Caractérisation et impact des différentes fractions d'une biomasse lignocellulosique pour améliorer les prétraitements favorisant sa méthanisation (utilisation de la paille de blé comme biomasse lignocellulosique d'étude)

La méthanisation est un processus biologique de transformation des matières organiques libérant principalement du méthane et du dioxyde de carbone. Cette technologie connaît un essor important pour la production de biométhane, source d énergie renouvelable. Elle présente cependant des rendements de dégradation faibles lorsque de la biomasse lignocellulosique est utilisée comme matière première. Pour optimiser son rendement, la paille de blé a été sélectionnée comme biomasse représentative et l impact sur la méthanisation de chacune des fractions (extractibles, hémicelluloses, cellulose et lignine) a été évalué. Une biomasse de synthèse a été construiteà partir des constituants pures de la paille de blé afin d évaluer l impact des interactions lignine-holocellulose. Le potentiel de méthanisation de différentes molécules phénoliques,provenant de la dégradation de la lignine, a été déterminé. Elles inhibent la méthanisation à l exception de trois d entres elles qui présentent un rendement de méthanisation élevé : les acides vanillique, l acide férulique et le syringaldéhyde. Différents prétraitements physique (le chauffage par échangeur thermique ou par irradiation aux micro-ondes ainsi que la sonication et le raffinage papetier) et chimique (la soude, l ammoniaque et l ozone) ont ensuite été sélectionnés, et leurs impacts sur lacomposition de la paille et sa méthanisation ont été mesurés. Les meilleurs rendements de méthanisation ont été obtenus suite à l exposition aux micro-ondes en présence de soude.Methanization or anaerobic digestion is a biological process to transform organicmatter into a gas mixture composed by a majority of methane and carbon dioxide. Thistechnology is developing rapidly for the production of biomethane as renewable energysource. However this biotechnological route has low performances when lignocellulosicbiomass is used as raw material.Wheat straw has been chosen as typical biomass and the role of each lignocellulosicfraction (extractives, cellulose, hemicelluloses and lignin) has been determined on theperformance of anaerobic digestion. A synthetic biomass has been built with different pureconstituents of the wheat straw to assess the impact of holocellulose-lignin interactions onmethanization. Then methane potential of various lignin degradation products (phenolicmolecules) has been studied. Majority of them have been shown an inhibitory effect butthree of them have been converted to methane: ferulic and vanillic acids andsyringaldehyde.Various physical pretreatments (heating, microwave irradiation, sonication andrefining) and chemical pretreatments (sodium hydroxide, ammonia and ozone) have beenselected to prepare the biomass to anaerobic digestion and their impacts on wheat strawcomposition have been evaluated. The best methanization yield has been obtained afterpretreatments by sodium hydroxide heating by microwave irradiation.BORDEAUX1-Bib.electronique (335229901) / SudocSudocFranceF

Near infrared analysis as a tool for rapid screening of some major wood characteristics in a eucalyptus breeding program

L'évaluation des propriétés du bois à des fins de sélection est généralement entravée par la durée et le coût des essais technologiques. Une des méthodes probablement la plus adaptable aux mesures rapides sur le bois est la spectrométrie en réflexion diffuse clans le proche infrarouge (SPIR). Au Congo. une sélection des meilleurs génotypes pour la plantation clonale est réalisée au sein d'une famille d'eucalyptus de plein frère issue d'une hybridation. Sur cette base génétique étroite, à partir d'échantillons de bois broyé, avant ou après extraction, des relations quantitatives entre les bandes spectrales issues de la SPIR et le taux d'extraits, la quantité et la composition de la lignine, la déformation longitudinale de croissance et les retraits sont analysés en terme de précision de la prédiction. Les résultats obtenus montrent que la SPIR peut être utilisée efficacement pour prédire les caractéristiques qui dépendent étroitement de la constitution chimique du bois. Cependant, la mesure de référence doit être précise et doit représenter la plus large gamme de valeurs pour obtenir des prédictions exploitables. Des améliorations méthodologiques et métrologiques sont envisageables. (Résumé d'auteur

A comparative study on the acetylation of wood by reaction with vinyl acetate and acetic anhydride

A comparative study on the acetylanon of maritime pine wood by reaction with vinyl acetate (VA) and acetic anhydride (AA) has been undertaken The reactivity of wood cellulose and lignin with regards to VA or AA was examined using different techniques The products dissolved in the reaction medium after acetylation of wood by the two different methods were analyzed by HPLC chromatography Results suggested that the cellulose sites in wood were more attacked by VA than by AA in our experimental conditions Besides the unreacted cellulose sites of the AA-acetylated sample could be further esterified by vinyl propionate which (13)C NMR signals could be differentiated from the acetyl signals The esterified materials obtained after modification of isolated cellulose and lignin were also characterized by FTIR (13)C CP-MAS NMR and (13)P NMR spectroscopy and compared Results indicated that VA could acetylate both biopolymers but they also showed that AA reacted more readily with lignin than VA Moreover FTIR spectroscopy revealed that unexpected side reactions concurrently occurred in lignin when VA was used It is hypothesized that some C-acetylation also took place between VA and a number of lignin aromatic rings during the treatment

Dispersibility and Emulsion-Stabilizing Effect of Cellulose Nanowhiskers Esterified by Vinyl Acetate and Vinyl Cinnamate

The surface of cotton cellulose nanowhiskers (CNW's) was esterified by vinyl acetate (VAc) and vinyl cinnamate (VCin), in the presence of potassium carbonate as catalyst. Reactions were performed under microwave activation and monitored by Fourier transform infrared (FT-IR) spectroscopy. The supramolecular structure of CNW's before and after modification was characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM). Distinctively from the acetylation treatment, an increase in particles dimensions was noted after esterification with VCin, which was assigned to pi-pi stacking interactions that may exist between cinnamoyl moieties. The dispersibility and emulsion stabilizing effect of acylated CNW's was examined in ethyl acetate, toluene, and cyclohexane, three organic solvents of medium to low polarity. The acylated nanoparticles could never be dispersed in toluene nor cyclohexane, but they formed stable dispersions in ethyl acetate while remaining dispersible in water. Stable ethyl acetate-in-water, toluene-in-water, and cyclohexane-in-water emulsions were successfully prepared with CNW's grafted with acetyl moieties, whereas the VCin-treated particles could stabilize only the cyclohexane-in-water emulsions. The impact of esterification treatment on emulsion stability and droplets size was particularly discussed

Functional Chitosan–Calcium Carbonate Coatings for Enhancing Water and Fungal Resistance of Paper Materials

The objective of this study was to increase the water resistance of paper while providing fungal resistance using a bio-based coating made from chitosan. The water resistance was improved through the surface control of roughness using modified calcium carbonate particles. The higher the quantity of particles in the film-forming solution, the higher the surface hydrophobicity of the paper. The addition of particles was found to counterbalance the chitosan hydrophilicity through the control of the coatings’ penetration in the paper bulk. As a consequence, the wetting time and liquid water resistance were enhanced. The antifungal activity of the film-forming solutions and coated paper was also investigated against the growth of Chaetomium globosum, which was selected as a model strain able to contaminate paper materials. The results reveal that the antifungal activity of chitosan was improved by a possible synergic effect with the bicarbonate ions from the mineral particles

Adding value to lignins isolated from sugarcane bagasse and Miscanthus

Attempt to depolymerize industrial organosolv lignin (from sugarcane bagasse) and lignins extracted from sugarcane bagasse and Miscanthus fibers (isolated by a soda/anthraquinone process) in presence of an anthraquinone acid catalyst (AQCOOH) was described. With the aim to substitute formaldehyde by glutaraldehyde, a dialdehyde that can be obtained from natural sources, lignins were reacted with glutaraldehyde and studied as phenolic-type resins for thermosets. The reactions were predominantly analyzed be SEC and P-31 NMR spectrometry. The Organosolv lignin-glutaraldehyde resin was used to prepare a composite reinforced with sugarcane bagasse fibers. Control samples were also prepared; specifically, composites based on phenol-formaldehyde and organosolv lignin-formaldehyde matrices. The results of the impact and the flexural strength tests of these composites showed that the organosolv lignin and glutaraldehyde can successfully replace phenol and formaldehyde, respectively

Anthraquinone polymer catalysts for alkaline delignification and action on a phenolic beta-O-4 lignin model in kraft pulping conditions

The delignification action of four new anthraquinone (AQ) polystyrene catalysts - three of them linear (CP-A, CP-B, CP-C) and one cross-linked (CP-3D) - were investigated on softwood (Pinus pinaster) chips under kraft pulping conditions, and their catalytic efficiency gains (EGs) were compared to that of AQ, with EG(AQ) = 100. The catalytic EG of the hydrophobic polymers CP-B and CP-3D was 96%, while the inherent hydrophilic catalyst CP-C showed an EG of 30%. Interpretation: hydrogen sulfide anions presented in the kraft pulp liquor might participate in the delignification mechanisms as redox active mediators in the case of the hydrophobic polymers. Moreover, the latter could be recovered after pulping, and delignification tests with the recovered materials revealed that they preserved their catalytic properties. Mechanistic studies were carried out with a phenolic beta-O-4 lignin model compound in the presence or absence of glucose (mimicking the carbohydrate end groups) and/or NaSH. It was shown that the cross-linked CP-3D polymer reacted with the lignin model through electron transfer reactions, a process most likely mediated by glucose and HS- redox active species. The concept of grafting AQ into polymeric substrates is discussed in terms of reusable delignification catalysts for large-scale pulping processes under kraft conditions

Anthraquinone polymer catalysts for alkaline delignification of lignocellulosic matter. Part 2. Action in soda pulping conditions on softwood and phenolic beta-O-4 lignin models

Two hydrophobic and one hydrophilic anthraquinone (AQ) polystyrene catalysts were tested under soda pulping conditions on thermomechanical fibers, and the results were evaluated based on commercial AQ. Hydrophobic and hydrophilic polymers had efficiency gains of 23%-28% and 57%, respectively, compared to AQ (100% efficiency). Hydrosolubility of AQ polymers played a major role in delignification efficiency, a property that allows a better contact with lignocellulosic fibers. Hydrophobic copolymers were stable under pulping conditions and preserved their catalytic effect entirely by contrast to the hydrophilic AQ, as demonstrated by recovery yields after pulping and catalytic action of the recovered copolymers. Studies on lignin models confirmed that the hydrophilic AQ polystyrene is a better catalyst under soda pulping conditions than the hydrophobic ones. It was demonstrated that AQ polystyrene polymers react with lignin models by electron transfer mechanisms