hanson RK. High-Temperature Measurements of the Reactions of OH with a Series of Ketones: Acetone, 2-Butanone, 3-Pentanone, and 2-Pentanone. J Phys Chem A 2012; 116:5549-59. [DOI: 10.1021/jp303853h] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Affiliation(s)
- King-Yiu Lam
- Department of Mechanical Engineering, Stanford University, Stanford, California
94305, United States
| | - David F. Davidson
- Department of Mechanical Engineering, Stanford University, Stanford, California
94305, United States
| | - Ronald K. Hanson
- Department of Mechanical Engineering, Stanford University, Stanford, California
94305, United States
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20
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Pang GA, Hanson RK, Golden DM, Bowman CT. High-Temperature Measurements of the Rate Constants for Reactions of OH with a Series of Large Normal Alkanes: n-Pentane, n-Heptane, and n-Nonane. ACTA ACUST UNITED AC 2011. [DOI: 10.1524/zpch.2011.0156] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Abstract
Rate constants for the overall reactions of OH with n-pentane, n-heptane, and n-nonane were measured in shock tube experiments behind reflected shock waves. Narrow-linewidth laser absorption by OH at 306.7 nm was used in pseudo first-order experiments with temperatures between 869 to 1364 K. tert-Butyl hydroperoxide (TBHP) was used as the OH precursor. Experiments were also performed to study the kinetics of the TBHP decomposition and resulting product chemistry, and an accurate mechanism describing OH precursor chemistry effects was developed to model OH concentration time-history in the n-alkane + OH experiments. The experimental results for the n-alkane + OH rate constant measurements can be expressed as rate constants in Arrhenius form as
k
n-pentane + OH = 2.10 × 10-10 exp(-2038/T[K]) (869–1364 K),
k
n-heptane + OH = 2.43 × 10-10 exp(-1804/T[K]) (869–1364 K),
k
n-nonane + OH = 3.17 × 10-10 exp(-1801/T[K]) (884–1352 K),
each in units of cm3 molecule-1 s-1. The present rate constants measured for OH with n-pentane and n-heptane show agreement within 20% with recent work by Sivaramakrishnan and Michael [J. Phys. Chem. A, 113 (2009) 5047]. The measurements of the rate constant for n-nonane + OH presented here represent the first in the literature to depict the temperature dependence of the rate constant above 800 K. The measurements of each n-alkane + OH rate constant studied were compared with two models in the literature used to estimate the rate constants of n-alkane + OH reactions. The Structure-Activity Relationship of Kwok and Atkinson [Atmos. Environ., 29 (1995) 1685] shows the best agreement with the current data for all three n-alkanes over the entire temperature range studied, demonstrating that this model is capable of predicting the overall rate constants for reactions of OH with n-pentane, n-heptane, and n-nonane for temperatures up to 1364 K.
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Affiliation(s)
| | - Ronald K. Hanson
- Stanford University, Mechanical Engineering Department, Stanford, CA 94305, U.S.A
| | - David M. Golden
- Stanford University, Department of Mechanical Engineering, Stanford CA 94305, U.S.A
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21
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Vasu SS, Huynh LK, Davidson DF, Hanson RK, Golden DM. Reactions of OH with Butene Isomers: Measurements of the Overall Rates and a Theoretical Study. J Phys Chem A 2011; 115:2549-56. [DOI: 10.1021/jp112294h] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Subith S. Vasu
- Mechanical Engineering Department, Stanford University, Stanford, California 94305-3032, United States
- Combustion Research Facility, MS 9055, Sandia National Laboratories, Livermore, California 94551-0969, United States
| | - Lam K. Huynh
- School of Biotechnology, International University VNUHCM, Vietnam
- Institute for Computational Science and Technology at Ho Chi Minh City, Vietnam
- Chemical Engineering Department, Colorado School of Mines, Golden, Colorado 80401, United States
| | - David F. Davidson
- Mechanical Engineering Department, Stanford University, Stanford, California 94305-3032, United States
| | - Ronald K. Hanson
- Mechanical Engineering Department, Stanford University, Stanford, California 94305-3032, United States
| | - David M. Golden
- Mechanical Engineering Department, Stanford University, Stanford, California 94305-3032, United States
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22
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Zhou CW, Simmie JM, Curran HJ. Ab initio and kinetic study of the reaction of ketones with ȮH for T = 500–2000 K. Part I: hydrogen-abstraction from H3CC(O)CH3–x(CH3)x, x = 0 ↦ 2. Phys Chem Chem Phys 2011; 13:11175-92. [DOI: 10.1039/c0cp02754e] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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23
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Sivaramakrishnan R, Su MC, Michael JV, Klippenstein SJ, Harding LB, Ruscic B. Rate Constants for the Thermal Decomposition of Ethanol and Its Bimolecular Reactions with OH and D: Reflected Shock Tube and Theoretical Studies. J Phys Chem A 2010; 114:9425-39. [DOI: 10.1021/jp104759d] [Citation(s) in RCA: 126] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- R. Sivaramakrishnan
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439
| | - M.-C. Su
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439
| | - J. V. Michael
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439
| | - S. J. Klippenstein
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439
| | - L. B. Harding
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439
| | - B. Ruscic
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439
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24
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Vasu SS, Zádor J, Davidson DF, Hanson RK, Golden DM, Miller JA. High-Temperature Measurements and a Theoretical Study of the Reaction of OH with 1,3-Butadiene. J Phys Chem A 2010; 114:8312-8. [DOI: 10.1021/jp104880u] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Subith S. Vasu
- Mechanical Engineering Department, Stanford University,
Stanford, California 94305-3032, and Combustion Research Facility,
MS 9055, Sandia National Laboratories, Livermore, California 94551-0969
| | - Judit Zádor
- Mechanical Engineering Department, Stanford University,
Stanford, California 94305-3032, and Combustion Research Facility,
MS 9055, Sandia National Laboratories, Livermore, California 94551-0969
| | - David F. Davidson
- Mechanical Engineering Department, Stanford University,
Stanford, California 94305-3032, and Combustion Research Facility,
MS 9055, Sandia National Laboratories, Livermore, California 94551-0969
| | - Ronald K. Hanson
- Mechanical Engineering Department, Stanford University,
Stanford, California 94305-3032, and Combustion Research Facility,
MS 9055, Sandia National Laboratories, Livermore, California 94551-0969
| | - David M. Golden
- Mechanical Engineering Department, Stanford University,
Stanford, California 94305-3032, and Combustion Research Facility,
MS 9055, Sandia National Laboratories, Livermore, California 94551-0969
| | - James A. Miller
- Mechanical Engineering Department, Stanford University,
Stanford, California 94305-3032, and Combustion Research Facility,
MS 9055, Sandia National Laboratories, Livermore, California 94551-0969
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25
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Hong Z, Vasu SS, Davidson DF, Hanson RK. Experimental Study of the Rate of OH + HO2 → H2O + O2 at High Temperatures Using the Reverse Reaction. J Phys Chem A 2010; 114:5520-5. [DOI: 10.1021/jp100739t] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Zekai Hong
- Department of Mechanical Engineering Stanford University, Stanford, California 94305, USA
| | - Subith S. Vasu
- Department of Mechanical Engineering Stanford University, Stanford, California 94305, USA
| | - David F. Davidson
- Department of Mechanical Engineering Stanford University, Stanford, California 94305, USA
| | - Ronald K. Hanson
- Department of Mechanical Engineering Stanford University, Stanford, California 94305, USA
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26
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da Silva G, Cole JA, Bozzelli JW. Thermal Decomposition of the Benzyl Radical to Fulvenallene (C7H6) + H. J Phys Chem A 2009; 113:6111-20. [DOI: 10.1021/jp901933x] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Gabriel da Silva
- Department of Chemical and Biomolecular Engineering, The University of Melbourne, Victoria 3010, Australia, and Department of Chemistry and Environmental Science, New Jersey Institute of Technology, Newark, New Jersey 07102
| | - John A. Cole
- Department of Chemical and Biomolecular Engineering, The University of Melbourne, Victoria 3010, Australia, and Department of Chemistry and Environmental Science, New Jersey Institute of Technology, Newark, New Jersey 07102
| | - Joseph W. Bozzelli
- Department of Chemical and Biomolecular Engineering, The University of Melbourne, Victoria 3010, Australia, and Department of Chemistry and Environmental Science, New Jersey Institute of Technology, Newark, New Jersey 07102
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27
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Vasudevan V, Cook RD, Hanson RK, Bowman CT, Golden DM. High-temperature shock tube study of the reactions CH3 + OH → products and CH3OH + Ar → products. INT J CHEM KINET 2008. [DOI: 10.1002/kin.20334] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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28
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Li H, Owens ZC, Davidson DF, Hanson RK. A simple reactive gasdynamic model for the computation of gas temperature and species concentrations behind reflected shock waves. INT J CHEM KINET 2008. [DOI: 10.1002/kin.20305] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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29
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Srinivasan NK, Su MC, Michael JV, Klippenstein SJ, Harding LB. Reflected Shock Tube and Theoretical Studies of High-Temperature Rate Constants for OH + CF3H ⇆ CF3 + H2O and CF3 + OH → Products. J Phys Chem A 2007; 111:6822-31. [PMID: 17503789 DOI: 10.1021/jp0706228] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The reflected shock tube technique with multipass absorption spectrometric detection of OH radicals at 308 nm, using either 36 or 60 optical passes corresponding to total path lengths of 3.25 or 5.25 m, respectively, has been used to study the bimolecular reactions, OH+CF3H-->CF3+H2O (1) and CF3+H2O-->OH+CF3H (-1), between 995 and 1663 K. During the course of the study, estimates of rate constants for CF3+OH-->products (2) could also be determined. Experiments on reaction -1 were transformed through equilibrium constants to k1, giving the Arrhenius expression k1=(9.7+/-2.1)x10(-12) exp(-4398+/-275K/T) cm3 molecule(-1) s(-1). Over the temperature range, 1318-1663 K, the results for reaction 2 were constant at k2=(1.5+/-0.4)x10(-11) cm3 molecule(-1) s(-1). Reactions 1 and -1 were also studied with variational transition state theory (VTST) employing QCISD(T) properties for the transition state. These a priori VTST predictions were in good agreement with the present experimental results but were too low at the lower temperatures of earlier experiments, suggesting that either the barrier height was overestimated by about 1.3 kcal/mol or that the effect of tunneling was greatly underestimated. The present experimental results have been combined with the most accurate earlier studies to derive an evaluation over the extended temperature range of 252-1663 K. The three parameter expression k1=2.08x10(-17) T1.5513 exp(-1848 K/T) cm3 molecule(-1) s(-1) describes the rate behavior over this temperature range. Alternatively, the expression k1,th=1.78x10(-23) T3.406 exp(-837 K/T) cm3 molecule(-1) s(-1) obtained from empirically adjusted VTST calculations over the 250-2250 K range agrees with the experimental evaluation to within a factor of 1.6. Reaction 2 was also studied with direct CASPT2 variable reaction coordinate transition state theory. The resulting predictions for the capture rate are found to be in good agreement with the mean of the experimental results and can be represented by the expression k2,th=2.42x10(-11) T-0.0650 exp(134 K/T) cm3 molecule(-1) s(-1) over the 200-2500 K temperature range. The products of this reaction are predicted to be CF2O+HF.
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Affiliation(s)
- N K Srinivasan
- Chemistry Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
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30
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Srinivasan NK, Su MC, Michael JV. High-temperature rate constants for CH3OH + Kr --> products, OH + CH3OH --> products, OH + (CH3)(2)CO --> CH2COCH3 + H2O, and OH + CH3 --> CH) + H2O. J Phys Chem A 2007; 111:3951-8. [PMID: 17388365 DOI: 10.1021/jp0673516] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The reflected shock tube technique with multipass absorption spectrometric detection of OH radicals at 308 nm (corresponding to a total path length of approximately 4.9 m) has been used to study the dissociation of methanol between 1591 and 2865 K. Rate constants for two product channels [CH3OH + Kr --> CH3 + OH + Kr (1) and CH3OH + Kr --> 1CH2 + H2O + Kr (2)] were determined. During the course of the study, it was necessary to determine several other rate constants that contributed to the profile fits. These include OH + CH3OH --> products, OH + (CH3)2CO --> CH2COCH3 + H2O, and OH + CH3 --> 1,3CH2 + H2O. The derived expressions, in units of cm(3) molecule(-1) s(-1), are k(1) = 9.33 x 10(-9) exp(-30857 K/T) for 1591-2287 K, k(2) = 3.27 x 10(-10) exp(-25946 K/T) for 1734-2287 K, kOH+CH3OH = 2.96 x 10-16T1.4434 exp(-57 K/T) for 210-1710 K, k(OH+(CH3)(2)CO) = (7.3 +/- 0.7) x 10(-12) for 1178-1299 K and k(OH+CH3) = (1.3 +/- 0.2) x 10(-11) for 1000-1200 K. With these values along with other well-established rate constants, a mechanism was used to obtain profile fits that agreed with experiment to within <+/-10%. The values obtained for reactions 1 and 2 are compared with earlier determinations and also with new theoretical calculations that are presented in the preceding article in this issue. These new calculations are in good agreement with the present data for both (1) and (2) and also for OH + CH3 --> products.
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Affiliation(s)
- N K Srinivasan
- Chemistry Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
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31
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Khamaganov VG, Bui VX, Carl SA, Peeters J. Absolute rate coefficient of the OH + CH(3)C(O)OH reaction at T = 287-802 K. The two faces of pre-reactive H-bonding. J Phys Chem A 2007; 110:12852-9. [PMID: 17125300 DOI: 10.1021/jp064922l] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The rate constants for the reaction OH + CH3C(O)OH --> products (1) were determined over the temperature range 287-802 K at 50 and 100 Torr of Ar or N2 bath gas using pulsed laser photolysis generation of OH by CH3C(O)OH photolysis at 193 nm coupled with OH detection by pulsed laser-induced fluorescence. The rate coefficient displays a complex temperature dependence with a sharp minimum at 530 K, indicating the competition between a reaction proceeding through a pre-reactive H-bonded complex to form CH3C(O)O + H2O, expected to prevail at low temperatures, and a direct methyl-H abstraction channel leading to CH2C(O)OH + H2O, which should dominate at high temperatures. The temperature dependence of the rate constant can be described adequately by k1(287-802 K) = 2.9 x 10(-9) exp{-6030 K/T} + 1.50 x 10(-13) exp{515 K/T} cm3 molecule(-1)(s-1), with a value of (8.5 +/- 0.9) x 10-13 cm3 molecule(-1)(s-1) at 298 K. The steep increase in rate constant in the range 550-800 K, which is reported for the first time, implies that direct abstraction of a methyl-H becomes the dominant pathway at temperatures greater than 550 K. However, the data indicates that up to about 800 K direct methyl-H abstraction remains adversely affected by the long-range H-bonding attraction between the approaching OH radical and the carboxyl -C(O)OH functionality.
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Affiliation(s)
- Victor G Khamaganov
- Department of Chemistry, University of Leuven, Celestijnenlaan 200 F, 3001 Leuven, Belgium
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