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253 results on '"Thomas, Sébastien"'

4. Direct and real-time analysis in a plasma reactor using a compact FTICR/MS: degradation of acetone in nitrogen and by-products formation

Author

Thomas, Sébastien, Blin-Simiand, Nicole, Heninger, Michel, Jeanney, Pascal, Lemaire, Joël, Magne, Lionel, Mestdagh, Helene, Pasquiers, Stephane, and Louarn, Essyllt

Subjects
Physics - Chemical Physics, Physics - Instrumentation and Detectors, Physics - Plasma Physics
Abstract

Methods for reduction of Volatile Organic Compounds (VOCs) content in air depend on the 10 application considered. For low concentration and low flux, non-thermal plasma methods are often considered as efficient. However, the complex chemistry involved is still not well understood as there is a lack of datasets of byproducts formation. So as to overcome this issue, rapid analytical methods are needed. We present the coupling of a rapid chemical ionization mass spectrometer (CIMS) for the real-time analysis of the VOCs formed during a degradation experiment. The high resolution instrument used 15 allows for chemical ionization and direct quantification of non-targeted compounds. We present degradation experiments of acetone in a photo-triggered nitrogen plasma discharge. Two regimes were highlighted: efficient conversion at low concentrations (<100ppm) and moderate efficiency conversion at higher concentrations (>100ppm). Those two regimes were clearly delimited as the sum of two exponential curves occuring at respectively low and high concentrations. Many by-products were detected, in 20 particular HCN presented a significantly high yield. Nitrile compounds (acetonitrile, propionitrile,...) are formed as well. To a lower extent, ketene, acetaldehyde and formaldehyde are observed. The association of the high resolution mass spectrometer to the plasma reactor will allow further insights into the plasma chemistry and comparison to modelisation.

Published
2020

15. Development of an Improved Kinetic Model for CO 2 Hydrogenation to Methanol.

Author

Mbatha, Siphesihle, Thomas, Sébastien, Parkhomenko, Ksenia, Roger, Anne-Cécile, Louis, Benoit, Cui, Xiaoti, Everson, Ray, Langmi, Henrietta, Musyoka, Nicholas, and Ren, Jianwei

Subjects
*CARBON dioxide, *FIXED bed reactors, *CATALYST testing, *METHANOL, *METHANOL as fuel, *CATALYST synthesis
Abstract

The kinetics of methanol synthesis remains debatable for various reasons, such as the lack of scientifically conclusive agreement about reaction mechanisms. The focus of this paper is on the evaluation of the intrinsic kinetics of the methanol synthesis reaction based on CO2 hydrogenation and the associated reverse water–gas shift as overall reactions. The industrial methanol synthesis catalyst, Cu/ZnO/Al2O3/MgO, was used for performing the kinetic studies. An optimal kinetic model was assessed for its ability to predict the experimental data from differential to integral conditions, contrary to the typical fitting of only the integral conditions' data (common practice, as reported in the literature). The catalyst testing and kinetic evaluations were performed at various temperatures (210–260 °C) and pressures (40–77 bar), and for different stoichiometric numbers (0.9–1.9), H2/CO2 ratios (3.0–4.4) and carbon oxide ratios (0.9–1.0), in an isothermal fixed bed reactor, operated in a plug-flow mode. Experiments with CO in the feed were also generated and fitted. Different literature kinetic models with different assumptions on active sites, rate-determining steps, and hence, model formulations were fitted and compared. The original Seidel model appeared to fit the kinetic data very well, but it has twelve parameters. The modified model (MOD) we propose is derived from this Seidel model, but it has fewer (nine) parameters—it excludes CO hydrogenation, but it takes into consideration the morphological changes of active sites and CO adsorption. This MOD model, with three active sites, gave the best fit to all the data sets. [ABSTRACT FROM AUTHOR]

Published
2023
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26. Insights into non-thermal plasma chemistry of acetone diluted in N2/O2 mixtures: a real-time MS experiment

Author

Thomas, Sébastien, Blin-Simiand, Nicole, Héninger, Michel, Jeanney, Pascal, Lemaire, Joel, Magne, Lionel, Mestdagh, Hélène, Pasquiers, Stéphane, Louarn, Essyllt, and Louarn, Essyllt

Subjects
chemical ionization, [CHIM.THEO] Chemical Sciences/Theoretical and/or physical chemistry, [CHIM.ANAL] Chemical Sciences/Analytical chemistry, plasma chemistry, real-time analysis, [PHYS.PHYS.PHYS-PLASM-PH] Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph], Non-thermal plasma, photo-triggered discharge, acetone
Published
2022

41. Insights into non-thermal plasma chemistry of acetone diluted in N2/O2 mixtures: a real-time MS experiment.

Author

Thomas, Sébastien, Blin-Simiand, Nicole, Héninger, Michel, Jeanney, Pascal, Lemaire, Joel, Magne, Lionel, Mestdagh, Hélεave;ne, Pasquiers, Stéphane, and Louarn, Essyllt

Abstract

Understanding non-thermal plasma reactivity is a complicated task as many reactions take place due to a large energy spectrum. In this work, we used a well-defined photo-triggered non-filamentous discharge to study acetone decomposition in N2/O2 gas mixtures. The plasma reactor is associated to a compact chemical ionization FTICR mass spectrometer (BTrap) in order to identify and quantify in real-time acetone and by-products in the plasma. Presence of oxygen (1 to 5%) decreased notably acetone degradation. A tremendous change is observed in the by-products distribution concomitantly to a global decrease of their total concentration. While main products observed in oxygen-free gas mix are nitrile compounds, in oxygenated media they are replaced by formaldehyde, methanol and ketene. Methanol is maximum for 1% of O2 whereas formaldehyde and ketene concentration reach their maximum value at the highest oxygen concentration tested (5%). A number of nitrate, nitrite and isocyanate organic compounds (C1 and C2) are observed as well with HNO2, HNO3 and HNCO. [ABSTRACT FROM AUTHOR]

Published
2022
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46. Statistical molecular fragmentation: which parameters influence the branching ratios?

Author

Désesquelles, Pierre, Pasquiers, Stéphane, Blin-Simiand, Nicole, Magne, Lionel, Van-Oanh, Nguyen-Thi, Thomas, Sébastien, Domin, Dominik, Laboratoire de physique des gaz et des plasmas (LPGP), Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Chimie Physique D'Orsay (LCPO), Université Paris-Sud - Paris 11 (UP11)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Institut de Chimie Physique (ICP), Institut de Chimie du CNRS (INC)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Institut de Chimie de la Matière Condensée de Bordeaux (ICMCB), and Université de Bordeaux (UB)-Institut Polytechnique de Bordeaux-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)

Subjects
010304 chemical physics, Chemistry, Radical, Mathematics::History and Overview, Ab initio, General Physics and Astronomy, Statistical model, 010402 general chemistry, Branching (polymer chemistry), 01 natural sciences, 0104 chemical sciences, chemistry.chemical_compound, Fragmentation (mass spectrometry), Chemical physics, Propane, [PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph], 0103 physical sciences, Physics::Atomic and Molecular Clusters, Molecule, Physical and Theoretical Chemistry, Physics::Chemical Physics
Abstract

The fragmentation of molecules under conditions that result in yields of products that are thermodynamically controlled can be readily studied with statistical models. We explore which parameters influence the branching ratios using our recently developed Statistical Molecular Fragmentation model (SMF) and apply it to the decomposition of propane. We find that the fragmentation process has low sensitivity to the differences between the molecular descriptions given by commonly used ab initio methods (B3LYP, CCSD(T) and composite methods with different atom-centered basis sets). However, the branching ratios are most influenced by the vibrational frequencies of the molecules and radicals present in the decomposition pathways.

Published
2019

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