Proposition de stages, thèses et post-docs

Laboratoire de Physicochimie des Processus de Combustion et de l'Atmosphère
PC2A - UMR 8522 CNRS/Lille1
Université Lille 1 Sciences et Technologies
Cité scientifique, Bâtiment C11/C5
59655 Villeneuve d'Ascq Cedex, France

Le Laboratoire de Physicochimie des Processus de Combustion et de l'Atmosphère de l'Université Lille1 Sciences et Technologies cherche des physico-chimistes, chimistes ou physiciens de formation, pour préparer un stage de recherche Master (Année universitaire 2019-2020), une thèse de doctorat (à partir d'Octobre 2020), ou un Post-Doc dans le domaine de l'énergétique et de l'environnement.

Les sujets de recherche proposés concernent les domaines de la combustion, de la sûreté nucléaire et de l'environnement. Ils s'inscrivent dans des axes de recherche soutenus par le Ministère de l'Enseignement Supérieur et de la Recherche, le CNRS-INSIS, l'Institut de Radioprotection et de Sûreté Nucléaire (IRSN) et le Contrat de Projet Etat-Région Hauts de France.

Les candidatures, comportant un CV et une lettre de motivation, doivent être soumises auprès des chercheurs responsables des sujets proposés.

Master 2

Role of the resonantly stabilized radicals in the inception of soot particles

Fossil fuel combustion constitutes the principal source of our energy needs. This combustion is unfortunately also the main source of the air pollution. Among the pollutants emitted by fuel combustion, there are polycyclic aromatic hydrocarbons (PAHs) of which we have a solid conviction that some of them are strongly harmful for health: there are indeed toxicological studies, which show their cancerogenic character. In addition, many studies carried out on the comprehension of the processes involving during PAHs and soot formation, agree on the implication of PAHs as precursors of soot particles. Soot particles are also very harmful for human being, more particularly the small particle sizes, which have a strong capacity of penetration in the lungs.

 

This training course lies within the scope of the continuation of the development and the validation of a detailed kinetic mechanism of hydrocarbon oxidation under rich fuel conditions producing soot particles. It aims to identify the impact of the resonantly stabilized radicals in the formation of the first aromatic rings. A particular attention will be paid to small PAHs (up 4-5 rings) as pyrene and its isomers, which are considered as direct precursors of nucleation soot process. It is expected to carry out quantum chemistry calculations by using chemical tools as Gaussian16. This work should confirm/cancel certain literature thermokinetic data, or to generate new data.

 

Keywords: PAHs, soot, combustion, detailed kinetic reaction mechanism, Flames, Quantum Calculations.

Linked to the workpackage of the Labex CaPPA : WP2

Supervisor(s): Abderrahman El Bakali / Sonia Taamalli

 

Optical properties of aerosols measured in the Optical properties of aerosols measured in the IR and UV range

Because of their ability to absorb and to scatter radiations, airborne particles play an important role in the energy budget of the earth-atmosphere system. It is assumed that aerosols are one of the atmospheric constituents participating to the cooling effect, but estimates are highly uncertain owing to the large spatial and temporal variability of aerosol concentration and physical properties.

The measurements from space-borne instruments are the only means for observing aerosol distributions from local to global scale. However, to fully exploit the instruments capabilities it is essential to have reference optical properties of various particles and mainly their complex refractive indices.

The aim of this work is to measure transmittance spectra of model airborne particles in the infrared and the UV-vis spectral region using a dedicated experimental setup developed in PC2A. The extinction spectra of the aerosol are measured by Fourier Transform InfraRed (FTIR) spectrometer and UV-vis spectrometer and the corresponding size distributions are recorded using optical counters. The whole methodology has been validated using model silica particles and volcanic ashes. The team wants to extend this methodology to other particles of atmospheric interest, e.g. water droplets containing bioaerosols or silica particles with water adsorbed on their surface. Reactivity with OH radicals will be also considered in order to estimate the role of atmospheric aging on the optical properties of the aerosols. Thus the objective of the internship is to transform the set-up in order to generate such particles and to measure their optical properties in parallel with chemical composition and some physical properties such as the size and the concentration of the particles. The experimental data are then processed in order to retrieve the complex refractive indexes of these aerosols (collaboration with LOA).

                 

This project is addressed to chemist or physicist candidates, interested in the experimental aspects of the research and motivated by the atmospheric impact of aerosols.

                 

Keywords: atmospheric particles, metrology of the aerosol, FTIR and UV-vis spectroscopy.

Workpackage of the Labex CaPPA: WP2

Supervisor: Denis Petitprez (PC2A) – Co-supervisor : Hervé Herbin (LOA)

 

Atmospheric chlorine chemistry modelling

The atmosphere is a complex chemical reactor in which a great number of reactions occurs. Most of these reactions are initiated by solar radiation and involves also chemical species either from natural or from anthropogenic sources. Although these compounds are present at very low level of concentration in the atmosphere (ppt to ppm), they could affect the environment and the climate. Human activities have noticeably changed the chemical composition of the atmosphere leading to the outcome of environmental problems such as global warming, or ozone depletion.

The reactions involving chlorine-containing species can modify the chemistry and the composition of the atmosphere. It stills however a lot of uncertainties in the understanding of the gas-phase atmospheric chemistry of these compounds.

The goal of this internship is to improve the understanding of the gas-phase reactivity of chlorine-containing species, to better address the lack of data in the field of atmospheric chemistry and to make a critical review of the literature to establish the chlorine chemical mechanism. 0D modelling studies will be conducted to evaluate the chlorine species speciation under various atmospheric conditions (temperature, photolysis, gas concentration, ...).

 

Keywords: Atmosphere, chlorine, chemical mechanism, 0D modelling

Linked to the workpackage of the Labex CaPPA : WP6

Supervisor(s): Valérie FEVRE-NOLLET / Florent LOUIS

Low-cost aerosol counters in a volcanic environment

The populations of aerosols are more and more studied because they present a very great diversity of chemical compositions, origins and distributions in sizes (oceanic, industrial, biogenic, volcanic, etc.). This wealth leads to multiple effects, that can be negative or positive, on the evolution of the Earth system and its biosphere: impact on climate, chemical balance (desert and marine aerosols) and imbalance (anthropogenic pollution) of ecosystems, pollen and human health problems, for instance. These impacts can be revealed at different scales (from indoor pollution to climate impact). It results in an interest in a wide range of instrumentation for the study and monitoring of aerosol populations at different scales from satellites to local in situ measurements.

Low-cost particle counters are now available and pave the way for in situ real-time mapping of aerosol populations. These sensors can easily be integrated, embedded and deployed in a network to probe hostile environments like a volcano, or an area with complicated topography such as a subway network. These small instruments are however much less efficient than the research instruments used in the laboratories, and characterization of their response to a given environment is necessary. In the framework of anemerging collaboration between LACy (University of La Reunion), LASIR (University of Lille) and PC2A (University of Lille), we propose an internship on the conditions of use of this instrumentation for the study of aerosols in the volcanic and oceanic environment of La Réunion island: the Optical Particle Counter OPCN3 (Alphasense company) counts particles in the range 350 nm - 40 µm in 24 channels and weights 100g. The Grimm MiniWRAS 1371 countsparticles in the range 10 nm - 35 µm in 41 channels and weights 7 kg. Thus, they allow to probe the kinetic of the Aitken and coagulation/accumulation modes. The internship will consist in working in the PC2A laboratory on the response of these sensors in a controlled atmosphere and then deploying the sensors during a campaign on the Piton de la Fournaise. The data will then be analyzed by combining routine aerosol measurements at the Reunion Island Atmosphere Physics Observatory (OPAR) located a few tens of kilometers from the volcano.

 

Keywords: Low-cost particle counter, sensor answer, natural aerosols, volcano, data science

Laboratories:LACy (Laboratoire de l’Atmosphère et des Cyclones) ; PC2A (laboratoire de Physicochimie des Processus de Combustion et de l'Atmosphère) ; LASIR (Laboratoire de Spectrochimie Infra-rouge et Raman) ; LOA (Laboratoire d’optique Atmosphérique)

Linked to the workpackage of the LabexCaPPA:WP 3

Supervisor(s): Guillaume Guimbretière (LACy) et Nicolas Visez (PC2A)

Unravelling the gas-phase atmospheric iodine reactivity using molecular simulations

The goal of this internship is to improve the understanding of the homogeneous reactivity of iodinated species with major photo-oxidants. It will provide a set of reliable kinetic and mechanistic data on gas-phase iodine reactions of atmospheric interest.

 

Theoretical chemistry is more and more used to determine rate constants for elementary reactions in the gas phase. In fact, the power of the actual computers allows now to obtain quantitative kinetic parameters within chemical accuracy. Quantum chemistry permits to understand the mechanism of the global reaction and of the different elementary pathways. It also allows to compute the molecular properties (molecular mass, vibrational frequencies, inertia moments) for the reactants, products, transition states, and molecular complexes. Then, the macroscopic properties such as the thermodynamical functions (internal energy, enthalpy, and Gibbs free energy) are computed from molecular properties using statistical thermodynamics. Finally, temperature and pressure dependencies of rate constants are estimated with kinetic theories using with the previously determined thermodynamical functions.

 

Keywords: Iodine, theoretical chemistry, reactivity, kinetics, atmospheric chemistry

Linked to the workpackage of the Labex CaPPA : WP6

Supervisor(s): Florent LOUIS / Marc RIBAUCOUR

Measurements of Polycyclic Aromatic Hydrocarbons and Oxygenated Polycyclic Aromatic Hydrocarbons in the combustion of advanced biofuels.

Biofuels are considered as promising sources for renewable energy production, which reduces the net CO2 emissions and the fossil fuel dependency. Combustion process is the mostly-used way to produce energy from fuels (>80% of the world’s primary energy supply is currently produced throughout combustion process; such process can be seen in flame burners, car engines, airplane engines, etc.). Recent studies have shown that the combustion of oxygenated biofuels produces lower amounts of large-sized soot particles (>10 nm) than conventional petroleum fuels. However, the biofuels potentially generate higher amounts of small-sized soot particles (<10 nm) and these particles contain a significant fraction of oxygenates including oxygenated polycyclic aromatic hydrocarbons (OPAHs) which are generally more toxic than polycyclic aromatic hydrocarbons (PAHs). These small-sized particles can penetrate deep into lungs and become very harmful for the health.

Due to the presence of oxygen atoms in the chemical structure of biofuels, the chemical species distribution and reaction mechanisms in the soot formation processes are expected to be much more complex compared to conventional fuels. Understanding the formation mechanism of these particles is therefore very challenging, but it is a prerequisite step towards developing cleaner combustion technologies of biofuels. PAHs have been proven to be the origin of soot formation, while the role of OPAHs in soot formation processes is less understood and will be explored in this internship. Concretely, the master student will identify and quantify PAHs and OPAHs in a premixed flame of fuel/biofuel mixture using gas chromatography (GC) instruments. These instruments are equipped with different columns, different detectors (thermal conductivity detector, flame ionization detector, a mass spectrometric detector), and a special system for trapping PAHs/OPAHs. The expected results will serve to analyze the relationship between OPAHs and PAHs, and their kinetic formation, which will provide a solid base for developing a longer-term proposal on the formation mechanism of small-sized soot particles in the combustion of biofuels.

 

Keywords: Biofuels, soot, PAHs, OPAHs, GC

Linked to the workpackage of the Labex CaPPA: WP 5

Supervisor: Luc-Sy TRAN, Co-Supervisor: Abderrahman El BAKALI

 

 

 

Thèses

Combustion de nouveaux biocarburants : étude du mécanisme de formation des Hydrocarbures Aromatiques Polycycliques Oxygénés (HAPOs) et des petites particules de suie (<10 nm)

Les biocarburants cellulosiques (BCC) contiennent dans leur structure un ou plusieurs atomes d’oxygène, et sont considérés comme une source prometteuse d'énergie alternative. Un de leurs intérêts est que leur combustion produit moins de particules de suie de grande taille (>10nm) comparé aux carburants conventionnels. Pour ces raisons, l’utilisation des BCC est en constante augmentation ces dernières années. Cependant, leur combustion peut générer un grand nombre de particules de suie de petite taille (<10 nm). Celles-ci contiennent également une proportion importante d’Hydrocarbures Aromatiques Polycycliques Oxygénés (HAPOs) rendant potentiellement les suies plus nocives. Comprendre et maitriser les mécanismes de formation des HAPOs, ainsi que leur responsabilité dans la formation des petites particules de suie est l’une des conditions préalables indispensables à l’utilisation des BCC comme énergie alternative, propre et sûre. Dans ce contexte, le projet de thèse proposé a pour objectif de contribuer à une meilleure compréhension des phénomènes physico-chimiques impliqués. Sa réalisation s’appuiera sur les compétences du laboratoire PC2A qui sont reconnues au niveau international dans le domaine. Le laboratoire PC2A dispose de bancs expérimentaux de haute technicité permettant de réaliser les travaux envisagés dans le cadre de ce projet. Ainsi, l’équipe a récemment fait l’acquisition de deux nouveaux dispositifs (notamment dans le cadre du CPER CLIMIBIO) qui seront mis en œuvre dans cette étude :

- un dispositif GC (chromatographie en phase gazeuse) permettant l’analyse quantitative d’espèces chimiques d’intérêt, équipé d’un système spécial dédié au piégeage des HAPs/HAPOs ;

- un dispositif SMPS (granulomètre de type Scanning mobility particle sizer) de toute nouvelle génération permettant la caractérisation de particules de l’ordre du nanomètre (1nm).

La haute sensibilité de ces dispositifs expérimentaux sera mise à profit pour l’analyse qualitative et quantitative des espèces chimiques clés impliquées dans la formation des particules de suie dans des flammes de BCC. L’obtention de cette base de données expérimentales, couplée avec le développement d’un modèle chimique détaillé, permettra une analyse fine de la cinétique de combustion des BCC et de formation des HAPOs/suie.

Programmes de recherche en lien avec le sujet : CPER Climibio / Labex CAPPA

 

Mots clés :   Biofuels, combustion, HAPs oxygénés, nucléation de suies, nanoparticules de suies (<10 nm)

 

Responsables et coordonnées :

Luc-Sy Tran                           luc-sy.tran@univ-lille.fr                      Tel: 03 20 43 49 78

Laurent Gasnot                      laurent.gasnot@univ-lille.fr                       03 20 43  48 02

 

Financement envisagé :  Bourse Région Hauts-de-France/ADEME/Labex CaPPA

 

Atmospheric Chemistry of Silicon Compounds and their Role in Indoor Air Quality

Indoor air quality and chemistry has been a subject of increasing interest in recent years. Indeed, we spend more than 80% of our time indoors, but the chemistry and health impacts of indoor air have attracted far less interest than that of outdoor air. Trace gas species are generally much higher indoors than outdoors, and this can be further enhanced in low energy buildings, where air exchange is reduced to a minimum in order to minimize energy consumption for heating (mostly in France) or cooling (mostly in Australia).

Volatile silicon compounds are present in a wide range of household items, particularly in personal care products such as cosmetics and deodorants. Of particular interest are the cyclic polysiloxanes, which are emerging persistent chemicals of concern. The atmospheric chemistry of silicon compounds remains relatively unstudied. However, in indoor environments volatile siloxanes can be present at significant concentrations. For example, it was recently shown that D4 (cyclic polysiloxane made of 4 Si- and 4 O-atoms) was the most abundant volatile compound in a university classroom. Even in outdoor environments silicon compounds can be found at high levels.

To understand potential health effects of indoor air we need to know the rate at which siloxanes are removed by reaction with free radical oxidants, which will control their airborne lifetimes. Moreover, we need to understand the chemical products that these compounds are ultimately transformed into, so that we can assess their impacts on human health and the environment.

This project is focused on verifying and then expanding our understanding of this chemistry, through a suite of combined experiments (in France) and theoretical simulations (in Australia) in order to characterize the rate at which volatile silicon compounds react with the OH radical, and identify the products that result from subsequent oxidation of the products.

The candidate will mostly carry out experiments in Lille using two different laser-based experimental set-ups: a laser photolysis system coupled to a detection by FAGE (fluorescence assay by gas expansion) and another laser photolysis system coupled to a detection by LIF (laser induced fluorescence) or cw-CRDS (cavity ring down spectroscopy). The PhD project also includes extended stays at the University Melbourne to get formation in theoretical chemistry and participate in the quantum chemical calculations. A counterpart PhD student at the University Melbourne will mostly do quantum chemical calculations and will participate in experiments during extended stays in Lille.

 

Programmes de recherche en lien avec le sujet :  PRC CNRS – University Melbourne

Mots clés : Indoor Air Quality, reaction kinetic, laser spectroscopy

Responsables et coordonnées :

PC2A                     Christa Fittschen                christa.fittschen@univ-lille.fr              Tel: 03 20 33 72 66

                                Coralie Schoemaecker      Coralie.schoemaecker@univ-lille.fr   Tel: 03 20 33 72 66

U Melbourne        Gabriel da Silva                   gdasilva@unimelb.eduau

Financement envisage : PhD grant secured in the frame of the PRC CNRS-Melbourne

 

Pollution sensors and building ventilation strategies

Since 2014 PC2A laboratory has been investigating the use of miniature gas and particle sensors to characterize the pollution levels inside buildings as well as the individual exposure of people to air pollutants. Recent results also pointed out the potential of miniature sensors to understand the behavior of the buildings themselves and of the people inside the buildings.

 

To further delve into these aspects, PC2A laboratory, in partnership with the Building Physics group at the University of Gent, is looking for a motivated student willing to undertake a PhD at the intersection of two fields with strong scientific, social and economic impacts : energy and public health. We propose to investigate, using the miniature air quality sensor systems developed at ULille, the mechanisms responsible for the outdoor to indoor transfer of pollutants, and the respective importance of particulate pollution from indoor and from outdoor origin. We will eventually be able to integrate the particles sensors into demand controlled ventilation systems, in order to renew the air in buildings while simultaneously considering the energy preservation objective prescribed for new buildings and ensuring a healthy indoor air for the occupants. The project therefore joins the expertise in atmospheric chemistry and physics and in individual exposure of the partners in ULille, with the expertise in building physics and ventilation of the UGent partner. The project relies on academic research that can be in a near future transferred to the economic world.

Due to the multidisciplinary nature of the envisioned project, candidates from various background may apply: atmospheric chemistry and physics, analytical chemistry, building science, architecture, public health…

 

Keywords: air quality, miniature sensors, building physics, ventilation schemes

 

Contacts :        Benjamin Hanoune           Benjamin.hanoune@univ-lille.fr   (PC2A, Lille)

                        Jelle Laverge                    Jelle.laverge@ugent.be             (Gent)

                               

 

Funding : I-SITE funding (not secured yet, main criterium is the candidate) : http://www.isite-ulne.fr/index.php/fr/app/co-tutelles-de-theses-2020-universite-de-gand/

Deadline for application: April 29, 2020.

 

Post-docs