Towards a high-accuracy kinetic database informed by theoretical and experimental data: CH3 + HO2 as a case study

Barbet, Mark C.; Lei, Lei; Burke, Michael P.

doi:10.1016/j.proci.2020.06.324

Cited by 10 publications

(5 citation statements)

References 39 publications

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“…A general theme of the present work (consistent with similar analyses 23,24,42,56 for other reactions) is that apparent inconsistencies among theoretically calculated and experimentally derived rate constants can often be resolved when the constraints imposed by ab initio electronic structure calculations and measured macroscopic observables are considered simultaneously within multiscale, physics-based frameworks for data analysis. We therefore recommend that future experimental studies report raw data (e.g., measured time profiles) and future theoretical studies provide theoretical kinetics input files (e.g., for Variflex or MESS) in addition to derived rate constants�in order to enable rigorous comparisons of theory and experiment in a manner that better reflects the information content and associated uncertainties in each.…”

Section: ■ Conclusionsupporting

confidence: 59%

“…For B2 in R1, for which the torsional dependence of the harmonic frequencies was considered, the same harmonic frequency scaling factor was applied to all frequencies at all torsional angles. For R6, whose rate constant was sufficiently constrained by macroscopic observables over the relevant temperature ranges, Arrhenius parameters were simply treated as active parameters (similar to our earlier work , ).…”

Section: Methodsmentioning

confidence: 99%

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Resolving Discrepancies between State-of-the-Art Theory and Experiment for HO₂ + HO₂ via Multiscale Informatics

et al. 2023

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Recent high-level theoretical calculations predict a mild temperature dependence for HO 2 + HO 2 inconsistent with state-of-the-art experimental determinations that upheld the stronger temperature dependence observed in early experiments. Via MultiScale Informatics analysis of the theoretical and experimental data, we identified an alternative interpretation of the raw experimental data that uses HO 2 + HO 2 rate constants nearly identical to theoretical predictions�implying that the theoretical and experimental data are actually consistent, at least when considering the raw data from experimental studies. Similar analyses of typical signals from low-temperature experiments indicate that an HOOOOH intermediate�identified by recent theory but absent from earlier interpretations�yields modest effects that are smaller than, but may have contributed to, the scatter in data among different experiments. More generally, the findings demonstrate that modern chemical theories and experiments have progressed to a point where meaningful comparison requires joint consideration of their data simultaneously.

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Section: ■ Conclusionsupporting

confidence: 59%

Section: Methodsmentioning

confidence: 99%

Resolving Discrepancies between State-of-the-Art Theory and Experiment for HO₂ + HO₂ via Multiscale Informatics

et al. 2023

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“…As indicated in Figure 5, the other influential reactions in model predictions at the present conditions are often among the most important reactions to predictions of other nitrogen kinetics systems, and their kinetic sensitivity coefficients (and rankings) depend on the values of the rate constants themselvessuch that unraveling remaining discrepancies may require simultaneous consideration of the other nitrogen kinetics validation data as well as nonlinearities in the sensitivity coefficients to kinetic parameters. In that regard, we anticipate that our future planned studies applying our MultiScale Informatics approach 47,67,68 to previous experimental and theoretical data for nitrogen kinetics may be useful in unraveling the remaining discrepancies.…”

Section: + ⇔ +mentioning

confidence: 99%

Toward a More Comprehensive Understanding of the Kinetics of a Common Biomass-Derived Impurity: NH₃ Oxidation by N₂O in a Jet-Stirred Reactor

2021

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Ammonia (NH 3 ) has garnered substantial attention in recent years due to its importance across many scientific and engineering domainsincluding its potential use as a carbon-free fuel and long-term energy storage option, its use in reducing combustion-generated nitrogen oxide emissions, its role as a decomposition fragment of many energetic materials, and its presence as an important impurity during biofuel and biomass combustion that can affect overall system kinetics, among others. Yet, it is generally recognized that there are still significant gaps in the present understanding of ammonia kineticsin both experimental data sets and submodels within the overall ammonia kinetic mechanism. For example, most experimental studies of ammonia oxidation have used molecular oxygen as the primary or sole oxidizer. While large mole fractions of molecular oxygen are encountered in many combustion scenarios, there are select systems where ammonia is more likely to be oxidized via nitrogen-containing species (e.g., N 2 O), and, more generally, there are relatively untested reaction sets that would be accentuated in such conditions. To address one such gap in experimental data sets for the validation of ammonia kinetics submodels, we present results from jet-stirred reactor experiments of an NH 3 /N 2 O/N 2 mixture over an intermediate temperature range (850−1180 K). In these experiments, the mole fractions of NH 3 , N 2 O, and NO are measured through a combination of gas chromatography, chemiluminescence, electrochemical detection, and infrared absorptionwhere agreement among the different diagnostics (within 3% for N 2 O and 7% for NO) ensures high confidence in the experimental measurements. Comparison of the experimental results and model predictions suggests deficiencies in commonly used models for nitrogen kinetics. Various modeling analyses point to the central role of the N 2 O + NH 2 = N 2 H 2 + NO reaction, on which recent kinetic models all rely on the same rate constant estimate that appears to have not been tested in previous validation data sets for NH 3 kinetics.

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“…62 Furthermore, it has been reported that the increasing use of LNG (mostly methane) in stoichiometric-combustion heavy-duty engines equipped with a three-way catalyst can have undesired effects on NH 3 and N 2 O emissions, depending on reaction temperature, CH 4 and NO exhaust concentrations, and further exhaust gas composition, as well as the aging status of the catalyst. 392 Not only natural gas combustion will profit from new insights into the chemistry of methane oxidation under different conditions, reaching from more accurate thermodynamics and kinetics for key species and their reactions, especially for important pressure-dependent and/or radical−radical reactions 393 to process details under practically relevant conditions including efficiency, pollutant formation, and exhaust aftertreatment. 62,363,364,385 Accurate, predictive, well-validated submodels for methane are of importance in foundational models for hydrocarbon combustion in general.…”

Section: Chemicalmentioning

confidence: 99%

“…Not only natural gas combustion will profit from new insights into the chemistry of methane oxidation under different conditions, reaching from more accurate thermodynamics and kinetics for key species and their reactions, especially for important pressure-dependent and/or radical–radical reactions to process details under practically relevant conditions including efficiency, pollutant formation, and exhaust aftertreatment. ,,, Accurate, predictive, well-validated submodels for methane are of importance in foundational models for hydrocarbon combustion in general . They are also valuable for future dual-fuel strategies using methane in blends, e.g., with ammonia, with reaction schemes like those discussed above as part of the fuel conversion and NO x formation.…”

Section: Fuels For a Carbon-reduced Perspectivementioning

confidence: 99%

Combustion, Chemistry, and Carbon Neutrality

Kohse‐Höinghaus

2023

Chem. Rev.

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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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Towards a high-accuracy kinetic database informed by theoretical and experimental data: CH3 + HO2 as a case study

Cited by 10 publications

References 39 publications

Resolving Discrepancies between State-of-the-Art Theory and Experiment for HO₂ + HO₂ via Multiscale Informatics

Resolving Discrepancies between State-of-the-Art Theory and Experiment for HO₂ + HO₂ via Multiscale Informatics

Toward a More Comprehensive Understanding of the Kinetics of a Common Biomass-Derived Impurity: NH₃ Oxidation by N₂O in a Jet-Stirred Reactor

Combustion, Chemistry, and Carbon Neutrality

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Towards a high-accuracy kinetic database informed by theoretical and experimental data: CH3 + HO2 as a case study

Cited by 10 publications

References 39 publications

Resolving Discrepancies between State-of-the-Art Theory and Experiment for HO2 + HO2 via Multiscale Informatics

Resolving Discrepancies between State-of-the-Art Theory and Experiment for HO2 + HO2 via Multiscale Informatics

Toward a More Comprehensive Understanding of the Kinetics of a Common Biomass-Derived Impurity: NH3 Oxidation by N2O in a Jet-Stirred Reactor

Combustion, Chemistry, and Carbon Neutrality

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Resources

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Resolving Discrepancies between State-of-the-Art Theory and Experiment for HO₂ + HO₂ via Multiscale Informatics

Resolving Discrepancies between State-of-the-Art Theory and Experiment for HO₂ + HO₂ via Multiscale Informatics

Toward a More Comprehensive Understanding of the Kinetics of a Common Biomass-Derived Impurity: NH₃ Oxidation by N₂O in a Jet-Stirred Reactor