Dissertations / Theses: 'Lignite Oxidation'

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Tyhoda, Luvuyo. "Oxidative ammonolysis of technical lignins and lignites." Thesis, Stellenbosch : Stellenbosch University, 2003. http://hdl.handle.net/10019.1/53548.

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Thesis (MSc)--Stellenbosch University, 2003.
ENGLISH ABSTRACT: Today there is renewed interest in using soil improvers with fertilising capability as the use of inorganic fertilisers results in ground water pollution through leaching and formation of nitrates in plant materials. Lignin is an important precursor of humic material in soils and with modification, can be used as a raw material for producing slow release nitrogenous fertilisers. This project focussed on the use of industrial residues such as technical lignins which are produced by the South African pulping industry as well as low grade coals such as lignite occurring in South Africa, for the production of high-grade humic substances like Novihum TM, using the special technology developed by the Institute of Plant and Wood Chemistry of the Technical University of Dresden in Germany. Technicallignins derived from kraft lignin, sugar cane baggase, autohydrolysis lignin with a trade name Sucrolin, a calcium lignosulphonate and South African lignites mined in the Kraaifontein and BraekenfeIl areas as well as German brown coal were subjected to oxidative ammonolysis with the aim to produce slow release nitrogenous fertilizers. Curie Point Pyrolysis GCIMS was used to determine the structural composition of the raw materials and products. Oxidative ammonolysis reactions were carried out on a laboratory and a pilot plant scale. Highest nitrogen contents were obtained with Sucrolin lignin followed by the lignite from Germany. The amount of nitrogen that could be fixed with oxidative ammonolysis varied between 1.44 - 10% for the various raw materials. The CIN ratios obtained were in the range between 5 - 34. Marginal differences were observed between the materials modified on lab and pilot plant scales. There were improvements in the total incorporated nitrogen when the raw materials were pre-activated with oxidising agents such as hydrogen perxide and a fungal species, Phanaerochateae chrysosporium prior to oxidative ammonolysis. Variable amounts of differently bonded nitrogen forms were obtained for the materials tested due to their structural differences.
AFRIKAANSE OPSOMMING: Daar is deesdae hernude belangstelling in die gebruik van grondverbeteringsmiddels wat ook 'n bemestingsfunksie het, aangesien die gebruik van anorganiese kunsmis besoedeling van grondwater deur uitlogingen insypeling veroorsaak, wat weer tot die vorming van nitrate in plantmateriaallei. Lignien is 'n belangrike voorloper van humiese materiale in grondstowwe en kan dmv modifisering gebruik word as 'n grondstof vir die produksie van stadigstikstof vrystellende nitro gene kunsmisstowwe. Die huidige projek het gefokus op die gebruik van industriële residue en tegniese ligniene wat deur die Suid- Afrikaanse pulpnywerheid geproduseer word, sowel as lae-graad steenkool soos ligniet wat in Suid-Afrika aangetrefword, vir die produksie van hoë-graad humiese stowwe soos Novihum TM. Hierdie produk is mbv spesiale tegnologie deur die Instituut van Plant- en Houtchemie van die Tegniese Universiteit van Dresden in Duitsland ontwikkel. In hierdie ondersoek is verskeie Suid-Afrikaanse tegniese ligniene soos Kraft lignien, suikerriet bagasse, 'n outohidrolise lignien met die naam van Sucrolin en 'n kalsiumlignosulfonaat sowel as SA ligniete, afkomstig van Brackenfell en Kraaifontein, gebied en Duitse bruinkool, aan oksidatiewe ammonolise onderwerp om sodoende verskillende, stadigvrstellende, stikstofryke kunsmisstowwe te vervaardig. Curie Punt Pirolise GC/MS is gebruik om die chemiese struktuur van die grondstowwe en produkte vas te stel. Oksidatiewe ammonolise reaksies is op 'n laboratorium en loodsaanlegskaal. uitgevoer. Die hoogste stikstofinhoud is met Sucrolin lignien verkry, gevolg deur die ligniet van Duitsland. Die hoeveelheid stikstof wat dmv oksidatiewe ammonlise bereik kon word, het tussen 1.44 en 10% gewissel. Die CIN verhoudings wat verkry was, het varieer tussen 5 en 34. Marginale verskille is tussen laboratorium - en loodsaanlegsskaal gemodifiseerde grondstowwe waargeneem. Daar was verhogings in stikstofinhoud wanneer die grondstowwe vooraf met oksiderende middels soos waterstofperoksied of swamkultur soos Phanaerochatae chrysosporium, aktiveer is. Stikstof is op verskillende maniere en in verskillende hoeveelhede gebind.

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Olsson, Moa. "Preparation of Lignin Diesel : Experimental and Statistical Study of the Biodiesel Preparation Process from a Pulp- and Paper Industry Residual Product." Thesis, Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-37420.

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The use of fossil fuels is depleting the petroleum resources and the emissions exhausted during the use is contributing to the planets temperature rise, glaciers reciding and rised sea level etc. In a global perspective, the liquid petroleum fuels are dominating the fuel market. In the coming ten years, the use of liquid fuels is expected to grow. In this work a method of preparing a biodiesel microemulsion between petroleum diesel and kraft lignin has been examined. Lignin is a renewable by-product from the pulp- and paper industry, extracted from black liquor. In its natural appearance, lignin is not soluble in water and has to be modified to work as the hydrophilic phase in the microemulsion. The modification is achieved in a oxidative ammonolysis process. As an indication of how well the modification is performing, the amount of dissolved lignin in water were measured. The influence by the reaction time, pH-value and water content on the amount of dissolved lignin were examined in a statistical model in the software MODDE. A screening examination was performed to find the most influential factors. The MODDE model was optimized and could thereafter be used as a predictive tool and predict the outcome of responses within the experimental range. Ultrasonication was used to create the microemulsion. A stabilization test was performed by observing the created lignin diesel samples during three weeks. The operational cost of producing lignin diesel was calculated based on the chemical cost and the cost of electricity consumed during the production process. A microemulsion was not created between diesel and modified lignin, rather an emulsion was achieved. The highest amount of dissolved lignin in the oxidative ammonolysis process were 99.77 %. The most influential factor was the pH-value in the oxidative ammonolysis process. The water content also affected the amount of dissolved lignin, while the reaction time factor within its range did not affect the amount of dissolved lignin. The statistical model design, execution and predictive ability were evaluated in MODDE and given a satisfying grade. In the stability test, a separation in the bottom of the samples were observed after 0.5 h time. After one week, there was a small colour gradient in the top of one of the samples. After two weeks, the same colour gradient were observed in all of the samples. In none of the samples, a total phase separation was observed under the three weeks.
Användningen av fossila bränslen utarmar jordens petroleum resurser och under användning utsöndras emissioner som bland annat bidrar till den globala uppvärmningen, smältande glaciärer och höjda havsnivåer. Globalt sätt dominerar de flytande petroleum bränslena bränslemarknaden och dess användning förväntas inom de närmsta tio åren öka. I detta examensarbete undersöks och testas en metod för framställning av lignindiesel. Lignindieseln består av petroleumdiesel och lignin, vilka hålls ihop med hjälp av en mikroemulsion. Lignin är en förnybar restprodukt från pappers- och massaindustrin som utvinns från svartlut. I naturligt utförande är lignin inte blandbart med vatten och behöver därför modifieras för att kunna agera som hydrofil fas i mikroemulsionen. Modifieringen görs genom en oxidativ ammonolysprocess. Som indikation på hur modifieringen verkade på ligninet mättes mängden löst lignin i vatten. Påverkan av faktorerna reaktionstid, pH-värde och vatteninnehåll på ligninets löslighet i vatten undersöktes i en statistisk modell som gjordes i programvaran MODDE. Den statistiska modellens design, utförande och predikteringskapacitet utvärderades. En screeningundersökning utfördes för att identifiera hur de olika faktorerna påverkade lignets löslighet i vatten. Modellen i MODDE optimerades och kunde därefter användas som en predikterande modell inom undersökningens omfattning. Ultraljudssonikering användes för att skapa mikroemulsionen. Ett stabiliseringstest gjordes genom att de olika lignindieslarna placerades i provrör som observerades under tre veckors tid. Driftkostnaden i form av kemikaliekostnad och kostnad för konsumerad elektricitet under produktionen beräknades. En mikroemulsion kunde inte framställas. Dock skapades en emulsion mellan diesel och modifierat lignin. Den högsta halten av löst lignin i vatten var 99.77 %. pH-värdet under reaktionen var den faktor som påverkade ligninets löslighet mest. Vatteninnehållet i det modifierade ligninet påverkade också lösligheten samtidigt som reaktionstiden inte påverkade lösligheten nämnvärt inom det givna spannet. Den statistiska modellens design och utförande var tillfredställande och den prediktiva kapaciteten var mycket bra. Stabilitetstestet visade att en separation observerades i botten ett av lignindieselproverna efter 0.5 h. Efter en vecka observerades en liten färggradient i toppen av ett av provrören. Efter två veckor syntes samma sorts färggradient i alla lignindieselproverna. Inget av lignindieselproverna undergick fullständig fasseparation under the tre veckornas separationstest.

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Alcantara, Berenice Kussumoto de. "Experimental approaches to study the responses to Al stress in cultivated crops." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/11/11151/tde-10062014-105216/.

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This thesis was performed in the scope of International Graduation Program in which Universidade de São Paulo and The Ohio State University are inserted. In the first year of Ph.D. work we aimed to understand the effect of aluminum (Al) in root growth of Eucalyptus spp. and the relationship with biochemical parameters and transcriptional responses since there is little information about these responses for tree species. Aluminum is found naturally in the Earth crust, but under acidic conditions Al3+ ion becomes available and toxic to the plants. United States and Brazil possess large areas with Al toxicity and great area of forests growing under these conditions. In order to perform the transcriptional analysis, Eucalyptus RNA was transported to United States, however, the method of transportation was not efficient to guarantee RNA integrity. Therefore we changed our objectives and we performed new experiments using maize as biological system because this species has economical importance to U.S. and Brazil. Furthermore, substantial area of this crop is growing in soils under these conditions. In these experiments, we aimed to verify if pre-treating maize seeds before germination could be efficient to induce Al-tolerance in Al-sensitive genotypes. This thesis was organized in order to build a story based on the sequences of the experiments. In general, we obtained interesting results for Al-sensitive maize that presented reduction in lignin content and gene expression in shoots, also for Al-tolerant variety that present increase in growth, productivity and improvement of nutritional quality of the kernels.
Esta tese foi realizada no âmbito do Programa Internacional de Pós-Graduação em que a Universidade de São Paulo e The Ohio State University estão inseridos. No primeiro ano do trabalho de doutorado, o objetivo foi de compreender o efeito do alumínio (Al) no crescimento de raízes de Eucalyptus spp. e a relação com parâmetros bioquímicos e respostas de transcrição já que há pouca informação sobre estas respostas para espécies arbóreas. O alumínio é encontrado naturalmente na crosta terrestre, porém sob condições ácidas o íon Al3+ torna-se disponível e tóxico para as plantas. Os Estados Unidos e o Brasil possuem grandes áreas com Al tóxico e grandes áreas de florestas crescem sob estas condições. A fim de executar a análise transcricional, o RNA dos materiais de eucalipto foi transportado para os Estados Unidos, entretanto, o método de transporte não foi eficiente para garantir a integridade do RNA. Assim sendo, mudamos nossos objetivos e realizamos novos experimentos utilizando milho como sistema biológico, porque esta espécie tem importância econômica para os EUA e também para o Brasil. Ademais, substanciais áreas de cultivo do milho se encontram em solos sob estas condições. Nos novos experimentos realizados, o objetivo foi de verificar se o pré-tratamento de sementes de milho antes da germinação poderia ser eficiente para induzir tolerância ao alumínio em genótipos Al-sensíveis. Esta tese foi organizada a fim de construir uma história com base nas sequencias dos experimentos. Em geral, resultados interessantes foram obtidos para a linhagem de milho sensível ao Al que apresentou redução no teor de lignina e na sua expressão gênica em parte aérea, também para a variedade tolerante ao Al que apresentou aumento no crescimento, produtividade e melhoria da qualidade nutricional dos grãos.

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Yao, Soledad G. "OXIDATION OF β-O-4 LIGNIN MODEL COMPOUNDS AND APPLICATION TO LIGNIN LINKAGE DEGRADATION FACILITATED BY MECHANOCHEMICAL TREATMENT AND TWO-STEP OXIDATIVE DEPOLYMERIZATION." UKnowledge, 2018. https://uknowledge.uky.edu/chemistry_etds/91.

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The oxidation of lignin model compounds was studied in conventional solvents in parallel with oxidations in ionic liquid solvents. Catalyst systems were investigated in ionic liquid solvents to determine how reaction rates and the selectivity for benzylic carbon oxidation were affected. Oxidation rates were often lower in ionic liquids than in conventional solvents ‒ as indicated by lower conversion in a standard reaction time ‒ likely due, at least in part, to the higher viscosity of ionic liquids. Mechano chemical treatment of Indulin AT kraft lignin by ball milling with KOH and toluene produced significant carbonyl functionality, among other changes. The chemical reactivity of the lignin was increased, resulting in greater lignin degradation from porphyrin oxidation followed by Baeyer-Villiger oxidation. The mechanochemical treatment produced a level of lignin oxidation that was similar to that produced by porphyrin-catalyzed oxidation. Combining mechanochemical treatment with porphyrin oxidation produced a synergistic positive effect on the depolymerization of lignin, as demonstrated by a significantly higher yield of monomers. The methyl ester of vanillic acid was obtained as the main monomeric product (after methylation), along with a small amount of methyl 5-carbomethoxyvanillate.

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Napoly, Francois. "Étude de nouveaux systèmes catalytiques pour la valorisation de la lignine par oxydation." Thesis, Lyon 1, 2014. http://www.theses.fr/2014LYO10207/document.

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Le but de cette thèse a été de trouver de nouveaux systèmes catalytiques pour l'oxydation de la lignine. Dans ce but, deux stratégies ont été abordées : une méthodologie directe, où différents systèmes catalytiques à base de sels métalliques et de peroxydes d'hydrogène ont été testés. Dans ce cas, le système Na2WO4,2H2O/H2O2 s'est avéré le plus efficace en dépolymérisant la lignine avec des rendements modérés. Une méthodologie indirecte via l'utilisation de molécules modèles de la lignine. Dans ce cas, des catalyseurs plus complexes ont été évalués notamment le Fe(TAML)Li. Ce dernier en combinaison avec le DAIB comme oxydant a montré une activité intéressante avec les molécules modèles, mais décevante avec la lignine. Enfin cette thèse a permis d'évaluer l'activité du Fe(TAML)Li dans l'oxydation d'alcools et d'alcane benzyliques
The goal of the thesis was to find new catalytic systems for lignin oxidation. Two strategies were chosen to reach this objective: a direct methodology, which implied the test of different catalytic systems based on metal salts and hydrogen peroxide. In that case the system Na2WO4,2H2O/H2O2 permitted to obtain the best results, with moderate depolymerization yields. An indirect methodology through the use of lignin model compounds. In that case, more complex catalysts were tested. The system Fe(TAML)Li/DAIB implied the best results with model compounds, but quite disappointing with lignin. Finally, the thesis have permitted to evaluate the activity of Fe(TAML)Li for the oxidation of alcohols and benzylic alkanes

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Cabral, Almada Cédric. "Étude sur la dépolymérisation catalytique de la lignine en milieu oxydant : vers la production d’aromatiques biosourcés." Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10301/document.

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Ces travaux de thèse s'inscrivent dans le cadre du projet CHEMLIVAL qui vise à valoriser la lignine en composés aromatiques fonctionnalisés (fonction : aldéhydes, acides carboxyliques, phénols) pour des applications en chimie fine ou polymères. Pour ce faire, nous avons étudié la valorisation de la lignine par voie d'oxydation catalytique hétérogène en milieu alcalin, une méthodologie respectueuse de l'environnement, pour la production de composés aromatiques telle que la vanilline ou la syringaldéhyde. Précédés par une caractérisation poussée des lignines utilisées dans cette étude, une optimisation des paramètres de la réaction (température, pression, catalyseurs…) ainsi que des suivis cinétique ont été réalisés. Ainsi des résultats comparables, voire supérieurs, à ceux décrits dans la littérature ont été obtenus. Ces travaux ont montré que la nature de la lignine ainsi que le procédé d'extraction lié à celle-ci avaient une grande influence sur les rendements en composés aromatiques. De plus, les résultats obtenus ont permis de proposer un schéma réactionnel d'oxydation de la lignine. L'utilisation d'un catalyseur (Pt/TiO2) a montré un effet bénéfique sur les rendements en composés aromatiques, probablement via un nouveau mécanisme d'oxydation de la lignine métallo-initié qui reste encore à élucider
This work is part of the CHEMLIVAL project aiming at the lignin valorization into functionalized aromatics compounds (functions : aldehydes, carboxylic acids, phenols) for fine chemistry or polymer applications. With this in mind, we studied lignin valorization through heterogeneous catalytic oxidation in alkaline media, an environmental friendly approach, for the production of aromatic compounds such as vanillin or syringaldehyde. After an extensive characterization of the different lignin samples used, we proceeded to an optimization of the conditions parameters (temperature, pressure, catalysts…) and kinetics study. As a results, yields similar or even higher than those reported in the literature were obtained. This work demonstrated that the lignin source as well as its extraction process has a great influence over the aromatic yields. Furthermore, the results acquired allowed us to propose a reaction scheme for lignin oxidation. The use of a catalyst (Pt/TiO2) was found to be beneficial for the production of aromatic compounds probably due to metallo-initiated mechanism that still needs to be identified

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Nguyen, Mai Thanh Thi. "Synthesis and Oxidation of Lignin-Carbohydrate Model Compounds." Fogler Library, University of Maine, 2008. http://www.library.umaine.edu/theses/pdf/NguyenMTT2008.pdf.

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Wiegand, Ute. "Hydro- und geochemische Prozesse in oberflächennahen Kippensedimenten des Braunkohlentagebaus Zwenkau." Doctoral thesis, Universitätsbibliothek Leipzig, 2004. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-37367.

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Die vorliegende Arbeit wurde im Rahmen des BMBF-geförderten Projektes "Luft- und bodengestützte spektrometrische Untersuchungen zur Differenzierung reaktiv veränderter Braunkohlentagebaugebiete in Mitteldeutschland" (Vorhaben 02 WB 9667/5) als Kooperation zwischen dem GeoForschungsZentrum Potsdam (GFZ), dem Deutschen Zentrum für Luft- und Raumfahrt (DLR), der Gesellschaft für Angewandte Fernerkundung (GAF) und dem Umweltforschungszentrum Leipzig/Halle GmbH (UFZ) angefertigt. Grundidee des Projektes war es, die durch spektrometrische Erfassungsmethoden der Fernerkundung erhaltenen Überfliegungsdaten mittels konventioneller petrographischer, mineralogischer und geochemischer Analytik zu kalibrieren. Der Schwerpunkt dieser Arbeit lag dabei in der Charakterisierung der hydro- und geochemischen Veränderungen in den Kippensedimenten des im mitteldeutschen Raum südlich von Leipzig aufgeschlossenen Braunkohlentagebaus Zwenkau. Zu diesem Zweck wurden die Kippensedimente in Abhängigkeit des Schüttungsalters und der Lagerung untersucht sowie die spezifischen Merkmale der Kippenwässer und Bodengase erfaßt, um die im Kippenkörper ablaufenden chemischen, petrographischen und gefügemäßigen Veränderungen sowie die Wechselwirkungen zwischen den Sedimenten, Wässern und Bodengasen zu beschreiben. Schließlich wird ein Modell zur zeitlichen Entwicklung der Abraumförderbrückenkippe, beginnend bei ihrer Verkippung bis hin zu einem Alter von etwa 20 Jahren, vorgestellt, welches die beobachteten Erscheinungen bezüglich der auftretenden endogenen und exogenen Wechselwirkungsfaktoren gut erklärt
This thesis was prepared in cooperation with the GeoForschungsZentrum Potsdam (GFZ), the Deutsches Zentrum für Luft- und Raumfahrt (DLR), the Gesellschaft für Angewandte Fernerkundung (GAF), and the Umweltforschungszentrum Leipzig/Halle (UFZ) in frame of the project "Airborne and laboratory spectroscopic studies for differentiation of reactively alterated lignite mining pits in Central Germany" (No. 02 WB 9667/5) which was gratefully supported by the Bundesministerium für Bildung, Wissenschaft, Forschung und Technologie (BMBF). The major idea of the project was to achieve a calibration of the spectroscopic data acquired by the remote sensing though the results obtained from conventionally petrographical, mineralogical and geochemical analyses. The main goal of this thesis was the characterization of the hydro- and geochemical alterations in the conveyor bridge dump of the open lignite mining pit Zwenkau which is located in the Central Germany District southern of Leipzig. Therefore, dependent on their ages in terms of dumping and their surface-near locations the dump sediments were investigated and the specific properties of the different types of dump water and soil gases were acquired as well in order to describe the ongoing chemical, petrographical and structural alterations and interactions between the sediments, the water and the soil gases in the conveyor bridge. Finally, a model of the chronological development of the overburden sediments starting from their spilling up to an age of about 20 years is proposed which well explains the observed phenomena regarding the appearing endogenous and exogenous interaction factors

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Condassamy, Olivia. "Valorisation d'une lignine alcaline industrielle : vers le développement de nouveaux synthons et oligomères bio-sourcés issus de la lignine." Thesis, Bordeaux, 2015. http://www.theses.fr/2015BORD0265/document.

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La première partie de ce projet à consisté à isoler la lignine à partir de liqueurs industrielles et à la purifier pour s’affranchir des sucres, des minéraux et autres constituants. Pour cela, un protocole efficace en trois étapes a été proposé pour obtenir des échantillons de lignine avec une pureté satisfaisante (95%) et pour récupérer 68% de la lignine initialement présente dans la liqueur alcaline de départ. La lignine alcaline purifiée a ensuite été caractérisée d’un point de vue moléculaire et par analyses thermiques. L’élucidation de la structure de la lignine alcaline a permis d’appréhender sa fonctionnalisation par oxydation. Les analyses par chromatographie d’exclusion stérique de la lignine après oxydation ont montré une diminution de la masse molaire confirmant ainsi le clivage. Trois fractions différentes ont été isolées après l’oxydation de la lignine selon le solvant d’extraction ; d’une part des oligomères (plus ou moins fonctionnalisés) et d’autre part des molécules aromatiques (dont15% de vanilline). Ce travail de thèse aura abouti à la synthèse de composés aromatiques à haute valeur ajoutée (vanilline) et d’oligomères de lignine fonctionnalisés par des fonctions acide carboxylique. Les applications envisageables de ces « polyacides » issus de lignine sont nombreuses pour la formation de nouveaux polymères bio-sourcés tels que des polyesters, polyamides ou encore polyuréthanes
A valorization of alkaline lignin from an industrial pulping liquor has been proposed for this project. Before considering any chemical modification or potential applications, the lignin structure has been elucidated. An efficient three-steps protocol for extraction and purification of lignin from industrial liquor has been established. This protocol leads to high purity sample of lignin (95%) and allows the recovery (68%) of the lignin initially present in the alkaline liquor. Alkaline lignin has been characterized utilizing analytical methods and thermogravimetric analysis. This precise structure elucidation was critical for proceeding to chemical modification of alkaline lignin. Chemical modification of alkaline lignin has been done by oxidation in alkaline media. Three major oxidized products have been isolated depending on the extraction solvent: oligomers bearing carboxylic groups and aromatic molecules. This thesis work led to the synthesis of value-added bio-sourced chemicals and functionalized oligomers. The polyacids from lignin obtained should be studied to form new biobased polymers such as polyesters, polyamids or polyurethanes

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Musharah, Amani. "Gold-catalysed oxidation of lignin-derived building blocks." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/goldcatalysed-oxidation-of-ligninderived-building-blocks(ef60feb6-5bc8-40c8-95c9-eddd3175f8d1).html.

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The use of heterogeneous catalysts containing Au nanoparticles supported on TiO2 has been explored for oxidative aqueous phase transformations of sustainable phenolic and benzoic acid derivatives that can be obtained from lignin. Au/TiO2 catalysts were chosen because of their high activity for ambient pressure oxidations of gas phase species, and because their synthesis is facile and reproducible through a modified deposition-precipitation method. The aerobic oxidation of syringic, vanillic, and ferulic acid as well as of guaiacol, eugenol and anisole was investigated at temperatures up to 70°C under (i) atmospheric air sparging in an open reactor and (ii) at 10 atm air pressure in a closed reactor system. The catalysts were characterised by Transmission Electron Microscopy (TEM), Inductively Coupled Plasma (ICP) Optical Emission Spectroscopy and the reproducibility of their catalytic activity independently monitored by determining their activity for carbon monoxide oxidation in a gas flow reactor. The oxidation of syringic acid, vanillic acid, ferulic acid over Au/TiO2 resulted in the formation of 2,6-dimethoxy benzoquinone, guaiacol, and vanillin, respectively, indicating high selectivity for decarboxylation followed by selective oxidation at the position releasing the leaving group. Guaiacol was found to form tetraguaiacol, while eugenol produced quinone methide. Generally, higher air pressure strongly accelerated the transformations, indicating that availability of oxidants formed from O2 is the rate limiting step in the observed transformations. No transformations took place when O2 was excluded from the systems. Overall, guaiacol was found to react fastest, followed by syringic acid, ferulic acid, then vanillic acid. Anisole was found to be unreactive, even at elevated air pressure. The overall reaction pattern emerging from these studies is that the aerobic oxidation in the presence of Au/TiO2 mimics known biotransformations, for example peroxidase-catalysed oxidations involving H2O2.To assess how the functional groups on the aromatic ring influence reactivity the oxidation of p-hydroxybenzoic acid and of 2,6-dimethoxybenzoic acid was also assessed. It was found that decarboxylation of p-hydroxybenzoic acid proceeds, albeit rather slowly, forming phenol, with no further oxidation to hydroquinone or benzoquinone. Taken together these results indicate that the methoxy moieties influence reactivity through both their inductive and resonance effects: leaving of the carboxylic acid group appears to be enhanced through the inductive effect, while further oxidation at the phenolic site seems to be activated through the resonance effect in ortho-position. In line with this hypothesis, it was recently found that dimethoxybenzoic acid converts fast.

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Ghahremani, Raziyeh. "Electrochemical Oxidation of Lignin for the Production of Value-added Chemicals." Ohio University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1603983239429615.

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Kovur, Srinivasulu Raju. "Synthesis and Enzymatic Oxidation of Model Lignin Carbohydrate Complexes." Fogler Library, University of Maine, 2008. http://www.library.umaine.edu/theses/pdf/KovurSR2008.pdf.

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Kieffer, Raphaëlle. "Développement de nouveaux catalyseurs pour la dépolymérisation de la lignine par voie d’oxydation." Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10124/document.

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La lignine est l'un des biopolymères les plus importants sur Terre. Elle est extraite des plantes et représente la plus grande source de noyaux aromatiques dans la biomasse. De nombreux projets ayant pour but la dépolymérisation de la lignine en molécules de faibles poids moléculaires, valorisables par les industries chimiques, sont de plus en plus développés au vu du fort potentiel de cette bio-ressource. Le but de notre projet était de développer un nouveau système catalytique pour la dépolymérisation de la lignine. Nous nous sommes intéressés à la conception de nouveaux catalyseurs homogènes et hétérogènes, basés sur la structure connue du complexe Fe(TAML). Nous avons étudié leurs réactivité et stabilité en conditions de catalyse oxydante, et les avons comparés aux caractéristiques du Fe(TAML) existant. Pour ce faire, l'étude catalytique a été réalisée sur des molécules modèles de la lignine, dans le but d'éviter les problèmes analytiques liés à la structure du polymère. Dans un premier temps, nous présenterons la stratégie de fonctionnalisation du ligand TAML connu afin d'obtenir de nouveaux complexes qui puissent être greffés sur un support de silice. Dans un deuxième temps, nous parlerons des résultats de la catalyse oxydante en conditions homogènes et hétérogènes, et de l'influence du changement de la structure des ligands sur l'activité des catalyseurs
Lignin is one of the most abundant biopolymers on earth. It is issued from plants and represents the largest source of aromatics in biomass. Projects aiming at depolymerizing lignin to obtain value-added small molecules for the chemical industry are more and more developed due to the high potential of this bio-resource. The goal of our project was to develop a new catalytic system for the depolymerization of lignin. We have been interested in designing new homogeneous and heterogeneous catalysts based on the known structure of the Fe(TAML) complex. We have studied their reactivity and stability under oxidative catalysis conditions, and have compared them to the characteristics of the existing Fe(TAML). To do so, the catalysis study has been realized on lignin small model molecules to avoid the analytical problems related to a polymer backbone. In a first hand, we will present the strategy of functionalization of the known TAML ligand to design new complexes to be grafted on a silica support. In a second hand, we will talk about the results of oxidative catalysis in homogeneous and heterogeneous conditions, and the influence of the ligand structure change on the activity of the catalysts

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14

Ferreira, Júnior Domingos da Costa. "Teor de lignina e respostas antioxidantes de milho forrageiro sob estresse salino e ácido salicílico exógeno." Universidade Estadual Paulista (UNESP), 2018. http://hdl.handle.net/11449/153822.

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Muitos estudos apontam que o ácido salicílico (AS) está envolvido na adaptação de plantas a estresses abióticos. Entretanto, pouco se sabe sobre a ação deste hormônio na síntese de importantes metabólitos secundários em condições de estresse, como a lignina. Para tanto, foram estudados neste trabalho os efeitos de AS exógeno no crescimento, lignificação, metabolismo antioxidativo, acúmulo de osmólitos compatíveis e acúmulo de Na+ e macronutrientes em folhas de milho sob concentrações crescentes de NaCl. O delineamento experimental utilizado foi o inteiramente casualizado em esquema fatorial 2x4, representado pelas concentrações de AS (0,0 e 0,5 mM) e concentrações de NaCl (0, 50, 100 e 150 mM). As plantas foram submetidas aos tratamentos no estádio fenológico V4 (quatro folhas completamente desenvolvidas), enquanto que as avaliações foram realizadas no estádio V6 (seis folhas completamente desenvolvidas). Foram avaliados os seguintes parâmetros na parte aérea: área foliar, massa seca, teor de lignina, peroxidação lipídica, teor de peróxido de hidrogênio (H2O2), atividade enzimática da superóxido dismutase (SOD) e catalase (CAT), teor de prolina (Pro) e glicina betaína, relação Na+/K+ e teor de macronutrientes (N, P, Ca, Mg, S). O estresse salino reduziu o crescimento da parte aérea da planta, além de induzir maior acúmulo de Pro e GB, peroxidação lipídica, atividade da CAT e lignificação foliar. A adição de AS à solução nutritiva atenuou o efeito da salinidade sobre o crescimento vegetal até a concentração de 100 mM de NaCl, o que pode estar relacionado à maior lignificação, aumento na atividade da SOD e teores de Pro e H2O2, maior teor de N e Ca, além de reduções nos níveis foliares de Na+ e peroxidação de lipídios. Dessa forma, conclui-se que o AS exógeno atenua os efeitos deletérios de estresse salino baixo e moderado por três vias: maior lignificação foliar, o que pode se relacionar à maior produção de H2O2; menor peroxidação lipídica, relacionada à maior atividade de SOD; e menor teor foliar de Na+, aliado a aumento nos teores de Ca2+ e N.
Several studies demonstrate that salicylic acid (AS) is involved in the adaptation responses of plants to abiotic stresses. However, not much is known about the action of this hormone on the synthesis of important secondary metabolites, as lignin. For this purpose, in this work it was assessed the effects of exogenous application of SA on the growth, lignification, antioxidant metabolism, compatible osmolytes content, and concentration of Na+ and in maize leaves under increasingly NaCl concentrations. It was adopted a completely randomized design and a 2x4 factorial layout, representing SA concentrations (0.0 and 0.5 mM) and NaCl concentrations (0, 50, 100 and 150 mM) in hydroponics. Plants were exposed to the treatments at the V4 phenological stage (with four completely developed leaves), and evaluations were performed at V6 stage (six completely developed leaves). The following parameters were assessed on shoots: leaf area, dry weight, lignin content, lipid peroxidation, enzymatic activity of superoxide dismutase (SOD) and catalase (CAT), proline (Pro) and glycinebetaine (GB) contents, Na+ /K+ ratio and macronutrients concentration (N, P, Ca, Mg and S). Salt stress impaired shoot growth, also inducting higher accumulation of Pro and GB, lipid peroxidation, CAT activity, leaf lignification and also lower content of all evaluated nutrients. The application of AS alleviated the deleterious effects of salinity on maize shoot growth until 100 mM of NaCl, what can be related to an enhancement of SOD activity, lignin, proline and H2O2 contents, higher N and Ca contents, as to lower lipid peroxidation and Na+ content. This way, it is concluded that exogenous AS mitigates the negative effects of low and moderate salt stress on maize through three main ways: higher leaf lignification, which can be correlated with higher H2O2; lower lipid peroxidation, explained by higher SOD activity; and lower Na+ content, followed by increased leaf contents of Ca2+ .

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Galkin, Maxim. "Palladium-catalyzed lignin valorization : Towards a lignin-based biorefinery." Doctoral thesis, Uppsala universitet, Syntetisk organisk kemi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-265315.

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The work described in this thesis focuses on the cleavage of the β-O-4′ bond, which is the most abundant interunit linkage in the lignin polymer. In the first part, three methods based on palladium catalysis have been developed and their applicability has been verified using lignin model compounds. A transfer hydrogenolysis of the β-O-4′ bond using formic acid as a mild hydrogen donor together with a base. An aerobic oxidation of the benzylic alcohol motif in the β-O-4′ linkage to generate a key intermediate in the cleavage reaction was performed. A redox neutral cleavage of the β-O-4′ bond was accomplished in which no stoichiometric reducing or oxidizing agents were added. In the second part of the thesis, a mechanistic study is presented. The corresponding ketone from a dehydrogenation reaction of the benzylic alcohol motif was identified to be the key intermediate. This ketone and its enol tautomer was found to be responsible for the β-O-4′ bond cleavage reaction under the employed reaction conditions. In the final part of this thesis, the methodologies have been applied to native lignin. The depolymerization reaction was combined with organosolv pulping. This approach was successful, and together with cellulose and hemicellulose, propenyl aryls were generated in excellent yields directly from wood. In this transformation, the lignin derived molecules have been reduced by an endogenous hydrogen donor from the wood.

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Chen, Wei-Ching. "Selective Oxidation of Lignin Models and Extracts with Earth-Abundant Transition Metals and Hypervalent Iodine." Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/32181.

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As a significant component of lignocellulosic biomass, lignin represents a potential source of value-added aromatic chemicals. In this thesis, catalytic systems with earth-abundant metal catalysts such as molybdenum(VI) and hypervalent iodine complexes were developed to selectively break down lignin models into lower molecular weight chemicals under mild conditions. Due to the complexity of lignin, simple lignin model substrates (A to E), representing common linkages in lignin, were used to investigate the catalytic activity/selectivity of these catalysts. With the molybdenum catalysts [7– 11]/SPC/Adogen®464 system (SPC = sodium percarbonate), oxidation of simple β-1 model compound A in acetonitrile showed primarily C-H bond cleavage to form the ketone product, benzoin methyl ether, whereas the Cα-Cβ bond cleavage product, methyl benzoate, was obtained by switching the reaction solvent to benzonitrile. Preference for generating the Cα-Cβ bond cleavage product, i.e. benzaldehyde, can also be achieved with other early to middle transition metal catalysts using H2O2(aq) as the terminal oxidant. Stoichiometric amounts of hypervalent iodine/Lewis acid systems [20a-c] were able to selectively cleave Cα-Cβ bonds to aldehydes with both simple β-1 model compound A and β-O-4 model compound C. In contrast, other lignin model compounds with different linkages were unable to be oxidized to a great extent using these Mo- or iodine-based complexes. The catalytic activity and selectivity of the reported vanadium complexes, copper salts and non-metal system 1-5 on non-volatile organosolv (NVO) lignin was investigated under basic condition. Details of the depolymerisation of lignin were determined by using Gel Permeation Chromatography (GPC) and the two-dimensional NMR technique, quantitative HSQC (q-HSQC) spectroscopy. Vanadium [2] and copper systems were found to be the most active for depolymerization of NVO lignin.

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Lee, Oh-Kyu. "Mechanistic Studies of the Oxidation of Lignin and Cellulose Models." Fogler Library, University of Maine, 2003. http://www.library.umaine.edu/theses/pdf/LeeO2002.pdf.

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18

Mobley, Justin K. "TOWARDS CATALYTIC OXIDATIVE DEPOLYMERIZATION OF LIGNIN." UKnowledge, 2016. http://uknowledge.uky.edu/chemistry_etds/59.

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Lignin is one of the most abundant and underutilized biopolymers on earth. Primarily composed on three monolignol units (sinapyl, coniferyl, and p-coumaryl alcohol), lignin is formed through a radical pathway resulting in an assortment of linkages, of which the β-O-4 linkage is the most prevalent (up to 60% in some hardwood species). In planta, lignin plays an important role in water transport and in protecting plants from chemical and biological attack. Traditional attempts to depolymerize lignin have focused on the cleavage of β-O-4 linkages via thermal or reductive routes. However these pathways lead to low-value, unstable product mixtures. Moreover, typical product yields are low and the highly corrosive reaction medium results in added expense. More recently, catalytic oxidations have been studied as a viable means to lignin utilization. The present work will review the state-of-the-art of lignin oxidations, and focus on stoichiometric and catalytic attempts to oxidize lignin and lignin model compounds in order achieve selective stepwise depolymerization of lignin. Specifically, activated dimethyl sulfoxides and LDH catalysts were evaluated for lignin and/or lignin model compound oxidations leading, in some cases, to unexpected products.

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Díaz-Urrutia, Christian. "Vanadium-Catalyzed Aerobic Oxidation of Diols and Lignin Models/Extracts." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/35102.

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As the world moves forward to the development of biorefineries, the interest to replace chemicals and materials derived from petroleum is increasing exponentially. Lignin is a macromolecular by-product derived from the wood pulping industry, mainly used for heating purposes. The development of new processes to produce high value-added lignin products such as multifunctional aromatic chemicals and high-tech carbon materials are required to fulfill the needs for biorenewable feedstocks. Such processes are likely to include selective oxidation catalysis. The aim of this Thesis is to advance the state-of-the-art for the oxidation of lignin models and lignin extracts using homogeneous catalysts based on vanadium, an inexpensive and abundant transition metal, using air as the only oxidant. Lignin models containing the most important features of lignin (e.g., β-O-4 and β-1 linkages) were initially used to assess the catalytic potential. Previously reported (HQ)2V(O)(OiPr) and (dipic)V(O)(OiPr) catalysts (dipic = dipicolinate and HQ = 8-oxyquinoline) displayed different selectivity for C-H, C-O and C-C bond cleavage upon varying of the solvent, the lignin model or the catalyst. Moreover, these catalysts cleave the C-H bond of secondary alcohols through a two-electron oxidation process and the C-C bond cleavage of the oxidation product ketone in the presence of exogenous base. Several amine bis(phenolate) oxovanadium(V) catalysts were synthesized and fully characterized, and demonstrated very good activity for the oxidation of lignin models and the depolymerization of organosolv lignin. These new catalysts overcome the need for added base, display higher reaction rates of oxidation, and improve the selectivity for the disassembly of lignin models. The different selectivities involving C-H vs. C-O vs. C-C bond cleavage are discussed together with a novel redox-neutral C-C bond cleavage of lignin model 1,2-diphenyl-2-methoxyethanol. The oxovanadium(V) catalysts, along with a metal-free variant and other transition metal catalysts, were employed to assess their performance for the oxidation and depolymerization of organosolv lignin. Although most catalysts oxidized the lignin extracts, the oxovanadium(V) complexes demonstrated the highest degree of lignin depolymerization as shown by Gel Permeation Chromatography (GPC), quantitative-Heteronuclear Single Quantum Correlation (q-HSQC) and quantitative 31P NMR spectroscopy of derived phosphite esters. In a complementary study, oxovanadium(V) catalysts also established their utility for the valorization of cellulose-derived substrates (e.g., diols). Two trialkoxyamine oxovanadium(V) complexes bearing a triethoxyamine and tris[2-(3,5-di-tert-butyl-phenoxy)methyl]amine ligand respectively, selectively cleaved the C-C bond in 1,2-diols with excellent rates and using air as the only oxidant. In a stoichiometric investigation of this reaction, it was determined that the transformation proceeds through an unusual direct oxidative two-electron cleavage of diols, affording a non-oxo monometallic V(III) intermediate. DFT calculations support a single-site proton-coupled electron-transfer of the hydroxyl hydrogen to the V oxo orbital. In summary, this Thesis describes new developments in vanadium catalysis such as mechanistic implications and catalyst optimization for the valorization of lignocellulosic biomass utilizing air as an oxidant.

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Pedersen, Nicolai. "Oxidation of veratryl alcohol with lignin peroxidase and nanoscale photosystems." Thesis, Uppsala universitet, Institutionen för kemi - BMC, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-355159.

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Gambarato, Bruno Chaboli. "Estabelecimento e validação de modelos de oxidação de ligninas." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/97/97131/tde-26092012-151744/.

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Neste trabalho, foram desenvolvidos modelos matemáticos fenomenológicos capazes de descrever a cinética de oxidação química e enzimática de ligninas de palha e bagaço de cana, obtidas por diferentes processos. A oxidação química foi realizada utilizando-se lignina de bagaço de cana obtida por explosão a vapor e por polpação Acetosolv. As reações se processaram em 4 temperaturas (50, 70, 90 e 115 °C) e o fluxo de oxigênio foi mantido constante a 60 mL/min. O meio reacional foi composto por 0,5 g de lignina, 100 mL de ácido acético glacial, 1,6 mL de HBr (47% p/v), 0,05 g de acetato de manganês (II), 0,42 g de acetato de cobalto (II) e 10 mL de anidrido acético. A cinética da reação foi acompanhada por medida de absorbância a 280nm. O modelo foi proposto considerando a cinética de ordem n e incorporando a equação de Arrhenius, que relaciona a constante de velocidade com a energia de ativação e a temperatura do sistema. A integração dos modelos foi feita utilizando-se o método de Runge-Kutta de quarta ordem e o ajuste dos parâmetros foi realizado segundo o método de Levenberg-Marquardt. A validade estatística do ajuste dos modelos foi avaliada pelo método de análise de variância. Os valores de energia de ativação obtidos foram 9099 ± 947 J/mol para a lignina de explosão a vapor e 785 ± 55 J/mol para a lignina acetosolv. A constante cinética K apresentou valor 6,62 ± 1,3 para a lignina de explosão a vapor e 0,0184 ± 0,0035 para a lignina acetosolv. A ordem de reação encontrada foi 1,22 ± 0,12 para a lignina de explosão a vapor e 1,19 ± 0,06 para a lignina acetosolv. A oxidação enzimática foi realizada utilizando lignina de palha e bagaço de cana e 4 extratos enzimáticos: extrato de maçã, extrato de maçã reutilizado, extrato de batata e enzima comercial NOVOZYM 51003. As reações se processaram em solução tampão fosfato 50 mmol/L (pH 7,6) e 1,4-dioxano, 3:1(v/v), no volume total de 30 mL. Foram utilizados 300 mg de lignina, 15 mL de extrato enzimático, 0,1% de glicerol e 30 mL/min de O2. A cinética da reação foi acompanhada pela medida de absorbância a 265, 280 e 320nm. O modelo foi proposto com base na cinética de Michaelis-Menten e foi capaz de reproduzir os dados experimentais. A consideração da cinética enzimática forneceu valores de correlação melhores que os obtidos em outros trabalhos, que não consideraram a cinética enzimática na modelagem. A formação dos grupos -carbonílicos, monitorada a 280nm, foi, em geral, a reação que apresentou maior constante de velocidade. Foi observado que o binômio C-ks é importante para a cinética da reação e a reação enzimática que apresentou maior afinidade enzima-substrato foi a de formação de grupos carboxílicos, monitorada a 320nm, para a oxidação com extrato de maçã. A oxidação enzimática da lignina de bagaço apresentou comportamento cinético diferente da lignina de palha, evidenciando que há diferenças estruturais entre essas ligninas não elucidadas ainda.
This work proposed phenomenological mathematical models capable of describing chemical and enzymatic oxidation kinetics of sugarcane straw and bagasse from different processes. Chemical oxidation was realized using sugarcane bagasse lignin obtained by steam explosion and acetosolv pulping. The reactions were carried out under 4 different temperatures (50, 70, 90 and 115 °C) and the oxygen flux was maintained constant at 60 mL/min. The reaction medium was formulated using 0.5 g lignin, 100 mL glacial acetic acid, 1.6 mL HBr (47% w/v), 0.05 g manganese acetate (II), 0.42 g cobalt acetate (II) and 10 mL acetic anhydride. The reaction kinetics was followed by absorbance measurements at 280 nm. It was proposed a model considering n-order kinetics and incorporating Arrhenius equation, which relates rate constant to activation energy and system temperature. Models integration was made using fourth-order Runge-Kutta method and parameters adjustment was realized according to Levenberg-Marquardt method. The statistical validity of model adjustments was assessed using analysis of variance method. For activation energy, the values obtained were 9099 ± 947 J mol-1 for steam explosion lignin and 785 ± 55 J mol-1 for acetosolv lignin. The kinetic constant K obtained was 6.62 ± 1.3 for steam explosion lignin and 0.0184 ± 0.0035 for acetosolv lignin. The reaction order found was 1.22 ± 0.12 for steam explosion lignin and 1.19 ± 0.06 for acetosolv lignin. Enzymatic oxidation was realized using sugarcane straw and bagasse and 4 enzyme extracts: apple extract, recovered apple extract, potato extract and commercial enzyme NOVOZYM 51003. The reactions were carried out in phosphate buffer solution 50 mmol L-1 (pH 7.6) and 1,4-dioxane, 3:1 (v/v), in a 30 mL total volume. The medium composition was 300 mg lignin, 15 mL enzyme extract, 0.1% glycerol and 30 mL/min O2. The reaction kinetics was followed by absorbance measurements at 265, 280 and 320 nm. The model proposed was based on Michaelis-Menten kinetics and it was able to reproduce the experimental data. The consideration of the enzyme kinetics in modeling provided better correlation values than those from other works, which do not consider enzyme kinetics. Formation of -carbonyl groups, monitored at 280 nm, was generally the reaction that presented the higher rate constant. It was observed that the binom C-ks is important for reaction kinetics; the enzyme reaction that showed the greatest enzyme-substrate affinity was that one responsible for carboxyl groups formation, monitored at 320 nm, for recovered apple extract. Enzymatic oxidation of bagasse lignin presented a different kinetic behavior from straw lignin, providing evidences that there are differences between these two lignins that still remain unclear.

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Salehi, Movahed Alireza. "Effect of Wood Constituents Oxidation of Unsaturated Fatty Acids." Licentiate thesis, KTH, Fiber- och polymerteknik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-33129.

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This work presents the mechanisms of free radicals in a model system between fatty acids oxidation process and wood components. The aim is to create a better understanding of new environmentally friendly materials for exterior wood protection. The drying mechanisms of the unsaturated fatty acids with wood model system in the real time were monitored by using RT-IR. This method together with SEC and NMR are enormously powerful spectroscopy techniques to determine the physical and chemical properties of fatty acids-wood during the oxidation process over time. In the first part of this study the focus was in a molecular level on oxidation of methyl linoleate mixed with lignin model compounds (1 and 20 wt%). The effect of lignin structures on unsaturation fatty acids oxidation was determined with 1 wt% lignin model compounds. The interaction, coupling reaction and new structure formations were analyzed through 20 wt% of same lignin compounds mixed with 80 wt% methyl linoleate. The oil oxidation interaction mechanisms were also evaluated by using methyl linoleate, methyl oleate and Linola® on real/natural wood (Norwegian Spruce). In the second part of this work, FT-IR and different NMR methods were used as characterization techniques. The results showed that the oxidative drying process of unsaturated fatty acids was indeed affected by wood constituents. The most hydrophobic part of the wood; lignin, interacted with the oxidation process and some lignin structures inhibited or retarded the reaction. Not only the oil structures were affected but also the lignins were to some extent oxidized as a competing reaction with the oil oxidation. However, a formation of chemicals bonds between the oil and the lignin structures was not observed, i.e. the oils were not immobilized on lignin by covalent bond formation to any significant extent. Further, the focus was on oils in wood using NMR and FTIR demonstrated that highly reactive linoleic acid did react in wood significantly, while it was not immobilized to the same extent. Oleic acid on the other hand reacted more sluggish but the reactive part was immobilized in the wood structure. According to the results, it can be concluded that the structure of the oil is crucial in the overall protective performance of the system. This study indicated that the oxidation pattern of fatty acids behaved differently on wood surface. The wood model compounds minimize the complexity of all elements that exist normally in the natural wood. It can also be concluded that different wood components e.g. end group structures, affect the oil drying process in different ways. The fatty acids pattern will affect not only the structure of the oil dried itself but also the surrounding wood materials.
Detta arbete beskriver friradikalmekanismerna i ett modellsystem mellan fettsyra oxidation och träs beståndsdelar för att skapa bättre förståelse för nya miljövänliga skyddssystem gällande trämaterial som används utomhus. Torkningsmekanismen av omättade fettsyror med trä modellsystem analyserades med hjälp av RT-IR i realtid. Denna metod tillsammans med SEC och NMR spektroskopier understödjer undersökningen av de fysikaliska och kemiska förändringarna av olja och träkomponenter under oxidationsprocessen. I den första delen av denna studie blandades metyl linoleate med ligninmodellföreningar (1 och 20 vikt%). Effekten av olika ligninstrukturer på omättade fettsyrors oxidation, bestämdes med 1vikt% ligninmodellföreningar. Samverkan och kemiska kopplingsreaktioner analyserades med 20 vikt% ligninföreningar genom att dessa kemikalier blandades med metyl linoleate (80 vikt%). Den andra delen av denna studie genomfördes på oljor som oxiderades på trä (gran). Detta genomfördes med hjälp av metyl linoleate, metyl oleat och Linola® på trä. FT-IR och olika NMR karaktäriseringsmetoder användandes i den sista delen av detta arbete. Resultaten visar ett flertal nya faktorer rörande den kemiska och fysikaliska samverkan mellan impregnerande olja och trä som har betydelse för ett optimalt fungerande skydd. Modellstudier mellan torkande oljor och olika ligninkomponenter visar att det sker en kemisk samverkan mellan ligninet och oljorna under oxidationsprocessen. En mycket viktig faktor är att oljan oxideras men att även en del av ligninstrukturerna förändras kemisk under denna process. Slutsatsen är att ligninet påverkar torkhastigheten hos oljan men att oxidationen av oljan också påverkar nedbrytning av ligninet. Studierna visar dock att ingen mätbar mängd olja reagerar kemisk med lignin dvs. oljan fastnar inte genom en kemisk koppling till lignin. NMR studier visar att olika oljor i trä är olika reaktiva, exempelvis reagerar linolja snabbt men merparten av dessa oxidationsreaktioner leder inte till att oljan immobilseras på en molekylär nivå. Mindre reaktiva oljor å andra sidan (exempelvis oljor med hög oljesyrahalt) torkar långsammare men att detta leder till att en större andel immobiliserad olja. Genom att använda trämodellföreningar minimeras komplexiteten av alla element som normalt finns i trä. Från denna studie kan man dra slutsatsen att olika träkomponenter, t.ex. olika kemiska strukturer påverkar olja torkningsprocessen på olika sätt. Fettsyrans kolkedjor påverkar inte bara oljans struktur under sin torkningsmekanism utan även det omgivande trämaterialet.
QC 20110429

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Jennings, John Adam. "HETEROGENEOUS BASE METAL CATALYZED OXIDATIVE DEPOLYMERIZATION OF LIGNIN AND LIGNIN MODEL COMPOUNDS." UKnowledge, 2017. http://uknowledge.uky.edu/chemistry_etds/81.

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With the dwindling availability of petroleum, focus has shifted to renewable energy sources such as lignocellulosic biomass. Lignocellulosic biomass is composed of three main constituents, lignin, cellulose and hemicellulose. Due to the low value of cellulosic ethanol, utilization of the lignin component is necessary for the realization of an economically sustainable biorefinery model. Once depolymerized, lignin has the potential to replace petroleum-derived molecules used as bulk and specialty aromatic chemicals. Numerous lignin depolymerization strategies focus on cleavage of β-aryl ether linkages, usually at high temperatures and under reductive conditions. Alternatively, selective benzylic oxidation strategies have recently been explored for lignin and lignin models. In this work, heterogeneous catalytic methods using supported base metals and layered-double hydroxides were evaluated for the oxidation of lignin models both before and after benzylic oxidation. Additionally, by studying putative reaction intermediates, insights were gained into the mechanisms of oxidative fragmentation of the model compounds. Generally, it was found that after benzylic oxidation models were more susceptible to oxidative fragmentation. Indeed, several heterogeneous oxidation systems were found to convert lignin models to oxygenated aryl monomers (mainly benzoic acids and phenols) using inexpensive primary oxidants (i.e., hydrogen peroxide and molecular oxygen). Reactions were conducted at relatively mild temperatures and at low oxygen concentrations for the purpose of an easy transition to large-scale experiments. Finally, the catalytic systems that resulted in significant cleavage of lignin models were applied to a Kraft lignin. Oxidation of Kraft lignin resulted a mixture of products for which analytical data and increased solubility are consistent with interunit cleavage within the lignin macromolecule.

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Rinesch, Torsten [Verfasser]. "Oxidative Spaltung von Lignin und Lignin-Modellverbindungen und Funktionalisierung der Spaltprodukte / Torsten Rinesch." München : Verlag Dr. Hut, 2019. http://d-nb.info/1181514312/34.

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25

Violette, Steven M. "Oxygen Delignification Kinetics and Selectivity Improvement." Fogler Library, University of Maine, 2003. http://www.library.umaine.edu/theses/pdf/VioletteSM2003.pdf.

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Camus, Martin. "Dépolymérisation oxydante d'une lignine alcaline et sa valorisation." Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0394.

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Dans un contexte de développement durable, l’intérêt pour la biomasse et les matières lignocellulosiques est grandissant. La lignine possède une structure chimique unique avec un squelette aromatique et une variété de groupements fonctionnels, devenant ainsi une potentielle matière première pour remplacer les produits dérivés du pétrole. Cependant cette structure complexe ainsi que sa solubilité limitée freine son utilisation directe et constituent un réel défi. Ces travaux de thèse proposent une nouvelle voie de valorisation d’une lignine alcaline. En effet, des modifications, celles portant sur les fonctions hydroxyles et phénols, permettent entre autre de moduler sa solubilité dans différents solvants et à différents pH, augmentant de ce fait la gamme d’application potentielles. Pour cela, une dépolymérisation oxydante (par oxygène ou air) d’une lignine alcaline de type lignoboost a été réalisée dans le but d’obtenir des fractions de lignine enrichies en fonctions acide carboxylique (initialement peu présentes sur la structure de la lignine). Dans la première partie, les différents paramètres réactionnels (nature du gaz oxydant, pression, température et type de réacteur utilisé) ont été optimisés dans le but d’obtenir les meilleurs rendements en fraction précipitée et hydrosoluble de lignine oxydée, tout en maximisant le taux de fonctions acide carboxylique. Cette oxydation a également généré des oligomères de lignine de plus faible masse molaire, améliorant les propriétés de solubilité de ces derniers (notamment pour la fraction hydrosoluble indépendamment pH). L’impact de cette nouvelle fonctionnalisation a ensuite été étudié dans le but de valoriser ces oligomères. Les propriétés tensioactives et antioxydantes, mettant en avant la structure et les fonctions de la lignine, ont été comparées à celles de la lignine native et lignosulfonates. La réalisation de nouveaux films anti-UV dans une matrice HPMC-Lignine a, quant à elle, permis d’exploiter les nouvelles solubilités de la lignine hydrosoluble
In a context of sustainable development, biomass and lignocellulosic materials are benefiting from a growing interest. Lignin has a unique chemical structure with aromatic backbone and a variety of functional groups, becoming a potential feedstock to substitute petroleum-based products. However, this complex structure and its limited solubility hinder its direct use. Those observations make lignin challenging. This work aims at valorizing alkaline lignin. Indeed, modifications, those concerning the hydroxyls and phenol functions, allow to modulate its solubility in various solvents and in various pH, increasing the range of potential applications. In this purpose, an oxidative depolymerization (by oxygen or air) of a lignoboost-type alkaline lignin have been realized to obtain lignin fraction enriched with carboxylic acid functions (the content of which is very low amount in the native lignin structure). In the first part, different reaction parameters (the nature of the oxidative gaz, pressure, temperature and reactor type used) have been optimized to increase the final yields in precipitated and hydrosoluble fractions, while maximizing the carboxylic acid ratio. This oxidative reaction also generated lignin oligomers of lower molecular weight, thus improving their solubility properties (especially for the hydrosoluble fraction which is water-soluble at any pH). The impact of this new functionalization have been studied to valorize these oligomers. Surfactants and antioxidant properties, taking advantage of lignin structure and functions, have been compared to alkaline lignin and lignosulfonates. The development of new blocking-UV films in a HPMC-lignin matrix allowed to achieve new solubility properties for the hydrosoluble lignin

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Nunes, Andreia. "Hybrid mesoporous materials for the oxidative depolymerization of lignin into valuable molecules." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1024.

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La lignine est un des polymères naturels les plus abondants et le seul constituant de la biomasse basé sur des unités aromatiques et, à ce titre, représente une ressource renouvelable prometteuse pour la production durable de molécules organiques plus complexes. Les travaux de cette thèse portent sur le développement de matériaux catalytiques capables de transformer sélectivement la lignine en molécules fonctionnelles de base, hautement oxygénées, et l'étude de leur mise en oeuvre en condition alcaline oxydante en utilisant le peroxyde d'hydrogène comme donneur d'oxygène. Différentes familles de matériaux hybrides de type SBA-15 à base de titane, Au/titane, Ag/titane et Fe(TAML) ont tout d'abord été synthétisées et entièrement caractérisées. Des études catalytiques comparatives ont ensuite été réalisées afin d'évaluer leurs performances en termes de degré de dépolymérisation et distribution de produits. Le catalyseur présentant le plus fort potentiel, le matériau TiO2 supporté sur SBA-15, a ensuite été soumis à des études de réactivité plus poussées afin d'optimiser les différents paramètres réactionnels (température, temps de réaction et quantité d'oxydant) permettant d'atteindre en présence d'un excès d'oxydant jusqu'à 90 %pds de conversion de la lignine et à 80°C un rendement en bio-huile de 50%pds constituée principalement d'acides carboxyliques et molécules aromatiques potentiellement valorisables
Lignin is one of the most abundant natural polymers and the only biomass constituent based on aromatic units and as such represents a promising renewable resource for the sustainable production of complex organic molecules. This dissertation reports on the development of catalytic materials capable of selectively transform lignin into basic functional molecules with high oxygen content and the study of their performance under alkaline oxidative conditions, using hydrogen peroxide as oxygen donner. Different families of hybrid materials based on the SBA-15 scaffold were first synthesized by incorporation of titanium, Au/titanium, Ag/titanium and Fe-TAML and completely characterized. Comparative catalytic studies were then accomplished in order to evaluate their performance in terms of degree of depolymerization and product distribution. The catalyst with the highest potential, the TiO2 based SBA-15 material, was then submitted to further reactivity studies in order to optimize the different reaction parameters (temperature, reaction time and quantity of oxidant). In the presence of an excess of oxidant, conversions up to 90 wt. % were obtained, whereas a temperature of 80 °C allowed to obtain a yield in bio-oil of 50 wt. %, which is mainly composed of carboxylic acids and aromatic molecules with potential to be further valorized

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Constant, Sandra. "De l'extraction de la lignine à sa valorisation." Thesis, Montpellier, Ecole nationale supérieure de chimie, 2012. http://www.theses.fr/2012ENCM0008.

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L'objectif de ce travail de thèse vise à étudier la conversion de la lignine dans des conditions oxydantes hydrothermales, par catalyse hétérogène. La lignine est l'une des principales constituantes des matériaux ligno-cellulosiques. Considérée comme déchet des procédés de valorisation de la cellulose, elle est majoritairement brûlée pour produire de l'énergie. De par sa structure de polymère phénolique, la lignine peut être considérée comme la principale source de noyaux aromatiques. Une méthodologie analytique complexe a, dans un premier temps, été mise en place pour permettre une caractérisation poussée des lignines et produits d'oxydation. Les lignines étudiées ont été extraites à partir de la paille par un procédé organosolv. Le procédé d'extraction influe sur les rendements mais aussi sur les structures et propriétés des différents produits. Les catalyseurs d'oxydation sont des oxydes divisés des métaux de transition, synthétisés par voie alginate. L'oxydation de la vanilline, composé modèle de la lignine, met en évidence des phénomènes d'oligomérisation des produits formés. Lors de l'oxydation des lignines, l'utilisation d'un catalyseur augmente les rendements et modifie les équilibres de dépolymérisation – oligomérisation
The objective of this thesis is to study the conversion of lignin in oxidizing hydrothermal conditions, by heterogeneous catalysis. Lignin is among the main constituents of lignocellulose materials. Being considered like a waste of the cellulose valorization procedures, it is mostly burned to produce the energy. Taking into account its phenolic polymer structure, lignin can be considered as the main source of aromatic rings. Complex analytical methodology has initially been set up to allow a thorough characterization of lignins and oxidation products. Lignins were extracted from the straw by the organosolv procedure. The extraction process affects not only yields but also the structures and properties of products. The oxidation catalysts are transition metal oxides, synthesized by an alginate route. The oxidation of vanillin (lignin's model compound) shows the oligomerization phenomena of obtained products. In the oxidation of lignin, the use of a catalyst increases the yield and modifies the equilibrium of depolymerization - oligomerization

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Sales, Fernando Gazelli. "Oxidação umida catalitica da lignina em reatores trifasicos com produção de aldeidos aromaticos." [s.n.], 2001. http://repositorio.unicamp.br/jspui/handle/REPOSIP/267029.

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Orientadores: João Alexandre F. da Rocha Pereira, Cesar Augusto M. de Abreu
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica
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Resumo: Os materiais lignocelulósicos, representando a maior reserva natural renovável da natureza, encontram-se armazenados nas plantas sob a forma de celulose, hemicelulose, lignina e extrativos, com a lignina correspondendo cerca de 30% deste total. As rotas de beneficiamento da lignina, com destaque para os processos oxidativos, visando a produção de vanilina, principalmente, utilizam na grande maioria processos bifásicos, alguns utilizando catalisadores solúveis na fase líquida, operando no entanto, com baixos rendimentos. No presente trabalho desenvolveu-se um processo de oxidação úmida catalítica (CWAO) da lignina para a produção seletiva de aldeídos aromáticos, com ênfase na vanilina, siringaldeído e p-hidroxibenzaldeído, aplicando um catalisador de paládio suportado em y-alumina. Prevendo-se a avaliação do processo catalítico foram conduzidas experiências em reator auto clave mecanicamente agitado, operando em batelada alimentada com relação à fase gasosa. Operou-se entre 373K e 413K, a uma pressão total de 20bar, representando uma pressão parcial de oxigênio entre 2bar e 10bar. A lignina com concentração de 60gIL foi solubilizada em meio alcalino de NaOH 2N. Utilizou-se um catalisador de Pd (2,85%pp.), em y-alumina, com granulometria entre 90_m e 200_m, aplicando-se concentrações de 3%pp. a 5%pp. em relação ao volume reacional. As reações de degradação da lignina e de formação de aldeídos aromáticos foram descritas por um modelo cinético quantificado por um sistema de reações complexas do tipo série-paralelo, com etapas de pseudo-primeira ordem. A presença do catalisador resultou em níveis de rendimento e seletividade em aldeídos, muito superiores quando comparados com o processo não catalítico, representando uma redução de cerca de 50% na energia de ativação para a degradação da lignina. Os níveis de conversão da lignina em aldeídos foram de 6% a 393K, 12% a 393K e 18% a 423K, para uma pressão parcial de oxigênio de 5bar e carga de catalisador de 4%pp. Com a finalidade de produzir aldeídos aromáticos em regime contínuo, um reator de leito fluidizado trifásico contínuo foi projetado e construído, em escala mini-piloto. O sistema foi avaliado hidrodinamicamente, em testes pré-operacionais, através de análise experimental utilizada aplicou a distribuição dos tempos de residência (DTR) na fase gasosa, utilizando o gás metano como traçador. A estimação dos dois parâmetros recorreu à confrontação das previsões obtidas via função de transferência do sistema, com os resultados provenientes dos experimentos dinâmicos, adotando-se como critério a minimização de uma função objetivo através de uma subrotina de busca seqüencial. Os resultados obtidos, de 2,2% a 9,3% para a retenção gasosa, e 38,0 a 54,4 para o número de Peclet da fase gasosa, estão compatíveis com os valores publicados na literatura para reatores de dimensões semelhantes operando nas mesmas condições. A produção de aldeídos aromáticos em regime contínuo, no reator de leito fluidizado trifásico, utilizou como agente oxidante o ar atmosférico a uma pressão de 4 bar. As influências dos parâmetros operacionais foram avaliadas dentro das ITonteiras práticas de operação, isto é, vazões da fase líquida de 5,OL/h e 10LIh, temperaturas de 393K e 413K. A vazão da fase gasosa foi fixada em 1000 NL/h com uma carga de catalisador de 4%pp e granulometria de 400llm - 5001lID. A lignina foi dissolvida em uma solução alcalina de hidróxido de sódio 2N a uma concentração de 30g/L. O melhor rendimento em aldeídos aromáticos foi de 12% em relação a concentração inicial de lignina, com o reator operando a 393K e vazão da fase líquida de 5L/h
Abstract: The lignocellulosic material, representing the largest natural renewable resource, occurring in the plants under the cellulose form, hemicellulose, lignin and extractive, with the lignina corresponding about 30% of this total one. The routes of lignin chemical processing, with prominence for the oxidations processes, with the objective of vanilin production, use in the great majority two-phase processes, some using soluble catalysts in the liquid phase, operating however, with low efficiency. In the present work a process of catalytic wet air oxidation (CW AO) was developed with the objective of selective production of aromatic aldehydes, with emphasis in the vanilina, siringaldeído and p-hidroxibenzaldeído, ITom lignin, applying a palladium catalyst supported in y-alumina. Intending the evaluation of the catalytic process, experiences were carried out in a mechanically stirred high pressure autoclave reactor, in semi-batch way, in relation to the gaseous phase. It was operated in temperatures ITom 373K to 413K, at a total pressure of 20bar, representing a partia! pressure of oxygen ITom 2bar to 10bar. The lignin concentration of60gIL was in an aIkaline medium ofNaOH 2N. A palladium catalyst was used (2,85%pp.), in y-alumina, with granulometry ITom 90mm to 200mm, being applied concentrations ITom 3%pp. to 5%pp. in relation to the reactional volume. The reactions of lignin degradation and aromatic aldehydes production were described by a kinetics model quantified by a system of complex reactions of the series-parallel type, with stages of pseudo-first order. The presence of the catalyst resulted in high levels of seletivities in aldehydes, further than as compared with the non-catalytic process, representing a reduction about 50% in the activation energy for the lignin degradation. The levels of conversion ofthe lignin in aldehydes were of6% at 393K, 12% at 393K and 18% at 423K, for a partial pressure of oxygen of 5bar and catalyst loading of 4%pp. With the purpose of producing aromatic aldehydes in continuous regime way, a three-phase fluidized bed reactor was designed and built, in mini-pilot scale. The system was evaluated hydrodynamically, in pre-operational tests, through applying dynamic analysis for the gaseous phase. The hydrodynamic analysis of the system was accomplished through the values of the gaseous retention (8G) and of the ofaxial Peclet number (PeG). The experimental technique applied the residence time distribution (RTD) in the gaseous phase, using the methane gas as tracer. The estimation ofthe two parameters felI back upon the conftontation ofthe prevision obtained through transfer function ofthe system, with the results uom the dynamic experiments, being adopted as approach the minimization of a objective function through a subroutine of sequencial search. The obtained results, uom 2,2% to 9,3% for the gaseous retention, and 38,0 to 54,4 for the number of Peclet of the gaseous phase, are compatible with the values published in the literature for reactors operating in the same conditions. The aromatic aldehydes production in a continuous three-phase fluidized bed reactor, used as oxidizing agent the atmospheric air in apressure of 4 bar. The influences of the operational parameters were evaluated in the practical ranges of operation, that is, liquid phase flow rate of 5,OL/h and lOL_ temperatures of 393K and 413K. The gaseous phase flow rate was 1000 NL/h with a catalyst loading of 3%pp and granulometry of 400 j.1m 500j.1m The lignin was in an aIkaline medium of NaOH 2N, in a concentration of 30g/L. The best yield in aromatic aldehydes reached 12% in relation to lignin initial concentration, as the reactor was operating at 393K and liquid flow rate of5LIh
Doutorado
Sistemas de Processos Quimicos e Informatica
Doutor em Engenharia Química

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30

Song, Yang. "OXIDATIVE DEPOLYMERIZATION OF LIGNIN TO LOW MOLECULAR WEIGHT AROMATICS." UKnowledge, 2019. https://uknowledge.uky.edu/chemistry_etds/114.

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To date, most lignocellulosic biorefinery strategies have focused on optimizing conversion of cellulose to ethanol, leaving lignin as an underutilized biomass constituent. Lignin is engineered by nature with the intent to protect plants from chemical and biological attack; this leaves lignin with high structural irregularity and recalcitrance, rendering conversion of the lignin macromolecule to valuable products particularly challenging. Nevertheless, given that the economics of cellulosic ethanol production are strongly dependent on the value that can be obtained for the lignin co-product, the successful valorization of lignin is a crucial step in the transition towards a bio-based economy. This thesis focuses on lignin depolymerization using oxidative methods, specifically, the oxidation and cleavage of the β-O-4 linkage. Heterogeneous catalysis in this case is more desirable than homogenous catalysis as the catalyst easily recovered, and it is better suited for industrial applications. Initially, layered double hydroxide (LDH) supported gold nanoparticles were characterized and screened in the oxidation of various lignin model compounds using molecular oxygen, leading to the discovery of an Au/Li-Al LDH heterogeneous catalyst active for oxidative cleavage of the β-O-4 linkage. The Au/Li-Al LDH catalyst was then applied to oxidatively depolymerize Indulin AT kraft lignin and γ-valerolactone (GVL) extracted lignin, high yields of monomers being observed when the oxidized lignins underwent subsequent base-catalyzed hydrolysis. Thereafter, different literature oxidative lignin depolymerization methods were tested on kraft lignin and GVL lignin, and the results compared to the Au/Li-Al LDH catalyst (coupled with hydrolysis) system to determine the most effective oxidative depolymerization method.

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Santos, Marcello Moreira. "Degradação oxidativa de ligninas pelo sistema biomimetico Gif." [s.n.], 1994. http://repositorio.unicamp.br/jspui/handle/REPOSIP/249505.

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Orientador : Ulf Friedrich Schuchardt
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica
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Mestrado

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Mottweiler, Jakob [Verfasser]. "Transition metal-catalyzed oxidative cleavage of lignin and lignin β-O-4 model compounds / Jakob Mottweiler." München : Verlag Dr. Hut, 2016. http://d-nb.info/1100968946/34.

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33

Passauer, Lars. "Beiträge zur Entwicklung Wasser speichernder Materialien auf Basis von Stärke und Lignin." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1218103243285-95634.

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Vor dem Hintergrund des weltweit wachsenden Bedarfes an Bodenverbesserungsmitteln, durch die Humus-, Nährstoff- und Wassermangel auf Problemstandorten kompensiert werden sollen, war es das Ziel der vorliegenden Arbeit, Bodenwasser-speicher auf Basis der nachwachsenden Biopolymere Stärke und Lignin zu entwickeln. Durch Derivatisierung der Stärke wurde deren Hydrophilie deutlich gesteigert, was Voraussetzung für die Bildung von Hydrogelen war. Es konnte gezeigt werden, dass durch Vernetzung der wasserlöslichen Stärkederivate Carboxymethylstärke und Monostärkemonophosphat mit Di-/Tricarbonsäuren quellfähige Hydrogele erzeugt werden, deren Quellungsvermögen und rheologische Eigenschaften über die Wahl des Vernetzers und die Vernetzerstoffmenge gezielt eingestellt werden können. Die Modifizierung von Lignin wurde durch Oxidation mit Wasserstoffperoxid, z.T. in Kombination mit Fe(II)- bzw. Mn(II)-Chloriden realisiert. Dadurch wurde die Vernetzbarkeit von Lignin deutlich verbessert, was auf oxidativ bedingte Strukturänderungen des Lignins zurückzuführen war. Diese bestanden im Wesentlichen in der Spaltung und Oxidation der Lignin-Seitenkette sowie der Hydroxylierung der Seitenkette und aromatischer Strukturen. Die Vernetzung von Lignin mit Poly-(ethylenglycol)-diglycidylether ergab quellfähige Hydrogele, deren Wasseraufnahmevermögen und rheologische Materialfunktionen von der eingesetzten Vernetzerstoffmenge abhängig sind. Es konnte gezeigt werden, dass durch den Einsatz von Stärkephosphat- und Lignin-Hydrogelen das Wasserspeichervermögen erhöht und die Evaporationsraten eines entsprechend behandelten Sandbodens verringert werden. Im Wachstumsversuch wurden die Frischmasseerträge von Gelbsenf (Sinapis alba) durch Behandlung eines Sandbodens mit Hydrogelen gesteigert
Soil degradation leading to a lack of humus, nutrients and water especially on exploited sites causes the worldwide need in soil amendments. Aim of the work was the development of hydrogels from renewable biopolymers starch and lignin improving water retention especially in degraded soils. A significant increase of hydrophilic properties of starch was obtained by chemical modification with the objective of forming starch based hydrogels. Swellable hydrogels were formed by cross-linking of water soluble starch derivatives like carboxymethyl starch and monostarch monophosphates with di- and tricarboxylic acids. Swelling capacity and rheological properties of the starch gels were selective adjusted by variation of cross linking agent and whose amounts. Modification of lignin was realized by oxidation with hydrogen peroxide partly in combination with ferrous and manganese chlorides, respectively. In consequence of oxidative structural changes which were cleavage and oxidation of side chain as well as aliphatic and aromatic hydroxylation, gelation of lignin was improved significant. Lignin hydrogels with different swelling capacities and rheological functions were formed by cross-linking lignin with different amounts of poly (ethylene glycol) diglycidyl ether. Application of hydrogels based on starch and lignin causes increased water storing capacity/field capacity and decreased evaporation of a sandy soil as well as an increased biomass yield of yellow mustard (Sinapis alba)

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Rinesch, Torsten Verfasser], Carsten [Akademischer Betreuer] [Bolm, and Markus [Akademischer Betreuer] Albrecht. "Oxidative Spaltung von Lignin und Lignin-Modellverbindungen und Funktionalisierung der Spaltprodukte / Torsten Rinesch ; Carsten Bolm, Markus Albrecht." Aachen : Universitätsbibliothek der RWTH Aachen, 2019. http://d-nb.info/1194066607/34.

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Rinesch, Torsten [Verfasser], Carsten [Akademischer Betreuer] Bolm, and Markus [Akademischer Betreuer] Albrecht. "Oxidative Spaltung von Lignin und Lignin-Modellverbindungen und Funktionalisierung der Spaltprodukte / Torsten Rinesch ; Carsten Bolm, Markus Albrecht." Aachen : Universitätsbibliothek der RWTH Aachen, 2019. http://d-nb.info/1194066607/34.

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Shimizu, Felipe Lange [UNESP]. "Remoção de lignina e hemicelulose: influência na acessibilidade à celulose e sacarificação enzimática." Universidade Estadual Paulista (UNESP), 2018. http://hdl.handle.net/11449/153394.

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A biomassa lignocelulósica, como a proveniente da cana-de-açúcar, é uma fonte abundante de resíduo que pode ser usado como matéria-prima na produção de energia. Para melhor aproveitar essa biomassa, moagem e pré-tratamentos podem ser usados para alterar a estrutura do material lignocelulósico, remover lignina e hemicelulose, expondo a celulose e assim aumentando sua acessibilidade. A acessibilidade à celulose tem sido indicada como uma das propriedades mais importantes para uma boa digestibilidade enzimática. Entretanto, as biomassas geradas da cana-de-açúcar possuem características físico-químicas diferentes, respondendo de modo diferente aos pré-tratamentos. Neste contexto, este estudo teve como objetivo verificar os efeitos da remoção de lignina e hemicelulose das biomassas da cana-de-açúcar (fração externa, entrenó, nó e folha) na acessibilidade à celulose. A cana-de-açúcar foi fracionada em fração externa, nó, entrenó e folha. Cada fração passou pelos pré-tratamentos ácido (5, 10, 20 %, m/m massa de ácido por massa de material, a 121°C/30 min), alcalino (5, 10, 20 e 30 % NaOH m/m) e oxidativo (0,5, 1, 2 e 3 horas com clorito de sódio 30 %). As amostras foram caracterizadas quanto ao seu conteúdo de celulose, hemicelulose e lignina. A determinação de acessibilidade foi realizada com corantes Direct, Orange (superfície específica externa), Direct Blue (superfície específica interna) e Vermelho Congo (superfície total). A hidrólise enzimática (15 FPU/g de material, Cellic Ctec 2 - Novozymes) foi realizada para avaliar o efeito dos pré-tratamentos e acessibilidade à celulose no rendimento em glicose. O efeito dos pré-tratamentos foi primeiramente analisado pela quantidade de massa recuperada. Todas as frações estudadas apresentaram uma tendência em perder massa com aumento da concentração de reagente utilizado no pré-tratamento. O pré-tratamento ácido resultou em menor recuperação de massa, o que ocorreu em função da solubilização de hemicelulose. A caracterização química apontou a remoção de hemicelulose e principalmente lignina dos materiais em função do pré-tratamento e das suas condições. A deslignificação com clorito de sódio (oxidativo) resultou em remoção de lignina, chegando a quase a sua totalidade em materiais como a folha. A determinação de acessibilidade com os corantes Vermelho Congo, Direct Blue e Direct Orange indicaram que o aumento da concentração de reagentes no pré-tratamento provoca aumento de acessibilidade à celulose. Entretanto, os corantes Direct Orange e Blue foram mais precisos na determinação da acessibilidade à celulose em comparação ao Vermelho Congo. A fração de menor recalcitrância, entrenó, apresentou adsorção de 525,9 mg/g no ensaio com Vermelho congo, o Direct Orange 1333,3 mg/g e o Direct Blue 746,3 mg/g. O rendimento em glicose na hidrólise enzimática seguiu a tendência de melhora com aumento da acessibilidade. Do mesmo modo, a remoção de lignina resultou em maior rendimento em glicose na hidrólise enzimática, o entrenó deslignificado resultou na quase completa conversão da celulose em glicose. Este estudo identificou a fração externa como mais recalcitrante, e entrenó como menos recalcitrante, resultando em menor rendimento e maior de glicose na hidrólise enzimática, respectivamente. A remoção de hemicelulose e lignina por meio de pré-tratamentos influenciou diretamente na acessibilidade à celulose, resultando em melhor ação das enzimas na hidrólise enzimática de todas as frações.
The lignocellulosic biomass, such as the provided by the sugarcane, is an abundant source of raw materials for energy production. In order to better use this biomass, milling and pretreatments can be employed to alter the structure of the materials, remove lignin and hemicellulose. This effect exposes the cellulose and raises its accessibility, which is is one of the most important property to ensure enzymatic digestibility. However, the biomass generated from the sugarcane have different physicochemical characteristics, giving different responses to the pretreatments. In this context, this study aimed to verify the effects of lignin and hemicellulose removal from the sugarcane biomass (external fraction, node, internode and leaf) on cellulose accessibility. The sugarcane was fractioned in external fraction, node, internode and leaf. Each fraction was pretreated with acid (5, 10, 20 % m/m acid mass per material mass, at 121°C/30 min), alkaline (5, 10, 20, 30 % NaOH m/m) oxidative (0,5, 1, 2 ,3 h charged with 30 % sodium chlorite). The chemical composition of the samples was determined based on cellulose, hemicellulose and lignin contents. Accessibility was determined by dye adsorption of Direct Orange (external specific surface), Direct Blue (internal specific surface) and Congo Red (total surface). Enzymatic hydrolysis (15 FPU/g of biomass, Cellic Ctec 2 – Novozymes) was used to verify the effects of pretreatments and cellulose accessibility on the glucose yield. All studied fractions showed tendency to lose mass with increasing reagent concentrations used in the pretreatments. Acid pretreatment resulted in low mass recovery due to hemicellulose solubilization. Chemical composition showed hemicellulose removal and significant lignin removal from the materials due to the pretreatments and their conditions. Delignification by sodium chlorite (oxidative) resulted in lignin removal, with almost completely removal with leaf samples. Accessibility determined by Congo Red, Direct Orange and Direct Blue dyes indicated that more aggressive pretreatments improved cellulose accessibility. However, Direct Orange and Direct Blue dyes were more precise than Congo Red while evaluating cellulose accessibility. The less recalcitrant fraction, the internode, showed 525,9 mg/g of Congo Red adsorption, 1333,3 mg/g of Direct Orange and 746,3 mg/g of Direct Blue. Glucose yield during enzymatic hydrolysis improved with higher cellulose accessibility. Lignin removal resulted in higher glucose yield, with delignified internode samples showing almost complete cellulose conversion. This study identified the external fraction as the most recalcitrant and the internode as the least recalcitrant, resulting in lower glucose yield and higher glucose yield, respectively. Hemicellulose and lignin removal by the pretreatments directly influenced cellulose accessibility, resulting in better enzymatic activity across all fractions.

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Katahira, Rui. "Studies on cleavage of β-O-4 linkages in lignins : TIZ and modified nitrobenzene oxidation methods." Kyoto University, 2005. http://hdl.handle.net/2433/145053.

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Kyoto University (京都大学)
0048
新制・課程博士
博士(農学)
甲第11653号
農博第1509号
新制||農||911(附属図書館)
学位論文||H17||N4046(農学部図書室)
23296
UT51-2005-D402
京都大学大学院農学研究科森林科学専攻
(主査)教授中坪文明, 教授西尾嘉之, 教授松本孝芳
学位規則第4条第1項該当

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Oliveira, Fernanda de Carvalho. "Oxidação de lignina proveniente de resíduos lignocelulósicos agroindustriais para obtenção de compostos químicos aromáticos de maior valor agregado." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/97/97131/tde-05082015-153217/.

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A exploração de processos viáveis para a conversão da biomassa lignocelulósica em combustíveis limpos e produtos químicos de alto valor agregado, para complementar ou substituir produtos derivados de fontes não renováveis, é crucial para um desenvolvimento sustentável. A valorização e modificação dos componentes lignocelulósicos, torna-se imprescindível para viabilizar o sistema de biorrefinaria. A lignina, macromolécula aromática dominante na natureza, é um destes componentes que, devido a sua estrutura e composição, oferece rotas únicas para a produção de vários químicos de valor agregado. Este trabalho tem como objetivo avaliar o efeito de reações de oxidação em ligninas de bagaço e de palha de cana-de-açúcar, e de casca de café, na obtenção de compostos aromáticos de baixa massa molar, em especial a vanilina, e adicionalmente, verificar a aplicabilidade da lignina oxidada residual na obtenção de matrizes para liberação controlada de herbicida, buscando alternativas para agregar valor à lignina proveniente de resíduos agroindustriais e contribuir com a viabilização de biorrefinarias. Para isso, os materiais lignocelulósicos foram pré-tratados com ácido diluído e submetidos a deslignificação alcalina para obtenção da lignina. As frações obtidas durante cada etapa foram avaliadas quanto a composição química e Espectrometria no Infravermelho (FTIR), e as ligninas obtidas, foram ainda avaliadas por Espectrometria no Ultravioleta (UV) e por Ressonância Magnética Nuclear (1H RMN, 13C RMN e 2D RMN). As ligninas obtidas foram oxidadas em diferentes condições: oxidação enzimática utilizando lacase, em meio ácido e em meio alcalino com H2O2 e oxidação úmida em meio aquoso e alcalino utilizando H2O2. A fração líquida obtida foi analisada por Cromatografia Líquida de Alta Eficiência (CLAE) para identificar e quantificar os aldeídos aromáticos e outros compostos de degradação, enquanto a fração sólida, constituída pela lignina residual oxidada, foi avaliada por FTIR e UV. As ligninas oxidadas provenientes das condições que resultaram em um maior rendimento de vanilina, foram aplicadas na formulação de matrizes para liberação controlada de ametrina. Os resultados mostraram que a lignina de bagaço e de palha de cana não oxidadas são compostas principalmente por unidades siringil e guaiacil, respectivamente, e predominância de ligações ?-O-4, enquanto a lignina de casca de café foi composta principalmente por unidades hidroxil e predominância de ligações C-C, indicando uma estrutura mais condensada. Das oxidações avaliadas, a oxidação em meio alcalino (NaOH 10%) utilizando H2O2 9,1% gerou um maior rendimento de vanilina quando utilizada lignina de bagaço (8,13 mg/g lignina) e de casca de café (1,15 mg/g lignina), e H2O2 6,1% quando utilizada lignina de palha (6,48 mg/g lignina). A aplicação das ligninas oxidadas permitiu a obtenção de matrizes capazes de liberar o herbicida ametrina com diferentes cinéticas, dependendo das propriedades e das proporções das ligninas empregadas.
The exploration of feasible paths for the conversion of the lignocellulosic biomass into clean fuels and high value chemicals, to complement or replace products derived from non-renewable sources, is crucial for a sustainable development. The efficient utilization of the lignocellulosic components is of fundamental importance for the economic viability of biorefineries. Lignin, nature\'s dominant aromatic polymer, is a major component of the biomass that, due to its structuture and chemical composition, is a unique feedstock for producing high-value chemicals. The aim of this study is to seek for alternatives for adding value to lignin from agro-industrial waste in order to contribute to the vialbility of biorefineries. To achieve this, we evaluated the effect of oxidation reactions in sugarcane bagasse and straw lignin, and coffee husk, for obtaining aromatic compounds of low molecular weight, especially vanillin. In addition, the applicability of the residual oxidized lignin for obtaining matrices for the controlled release of herbicides was also examined in this work. For this purpose, the lignocellulosic materials were pretreated with dilute acid and subjected to alkaline delignification to achieve separation of the lignin. The fractions obtained at each stage were analyzed for chemical composition and with Infrared Spectroscopy (FTIR). The lignins were also analyzed using UV-vis Spectroscopy (UV) and Nuclear Magnetic Resonance (1H NMR, 13C NMR and HSQC). The lignins obtained were subjected to oxidation using different physiochemical conditions - enzymatic oxidation with laccase, oxidation in acidic and alkaline medium with H2O2 and wet oxidation in aqueous and alkaline medium using H2O2.The obtained liquid fraction was analyzed by High Performance Liquid Chromatography (HPLC) to identify and quantify the aromatic aldehydes and other compounds of lignin degradation, while the solid fraction, comprising the oxidized residual lignin, was analyzed by FTIR and UV. The oxidized lignins derived from the conditions that have resulted in a maximun yield of vanillin, were applied in the formulation of controlled release matrices of ametryne. Results for non oxidized lignin showed bagasse and straw lignin being composed mainly of syringyl and guaiacil units, respectively, linked predominantly by ?-O-4 bonds, while coffee husk lignin was mainly composed of hydroxyl units linked by C-C bonds predominantly, indicating a more condensed structure. Of all the oxidation reactions, the oxidation in alkaline medium (NaOH 10%) using H2O2 9.1% showed the highest yield of vanillin with bagasse lignin (8.13 mg/g lignin) and coffee husk lignin (1.15 mg/g lignin), and H2O2 6.1% with straw lignin (6.48 mg/g lignin). The application of oxidized lignins as matrices resulted in the release of the herbicide ametryne with different kinetics, depending on the proportions and properties of the lignins applied.

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Fang, Zhen. "OXIDATIVE DEGRADATION OF LIGNIN AND INVESTIGATION OF UTILIZATION OF LIGNIN-DERIVED MATERIALS AS BUILDING BLOCKS FOR EPOXY RESINS." UKnowledge, 2019. https://uknowledge.uky.edu/chemistry_etds/110.

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Lignin, the second most abundant biopolymer on earth, is potentially a replaceable source for bulky fuels and chemical feedstocks. There have been numerous reports on methods for the oxidative cleavage of β-O-4 linkages but relatively few reports of how those methods affect other linkages that are present in lignin. We investigated how the β-1 and β-5 linkages respond under oxidative conditions proposed for lignin deconstruction based on their effect on β-O-4 linkages. Mechanochemical treatment of lignin can greatly improve the yield of monomer products and we applied a mechanochemical approach, using powerful ring-and-puck milling to promote lignin degradation. Along with similar production of monomers in a much shorter period than what we observed in previous ball-milling process, much more unexpected reactions were taking place during the current mechanochemical process. Lignin is a promising feedstock for epoxy resins since lignin-derived aromatic monomers usually bear hydroxyl and carboxyl groups. We are working on utilizing these mono-aromatic compounds and highly-functionalized-lignin as precursors for preparation of epoxy thermosets. We are interested in investigating the properties of thermosets by utilizing the actual isolated monomer streams from raw lignin. We expect to observe attractive thermal and mechanical properties from these lignin-derived epoxy thermosets compare to that of the commercialized but currently limited-used BPA-based epoxy resins.

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Setälä, Harri. "Regio- and stereoselectivity of oxidative coupling reaction of phenols : spirodienones as construction units in ligin /." [Espoo, Finland] : VTT, 2008. http://www.vtt.fi/inf/pdf/publications/2008/P689.pdf.

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Widiatmoko. "Oxygen delignification process chemistry for Acacia." Thesis, Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-10212006-130331/.

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Bateni, Fazel. "Development of Non-precious Metal and Metal Oxide Electrocatalysts for an Alkaline Lignin Electrolysis Process." Ohio University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1562674707447307.

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Mottweiler, Jakob Verfasser], Carsten [Akademischer Betreuer] [Bolm, and Walter [Akademischer Betreuer] Leitner. "Transition metal-catalyzed oxidative cleavage of lignin and lignin β-O-4 model compounds / Jakob Mottweiler ; Carsten Bolm, Walter Leitner." Aachen : Universitätsbibliothek der RWTH Aachen, 2016. http://d-nb.info/1129875717/34.

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Mottweiler, Jakob [Verfasser], Carsten [Akademischer Betreuer] Bolm, and Walter [Akademischer Betreuer] Leitner. "Transition metal-catalyzed oxidative cleavage of lignin and lignin β-O-4 model compounds / Jakob Mottweiler ; Carsten Bolm, Walter Leitner." Aachen : Universitätsbibliothek der RWTH Aachen, 2016. http://d-nb.info/1129875717/34.

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Yoshida, Ryouta. "Development of Metalated Amino Acids and Peptides as Oxidation Catalysts and Application of Those to Selective Lignin Degradation." 京都大学 (Kyoto University), 2017. http://hdl.handle.net/2433/225620.

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Sjöberg, Gudrun. "Lignin degradation : long-term effects of nitrogen addition on decomposition of forest soil organic matter /." Uppsala : Dept. of Soil Sciences, Swedish Univ. of Agricultural Sciences, 2003. http://epsilon.slu.se/a419.pdf.

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47

Nota, Monica. "Electrochemical oxidation of Kraft lignin for the production of value-added chemicals on Ni and Co electrocatalysts." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/21706/.

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La vanillina è un’aldeide aromatica importante da un punto di vista industriale, in quanto viene ampiamente utilizzata dall’industria alimentare, cosmetica e farmaceutica. Attualmente, la vanillina da biomasse viene ottenuta attraverso l’ossidazione catalitica della lignina. Un’alternativa è rappresentata dall’ossidazione elettro-catalitica, un processo che sta riscuotendo un notevole interesse, perché permette di lavorare in condizioni blande. L’obiettivo di questo lavoro è stato quello di sintetizzare elettro-catalizzatori che favoriscano la depolimerizzazione della lignina Kraft per ottenere selettivamente vanillina. Sono state utilizzate schiume di Ni a cella aperta, tal quali e elettro-depositate con idrossidi di Ni-Co e Co. La formazione degli osso-idrossidi dei metalli, sulla superficie delle schiume, e la OER contribuiscono all’elettro-ossidazione della lignina, mentre la resa di vanillina dipende sia dal catalizzatore che dalle condizioni di reazione (potenziale applicato e tempo di reazione). La resa maggiore di vanillina è stata ottenuta applicando 0.6 V vs SCE con un tempo di reazione di un’ora e utilizzando la schiuma di Ni bare come catalizzatore. Indipendentemente dal tipo di catalizzatore usato, aumentando il tempo di reazione la resa di vanillina diminuisce, probabilmente a causa delle reazioni di ri-condensazione e ossidazione successiva dei prodotti che coinvolgono la vanillina stessa. La presenza di idrossidi di Ni-Co e Co sulla schiuma di Ni non ne migliora l’attività catalitica. La schiuma Co/Ni esibisce un’elevata carica accumulata e un’alta conversione, probabilmente dovuto alle reazioni parassite che sfavoriscono l’accumulo di vanillina. Le schiume Ni-Co/Ni invece, presentando sia una resa in vanillina intermedia tra le altre due ma associata ad una carica accumulata molto bassa. Un risultato incoraggiante per possibili sviluppi futuri.

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Cronin, Dylan J. "Studies on the hydrothermal liquefaction of lignin to dicarboxylic acids and aromatics." Thesis, Queensland University of Technology, 2018. https://eprints.qut.edu.au/118668/1/Dylan_Cronin_Thesis.pdf.

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In the last decades, there has been increasing demand by society for non-toxic renewable products that could be used to replace fossil-based building blocks. Lignin is a major component of nonedible biomass, and is the most abundant renewable source of aromatics in nature. The research work investigated the breakdown of lignin using a novel thermochemical approach. It resulted in the production of organic acids, which can be formulated to produce green pesticides and herbicides. The study also resulted in the production of low molecular weight aromatics, which can be used for the production of bio-based polymers, including biodegradable packaging materials.

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Antonsson, Stefan. "The Use of Lignin Derivatives to Improve Selected Paper Properties." Licentiate thesis, KTH, Fibre and Polymer Technology, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4503.

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Ved består huvudsakligen av tre typer av polymerer, cellulosa, hemicellulosa och lignin. Lignin bildas i naturen genom enzymatiskt initierad oxidativ koppling av tre olika typer av fenylpropan-enheter. Dessa bygger genom olika kol-kol- och kol-syre-bindningar upp en amorf tredimensionell polymer. När kemisk massa tillverkas bryts lignin ner och löses ut i kokluten. Luten innehåller de förbrukade kokkemikalierna och bränns generellt i en sodapanna för att regenerera kemikalierna och producera ånga. Sodapannan är emellertid dyr. Därför har den blivit produktionsbegränsande på många massabruk. Att avlägsna en del av ligninet från avluten vore därför önskvärt och att finna ekonomiskt intressanta produkter baserade på lignin från svartlut är därför ett viktigt forskningsområde .

Ett lämpligt område för ligninprodukter vore som tillsatts i oblekt massa. Oblekt massa används till stor del för tillverkning av kraftliner, topp- och bottenskikten på wellpapp. När lådor av wellpapp lagras i containrar som färdas över haven, förändras den relativa luftfuktigheten. Detta gör att lådorna kollapsar lättare än om de skulle ha lagrats vid konstant luftfuktighet, även en hög sådan. Detta är på grund av det så kallade mekanosorptiva- eller accelererade krypfenomenet. Genom tillsatts av våtstyrkemedel till kraftliner eller behandla den med hydrofoba ämnen, finns indikatoner på att mekanosorptiva effekten skulle kunna minska.

För att försöka minska den effekten har ett lågmolekylärt kraftlignin, som utvunnits med hjälp av tvärsflödesfiltrering av svartlut och svavelsyrafällning, använts. Genom derivatisering av detta lignin med linolja erhölls ett hydrofobt ligninderivat som uppvisar strukturella likheter med biopolymeren suberin. När detta suberinlika ligninderivat tillsätts till massa verkar det mekanosorptiva krypet minska. När lågmolekylärt lignin används tillsammans med ligninradikalinitiatorerna lackas eller mangan(III) i kraftlinermassa erhålls dessutom en våtstyrka på ca 5% av torrstyrkan. Efter aminering av detta lignin gav en tillsatts till kraftlinermassan en våtstyrka på upp till 10% av torrstyrkan. Det finns indikationer på att det mekanosorptiva krypet samtidigt minskar när dessa behandlingar görs som ger upphov till ökad våtstyrka.

Wood consists mainly of three types of polymers; cellulose, hemi cellulose and lignin. Lignin is formed in nature through enzymatic initiated oxidative coupling of three different kinds of phenyl propane units. These form by various carbon-carbon and carbon-oxygen bonds, an amorphous three-dimensional polymer. As chemical pulp is produced, lignin is degraded and dissolved into pulping liquors. These liquors contain the spent cooking chemicals and are generally burnt in a recovery boiler to regenerate cooking chemicals and produce steam. However, the recovery boiler is expensive. Hence, it has become the bottleneck for production in many pulp mills. Removal of some lignin from the spent cooking liquor would, for that reason, be desired and valuable products based on lignin from cooking liquors are searched for.

One suitable area for lignin products would be as additive in unbleached pulp. A major product from unbleached pulp is kraftliner, the top and bottom layers of corrugated board. When boxes of corrugated board are stored in containers travelling overseas the relative humidity is varying. This makes the boxes collapse more easily than if they were stored at constant humidity, even a high one. This is due to the so called mechano-sorptive or accelerated creep phenomenon. By addition of wet strength additive to kraftliner or treating it with hydrophobic compounds there are indications on that the mechano-sorptive effect would decrease.

Trying to decrease this effect, low molecular weight kraft lignin has been used. It was obtained by cross-flow filtration of black liquor and precipitation by sulphuric acid. By derivatisation of this lignin by linseed oil, a hydrophobic lignin derivative was obtained, similar in structure to units in the biopolymer suberin. As this suberin-like lignin-derivative was added to pulp the mechano-sorptive creep seemed to be lowered. Furthermore, when the low molecular weight lignin was used together with the lignin radical initiators laccase or manganese(III) in kraftliner pulp, a wet strength of about 5% of dry strength was obtained. An amination treatment of this lignin and addition to kraftliner pulp resulted in a wet strength of up to 10% of dry strength. There are indications of that the mechano-sorptive creep also decreases as these treatments, resulting in increased wet strength, are made.

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Cornu, Agnès. "Synthèse et biosynthèse de composés modèles de complexes lignine-polysaccharides." Grenoble 1, 1989. http://www.theses.fr/1989GRE10051.

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L'etude des complexes du titre a ete envisagee selon deux approches: a) la premiere correspond a la synthese de composes mixtes modeles, avec differentes aglycones mono ou dimeriques, correspondant a des liaisons glycosidiques et a des liaisons ether benzylique. La sensibilite de ces liaisons vis-a-vis de l'oxydation a ete testee. B) la seconde est une etude biochimique. On prepare des polymeres a base d'alcool coniferylique a l'aide d'un extrait brut enzymatique en presence d'hydrates de carbone (polysaccharides ou nucleotides-oses) pour obtenir in vitro les complexes recherches

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Dissertations / Theses on the topic 'Lignite Oxidation'

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