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Asatryan R, Hudzik J, Swihart M. Intramolecular Catalytic Hydrogen Atom Transfer (CHAT). J Phys Chem A 2024; 128:2169-2190. [PMID: 38451855 DOI: 10.1021/acs.jpca.3c06794] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/09/2024]
Abstract
Intramolecular catalysis (IntraCat) is the acceleration of a process at one site of a molecule catalyzed by a functional group in the same molecule; an external agent such as a solvent typically facilitates it. Here, we report a general first-principles-based IntraCat mechanism, which strictly occurs within a single molecule with no coreagent being involved─we call it intramolecular catalytic transfer of hydrogen atoms (CHAT). A reactive part of a molecule (chat catalyst moiety or chat agent, represented by -OOH, -COOH, -SH, -CH2OH, -HPO4, or another bifunctional H-donor/acceptor group) catalyzes an interconversion process, such as keto-enol or amino-imino tautomerization, and cyclization in the same molecule, while being regenerated in the process. It can thus be regarded as an intramolecular version of the intermolecular H atom transfer processes mediated by an external molecular catalyst, e.g., dihydrogen, water, or a carboxylic acid. Earlier, we proposed a general mechanistic systematization of intermolecular processes, illustrated in the simplest case of the H2-mediated reactions classified as dihydrogen catalysis [Asatryan, R.; et al. Catal. Rev.: Sci. Eng., 2014, 56, 403-475]. Following this systematization, the CHAT catalysis belongs to the category of relay transfer of H atoms, albeit in an intramolecular manner. A broader class of intramolecular processes includes all types of H-transfer reactions stimulated by an H-migration, which we call self-catalyzed H atom transfer (SC-HAT). The CHAT mechanism comprises a subset of SC-HAT in which the catalytic moiety is regenerated (i.e., acts as a true catalyst and not a reagent). We provide several characteristic examples of CHAT mechanism based on detailed analysis of the corresponding potential energy surfaces. All such cases showed a dramatically reduced activation barrier relative to the corresponding uncatalyzed H-transfer reactions. For example, we show that CHAT can facilitate long-range H-migration in larger molecules and can occur multiple times in one molecule with multiple interconverting groups. It also facilitates amino-imino tautomerization of unsaturated GABA-analogues and peptides, as well as intramolecular cyclization processes to form heterocycles, e.g., oxygenated rings. CHAT pathways may also explain the pH-dependent increase of mutarotation rate of glucose-6-phosphate demonstrated in pioneering experiments that introduced the classical IntraCat concept. In addition, we identify a ground electronic state CHAT pathway as an alternative to the UV-promoted long-range molecular crane keto-enol conversion with a remarkably low activation energy. To initially assess the possible impact of the new keto-enol conversion pathway on combustion of n-alkanes, we present a detailed kinetic analysis of isomerization and decomposition of pentane-2,4-ketohydroperoxide (2,4-KHP). The results are compared with key alternative reactions, including direct dissociation and Korcek channels (for which a new alkyl group migration channel is also identified), revealing the competitiveness of the CHAT pathway across a range of conditions. Taken together, this work provides insight into a general class of reaction pathways that has not previously being systematically considered and that may occur in a broad range of contexts from combustion to atmospheric chemistry to biochemistry.
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Affiliation(s)
- Rubik Asatryan
- Department of Chemical and Biological Engineering, and Center for Hybrid Rocket Exascale Simulation Technology (CHREST), University at Buffalo, The State University of New York, Buffalo, New York 14260, United States
| | - Jason Hudzik
- Department of Chemical and Biological Engineering, and Center for Hybrid Rocket Exascale Simulation Technology (CHREST), University at Buffalo, The State University of New York, Buffalo, New York 14260, United States
| | - Mark Swihart
- Department of Chemical and Biological Engineering, and Center for Hybrid Rocket Exascale Simulation Technology (CHREST), University at Buffalo, The State University of New York, Buffalo, New York 14260, United States
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2
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Kjærgaard ER, Møller KH, Kjaergaard HG. Atmospheric Oxidation of Hydroperoxy Amides. J Phys Chem A 2023; 127:9311-9321. [PMID: 37877667 DOI: 10.1021/acs.jpca.3c04509] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2023]
Abstract
Recently, hydroperoxy amides were identified as major products of OH-initiated autoxidation of tertiary amines in the atmosphere. The formation mechanism is analogous to that found for ethers and sulfides but substantially faster. However, the atmospheric fate of the hydroperoxy amides remains unknown. Using high-level theoretical methods, we study the most likely OH-initiated oxidation pathways of the hydroperoxy and dihydroperoxy amides derived from trimethylamine autoxidation. Overall, we find that the OH-initiated oxidation of the hydroperoxy amides predominantly leads to the formation of imides under NO-dominated conditions and more highly oxidized hydroperoxy amides under HO2-dominated conditions. Unimolecular reactions are found to be surprisingly slow, likely due to the restricting, planar structure of the amide moiety.
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Affiliation(s)
- Eva R Kjærgaard
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark
| | - Kristian H Møller
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark
| | - Henrik G Kjaergaard
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark
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3
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Stewart M, Ohno PE, McKinney K, Martin ST. Prediction of the Response of a Photoionization Detector to a Complex Gaseous Mixture of Volatile Organic Compounds Produced by α-Pinene Oxidation. ACS Earth Space Chem 2023; 7:1956-1970. [PMID: 37876663 PMCID: PMC10592314 DOI: 10.1021/acsearthspacechem.3c00054] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Revised: 09/19/2023] [Accepted: 09/19/2023] [Indexed: 10/26/2023]
Abstract
Photoionization detectors (PIDs) are lightweight and respond in real time to the concentrations of volatile organic compounds (VOCs), making them suitable for environmental measurements on many platforms. However, the nonselective sensing mechanism of PIDs challenges data interpretation, particularly when exposed to the complex VOC mixtures prevalent in the Earth's atmosphere. Herein, two approaches to this challenge are investigated. In the first, quantum-chemistry calculations are used to estimate photoionization cross sections and ionization potentials of individual species. In the second, machine learning models are trained on these calculated values, as well as empirical PID response factors, and then used for prediction. For both approaches, the resulting information for individual species is used to model the overall PID response to a complex VOC mixture. In complement, laboratory experiments in the Harvard Environmental Chamber are carried out to measure the PID response to the complex molecular mixture produced by α-pinene oxidation under various conditions. The observations show that the measured PID response is 15% to 30% smaller than the PID response modeled by quantum-chemistry calculations of the photoionization cross section for the photo-oxidation experiments and 15% to 20% for the ozonolysis experiments. By comparison, the measured PID response is captured within a 95% confidence interval by the use of machine learning to model the PID response based on the empirical response factor in all experiments. Taken together, the results of this study demonstrate the application of machine learning to augment the performance of a nonselective chemical sensor. The approach can be generalized to other reactive species, oxidants, and reaction mechanisms, thus enhancing the utility and interpretability of PID measurements for studying atmospheric VOCs.
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Affiliation(s)
- Matthew
P. Stewart
- School
of Engineering and Applied Sciences, Harvard
University, Cambridge, Massachusetts 02138, United States
| | - Paul E. Ohno
- School
of Engineering and Applied Sciences, Harvard
University, Cambridge, Massachusetts 02138, United States
| | - Karena McKinney
- Department
of Chemistry, Colby College, Waterville, Maine 04901, United States
| | - Scot T. Martin
- School
of Engineering and Applied Sciences, Harvard
University, Cambridge, Massachusetts 02138, United States
- Department
of Earth and Planetary Sciences, Harvard
University, Cambridge, Massachusetts 02138, United States
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4
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Doner AC, Dewey NS, Rotavera B. Unimolecular Reactions of 2-Methyloxetanyl and 2-Methyloxetanylperoxy Radicals. J Phys Chem A 2023; 127:6816-6829. [PMID: 37535464 PMCID: PMC10440797 DOI: 10.1021/acs.jpca.3c03918] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2023] [Revised: 07/17/2023] [Indexed: 08/05/2023]
Abstract
Alkyl-substituted cyclic ethers are intermediates formed in abundance during the low-temperature oxidation of hydrocarbons and biofuels via a chain-propagating step with ȮH. Subsequent reactions of cyclic ether radicals involve a competition between ring opening and reaction with O2, the latter of which enables pathways mediated by hydroperoxy-substituted carbon-centered radicals (Q̇OOH). Due to the resultant implications of competing unimolecular and bimolecular reactions on overall populations of ȮH, detailed insight into the chemical kinetics of cyclic ethers remains critical to high-fidelity numerical modeling of combustion. Cl-initiated oxidation experiments were conducted on 2-methyloxetane (an intermediate of n-butane oxidation) using multiplexed photoionization mass spectrometry (MPIMS), in tandem with calculations of stationary point energies on potential energy surfaces for unimolecular reactions of 2-methyloxetanyl and 2-methyloxetanylperoxy isomers. The potential energy surfaces were computed using the KinBot algorithm with stationary points calculated at the CCSD(T)-F12/cc-pVDZ-F12 level of theory. The experiments were conducted at 6 Torr and two temperatures (650 K and 800 K) under pseudo-first-order conditions to facilitate Ṙ + O2 reactions. Photoionization spectra were measured from 8.5 eV to 11.0 eV in 50-meV steps, and relative yields were quantified for species consistent with Ṙ → products and Q̇OOH → products. Species detected in the MPIMS experiments are linked to specific radicals of 2-methyloxetane. Species from Ṙ → products include methyl, ethene, formaldehyde, propene, ketene, 1,3-butadiene, and acrolein. Ion signals consistent with products from alkyl radical oxidation were detected, including for Q̇OOH-mediated species, which are also low-lying channels on their respective potential energy surfaces. In addition to species common to alkyl oxidation pathways, ring-opening reactions of Q̇OOH radicals derived from 2-methyloxetane produced ketohydroperoxide species (performic acid and 2-hydroperoxyacetaldehyde), which may impart additional chain-branching potential, and dicarbonyl species (3-oxobutanal and 2-methylpropanedial), which often serve as proxies for modeling reaction rates of ketohydroperoxides. The experimental and computational results underscore that reactions of cyclic ethers are inherently more complex than currently prescribed in chemical kinetic models utilized for combustion.
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Affiliation(s)
- Anna C. Doner
- University
of Georgia, Department of Chemistry, Athens, Georgia 30602, United States
| | - Nicholas S. Dewey
- University
of Georgia, Department of Chemistry, Athens, Georgia 30602, United States
| | - Brandon Rotavera
- University
of Georgia, Department of Chemistry, Athens, Georgia 30602, United States
- University
of Georgia, College of Engineering, Athens, Georgia 30602, United States
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5
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Stewart M, Martin ST. Machine Learning for Ionization Potentials and Photoionization Cross Sections of Volatile Organic Compounds. ACS Earth Space Chem 2023; 7:863-875. [PMID: 37152449 PMCID: PMC10152554 DOI: 10.1021/acsearthspacechem.3c00009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Revised: 03/16/2023] [Accepted: 03/17/2023] [Indexed: 05/09/2023]
Abstract
Molecular ionization potentials (IP) and photoionization cross sections (σ) can affect the sensitivity of photoionization detectors (PIDs) and other sensors for gaseous species. This study employs several methods of machine learning (ML) to predict IP and σ values at 10.6 eV (117 nm) for a dataset of 1251 gaseous organic species. The explicitness of the treatment of the species electronic structure progressively increases among the methods. The study compares the ML predictions of the IP and σ values to those obtained by quantum chemical calculations. The ML predictions are comparable in performance to those of the quantum calculations when evaluated against measurements. Pretraining further reduces the mean absolute errors (ε) compared to the measurements. The graph-based attentive fingerprint model was most accurate, for which εIP = 0.23 ± 0.01 eV and εσ = 2.8 ± 0.2 Mb compared to measurements and computed cross sections, respectively. The ML predictions for IP correlate well with both the measured IPs (R 2 = 0.88) and with IPs computed at the level of M06-2X/aug-cc-pVTZ (R 2 = 0.82). The ML predictions for σ correlated reasonably well with computed cross sections (R 2 = 0.66). The developed ML methods for IP and σ values, representing the properties of a generalizable set of volatile organic compounds (VOCs) relevant to industrial applications and atmospheric chemistry, can be used to quantitatively describe the species-dependent sensitivity of chemical sensors that use ionizing radiation as part of the sensing mechanism, such as photoionization detectors.
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Affiliation(s)
- Matthew
P. Stewart
- School
of Engineering and Applied Sciences, Harvard
University, Cambridge, Massachusetts 02138, United States
| | - Scot T. Martin
- School
of Engineering and Applied Sciences, Harvard
University, Cambridge, Massachusetts 02138, United States
- Department
of Earth and Planetary Sciences, Harvard
University, Cambridge, Massachusetts 02138, United States
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6
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Abstract
Combustion is a reactive oxidation process that releases energy bound in chemical compounds used as fuels─energy that is needed for power generation, transportation, heating, and industrial purposes. Because of greenhouse gas and local pollutant emissions associated with fossil fuels, combustion science and applications are challenged to abandon conventional pathways and to adapt toward the demand of future carbon neutrality. For the design of efficient, low-emission processes, understanding the details of the relevant chemical transformations is essential. Comprehensive knowledge gained from decades of fossil-fuel combustion research includes general principles for establishing and validating reaction mechanisms and process models, relying on both theory and experiments with a suite of analytic monitoring and sensing techniques. Such knowledge can be advantageously applied and extended to configure, analyze, and control new systems using different, nonfossil, potentially zero-carbon fuels. Understanding the impact of combustion and its links with chemistry needs some background. The introduction therefore combines information on exemplary cultural and technological achievements using combustion and on nature and effects of combustion emissions. Subsequently, the methodology of combustion chemistry research is described. A major part is devoted to fuels, followed by a discussion of selected combustion applications, illustrating the chemical information needed for the future.
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Liu B, Dong S, Debleza J, Chen W, Xu Q, Wang H, Bourgalais J, Herbinet O, Curran HJ, Battin-Leclerc F, Wang Z. Experimental and Updated Kinetic Modeling Study of Neopentane Low Temperature Oxidation. J Phys Chem A 2023; 127:2113-2122. [PMID: 36815799 DOI: 10.1021/acs.jpca.2c03795] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/24/2023]
Abstract
Neopentane is an ideal fuel model to study low-temperature oxidation chemistry. The significant discrepancies between experimental data and simulations using the existing neopentane models indicate that an updated study of neopentane oxidation is needed. In this work, neopentane oxidation experiments are carried out using two jet-stirred reactors (JSRs) at 1 atm, at a residence time of 3 s, and at three different equivalence ratios of 0.5, 0.9, and 1.62. Two different analytical methods (synchrotron vacuum ultraviolet photoionization mass spectrometry and gas chromatography) were used to investigate the species distributions. Numerous oxidation intermediates were detected and quantified, including acetone, 3,3-dimethyloxetane, methacrolein, isobutene, 2-methylpropanal, isobutyric acid, and peroxides, which are valuable for validating the kinetic model describing neopentane oxidation. In the model development, the pressure dependencies of the rate constants for the reaction classes Q̇OOH + O2 and Q̇OOH decompositions are considered. This addition improves the prediction of the low-temperature oxidation reactivity of neopentane. Another focus of model development is to improve the prediction of carboxylic acids formed during the low-temperature oxidation of neopentane. The detection and identification of isobutyric acid indicates the existence of the Korcek mechanism during neopentane oxidation. Regarding the formation of acetic acid, the reaction channels are considered to be initiated from the reactions of ȮH radical addition to acetaldehyde/acetone. This updated kinetic model is validated extensively against the experimental data in this work and various experimental data available in the literature, including ignition delay times (IDTs) from both shock tubes (STs) and rapid compression machines (RCMs) and JSR speciation data at high temperatures.
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Affiliation(s)
- Bingzhi Liu
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230029, PR China
| | - Shijun Dong
- Combustion Chemistry Centre, School of Biological and Chemical Sciences, Ryan Institute, MaREI, University of Galway, Galway H91 TK33, Ireland.,School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan, Hubei 430074, PR China
| | - Janney Debleza
- LRGP, Université de Lorraine and CNRS, F-54000 Nancy, France
| | - Weiye Chen
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230029, PR China
| | - Qiang Xu
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230029, PR China
| | - Hong Wang
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230029, PR China
| | | | | | - Henry J Curran
- Combustion Chemistry Centre, School of Biological and Chemical Sciences, Ryan Institute, MaREI, University of Galway, Galway H91 TK33, Ireland
| | | | - Zhandong Wang
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230029, PR China.,State Key Laboratory of Fire Science, University of Science and Technology of China, Hefei, Anhui 230026, PR China
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8
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Hellmuth M, Chen B, Bariki C, Cai L, Cameron F, Wildenberg A, Huang C, Faller S, Ren Y, Beeckmann J, Leonhard K, Heufer KA, Hansen N, Pitsch H. A Comparative Study on the Combustion Chemistry of Two Bio-hybrid Fuels: 1,3-Dioxane and 1,3-Dioxolane. J Phys Chem A 2023; 127:286-299. [PMID: 36580040 DOI: 10.1021/acs.jpca.2c06576] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Bio-hybrid fuels are a promising solution to accomplish a carbon-neutral and low-emission future for the transportation sector. Two potential candidates are the heterocyclic acetals 1,3-dioxane (C4H8O2) and 1,3-dioxolane (C3H6O2), which can be produced from the combination of biobased feedstocks, carbon dioxide, and renewable electricity. In this work, comprehensive experimental and numerical investigations of 1,3-dioxane and 1,3-dioxolane were performed to support their application in internal combustion engines. Ignition delay times and laminar flame speeds were measured to reveal the combustion chemistry on the macroscale, while speciation measurements in a jet-stirred reactor and ethylene-based counterflow diffusion flames provided insights into combustion chemistry and pollutant formation on the microscale. Comparing the experimental and numerical data using either available or proposed kinetic models revealed that the combustion chemistry and pollutant formation differ substantially between 1,3-dioxane and 1,3-dioxolane, although their molecular structures are similar. For example, 1,3-dioxane showed higher reactivity in the low-temperature regime (500-800 K), while 1,3-dioxolane addition to ethylene increased polycyclic aromatic hydrocarbons and soot formation in high-temperature (>800 K) counterflow diffusion flames. Reaction pathway analyses were performed to examine and explain the differences between these two bio-hybrid fuels, which originate from the chemical bond dissociation energies in their molecular structures.
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Affiliation(s)
- Maximilian Hellmuth
- Institute for Combustion Technology, RWTH Aachen University, 52056Aachen, Germany
| | - Bingjie Chen
- Institute for Combustion Technology, RWTH Aachen University, 52056Aachen, Germany
| | - Chaimae Bariki
- Institute for Combustion Technology, RWTH Aachen University, 52056Aachen, Germany
| | - Liming Cai
- School for Automotive Studies, Tongji University, 201804Shanghai, China
| | - Florence Cameron
- Institute for Combustion Technology, RWTH Aachen University, 52056Aachen, Germany
| | - Alina Wildenberg
- Chair of High Pressure Gas Dynamics, Shock Wave Laboratory, RWTH Aachen University, 52056Aachen, Germany
| | - Can Huang
- Institute of Technical Thermodynamics, RWTH Aachen University, 52056Aachen, Germany
| | - Sebastian Faller
- Institute for Combustion Technology, RWTH Aachen University, 52056Aachen, Germany
| | - Yihua Ren
- Institute for Combustion Technology, RWTH Aachen University, 52056Aachen, Germany
| | - Joachim Beeckmann
- Institute for Combustion Technology, RWTH Aachen University, 52056Aachen, Germany
| | - Kai Leonhard
- Institute of Technical Thermodynamics, RWTH Aachen University, 52056Aachen, Germany
| | - Karl Alexander Heufer
- Chair of High Pressure Gas Dynamics, Shock Wave Laboratory, RWTH Aachen University, 52056Aachen, Germany
| | - Nils Hansen
- Combustion Research Facility, Sandia National Laboratories, Livermore, California94551, United States
| | - Heinz Pitsch
- Institute for Combustion Technology, RWTH Aachen University, 52056Aachen, Germany
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9
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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10
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Abstract
Algorithmic reaction exploration based on transition state searches has already made inroads into many niche applications, but its potential as a general-purpose tool is still largely unrealized. Computational cost and the absence of benchmark problems involving larger molecules remain obstacles to further progress. Here an ultra-low cost exploration algorithm is implemented and used to explore the reactivity of unimolecular and bimolecular reactants, comprising a total of 581 reactions involving 51 distinct reactants. The algorithm discovers all established reaction pathways, where such comparisons are possible, while also revealing a much richer reactivity landscape, including lower barrier reaction pathways and a strong dependence of reaction conformation in the apparent barriers of the reported reactions. The diversity of these benchmarks illustrate that reaction exploration algorithms are approaching general-purpose capability.
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Affiliation(s)
- Qiyuan Zhao
- Davidson School of Chemical EngineeringPurdue UniversityWest LafayetteIN47906USA
| | - Brett M. Savoie
- Davidson School of Chemical EngineeringPurdue UniversityWest LafayetteIN47906USA
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11
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Xing L, Lian L, Wang Z, Cheng Z, He Y, Cui J, Truhlar DG. Lowering of Reaction Rates by Energetically Favorable Hydrogen Bonding in the Transition State. Degradation of Biofuel Ketohydroperoxides by OH. J Am Chem Soc 2022; 144:16984-16995. [PMID: 36069709 DOI: 10.1021/jacs.2c06124] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Ketohydroperoxides (KHPs) are oxygenates with carbonyl and hydroperoxy functional groups, and they are generated under combustion and atmospheric conditions. Their fate is crucial for secondary organic aerosol formation in the troposphere and for the ignition processes of biofuels in advanced combustion engines. We investigated the thermodynamics and kinetics of nine hydrogen abstraction reactions from four ether KHPs by OH. We find that the rate constants are strongly affected by entropic effects whose estimation requires a consideration of higher-energy conformers of the transition state. A density functional was selected for these reactions by comparison to coupled cluster calculations, and it was used for calculations by multistructural canonical transition-state theory with multidimensional tunneling over the temperature range of 200-2000 K. We find that the effect of multistructural torsional anharmonicity is very large and quite different for the various ether KHP reactions. A leading cause of the structural dependence is the dominance of entropic factors due to the lack of hydrogen bonding in some of the higher-energy conformers of the transition states. Four of the reactions involve abstraction from the α-carbon (the carbon vicinal to the hydroperoxide group); they exhibit nonmonotonic temperature dependence with complex fuel-specific dependence. The rate constants for abstraction from a non-α-carbon of a given KHP can be faster than the ones for abstraction from an α-carbon; in two cases, this is due to entropy, and in one case, the non-α-carbon abstraction has a lower energy barrier. Tunneling and recrossing effects are also found to be important.
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Affiliation(s)
- Lili Xing
- Energy and Power Engineering Institute, Henan University of Science and Technology, Luoyang 471003, Henan, China.,Department of Chemistry, Chemical Theory Center, and Minnesota Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431, United States
| | - Liuchao Lian
- Energy and Power Engineering Institute, Henan University of Science and Technology, Luoyang 471003, Henan, China
| | - Zhandong Wang
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029, Anhui, China
| | - Zhanjun Cheng
- School of Environmental Science and Engineering, Tianjin University, Tianjin 300072, China
| | - Yunrui He
- Energy and Power Engineering Institute, Henan University of Science and Technology, Luoyang 471003, Henan, China
| | - Jintao Cui
- Energy and Power Engineering Institute, Henan University of Science and Technology, Luoyang 471003, Henan, China
| | - Donald G Truhlar
- Department of Chemistry, Chemical Theory Center, and Minnesota Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431, United States
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12
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Zhou Z, Yang J, Yuan W, Wang Z, Pan Y, Qi F. Probing combustion and catalysis intermediates by synchrotron vacuum ultraviolet photoionization molecular-beam mass spectrometry: recent progress and future opportunities. Phys Chem Chem Phys 2022; 24:21567-21577. [DOI: 10.1039/d2cp02899a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Soft photoionization molecular-beam mass spectrometry (PI MBMS) with synchrotron vacuum ultraviolet light (SVUV) has has a significant development and broad applications in recent decades. Particularly, the tunability of SVUV enables...
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13
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Taatjes CA, Caravan RL, Winiberg FAF, Zuraski K, Au K, Sheps L, Osborn DL, Vereecken L, Percival CJ. Insertion products in the reaction of carbonyl oxide Criegee intermediates with acids: Chloro(hydroperoxy)methane formation from reaction of CH2OO with HCl and DCl. Mol Phys 2021. [DOI: 10.1080/00268976.2021.1975199] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Affiliation(s)
- Craig A. Taatjes
- Combustion Research Facility, Mailstop 9055, Sandia National Laboratories, Livermore, CA, USA
| | - Rebecca L. Caravan
- Combustion Research Facility, Mailstop 9055, Sandia National Laboratories, Livermore, CA, USA
- NASA Postdoctoral Program Fellow, NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, IL, USA
| | - Frank A. F. Winiberg
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
- California Institute of Technology, Pasadena, CA, USA
| | - Kristen Zuraski
- NASA Postdoctoral Program Fellow, NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - Kendrew Au
- Combustion Research Facility, Mailstop 9055, Sandia National Laboratories, Livermore, CA, USA
| | - Leonid Sheps
- Combustion Research Facility, Mailstop 9055, Sandia National Laboratories, Livermore, CA, USA
| | - David L. Osborn
- Combustion Research Facility, Mailstop 9055, Sandia National Laboratories, Livermore, CA, USA
- Department of Chemical Engineering, University of California, Davis, CA, USA
| | - Luc Vereecken
- Institute of Energy and Climate Research, Forschungszentrum Jülich GmbH, Jülich, Germany
| | - Carl J. Percival
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
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14
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Huang J, Huang C, Wu X, Hou Q, Tian G, Yang J, Zhang F. Combined experimental and theoretical study on photoionization cross sections of benzonitrile and o/m/p-cyanotoluene. J Chem Phys 2021; 154:244301. [PMID: 34241365 DOI: 10.1063/5.0053119] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Photoionization cross sections (PICSs) for the products of the reaction from CN with toluene, including benzonitrile and o/m/p-cyanotoluene, were obtained at photon energies ranging from ionization thresholds to 14 eV by tunable synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS). Theoretical calculations based on the frozen-core Hartree-Fock approximation and Franck-Condon simulations were carried out to cross-verify the measured PICS. The results show that the photoionization cross sections of benzonitrile and cyanotoluene isomers are similar. The generalized charge decomposition analysis was used to investigate the components of the highest occupied molecular orbital (HOMO) and HOMO-1. It was found that the HOMO and HOMO-1 of benzonitrile and cyanotoluene isomers are dominated by the features of the benzene ring, indicating that the substitution of CN and methyl has a minor influence on the PICS of the studied molecules. The reported PICS on benzonitrile and cyanotoluene isomers in the present work could contribute to the near-threshold PIMS experiments and determine the ionization and dissociation rates in interstellar space for these crucial species. The theoretical analysis on characteristics of molecular orbitals provides clues to estimating the PICS of similar substituted aromatic compounds.
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Affiliation(s)
- Jiabin Huang
- Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China
| | - Can Huang
- Chair of Technical Thermodynamics, RWTH Aachen University, 52062 Aachen, Germany
| | - Xiaoqing Wu
- Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China
| | - Qifeng Hou
- Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China
| | - Guangjun Tian
- Key Laboratory for Microstructural Material Physics of Hebei Province, School of Science, Yanshan University, Qinhuangdao 066004, People's Republic of China
| | - Jiuzhong Yang
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230029, People's Republic of China
| | - Feng Zhang
- Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China
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15
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Bierkandt T, Oßwald P, Gaiser N, Krüger D, Köhler M, Hoener M, Shaqiri S, Kaczmarek D, Karakaya Y, Hemberger P, Kasper T. Observation of low‐temperature chemistry products in laminar premixed low‐pressure flames by molecular‐beam mass spectrometry. INT J CHEM KINET 2021. [DOI: 10.1002/kin.21503] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Thomas Bierkandt
- German Aerospace Center (DLR) Institute of Combustion Technology Stuttgart Germany
| | - Patrick Oßwald
- German Aerospace Center (DLR) Institute of Combustion Technology Stuttgart Germany
| | - Nina Gaiser
- German Aerospace Center (DLR) Institute of Combustion Technology Stuttgart Germany
| | - Dominik Krüger
- German Aerospace Center (DLR) Institute of Combustion Technology Stuttgart Germany
| | - Markus Köhler
- German Aerospace Center (DLR) Institute of Combustion Technology Stuttgart Germany
| | - Martin Hoener
- Mass Spectrometry in Reactive Flows University of Duisburg‐Essen Duisburg Germany
| | - Shkelqim Shaqiri
- Mass Spectrometry in Reactive Flows University of Duisburg‐Essen Duisburg Germany
| | - Dennis Kaczmarek
- Mass Spectrometry in Reactive Flows University of Duisburg‐Essen Duisburg Germany
| | - Yasin Karakaya
- Mass Spectrometry in Reactive Flows University of Duisburg‐Essen Duisburg Germany
| | - Patrick Hemberger
- Laboratory for Synchrotron Radiation and Femtochemistry Paul Scherrer Institute Villigen Switzerland
| | - Tina Kasper
- Mass Spectrometry in Reactive Flows University of Duisburg‐Essen Duisburg Germany
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16
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Yang B. Towards predictive combustion kinetic models: Progress in model analysis and informative experiments. Proceedings of the Combustion Institute 2021; 38:199-222. [DOI: 10.1016/j.proci.2020.11.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
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17
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Zhou B, Huang E, Almeida R, Gurses S, Ungar A, Zetterberg J, Kulkarni A, Kronawitter CX, Osborn DL, Hansen N, Frank JH. Near-Surface Imaging of the Multicomponent Gas Phase above a Silver Catalyst during Partial Oxidation of Methanol. ACS Catal 2020. [DOI: 10.1021/acscatal.0c04396] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Bo Zhou
- Combustion Research Facility, Sandia National Laboratories, Livermore, California 94551, United States
- Department of Mechanics and Aerospace Engineering, Southern University of Science and Technology, Shenzhen 518055, P. R. China
| | - Erxiong Huang
- Combustion Research Facility, Sandia National Laboratories, Livermore, California 94551, United States
| | - Raybel Almeida
- Combustion Research Facility, Sandia National Laboratories, Livermore, California 94551, United States
| | - Sadi Gurses
- Department of Chemical Engineering, University of California, Davis, California 95616, United States
| | - Alexander Ungar
- Combustion Research Facility, Sandia National Laboratories, Livermore, California 94551, United States
| | - Johan Zetterberg
- Division of Combustion Physics, Lund University, Lund SE-221 00, Sweden
| | - Ambarish Kulkarni
- Department of Chemical Engineering, University of California, Davis, California 95616, United States
| | - Coleman X. Kronawitter
- Department of Chemical Engineering, University of California, Davis, California 95616, United States
| | - David L. Osborn
- Combustion Research Facility, Sandia National Laboratories, Livermore, California 94551, United States
| | - Nils Hansen
- Combustion Research Facility, Sandia National Laboratories, Livermore, California 94551, United States
| | - Jonathan H. Frank
- Combustion Research Facility, Sandia National Laboratories, Livermore, California 94551, United States
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18
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Terracciano AC, Neupane S, Popolan-Vaida DM, Blair RG, Hansen N, Vaghjiani GL, Vasu SS. Elucidating the differences in oxidation of high-performance α- and β- diisobutylene biofuels via Synchrotron photoionization mass spectrometry. Sci Rep 2020; 10:21776. [PMID: 33311537 DOI: 10.1038/s41598-020-76462-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Accepted: 10/21/2020] [Indexed: 11/09/2022] Open
Abstract
Biofuels are a promising ecologically viable and renewable alternative to petroleum fuels, with the potential to reduce net greenhouse gas emissions. However, biomass sourced fuels are often produced as blends of hydrocarbons and their oxygenates. Such blending complicates the implementation of these fuels in combustion applications. Variations in a biofuel's composition will dictate combustion properties such as auto ignition temperature, reaction delay time, and reaction pathways. A handful of novel drop-in replacement biofuels for conventional transportation fuels have recently been down selected from a list of over 10,000 potential candidates as part of the U.S. Department of Energy's (DOE) Co-Optimization of Fuels and Engines (Co-Optima) initiative. Diisobutylene (DIB) is one such high-performing hydrocarbon which can readily be produced from the dehydration and dimerization of isobutanol, produced from the fermentation of biomass-derived sugars. The two most common isomers realized, from this process, are 2,4,4-trimethyl-1-pentene (α-DIB) and 2,4,4-trimethyl-2-pentene (β-DIB). Due to a difference in olefinic bond location, the α- and β- isomer exhibit dramatically different ignition temperatures at constant pressure and equivalence ratio. This may be attributed to different fragmentation pathways enabled by allylic versus vinylic carbons. For optimal implementation of these biofuel candidates, explicit identification of the intermediates formed during the combustion of each of the isomers is needed. To investigate the combustion pathways of these molecules, tunable vacuum ultraviolet (VUV) light (in the range 8.1-11.0 eV) available at the Lawrence Berkeley National Laboratory's Advanced Light Source (ALS) has been used in conjunction with a jet stirred reactor (JSR) and time-of-flight mass spectrometry to probe intermediates formed. Relative intensity curves for intermediate mass fragments produced during this process were obtained. Several important unique intermediates were identified at the lowest observable combustion temperature with static pressure of 93,325 Pa and for 1.5 s residence time. As this relatively short residence time is just after ignition, this study is targeted at the fuels' ignition events. Ignition characteristics for both isomers were found to be strongly dependent on the kinetics of C4 and C7 fragment production and decomposition, with the tert-butyl radical as a key intermediate species. However, the ignition of α-DIB exhibited larger concentrations of C4 compounds over C7, while the reverse was true for β-DIB. These identified species will allow for enhanced engineering modeling of fuel blending and engine design.
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19
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Abstract
The accelerating chemical effect of ozone addition on the oxidation chemistry of methyl hexanoate [CH3(CH2)4C(═O)OCH3] was investigated over a temperature range from 460 to 940 K. Using an externally heated jet-stirred reactor at p = 700 Torr (residence time τ = 1.3 s, stoichiometry φ = 0.5, 80% argon dilution), we explored the relevant chemical pathways by employing molecular-beam mass spectrometry with electron and single-photon ionization to trace the temperature dependencies of key intermediates, including many hydroperoxides. In the absence of ozone, reactivity is observed in the so-called low-temperature chemistry (LTC) regime between 550 and 700 K, which is governed by hydroperoxides formed from sequential O2 addition and isomerization reactions. At temperatures above 700 K, we observed the negative temperature coefficient (NTC) regime, in which the reactivity decreases with increasing temperatures, until near 800 K, where the reactivity increases again. Upon addition of ozone (1000 ppm), the overall reactivity of the system is dramatically changed due to the time scale of ozone decomposition in comparison to fuel oxidation time scales of the mixtures at different temperatures. While the LTC regime seems to be only slightly affected by the addition of ozone with respect to the identity and quantity of the observed intermediates, we observed an increased reactivity in the intermediate NTC temperature range. Furthermore, we observed experimental evidence for an additional oxidation regime in the range near 500 K, herein referred to as the extreme low-temperature chemistry (ELTC) regime. Experimental evidence and theoretical rate constant calculations indicate that this ELTC regime is likely to be initiated by H abstraction from methyl hexanoate via O atoms, which originate from thermal O3 decomposition. The theoretical calculations show that the rate constants for methyl ester initiation via abstraction by O atoms increase dramatically with the size of the methyl ester, suggesting that ELTC is likely not important for the smaller methyl esters. Experimental evidence is provided indicating that, similar to the LTC regime, the chemistry in the ELTC regime is dominated by hydroperoxide chemistry. However, mass spectra recorded at various reactor temperatures and at different photon energies provide experimental evidence of some differences in chemical species between the ELTC and the LTC temperature ranges.
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Affiliation(s)
- Aric C Rousso
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544, United States
| | - Ahren W Jasper
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Yiguang Ju
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544, United States
| | - Nils Hansen
- Combustion Research Facility, Sandia National Laboratories, Livermore, California 94551, United States
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20
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Abstract
We report experiments of ozone-initiated low-temperature oxidation of methyl crotonate (MC, CH3-CH═CH-C(O)OCH3) from 420 to 660 K in a near-atmospheric-pressure jet-stirred reactor using photoionization molecular-beam mass spectrometry as a sampling technique. In this temperature regime, no typical low-temperature combustion (LTC) reactions have been observed for MC when oxygen (O2) is used as the oxidizer. Upon ozone addition, significant oxidation of methyl crotonate is found. On the basis of experimentally observed energy-dependent mass peaks in combination with temperature-dependent mole fraction profiles and photoionization efficiency curves, we provide new insights into the methyl crotonate ozonolysis reaction network. The observed MC + O3 products, C5H8O5, are found to be related to the keto-hydroperoxides resulting from the isomerization of the primary ozonide. Evidence is also provided that molecular growth mainly results from cycloaddition reactions of the Criegee intermediate into aldehydes and alkenes as well as addition reactions of the Criegee intermediates to the double bond of methyl crotonate and sequential decomposition into ketones. Furthermore, species that contribute in large amounts to the low-temperature oxidation of methyl crotonate, like H2O2, CH3OOH, CH3OH, and HC(O)OH, are identified, and their mole fractions are reported. Additionally, preliminary modeling is performed which qualitatively captures the observed NTC behavior and reveals future research opportunities.
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Affiliation(s)
- X He
- Department of Physical Chemistry, Physikalisch-Technische Bundesanstalt (PTB), 38116 Braunschweig, Germany
| | - N Hansen
- Combustion Research Facility, Sandia National Laboratories, Livermore, California 94551, United States
| | - K Moshammer
- Department of Physical Chemistry, Physikalisch-Technische Bundesanstalt (PTB), 38116 Braunschweig, Germany
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21
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Abstract
Autoxidation has been acknowledged as a major oxidation pathway in a broad range of atmospherically important compounds including isoprene, monoterpenes, and very recently, dimethyl sulfide. Here, we present a high-level theoretical multiconformer transition-state theory study of the atmospheric autoxidation in amines exemplified by the atmospherically important trimethylamine (TMA) and dimethylamine and generalized by the study of the larger diethylamine. Overall, we find that the initial hydrogen shift reactions have rate coefficients greater than 0.1 s-1 and autoxidation is thus an important atmospheric pathway for amines. This autoxidation efficiently leads to the formation of hydroperoxy amides, a new type of atmospheric nitrogen-containing compounds, and for TMA, we experimentally confirm this. The conversion of amines to hydroperoxy amides may have important implications for nucleation and growth of atmospheric secondary organic aerosols and atmospheric OH recycling.
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Affiliation(s)
- Kristian H Møller
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark
| | - Torsten Berndt
- Atmospheric Chemistry Department (ACD), Leibniz Institute for Tropospheric Research (TROPOS), Permoserstraße 15, 04318 Leipzig, Germany
| | - Henrik G Kjaergaard
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark
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22
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Hoener M, Kaczmarek D, Bierkandt T, Bodi A, Hemberger P, Kasper T. A pressurized flow reactor combustion experiment interfaced with synchrotron double imaging photoelectron photoion coincidence spectroscopy. Rev Sci Instrum 2020; 91:045115. [PMID: 32357689 DOI: 10.1063/1.5141168] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2019] [Accepted: 03/29/2020] [Indexed: 06/11/2023]
Abstract
A new pressurized low-temperature combustion experiment has been commissioned at the Swiss Light Source, Paul Scherrer Institute. The experiment uses photoionization with tunable synchrotron radiation and double imaging photoelectron photoion coincidence (i2PEPICO) detection at the vacuum ultraviolet beamline. The experimental setup is described, including the high-pressure reactor experiment, sampling interface, and reactant delivery system. The CRF-PEPICO (Combustion Reactions Followed by Photoelectron Photoion Coincidence) endstation and VUV beamline are briefly elaborated. The novel aspects of the apparatus and the new components are elucidated in detail, such as the fluid supply system to the reactor and the reactor integration into the endstation. We also present a system overview of the experimental setup. The technical details are followed by a description of the experimental procedure used to operate the pressurized flow reactor setup. Finally, first experimental results demonstrating the capability of the setup are provided and analyzed. A major advantage of this new experiment is that the excellent isomer resolution capabilities of the i2PEPICO technique can be transferred to the investigation of reactions at elevated pressures of several bars. This enables the investigation of pressure effects on the reactivity of fuel mixtures and covers more realistic conditions found in technical combustors. The capability to obtain quantitative oxidation data is confirmed, and the main and certain intermediate species are quantified for a selected condition. The results show excellent agreement with a chemical kinetics model and previously published reference measurements performed with a gas chromatography setup.
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Affiliation(s)
- M Hoener
- Mass Spectrometry in Reactive Flows - Institute for Combustion and Gas Dynamics (IVG), University Duisburg-Essen, Duisburg 47057, Germany
| | - D Kaczmarek
- Mass Spectrometry in Reactive Flows - Institute for Combustion and Gas Dynamics (IVG), University Duisburg-Essen, Duisburg 47057, Germany
| | - T Bierkandt
- German Aerospace Center (DLR) - Institute of Combustion Technology, Stuttgart 70569, Germany
| | - A Bodi
- Laboratory for Synchrotron Radiation and Femtochemistry - Paul Scherrer Institute, Villigen 5232, Switzerland
| | - P Hemberger
- Laboratory for Synchrotron Radiation and Femtochemistry - Paul Scherrer Institute, Villigen 5232, Switzerland
| | - T Kasper
- Mass Spectrometry in Reactive Flows - Institute for Combustion and Gas Dynamics (IVG), University Duisburg-Essen, Duisburg 47057, Germany
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23
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Hansen N, Moshammer K, Jasper AW. Isomer-Selective Detection of Keto-Hydroperoxides in the Low-Temperature Oxidation of Tetrahydrofuran. J Phys Chem A 2019; 123:8274-8284. [PMID: 31483667 DOI: 10.1021/acs.jpca.9b07017] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Keto-hydroperoxides (KHPs) are reactive, partially oxidized intermediates that play a central role in chain-branching reactions during the gas-phase low-temperature oxidation of hydrocarbons and oxygenated species. Although multiple isomeric forms of the KHP intermediate are possible in complex oxidation environments when multiple reactant radicals exist that contain nonequivalent O2 addition sites, isomer-resolved data of KHPs have not been reported. In this work, we provide partially isomer-resolved detection and quantification of the KHPs that form during the low-temperature oxidation of tetrahydrofuran (THF, cycl.-O-CH2CH2CH2CH2-). We describe how these short-lived KHPs were detected, identified, and quantified using integrated experimental and theoretical approaches. The experimental approaches were based on direct molecular-beam sampling from a jet-stirred reactor operated at near-atmospheric pressure and at temperatures between 500 and 700 K, followed by mass spectrometry with single-photon ionization via tunable synchrotron-generated vacuum-ultraviolet radiation, and the identification of fragmentation patterns. The interpretation of the experiments was guided by theoretical calculations of ionization thresholds, fragment appearance energies, and photoionization cross sections. On the basis of the experimentally observed and theoretically calculated ionization and fragment appearance energies, KHP isomers could be distinguished as originating from H-abstraction reactions from either the α-C adjacent to the O atom or the β-C atoms. Temperature-dependent concentration profiles of the partially resolved isomeric KHP intermediates were determined in the range of 500-700 K, and the results indicate that the observed KHP isomers are formed overwhelmingly (∼99%) from the α-C THF radical. Comparisons of the partially isomer-resolved quantification of the KHPs to up-to-date kinetic modeling results reveal new opportunities for the development of a next-generation THF oxidation mechanism.
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Affiliation(s)
- Nils Hansen
- Combustion Research Facility , Sandia National Laboratories , Livermore , California 94551 , United States
| | - Kai Moshammer
- Physikalisch-Technische Bundesanstalt , Bundesallee 100 , 38116 Braunschweig , Germany
| | - Ahren W Jasper
- Chemical Sciences and Engineering Division , Argonne National Laboratory , Lemont , Illinois 60439 , United States
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24
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Huang C, Yang B, Zhang F. Calculation of the absolute photoionization cross-sections for C1-C4 Criegee intermediates and vinyl hydroperoxides. J Chem Phys 2019; 150:164305. [PMID: 31042918 DOI: 10.1063/1.5088408] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Criegee Intermediates (CIs) and their isomer Vinyl Hydroperoxides (VHPs) are crucial intermediates in the ozonolysis of alkenes. To better understand the underlying chemistry of CIs and VHPs, progress has been made to detect and identify them by photoionization mass spectrometric experiments. Further reliable quantitative information about these elusive intermediates requires their photoionization cross sections. The present work systematically investigated the near-threshold absolute photoionization cross-sections for ten C1-C4 CIs and VHPs, i.e., formaldehyde oxide (CH2OO), acetaldehyde oxide (syn-/anti-CH3CHOO), acetone oxide ((CH3)2COO), syn-CH3-anti-(cis-CH=CH2)COO, syn-CH3-anti-(trans-CH=CH2)COO and vinyl hydroperoxide (CH2CHOOH), 2-hydroperoxypropene (CH2=C(CH3)OOH), syn-CH2 = anti-(cis-CH=CH2)-COOH, syn-CH2 = anti-(trans-CH=CH2)COOH. The adiabatic ionization energies (AIEs) were calculated at the DLPNO-CCSD(T)/CBS level with uncertainties of less than 0.05 eV. The calculated AIEs for C1-C4 CIs and VHPs vary from 8.75 to 10.0 eV with the AIEs decreasing as the substitutions increase. Franck-Condon factors were calculated with the double Duschinsky approximation and the ionization spectra were obtained based on the calculated ionization energies. Pure electronic photoionization cross sections are calculated by the frozen-core Hartree-Fock (FCHF) approximation. The final determined absolute cross sections are around 4.5-6 Mb for the first and second ionization of CIs and 15-25 Mb for VHPs. It is found that the addition of a methyl group or an unsaturated vinyl substitution for the CIs does not substantially change the absolute value of their cross sections.
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Affiliation(s)
- Can Huang
- Center for Combustion Energy and Key Laboratory for Thermal Science and Power Engineering of MOE, Tsinghua University, Beijing 100084, People's Republic of China
| | - Bin Yang
- Center for Combustion Energy and Key Laboratory for Thermal Science and Power Engineering of MOE, Tsinghua University, Beijing 100084, People's Republic of China
| | - Feng Zhang
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230029, People's Republic of China
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25
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Taatjes CA, Khan MAH, Eskola AJ, Percival CJ, Osborn DL, Wallington TJ, Shallcross DE. Reaction of Perfluorooctanoic Acid with Criegee Intermediates and Implications for the Atmospheric Fate of Perfluorocarboxylic Acids. Environ Sci Technol 2019; 53:1245-1251. [PMID: 30589541 DOI: 10.1021/acs.est.8b05073] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
The reaction of perfluorooctanoic acid with the smallest carbonyl oxide Criegee intermediate, CH2OO, has been measured and is very rapid, with a rate coefficient of (4.9 ± 0.8) × 10-10 cm3 s-1, similar to that for reactions of Criegee intermediates with other organic acids. Evidence is shown for the formation of hydroperoxymethyl perfluorooctanoate as a product. With such a large rate coefficient, reaction with Criegee intermediates can be a substantial contributor to atmospheric removal of perfluorocarboxylic acids. However, the atmospheric fates of the ester product largely regenerate the initial acid reactant. Wet deposition regenerates the perfluorocarboxylic acid via condensed-phase hydrolysis. Gas-phase reaction with OH is expected principally to result in formation of the acid anhydride, which also hydrolyzes to regenerate the acid, although a minor channel could lead to destruction of the perfluorinated backbone.
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Affiliation(s)
- Craig A Taatjes
- Combustion Research Facility, Mail Stop 9055 , Sandia National Laboratories, Livermore , California 94551-0969 United States
| | - M Anwar H Khan
- School of Chemistry , The University of Bristol , Cantock's Close BS8 1TS , Bristol , U.K
| | - Arkke J Eskola
- Combustion Research Facility, Mail Stop 9055 , Sandia National Laboratories, Livermore , California 94551-0969 United States
- Department of Chemistry , University of Helsinki , P.O. Box 55 (A.I. Virtasen aukio 1) , FI-00014 Helsinki , Finland
| | - Carl J Percival
- The Centre for Atmospheric Science, The School of Earth, Atmospheric and Environmental Science , The University of Manchester , Simon Building, Brunswick Street , Manchester , M13 9PL , U.K
- Jet Propulsion Laboratory , California Institute of Technology , 4800 Oak Grove Drive , Pasadena , California 91109 United States
| | - David L Osborn
- Combustion Research Facility, Mail Stop 9055 , Sandia National Laboratories, Livermore , California 94551-0969 United States
| | - Timothy J Wallington
- Research & Advanced Engineering , Ford Motor Company , Dearborn , Michigan 48121 United States
| | - Dudley E Shallcross
- School of Chemistry , The University of Bristol , Cantock's Close BS8 1TS , Bristol , U.K
- Department of Chemistry , University of the Western Cape , Robert Sobukwe Road , Bellville 7535 , South Africa
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26
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Hrodmarsson HR, Loison JC, Jacovella U, Holland DMP, Boyé-Péronne S, Gans B, Garcia GA, Nahon L, Pratt ST. Valence-Shell Photoionization of C4H5: The 2-Butyn-1-yl Radical. J Phys Chem A 2019; 123:1521-1528. [DOI: 10.1021/acs.jpca.8b11809] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- H. R. Hrodmarsson
- Synchrotron Soleil, L’Orme des Merisiers, F-91192 Gif-sur-Yvette, France
| | - J.-C. Loison
- Institut des Sciences Moléculaires, Université Bordeaux, 33400 Talence, France
| | - U. Jacovella
- Laboratorium für Physikalische Chemie, ETH Zürich, 8093 Zürich, Switzerland
| | - D. M. P. Holland
- STFC, Daresbury Laboratory, Daresbury, Warrington, Cheshire WA4 4AD, United Kingdom
| | - S. Boyé-Péronne
- Institut des Sciences Moléculaires d’Orsay, UMR 8214, CNRS & Univ. Paris-Sud & Université Paris-Saclay, F-91405 Orsay, France
| | - B. Gans
- Institut des Sciences Moléculaires d’Orsay, UMR 8214, CNRS & Univ. Paris-Sud & Université Paris-Saclay, F-91405 Orsay, France
| | - G. A. Garcia
- Synchrotron Soleil, L’Orme des Merisiers, F-91192 Gif-sur-Yvette, France
| | - L. Nahon
- Synchrotron Soleil, L’Orme des Merisiers, F-91192 Gif-sur-Yvette, France
| | - S. T. Pratt
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439 United States
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27
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Abstract
Abstract
Current topics in combustion chemistry include aspects of a changing fuel spectrum with a focus on reducing emissions and increasing efficiency. This article is intended to provide an overview of selected recent work in combustion chemistry, especially addressing reaction pathways from fuel decomposition to emissions. The role of the molecular fuel structure will be emphasized for the formation of certain regulated and unregulated species from individual fuels and their mixtures, exemplarily including fuel compounds such as alkanes, alkenes, ethers, alcohols, ketones, esters, and furan derivatives. Depending on the combustion conditions, different temperature regimes are important and can lead to different reaction classes. Laboratory reactors and flames are prime sources and targets from which such detailed chemical information can be obtained and verified with a number of advanced diagnostic techniques, often supported by theoretical work and simulation with combustion models developed to transfer relevant details of chemical mechanisms into practical applications. Regarding the need for cleaner combustion processes, some related background and perspectives will be provided regarding the context for future chemistry research in combustion energy science.
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Affiliation(s)
- Katharina Kohse-Höinghaus
- Department of Chemistry , Bielefeld University , Universitätsstraße 25 , Bielefeld D-33615 , Germany , Phone: +49 5211062052
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Rousso AC, Hansen N, Jasper AW, Ju Y. Identification of the Criegee intermediate reaction network in ethylene ozonolysis: impact on energy conversion strategies and atmospheric chemistry. Phys Chem Chem Phys 2019; 21:7341-7357. [DOI: 10.1039/c9cp00473d] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The reaction network of the simplest Criegee intermediate (CI) CH2OO has been studied experimentally during the ozonolysis of ethylene.
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Affiliation(s)
- Aric C. Rousso
- Department of Mechanical and Aerospace Engineering
- Princeton University
- USA
| | - Nils Hansen
- Combustion Research Facility
- Sandia National Laboratories
- Livermore
- USA
| | - Ahren W. Jasper
- Chemical Sciences and Engineering Division
- Argonne National Laboratory
- Lemont
- USA
| | - Yiguang Ju
- Department of Mechanical and Aerospace Engineering
- Princeton University
- USA
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29
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Abstract
Ethylene oxidation initiated by ozone addition (ozonolysis) is carried out in a jet-stirred reactor from 300 to 1000 K to explore the kinetic pathways relevant to low-temperature oxidation. The temperature dependencies of species' mole fractions are quantified using molecular-beam mass spectrometry with electron ionization and single-photon ionization employing tunable synchrotron-generated vacuum-ultraviolet radiation. Upon ozone addition, significant ethylene oxidation is found in the low-temperature regime from 300 to 600 K. Here, we provide new insights into the ethylene ozonolysis reaction network via identification and quantification of previously elusive intermediates by combining experimental photoionization energy scans and ab initio threshold energy calculations for isomer identification. Specifically, the C2H4 + O3 adduct C2H4O3 is identified as a keto-hydroperoxide (hydroperoxy-acetaldehyde, HOOCH2CHO) based on the calculated and experimentally observed ionization energy of 9.80 (±0.05) eV. Quantification using a photoionization cross-section of 5 Mb at 10.5 eV results in 5 ppm at atmospheric conditions, which decreases monotonically with temperature until 550 K. Other hydroperoxide species that contribute in larger amounts to the low-temperature oxidation of C2H4, like H2O2, CH3OOH, and C2H5OOH, are identified and their temperature-dependent mole fractions are reported. The experimental evidence for additional oxygenated species such as methanol, ketene, acetaldehyde, and hydroxy-acetaldehyde suggest multiple active oxidation routes. This experimental investigation closes the gap between ozonolysis at atmospheric and elevated temperature conditions and provides a database for future modeling.
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Affiliation(s)
- Aric C Rousso
- Department of Mechanical and Aerospace Engineering , Princeton University , Princeton , New Jersey 08544 , United States
| | - Nils Hansen
- Combustion Research Facility , Sandia National Laboratories , Livermore , California 94551 , United States
| | - Ahren W Jasper
- Chemical Sciences and Engineering Division , Argonne National Laboratory , Argonne , Illinois 60439 , United States
| | - Yiguang Ju
- Department of Mechanical and Aerospace Engineering , Princeton University , Princeton , New Jersey 08544 , United States
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Chen MW, Rotavera B, Chao W, Zádor J, Taatjes CA. Direct measurement of ˙OH and HO 2˙ formation in ˙R + O 2 reactions of cyclohexane and tetrahydropyran. Phys Chem Chem Phys 2018; 20:10815-10825. [PMID: 29417107 DOI: 10.1039/c7cp08164b] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Formation of the key general radical chain carriers, ˙OH and HO2˙, during pulsed-photolytic ˙Cl-initiated oxidation of tetrahydropyran and cyclohexane are measured with time-resolved infrared absorption in a temperature-controlled Herriott multipass cell in the temperature range of 500-750 K at 20 Torr. The experiments show two distinct timescales for HO2˙ and ˙OH formation in the oxidation of both fuels. Analysis of the timescales reveals striking differences in behavior between the two fuels. In both cyclohexane and tetrahydropyran oxidation, a faster timescale is strongly related to the "well-skipping" (˙R + O2 → alkene + HO2˙ or cyclic ether + ˙OH) mechanism and is expected to have, at most, a weak temperature dependence. Indeed, the fast HO2˙ formation timescale is nearly temperature independent both for cyclohexyl + O2 and for tetrahydropyranyl + O2 below 700 K. A slower HO2˙ formation timescale in cyclohexane oxidation is shown to be linked to the sequential ˙R + O2 → ROO˙ → alkene + HO2˙ pathway, and displays a strong temperature dependence mainly from the final step (with energy barrier ∼32.5 kcal mol-1). In contrast, the slower HO2˙ formation timescale in tetrahydropyran oxidation is surprisingly temperature insensitive across all measured temperatures. Although the ˙OH formation timescales in tetrahydropyran oxidation show a temperature dependence similar to the cyclohexane oxidation, the temperature dependence of ˙OH yield is opposite in both cases. This significant difference of HO2˙ formation kinetics and ˙OH formation yield for the tetrahydropyran oxidation can arise from contributions related to ring-opening pathways in the tetrahydropyranyl + O2 system that compete with the typical ˙R + O2 reaction scheme. This comparison of two similar fuels demonstrates the consequences of differing chemical mechanisms on ˙OH and HO2˙ formation and shows that they can be highlighted by analysis of the eigenvalues of a system of simplified kinetic equations for the alkylperoxy-centered ˙R + O2 reaction pathways. We suggest that such analysis can be more generally applied to complex or poorly known oxidation systems.
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Affiliation(s)
- Ming-Wei Chen
- Combustion Research Facility, Sandia National Laboratories, Livermore, California 94550, USA.
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Wang Z, Popolan-Vaida DM, Chen B, Moshammer K, Mohamed SY, Wang H, Sioud S, Raji MA, Kohse-Höinghaus K, Hansen N, Dagaut P, Leone SR, Sarathy SM. Unraveling the structure and chemical mechanisms of highly oxygenated intermediates in oxidation of organic compounds. Proc Natl Acad Sci U S A 2017; 114:13102-13107. [PMID: 29183984 PMCID: PMC5740676 DOI: 10.1073/pnas.1707564114] [Citation(s) in RCA: 88] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Decades of research on the autooxidation of organic compounds have provided fundamental and practical insights into these processes; however, the structure of many key autooxidation intermediates and the reactions leading to their formation still remain unclear. This work provides additional experimental evidence that highly oxygenated intermediates with one or more hydroperoxy groups are prevalent in the autooxidation of various oxygenated (e.g., alcohol, aldehyde, keto compounds, ether, and ester) and nonoxygenated (e.g., normal alkane, branched alkane, and cycloalkane) organic compounds. These findings improve our understanding of autooxidation reaction mechanisms that are routinely used to predict fuel ignition and oxidative stability of liquid hydrocarbons, while also providing insights relevant to the formation mechanisms of tropospheric aerosol building blocks. The direct observation of highly oxygenated intermediates for the autooxidation of alkanes at 500-600 K builds upon prior observations made in atmospheric conditions for the autooxidation of terpenes and other unsaturated hydrocarbons; it shows that highly oxygenated intermediates are stable at conditions above room temperature. These results further reveal that highly oxygenated intermediates are not only accessible by chemical activation but also by thermal activation. Theoretical calculations on H-atom migration reactions are presented to rationalize the relationship between the organic compound's molecular structure (n-alkane, branched alkane, and cycloalkane) and its propensity to produce highly oxygenated intermediates via extensive autooxidation of hydroperoxyalkylperoxy radicals. Finally, detailed chemical kinetic simulations demonstrate the influence of these additional reaction pathways on the ignition of practical fuels.
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Affiliation(s)
- Zhandong Wang
- Clean Combustion Research Center, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia;
| | - Denisia M Popolan-Vaida
- Department of Chemistry, University of California, Berkeley, CA 94720
- Department of Physics, University of California, Berkeley, CA 94720
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720
- Department of Chemistry, University of Central Florida, Orlando, FL 32816-2450
| | - Bingjie Chen
- Clean Combustion Research Center, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
| | - Kai Moshammer
- Combustion Research Facility, Sandia National Laboratories, Livermore, CA 94551
- Physikalisch-Technische Bundesanstalt, 38116 Braunschweig, Germany
| | - Samah Y Mohamed
- Clean Combustion Research Center, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
| | - Heng Wang
- Clean Combustion Research Center, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
| | - Salim Sioud
- Analytical Core Laboratory, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
| | - Misjudeen A Raji
- Analytical Core Laboratory, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
| | | | - Nils Hansen
- Combustion Research Facility, Sandia National Laboratories, Livermore, CA 94551
| | - Philippe Dagaut
- CNRS, Institut National des Sciences de l'Ingénierie et des Systèmes, Institut de Combustion, Aérothermique, Réactivité et Environnement, 45071, Orléans, Cedex 2, France
| | - Stephen R Leone
- Department of Chemistry, University of California, Berkeley, CA 94720
- Department of Physics, University of California, Berkeley, CA 94720
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720
| | - S Mani Sarathy
- Clean Combustion Research Center, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia;
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Pieper J, Schmitt S, Hemken C, Davies E, Wullenkord J, Brockhinke A, Krüger J, Garcia GA, Nahon L, Lucassen A, Eisfeld W, Kohse-höinghaus K. Isomer Identification in Flames with Double-Imaging Photoelectron/Photoion Coincidence Spectroscopy (i 2 PEPICO) using Measured and Calculated Reference Photoelectron Spectra. ACTA ACUST UNITED AC 2018; 232:153-87. [DOI: 10.1515/zpch-2017-1009] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
Double-imaging photoelectron/photoion coincidence (i2PEPICO) spectroscopy using a multiplexing, time-efficient, fixed-photon-energy approach offers important opportunities of gas-phase analysis. Building on successful applications in combustion systems that have demonstrated the discriminative power of this technique, we attempt here to push the limits of its application further to more chemically complex combustion examples. The present investigation is devoted to identifying and potentially quantifying compounds featuring five heavy atoms in laminar, premixed low-pressure flames of hydrocarbon and oxygenated fuels and their mixtures. In these combustion examples from flames of cyclopentene, iso-pentane, iso-pentane blended with dimethyl ether (DME), and diethyl ether (DEE), we focus on the unambiguous assignment and quantitative detection of species with the sum formulae C5H6, C5H7, C5H8, C5H10, and C4H8O in the respective isomer mixtures, attempting to provide answers to specific chemical questions for each of these examples. To analyze the obtained i2PEPICO results from these combustion situations, photoelectron spectra (PES) from pure reference compounds, including several examples previously unavailable in the literature, were recorded with the same experimental setup as used in the flame measurements. In addition, PES of two species where reference spectra have not been obtained, namely 2-methyl-1-butene (C5H10) and the 2-cyclopentenyl radical (C5H7), were calculated on the basis of high-level ab initio calculations and Franck-Condon (FC) simulations. These reference measurements and quantum chemical calculations support the early fuel decomposition scheme in the cyclopentene flame towards 2-cyclopentenyl as the dominant fuel radical as well as the prevalence of branched intermediates in the early fuel destruction reactions in the iso-pentane flame, with only minor influences from DME addition. Furthermore, the presence of ethyl vinyl ether (EVE) in DEE flames that was predicted by a recent DEE combustion mechanism could be confirmed unambiguously. While combustion measurements using i2PEPICO can be readily obtained in isomer-rich situations, we wish to highlight the crucial need for high-quality reference information to assign and evaluate the obtained spectra.
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Hansen N, Wullenkord J, Obenchain DA, Graf I, Kohse-Höinghaus K, Grabow JU. Microwave spectroscopic detection of flame-sampled combustion intermediates. RSC Adv 2017. [DOI: 10.1039/c7ra06483g] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Microwave spectroscopy was used to detect and identify combustion intermediates after sampling out of laboratory-scale model flames.
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Affiliation(s)
- N. Hansen
- Combustion Research Facility
- Sandia National Laboratories
- Livermore
- USA
| | - J. Wullenkord
- Department of Chemistry
- Bielefeld University
- D-33615 Bielefeld
- Germany
| | - D. A. Obenchain
- Institut für Physikalische Chemie & Elektrochemie
- Gottfried-Wilhelm-Leibniz-University Hannover
- D-30167 Hannover
- Germany
| | - I. Graf
- Department of Chemistry
- Bielefeld University
- D-33615 Bielefeld
- Germany
| | | | - J.-U. Grabow
- Institut für Physikalische Chemie & Elektrochemie
- Gottfried-Wilhelm-Leibniz-University Hannover
- D-30167 Hannover
- Germany
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