Caractérisation d'intermédiaires de combustion, de polluants et de produits hautement oxygénés par chromatographie liquide et spectrométrie de masse Orbitrap pour la compréhension des mécanismes réactionnels d'oxydation de biocarburants

Since several decades, ecological transitions and sustainable development have been of great interest of global organizations. Thus, the exploitation lignocellulosic biomass aiming at decreasing the dependence on fossil resources and reducing greenhouse gas emissions, open the field of application in the energy sector, in particular the production of potential biofuels (e.g., diethyl ether, dibutyl ether, tetrahydrofuran, n-pentane, n-hexane). Because they have various chemical structures, their combustion and the mechanisms of formation of their oxidation intermediates are of interest to researchers. Several experimental devices (jet-stirred reactor, motored engine, rapid compression machine) have been used to oxidize biofuels under the cool flame regime. The development of a chromatographic method by coupling liquid chromatography and high-resolution massspectrometry allowed the characterization of oxidation intermediates little studied before (hydroperoxides, ketohydroperoxides and highly oxygenated molecules). The profiles of the oxidation products formed in a jetstirred reactor were compared to predictions of kinetic models found in the literature. In addition, comparison of the chemical species formed in the three experimental systems showed strong similarity, despite their different physical properties.Depuis plusieurs décennies, la transition écologique et le développement durable sont au cœur des préoccupations des organisations mondiales. Ainsi, l’exploitation et la valorisation de la biomasse lignocellulosique, visant à diminuer la dépendance aux ressources fossiles et à réduire les émissions de gaz à effet de serre, voient leur importance grandirent. Dans le domaine énergétique, la production de potentiels biocarburants (ex. éther diéthylique, éther dibutylique, tétrahydrofurane, n-pentane, n-hexane) est particulièrement importante. Ces derniers pouvant se présenter sous diverses structures chimiques, leur combustion et mécanismes de formation de leurs intermédiaires d’oxydation suscitent l’intérêt des chercheurs. Plusieurs dispositifs expérimentaux (réacteur auto-agité, moteur à combustion interne, machine à compression rapide) ont été utilisés pour oxyder des biocarburants dans la zone de flamme froide. Le développement d’une méthode chromatographique par couplage de la chromatographie en phase liquide et de la spectrométrie de masse haute résolution ont permis de caractériser des intermédiaires d’oxydation peuétudiés auparavant (hydroperoxydes, cétohydroperoxydes et molécules hautement oxygénées). Les profils des produits d’oxydation formés dans le réacteur auto-agité ont été comparés aux résultats de simulations utilisant des modèles cinétiques issus de la littérature. De plus, la comparaison entre les espèces chimiques formées dans les trois systèmes expérimentaux a démontré une similitude entre les processus chimiques de combustion dans chacun des systèmes, et ce malgré leurs différentes caractéristiques physiques

Towards a Comprehensive Characterization of the Low-Temperature Autoxidation of Di-n-Butyl Ether

In the present study, we investigated the oxidation of 2500 ppm of di-n-butyl ether under fuel-rich conditions (φ = 2) at low temperatures (460–780 K), a residence time of 1 s, and 10 atm. The experiments were carried out in a fused silica jet-stirred reactor. Oxidation products were identified and quantified in gas samples by gas chromatography and Fourier transform infrared spectrometry. Samples were also trapped through bubbling in cool acetonitrile for high-pressure liquid chromatography (HPLC) analyses. 2,4-dinitro-phenylhydrazine was used to derivatize carbonyl products and distinguish them from other isomers. HPLC coupled to high resolution mass spectrometry (Orbitrap Q-Exactive®) allowed for the detection of oxygenated species never observed before, i.e., low-temperature oxidation products (C8H12O4,6, C8H16O3,5,7, and C8H18O2,5) and species that are more specific products of atmospheric oxidation, i.e., C16H34O4, C11H24O3, C11H22O3, and C10H22O3. Flow injection analyses indicated the presence of high molecular weight oxygenated products (m/z > 550). These results highlight the strong similitude in terms of classes of oxidation products of combustion and atmospheric oxidation, and through autoxidation processes. A kinetic modeling of the present experiments indicated some discrepancies with the present data

Characterization of combustion intermediates, pollutants and highly oxygenated products by liquid chromatography and mass spectrometry Orbitrap for the understanding of biofuel oxidation pathways

Depuis plusieurs décennies, la transition écologique et le développement durable sont au cœur des préoccupations des organisations mondiales. Ainsi, l'exploitation et la valorisation de la biomasse lignocellulosique, visant à diminuer la dépendance aux ressources fossiles et à réduire les émissions de gaz à effet de serre, voient leur importance grandirent. Dans le domaine énergétique, la production de potentiels biocarburants (ex. éther diéthylique, éther dibutylique, tétrahydrofurane, n-pentane, n-hexane) est particulièrement importante. Ces derniers pouvant se présenter sous diverses structures chimiques, leur combustion et mécanismes de formation de leurs intermédiaires d'oxydation suscitent l'intérêt des chercheurs. Plusieurs dispositifs expérimentaux (réacteur auto-agité, moteur à combustion interne, machine à compression rapide) ont été utilisés pour oxyder des biocarburants dans la zone de flamme froide. Le développement d'une méthode chromatographique par couplage de la chromatographie en phase liquide et de la spectrométrie de masse haute résolution ont permis de caractériser des intermédiaires d'oxydation peu étudiés auparavant (hydroperoxydes, cétohydroperoxydes et molécules hautement oxygénées). Les profils des produits d'oxydation formés dans le réacteur auto-agité ont été comparés aux résultats de simulations utilisant des modèles cinétiques issus de la littérature. De plus, la comparaison entre les espèces chimiques formées dans les trois systèmes expérimentaux a démontré une similitude entre les processus chimiques de combustion dans chacun des systèmes, et ce malgré leurs différentes caractéristiques physiques.Since several decades, ecological transitions and sustainable development have been of great interest of global organizations. Thus, the exploitation lignocellulosic biomass aiming at decreasing the dependence on fossil resources and reducing greenhouse gas emissions, open the field of application in the energy sector, in particular the production of potential biofuels (e.g., diethyl ether, dibutyl ether, tetrahydrofuran, n-pentane, n-hexane). Because they have various chemical structures, their combustion and the mechanisms of formation of their oxidation intermediates are of interest to researchers. Several experimental devices (jet-stirred reactor, motored engine, rapid compression machine) have been used to oxidize biofuels under the cool flame regime. The development of a chromatographic method by coupling liquid chromatography and high-resolution mass spectrometry allowed the characterization of oxidation intermediates little studied before (hydroperoxides, ketohydroperoxides and highly oxygenated molecules). The profiles of the oxidation products formed in a jet-stirred reactor were compared to predictions of kinetic models found in the literature. In addition, comparison of the chemical species formed in the three experimental systems showed strong similarity, despite their different physical properties

On the similarities and differences between the products of oxidation of hydrocarbons under simulated atmospheric conditions and cool flames

International audienceAbstract. Atmospheric oxidation chemistry and, more specifically, photooxidation show that the long-term oxidation of organic aerosol (OA) progressively erases the initial signature of the chemical compounds and can lead to a relatively uniform character of oxygenated organic aerosol (OOA). This uniformity character observed after a long reaction time seems to contrast with the great diversity of reaction mechanisms observed in the early stages of oxidation. The numerous studies carried out on the oxidation of terpenes, and more particularly on limonene for its diversity of reaction sites (endo- and oxocyclic), allow this evolution to be studied. We have selected, for their diversity of experimental conditions, nine studies of limonene oxidation at room temperature over long reaction times to be compared to the present data set obtained at elevated temperature and short reaction time in order to investigate the similarities in terms of reaction mechanisms and chemical species formed. Here, the oxidation of limonene–oxygen–nitrogen mixtures was studied using a jet-stirred reactor at elevated temperature and atmospheric pressure. Samples of the reacting mixtures were collected and analyzed by high-resolution mass spectrometry (Orbitrap) after direct injection or after separation by reverse-phase ultra-high-pressure liquid chromatography and soft ionization, i.e., (+/-) HESI and (+/-) APCI. Unexpectedly, because of the diversity of experimental conditions in terms of continuous-flow tank reactor, concentration of reactants, temperature, reaction time, mass spectrometry techniques, and analysis conditions, the results indicate that among the 1138 presently detected molecular formulae, many oxygenates found in earlier studies of limonene oxidation by OH and/or ozone are also produced under the present conditions. Among these molecular formulae, highly oxygenated molecules and oligomers were detected in the present work. The results are discussed in terms of reaction pathways involving the initial formation of peroxy radicals (RO2), isomerization reactions yielding keto-hydroperoxides, and other oxygenated intermediates and products up to C25H32O17, products which could derive from RO2 autoxidation via sequential H shift and O2 addition (C10H14O3,5,7,9,11) and products deriving from the oxidation of alkoxy radicals (produced by RO2 self-reaction or reaction with HO2) through multiple H shifts and O2 additions (C10H14O2,4,6,8,10). The oxidation of RO2, with possible occurrence of the Waddington mechanism and of the Korcek mechanism, involving H shifts is also discussed. The present work demonstrates similitude between the oxidation products and oxidation pathways of limonene under simulated atmospheric conditions and in those encountered during the self-ignition of hydrocarbons at elevated temperatures. These results complement those recently reported by Vereecken and Nozière and confirm for limonene the existence of an oxidative chemistry of the alkylperoxy radical beyond 450 K based on the H shift (Nozière and Vereecken, 2019; Vereecken and Nozière, 2020)

Towards a Comprehensive Characterization of the Low-Temperature Autoxidation of Di-n-Butyl Ether

International audienceIn the present study, we investigated the oxidation of 2500 ppm of di-n-butyl ether under fuel-rich conditions (φ = 2) at low temperatures (460–780 K), a residence time of 1 s, and 10 atm. The experiments were carried out in a fused silica jet-stirred reactor. Oxidation products were identified and quantified in gas samples by gas chromatography and Fourier transform infrared spectrometry. Samples were also trapped through bubbling in cool acetonitrile for high-pressure liquid chromatography (HPLC) analyses. 2,4-dinitro-phenylhydrazine was used to derivatize carbonyl products and distinguish them from other isomers. HPLC coupled to high resolution mass spectrometry (Orbitrap Q-Exactive®) allowed for the detection of oxygenated species never observed before, i.e., low-temperature oxidation products (C8H12O4,6, C8H16O3,5,7, and C8H18O2,5) and species that are more specific products of atmospheric oxidation, i.e., C16H34O4, C11H24O3, C11H22O3, and C10H22O3. Flow injection analyses indicated the presence of high molecular weight oxygenated products (m/z > 550). These results highlight the strong similitude in terms of classes of oxidation products of combustion and atmospheric oxidation, and through autoxidation processes. A kinetic modeling of the present experiments indicated some discrepancies with the present data

On the formation of highly oxidized pollutants by autoxidation of terpenes under low-temperature-combustion conditions: the case of limonene and α -pinene

International audienceThe oxidation of monoterpenes under atmospheric conditions has been the subject of numerous studies. They were motivated by the formation of oxidized organic molecules (OOMs), which, due to their low vapor pressure, contribute to the formation of secondary organic aerosols (SOA). Among the different reaction mechanisms proposed for the formation of these oxidized chemical compounds, it appears that the autoxidation mechanism, involving successive events of O2 addition and H migration, common to both low-temperature-combustion and atmospheric conditions, leads to the formation of highly oxidized products (HOPs). However, cool-flame oxidation (∼500–800 K) of terpenes has not received much attention even if it can contribute to atmospheric pollution through biomass burning and wildfires. Under such conditions, terpenes can be oxidized via autoxidation. In the present work, we performed oxidation experiments with limonene–oxygen–nitrogen and α-pinene–oxygen–nitrogen mixtures in a jet-stirred reactor (JSR) at 590 K, a residence time of 2 s, and atmospheric pressure. Oxidation products were analyzed by liquid chromatography, flow injection, and soft-ionization–high resolution mass spectrometry. H–D exchange and 2,4-dinitrophenyl hydrazine derivatization were used to assess the presence of OOH and C=O groups in oxidation products, respectively. We probed the effects of the type of ionization used in mass spectrometry analyses on the detection of oxidation products. Heated electrospray ionization (HESI) and atmospheric-pressure chemical ionization (APCI) in positive and negative modes were used. We built an experimental database consisting of literature data for atmospheric oxidation and presently obtained combustion data for the oxidation of the two selected terpenes. This work showed a surprisingly similar set of oxidation products' chemical formulas, including oligomers, formed under the two rather different conditions, i.e., cool-flame and simulated atmospheric oxidation. Data analysis (in HESI mode) indicated that a subset of chemical formulas is common to all experiments, independently of experimental conditions. Finally, this study indicates that more than 45 % of the detected chemical formulas in this full dataset can be ascribed to an autoxidation reaction

On the autoxidation of terpenes: Detection of oxygenated and aromatic products

International audienceLimonene-O 2-N 2 and α-pinene-O 2-N 2 mixtures were oxidized in a jet-stirred reactor at atmospheric pressure, in the cool flame regime, and fuel-lean conditions. Samples of the reacting mixtures were analyzed by on-line Fourier transform infrared (FTIR) and collected, dissolved in acetonitrile for analysis by flow injection or chromatographic separation by ultra-high performance liquid chromatography and Orbitrap mass spectrometry. OH/OD exchange using D 2 O and reaction with 2,4dinitrophenylhydrazine were carried out for probing the existence of hydroxyl or hydroperoxyl, and carbonyl functions in the products, respectively. A large number of oxidation products, including highly oxygenated organic products with more than ten oxygen atoms, were observed. Unexpectedly, aromatic and polyunsaturated products with a contribution of 8-10% were detected for both terpenes over the range of temperatures studied. Van Krevelen plots, computed oxidation state of carbon, aromaticity index, and aromaticity equivalent index in products were used to rationalize the results

Characterization of the Autoxidation of Terpenes at Elevated Temperature Using High-Resolution Mass Spectrometry: Formation of Ketohydroperoxides and Highly Oxidized Products from Limonene

International audienceLow-temperature experiments on the oxidation of limonene-O2-N2 mixtures were conducted in a jet-stirred reactor (JSR) over a range of temperatures (520 to 800 K), fuel-lean conditions (equivalence ratio φ = 0.5), short residence time (1.5 s) and a pressure of 1 bar. Collected samples of the reacting mixtures were analyzed by (i) on-line Fourier transform infrared spectroscopy (FTIR) and (ii) Orbitrap Q-Exactive® high resolution mass spectrometry after direct injection or chromatographic separation using reversed-phase ultra-high-performance liquid chromatography (RP-UHPLC) and soft ionization (+/‒ heated electrospray ionization and +/‒ atmospheric pressure chemical ionization). H/D exchange using deuterated water (D2O) and reaction with 2,4-dinitrophenylhydrazine (2,4-DNPH) were performed to probe the presence of OH, OOH and C=O groups in the oxidized products, respectively. A broad range of oxidation products ranging from water to highly oxygenated products, containing five and more O-atoms, was detected (C7H10O4,5, C8H12O2,4, C8H14O2,4, C9H12O, C9H14O1,3-5, C10H12O2, C10H14O1-9, C10H16O2-5, and C10H18O6). Mass spectrometry analyzes were only qualitative whereas quantification was performed with FTIR. The results are discussed in terms of reaction routes involving the initial formation of peroxy radicals, H-atom transfer and O2 addition sequences producing a large set of chemical products among which ketohydroperoxides and more oxygenated products. Carbonyl compounds deriving from the Waddington oxidation mechanism on exo- and endo-double bonds (C=C) were observed as well as their products of further oxidation. Products of the Korcek mechanism (carboxylic acids and carbonyls) were also detected

Histo-Epidemiological Profile of Endometrial Cancer in the Oran Region

Objective: The aim of the present study is to describe the epidemiological, histopathological and therapeutic profile of endometrial cancers in the region of Oran. Methods: We conducted a retrospective study by exploring the medical files of 25 female patients diagnosed of endometrial cancer and treated at the level of the EHU November 1, 1954’s medical oncology department in Oran during the period from January 2015 to December 2019. For data collection, we used a structured exploitation sheet to obtain necessary information. Variables were analyzed using SPSS Software Version 20.0. Results: The median age of patients was 59 years with extremes ranging from 42 to 83 years. More than 56% of our patients were over 50 years old, 40% of the patients were nulliparous and 80% postmenopausal. The average age of menarche was 14.09 ± 1.44 years with extremes ranging from 12 to 17 years. The indication for anatomopathological examination was dominated by metrorrhagia (80%). Histopathologically, endometrioid adenocarcinoma was the most common at 75% of cases. We also note that 62.5% were classified in stage I and 37.5% in stage II. Myometrium infiltration was observed in 66.67% of cases. The basic treatment for endometrial cancer remains surgical. Conclusion: At the end of this work, we concluded that this pathology remains essentially that of postmenopausal women. Endometrioid adenocarcinoma was the most common histologic type. This study also revealed many risk factors for endometrial cancer, such as advanced age, hypertension and nulliparity. Keywords: Cancer, Endometrium, Epidemiology, Anathomopathology, Risk factor

Abstracts of 1st International Conference on Computational & Applied Physics

This book contains the abstracts of the papers presented at the International Conference on Computational & Applied Physics (ICCAP’2021) Organized by the Surfaces, Interfaces and Thin Films Laboratory (LASICOM), Department of Physics, Faculty of Science, University Saad Dahleb Blida 1, Algeria, held on 26–28 September 2021. The Conference had a variety of Plenary Lectures, Oral sessions, and E-Poster Presentations. Conference Title: 1st International Conference on Computational & Applied PhysicsConference Acronym: ICCAP’2021Conference Date: 26–28 September 2021Conference Location: Online (Virtual Conference)Conference Organizer: Surfaces, Interfaces, and Thin Films Laboratory (LASICOM), Department of Physics, Faculty of Science, University Saad Dahleb Blida 1, Algeria