Use of levulinic acid to produce chemicals

The non-edible Biomass is an abundant and relatively cheap carbon source that can be quickly reintegrated and that is ethically accepted because they cannot be used as a food source. They represent the best candidate to supply both energy and non-fossil carbon for our industrial society and have an enormous potential since they can be transformed into useful platform chemicals through biotechnological or thermochemical conversion steps. Levulinic acid (LA) was highlighted as one of the most promising platform chemicals mainly obtained from acid hydrolysis of lignocellulosic biomass because its synthesis is easier respect to other possible building block derived from cellulose. However, the actual chemical processes limit an economically convenient production in commercial quantities. Levulinic acid esters (LAEs) or alkyl levulinates fall certainly within the most important derivatives of levulinic acid and represent strategic value-added chemicals from a biofuel-market perspective, as biofuel additives, replacing current chemicals synthetized from petrochemicals. At the present, ethyl levulinate (EL) is the most widely studied alkyl levulinate since it provides a better blending option with fuel likewise other higher alcohols (butyl levulinate). The big advantage of EL is that it is synthetized with ethanol, which is traditionally produced from renewable resources. In this thesis work, the use of heterogenous catalysts for esterification reaction, with a deep investigation on kinetic aspects to design and optimize industrial reactors, will be investigated. The influence of reaction parameters on the esterification reaction of Levulinic acid with different catalysts (Amberlyst-15, Amberlite IR120 and Dowex 50Wx8) is studied. Furthermore, a process intensification study from batch to continuous reactor for the ethyl levulinate synthesis with Amberlite IR120 as catalyst is reported. At least, the possibility to use a chromatographic reactor, to integrate reaction and separation stages regarding the esterification reaction is described. The second objective of this thesis project is to study the hydrogenation of levulinic acid, by which is possible to obtain γ-valerolactone, that is a very interesting solvent that can substitute the traditional solvents. About the hydrogenation reaction the experimental work done was devoted to elucidating the influence of catalyst acidity in γ-valerolactone yield, and a deeper analysis on the performances of SiO2/Nb2O5/RuO catalysts, prepared via sol-gel technique was conducted

Advances in the Catalytic Conversion of Biomass Components to Ester Derivatives: Challenges and Opportunities

Biomass has received significant attention as a sustainable feedstock that can replace diminishing fossil fuels in the production of value-added chemicals and energy. Many new catalytic technologies have been developed for the conversion of biomass feedstocks into valuable biofuels and bioproducts. However, many of these still suffer from several disadvantages, such as weak catalytic performance, harsh reaction conditions, a high processing cost, and questionable sustainability, which limit their further applicability/development in the immediate future. In this context, the esterification of carboxylic acids represents a very valuable solution to these problems, requiring mild reaction conditions and being advantageously integrable with many existing processes of biomass conversion. An emblematic example is the acid-catalyzed hydrothermal route for levulinic acid production, already upgraded to that of higher value alkyl levulinates, obtained by esterification or directly by biomass alcoholysis. Many other chemical processes benefit from esterification, such as the synthesis of biodiesel, which includes monoalkyl esters of long-chain fatty acids prepared from renewable vegetable oils and animal fats, or that of cellulose esters, mainly acetates, for textile uses. Even pyrolysis bio-oil should be stabilized by esterification to neutralize the acidity of carboxylic acids and moderate the reactivity of other typical biomass-derived compounds, such as sugars, furans, aldehydes, and phenolics. This Special Issue reports on the recent main advances in the homogeneous/heterogeneous catalytic conversion of model/real biomass components into ester derivatives that are extremely attractive for both the academic and industrial fields. Dr. Domenico Licursi Guest Edito

Heterogeneously catalyzed hydrothermal processing of C5-C6 sugars

Biomass has been long exploited as an anthropogenic energy source; however, the 21st century challenges of energy security and climate change are driving resurgence in its utilization both as a renewable alternative to fossil fuels and as a sustainable carbon feedstock for chemicals production. Deconstruction of cellulose and hemicellulose carbohydrate polymers into their constituent C5 and C6 sugars, and subsequent heterogeneously catalyzed transformations, offer the promise of unlocking diverse oxygenates such as furfural, 5-hydroxymethylfurfural, xylitol, sorbitol, mannitol, and gluconic acid as biorefinery platform chemicals. Here, we review recent advances in the design and development of catalysts and processes for C5-C6 sugar reforming into chemical intermediates and products, and highlight the challenges of aqueous phase operation and catalyst evaluation, in addition to process considerations such as solvent and reactor selection

Hybrid designed porous carbon dispersed gold/metal oxide nanocomposites for catalytic synthesis of biomass-derived chemicals

Abstract: Please refer to full text to view abstract.Ph.D. (Chemistry

Design of novel well-defined organorhenium heterogeneous catalyst for unsaturated fatty acid derivatives self-metathesis

La formation des liaisons C-C est parmi les cibles les plus élevés de la science et de la technologie de la catalyse. Dans ce cadre, la réaction de métathèse catalytique a gagné une importance considérable en raison de l'efficacité du processus de transformation. Par conséquent, un grand progrès a été réalisé dans ce domaine avec le développement de plusieurs catalyseurs homogènes et hétérogènes, ainsi que les différentes approches de métathèse. Cette formule a permis une conception plus facile et plus durable de diverses stratégies de synthèse dans différents domaines, y compris la synthèse organique, la science des polymères, etc. Cependant, le développement des catalyseurs de métathèse robustes pour les applications à grande échelle est encore une tâche difficile. Tenant compte de cela, les résultats de recherche présentés dans cette thèse de doctorat se concentrent sur la synthèse d'un nouveau catalyseur hétérogène de métathèse. Par conséquent, le méthyltrioxorhénium (MTO) a été supporté sur différents matériaux à base d'alumine. La performance des catalyseurs synthétisés a été étudié par l'auto-métathèse de l'oléate de méthyle, choisi comme substrat modèle; volumineux et fonctionnalisé, afin d'évaluer la tolérance des espèces actives aux groupements fonctionnels, ainsi que d'évaluer sa diffusion à l'intérieur des canaux mésoporeux. Tout d'abord, des supports très organisés à base alumine mésoporeux organisée modifiée avec le chlorure de zinc (ZnCl2-AMO) ont été préparés avec succès grâce à un procédé sol-gel puis une imprégnation post-synthèse. Le MTO supporté sur ces supports catalytiques est très actif pour l'auto-métathèse de l'oléate de méthyle, avec des vitesses de réaction plus élevées et une meilleure sélectivité par rapport aux catalyseurs à base d'alumine classiques. Cette amélioration est attribuée à des meilleurs phénomènes de transfert de masse à l'intérieur du réseau mésoporeux organisé. Ensuite, nous avons développé une voie de synthèse efficace en une seule étape pour la préparation des matériaux ZnCl2-AMO. Cette approche a permis l'accès à des supports ZnCl2-AMO très ordonnés avec de meilleurs rendements de synthèse ainsi que de meilleures propriétés physiques et de surface. En outre, ces fonctionnalités améliorées ont permis aux catalyseurs à base de MTO supportés sur ces matériaux préparés en une seule étape de manifester une meilleure performance catalytique par rapport à celle de ZnCl2-AMO préparé par le processus en plusieurs étapes. Toutefois, des études spectroscopiques ont révélé la formation d'espèces actives semblables sur la surface pour tous les supports catalytiques préparées. Ces caractérisations nous ont guidés pour étudier et proposer un mécanisme complet pour les voies de formation des produits de métathèse, ainsi que le cycle catalytique de métathèse, démontrant l'effet d'encombrement stérique sur l'interface de catalyseurs qui contrôle la sélectivité de la réaction. La synthèse des catalyseurs de métathèse MTO/ZnCl2-AMO nous a permis d'effectuer efficacement les transformations de métathèse utilisant des matières premières renouvelables (par exemple des acides gras estérifiés provenant des huiles végétales), offrant un accès à une variété de monomères fonctionnalisés, qui pourraient éventuellement être utilisés pour d'autres transformations telles que la synthèse des bio-polymères à valeur ajoutée à base (par exemple, les bioplastiques, biosurfactants).Sustainable C-C bond forming reactions have been among the highest target of catalysis science and technology. In this scope, metathesis reaction has been gaining enormous attention due to the efficiency of the transformation process. Therefore, a great progress has been made in this area by developing several homogeneous and heterogeneous catalysts as well as distinct metathesis reaction approaches. This allows an easier and more sustainable design for various synthesis strategies in different fields including organic synthesis, polymer science, etc. However, the development of robust metathesis catalysts for large scale applications is still a challenging task. Taking this into account, this research presented in this doctoral dissertation is focusing on the synthesis of new heterogeneous metathesis catalysts. Therefore, methyltrioxorhenium (MTO) was supported on various alumina-based materials. The synthesized catalysts' performance was studied though methyl oleate self-metathesis, chosen as a model bulky functionalized substrate, in order to evaluate the active species tolerance to functional groups as well as to evaluate its diffusion inside the mesoporous channels. First, highly organized ZnCl2-modified OMA supports were successfully prepared through a sol-gel method followed by a post-synthesis modification via wet-impregnation process. MTO supported on these catalytic supports were found o be highly active for methyl oleate self-metathesis, displaying higher reaction rate and products selectivity compared to the conventional wormhole-like alumina-based catalysts. This improvement is ascribed to enhanced mass transfer phenomena inside the organized mesoporous network. Afterwards, we have developed efficient one-pot synthesis route ZnCl2-modified OMA supports. Interestingly, this approaches allowed access to numerous highly ordered ZnCl2-modified OMA supports with better synthesis yields and improved textural and surface properties. Moreover, these enhanced features allowed the MTO-based catalyst supported on these one-step prepared materials to exhibit higher metathesis reaction performance compared to ZnCl2-modified OMA supports prepared via the two-steps processes. However, spectroscopic investigations revealed the formation of similar surface active species for all the prepared catalytic supports. These characterizations guided us to study and propose a comprehensive mechanism of metathesis products formation pathways as well as the metathesis catalytic cycle, demonstrating the steric hindrance effect on the catalysts interface that governed the reaction selectivity. The synthesis of the 3 wt.% MTO/ZnCl2-OMA catalysts allowed us to efficiently perform metathesis reaction using renewable feedstock (e.g. fatty acid esters derived from vegetable oils), offering access to a variety of functionalized monomers which could be used for further transformations such as the synthesis of value-added bio-based polymers (e.g. bioplastics, biosurfactants)

Photodegradation of phenol in rotating disk reactor and 3D CFD modelling

Phenol is a chemical that is associated with the regulations in place that control the release of contaminants to the water environment. The photocatalytic degradation as advanced oxidation process is seen among the promising routes for reduction of a wide range of organic pollutants. This work investigates the degradation of phenol in a rotating disc reactor (RDR) as process intensification approach and highlights the role of the process parameters and relevant impacts on both mass transfer effectiveness and reaction rate performance over the essential role of oxygen penetration in the liquid film, the surface reaction catalyzed by the intermediate hydroxyl radicals and the UV light activation. Ensuring a sufficient supply to the catalyst surface is achieved by the thin film subject to the dynamic operations of the rotating disk and the deep light penetration across the bulk liquid film. This work aims to assess via a laboratory work the impact of hydrodynamics generated by the rotational speed and flow dyn

Heterogeneous Catalytic Conversion of Biomass-Derived Platform Molecules to Fuels and Specialty Chemicals

The increasing global consumption of petroleum-derived fuels and chemicals has resulted in rapid generation of atmospheric CO2, the accumulation of which has adverse effects on the global climate. One strategy for lowering the overall emission of CO2 from the combustion of petroleum-derived fuels and lubricants is to replace them with similar products derived from renewable sources. This approach has the potential to be both environmentally responsible and economical, particularly if policy changes incentivize the use of non-fossil energy resources in the future. Biomass, such as agricultural waste, is a readily available source of renewable carbon for producing fuels and chemicals that does not compete with the demand for food. Efforts in biological fermentation of biomass-derived sugars via ABE fermentation have enabled the attainment of renewable butanol, acetone, and ethanol with the molar ratio of 6:3:1. These so-called platform molecules can be upgraded to produce higher carbon number fuels and chemicals using heterogeneous catalysts. This thesis is focused on developing an understanding of several heterogeneous catalytic pathways towards producing fuels and specialty chemicals from renewable platform molecules; specifically, acetone, ethanol, and other biomass-derived alcohols. The first three chapters of this thesis are centered around understanding the etherification of biomass-derived alcohols and other platform molecules to produce ethers for use as fuels and lubricants. Ethers have attracted recent interest as diesel additives and specialty chemicals due to their high cetane numbers and excellent lubricant properties, and they can be produced via direct etherification of biomass-derived alcohols in the liquid phase. The competing reaction for alcohol dehydration over an acid catalyst is unimolecular dehydration to form alkenes, which is thermodynamically favored above approximately 350 K. To improve the activity and selectivity towards direct etherification of long chain alcohols in the liquid phase, it is necessary to develop an understanding of the mechanism and kinetics of etherification and dehydration reactions. In the first study of this dissertation, tungstated zirconia was identified as a selective solid acid catalyst for the liquid phase etherification of 1-dodecanol. Through kinetic modeling and mechanistic probing, this study suggested that a cooperative effect between Brønsted and Lewis acid sites on tungstated zirconia enhances the selectivity to ether by increasing the surface concentration of adsorbed alcohol molecules, promoting bi-molecular etherification over unimolecular dehydration. Kinetic isotope effects for linear alcohol dehydration were measured to elucidate the rate limiting steps in the mechanism. Effects of alcohol concentration and product inhibition were measured and fit to kinetic models consistent with the proposed mechanisms. In addition, acid site characterization and selective poisoning experiments were used to probe the role of the acid sites and support the proposed mechanism.In the second study, the scope of alcohols for the synthesis of ethers via direct etherification over tungstated zirconia was expanded to include a variety of biomass-derived alcohols ranging from C6-C24 with varying degrees of carbon chain branches and substitution. The effects of alcohol length, position of carbon chain branches, and length of carbon chain branches were studied for etherification and dehydration reactions. Trends in the effects of alcohol structure on selectivity were consistent with the proposed mechanisms for etherification and dehydration and elucidated possible pathways to selectively form ethers from biomass-derived alcohols. In the third chapter of this thesis, these studies of direct etherification were explored within in the greater context of the etherification literature. Tradeoffs between catalyst selectivity, activity, stability, and reaction conditions required to achieve the most economically and environmentally favorable routes to biomass-derived ethers were discussed with the goal of identifying the combination of catalyst properties required to achieve high ether selectivity for a specified class of synthons.Continuing the investigation of the valorization of alcohols via heterogeneous catalysis, the next study focused on the valorization of ethanol through oxidation reactions over Ag, Au, and Cu nanoparticles on Li2O/Al2O3. The interest in studying the oxidation of ethanol over arose from striking reports in the literature that identified Ag and Ag, Au, and Cu nanoparticles on Li2O/Al2O3 as highly selective catalysts for the single-step conversion of ethanol to ethylene oxide, a valuable precursor for the synthesis of many polymers and specialty chemicals. Motivated by these reports, a systematic study of the effects of catalyst support, Li2O loading, and various nanoparticle synthesis procedures was performed to provide an understanding of the unexpected selectivity reported in the literature. Systematic kinetic measurements and product characterization revealed that the primary product of this reaction is acetaldehyde, not ethylene oxide, and that errors in previous reports in the literature could be attributed to mis-identification of products with gas chromatography and mass spectrometry.The last study in this thesis is centered around the valorization of bio-ethanol and acetone via conversion to isobutene. Isobutene is a valuable specialty chemical used in the production of fuel additives, polymers, and other high-value products. Isobutene is normally produced via steam cracking of petroleum naptha, thus the use of renewable platform molecules such as ethanol and acetone to synthesize isobutene has received increasing interest. Recent work in the literature has shown that zinc-zirconia mixed oxides selectively catalyze the production of isobutene from ethanol and acetone in the presence of water at 723 K. While this reaction is stable and selective, little is known about the mechanism, kinetics, and reaction pathway. In this study, a thorough investigation into the mechanism and kinetics of the acetone and ethanol conversion to isobutene was performed with the aim of elucidating the reaction pathway, the roles of active acidic and basic sites, and the role of water in promoting stability and selectivity. A reaction sequence for the conversion of ethanol to isobutene was proposed and supporting using a combination of catalyst synthesis, characterization, and kinetic measurements. The 5-step sequence starts with the dehydrogenation of ethanol to acetaldehyde, followed by oxidation to acetic acid, ketonization to acetone, and then dimerization to diacetone alcohol which then either undergoes decomposition or dehydration to mesityl oxide and subsequent hydrolysis to produce isobutene and acetic acid, which undergoes further ketonization to acetone. The dispersion of zinc oxide on zirconia was found to produce a balance between Lewis acidic and basic sites that promotes the cascade reactions of ethanol and acetone to isobutene.Overall, this thesis brings together fundamental studies of the mechanisms and kinetics of these heterogeneous catalytic reactions to create a broader picture of the catalyst properties and reaction conditions necessary to enable the selective conversion of biomass-derived platform molecules to fuels and specialty chemicals. Bifunctional catalysts with cooperative Brønsted and Lewis acid sites, as well as Lewis acid and base sites, have emerged as versatile systems to study C-O and C-C bond forming reactions. This thesis also demonstrates the versatility of the zirconia support and various promoters in producing catalytic materials with tunable acid and base properties, and thus tunable catalytic activity and selectivity. By providing extensive catalyst characterization as well as kinetic and mechanistic probing, this thesis elucidates the catalytic properties and reaction conditions that favor the effective production of fuels and specialty chemicals from renewable platform molecules, specifically concentrating on the synthesis of ethers and isobutene. While this thesis focuses on the fundamental understanding of these reactions, the insights gained are part of a larger effort by the scientific community to develop creative solutions to the growing global energy demands in the dawn of an era when continuing to burn fossil fuels is triggering devastating effects on the health of the planet and its inhabitants

Sustainable Synthesis of Gamma-Valerolactone

The aim of this work was the sustainable synthesis of gamma-valerolactone over non-noble metal catalysts in batch autoclave (screening) and a continuous flow set-up. In order to further develop an environmentally benign process, formic acid which is generated as a by-product, was considered directly as hydrogen source

Síntesis de nanopartículas asistida por microondas en condiciones batch

The development of intensified processes for the preparation of novel catalytically active nanodimensional materials is a captivating challenge getting more attention day-by-day.1, 2 In fact, nanoparticle systems offer the possibility of combining the high activity of homogenous catalysts with the better recoverability of heterogeneous ones, opening to unlimited application in the chemical industry. The microwave-assisted technique – recognized as one of the most innovative methods for process intensification – makes it possible to both synthesize and test new nanocatalysts exploiting the unique characteristics of microwave heating. These characteristics include reduced reaction times, minimized (or suppressed) side reactions, highly reproducibility, enhanced yields and selectivity as well as selective heating and magnetic loss heating.3-5 The PhD thesis presented has been developed thanks to the experience of the research group FQM-383 (NanoVal) in nanoscale chemistry, heterogeneous catalysis and waste/biomass valorization. More in details, the research studies of the PhD thesis demonstrated the potentiality of microwave-assisted techniques for the development of efficient nanocatalytic systems specifically designed for photochemical applications, fine chemical synthesis and biofuel production.6-10 Most important results obtained during the PhD Thesis have been described in three research articles. In addition, a comprehensive minireview has been included in the introduction section in order to highlight the primary importance of nanocatalysts for the production of biofuels. The first research article, “Microwave-assisted valorization of pig bristles: towards visible light photocatalytic chalcocite composites”, discloses the preparation of nano-Cu2S carbon composites via a fast and low-toxicity microwave-assisted method.11 The synthesis was carried out employing ethylene glycol as solvent, copper chloride as metal precursor and waste pig bristles as sulfur and carbon source, avoiding the use of any toxic sulfur precursor (e.g. H2S, thiourea). The high microwave adsorption and high viscosity of ethylene glycol allowed for the preparation of homogeneous Cu2S carbon composites within a few minutes (4 minutes at 200°C operating in a multimode microwave oven). By contrast, conventional heating needed longer reaction times and formed inhomogeneous, low-active Cu2S carbon material. The so-produced composite has been characterized by X-ray diffraction (XRD), nitrogen physisorption (BET model), scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM-EDX) and UV-Vis spectroscopy. Cu2S carbon composite has been successfully used for the photo degradation of methyl red, a common pollutant dye, under visible LED light irradiation, leading to ca. 40% of degradation within 3 hours. In the second research article, “Heterogeneously Catalyzed Synthesis of Imidazolones via Cycloisomerizations of Propargylic Ureas Using Ag and Au/Al SBA-15 Systems”, a study of environmentally friendly paths for the cycloisomerization of propargylic ureas has been explored.12 Specifically, different nanogold and nanosilver catalsyts have been prepared by supporting the metal nanoparticles over mesoporous silica (AlSBA-15) through mechanochemistry and microwave-assisted approaches. The catalysts have been used as heterogeneous systems in the microwave assisted synthesis of a library of imidazolones via a sequential study aimed to shift the reaction to greener operative conditions. The employed systems avoided the utilization of strong bases, such as NaOH, or expensive homogeneous metal catalysts. The best conditions have been combined in order to catalyse the cycloisomerization of propargyl ureas using only water as solvent and promoter of the reaction. The results demonstrated that the selected solvent highly influenced the reactions, where toluene promoted N-cyclization reactions, ethanol favoured the cyclization of propargylic ureas characterized by more electron withdrawing groups and water favoured the cyclization of propargylic ureas containing electron donor compounds in the structure. The third research article, “Efficient and Environmentally Friendly Microwave-Assisted Synthesis of Catalytically Active Magnetic Metallic Ni Nanoparticles” describes the preparation of pure magnetic metallic nickel by a simple and fast microwave-assisted method using a monomode microwave reactor (CEM Discover, CEM Corp.).13 The synthesis has been carried out using nickel chloride as metal precursor and a mixture of ethylene glycol and ethanol (or isopropanol) as solvent and reducing agent. A fine study carried out varying the molar ratio of ethylene glycol and ethanol in function of the reaction temperature has highlighted the reaction conditions where the reduction of nickel occurred. The best performance (71% yield) has been achieved operating at 250°C for 5 minutes under microwave irradiation. The mechanism of reaction for oxidation of ethylene glycol and reduction of Ni2+ has been demonstrated by gas chromatography–mass spectrometry (GC-MS) analysis, while the behaviour of the mixture and its bubble point in function of the recorder pressure has been simulated by PRO/II software (Schneider Electric Group). The nanoparticles have been analysed by X-ray diffraction (XRD), scanning emission microscopy (SEM), transmission electron microscopy (TEM) and magnetic mass susceptibility. The surface area has been determined by nitrogen physisorption (BET model). The nanoparticles have showed good activity in the hydrogenolysis of benzyl phenyl ether (BPE), a lignin model compound, with a maximum conversion of 24%, and reusability up to 5 cycles without sensible loss of activity.El desarrollo de procesos destinado a la preparación de nuevos materiales con dimensiones nanométricas y, a su vez, catalíticamente activos, es un desafío fascinante que llama cada vez más la atención1, 2. De hecho, los sistemas compuestos de nanopartículas ofrecen la posibilidad de combinar la alta actividad de los catalizadores homogéneos con la mejor capacidad de recuperación de los heterogéneos, ofreciendo de esta manera un número ilimitado de aplicaciones en la industria química. La técnica asistida por microondas, reconocida como uno de los métodos más innovadores para la intensificación de procesos, permite sintetizar y probar nuevos nanocatalizadores que exploten las características únicas del calentamiento por microondas. Estas características incluyen tiempos de reacción reducidos, reacciones secundarias minimizadas (o suprimidas), alta reproducibilidad, rendimientos y selectividad mejorados, así como calentamiento selectivo y calentamiento por pérdida magnética.3-5 La presente tesis doctoral se ha desarrollado gracias a la experiencia del grupo de investigación FQM-383 (NanoVal) en química a nanoescala, catálisis heterogénea y valorización de residuos/biomasa. Más en detalle, los estudios de investigación de la tesis doctoral demostraron la potencialidad de las técnicas asistidas por microondas para el desarrollo de sistemas nanocatalíticos eficientes diseñados específicamente para aplicaciones fotoquímicas, síntesis química fina y producción de biocombustibles.6-10 Los resultados más importantes obtenidos durante la tesis doctoral se han descrito en tres artículos de investigación. Además, en la sección de introducción, un apartado va dedicado a resaltar la gran importancia de los nanocatalizadores en la producción de biocombustibles. El primer artículo de investigación, Microwave-assisted valorization of pig bristles: towards visible light photocatalytic chalcocite composites”, describe la preparación de compuestos nano-Cu2S de carbono mediante un método asistido por microondas rápido y de baja toxicidad.11 La síntesis se llevó a cabo empleando etilenglicol como disolvente, cloruro de cobre como precursor de metal y pelos de cerdo de desecho como fuente de azufre y carbono, evitando el uso de cualquier precursor de azufre tóxico (por ejemplo, H2S, tiourea). La alta adsorción por microondas y la alta viscosidad del etilenglicol permitieron la preparación de compuestos de carbono Cu2S homogéneos en pocos minutos (4 minutos a 200 ° C trabajando en un horno de microondas multimodo). Por el contrario, el calentamiento convencional necesitó tiempos de reacción más largos, dando como resultado un material de carbono Cu2S poco homogéneo y poco activo. El compuesto así producido se ha caracterizado por difracción de rayos X (XRD), fisisorción de nitrógeno (modelo BET), microscopía electrónica de barrido / espectroscopía de rayos X dispersiva de energía (SEM-EDX) y espectroscopía UV-Vis. El compuesto de carbono Cu2S se ha utilizado con éxito para la foto degradación del rojo de metilo, un colorante contaminante común, bajo irradiación de luz LED visible, que conduce a ca. 40% de degradación en 3 horas. En el segundo artículo de investigación, “Heterogeneously Catalyzed Synthesis of Imidazolones via Cycloisomerizations of Propargylic Ureas Using Ag and Au/Al SBA-15 Systems”, se han estudiado diversos caminos ecológicos para la cicloisomerización de ureas propargílicas12. Específicamente, diferentes nanocatalizadores de oro y plata se han preparado soportando las nanopartículas metálicas sobre sílice mesoporosa (AlSBA-15) utilizando mecanoquímica y radiación microondas. Los catalizadores se han utilizado como sistemas heterogéneos en la síntesis asistida por microondas de una biblioteca de imidazolonas a través de un estudio secuencial destinado a cambiar la reacción a condiciones operativas más ecológicas. Los sistemas empleados evitaron la utilización de bases fuertes, como NaOH, o catalizadores metálicos homogéneos y caros. Las mejores condiciones se han combinado para catalizar la cicloisomerización de las propargilureas utilizando solo agua como disolvente y promotor de la reacción. Los resultados demostraron que el disolvente seleccionado tiene una gran influencia en las reacciones, en concreto el tolueno promovió las reacciones de N-ciclación, el etanol favoreció la ciclación de las ureas propargílicas caracterizadas por más grupos de extracción de electrones y el agua favoreció la ciclación de la urea propargílica que contiene compuestos donadores de electrones en la estructura. El tercer artículo de investigación, “Efficient and Environmentally Friendly Microwave-Assisted Synthesis of Catalytically Active Magnetic Metallic Ni Nanoparticles” describe la preparación de níquel metálico y magnético mediante un método simple y rápido asistido por microondas utilizando un reactor monomodo (CEM Discover, CEM Corp .) 13 La síntesis se ha llevado a cabo utilizando cloruro de níquel como precursor metálico y una mezcla de etilenglicol y etanol (o isopropanol) como disolvente y agente reductor. Un buen estudio llevado a cabo variando la relación molar de etilenglicol y etanol en función de la temperatura de reacción ha llevado a las condiciones de reacción donde se produjo la reducción de níquel. El mejor rendimiento (71%) se ha logrado operando a 250 ° C durante 5 minutos bajo irradiación de microondas. El mecanismo de reacción para la oxidación de etilenglicol y la reducción de Ni2 + se ha demostrado mediante el análisis de cromatografía de gases-espectrometría de masas (GC-MS), mientras que el comportamiento de la mezcla y su punto de burbuja en función de la presión del registrador se ha simulado con PRO/II software (Grupo Schneider Electric). Las nanopartículas han sido analizadas por difracción de rayos X (XRD), microscopía de emisión de barrido (SEM), microscopía electrónica de transmisión (TEM) y susceptibilidad de masa magnética. El área superficial ha sido determinada por la fisisorción de nitrógeno (modelo BET). Las nanopartículas han mostrado una buena actividad en la hidrogenolisis del bencil fenil éter (BPE), un compuesto modelo de lignina, con una conversión máxima del 24%, y reutilización de hasta 5 ciclos sin aparente pérdida de actividad

Reducing the brittleness of poly-furfuryl alcohol resin used in composites

The thermoset market is dominated with petroleum-based products. The rising concerns on depletion of non-renewable resources and climate change has motivated researches and industries to find green alternatives for petroleum based materials. The thermoset polymer poly-furfuryl alcohol (PFA) displays good chemical, viscoelastic and moisture stability properties and importantly is bio-based, however, the cured PFA resin is very brittle. The approach of incorporating different types of particulate fillers into the PFA matrix and reinforcing the PFA matrix with flax fabric was used to address the brittleness issue associated with PFA. In the first study, flax fabric was treated with a diammonium phosphate based flame-retardant to reduce the flammability. Compression moulding was used to produce PFA biocomposites and PFA laminates. The effect of the flame-retardant was investigated using Scanning electron microscope (SEM), x-ray diffraction (XRD), fourier transform infrared (FTIR), and cone calorimeter, flexural and tensile tests. The flame-retardant treatment significantly improved the flammability properties, however, decreased the flexural and tensile properties. In the second study, 10 different fillers were selected, these being; ZnO, Clay, montmorillonite (MMT), Rubber, Chitin, Starch, CaCO3, Chitosan, Lignin and TiO2. These fillers were incorporated into the PFA resin at 2% and 5% concentration and reinforced with untreated (UT) flax fabric and flame-retardant (FR) treated flax fabric. Flexural, tensile and izod impact tests were performed on the cured laminates. Thermogravimetric analysis (TGA), SEM and micro x-ray computed tomography scan (CT scan) analysis was performed on selected samples. The inclusion of MMT and Rubber significantly increased the strength and the stiffness of the PFA/UT-Flax laminate while Clay and ZnO reduced the brittleness of the PFA/UT-Flax laminate. FR laminates generally exhibited poor mechanical properties regardless of the type of filler. This was the result of FR damaging the flax fibres during the compression moulding process and hindered the interaction between the PFA matrix and flax fabric. TGA results showed that FR treatment increased the thermal stability of the PFA laminate. SEM and CT scan analysis illustrated the large amount of voids between fabric layers, especially for UT-Flax laminates. The fillers MMT, Rubber and ZnO had a positive effect on the mechanical properties of UT-Flax laminates and therefore were used in the third study. A Box Behnken design of experiment was developed in which the concentration of MMT, Rubber and ZnO was varied between 0 – 5%. Multiple linear regression was used to model the mechanical properties of the PFA/UT-Flax laminates based on a full quadratic model. An optimized filler combination was determined with Solver ®. The experimental results of the optimised PFA/UT-Flax laminate were compared to the values predicted with the statistical model