WorldCat Identities

Chirat, Christine

Overview
Works: 30 works in 34 publications in 2 languages and 44 library holdings
Roles: Thesis advisor, Author, Opponent, Editor, Other
Publication Timeline
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Most widely held works by Christine Chirat
Extraction des hémicelluloses de pâtes papetières pour la production de pâte à dissoudre by Benoît Arnoul Jarriault( )

1 edition published in 2015 in French and held by 2 WorldCat member libraries worldwide

Les pâtes à dissoudre, composées à 95% de cellulose, sont la matière première pour la production de fibres cellulosiques régénérées (viscose, Lyocell...) et de dérivés cellulosiques (ester, éther ou nitrate de cellulose). En tant qu'alternative aux matériaux issus de ressources pétrolières, ces produits connaissent actuellement un fort regain d'intérêt. Ainsi, la production de pâte à dissoudre devrait croître fortement au cours de la prochaine décennie. L'objectif de cette thèse est de proposer des procédés de conversion d'une pâte papetière de résineux en pâte à dissoudre. Pour cela les hémicelluloses présentes dans les pâtes kraft papetières doivent être extraites. Trois méthodes d'extraction d'hémicelluloses ont ainsi été étudiées : (1) une extraction alcaline à froid (CCE) dans des conditions non conventionnelles, (2) un procédé se divisant en deux étapes successives : un stade acide à haute température (150°C) suivie d'une extraction alcaline à chaud (AHCE) et (3) une hydrolyse enzymatique par trois enzymes commerciales (une xylanase, une mannanase, une cellulase). Les deux premières méthodes ont permis de produire des pâtes avec des caractéristiques proches des pâtes à dissoudre commerciales. Cependant, dans les trois voies d'extraction étudiées, l'extraction d'hémicelluloses n'a jamais atteint 100%. Des prétraitements des pâtes (raffinage, explosion à la vapeur, oxydation TEMPO) ont alors été testés pour améliorer l'extraction des hémicelluloses. De nouvelles séquences de purification basées sur la combinaison d'une étape de raffinage suivie d'une extraction alcaline à froid (CCE) peuvent être ainsi imaginées. La dernière partie de ces travaux de thèse s'est intéressée au gonflement des pâtes à dissoudre. Les travaux ont abouti à la création d'une nouvelle méthode simple et rapide de caractérisation du gonflement des fibres de pâte cellulosique. Cette méthode de mesure peut être, dans certaines conditions, considérée comme une mesure alternative de la réactivité des pâtes à dissoudre habituellement caractérisée par le test Fock
Effet de l'ozone sur les hydrates de carbone et la lignine des pâtes à papier chimiques : application au blanchiment by Christine Chirat( Book )

2 editions published in 1994 in French and held by 2 WorldCat member libraries worldwide

L'objectif de ce travail est d'analyser les effets de l'ozone sur les hydrates de carbone et la lignine contenus dans les pates a papier chimiques, et en particulier dans les pates kraft de résineux, ainsi que les conséquences de ces effets sur la qualité des pates blanchies a l'ozone, et sur les résultats obtenus dans des stades de blanchiment ultérieurs. Apres un premier chapitre consacre a une revue de la littérature sur l'ozone en milieu aqueux, sur son action sur les hydrates de carbone et la lignine, ainsi que sur son utilisation dans le blanchiment des pates a papier chimiques, un deuxième chapitre porte sur l'analyse des effets de l'ozone sur les hydrates de carbone et la lignine résiduelle d'une pate kraft de résineux, et plus globalement sur diverses pates a papier de différentes natures. Dans le troisième chapitre sont étudiés les effets des cations métalliques sur le blanchiment a l'ozone, en distinguant les cations présents dans la pate de ceux éventuellement présents dans l'eau du procédé. Le quatrième chapitre traite du cas de l'ozone dans des séquences de blanchiment sans composes chlores, et plus particulièrement des conséquences des modifications apportées par l'ozonation a la cellulose et a la lignine sur un stade de blanchiment ultérieur. L'optimisation de la séquence choisie est également réalisée. Dans le cinquième chapitre l'ensemble des résultats obtenus est explique en faisant appel, entre autres, a des techniques de détection des radicaux hydroxyles, et a des expérimentations de gamma radiolyse de l'eau. Les actions respectives de l'ozone moléculaire et des radicaux hydroxyles générés sont ainsi précisées. En conclusion les perspectives de l'utilisation de l'ozone en blanchiment sont discutées
Study on extraction and characterization of softwoods hemicelluloses oligomers and their influence on gut microbiota by Vivien Deloule( )

1 edition published in 2017 in English and held by 2 WorldCat member libraries worldwide

Détermination du potentiel prébiotiques des hémicelluloses de bois résineux
Relation morphologie/réactivité des substrats lignocellulosiques : impact du prétraitement par explosion à la vapeur by Charlotte Loustau Cazalet( )

1 edition published in 2018 in French and held by 2 WorldCat member libraries worldwide

In a context of energy transition and climate change challenge, the production of second generation ethanol seems to be a very promising way to reduce our dependence on fossil fuels. There are 3 key steps for producing this new biofuel: pretreatment to decompose the lignocellulosic biomass and to make cellulose more accessible to enzyme attacks, enzymatic hydrolysis to produce fermentable sugars and fermentation to convert these sugars into ethanol. Currently, the pretreatment considered to be the most efficient, and mainly retained for industrialization, is the steam explosion pretreatment. However, some aspects such as the physicochemical effects induced by pretreatment and their impacts on the characteristics of pretreated biomass remain misunderstood.Schematically, the steam explosion pretreatment can be separated into two stages: the first is similar to an acid cooking carried out at 150-200°C during 5-30 min and allows mainly the hydrolysis of hemicelluloses, while the second is an explosive release which allows a mechanical bursting of the substrate potentially making the cellulose more reactive to enzymatic hydrolysis. As a whole, the effects of this type of pretreatment on lignocellulosic biomass are now well known, but the understanding of the different physicochemical phenomena occurring within it remains limited. Indeed, decoupling the cooking stage and the expansion stage is complicated because the reactor temperature (which mainly impacts the cooking reactions) is directly related to its pressure (which mainly impacts the explosive release) by the phase thermodynamics.This thesis work aims to better understand all the physicochemical phenomena occurring during a steam explosion pretreatment, based in particular on experimental discrimination of chemical phenomena (depolymerization reactions) and physical phenomena (explosive release) as well as on a multi-technical and multi-scale characterization of the lignocellulosic biomass obtained after this type of pretreatment. The objective is also to understand what are the main characteristics of biomass that explain the differences in reactivity observed during the enzymatic hydrolysis step and to explain the impact of the steam explosion pretreatment on the physicochemical properties and therefore the reactivity
Production de cellulose pure à partir de bois par un procédé d'épuration et de blanchiment propre à base d'ozone, en vue d'une valorisation textile ou chimique by Jordan Perrin( )

1 edition published in 2016 in French and held by 2 WorldCat member libraries worldwide

Le blanchiment est toujours l'un des points critiques en termes d'impact environnemental lors de la production de pâte de bois. Une nouvelle séquence « propre » de blanchiment sans réactifs chlorés (TCF) et à base d'ozone a permis d'obtenir une pâte à dissoudre blanchie dont les propriétés sont semblables à celles de pâtes blanchies par des séquences conventionnelles ECF à base de dioxyde de chlore. Il est montré que la pâte TCF a une meilleure stabilité de blancheur que la pâte ECF correspondante. Les phénomènes de jaunissement dont les mécanismes sont toujours mal compris ont été étudiés en mettant en œuvre diverses méthodes dont la spectroscopie RPE et la spectroscopie UV Raman et l'analyse des groupements carbonyle et carboxyle par fluorescence. Les groupes carbonyle que peut porter la cellulose se sont montrés néfastes pour la stabilité de la pâte, à la fois dans les conditions d'un vieillissement accéléré et en conditions alcalines de mercerisation. Ils peuvent néanmoins être partiellement éliminés par un traitement alcalin, ce qui se traduit par une meilleure stabilité de blancheur. L'addition de peroxyde d'hydrogène dans ce traitement permet d'obtenir des résultats encore meilleurs, sans élimination supplémentaire des carbonyles. Il aurait pour effet d'éliminer des chromophores résiduels de type quinonique et ayant un très fort impact sur le jaunissement des pâtes. La pâte TCF possèderait moins de chromophores quinoniques qu'une pâte ECF
Etude de l'impact de l'autohydrolyse sur les constituants du bois et sur le déroulement du procédé de production de cellulose pure by Hélène Curmi( )

1 edition published in 2018 in French and held by 2 WorldCat member libraries worldwide

This study is a part of a large project which aim is to convert a pulp mill into a fully integrated biorefinery by adding an autohydrolysis step to remove and valorize hemicelluloses prior to cooking. This thesis's goal is to study the impact of adding an autohydrolysis step on wood components and on the subsequent delignification and bleaching processes applied to this wood to produce pure cellulose. Wood components were analyzed before and after autohydrolysis. In particular it was shown that autohydrolysis increases the amount of free phenolic groups, and lowers the involvement of lignin in lignin carbohydrates complexes. A new NMR method using Dynamic Nuclear Polarization was performed directly on milled wood to look at wood components structure without extraction's steps to avoid chemical modifications.The second part describes the test of pulp processes (alkaline cooking, oxygen delignification and bleaching) on autohydrolysed wood chips. It showed that the addition of this autohydrolysis step improves delignification during cooking to such an extent that soda cooking alone is possible and efficient. Oxygen delignification was also improved. Two bleaching sequences with or without chlorinated compounds (ECF and TCF) were applied and compared, and it was concluded that sustainable bleaching without any chlorinated reagents is feasible. Finally, evaluation of bleached pulp properties demonstrated that viscose application can be targeted. Indeed, pulp had high purity cellulose content, adequate degree and high brightness and brightness stability
Blanchiment des fibres cellulosiques par l'ozone : effet sur les propriétés des fibres by Shree Prakash Mishra( Book )

2 editions published in 2010 in English and held by 2 WorldCat member libraries worldwide

L'effet de l'ozone sur la viscosité, la morphologie des fibres, le comportement au raffinage et la résistance mécanique des pâtes kraft est un sujet controversé qui anime les fabricants de pâte à papier, les fournisseurs d'ozone et les laboratoires de recherche. L'objectif de cette thèse est d'accroître la connaissance sur le sujet et de contribuer à l'essor du blanchiment à l'ozone dans l'optique d'un développement durable de l'industrie des pâtes à papier. Il est montré que l'incorporation d'un stade à l'ozone dans une séquence de blanchiment ECF de pâte d'eucalyptus ou de pin radiata permet de réduire le coût en agents de blanchiment et d'accroître la blancheur finale. Le blanchiment par l'ozone réduit la viscosité de la cellulose, sans toutefois affecter les principales caractéristiques mécaniques de la pâte, ni la morphologie des fibres. Les autres avantages des traitements de blanchiment incorporant l'ozone sont une meilleure élimination des extraits, une réduction de l'énergie nécessaire au raffinage des fibres et une moindre rétention d'eau par la pâte. Ces avantages sont observables pour des taux d'ozone et des séquences de blanchiment convenablement choisis
Contribution à l'étude du gluten comme matériau : apport de lignines de différentes natures. by Antoine Duval( )

1 edition published in 2013 in French and held by 2 WorldCat member libraries worldwide

Wheat gluten, a set of proteins from the wheat kernel, is commonly used to process polymeric materials, usually in the presence of glycerol as a plasticizer. Their use is however limited, because of their high sensitivity to water and relatively poor mechanical properties when compared to synthetic polymers. We first evaluated the influence of the glycerol content on the water absorbance, the phase separation and their glass transition.Then, another biopolymer, wood lignin, has been incorporated into the materials in order to enhance their properties. The influence of different types of lignin from the pulp paper industry, Kraft lignin and lignosulfonates, have been investigated. Kraft lignin addition enhances materials rigidity and thermal properties, and reduces the water sensitivity, whereas lignosulfonates allow to decrease the glycerol content, resulting in better mechanical properties and reduced water sensitivity.To gain insights into the interactions between gluten and lignins, several fractionation procedures have then been carried out. The influence of the protein type and lignin molecular mass could be pointed out, and where correlated to the materials macroscopic properties
Etude des possibilités de production d'éthanol hémicellulosique dans le cadre d'une bioraffinerie papetière. by Jérémy Boucher( )

1 edition published in 2014 in French and held by 2 WorldCat member libraries worldwide

La réduction de la consommation des carburants fossiles est l'un des enjeux majeurs du XXIème siècle. Le bioéthanol représente une alternative durable à l'essence, mais sa production est limitée puisqu'il est produit à partir de ressources alimentaires. L'éthanol de seconde génération offre une alternative pour relancer son développement. Encore au stade expérimental, il serait produit à partir de biomasse lignocellulosique (bois, paille, plantes annuelles..) et donc ne concurrencerait pas l'alimentation humaine. Cette thèse s'inscrit dans le cadre de production d'éthanol de 2nde génération dans une usine de pâte kraft. Dans ces usines, les hémicelluloses, qui représentent 20 à 30% du bois, ne sont pas valorisées. Cette étude porte sur l'extraction de ces hémicelluloses en amont du procédé et de leur fermentation en éthanol. Elle consiste à la mise au point et l'optimisation d'un procédé global allant du copeau de bois à l'éthanol
Blanchiment final des pâtes papetières cellulosiques par l'ozone by Guillaume Pipon( Book )

2 editions published in 2007 in French and held by 2 WorldCat member libraries worldwide

Ozone, which is already employed as a reagent at the beginning of the bleaching sequence of paper pulps, could be very interesting at the end of the sequence where it can, in neutral medium, improve brightness without degrading cellulose. In this thesis, the main chemical mechanisms of the ozone final bleaching stage were revealed, and an optimization of the process was proposed for an industrial use. Our study especially demonstrates that new chromophores can be created during the ozone-lignin reactions, and the lignin and hexenuronic acid groups contents have to be low before applying ozone. In an industrial point of view, medium consistency ozonation seems to be the best technological solution for the process and can replace the last D stage of an ECF chemical pulp with a lot of advantages. Endly, it was discovered that a high temperature improves the final brightness and heat stability of the pulp
Contribution à l'étude du blanchiment des pâtes papetières obtenues par des procédés sans soufre by Nicolas Bénattar( Book )

2 editions published in 2005 in French and held by 2 WorldCat member libraries worldwide

Sulfur free processes are alternative to Kraft process for chemical pulping. Some of these processes, such as the I.D.E. process considered in this study (combining the effect of caustic soda, ethanol and anthraquinone which acts as catalyst), lead to increase pulp yield, improved energy generation (by black liquor combustion) and reduced olfactory problems. However the I.D.E. pulp exhibits bleachability problems, which is a common characteristic of all pulps produced by the alkaline sulphur free processes. The main result of this work is that quinone groups, present in residual lignin, would be responsible for the poor bleachability. The rate of quinones groups in residual bleaching is influenced by cooking parameters, and wood species. This has been demonstrated by two independant methods : 19F NMR spectroscopy of fluorinated lignin and voltametry. In order to deal with this problem, hydrogen peroxyde can be advantageously added to the bleaching process. Its specific action on quinone groups explains the po
Contribution à l'étude des complexes lignine-hydrates de carbone (LCC) dans le bois : étude de l'impact des différentes étapes d'un procédé de bioraffinerie sans soufre sur les LCC by Claire Monot( )

1 edition published in 2015 in French and held by 2 WorldCat member libraries worldwide

The valorization of lignocellulosic biomass is nowadays a major issue due to the reduction of fossil resources. Separating each component to valorize them the best way as possible is the goal of the pulp and paper biorefineries. The effluent of the mill, called the black liquor, is currently burnt to produce energy, but gasification would increase the energy efficiency. For this, a sulfur-free cooking of wood is necessary, as sulfur inhibits gasification.Therefore this study first focused on the feasibility of cooking without sulfur, which is more difficult than a conventional kraft cooking containing sulfur. The work was done on softwood which is more difficult to delignify than hardwood. The wood was first pretreated with an autohydrolysis to remove hemicelluloses for further valorization.The results were conclusive for the production of cellulose pulp for chemical applications. To explain the differences obtained, structural differences of wood components were looked for. Lignin did not show major differences whether the wood was prehydrolyzed or not, whereas the complexes between lignin and carbohydrates (LCCs) showed significant differences, which would explain the results obtained
Special issue - this issue contains selected papers from the 14th European Workshop on Lignocellulosics and Pulp (EWLP) June 28-30, 2016, Autrans, France by European Workshop on Lignocellulosics and Pulp( Book )

1 edition published in 2017 in English and held by 2 WorldCat member libraries worldwide

Etude de procédés de dépolymérisation d'oligosaccharides d'hémicelluloses dans le cadre d'une bioraffinerie papetière by Valentin Guigon( )

1 edition published in 2019 in French and held by 2 WorldCat member libraries worldwide

Lignocellulosic biomass is made of 30% of hemicelluloses. Hemicelluloses are themselves made of saccharides that are true platform chemicals due to their ability to be transformed into many different products. Within the context of a biorefinery, hemicelluloses were solubilized as monosaccharides and oligosaccharides after a water pre-hydrolysis treatment. Secondary acid and enzymatic hydrolysis treatments were further applied to the obtained hydrolysate to depolymerize as much oligosaccharides as possible to monosaccharides (acid hydrolysis) and to depolymerize as much as xylans as possible to xyloses (enzymatic hydrolysis). Treatments were optimized to pilot scale
Nouvelles conditions d'utilisation de l'ozone dans le blanchiment des pâtes cellulosiques. Application à la mise au point d'un procédé de blanchiment "vert" by Frédéric Pouyet( )

1 edition published in 2014 in French and held by 2 WorldCat member libraries worldwide

The lack of understanding regarding the reactions of ozone with pulp components is one of the reasons why chlorine-free bleaching never really developed. Ozone is actually believed to lead to an extensive degradation of cellulose, contrary to the agent it could replace: chlorine dioxide. However, as the use of chlorinated compounds has many drawbacks, including the generation of toxic compounds, non-degrading chlorine-free bleaching sequences have to be designed. To do so, a better understanding of reactions involving ozone and hydrogen peroxide has to be gained. The first part of this very work consisted of a literature review. In the second part, some of the main hypotheses extracted from the literature were compared with other elements and first results, to show they inevitably led to contradictions and that new theories were needed. The third part was dedicated to ozone. The order of its reactions with pulp components was first of all checked. The properties of pulps of various compositions were then measured through ozonations. This study led to a new hypothesis, which was validated thanks to ESR spectroscopy. The reaction of ozone with some non-aromatic unsaturated compounds seems to give radical species. Those radical species would be in turn responsible for the depolymerization of cellulose, and the formation of carbonyl groups on cellulose as well. The fourth part dealt with the impact of alkaline treatment on cellulose after ozonations. Observations about carbonyl content and degree of polymerization suggest a new mechanism related to carbonyl and nucleophilic agents, explaining a main part of the depolymerization undergone by the cellulose. The last chapter of this work summarizes the trials regarding the optimisation of a chlorine-free bleaching sequence. It proves that high-quality pulps can be obtained by chlorine-free processes
Etude de l'impact de l'extraction des hémicelluloses du bois sur les procédés d'obtention de cellulose et d'éthanol dans le cadre d'une bioraffinerie lignocellulosique by Lucie Boiron( )

1 edition published in 2012 in French and held by 2 WorldCat member libraries worldwide

Biofuel revival could be a great opportunity for the chemical pulp industry to widen the range ofits products made from wood. This thesis deals with the integration of a softwood hemicelluloseextraction step prior to the Kraft pulping process in order to produce both cellulose fibres andbioethanol.In this study the experimental work covers the entirety of the process: from the extraction ofmore than half of the hemicelluloses from wood either by autohydrolysis or dilute acid hydrolysis tothe production of bleached cellulosic fibres as well as ethanol from fermentated wood hydrolyzates.Prehydrolyzed wood and their subsequent pulps stood out by their excellent delignification abilityduring Kraft cooking and oxygen bleaching. Quantitative analysis of the main constituants of thepulps showed why prehydrolysis leads to decreased Kraft pulp yields (extra lignin loss andhemicelluloses loss including xylans). A range of hypotheses to explain the good delignificationability of prehydrolyzed wood Kraft pulps during oxygen bleaching was narrowed to one by Kraftlignin analysis.The overall results of the hemicellulose extraction prior to Kraft pulping as it has been defined inthis study showed that from 100 kg of softwood, 27 to 36 kg of bleached cellulosic fibres and 6litres of ethanol could be produced. The bleached cellulosic fibres are of great interest for dissolvingpulp or cellulose nanocrystals production
Nouvelles utilisations de l'ozone dans le traitement des pâtes ligno cellulosiques by Dinah Nyangiro( )

1 edition published in 2003 in English and held by 1 WorldCat member library worldwide

Développement de nouveaux milieux et catalyseurs acides pour la transformation de biomasse lignocellulosique en molécules plateformes by Alban Chappaz( )

1 edition published in 2014 in French and held by 1 WorldCat member library worldwide

The thesis presented in this document aims at converting lignocellulosic biomass into levulinic acid. This target is a valuable building block which can lead to various products.This platform intermediate can be obtained by acid-catalyzed conversion of cellulose contained in raw biomass. However, the state of the art concerning this acid-catalyzed reaction revealed that the current conditions (diluted acids in harsh temperature conditions) result in numerous by-products formation. The selectivity issue often deals with process control, in particular with reaction time optimization.Our approach lies in using concentrated Brønsted acids as alternative media to catalyze cellulose conversion. Indeed, the high acidity level allow the interaction with hydrogen bonds in cellulose fibrils and favor cellulose decristallization. This property should promote the transformation of cellulose into levulinic acid at lower temperature thus limiting the formation of by-products. Therefore, acidity measurements in such media have been developed and performed. An extensive study on glucose and Avicel cellulose conversion in concentrated aqueous solutions of sulfuric acid was performed at 80°C. Levulinic acid yields, up to 50 mol%, were determined by HPLC analysis and a special attention was dedicated to the identification and quantification of soluble or insoluble by-products, allowing the characterization of new species never described in aqueous solutions. Referring to the acidity levels previously determined, a comparison between acidity and catalytic results will be setted.Finally, the effect of metallic chloride addition on the transformation of glucose and cellulose in sulphuric acid solutions has been investigated, revealing improvements yielding up to 70 mol% levulinic acid. This range of selectivity is unprecedented at such a low temperature
Génie des procédés appliqué à la fabrication des pâtes cellulosiques by Christine Chirat( )

1 edition published in 2003 in French and held by 1 WorldCat member library worldwide

Biorefinery in a kraft pulp mill : from bioethanol to cellulose nanocrystals by Christine Chirat( )

1 edition published in 2010 in English and held by 1 WorldCat member library worldwide

 
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Alternative Names
Christine Chirat wetenschapper

Languages
French (18)

English (6)