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Demireva M, Au K, Hansen N, Sheps L. Time-resolved quantification of key species and mechanistic insights in low-temperature tetrahydrofuran oxidation. Phys Chem Chem Phys 2024; 26:10357-10368. [PMID: 38502092 DOI: 10.1039/d3cp06227a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/20/2024]
Abstract
We investigate the kinetics and report the time-resolved concentrations of key chemical species in the oxidation of tetrahydrofuran (THF) at 7500 torr and 450-675 K. Experiments are carried out using high-pressure multiplexed photoionization mass spectrometry (MPIMS) combined with tunable vacuum ultraviolet radiation from the Berkely Lab Advanced Light Source. Intermediates and products are quantified using reference photoionization (PI) cross sections, when available, and constrained by a global carbon balance tracking approach at all experimental temperatures simultaneously for the species without reference cross sections. From carbon balancing, we determine time-resolved concentrations for the ROO˙ and ˙OOQOOH radical intermediates, butanedial, and the combined concentration of ketohydroperoxide (KHP) and unsaturated hydroperoxide (UHP) products stemming from the ˙QOOH + O2 reaction. Furthermore, we quantify a product that we tentatively assign as fumaraldehyde, which arises from UHP decomposition via H2O or ˙OH + H loss. The experimentally derived species concentrations are compared with model predictions using the most recent literature THF oxidation mechanism of Fenard et al., (Combust. Flame, 2018, 191, 252-269). Our results indicate that the literature mechanism significantly overestimates THF consumption and the UHP + KHP concentration at our conditions. The model predictions are sensitive to the rate coefficient for the ROO˙ isomerization to ˙QOOH, which is the gateway for radical chain propagating and branching pathways. Comparisons with our recent results for cyclopentane (Demireva et al., Combust. Flame, 2023, 257, 112506) provide insights into the effect of the ether group on reactivity and highlight the need to determine accurate rate coefficients of ROO˙ isomerization and subsequent reactions.
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Affiliation(s)
- Maria Demireva
- Combustion Research Facility, Sandia National Laboratories, Livermore, California 94551, USA.
| | - Kendrew Au
- Combustion Research Facility, Sandia National Laboratories, Livermore, California 94551, USA.
| | - Nils Hansen
- Combustion Research Facility, Sandia National Laboratories, Livermore, California 94551, USA.
| | - Leonid Sheps
- Combustion Research Facility, Sandia National Laboratories, Livermore, California 94551, USA.
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Couch DE, Mulvihill CR, Sivaramakrishnan R, Au K, Taatjes CA, Sheps L. Quantification of Key Peroxy and Hydroperoxide Intermediates in the Low-Temperature Oxidation of Dimethyl Ether. J Phys Chem A 2022; 126:9497-9509. [DOI: 10.1021/acs.jpca.2c06959] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- David E. Couch
- Combustion Research Facility, Sandia National Laboratories, Livermore, California94551, United States
| | - Clayton R. Mulvihill
- Chemical Sciences and Engineering, Argonne National Laboratory, Lemont, Illinois60439, United States
| | - Raghu Sivaramakrishnan
- Chemical Sciences and Engineering, Argonne National Laboratory, Lemont, Illinois60439, United States
| | - Kendrew Au
- Combustion Research Facility, Sandia National Laboratories, Livermore, California94551, United States
| | - Craig A. Taatjes
- Combustion Research Facility, Sandia National Laboratories, Livermore, California94551, United States
| | - Leonid Sheps
- Combustion Research Facility, Sandia National Laboratories, Livermore, California94551, United States
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Rösch D, Almeida R, Sztáray B, Osborn DL. High-Resolution Double Velocity Map Imaging Photoelectron Photoion Coincidence Spectrometer for Gas-Phase Reaction Kinetics. J Phys Chem A 2022; 126:1761-1774. [PMID: 35258948 DOI: 10.1021/acs.jpca.1c10293] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
We present a new photoelectron photoion coincidence (PEPICO) spectrometer that combines high mass resolution of cations with independently adjustable velocity map imaging of both cations and electrons. We photoionize atoms and molecules using fixed-frequency vacuum ultraviolet radiation. Mass-resolved photoelectron spectra associated with each cation's mass-to-charge ratio can be obtained by inversion of the photoelectron image. The mass-resolved photoelectron spectra enable kinetic time-resolved probing of chemical reactions with isomeric resolution using fixed-frequency radiation sources amenable to small laboratory settings. The instrument accommodates a variety of sample delivery sources to explore a broad range of physical chemistry. To demonstrate the time-resolved capabilities of the instrument, we study the 193 nm photodissociation of SO2 via the C̃(1B2) ← X̃(1A1) transition. In addition to the well-documented O(3Pj) + SO(3Σ-) channel, we observe direct evidence for a small yield of S(3Pj) + O2(3Σg-) as a primary photodissociation product channel, which may impact sulfur mass-independent fractionation chemistry.
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Affiliation(s)
- Daniel Rösch
- Combustion Research Facility, Sandia National Laboratories, Mail Stop 9055, Livermore, California 94551-0969, United States
| | - Raybel Almeida
- Combustion Research Facility, Sandia National Laboratories, Mail Stop 9055, Livermore, California 94551-0969, United States
| | - Bálint Sztáray
- Department of Chemistry, University of the Pacific, Stockton, California 95211, United States
| | - David L Osborn
- Combustion Research Facility, Sandia National Laboratories, Mail Stop 9055, Livermore, California 94551-0969, United States.,Department of Chemical Engineering, University of California, Davis, Davis, California 95616, United States
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Sheps L, Dewyer AL, Demireva M, Zádor J. Quantitative Detection of Products and Radical Intermediates in Low-Temperature Oxidation of Cyclopentane. J Phys Chem A 2021; 125:4467-4479. [PMID: 34006098 DOI: 10.1021/acs.jpca.1c02001] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We present a combined experimental and theoretical investigation of the autoignition chemistry of a prototypical cyclic hydrocarbon, cyclopentane. Experiments using a high-pressure photolysis reactor coupled to time-resolved synchrotron VUV photoionization mass spectrometry directly probe the short-lived radical intermediates and products in cyclopentane oxidation reactions. We detect key peroxy radical intermediates ROO and OOQOOH, as well as several hydroperoxides, formed by second O2 addition. Automated quantum chemical calculations map out the R + O2 + O2 reaction channels and demonstrate that the detected intermediates belong to the dominant radical chain-branching pathway: ROO (+ O2) → γ-QOOH + O2 → γ-OOQOOH → products. ROO, OOQOOH, and hydroperoxide products of second-O2 addition undergo extensive dissociative ionization, making their experimental assignment challenging. We use photoionization dynamics calculations to aid in their characterization and report the absolute photoionization spectra of isomerically pure ROO and γ-OOQOOH. A global statistical fit of the observed kinetics enables reliable quantification of the time-resolved concentrations of these elusive, yet critical species, paving the way for detailed comparisons with theoretical predictions from master-equation-based models.
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Affiliation(s)
- Leonid Sheps
- Combustion Research Facility, Mail Stop 9055, Sandia National Laboratories, Livermore, California 94551-0969, United States
| | - Amanda L Dewyer
- Combustion Research Facility, Mail Stop 9055, Sandia National Laboratories, Livermore, California 94551-0969, United States
| | - Maria Demireva
- Combustion Research Facility, Mail Stop 9055, Sandia National Laboratories, Livermore, California 94551-0969, United States
| | - Judit Zádor
- Combustion Research Facility, Mail Stop 9055, Sandia National Laboratories, Livermore, California 94551-0969, United States
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Demireva M, Au K, Sheps L. Direct time-resolved detection and quantification of key reactive intermediates in diethyl ether oxidation at T = 450-600 K. Phys Chem Chem Phys 2020; 22:24649-24661. [PMID: 33099590 DOI: 10.1039/d0cp03861j] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
High-pressure multiplexed photoionization mass spectrometry (MPIMS) with tunable vacuum ultraviolet (VUV) ionization radiation from the Lawrence Berkeley Labs Advanced Light Source is used to investigate the oxidation of diethyl ether (DEE). Kinetics and photoionization (PI) spectra are simultaneously measured for the species formed. Several stable products from DEE oxidation are identified and quantified using reference PI cross-sections. In addition, we directly detect and quantify three key chemical intermediates: peroxy (ROO˙), hydroperoxyalkyl peroxy (˙OOQOOH), and ketohydroperoxide (HOOP[double bond, length as m-dash]O, KHP). These intermediates undergo dissociative ionization (DI) into smaller fragments, making their identification by mass spectrometry challenging. With the aid of quantum chemical calculations, we identify the DI channels of these key chemical species and quantify their time-resolved concentrations from the overall carbon atom balance at T = 450 K and P = 7500 torr. This allows the determination of the absolute PI cross-sections of ROO˙, ˙OOQOOH, and KHP into each DI channel directly from experiment. The PI cross-sections in turn enable the quantification of ROO˙, ˙OOQOOH, and KHP from DEE oxidation over a range of experimental conditions that reveal the effects of pressure, O2 concentration, and temperature on the competition among radical decomposition and second O2 addition pathways.
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Affiliation(s)
- Maria Demireva
- Combustion Research Facility, Sandia National Laboratories, Livermore, California 94551, USA.
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McCoy AB. Virtual Issue on New Tools and Methods in Physical Chemistry Research. J Phys Chem A 2020; 124:4323-4324. [PMID: 32493016 DOI: 10.1021/acs.jpca.0c04262] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Anne B McCoy
- Department of Chemistry, University of Washington, Seattle, Washington 98195, United States
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