An experimental pressure swing adsorption unit has been constructed and used to investigate the separation of carbon dioxide from carbon dioxide enriched air using both an activated carbon and a type 5A molecular sieve adsorbent. Continuous, cyclic operation was achievedusing a pair of fixed bed adsorbers. At any one time the feed gas entered one bed at a high pressure and part of the purified gas was returned to the other bed at a reduced pressure to provide countercurrent regeneration of the adsorbent. The beds of adsorbent used were each nominally 0.165m diameter and Im. deep. Separations were carried out at approximately ambient temperature using air flow rates in the range 0.15 to 0.95 kg/m2s and inlet carbon dioxide concentrations'in the range 0.1 to 1.5% v/v. Adsorption pressures of 2 to 6.4 bar were examined, the desorption pressure being maintained throughout at essentially 1.0 bar. The period time was varied from 30 to 900 seconds and the revert ratio (i. e. the ratio of the product gas returned for desorption to the total feed rate to the unit) was varied from 0 to 1.0. The carbon dioxide separation efficiency was found to increase markedly as the adsorption pressure and the revert ratio were increased whereas it was relatively insensitive to variations in feed rate and, more particularly, feed concentration. The performance of the molecular sieve adsorbent was found to be very sensitive to the presence of moisture in the feed gas. In contrast the carbon dioxide efficiencies observed with Lhe activated carbon were unaffected by the presence of small amounts (circa 100 ppm) of moisture in the feed. A theoretical model has been proposed for predicting the performance of pressure swing adsorption systems of the type investigated and approximate analytical equations and more precise numerical techniques have been established to represent its solution. The approximate analytical solutions were found to give close agreement with the more precise methods examined under conditions corresponding to low values of a dimensionless period time parameter. The proposed theoretical model incorporates an effective irean mass transfer coefficient to represent the diffusion process within the adsorbent particles. Methods for estimation of the value of this coefficient based on the limiting conditions of a periodic constant surface flux or a periodic constant surface concentration are presented. The experimental performance data were analysed in terms of the proposed analytical solution to give values of the apparent solid phase mass transfer coefficient for comparison with those predicted theoretically. In general the apparent experimental values were consistently less than the predicted values. In addition the relationship between the experimental and predicted coefficients was found to be dependent on both the nature of the adsorbent and a parameter formed by the product of the revert ratio and the adsorption to desorption pressure ratio. Empirical correlating equations which incorporate this dependence are presented.

The main theme of this dissertation is to engineer nanoporous materials and nanostructured surfaces for applications in gas separation membranes. Tunable methods have been developed to create inorganic hydroxide nanostructures on zeolite surfaces, and used to control the inorganic/polymer interfacial morphology in zeolite/polymer composite membranes. The study of the structure-property relationships in this material system showed that appropriate tuning of the surface modification methods leads to quite promising structural and permeation properties of the membranes made with the modified zeolites. First, a facile solvothermal deposition process was developed to prepare roughened inorganic nanostructures on zeolite pure silica MFI crystal surfaces. The functionalized zeolite crystals resulted in high-quality ̒mixed matrix̕ membranes, wherein the zeolite crystals were well-adhered to the polymeric matrix. Substantially enhanced gas separation characteristics were observed in mixed matrix membranes containing solvothermally modified MFI crystals. Gas permeation measurements on membranes containing nonporous uncalcined MFI revealed that the performance enhancements were due to significantly enhanced MFI-polymer adhesion and distribution of the MFI crystals. Solvothermal deposition of inorganic nanostructures was successfully applied to aluminosilicate LTA surfaces. Solvothermal treatment of LTA was tuned to deposit smaller/finer Mg(OH)₂ nanostructures, resulting in a more highly roughened zeolite surface. Characterization of particles and mixed matrix membranes revealed that the solvothermally surface-treated LTA particles were promising for application in mixed matrix membranes. Zeolite LTA materials with highly roughened surfaces were also successfully prepared by a new method: the ion-exchange-induced growth of Mg(OH)₂ nanostructures using the zeolite as the source of the Mg²⁺ ions. The size/shape of the inorganic nanostructures was tuned by adjusting several parameters such as the pH of the reagent solution and the amount of magnesium in the substrates and systematic modification of reaction conditions allowed generation of a good candidate for application in mixed matrix membranes. Zeolite/polymer adhesion properties in mixed matrix membranes were improved after the surface treatment compared to the untreated bare LTA. Surface modified zeolite 5A/6FDA-DAM mixed matrix membranes showed significant enhancement in CO₂ permeability with slight increases in CO₂/CH₄ selectivity as compared to the pure polymer membrane. The CO₂/CH₄ selectivity of the membrane containing surface treated zeolite 5A was much higher than that of membrane with untreated zeolite 5A. In addition, the use of metal organic framework (MOF) materials has been explored in mixed matrix membrane applications. ZIF-90 crystals with submicron and 2-μm sizes were successfully synthesized by a nonsolvent induced crystallization technique. Structural investigation revealed that the ZIF-90 particles synthesized by this method had high crystallinity, microporosity and thermal stability. The ZIF-90 particles showed good adhesion with polymers in mixed matrix membranes without any compatibilization. A significant increase in CO₂ permeability was observed without sacrificing CO₂/CH₄ selectivity when Ultem® and Matrimd® were used as the polymer matrix. In contrast, mixed matrix membranes with the highly permeable polymer 6FDA-DAM showed substantial enhancement in both permeability and selectivity, as the transport properties of the two phases were more closely matched.

The current work focused on defining the material science options to fabricate novel, high performing ethylene/ethane (C₂H₄/C₂H₆) separation carbon molecular sieve (CMS) dense film membranes. Three polymer precursors: Matrimid®, 6FDA-DAM and 6FDA:BPDA-DAM were used as precursors to the CMS membranes. CMS performances were tailored by way of tuning pyrolysis conditions such as the pyrolysis temperature, heating rate, pyrolysis atmosphere etc. The CMS dense film membranes showed attractive C₂H₄/C₂H₆ separation performance far exceeding the polymeric membrane performances. Semi-quantitative diffusion size pore distributions were constructed by studying the transport performance of a range of different penetrant gases as molecular sized probes of the CMS pore structure. This, in conjunction with separation performance data, provided critical insights into the structure-performance relationships of the CMS materials. The effects of testing conditions, i.e. the testing temperature, pressure and feed composition on C₂H₄/C₂H₆ separation performance of CMS dense films were also analyzed. These studies were useful not just in predicting the membrane behavior from a practical stand-point, but also in a fundamental understanding of the nature of CMS membrane separation. The study helped clarify why CMS membranes outperform polymeric membrane performance, as well as allowed comparison between CMS derived from different precursors and processing conditions. The effects on C₂H₄/C₂H₆ separation in the presence of binary gas mixture were also assessed to get a more realistic measure of the CMS performance resulting from competition and bulk flow effects. The current work thus establishes a framework for guiding research ultimately aimed at providing a convenient, potentially scalable hollow fiber membrane formation technology for C₂H₄/C₂H₆ separation

Olefin/paraffin separation is a large potential market for membrane applications. Carbon molecular sieve membranes (CMS) are promising for this application due to the intrinsically high separation performance and the viability for practical scale-up. Intrinsically high separation performance of CMS membranes for olefin/paraffin separations was demonstrated. The translation of intrinsic CMS transport properties into the hollow fiber configuration is considered in detail. Substructure collapse of asymmetric hollow fibers was found during Matrimidﾮ CMS hollow fiber formation. To overcome the permeance loss due to the increased separation layer thickness, 6FDA-DAM and 6FDA/BPDA-DAM polyimides with higher rigidity were employed as alternative precursors, and significant improvement has been achieved. Besides the macroscopic morphology control of asymmetric hollow fibers, the micro-structure was tuned by optimizing pyrolysis temperature protocol and pyrolysis atmosphere. In addition, unexpected physical aging was observed in CMS membranes, which is analogous to the aging phenomenon in glassy polymers. For performance evaluation, multiple "proof-of-concept" tests validated the viability of CMS membranes under realistic conditions. The scope of this work was expanded from binary ethylene/ethane and propylene/propane separations for the debottlenecking purpose to mixed carbon number hydrocarbon processing. CMS membranes were found to be olefins-selective over corresponding paraffins; moreover, CMS membranes are able to effectively fractionate the complex cracked gas stream in a preferable way. Reconfiguration of the hydrocarbon processing in ethylene plants is possible based on the unique CMS membranes.

<p>DESCARTES is a light-weight, balloon-borne grab sampler for stratospheric long-lived tracers developed at the University of Cambridge. 33 flights have been performed with two versions of the instrument at northern latitudes by the DESCARTES team at the Swedish Institute of Space Physics (IRF) in Kiruna during the years 1997-2000.</p><p>The general interest in long-lived stratospheric tracers is to study the general global circulation of air in the stratosphere and the exchange between the stratosphere and troposphere. In the study of chemical ozone depletion in the stratosphere, long-lived tracers serve as an important reference to distinguish between the variations in ozone of dynamical and chemical origin.</p><p>This thesis focuses on calibrations and quality assessment of the measurements made with the third version of the DESCARTES instrument based at IRF. Two different general approaches to make calibrations are discussed. Uncertainty estimations for both of these methods are made and the results are tested by laboratory methods and by comparisons to other instruments, including comparisons between two versions of DESCARTES. Analyzed and calibrated flight data for all successful flights are presented.</p><p>The basic principle of the instrument is to chemically adsorb a number of tracers (in practice only CFC-11 is measured) in an adsorption bed of Carboxen in a micro trap through which the sampled air is driven by a pump. After recovery the adsorbed species in the trap is desorbed by electrical heating of the trap and analysed by gas chromatography.</p><p>The resulting estimated mixing ratios from the instrument are directly dependent on the adsorption of the sampled species being quantitative in the traps. Laboratory experiments are described using two traps in series, where the performance of the first is tested by sampling the breakthrough by the second. A model is developed to recreate these tests in order to be able to compensate for breakthrough during flights. The model showed that the adsorption in the traps is not explained by simple chromatographic theory and the results allow us only to give an estimation of the uncertainty due to breakthrough.</p> / <p>DESCARTES är ett lätt ballongburet provtagningsinstrument för stratosfäriska spårgaser. Det är utvecklat vid universitetet i Cambridge. DESCARTES-teamet vid Institutet för rymdfysik (IRF) i Kiruna har under åren 1997-2000 genomfört 33 flygningar med två olika versioner av instrumentet från nordliga latituder.</p><p>Det generella intresset av långlivade stratosfäriska spårgaser är att studera den globala cirkulationen i stratosfären och utbytet av luft mellan stratosfären och troposfären. För studier av den kemiska ozonnedbrytningen i stratosfären spelar långlivade spårgaser en avgörande roll som referens för att skilja mellan variation i ozonkoncentrationen av kemiskt och dynamiskt ursprung.</p><p>Denna avhandling fokuserar på kalibrering och kvalitetssäkring av mätningar gjorda med den tredje versionen av DESCARTES-instrumentet hemmahörande vid IRF. Två i grunden olika kalibreringsförfaranden för instrumentet behandlas. Osäkerhetsuppskattningar är gjorda för båda dessa metoder och resultaten är prövade i laboratorietester. Dessutom jämförs resultaten från två versioner av DESCARTES och andra instrument. Analyserade data från samtliga lyckade flygningar presenteras.</p><p>Den grundläggande principen för instrumentet är att pumpa luftprover genom en fälla som innehåller en bädd av det kemiska adsorptionsmaterialet Carboxen, som adsorberar ett antal spårgaser. När instrumentet hämtats tillbaka efter en flygning gasas de adsorberade ämnena i fällan ut genom att fällan upphettas på elektrisk väg. De utgasade ämnena analyseras med gaskromatografi. I praktiken kan endast CFC-11 analyseras.</p><p>Den slutgiltiga bestämningen av blandningsförhållandet från instrumentet är direkt beroende av att adsorptionen i fällorna för de ämnen man vill undersöka är fullständig. En serie laboratorieexperiment har genomförts där två likadana fällor kopplats efter varandra. På så sätt har tillförlitligheten av den första fällan kunnat studeras genom att uppmäta hur mycket som bryter igenom till den andra fällan. En modell har utvecklats för att förstå resultatet av dessa tester och kunna kompensera för eventuella genombrott vid provtagning under flygningar. Modellen visade att adsorptionen i fällorna inte kan förklaras med enkel kromatografisk teori. Resultaten ger endast möjlighet att bedöma osäkerheten i mätningarna till följd av risken för genombrott.</p>

DESCARTES is a light-weight, balloon-borne grab sampler for stratospheric long-lived tracers developed at the University of Cambridge. 33 flights have been performed with two versions of the instrument at northern latitudes by the DESCARTES team at the Swedish Institute of Space Physics (IRF) in Kiruna during the years 1997-2000. The general interest in long-lived stratospheric tracers is to study the general global circulation of air in the stratosphere and the exchange between the stratosphere and troposphere. In the study of chemical ozone depletion in the stratosphere, long-lived tracers serve as an important reference to distinguish between the variations in ozone of dynamical and chemical origin. This thesis focuses on calibrations and quality assessment of the measurements made with the third version of the DESCARTES instrument based at IRF. Two different general approaches to make calibrations are discussed. Uncertainty estimations for both of these methods are made and the results are tested by laboratory methods and by comparisons to other instruments, including comparisons between two versions of DESCARTES. Analyzed and calibrated flight data for all successful flights are presented. The basic principle of the instrument is to chemically adsorb a number of tracers (in practice only CFC-11 is measured) in an adsorption bed of Carboxen in a micro trap through which the sampled air is driven by a pump. After recovery the adsorbed species in the trap is desorbed by electrical heating of the trap and analysed by gas chromatography. The resulting estimated mixing ratios from the instrument are directly dependent on the adsorption of the sampled species being quantitative in the traps. Laboratory experiments are described using two traps in series, where the performance of the first is tested by sampling the breakthrough by the second. A model is developed to recreate these tests in order to be able to compensate for breakthrough during flights. The model showed that the adsorption in the traps is not explained by simple chromatographic theory and the results allow us only to give an estimation of the uncertainty due to breakthrough. / DESCARTES är ett lätt ballongburet provtagningsinstrument för stratosfäriska spårgaser. Det är utvecklat vid universitetet i Cambridge. DESCARTES-teamet vid Institutet för rymdfysik (IRF) i Kiruna har under åren 1997-2000 genomfört 33 flygningar med två olika versioner av instrumentet från nordliga latituder. Det generella intresset av långlivade stratosfäriska spårgaser är att studera den globala cirkulationen i stratosfären och utbytet av luft mellan stratosfären och troposfären. För studier av den kemiska ozonnedbrytningen i stratosfären spelar långlivade spårgaser en avgörande roll som referens för att skilja mellan variation i ozonkoncentrationen av kemiskt och dynamiskt ursprung. Denna avhandling fokuserar på kalibrering och kvalitetssäkring av mätningar gjorda med den tredje versionen av DESCARTES-instrumentet hemmahörande vid IRF. Två i grunden olika kalibreringsförfaranden för instrumentet behandlas. Osäkerhetsuppskattningar är gjorda för båda dessa metoder och resultaten är prövade i laboratorietester. Dessutom jämförs resultaten från två versioner av DESCARTES och andra instrument. Analyserade data från samtliga lyckade flygningar presenteras. Den grundläggande principen för instrumentet är att pumpa luftprover genom en fälla som innehåller en bädd av det kemiska adsorptionsmaterialet Carboxen, som adsorberar ett antal spårgaser. När instrumentet hämtats tillbaka efter en flygning gasas de adsorberade ämnena i fällan ut genom att fällan upphettas på elektrisk väg. De utgasade ämnena analyseras med gaskromatografi. I praktiken kan endast CFC-11 analyseras. Den slutgiltiga bestämningen av blandningsförhållandet från instrumentet är direkt beroende av att adsorptionen i fällorna för de ämnen man vill undersöka är fullständig. En serie laboratorieexperiment har genomförts där två likadana fällor kopplats efter varandra. På så sätt har tillförlitligheten av den första fällan kunnat studeras genom att uppmäta hur mycket som bryter igenom till den andra fällan. En modell har utvecklats för att förstå resultatet av dessa tester och kunna kompensera för eventuella genombrott vid provtagning under flygningar. Modellen visade att adsorptionen i fällorna inte kan förklaras med enkel kromatografisk teori. Resultaten ger endast möjlighet att bedöma osäkerheten i mätningarna till följd av risken för genombrott.

Made available in DSpace on 2014-12-17T14:07:00Z (GMT). No. of bitstreams: 1 AuristelaCM_DISSERT.pdf: 1278248 bytes, checksum: cbdcf9cab5a2fc14113da4b21bc60b64 (MD5) Previous issue date: 2011-11-28 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The mesoporous molecular sieves of the MCM-41 and FeMCM-41 type are considered promissory as support for metals used as catalysts in oil-based materials refine processes and as adsorbents for environmental protection proposes. In this work MCM-41 and FeMCM41 were synthesized using rice husk ash - RHA as alternative to the conventional silica source. Hydrothermal synthesis was the method chosen to prepare the materials. Pre-defined synthesis parameters were 100?C for 168 hours, later the precursor was calcinated at 550?C for 2 hours under nitrogen and air flow. The sieves containing different proportions of iron were produced by two routes: introduction of iron salt direct synthesis; and a modification post synthesis consisting in iron salt 1 % and 5% impregnation in the material followed by thermal decomposition. The molecular sieves were characterized by X ray diffraction XRD, Fourier transform infrared spectroscopy FT-IR, X ray fluorescence spectroscopy XFR, scanning electronic microscopy SEM, specific surface area using the BET method, Termogravimetry TG. The kinetic model of Flynn Wall was used with the aim of determining the apparent activation energy of the surfactant remove (CTMABr) in the MCM- 41 porous. The analysis made possible the morphology characterization, identifying the presence of hexagonal structure typical for mesoporous materials, as well as observation of the MCM41 and iron of characteristic bands. / As peneiras moleculares mesoporosas do tipo MCM-41 e FeMCM-41, s?o consideradas promissoras como suporte para metais, usadas como catalisadores em processos de refino de materiais a base de petr?leo e como adsorventes com o prop?sito de prote??o ambiental. Neste trabalho MCM-41 e FeMCM-41 foram sintetizadas utilizando a cinza da casca de arroz CCA, como alternativa para a fonte de s?lica. O m?todo escolhido foi a s?ntese hidrotermal para o preparo dos materiais, a temperatura de 100 ?C por 168 horas em estufa, posteriormente foi calcinado a 550 ?C por 2 horas sob fluxo de nitrog?nio e ar. As peneiras moleculares contendo diferentes propor??es de ferro foram produzidas por duas rotas: introdu??o do sal de ferro no gel de s?ntese e impregna??o de 1% e 5% de ferro no MCM-41 sintetizado. As peneiras moleculares foram caracterizadas por difra??o de raios X DRX, espectroscopia no infravermelho por transformada de Fourier (Fourier transform infrared spectroscopy FT-IR), espectroscopia de fluoresc?ncia de raios X FRX, microscopia eletr?nica de varredura MEV, ?rea superficial espec?fica atrav?s do m?todo BET e Termogravimetria TG. O modelo cin?tico de Flynn Wall foi utilizado com o objetivo de determinar a energia de ativa??o aparente da remo??o do surfactante (CTMABr) nos poros do MCM-41. As an?lises possibilitaram a caracteriza??o morfol?gica, identificando a presen?a da estrutura hexagonal t?pica dos materiais mesoporosos, assim como das bandas caracter?sticas do MCM41 e do ferro.

Submitted by Emanuel Varela Cardoso (emanuel.varela@ufcg.edu.br) on 2018-08-23T19:44:24Z No. of bitstreams: 1 THIAGO RODRIGO BARBOSA BARROS – DISSERTAÇÃO (PPGEQ) 2017.pdf: 2174476 bytes, checksum: 3268fd475d20f6eff1be072f2e7fa4e3 (MD5) / Made available in DSpace on 2018-08-23T19:44:24Z (GMT). No. of bitstreams: 1 THIAGO RODRIGO BARBOSA BARROS – DISSERTAÇÃO (PPGEQ) 2017.pdf: 2174476 bytes, checksum: 3268fd475d20f6eff1be072f2e7fa4e3 (MD5) Previous issue date: 2017-02-20 / Capes / Biodiesel, que é produzido a partir de óleos vegetais ou gorduras animais através da reação de transesterificação com álcool é um excelente substituto para o diesel de petróleo por ser um combustível biodegradável derivado de fontes renováveis. A peneira molecular MCM-41 apresenta potencial para processamento de ácidos graxos visando a produção de biodiesel, por controle da composição química e por tratamentos químicos posterior a sua síntese. A inserção de óxidos metálicos pode proporcionar um aumento no desempenho catalítico da peneira molecular, possibilitando a preparação de catalisadores com maior atividade, seletividade e estabilidade térmica. O presente trabalho tem como objetivo principal a obtenção de biodiesel a partir da reação de transesterificação do óleo de soja utilizando o catalisador MoO3/25CeO2/MCM-41. Para tal afinidade, a peneira molecular foi preparada partindo-se de um gel com a seguinte composição molar da mistura reacional: 1SiO2 : 0,30 CTABr : 11 NH3 : 144 H2O. A incorporação do cério e molibdênio (em peso) no suporte MCM-41 foi por via seca. Através dos difratogramas foi possível identificar os picos característicos da peneira molecular MCM-41, como também as fases dos óxidos de cério e molibdênio na estrutura da peneira molecular, confirmando os processos de impregnação. Por meio da isoterma de adsorção de nitrogênio a peneira molecular apresentou uma área superficial SBET de 1072 m2/g e isoterma do tipo IV característica de materiais mesoporosos. O catalisador contendo 15% em peso de molibdênio e 25% em peso de cério atingiu a maior conversão em éster metílico em torno de 93% como também densidade de 0.8832 g/cm3, viscosidade cinemática 4,044 mm2/s e acidez de 0,49 mg KOH/g. / Biodiesel, which is produced from vegetable oils or animal fats by transesterification reaction with alcohol, is an excellent substitute for diesel oil being a biodegradable fuel derived from renewable. The molecular sieve MCM-41 has the potential to process fatty acids aiming biodiesel production, by controlling the chemical composition and subsequent chemical treatments to their synthesis. The inclusion of metallic oxides can provide an increase in catalytic performance of the molecular sieve, allowing th e preparation of catalysts with higher activity, selectivity and thermal stability. This study aims to obtain biodiesel from the transesterification reaction of soybean oil using the catalyst MoO3/25CeO2/MCM-41. To this affinity, the molecular sieve was prepared starting with a gel with the following molar composition of the reaction mixture: 1SiO2 : 0,30 CTABr : 11 NH3 : 144 H2O. The incorporation of cerium and molybdenum (by weight) in the MCM-41 was supported by dry. Through the XRD patterns it was possible to identify the peaks characteristic of MCM-41 molecular sieve, as well as phases of cerium and molybdenum oxides in the molecular sieve structure, confirming the impregnation process. By means of the nitrogen adsorption isotherm molecular sieve had a surface area SBET de 1072 m2/g and isotherm type IV characteristic of mesoporous materials. The catalyst containing 15% by weight molybdenum and 25% by weight cerium reached the highest methyl ester conversion around 93% as well as density of 0.8832 g/cm3, kinematic viscosity 4,044 mm2/s and acidity of 0,49 mg KOH/g