Dissertationen: „Solvent system“

1

Ghosh, Gargi. „Investigation on solute-solute, solute-solvent and solvent-solvent interactions prevailing in some liquid system“. Thesis, University of North Bengal, 2009. http://hdl.handle.net/123456789/1351.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

2

Hoy, Thomas Lavelle. „Optimizing Solvent Blends for a Quinary System“. University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1462199621.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

3

Gupta, Bindu 1963. „Solubility of anthracene in complex solvent system“. Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/276989.

Der volle Inhalt der Quelle

Annotation:

The solubility of anthracene was measured in binary and ternary co-solvent-water systems. The binary systems consisted of water and a completely miscible organic solvent (CMOS); while the ternary system incorporated a partially miscible organic solvent (PMOS) into the binary systems. The data were used to test the following model:(UNFORMATTED TABLE OR EQUATION FOLLOWS) log Sᵃ(c,p,w) = log Sᵃ(w) + f(c) σᵃ(c) + [(Sᴾ(w) 10 (f(c) σᴾ(c))/D(p)] σᵃ(p). (TABLE/EQUATION ENDS) The terms on the right of the equality sign are the aqueous solubility of anthracene, the solubility of anthracene in CMOS-water, and the solubility of anthracene due to the incorporation of the PMOS, respectively. This model predicts that the incorporation of a PMOS, as a solubilized solute, in CMOS-water mixtures can lead to an increase in the solubility of anthracene due to the cosolvency effect of the PMOS. The results indicate a good correlation between the observed vs. predicted increase in solubility. The deviations observed may be explained by the interactions between the solvent components.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

4

Fowler, Michael James. „Construction of prototype system for directional solvent extraction desalination“. Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/76130.

Der volle Inhalt der Quelle

Annotation:

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 37-38).
Directional solvent extraction has been demonstrated as a low temperature, membrane free desalination process. This method dissolves the water into an inexpensive, benign directional solvent, rejects the contaminants, then recovers pure water, and re-uses the solvent. In order to bring this technology closer to real world application, a continuous process prototype for a directional solvent extraction system was developed and tested. Octanoic acid was used as the solvent of choice, and a system capable of producing up to 7 gallons per day of fresh water was constructed. The system was tested to effectively desalinate the feed water, and the total system power was less than 7 kW. The system was constructed and first tested to run fresh water and solvent through it. Fresh water was dissolved in and separated, as expected, from the solvent at a rate of about 2 gpd. Saline water containing 3.5% sodium chloride was then used as feedwater and the desalinated water was recovered at a rate of about 1 gpd with an average salinity of 0.175%. Effective continuous operation of the directional solvent extraction prototype was demonstrated. Certain design improvements to increase efficiency, optimize component sizes, and decrease energy consumption are suggested. The demonstrated system has a wide range of applications, including production of fresh water from the sea, as well as, treatment of produced and flowback water from shale gas and oil extraction.
by Michael James Fowler.
S.B.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

5

Brunet, Jean-Christophe. „An expert system for solvent-based separation process synthesis“. Thesis, Virginia Tech, 1992. http://hdl.handle.net/10919/42949.

Der volle Inhalt der Quelle

Annotation:

Expert systems are being used more daily in chemical engineering. This work continues the development of an EXpert system for SEParation flowsheet synthesis named EXSEP. Written in Prolog, it can generate flowsheets for four multicomponent separations: distillation, absorption, stripping and liquid-liquid extraction. For these separations, we describe a large collection of heuristics (or rules) that are used for flowsheet synthesis. EXSEP uses several of these heuristics and the Kremser equation to test the thermodynamic feasibility of separation tasks. EXSEP requires only basic input data such as the expected component flow rates in each product and the component K-values. With those data, EXSEP searches for the sets of the number of theoretical stages, solvent flow rate, and component-recovery ratios that characterize a number of feasible and economical flowsheets. The use of the component assignment matrix (CAM) combined with Prolog list processing makes EXSEP very fast (several seconds) to generate solutions. We test EXSEP with several examples of industrial separation processes and compare the results with the literature. We also compare EXSEP results with rigorous simulations using commercial CAD software (e.g., DESIGN II). In most cases, EXSEP gives very similar and even better flowsheets. However, EXSEP is limited to dilute solvent-based separations and cannot solve problems where the major feed component is also the solvent (e.g. sour-water steam stripper). The development of EXSEP on IBM-PC makes it very "user friendly". In the future, EXSEP should be expanded with additional modules such as extractive and azeotropic distillation, and bulk absorption. It should also include modules for separation method and solvent selections, which are great challenges in flowsheet synthesis.
Master of Science

APA, Harvard, Vancouver, ISO und andere Zitierweisen

6

Tawfik, Wahid Yosry. „Design of optimal fuel grade ethanol recovery system using solvent extraction“. Diss., Georgia Institute of Technology, 1986. http://hdl.handle.net/1853/11152.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

7

BHANDARI, SHASHANK. „Design of a solvent recovery system in a pharmaceutical manufacturing plant“. Thesis, KTH, Skolan för kemivetenskap (CHE), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-190901.

Der volle Inhalt der Quelle

Annotation:

Solvents play a crucial role in the Active Pharmaceutical Ingredient (API) manufacturing and are used in large quantities. Most of the industries incinerate the waste solvents or send it to waste management companies for destruction to avoid waste handling and cross-contamination. It is not a cost effective method and also hazardous to the environment. This study has been performed at AstraZeneca’s API manufacturing plant at Sodertalje, Sweden. In order to find a solution, a solvent recovery system is modeled and simulated using ASPEN plus and ASPEN batch modeler. The waste streams were selected based on the quantity and cost of the solvents present in them. The solvent mixture in the first waste stream was toluene-methanol in which toluene was the key-solvent whereas in the second waste stream, isooctane-ethyl acetate was the solvent mixture in which isooctane was the key-solvent. The solvents in the waste stream were making an azeotrope and hence it was difficult to separate them using conventional distillation techniques. Liquid-Liquid Extraction with water as a solvent followed by batch distillation was used for the first waste stream and Pressure Swing Distillation was used for the second waste stream. The design was optimized based on cost analysis and was successful to deliver 96.1% toluene recovery with 99.5% purity and 83.6% isooctane recovery with 99% purity. The purity of the solvents was decided based on the quality conventions used at AstraZeneca so that it can be recovered and recycled in the same system. The results were favorable with a benefit of €335,000 per year and preventing nearly one ton per year carbon dioxide emissions to the environment. A theoretical study for the recovery system of toluene-methanol mixture was performed. The proposed design was an integration of pervaporation to the batch distillation. A blend of polyurethane / poly(dimethylsiloxane) (PU / PDMS) membrane was selected for the separation of methanol and toluene mixture. The results of preliminary calculations show 91.4% toluene recovery and 72% methanol recovery with desired purity.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

8

Abdul, Manaf Norhuda. „MANAGEMENT DECISION SUPPORT SYSTEM OF SOLVENT-BASED POST-COMBUSTION CARBON CAPTURE“. Thesis, The University of Sydney, 2016. http://hdl.handle.net/2123/16567.

Der volle Inhalt der Quelle

Annotation:

A management decision-support framework for a coal-fired power plant with solvent based post combustion CO2 capture (PCC) (integrated plant) is proposed and developed in this thesis. A brief introduction pertaining to the solvent-based PCC technology, thesis motivations and objectives are given in Chapter 1. Chapter 2 comprises a comprehensive literature review of solvent-based PCC plant from the bottom level (PCC instrumentation level) until the top level (managerial decision of PCC system). Chapter 3 describes the development of solvent-based PCC dynamic model via empirical methods. Open-loop dynamic analyses are presented to provide a deeper understanding of the dynamic behaviour of key variables in solvent-based PCC plant. Chapter 4 presents the design of the control architecture for solvent-based PCC plant. Two control algorithms developed, which utilise conventional proportional, integral and derivative (PID) controller and advanced model predictive control (MPC). Chapter 5 proposes a conceptual framework for optimal operation of the integrated plant. The MPC scheme is chosen as the control algorithm while mixed integer non-linear programming (MINLP) using genetic algorithm (GA) function is employed in the optimization algorithm. Both algorithms are integrated to produce a hybrid MPC-MINLP algorithm. Capability and applicability of the algorithm is evaluated based on 24 hours and annual operation of integrated plant. Chapter 6 extends the scope of Chapter 5 by evaluating the relevance of solvent-based PCC technology in the operation of black coal-fired power plant in Australia. This chapter considers a prevailing climate policy established in Australia namely Emission Reduction Fund (ERF). Finally, the concluding remarks and future extensions of this research are presented in Chapter 7.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

9

Mukherjee, P. „Solvent-free, triphase catalytic oxidation reactions over TS-1/H2O2 system“. Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 2000. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/2277.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

10

Alturaihi, Haydar. „Biocatalysis of lipoxygenase in a model system using selected organic solvent media“. Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=96760.

Der volle Inhalt der Quelle

Annotation:

The biocatalysis of commercially purified soybean lipoxygenase (LOX-1B: EC 1.13.11.12) in ternary micellar and neat organic solvent media, using linoleic acid as a substrate model, was investigated. The organic solvent, used throughout this study, was at different ratios in the ternary micellar system, composed of Tris-HCl buffer solution (0.1 M, pH 9.0) and 10 µM of Tween-40 as the surfactant. The results indicated a 1.4- and 1.7-fold increase in LOX activity when, respectively, 2% iso-octane or 2% hexane was used as the organic solvent in comparison to that in the aqueous medium. The kinetic parameters, including Km and Vmax values, the choice of the surfactant, the optimum reaction temperature and the optimum pH, were investigated. The effects of selected parameters, including initial water activity (aw, 0.23 to 0.75), agitation speed (0 to 200 rpm), reaction temperature (20 to 45ºC) and thermal stability of LOX activity in neat organic solvent, were also studied. The experimental findings showed that the Km and Vmax values in the ternary micellar system containing 2% hexane was calculated to be 7.7 µmol of linoleic acid and 30.0 nmol of linoleic acid hydroperoxides (HPODs)/mg protein/min, respectively, as compare to that of 20.7 µmol of linoleic acid and 8.3 nmol HPODs/mg protein/min in the neat organic solvent, respectively. The experimental results indicated that the major LOX specific activity, for both aqueous and ternary micellar systems, was measured at pH 9.0, with a minor one at pH 6.0 for the aqueous system and at pH 7.0 for the ternary micellar system. The activation energy (Ea) of the reaction system of LOX was 9.87 kJ/mol or 2.36 kcal/mol. The half-life (T50) for LOX was 27.61, 66.63 and 138.6 min for the aqueous, ternary micellar and neat organic media, respectively.
La biocatalyse de la lipoxygénase purifiée, obtenus à partir de la graine de soja (LOX-1B: EC 1.13.11.12), a été étudiée en milieux micellaire ternaire et en monophasique organique, en utilisant l'acide linoléique comme substrat modèle. Le solvant organique, utilisé dans cette étude, a été utilisé à différentes concentrations dans le système micellaire ternaire, composé d'une solution tampon Tris-HCl (0,1 M, pH 9,0) et 10 µM d'un surfactant, le Tween-40. Les résultats obtenus ont démontré qu'il y a une augmentation de 1,4 et 1,7 fois de l'activité enzymatique de la LOX en utilisant, respectivement, soit du l'iso-octane à 2% ou soit du l'hexane à 2%, comme le solvant organique en comparaison avec celle en milieux aqueux. Les paramètres cinétiques, comportant les valeurs de Km et de Vmax, le choix de surfactant ainsi que la température et le pH optimal de la réaction ont été étudiés. Les effets de différents paramètres tels que l'activité initiale de l'eau (aw) du 0,23 à 0,75, l'agitation du 0 à 200 rpm, la température de la réaction du 20 à 45ºC et la stabilité thermique de l'activité de la LOX en milieux monophasiques organiques ont été aussi étudiés. Les résultats obtenus tendent à montré que les valeurs de Km et de Vmax en système micellaire ternaire, contenant de l' hexane à 2%, ont été de 7,7 µmol d'acide linoléique et 30,0 nmol d'hydroperyde de l'acide linoléique (HPODs)/mg protéine/min, respectivement, en comparaison à des valeurs de 20,7 µmol d'acide linoléique et 8,3 nmol HPODs/mg protéine/min dans les milieux monophasiques organiques, respectivement. De plus, les résultats expérimentaux ont démontré que l'activité spécifique maximale de la LOX pour les deux systèmes aqueux et micellaire ternaire a été obtenue à pH 9,0, avec aussi une activité minimale à pH 6,0 pour le système aqueux et à pH 7,0 pour le système micellaire ternaire. L'énergie d'activation (Ea) du système de réaction de la LOX était d'une valeur de 9,87 kJ/mol ou 2,36 kcal/mol. La demi-vie (T50) de LOX a été déterminée à 27,61 min dans le milieu aqueux, 66,63 min dans le milieu micellaire ternaire et 138,6 min dans les milieux monophasiques organiques.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

11

Ploetz, Christopher Daniel. „Micelles of polybutadiene-b-poly(ethylene oxide) in a binary solvent system“. College Park, Md. : University of Maryland, 2008. http://hdl.handle.net/1903/8310.

Der volle Inhalt der Quelle

Annotation:

Thesis (M.S.) -- University of Maryland, College Park, 2008.
Thesis research directed by: Dept. of Chemical and Biomolecular Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

12

Das, Koyeli. „Physicochemical investigation of assorted interactions of some imperative compounds with the manifestation of solvation effects prevalent in diverse solvent systems“. Thesis, University of North Bengal, 2018. http://ir.nbu.ac.in/handle/123456789/2684.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

13

Onwukamike, Kelechukwu Nnabuike. „Sustainable cellulose solubilization, regeneration and derivatization in a DBU-CO2 switchable solvent system“. Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0016/document.

Der volle Inhalt der Quelle

Annotation:

Source de carbone la plus abondante du règne végétal et non concurrentielle de la chaîne alimentaire, la cellulose est une alternative aux ressources fossiles crédible pour le développement de nouveaux matériaux polymères. Néanmoins, à ce jour, les nombreux travaux décrits dans la littérature et visant la valorisation et la modification chimique de ce biopolymère fascinant ne répondent pas suffisamment, ou tout au moins que très partiellement, aux critères de durabilité. Pour répondre à ces critères de développement durable, le caractère renouvelable de la cellulose et les concepts de procédés propres et de chimie ‘verte’, doivent être réellement pris en compte. Ceci implique un choix réfléchi des solvants et réactifs utilisés, une maîtrise des procédés de modification chimique et bien évidemment une évaluation de la pertinence des produits formés, pour lesquels les propriétés obtenues doivent être innovantes et supérieures aux matériaux polymères existants. Cette thèse se divise en trois parties principales, à savoir la solubilisation, la régénération et la modification chimique de la cellulose. Tout au long de ce travail, une attention particulière a été portée sur la durabilité de sa transformation chimique pour viser l’élaboration de matériaux cellulosiques processables et aux propriétés innovantes. Dans la première partie de la thèse, un système composé d’un catalyseur organique nucléophile (DBU) et de CO2 a permis la dissolution rapide de la cellulose dans le DMSO. Une étude détaillée visant à optimiser le système DMSO-DBU-CO2 a été réalisée grâce à un suivi par spectroscopie infrarouge in situ. Ainsi, jusqu'à 8 % massique de cellulose ont pu être dissous en 15 minutes à 30 °C sous une faible pression de CO2 (2-5 bars). L’originalité de ce système commutable (fixation-relargage réversible du CO2), par comparaison aux autres solvants classiques de la cellulose, inclut une recyclabilité plus facile par simple dépressurisation du CO2 et une solubilisation rapide et douce, à plus bas coût, en comparaison aux systèmes utilisant les liquides ioniques. La mise en évidence de la création de fonctions carbonate par réaction avec différents composés électrophiles tels les halogénures d’alkyle a permis d’avoir une connaissance approfondie de ce système. L'optimisation réussie d'un système ‘propre’ permettant la dissolution de la cellulose nous a conduit à étudier sa régénération. Dans cet objectif, des aérogels de cellulose ont été préparés par un procédé de solubilisation, coagulation et lyophilisation. Différents paramètres ont été examinés tels la concentration en cellulose, le solvant de coagulation ou encore la nature et concentration en super-base (DBU-CO2), sur les propriétés des aérogels (densité, morphologie, taille des pores). Les résultats obtenus démontrent que des aérogels avec une densité entre 0.05 et 1,2 g/cm3, des porosités entre 92 et 97 % et des tailles de pore entre 1,1 et 4,5 μm ont été obtenus. Enfin, l’analyse des aérogels par microscopie électronique à balayage (SEM), a révélé la formation de réseaux de cellulose interconnectés et macroporeux. La modification chimique de la cellulose pour l’élaboration de matériaux processables aux propriétés innovantes fait l’objet de la troisième partie de la thèse. Cette partie est divisée en deux sous-parties: la dérivatisation de la cellulose par réaction de transestérification d’une part, et par réaction multi-composants, d’autre part. Dans la première sous-partie et gardant à l'esprit les principes de la chimie verte, la nature unique du système commutable DBU-CO2 amenant un changement d’hydrophilie du squelette cellulosique a permis l’utilisation directe de l’huile de tournesol pour la transestérification de la cellulose. [...]
As the most abundant source of carbon in our planet, without any competition with food or feed supplies, cellulose is a viable alternative to replace the widely used and unsustainable fossil-based polymers. However, the majority of researchers working on this fascinating biopolymer fail to incorporate sustainability considerations during cellulose chemical transformation to make materials. The consequence is a shift of the “environmental burden” to other stages of the process cycle. Therefore, to ensure sustainability, both the renewability feature of cellulose as well as sustainability considerations concerning its transformation processes are necessary. This implies to consider the solvent, the reactants, the derivatization process and the wastes produced as well as an evaluation of the suitability of the resultant products, for which relevant properties have to be obtained to compete with existing alternatives. This thesis is therefore divided into three main parts (solubilization, regeneration and derivatization of cellulose), and addresses the various concerns of sustainability during cellulose transformation with an end-goal of making processable materials.In the first part of the thesis, a sustainable solvent system for cellulose was investigated. In this regard, a detailed optimization study of the DBU-CO2 switchable solvent system was performed using in-situ infrared spectroscopy. Upon optimization, up to 8 wt.% cellulose could be dissolve within 15 min at 30 °C using low CO2 pressure (2-5 bar). What makes this solvent system sustainable, when compared to other classical cellulose solvents, includes: easier recyclability by simple release of the CO2 pressure, fast and mild solubilization and lower cost compared to ionic liquids. Finally, by successfully trapping the formed in-situ cellulose carbonate using an electrophile, a clearer understanding of this solvent system was established.The successful optimization of a sustainable solvent system for cellulose led to the second part of the thesis: the regeneration of cellulose. Here, the general solubilization and coagulation ways followed by freeze-drying was adopted to prepare cellulose aerogels. Various processing conditions such as cellulose concentration, coagulating solvent and super base, were investigated on their effect of the aerogels properties (density, morphology, pore size). The obtained results showed aerogels with densities between 0.05 and 1.2 g/cm3, porosities between 92 and 97 % and pore sizes between 1.1 and 4.5 μm. In addition, from scanning electron microscopy (SEM), open large macroporous inter-connected cellulose networks were observed.The derivatization of cellulose to make thermally processable materials is covered in the third part of the thesis. This part is divided into two sub-parts; transesterification and multicomponent reaction modification. [...]
Als Kohlenstoffquelle mit der größten Verfügbarkeit auf unserem Planeten, ohne Konkurrenz zur Lebens- und Futtermittelversorgung, stellt Cellulose eine interessante Alternative dar, um die vielfältig genutzten, nicht-nachhaltigen Polymere auf Erdölbasis zu ersetzen. Die Mehrheit der Forscher, die mit diesem faszinierenden Biopolymer arbeiten, vernachlässigt allerdings Überlegungen zur Nachhaltigkeit in die chemische Modifizierung von Cellulose bei der Herstellung von Materialien zu integrieren. Die Konsequenz dessen ist eine Verlagerung der Umweltbelastung auf andere Abschnitte des Prozess-Zyklus. Um Nachhaltigkeit sicherzustellen, sind deshalb sowohl der erneuerbare Aspekt von Cellulose als auch Überlegungen zur Nachhaltigkeit im Reaktionsprozess wichtig. Dies beinhaltet die Berücksichtigung des Lösungsmittels, die Reaktanden, des Derivatisierungsprozesses, die produzierten Abfälle sowie eine Beurteilung der Nachhaltigkeit der resultierenden Produkte, die relevante Eigenschaften aufweisen müssen um mit bestehenden Alternativen konkurrieren zu können. Diese Arbeit ist deshalb in drei Teile gegliedert (Löslichkeit, Rückgewinnung und Derivatisierung von Cellulose) und befasst sich mit den verschiedenen Aspekten der Nachhaltigkeit während der Umsetzung von Cellulose mit dem Ziel, verarbeitbare Materialien herzustellen.Im ersten Teil der Arbeit wurde ein nachhaltiges Lösungsmittelsystem für Cellulose untersucht. In diesem Zusammenhang wurde eine detaillierte Optimierungsstudie des DBU-CO2 schaltbaren Lösungsmittelsystems mittels in-situ Infrarot Spektroskopie durchgeführt. Nach der Optimierung konnten bis zu 8 Gew.-% Cellulose innerhalb von 15 min. bei 30°C und einem niedrigen CO2-Druck (2-5 bar) gelöst werden. Verglichen mit klassischen Lösungsmitteln für Cellulose weist dieses Lösungsmittelsystem verschiedene nachhaltige Aspekte auf: Einfaches Recycling durch entfernen des CO2-Drucks, schnelles und mildes Auflösen und geringere Kosten als ionische Flüssigkeiten. Durch erfolgreiches Abfangen des in-situ gebildeten Cellulose-Carbonats mit einem Elektrophil, konnte schließlich ein besseres Verständnis dieses Lösungsmittelsystems erreicht werden. Die erfolgreiche Optimierung eines Lösungsmittelsystems für Cellulose führte zum zweiten Teil der Arbeit: der Regenerierung von Cellulose. Hier wurde der bereits mit anderen Systemen beschriebene Weg von Lösen und Ausfällen, gefolgt von Gefriertrocknen übernommen, um Cellulose-Aerogele herzustellen. Verschiedene Bedingungen bei der Verarbeitung wie die Cellulose-Konzentration, Lösungsmittel zum Ausfällen und die Superbase und deren Effekt auf die Eigenschaften der Aerogele (Dichte, Morphologie und Porengröße) wurden untersucht. So wurden Aerogele mit einer Dichte von 0.05-1.20 g/cm3, Porositäten zwischen 92 und 97% und Porengrößen zwischen 1.1 und 4.5 μm erhalten. Zusätzlich wurden im Rasterelektronenmikroskop offene große und makroporöse, miteinander verbundene Cellulose-Netzwerke beobachtet. [...]

APA, Harvard, Vancouver, ISO und andere Zitierweisen

14

Panczer, Robert John. „Soil Remediation using Solvent Extraction with Hydrodehalogenation and Hydrogenation in a Semicontinuous System“. Scholar Commons, 2014. https://scholarcommons.usf.edu/etd/5092.

Der volle Inhalt der Quelle

Annotation:

The objective of this thesis is to aid in the development of Remedial Extraction And Catalytic Hydrodehalogenation (REACH), a green remediation technology used to remove and destroy halogenated hydrophobic organic compounds from soil. REACH has no secondary waste streams, uses an environmentally benign solvent, and aims to catalytically destroy rather than transfer the organic contaminants into a different phase. In this thesis, a bench-top semicontinuous model of the proposed remediation technology was constructed and used to extract the model contaminant, 1,2,4,5-tetrachlorobenzene, from soil and to convert it to an acceptable end product, cyclohexane. Palladium was used as a catalyst for hydrodehalogenation, which converted the tetrachlorobenzene to benzene. Rhodium was used to catalyze the hydrogenation of benzene to cyclohexane. A novel method, ultraviolet solvent treatment, was proposed to mitigate catalyst deactivation that occurs because of extracted chemicals contained in the contaminated soil. The goal of this treatment is to degrade organic matter that is suspected of causing catalyst deactivation. The REACH process was found to successfully extract TeCB from the soil, but only partial conversion from TeCB to cyclohexane occurred. Catalyst deactivation was the suspectedcause of the low amount of conversion observed. Hydrogen limitation was also tested as a cause of limited conversion, but was not found to be a contributor. Ultraviolet solvent treatment was tested as a means of mitigating catalyst deactivation. However, the treatment was not effective in making a profound difference in stopping the catalyst from deactivating. The experiments conducted in this research show that REACH has the potential to become a viable technology for cleaning soil contaminated with halogenated organic compounds. However, future research needs to be done to greatly reduce the severity of catalyst deactivation and to determine with which other halogenated organic compounds the technology works well.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

15

Vázquez-Figueroa, Eduardo. „Development of a novel dehydrogenase and a stable cofactor regeneration system“. Diss., Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/31685.

Der volle Inhalt der Quelle

Annotation:

The first goal of this work focused on the development of an amine dehydrogenase (AmDH) from a leucine dehydrogenase using site-directed mutagenesis. We aimed at reductively aminating a prochiral ketone to a chiral amine by using leucine dehydrogenase (LeuDH) as a starting template. This initial work was divided into two stages. The first focused mutagenesis to a specific residue (K68) that we know is key to developing the target functionality. Subsequently, mutagenesis focused on residues known to be in close proximity to a key region of the substrate (M65 and K68). This approach allowed for reduced library size while at the same time increased chances of generating alternate substrate specificity. An NAD+-dependent high throughput assay was optimized and will be discussed. The best variants showed specific activity in mU/mg range towards deaminating the target substrate. The second goal of this work was the development of a thermostable glucose dehydrogenase (GDH) starting with the wild-type gene from Bacillus subtilis. GDH is able to carry out the regeneration of both NADH and NADPH cofactors using glucose as a substrate. We applied the structure-guided consensus method to identify 24 mutations that were introduced using overlap extension. 11 of the tested variants had increased thermal stability, and when combined a GDH variant with a half-life ~3.5 days at 65℃ was generated--a ~10⁶increase in stability when compared to the wild-type. The final goal of this work was the characterization of GDH in homogeneous organic-aqueous solvent systems and salt solutions. Engineered GDH variants showed increased stability in all salts and organic solvents tested. Thermal stability had a positive correlation with organic solvent and salt stability. This allowed the demonstration that consensus-based methods can be used towards engineering enzyme stability in uncommon media. This is of significant value since protein deactivation in salts and organic solvents is not well understood, making a priori design of protein stability in these environments difficult.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

16

Myatt, Matthew James. „Confocal microscopy of a ternary polymer system undergoing phase separation due to solvent loss“. Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.619803.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

17

Fullarton, Claire. „Working towards a new sustainable rechargeable battery : zinc, conducting polymer and deep eutectic solvent system“. Thesis, University of Leicester, 2015. http://hdl.handle.net/2381/31863.

Der volle Inhalt der Quelle

Annotation:

Electronically conducting polymers based on functionalised thiophenes and pyrroles have continued to stimulate academic interest as well as starting to be employed in practical applications and uses. This thesis describes studies of the electronic properties of mixed thiophene-pyrrole polymers (based on custom synthesised mixed monomer precursors) and polymers electrodeposited from commercially available monomers, pyrrole and 3,4-ethylenedioxythiophene, in respect to energy storage applications including batteries and ion selective membranes. In such applications the movement of ion and solvent through the polymer film during oxidation and reduction cycles is critical to application and function, e.g. charging rate, metal ion permeability or adhesion stability. Recently the unexpected behaviour of polypyrrole in choline chloride based ionic liquids has been described. These liquids are especially attractive because of their unique solubility profiles, high stability, low volatility and low toxicity. This thesis describes the electrochemical characterisation, DC capacitance behaviour and ion/solvent transport properties of conducting polymers using a range of electrochemical methodologies in combination with acoustic impedance electrochemical quartz crystal microbalance techniques (EQCM) and X-Ray Photo-electron Spectroscopy (XPS). The behaviour of several mixed thiophene-pyrrole films, polypyrrole and poly 3,4-ethylenedioxythiophene in different electrolyte media; deep eutectic solvents (DESs), conventional organic solvents and aqueous media are contrasted in this thesis. PEDOT and one of the mixed thiophene-pyrrole polymers (poly 2-(thiophene-2-yl)-1H pyrrole) gave the highest DC capacitances of the polymers investigated, with high values observed in both choline chloride based (Type III) and zinc based (Type IV) DESs. The ion dynamics of the polymers p-doping in the DESs, observed to fit gravimetric data recorded, was able to show a marked difference in the ion transfers between DES types and a conventional organic solvent, acetonitrile. Both polymers in acetonitrile and the zinc based DES (ZnCl2 / EG) satisfied the electro-neutrality condition through dominance of anion transfers. Whereas, polymers in the choline chloride based DES (Ethaline) satisfied the electro-neutrality condition through dominance of choline cation transfers (in the opposite direction to anion transfers). This research involved work towards the development of a new class of rechargeable batteries based on a Zinc-Polymer system incorporating a novel, inexpensive, environmentally sustainable solvent. This work is necessitated by the problems associated with petrol and diesel powered vehicles and the limitations of batteries available for electric vehicles.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

18

Ray, Tanusree. „Exploration of assortment of interfaces of some lonik liquids in solvent system by physicochemical approach“. Thesis, University of North Bengal, 2016. http://ir.nbu.ac.in/handle/123456789/2743.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

19

Redha, Batul H. „Impact of mixed solvent on co-crystal solubility, ternary diagrams and crystallisation scale-up. Crystallisations of Isonicotinamide ¿Benzoic Acid Co-crystals from Ethanol ¿Water Co-solvent System“. Thesis, University of Bradford, 2012. http://hdl.handle.net/10454/5683.

Der volle Inhalt der Quelle

Annotation:

The production of stable solid crystalline material is an important issue in the pharmaceutical industry and the challenge to control the desired active pharmaceutical ingredient (API) with the specific chemical and physical properties has led to more development in the drug industry. Increasing the solubility and the dissolution of the drug will increase its bioavailability; therefore the solubility can be improved with the change in the preparation method. The formation of co-crystals has emerged as a new alternate to the salts, hydrates and solvate methods since the molecules that cannot be formed by the usual methods might crystallise in the form of co-crystals. Co-crystals are multicomponent crystals which can be known as supramolecules and are constructed by the non covalent bonds between the desired former and co-former. Therefore the synthon approach was utilised to design co-crystals with the specific properties, this involves the understanding of the intermolecular interactions between these synthons. These interaction forces can be directed to control the crystal packing in the design of the new crystalline solid with the desired chemical and physical properties. The most familiar synthon was the amide group with its complementary carboxylic group, in this work isonicotinamide and benzoic acid were chosen to design co-crystal and much literature exist that introduce the determination of co-crystal growth from these two compounds. The growth of co-crystals was carried out in water, ethanol and ethanol / water mixed solvent (30 - 90 % ethanol) by utilising the Cryo-Compact circulator. Co-crystals (1:1) and (2:1) were grown in ethanol and water respectively and a mixture of both phases were grown in the mixed solvent. All the phases were examined by powder X-ray diffraction (PXRD), Raman, Infrared and 1H-NMR spectroscopy. The solubility of isonicotinamide, benzoic acid, co-crystals (1:1) and (2:1) in water, ethanol and ethanol/water mixed solvent (30 - 90 % ethanol) were determined at 25 °C, 35 °C and 40 °C by utilising the React-Array Microvate. It was important to understand some of the thermodynamic factors which control the formation of these polymorphs such as the change in the enthalpy and the change in the entropy. Also it was important to study the pH behaviour during dissolution of the former, co-former and co-crystals in water, ethanol and ethanol/water mixed solvent (30 - 90 % ethanol) in-order to examine the affect of the solvent composition on the solubility and to identify if some ions were formed during the dissociation and how this could affects the formation of co-crystals. A discussion has been introduced in this research of how similar solubility of the compounds maps the formation of the typical ternary phase diagram of the mixture of 1:1 while compounds with different solubility maps the formation of skewed phase diagram as shown in section 1.6.2.3. In this project an isotherm ternary phase diagram at 20 °C and 40 °C was constructed to map the behaviour of benzoic acid and isonicotinamide and to show all possible phases formed and the regions where all phases are represented in the ternary phase diagram were determined by the slurry method. The ternary phase diagram was used to design a drawn out and cooling crystallisation at 100 cm3 solution of 50 % ethanol / water mixed solvent and a study of the impact of seeds of co-crystals 1:1 on the cooling crystallisation method.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

20

Chandra, Alind. „THERMODYNAMIC MODELING AND EQUILIBRIUM SYSTEM DESIGN OF A SOLVENT EXTRACTION PROCESS FOR DILUTE RARE EARTH SOLUTIONS“. UKnowledge, 2019. https://uknowledge.uky.edu/mng_etds/53.

Der volle Inhalt der Quelle

Annotation:

Rare earth elements (REEs) are a group of 15 elements in the lanthanide series along with scandium and yttrium. They are often grouped together because of their similar chemical properties. As a result of their increased application in advanced technologies and electronics including electric vehicles, the demand of REEs and other critical elements has increased in recent decades and is expected to significantly grow over the next decade. As the majority of REEs are produced and utilized within the manufacturing industry in China, concerns over future supplies to support national defense technologies and associated manufacturing industries has generated interest in the recovery of REEs from alternate sources such as coal and recycling. A solvent extraction (SX) process and circuit was developed to concentrate REEs from dilute pregnant leach solutions containing low concentrations of REEs and high concentrations of contaminant ions. The separation processes used for concentrating REEs from leachates generated by conventional sources are not directly applicable to the PLS generated from coal-based sources due to their substantially different composition. Parametric effects associated with the SX process were evaluated and optimized using a model test solution produced based on the composition of typical pregnant leach solution (PLS) generated from the leaching of pre-combustion, bituminous coal-based sources. Di-2(ethylhexyl) phosphoric acid (DEHPA) was used as the extractant to selectively transfer the REEs in the PLS from the aqueous phase to the organic phase. The tests performed on the model PLS found that reduction of Fe3+ to Fe2+ prior to introduction to the SX process provided a four-fold improvement in the rejection of iron during the first loading stage in the SX circuit. The performances on the model system confirmed that the SX process was capable of recovering and concentrating the REEs from a dilute PLS source. Subsequently, the process and optimized parametric values were tested on a continuous basis in a pilot-scale facility using PLS generated from coal coarse refuse. The continuous SX system was comprised of a train of 10 conventional mixer settlers having a volume of 10 liters each. A rare earth oxide (REO) concentrate containing 94.5% by weight REO was generated using a two- stage (rougher and cleaner) solvent extraction process followed by oxalic acid precipitation. The laboratory evaluations using the model PLS revealed issues associated with a third phase formation. Tributyl Phosphate (TBP) is commonly used as a phase modifier in the organic phase to improve the phase separation characteristics and prevent the formation of a third phase. The current study found that the addition of TBP affected the equilibrium extraction behavior of REE as well as the contaminant elements., The effect on each metal was found to be different which resulted in a significant impact on the separation efficiency achieved between individual REEs as well as for REEs and the contaminant elements. The effect of TBP was studied using concentrations of 1% and 2% by volume in the organic phase. A Fourier Transform Infrared (FTIR) analysis on the mixture of TBP and DEHPA and experimental data quantifying the change in the extraction equilibrium for each element provided insight into their interaction and an explanation for the change in the extraction behavior of each metal. The characteristic peak of P-O-C from 1033 cm-1 in pure DEHPA to 1049 cm-1 in the 5%DEHPA-1%TBP mixture which indicated that the bond P-O got shorter suggesting that the addition of TBP resulted in the breaking of the dimeric structure of the DEHPA and formation of a TBP-DEHPA associated molecule with hydrogen bonding. The experimental work leading to a novel SX circuit to treat dilute PLS sources was primarily focused on the separation of REEs from contaminant elements to produce a high purity rare earth oxide mix product. The next step in the process was the production of individual REE concentrates. To identify the conditions needed to achieve this objective, a thermodynamic model was developed for the prediction of distribution coefficients associated with each lanthanide using a cation exchange extractant. The model utilized the initial conditions of the system to estimate the lanthanide complexation and the non-idealities in both aqueous and organic phases to calculate the distribution coefficients. The non-ideality associated with the ions in the aqueous phase was estimated using the Bromley activity coefficient model, whereas the non-ideality in the organic phase was computed as the ratio of the activity coefficient of the extractant molecule and the metal extractant molecule in the organic phase which was calculated as a function of the dimeric concentration of the free extractant in the organic phase. To validate the model, distribution coefficients were predicted and experimentally determined for a lanthanum chloride solution using DEHPA as the extractant. The correlation coefficient defining the agreement of the model predictions with the experimental data was 0.996, which is validated the accuracy of the model. As such, the developed model can be used to design solvent extraction processes for the separation of individual metals without having to generate a large amount of experimental data for distribution coefficients under different conditions.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

21

Korehei, Reza. „Effect of non-solvent on viscoelastic and microstructural properties of cellulose acetate in a ternary system“. Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/32881.

Der volle Inhalt der Quelle

Annotation:

In this study, the effects of component composition on rheological and microstructural behaviour of a ternary of cellulose acetate (CA), N,N-dimethylacetamide (DMAc) and non-solvent (1-Propanol, 2-Propanol, 1-Hexanol, 1-Octanol, 1-Decanol, 1,2-Ethanediol, 1,2-Propanediol, 1,3-Propanediol, 1,4-Butanediol, 1,6-Hexanediol, Glycerol) system was examined. In this ternary system, physical gel formation can arise as a result of phase separation, which is characterized by the observation of a gradual to extreme cloudiness in the system. Depending on the non-solvent concentration, structure and polymer concentration, phase separation leads to CA aggregation and the formation of large macromolecular assemblies. Sol-gel transition is observed at a critical non-solvent concentration, which is dependent on the non-solvent structure and CA concentration. Increasing CA and non-solvent concentration resulted in enhanced steady shear viscosity and dynamic viscoelastic properties. Enhanced dynamic viscoelastic property and gelation are due to the intensification of intermolecular hydrogen bonding and hydrophobic interactions. Increasing the available hydrogen-bonding groups within the non-solvent leads to the formation of gels with larger elastic and viscous modulus (G' and G"), and a lower concentration sol-gel transition. Likewise, increasing the hydrophobic component of the non-solvent also enhanced the gel properties and accelerated the sol-gel transition. Although hydrophobic interactions play a role in the gelation process, it appears that gel properties are greatly influenced by competitive hydrogen bonding between system components. Competitive hydrogen bonding interactions between components in the various stages of the phase separation and gel formation was used to explain the weak and strong polymer-network structures observed by rheology. Through the use of Fourier transfer infrared (FTIR) spectroscopy the effect of hydrogen bonding between CA, DMAc and non-solvent were probed. Shifting the hydroxyl (OH) band to a lower wavenumber in the FTIR spectra suggests the intensification of the intermolecular hydrogen bonds in the ternary system. This shift accounts for the phase separation, and development of microstructure in the sample. Increasing the non-solvent content shifts the yield strain of the gels to a lower strain value, suggesting that they are made of floes. These floes consist of aggregated macromolecules with strong-links, and the links between floes are stronger than the links within the floes. The power-law dependence of elastic modulus (G1), together with similar values of fractal dimension for gels observed through confocal microscopy, suggests that the gels are fractal in nature and that they are made through an aggregation mechanism. Scanning electron microscopy (SEM) and laser scanning confocal microscopy (LSCM) revealed differences in the gel microstructure, depending on the constituent composition. Microscopic images showed better uniform packing in the polymer network structure as the CA concentration increases. The LSCM images (fluorescence and reflective mode) confirm the rheological results, and show different texture and aggregated structure for the gel as the structure of non-solvents are varied in the ternary system.
Forestry, Faculty of
Graduate

APA, Harvard, Vancouver, ISO und andere Zitierweisen

22

Collins, Micahel M. (Michael Matthew). „Design of a sequential in-situ anaerobic/aerobic enhanced bioremedication system for a chlorinated solvent contaminated plume“. Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/40163.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

23

Orejuela, Lourdes Magdalena. „Lignocellulose deconstruction using glyceline and a chelator-mediated Fenton system“. Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/81255.

Der volle Inhalt der Quelle

Annotation:

Non-edible plant biomass (lignocellulose) is a valuable precursor for liquid biofuels, through the processes of pretreatment and saccharification followed by fermentation into products such as ethanol or butanol. However, it is difficult to gain access to the fermentable sugars in lignocellulose, and this problem is principally associated with limited enzyme accessibility. Hence, biomass pretreatments that destroy native cell wall structure and allows enzyme access are required for effective biomass conversion techniques. This research studied two novel pretreatment methods on two wood species: 1) a deep eutectic solvent (DES) that, under heat, swells lignocellulose and partially solubilizes cell wall materials by causing breakage of lignin-carbohydrate linkages and depolymerization of the biomass components, and 2) a chelator-mediated Fenton reaction (CMF) that chemically modifies the nanostructure of the cell wall through a non-enzymatic cell wall deconstruction. After pretreatment, utilizing analytical techniques such as nuclear magnetic spectroscopy, wide angle x-ray scattering, and gel permeation chromatography, samples were analyzed for chemical and structural changes in the solubilized and residual materials. After single stage DES (choline-chloride-glycerol) and two stage, CMF followed by DES pretreatments, lignin/carbohydrate fractions were recovered, leaving a cellulose-rich fraction with reduced lignin and hemicellulose content as determined by compositional analysis. Lignin and heteropolysaccharide removal by DES was quantified and the aromatic-rich solubilized biopolymer fragments were analyzed as water insoluble high molecular weight fractions and water-ethanol soluble low molecular weight compounds. After pretreatment for the hardwood sample, enzyme digestibility reached a saccharification yield of 78% (a 13-fold increase) for the two stage (DES/CMF) pretreated biomass even with the presence of some lignin and xylan remained on the pretreated fiber; only a 9-fold increase was observed after the other sequence of CMF followed by DES treatment. Single stage CMF treatment or single stage DES pretreatment improved 5-fold glucose yield compared to the untreated sample for the hardwood sample. The enhancement of enzymatic saccharification for softwood was less than that of hardwoods with only 4-fold increase for the sequence CMF followed by DES treatment. The other sequence of treatments reached up to 2.5-fold improvement. A similar result was determined for the single stage CMF treatment while the single stage DES treatment reached only 1.4-fold increase compared to the untreated softwood. Hence, all these pretreatments presented different degrees of biopolymer removal from the cell wall and subsequent digestibility levels; synergistic effects were observed for hardwood particularly in the sequence DES followed by CMF treatment while softwoods remained relatively recalcitrant. Overall, these studies revealed insight into two novel methods to enhance lignocellulosic digestibility of biomass adding to the methodology to deconstruct cell walls for fermentable sugars.
Ph. D.
Wood is a valuable material that can be used to produce liquid biofuels. Wood main components are biopolymers cellulose, hemicellulose and lignin that form a complex structure. Nature has locked up cellulose in a protective assembly that needs to be destroyed to gain access to cellulose, convert it to glucose and then ferment it to bioalcohol. This process is principally associated with limited enzyme accessibility. Therefore, biomass pretreatments that deconstruct native cell wall structure and allow enzyme access are required for effective biomass conversion techniques. This research studied two novel pretreatment methods on two wood species: 1) a deep eutectic solvent called glyceline that, under heat, swells wood and partially solubilizes cell wall materials by causing breakage of bonds and converting it into smaller molecules (monomers and oligomers), and 2) a chelator-mediated Fenton system (CMF) that chemically modifies the structure of the cell wall. Pretreatments were tested individually and in sequence in sweetgum and southern yellow pine. After pretreatments, utilizing analytical techniques, fractions were investigated for chemical and structural changes in the solubilized and residual materials. Treated wood samples were exposed to enzymatic conversion. A maximum 78% of glucose yield was obtained for the glyceline followed by CMF pretreated wood. For yellow pine only a 24% of glucose yield was obtained for the CMF followed by glyceline treatment. All these pretreatments presented different degrees of biopolymer removal from the cell wall and subsequent enzyme conversion levels. Overall, these studies revealed insight into two novel methods to enhance wood conversion adding to the methodology to deconstruct cell walls for fermentable sugars.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

24

Kabangu, Mpinga John. „Extraction and separation of tantalum and niobium from Mozambican tantalite by solvent extraction in the ammonium bifluoride-octanol system“. Diss., University of Pretoria, 2012. http://hdl.handle.net/2263/25313.

Der volle Inhalt der Quelle

Annotation:

The principal aim of this research was to determine the optimum conditions of extraction and separation of niobium and tantalum with octanol as solvent, from Mozambican tantalite using ammonium bifluoride as an alternative to hydrofluoric acid. The extraction of niobium and tantalum from tantalite can be divided into three activities, viz., acid treatment of the ore to bring the niobium and tantalum values into solution, separation of niobium and tantalum by solvent extraction and preparation of pure niobium pentoxide and tantalum pentoxide by precipitation followed by calcination. An initial solution was prepared by melting a mixture of tantalite and ammonium bifluoride followed by leaching of the soluble component with water and separation of the solution by filtration. The solution filtered was successfully used after adjustment of the acidity for the extraction and separation of niobium and tantalum. After liquid-liquid extraction highly pure niobium pentoxide and tantalum pentoxide were obtained through precipitation with ammonium hydroxide and calcination. Comparative experiments were performed modifying the following variables: decomposition temperature; decomposition time of the digestion of niobium and tantalum; acid concentration of feed solution; solvent agent; and stripping agent. From the experimental results it was determined that the decomposition temperature, decomposition time of the digestion of niobium and tantalum, the acidity of the feed solution, the solvent agent, and stripping agent, all have an important effect on the extraction and separation of tantalum and niobium. The optimal conditions were determined to be: tantalite-to-ammonium bifluoride 1:30; decomposition temperature 250°C; decomposition time 3 hours; and a water leach period of 10 minutes. Under these conditions the leach recovery of niobium and tantalum was about 95.07% and 98.52%, respectively. For nearly complete extraction of tantalum and niobium with 2-octanol, two and three equilibrium stages, respectively, are required. The equilibrium data were obtained at an aqueous-to-organic ratio (A/O) of 1:1 using: 100% 2 octanol; 6 M H2SO4; 10 minutes contact time at room temperature for tantalum; and 100% 2 octanol, 9 M H2SO4, 10 minutes contact time at room temperature for niobium. Different stripping agents were used and water seems to give good result for both. For the nearly complete stripping process four equilibrium stages are required. From the results obtained an optimum stripping efficiency is achieved after 15 minutes for a 1:1 ratio. Niobium and tantalum were then neutralized using 28% ammonium hydroxide. The precipitate obtained was dried and placed in a muffle furnace for 4 hours at 900°C. After calcinations, pure tantalum pentoxide and niobium pentoxide were obtained and characterized using XRD and SEM. Tantalum pentoxide and niobium pentoxide synthesized contain trace impurities such as iron and titanium which can be removed by incorporating an appropriate intermediate treatment.
Dissertation (MSc)--University of Pretoria, 2012.
Chemical Engineering
unrestricted

APA, Harvard, Vancouver, ISO und andere Zitierweisen

25

Zhang, Liqin. „A new liquid-liquid partitioning system for bioseparations at low temperatures“. Ohio : Ohio University, 1997. http://www.ohiolink.edu/etd/view.cgi?ohiou1184618209.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

26

Garikipati, Satya Venkata Bhaskara Janardhan. „Biocatalysis for oxidation of naphthalene to 1-naphthol: liquid-liquid biphasic systems and solvent tolerant strains“. Diss., University of Iowa, 2009. https://ir.uiowa.edu/etd/237.

Der volle Inhalt der Quelle

Annotation:

Biocatalysis involves the use of enzymes to perform stereo- and enantio-specific reactions. One of the reactions where biocatalysis is a valuable technology is oxidation of naphthalene to 1-naphthol using Toluene ortho-Monooxygenase (TOM) variant TmoA3 V106A, also known as TOM-Green. Whole-cell biocatalysis in a water-organic solvent biphasic system was used to minimize naphthalene and 1-naphthol toxicity, and to increase substrate loading. Recombinant Escherichia coli TG1 cells expressing TOM-Green were used for biphasic biocatalysis and lauryl acetate gave best results among the solvents tested. On a constant volume basis, 8 - fold improvement in 1-naphthol production was achieved using biphasic systems compared to biotransformation in aqueous medium. The organic phase was optimized by studying the effects of organic phase ratio and naphthalene concentration in the organic phase. The efficiency of biocatalysis was further improved by application of a solvent tolerant strain Pseudomonas putida S12. P. putida S12 is solvent tolerant owing to its two adaptive mechanisms: outer membrane modification and solvent extrusion using solvent resistant pump srpABC. P. putida S12, in addition to its tolerance to various organic solvents, showed better tolerance to naphthalene compared to E. coli TG1 strain expressing TOM-Green. Application of solvent tolerant P. putida S12 further improved 1-naphthol productivity by approximately 42%. Solvent tolerance of P. putida S12 was further analyzed by transferring its tolerance to a solvent sensitive E. coli strain by transfer of solvent resistant pump srpABC genes. Engineered E. coli strain bearing srpABC genes either in low-copy number plasmid or high-copy number plasmid grew in the presence of a saturated toluene concentration. Engineered E. coli strains were also more tolerant to toxic solvents, e. g., decanol and hexane, compared to the control E. coli strain without srpABC genes. The expression of solvent resistant pump genes was confirmed by Reverse Transcriptase PCR analysis. The main drawbacks of biocatalysis for production of chemicals were addressed and approaches to minimize the drawbacks have been presented. The production of 1-naphthol was significantly improved using biocatalysis in liquid-liquid biphasic systems.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

27

Li, Guang-Shan. „Development of a reporter system for the study of gene expression for solvent production in Clostridium beijerinckii NRRL B592 and Clostridium acetobutylicum ATCC 824“. Diss., Virginia Tech, 1998. http://hdl.handle.net/10919/29439.

Der volle Inhalt der Quelle

Annotation:

Development of a reporter system for the study of gene expression for solvent production in Clostridium beijerinckii NRRL B592 and Clostridium acetobutylicum ATCC 824 By Guang-Shan Li (Abstract) To study the regulation of gene expression, a good reporter system is very useful. The lack of a good reporter system for the solvent-producing clostridia hindered the progress of research in this area. The objective of this study was to develop a reporter system to facilitate the elucidation of the control mechanism for the expression of solvent-producing genes. A potential reporter gene was found in Clostridium beijerinckii NRRL B593, which contains an adh gene encoding a primary-secondary alcohol dehydrogenase and this adh gene is not present in Clostridium acetobutylicum ATCC 824 and Clostridium beijerinckii NRRL B592. The adh gene was cloned into the E. coli -Clostridium shuttle vectors to generate plasmids. An electro-transformation procedure was developed for C. beijerinckii NRRL B592. Shuttle plasmids were transformed into C. beijerinckii NRRL B592 or C. acetobutylicum ATCC 824. The copy number of the plasmids in C. beijerinckii was 4. Isopropanol production suggested that the adh gene was expressed in transformants of C. acetobutylicum ATCC 824 and C. beijerinckii NRRL B592. Northern analysis indicated that the expression of the adh gene was regulated at the transcriptional level in the transformants of C. beijerinckii. The transcriptional start site for the adh gene was identified by the primer extension method. A promoter-probing vector was constructed and tested with the promoter from the ferredoxin(fer) gene. The expression of the adh gene under the control of the fer promoter was at a low and similar level during acidogenesis and solventogenesis. The expression pattern of the adh gene under the control of the promoter of the adh gene differed from that under the control of the promoter of the fer gene.
Ph. D.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

28

Brahma, Aischarya [Verfasser]. „Exploration of the potential of the hydroxynitrile lyase from Arabidopsis thaliana in a micro-aqueous organic solvent system / Aischarya Brahma“. Düsseldorf : Universitäts- und Landesbibliothek der Heinrich-Heine-Universität Düsseldorf, 2016. http://d-nb.info/1111774250/34.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

29

Barman, Biraj Kumar. „Investigation of diverse interactions and inclusion complexation in different environment by physicochemical methodology“. Thesis, University of North Bengal, 2018. http://ir.nbu.ac.in/handle/123456789/2622.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

30

Morgado, Daniella Lury. „Biocompósitos a partir de celulose de linter: filmes de acetatos de celulose/celulose e quitosana/celulose“. Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/75/75131/tde-25022010-152850/.

Der volle Inhalt der Quelle

Annotation:

O presente trabalho visou o estudo da modificação química da celulose de linter (obtida de fonte de rápido crescimento e considerada a celulose de maior pureza isolada de fontes vegetais) através da sua derivatização em meio homogêneo, buscando-se a obtenção de materiais com características bem definidas e via um método que apresente boa reprodutibilidade. Dentre os derivados de celulose, os acetatos têm importância industrial significativa. No presente trabalho, acetatos de celulose obtidos no sistema de solvente cloreto de lítio/dimetilacetamida (LiCl/DMAc), com diferentes graus de substituição (GS) foram caracterizados através de 1H NMR, espectroscopia na região do infravermelho, viscosimetria e análises térmicas (DSC e TG). Através de métodos quantitativos aplicados às curvas termogravimétricas pode-se obter parâmetros cinéticos relacionados à decomposição térmica como a energia de ativação (Ea). Os resultados para os acetatos mostraram que conforme o GS aumenta, aumenta o grau de substituição de C2 e C3, e observa-se também aumenta Ea. Acetatos de celulose com diferentes GS foram utilizados para a obtenção de filmes a partir do mesmo sistema de solvente. Visando à obtenção de biocompósitos, filmes de acetatos de celulose com diferentes porcentagens de celulose foram preparados. Nestes filmes, os acetatos são considerados como matriz e a celulose como reforço, se tendo como pressuposto que as cadeias de celulose formarão agregados em solução, os quais serão mantidos nos filmes, atuando então como reforço. Este pressuposto é baseado em resultados de trabalhos anteriores, assim como estudos reológicos feitos no presente trabalho, que mostram que as cadeias de celulose se agregam, mesmo a baixas concentrações. Estes materiais foram caracterizados via difração de raios X, análises térmicas (DSC, TG e DMTA), cromatografia de exclusão por tamanho (SEC), microscopia eletrônica de varredura (MEV), solvatocromismo, dentre outras. A eliminação dos solventes após a obtenção dos filmes é um fator importante a ser considerado, e os resultados mostraram que o processo escolhido não leva a presença residual dos solventes utilizados. As imagens de MEV indicaram que fibras de celulose nos filmes de biocompósitos no geral não são visíveis em escala microscópica. Este resultado é promissor, pois sugere que as fibras de celulose podem estar presentes em escala nanométrica, já que para alguns filmes a ação como reforço foi observada, através da melhora em algumas propriedades. Ainda, a rugosidade dos filmes de biocompósitos foi alterada com a presença de celulose conforme mostram os resultados de AFM. Os resultados de DMTA indicaram que uma baixa porcentagem de celulose (5% de celulose) no filme de acetato de celulose com GS 0,8, foi suficiente para a ação como reforço ser observada, sugerindo que cadeias de celulose interagiram preferencialmente entre si, gerando estruturas supramoleculares de cadeias agregadas quando ainda no meio solvente (LiCl/DMAc), as quais permaneceram na preparação dos filmes. No entanto, para o filme obtido a partir de um GS maior (GS 1,5), o efeito de reforço da celulose nos filmes de biocompósitos ocorre apenas para a maior proporção de celulose (15% de celulose). Os resultados de ensaio à tração mostraram que dependendo da aplicação, ou seja, a necessidade de filmes mais resistentes à tração e maior rigidez, estes podem ser empregados. Adicionalmente, filmes de celulose e quitosana foram preparados no sistema de solvente NaOHaq./tiouréia. Nestes filmes, considera-se a quitosana como matriz e a celulose como agente de reforço. Acredita-se que as cadeias de celulose prefiram interagir entre si, gerando \"domínios\" de cadeias de celulose. Por este motivo, o termo biocompósito foi empregado também para estes filmes. Estes materiais foram caracterizados via difração de raios X, análises térmicas (DSC, TG e DMTA), biodegradação, sorção de umidade, microscopia de força atômica (AFM), dentre outras. Os resultados de difração de raios X mostram que o sistema de solvente não altera significativamente a cristalinidade dos filmes, comparativamente aos materiais de partida. As análises térmicas empregadas (TG e DSC) mostraram que a estabilidade térmica é alterada devido a presença dos dois polissacarídeos nos filmes de biocompósitos. O estudo de biodegradação dos filmes de biocompósitos em solo simulado mostrou que a velocidade de biodegradação está relacionada à proporção das regiões não cristalinas, que são mais acessíveis à água e aos microrganismos, isto é, quanto maior o valor de índice de cristalinidade, menor será a velocidade de biodegradação. Importante ressaltar que o comportamento destes filmes em relação à biodegradação está também relacionado com a morfologia apresentada pelos filmes. A análise de AFM mostrou que o aumento da proporção de quitosana nos filmes de biocompósitos leva a maiores valores de rugosidade. Os resultados obtidos para os filmes de quitosana, celulose e biocompósitos (quitosana/celulose), assim como para os filmes de acetato de celulose, celulose e biocompósitos (acetato de celulose/celulose) se mostraram promissores.
This work was aimed at studying the chemical modification of linters cellulose extracted from a source of rapid growth and considered the most pure cellulose from vegetable sources. Derivatization was carried out in a homogeneous medium to obtain materials with well-defined properties via a reproducible method. Here cellulose acetate was obtained with various degrees of substitution (DS) using the lithium chloride/dimethylacetamide system (LiCl/DMAc), being characterized with 1H NMR, infrared spectroscopy, viscometry measurements and thermal analysis (DSC and TG). The thermogravimetric curves were analyzed quantitatively, which allowed the determination of kinetics parameters for the thermal decomposition, including the activation energy (Ea). Ea and the substitution at C2 and C3 increased with increasing DS. Cellulose acetates with distinct DS were obtained in the form of films using the solvents mentioned above. Furthermore, biocomposite films were prepared with different contents of cellulose, in which the acetates were considered as matrices and the cellulose was the loading material. It is assumed that the cellulose chains form aggregates in solution, which will be preserved in the films, thus acting as reinforcement. This hypothesis was based on previous work and confirmed here with rheological data. We show that the cellulose chains are aggregated even at low concentrations. These films were characterized using X-ray diffraction, thermal analysis (DSC, TG and DMTA), size exclusion chromatography (SEC), atomic force microscopy (AFM) and scanning electron microscopy. No residual solvent was present after film preparation. The SEM images indicated that the cellulose fibers in the biocomposite films are not visible at the microscopy scale, thus suggesting the presence of cellulose nanofibers. This is promising due to the possible enhancement in the mechanical properties, which was actually observed with a threshold percentage of only 5% of cellulose with DS 0.8. The cellulose chains apparently interacted among each other, generating supramolecular structures with aggregated chains in the LiCl/DMAc solvent. The film roughness investigated with AFM was altered by the presence of cellulose in the composite film. For the film obtained with cellulose acetate with GS 1.5, the effects from cellulose as reinforcement were only observed with higher content of cellulose (15%). According to the stress-strain tests, the films may be employed in applications requiring rigid, mechanically resistant materials. Cellulose/chitosan films were also prepared using NaOHaq./thiourea as solvent, in which chitosan served as the matrix. As in the biocomposite with cellulose acetate, the cellulose chains formed domains. The films were characterized using X-ray diffraction, thermal analysis (DSC, TG and DMTA), biodegradation tests, humidity sorption isotherms and AFM. The solvent did not affect the crystallinity of the sample, according to the XRD data. Through thermal analysis, it was inferred that the thermal stability was affected by the presence of chitosan in the biocomposite films. The study of biocomposite film degradation in a simulated soil showed that the rate of biodegradation is associated with the crystalline regions of the sample, which are more accessible to the water and the microorganisms. In other words, the higher the crystallinity the lower the biodegradation rate is. It is worth mentioning that the biodegradability also depends on the film morphology. The analysis of AFM images indicated that the film roughness increased with the content of chitosan. The results obtained with the films made with chitosan, cellulose and biocomposites (chitosan/cellulose), as well as for the films from cellulose acetate and cellulose acetate/cellulose, are promising.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

31

Werle, Stefanie Bressan. „AVALIAÇÃO DA EVAPORAÇÃO DO SOLVENTE DE SISTEMAS ADESIVOS CONTEMPORÂNEOS“. Universidade Federal de Santa Maria, 2012. http://repositorio.ufsm.br/handle/1/6096.

Der volle Inhalt der Quelle

Annotation:

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Objectives: The aim of this study was to evaluate the effect of air-drying time on degree of evaporation of solvent (DE), microtensile resin-dentin bond strength (μTBS) and degree of conversion (DC) of adhesive systems. Methods: Four two-steps etch-and-rinse (Adper Single Bond 2, XP Bond, Prime & Bond 2.1 and Opti Bond Solo) and one one-step self-etch (Adper Easy One) were tested. The DE was measured gravimetrically (n=6) after 3, 5, 10, 20, 30 and 60 seconds by air-drying. For μTBS flat dentin surfaces were obtained from fifty caries-free extracted molars (n=5). The adhesive systems were applied to dentin surfaces according to the manufacturer s instructions and subsequently air-drying for the time proposed by manufacturer (A) or for prolonged time (B), corresponding to maximum DE in the times evaluated. A composite resin was used for coronal build-up. After 24h water storage at 37ºC, the specimens were sectioned in x and y directions to obtain bonded sticks (0.9 mm2) which were immediately subjected to μTBS (1mm/min). The DC (n=3) was calculated by Fourier-transform infrared spectroscopy with attenuated total reflectance considering air-drying times A and B. The data of DE were statistically analyzed by ANOVA and Tukey´s test, μTBS and DC were analyzed by T-Test (α = 0.05). Results: The prolonged time (B) increased the DE for all materials compared to manufacturer´s times, however improved μTBS only for XP Bond and Adper Easy One. DC was not affected by evaluated air-drying times. There was no significant correlation between DC and μTBS. Conclusion: The evaporation of solvent from adhesive systems is affected by air-drying. The effect of air-drying time seems be material-dependent on parameters evaluated. Changes in protocols of use may be necessary to obtain better properties.
Objetivos: Avaliar o efeito de diferentes protocolos de aplicação de jato de ar no grau de evaporação do solvente (GE), resistência de união à dentina (RU) e grau de conversão (GC) de sistemas adesivos. Métodos: Quatro sistemas adesivos de dois passos com condicionamento ácido prévio (Adper Single Bond 2, XP Bond, Prime & Bond 2.1 e Opti Bond Solo) e um autocondicionante de passo único (Adper Easy One) foram testados. O GE foi mensurado gravimetricamente (n=6) após a aplicação de jato de ar durante 3, 5, 10, 20, 30 e 60 segundos. A RU à dentina foi mensurada através do teste de microtração. Para isso, cinquenta molares humanos hígidos (n=5) tiveram o esmalte e dentina superficial removidos. Os sistemas adesivos foram aplicados de acordo com as instruções dos fabricantes na superfície dentinária e subsequentemente foi aplicado jato de ar durante o tempo proposto pelo fabricante (A) ou por tempo prolongado (B), o qual resultou em evaporação máxima nos tempos considerados na avaliação do GE. Após a confecção de blocos de resina composta e armazenamento em água à 37ºC, por 24 horas, os espécimes foram seccionados em dois eixos a fim de obterem-se espécimes com área de secção transversal de aproximadamente 0,9 mm2. Os espécimes foram submetidos ao teste de microtração com velocidade de 1mm/min. O GC (n=3) foi analisado por espectroscopia de infravermelho transformada de Fourier (FTIR) considerando os tempos A e B. Os dados do GE foram submetidos à análise de variância de um fator e teste de Tukey. Os dados de RU e GC foram submetidos ao teste t de Student pareado. Todas as análises foram realizadas considerando o nível de significância de 5%. Resultados: A aplicação de jato de ar por tempo prolongado (B) aumentou o GE para todos os materiais em comparação ao tempo proposto pelo fabricante. Contudo, maiores valores de RU foram obtidos somente para os sistemas XP Bond e Adper Easy One. O GC não foi afetado pelos tempos de aplicação de jato de ar avaliados. Não houve correlação significante entre GC e RU. Conclusão: A evaporação do solvente dos sistemas adesivos testados é modulada pelo tempo de aplicação de jato de ar. A influência do tempo de aplicação do jato de ar nos parâmetros testados parece ser material dependente. Mudanças no protocolo de aplicação jato de ar podem ser necessárias a fim de se obterem as melhores propriedades dos sistemas adesivos.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

32

Onwukamike, Kelechukwu Nnabuike [Verfasser], M. A. R. [Akademischer Betreuer] Meier und H. [Akademischer Betreuer] Cramail. „Sustainable Cellulose Solubilization, Regeneration and Derivatization in a DBU-CO$_2}$ Switchable Solvent System / Kelechukwu Nnabuike Onwukamike ; Betreuer: M.A.R. Meier, H. Cramail“. Karlsruhe : KIT-Bibliothek, 2019. http://d-nb.info/1181190525/34.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

33

Husson, Éric. „Synthèse de dérivés fonctionnels de petits peptides par voie enzymatique“. Thesis, Vandoeuvre-les-Nancy, INPL, 2008. http://www.theses.fr/2008INPL061N/document.

Der volle Inhalt der Quelle

Annotation:

Ce travail a consisté à étudier la N et/ou O acylation enzymatique d’alcool aminés et de dipeptides.Une étude préliminaire consacrée à l’acylation enzymatique d’une molécule modèle, le 6-amino-1-hexanol a démontré la capacité de la lipase B de Candida antarctica immobilisée à catalyser l’acylation de ce substrat dans différents milieux réactionnels. La mise en œuvre de cette réaction en solvants organiques (hexane, 2-méthyl-2-butanol) a conduit à la formation du produit diacylé avec un rendement de 85 % montrant l’absence de chimio-sélectivité de la réaction. L’utilisation de système sans solvant à base d’acide gras libre et de CO2 supercritique a permis d’orienter la chimio-sélectivité de la réaction en faveur de la O-acylation. Les liquides ioniques à cation de type imidazolium et à anions faiblement nucléophiles ont conduit à un taux de conversion de l’alcool aminé de l’ordre de 99 % tout en conservant l’absence de chimio-sélectivité observée en solvant organique. L’étude s’est ensuite focalisée sur l’acylation de dipeptides modèles tels que la Lys-Ser,HCl et la Ser-Leu. L’étude de l’acylation catalysée par la lipase B de Candida antarctica immobilisée de la Lys-Ser,HCl a montré une sélectivité exclusive en faveur de l’acylation de la fonction amine en position e, indépendamment du milieu réactionnel. La O-acylation de la Ser-Leu a permis de mettre en évidence l’influence du groupe carboxylique Cterminal électro-attracteur de Lys-Ser sur la réactivité de la fonction hydroxyle de la sérine. Enfin, la N-acylation enzymatique d’un dipeptide naturel bioactif, la carnosine a été réalisée d’une part en solvant organique, catalysée par la lipase B de Candida antarctica immobilisée et d’autre part, en milieu aqueux biphasique catalysée par l’acyl-transférase de Candida parapsilosis. L’acylation de la carnosine, conduisant à la synthèse de N-oléyl carnosine, n’affecte pas son activité inhibitrice de la xanthine oxydase et semble améliorer son activité anti-radicalaire vis-à-vis de l’anion superoxyde
The present work consisted in studying the N and/or O-enzymatic acylation of amino alcohols and dipeptides. A preliminary study was firstly undertaken about the enzymatic acylation of a bifunctionnal model molecule, 6-amino-1-hexanol and demonstrated the ability of the lipase B of Candida antarctica to catalyze the acylation of this substrate in different reaction media. The reaction performed in organic solvents (hexane, 2-methyl-2-butanol) allowed to the synthesis of the diacylated product with a substrate conversion yield of 85 %, showing the absence of chimio-selectivity of the reaction. The use of a solvent-free system constituted of free fatty acid and the use of supercritical carbon dioxide permitted to orientate the selectivity of the reaction in favour of the O-acylation. Ionic liquids with imidazolium cation and few nucleophilic anions led to a substrate conversion of 99 % and to maintain the absence of chemo-selectivity observed in organic solvents. Then, the study focused on the acylation of model dipeptides like Lys-Ser, HCl and Ser-Leu. Results relative to the acylation of Lys-Ser, HCl catalyzed by the lipase B of Candida antarctica immobilized showed a selectivity in favour of the acylation of the e-amino function independently of the reaction medium. The Ser-Leu O-acylation permitted to demonstrate the influence of the molecular environment (electro-attractor C terminal carboxylic group) on the reactivity of the serine hydroxyl function. Finally, the enzymatic acylation of a bioactive dipeptide was catalyzed by the lipase B of Candida antarctica immobilized in organic solvent and by the acyl-transferase of Candida parapsilosis in lipid-aqueous biphasic medium. The acylation of carnosine allowed the N-oleyl carnosine synthesis. The acylation of carnosine did not affect its xanthine oxydase inhibition activity and seemed to improve its superoxyde anion scavenging property

APA, Harvard, Vancouver, ISO und andere Zitierweisen

34

Oliveira, Samantha Sant'Anna Marotta de. „Preparação e caracterização in vitro de micropartículas de heparina fracionada potencialmente aplicáveis ao tratamento da trombose venosa profunda“. Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/60/60137/tde-30042009-143701/.

Der volle Inhalt der Quelle

Annotation:

A trombose venosa profunda (TVP) é uma patologia grave de alta incidência mundial. Quando não diagnosticada precocemente e tratada adequadamente pode evoluir causando sérias complicações, como a embolia pulmonar e insuficiência venosa crônica, as quais são responsáveis por altas taxas de morbidade e mortalidade. Seu tratamento utiliza terapia com anticoagulantes pelas vias parenteral e oral (para manutenção) que estão associadas a prejuízos bem documentados limitando seu uso, além de resultar em baixa adesão do paciente ao tratamento. Os sistemas de liberação modificada de fármacos, tais como as micropartículas poliméricas, representam uma grande área em desenvolvimento, a qual tem recebido atenção de pesquisadores e indústrias de todo o mundo e recebido investimentos crescentes nas últimas três décadas. As micropartículas poliméricas possuem grande estabilidade, capacidade industrial e possibilitam ajustes para alcançar o perfil de liberação adequado e/ou o direcionamento para determinado sítio de ação. O estudo teve início com o desenvolvimento e validação do método analítico para a quantificação da enoxaparina sódica. A turbidimetria foi a técnica de escolha, pois os resultados utilizando CLAE não foram satisfatórios. Este estudo teve como objetivo a obtenção e caracterização físico-química de um sistema de liberação microparticulado para veiculação de uma heparina fracionada (HF), a enoxaparina sódica, muito utilizada no tratamento da TVP, visando um aumento da biodisponibilidade do fármaco com controle da sua biodistribuição. As micropartículas contendo a enoxaparina sódica foram preparadas utilizando o copolímero dos ácidos lático e glicólico (50:50) (PLGA), biodegradável, através do método da dupla emulsificação/ evaporação do solvente. As partículas obtidas foram caracterizadas pela técnica de microscopia eletrônica de varredura (MEV) e apresentaram forma esférica com superfície lisa e regular. As análises do tamanho e distribuição dos tamanhos de partícula foram realizadas por dispersão de luz laser e apresentaram perfil monomodal para a maioria das formulações. O perfil de liberação in vitro do fármaco encapsulado foi avaliado por 35 dias e apresentou cinética de liberação de pseudo ordem zero, modelo de Higuchi (1961), indicando que a difusão foi o principal mecanismo de liberação. A velocidade de degradação das micropartículas é, através da difusão do fármaco, um parâmetro muito importante e determinante da liberação in vivo.
Deep vein thrombosis (DVT) is a severe disease with high incidence worldwide. When it is not early diagnosed and properly treated it can develop and to cause serious complications, such as pulmonary embolism and chronic venous insufficiency, which are responsible for high morbidity and mortality rates. The treatment of DVT is accomplished with parenteral and oral (for maintenance) anticoagulants. They are associated to damage well documented that limit their use resulting in poor adherence of patients to treatment. Drug delivery systems, such as polymeric microparticles, represent a significant development area. It has received attention of researchers and industries around the world and increased investments in last three decades. The polymeric microparticles have great stability, industrial capacity and they allow adjustments to achieve the suitable release profile and / or direction for a particular site of action. The study started with development and validation from the analytical method to quantification of enoxaparin sodium. Turbidimetric technique was used because the results by HPLC were not satisfactory. The aim of this work was the preparation and physical-chemical characterization of a microparticle release system for delivery of a fractionated heparin (FH), enoxaparin sodium, widely used to the treatment of DVT to increase the drug bioavailability and control their biodistribution. The microparticles containing enoxaparin sodium were prepared from a biodegradable polymer poly (lactic-co-glycolic acid) (50:50) (PLGA) using double emulsification / evaporation of the solvent method. The particles obtained were characterized by scanning electron microscopy technique (SEM) and showed spherical shape with smooth and regular surface. The analysis of the size and distribution of particle sizes were performed by scattering of laser light and showed unimodal profile for the most of formulations. In vitro drug release profile from the microparticles was evaluated in 35 days showing pseudo zero order kinetics, Higuchi model (1961). This indicated that main mechanism of drug release was diffusion.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

35

Makaka, Siphokazi. „The development of an empirical mass transfer relationship for the extraction of copper ions in a carrier facilitated tubular supported liquid membrane system“. Thesis, Cape Peninsula University of Technology, 2011. http://hdl.handle.net/20.500.11838/866.

Der volle Inhalt der Quelle

Annotation:

Thesis submitted in fulfilment of the requirements for the degree Master of Technology: Chemical Engineering in the Faculty of Engineering at the Cape Peninsula University of Technology 2011
Treatment of waste material from mining and mineral processing is gaining increasing importance as a result of the increasing demand for high purity products and environmental concerns. Supported liquid membranes (SLMs) have been proposed as a new technology for the selective removal of metal ions from a solution. This technology can be described as the simultaneous extraction and stripping operation, combined in a continuous single process unit. Theoretically, the rate of mass transfer through SLM systems could be controlled by three resistances, namely: · Resistance through the feed-side · Resistance through the strip-side laminar layers; and · Diffusion through the membrane. It has been reported that transport resistance in the feed-side laminar layer is controlling. (Srisurichan et al, 2005:186). The objective of this research was to extract copper ions in a TSLM system, evaluate the effect of the feed characteristics on the feed-side laminar layer and determine a relationship between the applicable dimensionless numbers, i.e. Sherwood, Schmidt and Reynolds numbers. A Counter-current, double pipe Perspex bench-scale reactor, consisting of a single hydrophobic PVDF tubular membrane mounted vertically within, was used for the test work. The membrane was impregnated with LIX 984N-C and became the support for this organic transport medium. Dilute Copper solution passed through the centre pipe and sulphuric acid, as a strippant, passed through the shell side. In this test work, Copper was successfully transported from the feed-side to the strip-side and through repetitive results; a relationship between dimensionless numbers was achieved.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

36

Ballentine, Michael Drake. „Imidazolium Ionic Liquids as Multifunctional Solvents, Ligands, and Reducing Agents for Noble Metal Deposition onto Well-Defined Heterostructures and the Effect of Synthetic History on Catalytic Performance“. TopSCHOLAR®, 2018. https://digitalcommons.wku.edu/theses/2101.

Der volle Inhalt der Quelle

Annotation:

1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM]Tf2N) was investigated as a multifunctional solvent, ligand, and reducing agent for platinum deposition onto well-defined CdSe@CdS nanorods. Platinum deposition was carried out thermally and photochemically using Pt(acac)2 as the metal precursor. Thermal deposition was investigated in [BMIM]Tf2N with and without addition of a sacrificial reducing agent, and product topology was compared with the products obtained from polyol reduction using 1,2-hexadecanediol, oleic acid, and oleylamine in diphenyl ether. Photochemically induced platinum deposition was carried out at room temperature in [BMIM]Tf2N, and product topology was compared with the photodeposition products obtained from a toluene dispersion. Thermal deposition of platinum in ionic liquid showed rods of broken morphology and small platinum nanoparticles speckled across the rods’ surface, while photodeposition of platinum exhibited particles decorated throughout the nanorod surface but larger in size than those exhibited by thermal means. Photocatalytic reduction of methylene blue was studied using these Pt-CdSe@CdS heterostructured nanoparticles, and catalytic performance was correlated with topology and synthetic history. Initial findings of catalytic performance suggest that there in an advantage of depositing platinum nanoparticles onto the CdSe@CdS in the ionic liquid system. Methylene blue dye was degraded using each system and the results show and there is an increased performance of the nanorods synthesized in the ionic system.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

37

Dakua, Vikas Kumar. „Physico-chemical studies on interactions between ion-solvent, ion-ion and solvent-solvent in aqueous and non-aqueous pure and mixed solvent systems“. Thesis, University of North Bengal, 2008. http://hdl.handle.net/123456789/707.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

38

Henneman, Richard Lewis. „Human problem solving in complex hierarchical large scale systems“. Diss., Georgia Institute of Technology, 1985. http://hdl.handle.net/1853/25432.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

39

Smith, Jill Yvonne. „Communication Quality in Information Systems Development: The Effect of Computer-Mediated Communication on Task-Oriented Problem Solving“. Thesis, North Texas State University, 1986. https://digital.library.unt.edu/ark:/67531/metadc331600/.

Der volle Inhalt der Quelle

Annotation:

The problem motivating this research is that ineffective communication may hamper systems development efforts. Specifically germane to this study are development efforts characterized as task-oriented, and which require information-sharing and problem-solving activities. This research problem motivated an analysis of the communication process and lead to the development of a temporal framework that delineates variables associated with task-oriented, end user/systems analyst communication interactions. Several variables within this framework are depicted in two theoretical models. The first model shows the theoretical relationship between an independent variable, communication mode (represented by asynchronous computer conferencing and face-to-face conferencing), and five dependent variables: (1) the amount of information shared, (2) the significance of the information shared, (3) the comprehensiveness of the information shared, (4) the perception of progress toward the goal, and (5) the perception of freedom to participate. The second model depicts the assumed interaction between communication mode, the five variables cited above (now acting as independent variables), and a dependent variable, communication quality. There are two theoretical components of communication quality: (1) deviation from an optimal set of user requirements, and (2) the degree of convergence (unity based on mutual understanding and mutual agreement) emanating from a communication interaction. Using the theoretical models as a guide, an experiment was designed and performed to test the relationships among the variables. The experimental results led to the rejection of all null hypotheses; the results strongly favored face-to-face conferencing for solving task-oriented, information-sharing problems analagous to the case used in the present study. The findings indicate that asynchronous computer conferencing may have a detrimental effect on the thoroughness of information exchange, on the relevance of the information shared in terms of making the correct decision, and on the completeness of the consideration given to all problem dimensions.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

40

Khalid, Muhammad. „Influence of solvent viscosity, polarity and polarizability on the chemiluminescence parameters of inter and intramolecular electron transfer initiated chemiexcitation systems“. Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/46/46136/tde-29092015-114251/.

Der volle Inhalt der Quelle

Annotation:

The cyclic peroxides: diphenoyl peroxide (1), spiro-adamantyl-1,2-dioxetanone (2) and 4-(3-tert-butyldimethylsilyloxyphenyl)-4-methoxyspiro[1.2-dioxetane-3.2\'-adamantane] (3) synthesized, purified and characterized, also their kinetic and chemiluminescence (CL) properties were determined. The influence of solvent polarity on the chemiexcitation parameters of the catalyzed decomposition of 1 and 2, as well as the induced decomposition of 3 were examined in several binary solvent mixtures with different polarity and polarizability parameters, but similar viscosities. For solvents with low polarity, singlet quantum yields for the intermolecular catalyzed decomposition of diphenoyl peroxide (1,) and 1,2-dioxetanone (2) increase in function of medium polarity, showing maximum values in mediums of intermediate polarity, and decreasing in highly polar mixtures. For the induced decomposition of 3, the quantum yield showed to increase with increasing solvent polarity, including high polar solvent systems. In the binary solvent systems studied, the polarizability parameter showed to be contrary to the polarity values, therefore, it might appear that an increase of polarizability leads to a decrease in the singlet quantum yields for catalyzed decomposition of diphenoyl peroxide (1) and the induced decomposition of 3, however an increase in the singlet quantum yields for 1,2-dioxetanone 2. The three CL systems were also studied in binary solvent mixtures with different viscosities but similar polarity and polarizability parameters and singlet quantum yields showed an increase with increasing medium viscosity. Data were analyzed by using the collisional and the free volume models. The highly efficient intramolecular system induced 1,2-dioxetane 3 decomposition showed to be much more sensible to viscosity effects than the inefficient intermolecular systems. This surprising fact indicates that, even showing a significant solvent-cage effect, the induced 1,2-dioxetane should occur by an intramolecular electron back transfer. Moreover, chemiluminescence parameters of these systems were studied in several pure solvents. The obtained singlet quantum yields were correlated with viscosity, polarizability and polarity parameters by using multiple linear regression analysis.
Os peróxidos cíclicos: peróxido de difenoila (1), spiro-adamantil-1,2-dioxetanona (2) e 4-(3-terc-butildimetilsililoxifenil)-4-metoxispiro[1,2-dioxetano-3.2\'-adamantano] (3) foram sintetizados, purificados e caracterizados e as suas propriedades cinéticas e de quimiluminescência (CL) determinadas. A influência da polaridade do solvente sobre os parâmetros de quimi-excitação da decomposição catalisada de 1 e 2, e a decomposição induzida de 3 foi examinada em diversas misturas binárias de solventes com parâmetros de polaridade e polarizabilidade diferente, mas viscosidades semelhantes. Para solventes com baixa polaridade, os rendimentos quânticos singlete para a decomposição catalisada intermolecular do peróxido de difenoila (1) e 1,2-dioxetanona (2) aumentam em função da polaridade do meio, mostrando valores máximos em meios com polaridade intermediária, e diminuim para misturas altamente polares. Para a decomposição induzida de 3, o rendimento quântico mostrou aumentar com o aumento da polaridade do solvente, inclusive para sistemas com alta polaridade. Nos sistemas binários de solventes estudados, os parâmetros de polarizabilidade mostraram-se contrários aos valores de polaridade, portanto, parece que um aumento da polarizability leva a uma diminuição nos rendimentos quânticos singlete para a decomposição catalisada do peróxido de difenoila (1) e a decomposição induzida de 3, no entanto, um aumento nos rendimentos quânticos singlete para a 1,2-dioxetanona 2. Os três sistemas de CL também foram estudados em misturas binárias de solventes com diferentes viscosidades, mas com parâmetros de polaridade e polarizabilidade semelhantes e os rendimentos quânticos singlete mostraram aumentar com o aumento da viscosidade do meio. Os dados foram analisados usando tanto o modelos colisional quando o modelo de volume livre. Surpreendentemente, o sistema altamente eficiente decomposição induzida intramolecular do 1,2-dioxetano 3 mostrou-se muito mais sensível aos efeitos da viscosidade do que os sistemas intermoleculares ineficientes, o que indica claramente que a decomposição induzida do 1,2-dioxetano deve ocorrer por um processo de retro-transferência de elétron intramolecular. Além disso, os parâmetros de quimiluminescência destes sistemas foram estudados em vários solventes puros. Os rendimentos quânticos singlete obtidos foram correlacionados com parâmetros de viscosidade, polarizabilidade e polaridade usando análise de regressão linear múltipla.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

41

Brindle, David. „Lattice models of amphiphile and solvent mixtures“. Thesis, Sheffield Hallam University, 1991. http://shura.shu.ac.uk/19397/.

Der volle Inhalt der Quelle

Annotation:

Materials based on amphiphilic molecules have a wide range of industrial applications and are of fundamental importance in the structure of many biological systems. Their importance derives from their behaviour as surface-active agents in solubilization applications and because of their ability to form systems with varying degrees of structural order such as micelles, bilayers and liquid crystal phases. The nature of the molecular ordering is of importance both during the processing of these materials and in their final application. A Monte Carlo simulation of a three dimensional lattice model of an amphiphile and solvent mixture has been developed as an extension of earlier work in two dimensions. In the earlier investigation the simulation was carried out with three segment amphiphiles on a two dimensional lattice and cluster size distributions were determined for a range of temperatures, amphiphile concentrations and intermolecular interaction energies. In the current work, a wider range of structures are observed including micelles, bilayers and a vesicle. The structures are studied as a function of temperature, chain length, amphiphile concentration and intermolecular interaction energies. Clusters are characterised according to their shape, size and surface roughness. A detailed temperature-concentration phase diagram is presented for a system with four segment amphiphiles. The phase diagram shows a critical micelle concentration (c.m.c) at low amphiphile concentrations and a transition from a bicontinuous to lamellar region at amphiphile concentrations around 50%. At high amphiphile concentrations, there is some evidence for the formation of a gel. The results obtained question the validity of current models of the c.m.c. The Monte Carlo simulations require extensive computing power and the simulation was carried out on a transputer array, where the parallel architecture allows high speed. The development of a suitable parallel algorithm is discussed. A mean field model of a bilayer is presented which has similar interaction potentials as the Monte Carlo model. The ordering of the bilayer is examined as a function of chain length, bilayer thickness, temperature and inter molecular interaction energies. In this approximation a phase transition to the ordered bilayer is observed.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

42

Cheng, Chin-Hwa 1957. „Solubility of diuron in complex solvent systems“. Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/277194.

Der volle Inhalt der Quelle

Annotation:

The solubility of diuron was determined in binary and ternary cosolvent-water systems. The binary systems were composed of a completely miscible organic solvent (CMOS) and water while the ternary systems incorporate partially miscible organic solvents (PMOS) into the binary systems. Due to the low aqueous solubilities of trichloroethylene and toluene, the PMOS's do not behave as cosolvents and they do not play an important role in altering solubility.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

43

Lunkov, Sergey. „Modelling metal complexation in solvent extraction systems“. Thesis, Curtin University, 2013. http://hdl.handle.net/20.500.11937/2018.

Der volle Inhalt der Quelle

Annotation:

This thesis represents a theoretical investigation of synergistic solvent extraction of transition metal ions based on models for the commercial used components, namely LIX63 and Versatic10 acid. Quantum mechanical studies of oxime isomerisation have been conducted in order to understand the thermodynamic and kinetic properties of the syn/anti interconversion of LIX63, which is found to favour an oligomeric form in non-polar solvents.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

44

Pinheiro, Carolina Tavares. „Characterization of lubricant oils and regeneration studies by green solvent extraction“. Doctoral thesis, 2018. http://hdl.handle.net/10316/80616.

Der volle Inhalt der Quelle

Annotation:

Tese de doutoramento em Engenharia Química, apresentada ao Departamento de Engenharia Química da Faculdade de Ciências e Tecnologia da Universidade de Coimbra
Waste lubricant oil (WLO) is the most significant liquid hazardous waste stream in Europe that requires proper handling and treatment. Regeneration is an interesting treatment route to mitigate the significant environmental impacts of lubricants. Solvent extraction is one of the most effective deasphalting processes for the regeneration of WLO. The current objectives towards a circular economy represent a challenge to continuously maximize the regeneration of this waste. The quality of WLO is a limiting factor regarding its potential for regeneration, in which producers have a great responsibility on the handling phase. In addition, with increasing awareness for environmental protection, it is becoming imperative to find not only sustainable but also economically attractive processes. In this context, the main objectives of the thesis include the characterization of fresh and waste lubricant oils aiming to improve the management system of WLO in Portugal. In addition, the objectives of this work include studies of the regeneration process by solvent extraction, the development of a new methodology for the selection of sustainable solvents and the assessment of the best extraction conditions. Regarding the characterization of fresh lubricant oil, the following properties were evaluated: viscosity; viscosity index; density; total acid number (TAN); saponification number; and percentage of aromatics, naphthenics and paraffinics. Regression models that can predict the desired properties based on FTIR spectra were developed. The density, percentage of aromatics, naphthenics and paraffinics were well predicted. As regards the characterization of WLO, the temperature dependence of viscosity was investigated, and correlations for the estimation of viscosity and surface tension from density were assessed. The temperature dependence of viscosity at the Newtonian plateau of WLO deviated from the Arrhenius behavior, and was accurately described by four correlations: Williams–Landel–Ferry (WLF), MYEGA, power law and Ghatee. The glass transition temperature varied between 170.5 and 198.7 K. New correlations were found for the estimation of viscosity and surface tension from density at different temperatures. The evaluation and improvement of a national management system was based on the physicochemical characteristics of WLO collected from different producers (garage, industry and others). The results revealed that chlorine nonconformities (Cl > 2000 ppm) were mostly registered in industrial producers. Therefore, the management system could be improved by segregating oils from industry. In addition, FTIR analysis showed that about 60% of the WLO collected in Portugal may be contaminated with glycol-containing compounds (e.g. brake fluid and antifreeze), regardless the producer. The nature of the compounds responsible for the coagulation phenomena after alkaline treatments that may cause plant shutdown was studied. For that, an empirical test method was developed to assess the coagulation behavior of WLO. The coagulation phenomena were classified as A – negative, B – precipitate formation and C – positive. Spectral discriminating analysis revealed that class A oils did not have any compounds that negatively affect the alkaline treatment. Class B oils may be constituted by gear or hydraulic lubricants, which have low concentration of additives and oxidation products. Class C is mainly composed by synthetic esters, which form a gel-type oil after the addition of KOH and hamper regeneration processes in alkaline treatments. The classification based on statistical analysis applied to FTIR spectra properly categorize 83% of the WLO according to their coagulation class. A new methodology for the selection of solvents for WLO regeneration, which takes into account technical, economical and greenness issues was proposed. In the first phase, five criteria were used: water and acidic properties; selectivity towards the base oil and flocculation capacity; number of carbon atoms between three and five; melting point lower than 10 ºC and a boiling point between 60 and 130 ºC; yield greater than 85%. In the second phase, three metrics of sustainability were employed: greenness, efficiency, and cost. Globally, a score was attributed to each solvent based on the assessment of individual metrics. From a list of 154 solvents, 1-butanol, isobutanol, and methylethyl ketone (MEK) are the most sustainable solvents. Solvent extraction studies were performed using 1-butanol and MEK as “green” solvents. WLO with substantial different properties and segregated by coagulation classes (A, B and C) were tested. The extraction is not effective for class B oil, due to its low level of impurities. The addition of KOH in class C oils is less effective due to greater saponifiable matter in the oil. 1-Butanol is more efficient than MEK for both class A and C. The optimal solvent/oil ratio of 5 w/w and KOH dosage of 1.5 or 2 g/L was found for all systems.
Os óleos lubrificantes usados (OU) constituem o resíduo líquido perigoso mais significativo da Europa. A sua regeneração constitui uma interessante via de tratamento para mitigar o elevado impacto ambiental e está alinhada com os princípios da “economia circular”, um desiderato nacional e europeu. De facto, sendo os OU um resíduo perigoso, a sua recuperação e reintrodução no ciclo de vida útil, é de relevância acrescida. Contudo, a qualidade dos OU é um fator limitante para o seu potencial de regeneração, no qual os produtores têm uma responsabilidade central. Além disso, para além da vertente ambiental, torna-se imperativo implementar abordagens holísticas que garantam o desenvolvimento de um ciclo de vida dos OU mais sustentável. Neste contexto, os principais objetivos da tese envolvem a caraterização de óleos novos e usados com vista à melhoraria do sistema de gestão de OU em Portugal. Além disso, os objetivos deste trabalho incluem estudos do processo de regeneração por extração solvente, incluindo o desenvolvimento de uma nova metodologia para a seleção de solventes e a avaliação das condições ótimas de extração. Relativamente à caraterização de óleos lubrificantes novos, foram avaliadas as seguintes propriedades: viscosidade; índice de viscosidade, densidade, índice de acidez; índice de saponificação e teor de parafínicos, nafténicos e aromáticos. Desenvolveram-se modelos de regressão para a previsão destas propriedades com base nos espetros FTIR. A densidade, percentagem de aromáticos, nafténicos e parafínicos foram corretamente previstas. Em relação à caracterização de OU, investigou-se a dependência da temperatura com a viscosidade, e avaliaram-se correlações para estimar a viscosidade e tensão superficial a partir da densidade. A dependência da viscosidade com a temperatura dos OU desvia-se do comportamento de Arrhenius, sendo descrita com precisão por quatro correlações: Williams-Landel-Ferry (WLF), MYEGA, lei de potência e Ghatee. A temperatura de transição vítrea variou entre 170,5 e 198,7 K. Adicionalmente, foram desenvolvidas novas correlações para estimar a viscosidade e a tensão superficial a partir da densidade a diferentes temperaturas. O potencial de melhoria do sistema nacional de gestão foi avaliado tendo em conta as características físico-químicas de OU recolhidos em diferentes produtores (oficinas, indústria e outros). Os resultados revelaram que as não conformidades de cloro (Cl> 2000 ppm) registam-se sobretudo em produtores industriais. Desta forma, o sistema de gestão poderia beneficiar da segregação dos óleos industriais. Além disso, a análise FTIR mostrou que 60% dos OU recolhidos em Portugal podem estar contaminados com glicol (e.g. fluido de travão e anticongelante), independentemente do tipo de produtor. Foi estudada a natureza dos compostos responsáveis pelos fenómenos de coagulação após tratamento alcalino que podem causar problemas no processo industrial. Paral tal, de modo a avaliar o comportamento de coagulação dos OU foi desenvolvido em teste empírico. Os resultados foram classificados como A - negativos, B - formação de precipitados e C - positivos. A análise espectral discriminante revelou que os óleos classe A não possuem compostos que afetam negativamente o tratamento alcalino. Os óleos da classe B podem ser constituídos por óleos de engrenagem ou hidráulicos, que por terem baixa concentração de aditivos e produtos de oxidação, não reagem com o KOH, que acaba por precipitar. A classe C é composta por óleos sintéticos do tipo éster, que formam um gel após a adição de KOH e inibem a regeneração com tratamento alcalino. A classificação do teste de coagulação baseada na análise estatística aplicada ao FTIR categoriza corretamente 83% dos OU de acordo com sua classe de coagulação. Propôs-se uma nova metodologia para a seleção de solventes para regeneração de OU, que contrabalança critérios técnicos, económicos e de “verdura”. Na primeira fase, cinco critérios foram utilizados: água e propriedades ácidas; seletividade para com o óleo base e capacidade de floculação; número de átomos de carbono entre três e cinco; ponto de fusão < 10 ºC e ponto de ebulição entre 60 e 130 ºC; rendimento > 85%. Na segunda fase, três métricas de sustentabilidade foram aplicadas: “verdura”, eficiência e custo. Globalmente, foi atribuída uma pontuação a cada solvente com base na avaliação das métricas individuais. De uma lista de 154 solventes, o 1-butanol, isobutanol e metiletilcetona (MEK) foram os mais sustentáveis. Os estudos de extração realizados com 1-butanol e MEK (solventes “verdes”) mostraram ser eficientes para recuperar os OU. Neste âmbito, foram testados OU com propriedades substancialmente diferentes e segregados por classe de coagulação (A, B e C). A extração não é efetiva para o óleo classe B, devido ao baixo nível de impurezas. A adição de KOH nos óleos da classe C é menos eficaz devido à maior quantidade de matéria saponificável no óleo. O 1-butanol é mais eficiente que o MEK para as classes A e C. A razão solvente/óleo ótima corresponde a 5 w/w e a dosagem de KOH a 1,5 ou 2 g/L.
SOGILUB – Sociedade de Gestão Integrada de Óleos Lubrificantes Usados, Lda

APA, Harvard, Vancouver, ISO und andere Zitierweisen

45

Lai, Su-Huei, und 賴素慧. „A study on the phase separation behavior of the DLPLA-Solvent-Non-Solvent System“. Thesis, 2005. http://ndltd.ncl.edu.tw/handle/10950040576437582076.

Der volle Inhalt der Quelle

Annotation:

碩士
國立陽明大學
醫學工程研究所
93
Due to its superior properties of biocompatibility and biodegradability, polylactide has been widely used in the preparations of cellular scaffolds, drug carriers, and polymer film. Literature reviews indicate that porous structure of polylactide mainly caused by the liquid-liquid demixing of the solidification process. This study constructs the phase diagrams of DL-PLA-Solvent-Non-solvent ternary systems to explore the behavior of phase separation by tuning temperature, solvent and nonsolvent. Theoretical liquid-liquid demixing gap based on model proposed by Yilmaz are also included. Our experimental results show that when temperature decreases, liquid-liquid demixing gap moves toward polymer-solvent axis; when we change solvent, the increase in the miscibility between polymer and solvent will decrease the area of liquid-liquid demixing gap. This effect becomes even more noticeable with better mutual affinities between solvent and nonsolvent. By changing nonsolvent, if the miscibility between solvent and nonsolvent increases, liquid-liquid demixing gap becomes larger. This effect becomes more prominent when polymer and nonsolvent are barely miscible. Theoretical analyses, in which interaction parameters are evaluated by our solubility tests, reveal that when g12 ＜ g13 ， liquid-liquid demixing gap becomes larger with decrement of g12 , and increment of g23 and g13 . The experimental observations in liquid-liquid demixing have the same trends with the results of theoretical prediction; however, the exact values of binodal curves are different. The differences between the experimental and theoretical binodal curves might be caused by the error of the interaction parameters applied and by the neglect of the concentration dependency of g13 . Key word: Interaction parameters; Flory-Huggins; phase diagram

APA, Harvard, Vancouver, ISO und andere Zitierweisen

46

Li, Kang-Fang, und 李耿芳. „Development of the solvent based slurry stereolithography rapid prototyping system“. Thesis, 2010. http://ndltd.ncl.edu.tw/handle/n9z2yq.

Der volle Inhalt der Quelle

Annotation:

碩士
國立臺北科技大學
機電整合研究所
98
The purpose of the study is to develop a Solvent based Slurry Stereolithography (3S) Rapid Prototyping System. This system is applying dynamic mask to form a ceramic part for the requirement of high strength and accuracy. The approach of the innovative process is adding solvent into photopolymer and ceramic powder to become very low viscosity slurry. The low viscosity slurry can provide a good coating ability while adding a new thin layer. Also, the solvent will be vaporized within a short time after the recoating process. The capillary force will help new layer of material self assembly to the previous layers and bring a strong bounding force. After the vaporizing of the solvent, it becomes a semi-solid substrate which the powder is connected by the sticky resin. The dynamic photo mask will bring the light selectively curing the cross section of the forming part. After the process of every layer completed, the cube of the semi-solid substrate and the green part will send to dissolve. The substrate will be scatter in the solvent and the green part will remain. A system has been build to evaluate the proposed 3S Rapid Prototyping process. A 3Dcomplex benchmark part has been build using this system. The layer thickness is 0.03mm and the X-Y resolution is 0.07mm. further study is carrying on for better automation and material properity.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

47

Liu, You-Feng, und 劉有峰. „Vapor-Liquid Equilibrium for Ternary System CO2 + H2 + Organic Solvent“. Thesis, 2009. http://ndltd.ncl.edu.tw/handle/72367484569520438594.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

48

Cheng, Sheng Hsing, und 鄭勝祥. „Solvent Effect on the Miscibility of Polymer Blend:PVAc-PEO System“. Thesis, 1997. http://ndltd.ncl.edu.tw/handle/16509935595477938400.

Der volle Inhalt der Quelle

Annotation:

碩士
中國文化大學
造紙印刷研究所
85
The miscibility of the poly(vinyl acetate) and poly( ethylene) blends hasbeen studied using the solvent casting method.Fine solvents of benzene,toluene,acetone,methyl alcohol, cycloheaxanone were used.The glass transition and melt-ing temperature of the crystalline-amorphous blends were measured by differentscanning calorimeter(DSC).It is shown that the blends of various compositionsare miscible in their molten state. The Flory-Huggins interaction parameterswere determined using the melting depression analysis. These parameters arenegative for the blends prepared from various casting solvents.Generally, toluene and cycloheaxanone are better solvents where the blends have a more homogeneous morphology. The Flory-Huggins interaction parameters are alsoplotted against the boiling temperatures of various casting solvents. A consis-tent correlation shows that more negative values of interaction parameters existbetween the boiling temperatures of 80 to 160℃ for blends of various composi-tions. This temperature range correpond to the toluene and cycloheaxanone usedin this study. It is indicated that the correlation is useful in selecting theapprop[riate solvents in preparing polymer blends. Further investigation onmore polymer blend and casting solvent systems are essential to generalizethis correlation.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

49

ZHANG, CAN-JIN, und 張燦金. „The manufacture of polyvinyl alcohol fiber with organic solvent system“. Thesis, 1990. http://ndltd.ncl.edu.tw/handle/64685205988209443637.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

50

Lan, Chang-Feng, und 藍長風. „Entropy configuration of amino acid solvent system with Voronoi cell distribution“. Thesis, 2016. http://ndltd.ncl.edu.tw/handle/52903080046819052241.

Der volle Inhalt der Quelle

Annotation:

碩士
國立中興大學
化學系所
104
To understand the physical behavior of solvent system in microscopic structure, such as amino acids in aqueous solution, the Voronoi tessellation method was employed to analyze space distribution of solvent surrounding the solute. The Voronoi polyhedra can be constructed through Delaunay simplexes. In our analysis, each non-hydrogen atom is treated as an independent element and a space-dependent factor is introduced for every element. In an equilibrium homogenous system, each Voronoi polyhedron is not identical but should have same average factor which is treated as the standard by definition. Compared with the standard factor of the homogenous system, i.e., pure water system, the factor on the solute surface should give out the information of interaction between the solvent and the solute. Therefore, this space-dependent factor must include the locally abnormal distribution with statistical significance. We then constructed the statistical entropy based on this factor to interpret thermodynamic behavior of amino acids, peptides and even proteins. Through analyzing the solvation differences between 20 standard amino acids, we quantify contribution of the different side-chain toward solvation of the solute surfaces in terms of statistical entropy.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

Dissertationen zum Thema „Solvent system“

Geben Sie eine Quelle nach APA, MLA, Chicago, Harvard und anderen Zitierweisen an