http://hdl.handle.net/2268/83 Search this channel search http://orbi.ulg.ac.be/simple-search http://hdl.handle.net/2268/148642 Title: What is the right pathway to be sustainable? Case of biofuels and bioproducts in Europe <br/> <br/>Author, co-author: Belboom, Sandra; Léonard, Angélique http://hdl.handle.net/2268/148631 Title: SAXS analysis in terms of density fluctuations within random observation window <br/> <br/>Author, co-author: Gommes, Cédric http://hdl.handle.net/2268/148514 Title: THREE-DIMENSIONAL RECONSTRUCTION OF LIQUID PHASES CONFINED IN DISORDERED POROUS MEDIA: AN IN SITU SYNCHROTRON SAS ANALYSIS <br/> <br/>Author, co-author: Gommes, Cédric; Hermida Merino, Daniel <br/> <br/>Abstract: We use Synchrotron Small-Angle X-ray Scattering to investigate temperature-induced morphological changes in binary hexane/nitrobenzene solutions confined in the pores of disordered mesoporous solids. The scattering data is analyzed with a plurigaussian model, which enables us to reconstruct the 3D morphology of the phases with a nanometer resolution. The reconstructions bring to light wetting transitions whereby the morphology of the nitrobenzene passes from a nanometer-thin layer that uniformly covers the solid surface to plugs that locally occlude the pore space. Our analysis enables us to quantitatively analyze the SAS data in terms of changing interface areas and wetting angles. The present contribution offers unprecedented insight into nanometer-scale wetting transitions. It also presents a novel SAS data analysis methodology that is applicable to a host of experimental situations involving disordered mesoporous materials. http://hdl.handle.net/2268/147985 Title: Importance of LUC and ILUC on the carbon footprint of bioproduct:case of bio-HDPE <br/> <br/>Author, co-author: Belboom, Sandra; Léonard, Angélique <br/> <br/>Abstract: Due to the depletion of fossil fuels and the increase of greenhouse gas emissions, solutions are needed to replace petrol based products. As a consequence, the number of biobased products developed using agricultural feedstock is continuously increasing. This study focuses on the carbon footprint of bio-HDPE produced either from Brazilian sugar cane or Belgian sugar beet. The goal of this study is to compare the carbon footprint of bio-HDPE with the fossil one, taking into account the effect of land use change. Common boundaries of the agricultural systems comprise the cultivation step for both crops, i.e. sugar cane and sugar beet, with all associated energy and fertilizer consumptions, the transportation step from field to the industrial plant, the sugar crops transformation into hydrate bioethanol, the by-products valorisation, the dehydration and polymerization steps and the HDPE incineration as end of life issue. Fossil scenario includes the production of ethylene, its polymerization and its incineration. When comparing the entire life cycle of bio and fossil HDPE, the GHG emissions are lower for the biobased product which is the willing effect. This result is only valid if no Land Use Change (LUC) or Indirect Land Use Change (ILUC) effect appears. To assess the environmental impact of the deforestation or of the transformation of a pasture into a field, the EC-Guidelines from the European Union were used in order to calculate the CO2 emissions depending on several parameters. For sugar cane, LUC consists in the transformation of pastures into fields in the region of Sao Paulo in Brazil. Three scenarios can be developed based on different agricultural practices for pasture and field (tillage and fertilizers inputs): the best, the worst and the average. The best case leads to a supplementary environmental gain. The worst and average achieve additional emissions. A payback time, considering the time needed to find again an environmental gain compared to the fossil counterpart, was calculated for the average scenario which is equal to 12 years. The ILUC effect for sugar cane is assumed to be deforestation due to the transformation of forest into pasture induced by the previous LUC effect. The rate of deforestation can vary between 16% or 100% depending on used statistics and leads to a payback time of respectively 26 and 101 years. For sugar beet, no LUC is considered. Indeed, no land expansion is available in Belgium due to small available areas. In the case of an increase of bioplastics production, Belgium should import sugar beet from neighboring countries which can induce ILUC. In this study, sugar beet is assumed to be provided by the Netherlands on pastures previously transformed into fields. The average scenario implies a payback time of 8 years. This study permits to highlight the importance of LUC and ILUC especially for energetic crops dedicated to replace fossil products. This effect can reverse expected results and induce long payback times. http://hdl.handle.net/2268/147477 Title: Convective drying of wastewater sludge: Introduction of shrinkage effect in mathematical modeling <br/> <br/>Author, co-author: Bennamoun, Lyes; Crine, Michel; Léonard, Angélique http://hdl.handle.net/2268/147385 Title: L’Analyse du Cycle de vie : quoi, pourquoi, comment ? <br/> <br/>Author, co-author: Léonard, Angélique http://hdl.handle.net/2268/147363 Title: Use of Life Cycle Assessment to determine the environmental impact of thermochemical conversion routes of lignocellulosic biomass: The gasification step <br/> <br/>Author, co-author: Gerbinet, Saïcha; Jeanmart, Hervé; Léonard, Angélique http://hdl.handle.net/2268/147251 Title: Modified TiO2-based Photocatalytic Films and Powders produced by Aqueous and Non-Aqueous Sol-Gel Processes for Water Purification <br/> <br/>Author, co-author: Malengreaux, Charline <br/> <br/>Abstract: Summary Two major research goals have been proposed for this thesis. The first goal concerns the development of photocatalysts in the shape of thin films coated on glass substrates which includes (i) the development of a sol-gel chemistry suitable for the production of stable colloidal suspensions of TiO2 particles, (ii) the optimization of the deposition method and (iii) the development of an experimental device to measure the photocatalytic activity of the films. The second objective is the development of innovative non-aqueous and aqueous sol-gel routes, including the development of new methods for the introduction of dopants as well as the photocatalytic testing of the resulting materials. Two original non-aqueous sol-gel processes involving respectively, an in situ production of water and the controlled addition of a small amount of water, have been developed to produce a series of stable colloidal suspensions of TiO2 particles (sols). From those sols, transparent, adherent, homogeneous thin films have been produced using an optimized dip-coating deposition method and have been proven to be photocatalytically active for the degradation of an organic pollutant in aqueous solution. The photocatalytic activity of the films has been improved through an increase of their roughness thanks to the addition of an organic additive into the sol, leading to an increased active surface involved into the photocatalytic reaction. A mathematical model allowing the rigorous evaluation of the kinetic parameters of the photocatalytic reaction taking into account the influence of the variation of the volume inside the batch photoreactor has been developed. The equations have been established in the case of a photocatalytic powder homogeneously dispersed in the pollutant solution, and in the case of a photocatalytic thin film placed at the bottom of the reactor. The particular case of a first order reaction has been treated and the error on the reaction rate constant induced by neglecting the volume variation has been quantified. An environmentally-friendly aqueous sol-gel process for producing undoped and Cu2+, Ni2+, Zn2+, Pb2+, Fe3+, Cr3+, La3+ or Eu3+ single-doped as well as La3+- Fe3+ and Eu3+- Fe3+ co-doped TiO2 bulk photocatalysts composed of nanocrystallites of anatase and exhibiting a remarkably high photocatalytic activity without requiring any calcination step has been developed. Different effects of the metal ion dopant on the photocatalytic activity have been observed and discussed according to the dopant nature and content. A kinetic study of the photocatalytic degradation of a model pollutant (4-nitrophenol) in aqueous solution under UV-Visible light (330 nm < λ < 800 nm) has been performed over a promising TiO2-Zn2+ doped catalyst. Statistical validations have confirmed the suitability of the phenomenological reaction rate model developed to represent the 4-nitrophenol photocatalytic degradation over time.; Résumé Deux objectifs majeurs ont été proposés dans le cadre de cette thèse. Le premier objectif concerne le développement de photocatalyseurs sous forme de films déposés sur des supports de verre ce qui implique (i) le développement d’une chimie sol-gel permettant la production de suspensions colloïdales stables de particules de TiO2, (ii) l’optimisation de la méthode de dépôt et (iii) le développement d’un dispositif expérimental permettant de mesurer l’activité photocatalytique des films. Le second objectif proposé est le développement de procédés aqueux et non-aqueux, ainsi que de nouvelles méthodes permettant l’introduction de dopants, afin d’obtenir des photocatalyseurs innovants sous forme de poudres. Deux procédés sol-gel non-aqueux impliquant une production d’eau in situ ou l’addition contrôlée d’une faible quantité d’eau dans le système réactionnel ont été développés afin d’obtenir des suspensions colloïdales stables de particules de TiO2 (sols). L’utilisation de ces sols stables a permis la production de films minces transparents, adhérents et homogènes au moyen d’un procédé de dépôt par dip-coating optimisé. Les films obtenus permettent la dégradation photocatalytique de polluants organiques en milieu aqueux. L’introduction d’une molécule organique au cours de la synthèse a permis l’amélioration de l’activité photocatalytique des films grâce à un accroissement de leur rugosité, entrainant une augmentation de la surface active de catalyseur déposé par unité de surface de support. Un modèle mathématique permettant l’évaluation rigoureuse des paramètres cinétiques de la réaction photocatalytique en tenant compte de la variation de volume au sein du réacteur discontinu a été développé. Les équations ont été établies d’une part, dans le cas d’une poudre photocatalytique dispersée de manière homogène dans la solution de polluant et d’autre part, dans le cas d’un film photocatalytique déposé au fond du réacteur discontinu. Le cas particulier d’une réaction de premier ordre a été examiné. L’erreur sur la valeur de la constante cinétique induite en négligeant la variation de volume au sein du réacteur discontinu a été quantifiée. Un procédé sol-gel respectueux de l’environnement permettant la production de catalyseurs de TiO2 purs et dopés sous forme de poudres a été développé. Les ions Cu2+, Ni2+, Zn2+, Pb2+, Fe3+, Cr3+, La3+ et Eu3+ ont été utilisés comme dopant et co-dopant dans le cas des ions La3+-Fe3+ et Eu3+-Fe3+. Ce procédé aqueux permet d’obtenir des catalyseurs composés de nanocrystallites d’anatase présentant une activité photocatalytique remarquablement élevée sans nécessiter de traitement à haute température. Enfin, une étude cinétique de la dégradation photocatalytique d’un polluant modèle (4-nitrophenol) en milieu aqueux et sous lumière UV-Visible (330 nm < λ < 800 nm) a été réalisée avec un catalyseur TiO2 dopé en ions Zn2+. Une analyse statistique des résultats a permis de valider que le modèle cinétique phénoménologique proposé peut être utilisé pour représenter les données dans tout le domaine expérimental étudié. http://hdl.handle.net/2268/147031 Title: Suivi par diffusion des rayons X aux petits angles de la formation de gels de résorcinol-formaldéhyde <br/> <br/>Author, co-author: Gommes, Cédric; Job, Nathalie http://hdl.handle.net/2268/147030 Title: Adsorption du bleu de méthylène sur des xérogels de carbone activés <br/> <br/>Author, co-author: Páez Martínez, Carlos; Contreras, Soledad; Léonard, Angélique; Olivera-Fuentes, Carlos; Pirard, Jean-Paul; Job, Nathalie http://hdl.handle.net/2268/146817 Title: Catalysts - special issue 'Aerogel catalysts' <br/> <br/>Editor: Job, Nathalie; Ioannides, Theophilos http://hdl.handle.net/2268/146816 Title: La pile à combustible: du marché de niche au marché de masse <br/> <br/>Author, co-author: Job, Nathalie http://hdl.handle.net/2268/146815 Title: Piles à combustible: vers une solution économiquement viable <br/> <br/>Author, co-author: Job, Nathalie http://hdl.handle.net/2268/146809 Title: The multiple SEA method: a method to synthesize Pt/carbon xerogel catalysts for Proton Exchange Membrane fuel cells <br/> <br/>Author, co-author: Zubiaur, Anthony; Chatenet, Marian; Maillard, Frédéric; Lambert, Stéphanie; Pirard, Jean-Paul; Job, Nathalie http://hdl.handle.net/2268/146808 Title: Catalytic layer for PEMFC based on carbon xerogels <br/> <br/>Author, co-author: Deschamps, Fabien; Traina, Karl; Pirard, Jean-Paul; Job, Nathalie http://hdl.handle.net/2268/146805 Title: Porous carbon material <br/> <br/>Author, co-author: Pirard, Jean-Paul; Pirard, René; Job, Nathalie http://hdl.handle.net/2268/146800 Title: Efficient Pt/carbon electrocatalysts for Proton Exchange Membrane fuel cells: avoid chloride-based Pt salts ! <br/> <br/>Author, co-author: Job, Nathalie; Chatenet, Marian; Berthon-Fabry, Sandrine; Hermans, Sophie; Maillard, Frédéric http://hdl.handle.net/2268/146799 Title: Continuous synthesis of porous carbon xerogel beads. Communication présentée par D. Eskenazi <br/> <br/>Author, co-author: Eskenazi, David; Kreit, Patrick; Compère, Philippe; Pirard, Jean-Paul; Job, Nathalie http://hdl.handle.net/2268/146797 Title: Continuous synthesis of porous carbon xerogel beads. <br/> <br/>Author, co-author: Eskenazi, David; Kreit, Patrick; Compère, Philippe; Pirard, Jean-Paul; Job, Nathalie http://hdl.handle.net/2268/146559 Title: Three-dimensional reconstruction of liquid phases in disordered mesopores using in situ small-angle scattering <br/> <br/>Author, co-author: Gommes, Cédric <br/> <br/>Abstract: Small-angle scattering of X-rays (SAXS) or neutrons is one of the few experimental methods currently available for the in situ analysis of phenomena in mesoporous materials at the mesoscopic scale. In the case of disordered mesoporous materials, however, the main difficulty of the method lies in the data analysis. A stochastic model is presented, which enables one to reconstruct the three-dimensional nanostructure of liquids confined in disordered mesopores starting from small-angle scattering data. This so-called plurigaussian model is a multi-phase generalization of clipped Gaussian random field models. Its potential is illustrated through the synchrotron SAXS analysis of a gel permeated with a critical nitrobenzene/hexane solution that is progressively cooled below its consolute temperature. The reconstruction brings to light a wetting transition whereby the nanostructure of the pore-filling liquids passes from wetting layers that uniformly cover the solid phase of the gel to plugs that locally occlude the pores. Using the plurigaussian model, the dewetting phenomenon is analyzed quantitatively at the nanometre scale in terms of changing specific interface areas, contact angle and specific length of the triple line.