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Crisci L, Barone V. Reconciling Accuracy and Feasibility for Barrierless Reaction Steps by the PCS/DDCI/MC-PDFT Protocol: Methane and Ethylene Dissociations as Case Studies. J Chem Theory Comput 2024; 20:8539-8548. [PMID: 39287503 DOI: 10.1021/acs.jctc.4c00911] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/19/2024]
Abstract
Several enhancements have been introduced into state-of-the-art computational protocols for the treatment of barrierless reaction steps in the framework of variable reaction coordinate variational transition state theory. The first step is the synergistic integration of the Iterative Difference Dedicated Configuration Interaction (I-DDCI) and Pisa Composite Scheme, which defines a reduced cost, yet very accurate, computational workflow. This approach provides a near black box tool for obtaining 1D reference potentials. Then, a general strategy has been devised for tuning the level of theory used in Monte Carlo (MC) sampling, employing Multiconfiguration Pair Density Functional Theory (MC-PDFT) with dynamically adjusted Hartree-Fock exchange. Concurrently, partial geometry optimizations during the MC simulations account for the coupling between the reaction coordinates and conserved modes. The protocol closely approaches full size consistency and yields highly accurate results, with several test computations suggesting rapid convergence of the I-DDCI correction with the basis set dimensions. The capabilities of the new platform are illustrated by two case studies (the hydrogen dissociation from CH4 and C2H4), which highlight its flexibility in handling different carbon hybridizations (sp3 and sp2). The remarkable accuracy of the computed rate constants confirms the robustness of the proposed method. Together with their intrinsic interest, these results pave the way for systematic investigations of complex gas-phase reactions through a reliable, user-friendly tool accessible to specialists and nonspecialists alike.
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Affiliation(s)
- Luigi Crisci
- Scuola Normale Superiore di Pisa, Piazza dei Cavalieri 7, I-56126 Pisa, Italy
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2
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Angiolari F, Huppert S, Spezia R. Quantum versus classical unimolecular fragmentation rate constants and activation energies at finite temperature from direct dynamics simulations. Phys Chem Chem Phys 2022; 24:29357-29370. [PMID: 36448557 DOI: 10.1039/d2cp03809a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
In the present work, we investigate how nuclear quantum effects modify the temperature dependent rate constants and, consequently, the activation energies in unimolecular reactions. In the reactions under study, nuclear quantum effects mainly stem from the presence of a large zero point energy. Thus, we investigate the behavior of methods compatible with direct dynamics simulations, the quantum thermal bath (QTB) and ring polymer molecular dynamics (RPMD). To this end, we first compare them with quantum reaction theory for a model Morse potential before extending this comparison to molecular models. Our results show that, in particular in the temperature range comparable with or lower than the zero point energy of the system, the RPMD method is able to correctly capture nuclear quantum effects on rate constants and activation energies. On the other hand, although the QTB provides a good description of equilibrium properties including zero-point energy effects, it largely overestimates the rate constants. The origin of the different behaviours is in the different distance distributions provided by the two methods and in particular how they differently describe the tails of such distributions. The comparison with transition state theory shows that RPMD can be used to study fragmentation of complex systems for which it may be difficult to determine the multiple reaction pathways and associated transition states.
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Affiliation(s)
- Federica Angiolari
- Sorbonne Université, Laboratoire de Chimie Théorique, UMR 7616 CNRS, 4 Place Jussieu, 75005 Paris, France.
| | - Simon Huppert
- Sorbonne Université, Institut de Nanosciences de Paris, UMR 7588 CNRS, 4 Place Jussieu, 75005 Paris, France
| | - Riccardo Spezia
- Sorbonne Université, Laboratoire de Chimie Théorique, UMR 7616 CNRS, 4 Place Jussieu, 75005 Paris, France.
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3
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Cao F, Shi G, Song J, Tian P, Li Z. Kinetics of the Reactions of Methyl Radical with Hydrogen, Methyl and Ethyl Peroxides. ChemistrySelect 2021. [DOI: 10.1002/slct.202100193] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Fei Cao
- State Key Laboratory of Engines Tianjin University Tianjin 300350 P.R. China
| | - Gai Shi
- State Key Laboratory of Engines Tianjin University Tianjin 300350 P.R. China
| | - Jinou Song
- State Key Laboratory of Engines Tianjin University Tianjin 300350 P.R. China
| | - Pengzhen Tian
- College of Mathematics and Information Science Hebei University Baoding Hebei 071002 P.R. China
| | - Zhijun Li
- State Key Laboratory of Engines Tianjin University Tianjin 300350 P.R. China
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4
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Chow R, Mok DKW. A theoretical study of the addition of CH 2OO to hydroxymethyl hydroperoxide and its implications on SO 3 formation in the atmosphere. Phys Chem Chem Phys 2020; 22:14130-14141. [PMID: 32542295 DOI: 10.1039/d0cp00961j] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The reaction of hydroxymethyl hydroperoxide (HMHP, HOCH2OOH) with the simplest Criegee intermediate, CH2OO, has been examined using quantum chemical methods with transition state theory. Geometry optimization and IRC calculations were performed using the M06-2X, MN15-L, and B2PLYP-D3 functionals in conjunction with the aug-cc-pVTZ basis set. Single point energy calculations using QCISD(T) and BD(T) with the same basis set have been performed to determine the energy of reactants, reactive complexes, transition states, and products. Rate coefficients have been obtained using variational transition state theory. The addition of CH2OO on the three different oxygen atoms in HMHP has been considered and the ether oxide forming channel, CH2OO + HOCH2OOH → HOCH2O(O)CH2OOH (channel 2), is the most favorable. The best computed standard enthalpy of reaction (ΔH) and zero-point corrected barrier height are -20.02 and -6.33 kcal mol-1, respectively. The reaction barrier is negative and our results suggest that both the inner and outer transition states contribute to the corresponding overall reactive flux in the tropospheric temperature range (220 K to 320 K). A two-transition state model has been used to obtain reliable rate coefficients at the high-pressure limit. The pressure-dependent rate coefficient calculations using the SS-QRRK theory have shown that this channel is pressure-dependent. Moreover, our investigation has shown that the ether oxide formed may rapidly react with SO2 at 298 K to form SO3, which can, in turn, react with water to form atmospheric H2SO4. A similar calculation has been conducted for the reaction of HMHP with OH, suggesting that the titled reaction may be a significant sink of HMHP. Therefore, the reaction between CH2OO and HOCH2OOH could be an indirect source for generating atmospheric H2SO4, which is crucial to the formation of clouds, and it might relieve global warming.
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Affiliation(s)
- Ronald Chow
- Department of Applied Biology and Chemical Technology, Hong Kong Polytechnic University, Hung Hom, Hong Kong.
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5
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Jasper AW. Microcanonical Rate Constants for Unimolecular Reactions in the Low-Pressure Limit. J Phys Chem A 2020; 124:1205-1226. [DOI: 10.1021/acs.jpca.9b10693] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Ahren W. Jasper
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
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6
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Spezia R, Dammak H. On the Use of Quantum Thermal Bath in Unimolecular Fragmentation Simulation. J Phys Chem A 2019; 123:8542-8551. [DOI: 10.1021/acs.jpca.9b06795] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Riccardo Spezia
- Laboratoire de Chimie Théorique, Sorbonne Université and CNRS, F-75005 Paris, France
| | - Hichem Dammak
- Laboratoire Structures, Propriétés et Modélisation des Solides, CentraleSupélec, CNRS, Université Paris-Saclay, F-91190 Gif-sur-Yvette, France
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7
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Hao J, Schwach P, Fang G, Guo X, Zhang H, Shen H, Huang X, Eggart D, Pan X, Bao X. Enhanced Methane Conversion to Olefins and Aromatics by H-Donor Molecules under Nonoxidative Condition. ACS Catal 2019. [DOI: 10.1021/acscatal.9b01771] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Jianqi Hao
- State Key Laboratory of Catalysis, National Laboratory for Clean Energy, 2011-Collaborative Innovation Center of Chemistry for Energy Materials, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Zhongshan Road 457, Dalian 116023, China
- University of Chinese Academy of Sciences, Yuquan Road 19A, Shijingshan District, Beijing 100049, China
| | - Pierre Schwach
- State Key Laboratory of Catalysis, National Laboratory for Clean Energy, 2011-Collaborative Innovation Center of Chemistry for Energy Materials, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Zhongshan Road 457, Dalian 116023, China
| | - Guangzong Fang
- State Key Laboratory of Catalysis, National Laboratory for Clean Energy, 2011-Collaborative Innovation Center of Chemistry for Energy Materials, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Zhongshan Road 457, Dalian 116023, China
| | - Xiaoguang Guo
- State Key Laboratory of Catalysis, National Laboratory for Clean Energy, 2011-Collaborative Innovation Center of Chemistry for Energy Materials, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Zhongshan Road 457, Dalian 116023, China
| | - Hailei Zhang
- Key Laboratory of Nuclear Physics and Ion-beam Application, Institute of Modern Physics, Fudan University, Shanghai 200433, China
| | - Hao Shen
- Key Laboratory of Nuclear Physics and Ion-beam Application, Institute of Modern Physics, Fudan University, Shanghai 200433, China
| | - Xin Huang
- State Key Laboratory of Catalysis, National Laboratory for Clean Energy, 2011-Collaborative Innovation Center of Chemistry for Energy Materials, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Zhongshan Road 457, Dalian 116023, China
| | - Daniel Eggart
- Institute for Chemical Technology and Polymer Chemistry (ITCP), Karlsruhe Institute of Technology, Kaiserstraße 12, Karlsruhe 76131, Germany
| | - Xiulian Pan
- State Key Laboratory of Catalysis, National Laboratory for Clean Energy, 2011-Collaborative Innovation Center of Chemistry for Energy Materials, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Zhongshan Road 457, Dalian 116023, China
| | - Xinhe Bao
- State Key Laboratory of Catalysis, National Laboratory for Clean Energy, 2011-Collaborative Innovation Center of Chemistry for Energy Materials, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Zhongshan Road 457, Dalian 116023, China
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8
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Sela P, Sakai Y, Choi HS, Herzler J, Fikri M, Schulz C, Peukert S. High-Temperature Unimolecular Decomposition of Diethyl Ether: Shock-Tube and Theory Studies. J Phys Chem A 2019; 123:6813-6827. [PMID: 31329437 DOI: 10.1021/acs.jpca.9b04186] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The unimolecular decomposition of diethyl ether (DEE; C2H5OC2H5) is considered to be initiated via a molecular elimination and a C-O and a C-C bond fission step: C2H5OC2H5 → C2H4 + C2H5OH (1), C2H5OC2H5 → C2H5 + C2H5O (2), and C2H5OC2H5 → CH3 + C2H5OCH2 (3). In this work, two shock-tube facilities were used to investigate these reactions via (a) time-resolved H-atom concentration measurements by H-ARAS (atomic resonance absorption spectrometry), (b) time-resolved DEE-concentration measurements by high repetition-rate time-of-flight mass spectrometry (HRR-TOF-MS), and (c) product-composition measurements via gas chromatography/MS (GC/MS) after quenching the test gas. The experiments were conducted at temperatures ranging from 1054 to 1505 K and at pressures between 1.2 and 2.5 bar. Initial DEE mole fractions between 0.4 and 9300 ppm were used to perform the kinetics experiments by H-ARAS (0.4 ppm), GC/MS (200-500 ppm), and HRR-TOF-MS (7850-9300 ppm). The rate constants, ktotal (ktotal = k1 + k2 + k3) derived from the GC/MS and HRR-TOF-MS experiments agree well with each other and can be described by the Arrhenius expression, ktotal(1054-1467 K; 1.3-2.5 bar) = 1012.81±0.22 exp(-240.27 ± 5.11 kJ mol-1/RT) s-1. From the H-ARAS experiments, overall rate constants for the bond fission channels, k2+3 = k2 + k3 have been extracted. The k2+3 data can be well described by the Arrhenius equation, k2+3(1299-1505 K; 1.3-2.5 bar) = 1014.43±0.33 exp(-283.27 ± 8.78 kJ mol-1/RT) s-1. A master-equation analysis was performed using CCSD(T)/aug-cc-pvtz//B3LYP/aug-cc-pvtz and CASPT2/aug-cc-pvtz//B3LYP/aug-cc-pvtz molecular properties and energies for the three primary thermal decomposition processes in DEE. The derived experimental data is very well reproduced by the simulations with the mechanism of this work. With regard to the branching ratios between bond fissions and elimination channels, uncertainties remain.
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Affiliation(s)
- Paul Sela
- IVG, Institute for Combustion and Gas Dynamics-Reactive Fluids and CENIDE, Center for Nanointegration Duisburg-Essen , University of Duisburg-Essen , 47048 Duisburg , Germany
| | - Yasuyuki Sakai
- Graduate School of Engineering , University of Fukui , Fukui 910-8507 , Japan
| | - Hang Seok Choi
- IVG, Institute for Combustion and Gas Dynamics-Reactive Fluids and CENIDE, Center for Nanointegration Duisburg-Essen , University of Duisburg-Essen , 47048 Duisburg , Germany
| | - Jürgen Herzler
- IVG, Institute for Combustion and Gas Dynamics-Reactive Fluids and CENIDE, Center for Nanointegration Duisburg-Essen , University of Duisburg-Essen , 47048 Duisburg , Germany
| | - Mustapha Fikri
- IVG, Institute for Combustion and Gas Dynamics-Reactive Fluids and CENIDE, Center for Nanointegration Duisburg-Essen , University of Duisburg-Essen , 47048 Duisburg , Germany
| | - Christof Schulz
- IVG, Institute for Combustion and Gas Dynamics-Reactive Fluids and CENIDE, Center for Nanointegration Duisburg-Essen , University of Duisburg-Essen , 47048 Duisburg , Germany
| | - Sebastian Peukert
- IVG, Institute for Combustion and Gas Dynamics-Reactive Fluids and CENIDE, Center for Nanointegration Duisburg-Essen , University of Duisburg-Essen , 47048 Duisburg , Germany
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9
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Jasper AW, Davis MJ. Parameterization Strategies for Intermolecular Potentials for Predicting Trajectory-Based Collision Parameters. J Phys Chem A 2019; 123:3464-3480. [DOI: 10.1021/acs.jpca.9b01918] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ahren W. Jasper
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Michael J. Davis
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
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10
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Classical trajectory studies of collisional energy transfer. ACTA ACUST UNITED AC 2019. [DOI: 10.1016/b978-0-444-64207-3.00003-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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11
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Peukert S, Sela P, Nativel D, Herzler J, Fikri M, Schulz C. Direct Measurement of High-Temperature Rate Constants of the Thermal Decomposition of Dimethoxymethane, a Shock Tube and Modeling Study. J Phys Chem A 2018; 122:7559-7571. [DOI: 10.1021/acs.jpca.8b06558] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Sebastian Peukert
- IVG, Institute for Combustion and Gas Dynamics−Reactive Fluids and CENIDE, Center for Nanointegration Duisburg−Essen, University of Duisburg−Essen, 47048 Duisburg, Germany
| | - Paul Sela
- IVG, Institute for Combustion and Gas Dynamics−Reactive Fluids and CENIDE, Center for Nanointegration Duisburg−Essen, University of Duisburg−Essen, 47048 Duisburg, Germany
| | - Damien Nativel
- IVG, Institute for Combustion and Gas Dynamics−Reactive Fluids and CENIDE, Center for Nanointegration Duisburg−Essen, University of Duisburg−Essen, 47048 Duisburg, Germany
| | - Jürgen Herzler
- IVG, Institute for Combustion and Gas Dynamics−Reactive Fluids and CENIDE, Center for Nanointegration Duisburg−Essen, University of Duisburg−Essen, 47048 Duisburg, Germany
| | - Mustapha Fikri
- IVG, Institute for Combustion and Gas Dynamics−Reactive Fluids and CENIDE, Center for Nanointegration Duisburg−Essen, University of Duisburg−Essen, 47048 Duisburg, Germany
| | - Christof Schulz
- IVG, Institute for Combustion and Gas Dynamics−Reactive Fluids and CENIDE, Center for Nanointegration Duisburg−Essen, University of Duisburg−Essen, 47048 Duisburg, Germany
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12
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Peukert S, Herzler J, Fikri M, Schulz C. High-Temperature Rate Constants for H + Tetramethylsilane and H + Silane and Implications about Structure-Activity Relationships for Silanes. INT J CHEM KINET 2017. [DOI: 10.1002/kin.21140] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- S. Peukert
- IVG; Institute for Combustion and Gas Dynamics-Reactive Fluids, and CENIDE; Center for Nanointegration Duisburg-Essen; University of Duisburg-Essen; 47048 Duisburg Germany
| | - J. Herzler
- IVG; Institute for Combustion and Gas Dynamics-Reactive Fluids, and CENIDE; Center for Nanointegration Duisburg-Essen; University of Duisburg-Essen; 47048 Duisburg Germany
| | - M. Fikri
- IVG; Institute for Combustion and Gas Dynamics-Reactive Fluids, and CENIDE; Center for Nanointegration Duisburg-Essen; University of Duisburg-Essen; 47048 Duisburg Germany
| | - C. Schulz
- IVG; Institute for Combustion and Gas Dynamics-Reactive Fluids, and CENIDE; Center for Nanointegration Duisburg-Essen; University of Duisburg-Essen; 47048 Duisburg Germany
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13
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Cobos CJ, Hintzer K, Sölter L, Tellbach E, Thaler A, Troe J. Shock Wave and Theoretical Modeling Study of the Dissociation of CH 2F 2. I. Primary Processes. J Phys Chem A 2017; 121:7813-7819. [PMID: 28948790 DOI: 10.1021/acs.jpca.7b05854] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The unimolecular dissociation of CH2F2 leading to CF2 + H2, CHF + HF, or CHF2 + H is investigated by quantum-chemical calculations and unimolecular rate theory. Modeling of the rate constants is accompanied by shock wave experiments over the range of 1400-1800 K, monitoring the formation of CF2. It is shown that the energetically most favorable dissociation channel leading to CF2 + H2 has a higher threshold energy than the energetically less favorable one leading to CHF + HF. Falloff curves of the dissociations are modeled. Under the conditions of the described experiments, the primary dissociation CH2F2 → CHF + HF is followed by the reaction CHF + HF → CF2 + H2. The experimental value of the rate constant for the latter reaction indicates that it does not proceed by an addition-elimination process involving CH2F2* intermediates, as assumed before.
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Affiliation(s)
- C J Cobos
- INIFTA, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, CONICET , Casilla de Correo 16, Sucursal 4, 1900 La Plata, Argentina
| | - K Hintzer
- Dyneon GmbH , Gendorf, D-84508 Burgkirchen, Germany
| | - L Sölter
- Institut für Physikalische Chemie, Universität Göttingen , Tammannstrasse 6, D-37077 Göttingen, Germany
| | - E Tellbach
- Institut für Physikalische Chemie, Universität Göttingen , Tammannstrasse 6, D-37077 Göttingen, Germany
| | - A Thaler
- Dyneon GmbH , Gendorf, D-84508 Burgkirchen, Germany
| | - J Troe
- Institut für Physikalische Chemie, Universität Göttingen , Tammannstrasse 6, D-37077 Göttingen, Germany.,Max-Planck-Institut für Biophysikalische Chemie , Am Fassberg 11, D-37077 Göttingen, Germany
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14
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Schwach P, Pan X, Bao X. Direct Conversion of Methane to Value-Added Chemicals over Heterogeneous Catalysts: Challenges and Prospects. Chem Rev 2017; 117:8497-8520. [DOI: 10.1021/acs.chemrev.6b00715] [Citation(s) in RCA: 656] [Impact Index Per Article: 93.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Pierre Schwach
- State
Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, P.R. China
| | - Xiulian Pan
- State
Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, P.R. China
| | - Xinhe Bao
- State
Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, P.R. China
- Chemistry
Department, Fudan University, Shanghai 200433, P.R. China
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15
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Knight G, Sölter L, Tellbach E, Troe J. Shock wave and modeling study of the reaction CF4 (+M) ⇔ CF3 + F (+M). Phys Chem Chem Phys 2016; 18:17592-6. [PMID: 27307206 DOI: 10.1039/c6cp03010f] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The thermal decomposition of CF4 (+Ar) → CF3 + F (+Ar) was studied in shock waves over the temperature range 2000-3000 K varying the bath gas concentration [Ar] between 4 × 10(-6) and 9 × 10(-5) mol cm(-3). It is shown that the reaction corresponds to the intermediate range of the falloff curve. By combination with room temperature data for the reverse reaction CF3 + F (+He) → CF4 (+He) and applying unimolecular rate theory, falloff curves over the temperature range 300-6000 K are modeled. A comparison with the reaction system CH4 (+M) ⇔ CH3 + H (+M) is made.
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Affiliation(s)
- Gary Knight
- Edwards Innovation Centre, Clevedon, BS21 6TH, UK
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16
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Wang S, Davidson DF, Hanson RK. Improved Shock Tube Measurement of the CH4 + Ar = CH3 + H + Ar Rate Constant using UV Cavity-Enhanced Absorption Spectroscopy of CH3. J Phys Chem A 2016; 120:5427-34. [DOI: 10.1021/acs.jpca.6b02572] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Shengkai Wang
- High Temperature Gasdynamics
Laboratory, Mechanical Engineering, Stanford University, California 94305, United States
| | - David F. Davidson
- High Temperature Gasdynamics
Laboratory, Mechanical Engineering, Stanford University, California 94305, United States
| | - Ronald K. Hanson
- High Temperature Gasdynamics
Laboratory, Mechanical Engineering, Stanford University, California 94305, United States
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17
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Qu C, Conte R, Houston PL, Bowman JM. “Plug and play” full-dimensional ab initio potential energy and dipole moment surfaces and anharmonic vibrational analysis for CH4–H2O. Phys Chem Chem Phys 2015; 17:8172-81. [DOI: 10.1039/c4cp05913a] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The first full-dimensional potential energy surface of CH4–H2O dimer is presented, and vibrational analysis of this dimer is performed.
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Affiliation(s)
- Chen Qu
- Department of Chemistry and Cherry L. Emerson Centrer for Scientific Computations
- Emory University
- Atlanta
- USA
| | - Riccardo Conte
- Department of Chemistry and Cherry L. Emerson Centrer for Scientific Computations
- Emory University
- Atlanta
- USA
| | - Paul L. Houston
- School of Chemistry and Biochemistry
- Georgia Institute of Technology
- Atlanta
- USA
- Department of Chemistry and Chemical Biology
| | - Joel M. Bowman
- Department of Chemistry and Cherry L. Emerson Centrer for Scientific Computations
- Emory University
- Atlanta
- USA
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18
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Baptista L, da Silveira EF. A theoretical study of three gas-phase reactions involving the production or loss of methane cations. Phys Chem Chem Phys 2014; 16:21867-75. [PMID: 25200833 DOI: 10.1039/c4cp02607a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Hydrocarbon ions are important species in flames, spectroscopy and the interstellar medium. Their importance is reflected in the extensive body of literature on the structure and reactivity of carbocations. However, the geometry, electronic structure and reactivity of carbocations are difficult to assess. This study aims to contribute to the current knowledge of this subject by presenting a quantum mechanics description of methane cation dissociation using multiconfigurational methods. The geometric and electronic parameters of the minimum structure were determined for three main reaction paths: the dissociation CH4(+)→ CH2(+) + H2 and the dissociation-recombination processes CH4(+)↔ CH3(+) + H. The electronic and energetic effects of these reactions were analyzed, and it was found that each reaction path has a strong dependence on the methodology used as well as a strong multiconfigurational character during dissociation. The first doublet excited states are inner-shell excited states and may correspond to the ions that are expected to be formed after electron detachment. The rate coefficient for each reaction path was determined using variational transition state theory and RRKM/master equation calculations. The major dissociation paths, with their rate coefficients at the high-pressure limit, are CH4(+)(X(~)(2)B1) → CH3(+)(A(2)A1') + H((2)S) (k∞(T) = 1.42 × 10(+14) s(-1) exp(-37.12/RT)) and CH4(+)(X(~)(2)B1) → CH2(+)(A(2)A1) + H2((2)Σg(+)) (k∞(T) = 9.18 × 10(+14) s(-1) exp(-55.77/RT)). Our findings help to explain the abundance of ions formed from CH4 in the interstellar medium and to build models of chemical evolution.
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Affiliation(s)
- Leonardo Baptista
- Universidade do Estado do Rio de Janeiro, Faculdade de Tecnologia, Departamento de Química e Ambiental, Rodovia Presidente Dutra Km 298, Resende, RJ, Brazil.
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19
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Affiliation(s)
- Jürgen Troe
- Institut für Physikalische Chemie, Universität Göttingen , and Max-Planck-Institut für Biophysikalische Chemie, Göttingen, Germany
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Jasper AW, Miller JA, Klippenstein SJ. Collision Efficiency of Water in the Unimolecular Reaction CH4 (+H2O) ⇆ CH3 + H (+H2O): One-Dimensional and Two-Dimensional Solutions of the Low-Pressure-Limit Master Equation. J Phys Chem A 2013; 117:12243-55. [DOI: 10.1021/jp409086w] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ahren W. Jasper
- Combustion
Research Facility, Sandia National Laboratories, P.O. Box 969, Livermore, California 94551-0969, United States
| | - James A. Miller
- Chemical
Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Stephen J. Klippenstein
- Chemical
Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
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Peukert SL, Labbe NJ, Sivaramakrishnan R, Michael JV. Direct measurements of rate constants for the reactions of CH3 radicals with C2H6, C2H4, and C2H2 at high temperatures. J Phys Chem A 2013; 117:10228-38. [PMID: 23968575 DOI: 10.1021/jp4073153] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The shock tube technique has been used to study the reactions CH3 + C2H6 → C2H4 + CH4 + H (1), CH3 + C2H4 → Products + H (2), and CH3 + C2H2 → Products + H (3). Biacetyl, (CH3CO)2, was used as a clean high temperature thermal source for CH3-radicals for all the three reactions studied in this work. For reaction 1, the experiments span a T-range of 1153 K ≤ T ≤ 1297 K, at P ~ 0.4 bar. The experiments on reaction 2 cover a T-range of 1176 K ≤ T ≤ 1366 K, at P ~ 1.0 bar, and those on reaction 3 a T-range of 1127 K ≤ T ≤ 1346 K, at P ~ 1.0 bar. Reflected shock tube experiments performed on reactions 1-3, monitored the formation of H-atoms with H-atom Atomic Resonance Absorption Spectrometric (ARAS). Fits to the H-atom temporal profiles using an assembled kinetics model were used to make determinations for k1, k2, and k3. In the case of C2H6, the measurements of [H]-atoms were used to derive direct high-temperature rate constants, k1, that can be represented by the Arrhenius equation k1(T) = 5.41 × 10(-12) exp(-6043 K/T) cm(3) molecules(-1) s(-1) (1153 K ≤ T ≤ 1297 K) for the only bimolecular process that occurs, H-atom abstraction. TST calculations based on ab initio properties calculated at the CCSD(T)/CBS//M06-2X/cc-pVTZ level of theory show excellent agreement, within ±20%, of the measured rate constants. For the reaction of CH3 with C2H4, the present rate constant results, k2', refer to the sum of rate constants, k(2b) + k(2c), from two competing processes, addition-elimination, and the direct abstraction CH3 + C2H4 → C3H6 + H (2b) and CH3 + C2H4 → C2H2 + H + CH4 (2c). Experimental rate constants for k2' can be represented by the Arrhenius equation k2'(T) = 2.18 × 10(-10) exp(-11830 K/T) cm(3) molecules(-1) s(-1) (1176 K ≤ T ≤ 1366 K). The present results are in excellent agreement with recent theoretical predictions. The present study provides the only direct measurement for the high-temperature rate constants for these channels. Lastly, measurements of H-atoms from the reaction of CH3 with C2H2 provided direct unambiguous determinations of the rate constant for the dominant process under the present experimental conditions, the addition-elimination, CH3 + C2H2 → p-C3H4 + H (3b). Experimental rate constants for k(3b) can be represented by the Arrhenius equation k(3b)(T) = 5.16 × 10(-13) exp(-3852 K/T) cm(3) molecules(-1) s(-1) (1127 K ≤ T ≤ 1346 K). The present determinations for k(3b) represent the only direct measurements for this reaction and are also in good agreement with recent theoretical predictions. The present experimental k(3b) values were also used to derive rate constants, k(-3b), for the more extensively studied back-process, the reaction of H-atoms with propyne. The best fit Arrhenius equation, combining the presently derived k(-3b) values with a recent experimental determination for k(-3b), can be represented by k(-3b)(T) = 3.87 × 10(-11) exp(-1313 K/T) cm(3) molecules(-1) s(-1) (870 K ≤ T ≤ 1346 K). The present studies represent a novel implementation of the sensitive H-ARAS technique to measure rate constants for poorly characterized and difficult to isolate "slow" CH3-radical reactions with stable C2 hydrocarbons.
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Affiliation(s)
- S L Peukert
- Chemical Sciences and Engineering Division, Argonne National Laboratory , Argonne, Illinois 60439, United States
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Peukert SL, Michael JV. High-Temperature Shock Tube and Modeling Studies on the Reactions of Methanol with D-Atoms and CH3-Radicals. J Phys Chem A 2013; 117:10186-95. [DOI: 10.1021/jp4059005] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- S. L. Peukert
- Chemical
Sciences and Engineering
Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - J. V. Michael
- Chemical
Sciences and Engineering
Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
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Affiliation(s)
- David M. Golden
- Department of Mechanical Engineering; Stanford University; Stanford; CA; 94305
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