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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

An Introductory Study of Solid Materials for Capture and Catalysis of Waste Stream Chemicals

Butler, Steven Kyle 01 June 2018 (has links)
Heterogeneous catalysts are key materials in research and industry. Herein we study two materials in different stages of development toward being applied as heterogeneous catalysts. First, MoO3SnO2 was synthesized and studied as a catalytic system similar to Sn-beta zeolites. While the Mo-based catalyst did not show similar activity to Sn-beta, it did show interesting reactivity in activating carbonyls and oxidizing organic substrates. Second, a method was developed for grafting amines onto carboxylic acid functionalized carbon nanotubes for CO2 capture. The method was successful for grafting monomer ethylamine groups onto CNT and can be further developed to allow for polymeric amine groups to be grafted.
52

Process Optimization for the Synthesis of Gold Nanoparticles from a Mixed Metal Precursor Solution

Dill, Kathryn Ann 01 January 2018 (has links)
Separation methods involving a mixture of metals typically include upfront processing that leads to one final product. To lower the waste and ultimately environmental burden, the potential to synthesize multiple functional products from a mixed metal precursor solution is explored. The initial precursor solutions contained varying ratios of gold and copper, gold and nickel, and finally a ternary solution of gold, copper, and nickel. The amount of gold was kept constant, while the amount of copper and/or nickel was sequentially increased. Two separate synthesis processes were tested, the traditional Turkevich method involving trisodium citrate and another chemical reduction method involving sodium borohydride. The particle size and chemical composition of the synthesized particles were characterized using TEM, DLS and ICP-OES. It was determined that gold nanoparticles still formed at a ratio of 1 to 2 gold to copper while using trisodium citrate or sodium borohydride as the reducing agent. The same limiting ratio was observed for the gold to nickel reactions in the presence of either trisodium citrate or sodium borohydride. The ternary mixture limit for gold nanoparticle formation was a molar ratio of 1 to 1 to 1 gold to copper to nickel. The repeatability and stability results for the optimized binary reaction conditions indicate that using sodium borohydride as the reducing agent consistently produces more stable particle suspensions. Quantifying the environmental impact using green chemistry metrics indicate the Turkevich reactions for the optimized reactions have the lower environmental factors.
53

Sustainable Production of Bio-based Succinic Acid from Plant Biomass

Lo, Enlin 24 June 2018 (has links)
Succinic acid is a compound used for manufacturing lacquers, resins, and other coating chemicals. It is also used in the food and beverage industry as a flavor additive. It is predominantly manufactured from petrochemicals, but it can also be produced more sustainably by fermentation of sugars from renewable feedstocks (biomass). Bio-based succinic acid has excellent potential for becoming a platform chemical (building block) for commodity and high-value chemicals. In this study, we focused on the production of bio-based succinic acid from the fiber of sweet sorghum (SS), which has a high fermentable sugar content and can be cultivated in a variety of climates and locations around the world. To avoid competition with food feedstocks, we targeted the non-edible ‘bagasse’, which is the fiber part after extracting the juice. Initially, we studied various conditions of pretreating SS bagasse to remove most of the non-fermentable portions and expose the cellulose fibers containing the fermentable sugars (glucose). Concentrated (83%) phosphoric acid was utilized at mild temperatures of 50-80 °C for 30-60 minutes at various bagasse loadings (10-15%) using a partial factorial experimental design. After pretreatment, the biomass was subjected to enzymatic hydrolysis with commercial cellulase enzyme (Cellic® Ctec2) to identify the pretreatment conditions that lead to the highest glucose yield that is critical for the production of succinic acid via fermentation with the bacterium Actinobacillus succinogenes. As the pretreatment temperature and duration increased, the bagasse color changed from light brown to dark brown-black, indicating decomposition, which ranged from 15% to 72%. The pretreatment results were fitted with an empirical model that identified 50 °C for 43 min at 13% solids loading as optimal pretreatment conditions that lead to the highest glucose release from sweet sorghum bagasse. Biomass pretreated at those conditions and subjected to separate enzymatic hydrolysis and fermentation with A. succinogenes yielded almost 18 g/L succinic acid, which represented 90% of the theoretical yield, a very promising performance that warranties further investigation of bio-based succinic acid production from sweet sorghum bagasse, as a more sustainable alternative to succinic acid produced from fossil sources, such as oil.
54

Nanoréacteurs pour la catalyse en milieux aqueux / Nanoreactors for catalysis in aqueous media

Deraedt, Christophe 19 December 2014 (has links)
Cette thèse concerne l’élaboration par réaction “click” CuAAC denouveaux nanomatériaux présentant diverses applications, en particulier en catalyse.Ces macromolécules (dendrimères, dendrimères supportés sur oxide et polymères)comprenant des cycles 1,2,3-triazoles ont été utilisés pour stabiliser desnanoparticules essentiellement de palladium actives en catalyse de couplage C-C,réduction du 4-nitrophenol et oxydation des alcools dans des solvants aqueux.L’utilisation de ces nanoparticules à l’échelle du ppm traduit leur efficacité et l’aspectécologique visé avec ce projet. L’intégration d’unités triazolylbiferrocéniques au seinde ces polymères a permis d’étendre la gamme d’applications de ces matériaux auxsondes électrochimiques, réduction d’ions métalliques en nanoparticules, composéspoly-électrolytes, poly-électrochromes, à valence mixte. L’imprégnation denanoparticules de palladium stabilisées par des dendrimères sur support magnétiquea permis d’augmenter la robustesse des catalyseurs ainsi que leur recyclablité paraimantation. / This thesis concerns the synthesis by “click” CuAAC reactions of newnanomaterials that have various applications, in particular in catalysis. Thesemacromolecules are dendrimers, supported dendrimers and polymers that contain1,2,3-triazole rings and were used in the stabilization of essentially palladiumnanoparticles (PdNPs). These PdNPs are extremely active in the catalysis in greensolvents of C-C coupling, reduction of 4-nitrophenol and selective oxidation ofalcohols. The use of these nanoparticle catalysts at the ppm level shows theirefficiency and their ecological aspect. The integration of biferrocene units in thepolymers allowed expanding their applications to electrochemical sensors, reductantsof metallic ions to nanoparticles, polyelectrolytes, polyelectrochromic, and mixedvalentcomplexes. The impregnation of PdNPs stabilized by dendrimers on magneticsupport led to the increase of the catalyst robustness and recyclability using amagnet.
55

Étude de nouveaux systèmes catalytiques pour la valorisation de la lignine par oxydation / Study of new catalytic systems for lignin valorization by oxidation

Napoly, Francois 13 October 2014 (has links)
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
56

Life Cycle Assessment as a Tool for Green Chemistry: Application to Different Advanced Oxidation Processes for Wastewater Treatment

Muñoz Ortiz, Ivan 05 May 2006 (has links)
El objetivo de la tesis es contribuir a la aceptación del Análisis de Ciclo de Vida (ACV) como herramienta metodológica para la evaluación medioambiental de procesos químicos diseñados siguiendo las pautas de la Química Verde. Se pretende asimismo complementar e integrar la evaluación ambiental con la correspondiente evaluación económica, también desde una perspectiva de ciclo de vida. Con el objetivo de mostrar la potencial utilidad del ACV en este ámbito, se llevan a cabo dos casos de estudio en los cuales se evalúan diferentes Procesos Avanzados de Oxidación (PAOs) para el tratamiento de aguas residuales de la industria conteniendo contaminantes orgánicos persistentes. Las tecnologías evaluadas son: fotocatálisis en fase heterogénea, fotocatálisis en fase homogénea mediante procesos foto-Fenton, y ozonización. El primer caso de estudio se lleva a cabo a partir de datos a escala de laboratorio, mientras que el segundo caso de estudio, de carácter más detallado, se lleva a cabo mediante datos de planta piloto e industrial. Ambos estudios complementan la dimensión ambiental con la dimensión económica, utilizando la herramienta Coste del Ciclo de Vida (CCV). A continuación, se lleva a cabo una discusión sobre la utilidad del ACV en el ámbito de los procesos químicos, dependiendo de la escala de análisis: desde el laboratorio hasta la aplicación comercial. Finalmente, se presentan las conclusiones globales de la tesis, que pueden resumirse del siguiente modo:- La cuantificación de los avances alcanzados mediante la aplicación de los principios de la Química Verde requiere herramientas, habiéndose mostrado la potencial utilidad del ACV en este ámbito mediante dos casos de estudio sobre PAOs.- Se ha mostrado la posibilidad de aplicar el ACV tanto al nivel más básico de la Química Verde (laboratorio) hasta el más avanzado (aplicación comercial). Sin embargo los resultados obtenidos mediante ACVs basados en datos de laboratorio no necesariamente coinciden con los obtenidos en un estudio detallado, debido a: 1) falta de optimización de los procesos en laboratorio y 2) exclusión de procesos o fases del ciclo de vida que pueden ser relevantes, debido a la falta de datos. Por ello, tales estudios deben ser utilizados únicamente como evaluaciones preliminares.- El ACV despliega su potencialidad en estudios detallados, utilizando datos originados a escala piloto o industrial. Asimismo, el CCV se presenta como un complemento muy apropiado para el ACV, principalmente también en el caso de estudios detallados. / The goal of the thesis is to contribute to the acceptance of Life Cycle Assessment (LCA) as a methodological tool for environmental evaluation of chemical processes designed by following the guidelines of Green Chemistry. This work also intends to complement and to integrate in the same framework the environmental assessment with the respective economic assessment, taking into account a life cycle perspective as well. In order to demonstrate the potential suitability of the LCA tool in this context, two case studies are carried out on the subject of Advanced Oxidation Processes (AOPs) for treating industrial wastewaters containing persistent organic pollutants. In particular, the evaluated AOP technologies are: heterogeneous photocatalysis, homogeneous photo-Fenton, and ozonation. The first case study is carried out by exclusively using data derived from laboratory experiments, while the second case study is more detailed, and carried out by using data from pilot plants and industrial plants. Both studies include, along with the environmental assessment, the corresponding economic assessment, based on Life Cycle Costing (LCC). Following these studies, a discussion is made on the suitability of LCA in the context of chemical processes depending on the scale of analysis. Finally, the overall conclusions of the thesis are outlined, which can be summarised as follows:- In order to assess the advances derived from applying Green Chemistry principles in the design of chemicals and chemical processes, methodological tools are needed. This thesis supports that LCA can be used for such a purpose, as has been shown by means of two case studies on AOPs.- Application of LCA can be carried out at several stages: from the most basic, namely the laboratory scale, to the most advanced, namely commercial application. However, results obtained by means LCA studies based exclusively on laboratory-derived data do not necessarily match the results obtained in a detailed LCAs, mainly due to: 1) lack of optimization of the conditions in which the chemical process takes place in laboratory tests, and 2) excluding relevant operations or life cycle phases which are hardly quantifiable when evaluated from laboratory tests. For this reason, it is suggested that laboratory-derived LCAs should be used only as a means of obtaining preliminary environmental information.- The potential of LCA as a tool is displayed when detailed studies, based on large-scale application data, are carried out. The LCC tool, on the other hand, presents itself as a very suitable complement, mainly when performing detailed studies.
57

Development of Soft Chemical Processes: Preparation of TiO(2) Films and Powders at Low Temperature

Gutiérrez Tauste, David 25 April 2008 (has links)
El processament convencional de materials d'òxid de titani (TiO2) inherentment implica un consum energètic important i ha esdevingut una limitació tecnològica per a la fabricació de dispositius emprant substrats termolàbils així com per a la preparació de materials híbrids orgànic/TiO2. Aquesta tesi doctoral tracta del desenvolupament de processos químics per a la preparació de capes i pols de TiO2 d'acord amb principis de Química Verda, posant especial èmfasi en el processament a baixa temperatura. Plantejaments simples, benignes amb el medi ambient i de baix cost són els desitjats sota aquestes directrius. A més a més, els mètodes a baixa temperatura (idealment fins a un màxim proper a 100ºC) haurien de donar lloc a materials que exhibeixin propietats similars a aquells processats a alta temperatura o tractats solvotermalment. S'ha focalitzat especial interès en la recerca d'aplicacions pràctiques dels materials produïts en camps com la conversió d'energia solar i materials actuadors. / El procesamiento convencional de materiales de óxido de titanio (TiO2) inherentemente implica un consumo energético importante y ha resultado una limitación tecnológica para la fabricación de dispositivos utilizando substratos termolábiles así como para la preparación de materiales híbridos orgánico/TiO2. Esta tesis doctoral trata el desarrollo de procesos químicos suaves para la preparación de capas y polvos de TiO2 de acuerdo con principios de Química Verde, poniendo especial énfasis en el procesamiento a baja temperatura. Planteamientos simples, benignos con el medioambiente y de bajo conste son los deseados bajo estas directrices. Además, los métodos a baja temperatura (idealmente hasta un máximo próximo a 100ºC) deberían dar lugar a materiales que exhiban propiedades similares a aquellos procesados a alta temperatura o tratados solvotermalmente. Se ha centrado especial interés en la búsqueda de aplicaciones prácticas de los materiales producidos en campos como la conversión de energía solar y materiales actuadores. / Conventional high-temperature processing of titanium dioxide (TiO2) materials inherently implies important energy consumption and has became a technological limitation for fabricating devices employing thermolabile substrates as well as preparing hybrid organic/TiO2 materials. This PhD thesis deals with the development of chemical processes for preparing TiO2 films and powders fitting Green Chemistry principles, putting special emphasis on low-temperature processing. Simple, environmentally benign and low-cost approaches are desired upon these guidelines. Moreover, low-temperature methods (ideally up to a maximum closer to 100ºC) should give rise to materials exhibiting properties similar than those processed at high temperature or solvothermally treated. Special interest has been focused on finding practical applications of the as-prepared materials in fields such as solar energy conversion and actuating materials.
58

Synthesis Of Heteroaryl Substituted Dihydrofuran And Dihydropyran Derivatives By Green Chemistry Approach

Demirci, Sema 01 September 2009 (has links) (PDF)
The thesis subject is mainly involved in Green Chemistry approach. Thiophene, furan and pyridine carboxaldehydes were chosen as starting compounds and vinylation and allylation with Grignard reaction afforded the corresponding racemic heteroaryl substituted allylic and homoallylic alcohols. Subsequent resolution with enzymes (PS-Amano II, Lipozym and Novazym 435) gave enantiomerically enriched alcohols with the e.e. values varied between 65 and 99%. The absolute configurations of all substrates are known. As a result of O-allylation with the common procedure formed the feasible carbon backbone for the ring closing metathesis reaction. All ring closing metathesis reactions were performed by Grubbs&rsquo / catalyst with just 5% catalyst loading. The absolute configurations of dihydrofuran and dihydropyran derivatives are known, since the chiral center configurations of all substrates are preserved throughout all the applied processes.
59

Synthesis Of 2-heteroaryl Substituted Chiral Fused Cyclopenta[c]pyridine Derivatives Via Pauson-khand Reaction

Gumrukcu, Yasemin 01 October 2009 (has links) (PDF)
The racemic homoallylic and homopropargylic alcohol derivatives were resolved by applying chemoenzymatic method using various lipase type enzymes i.e., PS-C II, Lipozyme, CAL-B. The enantiomeric excess values of the resultant alcohols were determined by HPLC. These enantiomerically enriched homoallylic and homopropargylic alcohols were subjected to N-propargylation and N-allylation, respectively, by SN2 and modified Mitsunobu reactions. During the course of all reactions, stereochemistry of the chiral centers were under controlling according to the known reaction mechanisms. The resultant chiral N-tosylated enyne derivatives afforded the corresponding chiral fused cyclopenta[c]pyridinone derivatives (69, 73, 75 and 77) with acceptable chemical yields and excellent diastereoslectivity depending upon the conformational effect on the complete remote stereochemical control for the newly generated chiral centers. The chemoenzymatic applications done with biocatalysis (lipases) and the Pauson-Khand reaction are involved in &ldquo / Green Chemistry&rdquo / approach.
60

The application of green chemistry and engineering to novel sustainable solvents and processes

Marus, Gregory Alan 21 December 2011 (has links)
The implementation of sustainable solvents and processes is critical to new developments in reducing environmental impact, improving net efficiency, and securing economic profitability in the chemical and pharmaceutical industries. In order to address the challenge of sustainability, researchers have used switchable solvents for both reaction and separation by utilizing a built-in switch to undergo a step change in chemical and physical properties. This allows us to facilitate reactions in the solvent then activate the switch to enable separation and facile product recovery. Subsequently, we can recover the solvent for reuse and avoid energy- or waste-intensive separation processes; thus we are developing and using these switchable solvents as sustainable and environmentally benign alternatives to traditional processes. In this research, we enable the sustainable scale-up of a switchable solvent - piperylene sulfone - a "volatile" and recyclable DMSO replacement. In the development of this process, we improved the reaction performances and developed a green purification method. Furthermore, we enable and demonstrate the implementation of a Meerwein-Ponndorf-Verley (MPV) reduction, a pharmaceutically relevant reaction, into a continuous flow platform. The innovation of continuous flow processes can replace traditional batch reaction technology, and is indeed a key research area that has been acknowledged by the pharmaceutical industry. Additionally, we utilize the switchable sulfone solvents, piperylene and butadiene sulfone, for reaction and separation of HMF produced from monosaccharides as an alternative to a process which has been limited by an inefficient separation step.

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