Fuel-rich methane oxidation in a high-pressure flow reactor studied by optical-fiber laser-induced fluorescence, multi-species sampling profile measurements and detailed kinetic simulations

Schwarz, Heiner; Geske, Michael; Goldsmith, C. Franklin; Schlögl, Robert; Horn, Raimund

doi:10.1016/j.combustflame.2014.01.007

Cited by 22 publications

(20 citation statements)

References 37 publications

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“…The reduced C 2 -product formation can also be explained by the higher abundance of oxygen in the gas phase. Assuming the widely accepted mechanism involving methyl radicals being released to the gas phase and combining to ethane, the collision of the radicals with oxygen becomes more likely in an oxygen-rich atmosphere, favoring the unselective gas-phase reactions leading to CO and CO 2 …”

Section: Resultsmentioning

confidence: 99%

Oxygen Activation in Oxidative Coupling of Methane on Calcium Oxide

et al. 2018

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A pulsed isotope exchange technique was applied to study the oxygen scrambling activity of polycrystalline calcium oxide under temperatures and pressures relevant for the oxidative coupling of methane (OCM). Oxygen exchange was observed above 400 °C. The onset was attributed to the removal of impurities on the catalyst surface. By trapping impurities in the gas feed, the scrambling could already be observed at room temperature. An activation energy of 80 kJ/mol was determined for the oxygen scrambling of O2 on the surface of polycrystalline CaO powder in absence of other gases. Presence of water and carbon dioxide shift the onset of the reaction to higher temperatures and increase the activation energy significantly to 110 and 150 kJ/mol, respectively. The OCM activity could be directly linked to the oxygen scrambling activity of the material in pulsed OCM operation. It is proposed that the same sites are responsible for oxygen scrambling and OCM reaction and that the rate is dictated by desorption of CO2 and H2O. The high reaction temperatures in OCM in case of CaO are only required to regenerate the active sites, which may apply to basic OCM catalysts in general. In situ Raman and thermogravimetric experiments verified the formation of a bulk calcite phase below 750 °C, which is inactive in OCM and oxygen scrambling. Above 750 °C no surface oxygen species or adsorbates were found by Raman spectroscopy suggesting that only surface defects are responsible for catalytic activity of CaO.

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Section: Resultsmentioning

confidence: 99%

Oxygen Activation in Oxidative Coupling of Methane on Calcium Oxide

et al. 2018

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“…It was also validated against the combustion data of C 0 –C 4 . The model of Schwarz et al ( 55 ) was adapted and reduced from Dooley’s model, 68 which described the oxidation of methyl formate, and compared it against the experimental data of fuel-rich methane oxidation (OCM condition) in a plug flow reactor. In addition to these four models, from strictly gas-phase studies, as discussed above, two other models were selected from homogeneous–heterogeneous networks for methane oxidation in the presence of catalysts.…”

Section: Resultsmentioning

confidence: 99%

Noncatalytic Oxidative Coupling of Methane (OCM): Gas-Phase Reactions in a Jet Stirred Reactor (JSR)

et al. 2021

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Oxidative coupling of methane (OCM) is a promising technique for converting methane to higher hydrocarbons in a single reactor. Catalytic OCM is known to proceed via both gas-phase and surface chemical reactions. It is essential to first implement an accurate gas-phase model and then to further develop comprehensive homogeneous–heterogeneous OCM reaction networks. In this work, OCM gas-phase kinetics using a jet-stirred reactor are studied in the absence of a catalyst and simulated using a 0-D reactor model. Experiments were conducted in OCM-relevant operating conditions under various temperatures, residence times, and inlet CH 4 /O 2 ratios. Simulations of different gas-phase models related to methane oxidation were implemented and compared against the experimental data. Quantities of interest (QoI) and rate of production analyses on hydrocarbon products were also performed to evaluate the models. The gas-phase models taken from catalytic reaction networks could not adequately describe the experimental gas-phase performances. NUIGMech1.1 was selected as the most comprehensive model to describe the OCM gas-phase kinetics; it is recommended for further use as the gas-phase model for constructing homogeneous–heterogeneous reaction networks.

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“…and the secondary reactions of CH 3 . play key roles in governing the OCM catalyst selectivity . Reasonably, online detection of these reactive intermediates is essential to study the radicals involved reactions pathways.…”

Section: Applications Of Vuv‐pims System In Heterogeneous Catalysismentioning

confidence: 99%

“…It has been long proposed that the activation of methane on OCM catalysts leads to the formation of gasphase methyl radicals (CH 3 * ) and the secondary reactions of CH 3 * play key roles in governing the OCM catalyst selectivity. [75][76][77] Reasonably, online detection of these reactive intermediates is essential to study the radicals involved reactions pathways.…”

Section: Methane Conversionmentioning

confidence: 99%

Photoionization Mass Spectrometry for Online Detection of Reactive and Unstable Gas‐Phase Intermediates in Heterogeneous Catalytic Reactions

You

Huang

2019

ChemCatChem

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Heterogeneous catalytic reactions always involve surface intermediates on catalyst surfaces, and some of them also involve reactive and unstable gas-phase intermediates such as radicals and alkyl hydroperoxides. Online detection of these gas-phase intermediates is of great importance for fundamentally understanding reaction mechanisms of relevant heterogeneous catalytic reactions, designing structures of efficient catalysts and optimizing reactors. However, it has remained a long-time challenge due to the lack of routine characterization techniques. Herein we review recent progress on applications of photoionization mass spectrometry in online detection of reactive and unstable gas-phase intermediates in heterogeneous catalytic reactions. The development and advantages of photoionization mass spectrometry and the relevant equipment setup for heterogeneous catalysis studies are also described. Finally, a future perspective is given.[a] Dr. * (m/z = 15), C 2 H 5 * (m/z = 29) and allyl radical (CH 2 CHCH 2 * 4 5 6 7 8

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Fuel-rich methane oxidation in a high-pressure flow reactor studied by optical-fiber laser-induced fluorescence, multi-species sampling profile measurements and detailed kinetic simulations

Cited by 22 publications

References 37 publications

Oxygen Activation in Oxidative Coupling of Methane on Calcium Oxide

Oxygen Activation in Oxidative Coupling of Methane on Calcium Oxide

Noncatalytic Oxidative Coupling of Methane (OCM): Gas-Phase Reactions in a Jet Stirred Reactor (JSR)

Photoionization Mass Spectrometry for Online Detection of Reactive and Unstable Gas‐Phase Intermediates in Heterogeneous Catalytic Reactions

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