Robust industrially relevant membranes for CO₂ removal from aggressive natural gas feed streams were developed and characterized. Asymmetric hollow fiber membranes with defect-free selective skin layers on an optimized porous support substructure were successfully spun and subsequently stabilized by covalent crosslinking within the economical membrane formation process. Thermal treatment conditions, which promote sufficient crosslinking without introducing defects or undesired substructure resistance, were identified. It was found that crosslinking improves membrane efficiency and plasticization resistance as well as mechanical strength of fibers. The capability to maintain attractive separation performance under realistic operating conditions and durability against deleterious impurities suggests that the crosslinked fibers have great potential for use in diverse aggressive applications, even beyond the CO₂/CH₄ example explored in this work.

A collection of >3000 MOFs with experimentally confirmed structures were screened for performance in three binary separations: Ar/Kr, Kr/Xe, and Xe/Rn. 70 materials were selected for further analysis, and calculations were performed to account for inaccessible regions. Single component GCMC calculations were performed to parameterize IAST calculations on these 70 materials, and the curve fitting problem in IAST was discussed. IAST calculations were confirmed with extensive binary GCMC calculations. For each binary separation, materials were identified with predicted performance that surpasses the state of the art. "Reverse selective" materials, for which a smaller gas species is preferably adsorbed over a larger species, were explained on the basis of surface fractal geometry, computed via a corrected surface area calculation. The effect of temperature on separation performance was also examined.

Membrane separations are rapidly growing alternatives to traditionally expensive gas separation processes. For natural gas purification, membranes are used to remove carbon dioxide to prevent pipeline corrosion and increase the heating value of the natural gas. The robust chemical and physical properties of polyimide membranes make them ideal for the numerous components and high pressures associated with natural gas production. Typically, the performance of membranes changes over time as a result of physical aging of the polymer. Previous work shows that the thin selective layer of an asymmetric hollow fiber membrane, the morphology of choice for gas separations, ages differently than a thick dense film of the same material. Also, carbon dioxide, which is highly soluble in most polymers, can actively swell and plasticize polymer membranes at higher pressures. In this work, free acid groups present in the model polyimide are covalently crosslinked to stabilize the matrix against plasticization. Physical aging of two different crosslinked derivatives are compared to the free acid polyimide through gas permeation, gas sorption, and refractive index measurements. Thick (~50 m) and thin (~650 nm) films are examined to determine the effects of sample dimension on physical aging. The crosslinking mechanism employs diol substituents to form ester linkages through the free acid group. However, the annealing treatment, above the glass transition temperature, used to "reset" the thermal history of the films is found to form a new crosslinked polymer. Characterization of this new crosslinking mechanism reveals a high-temperature decarboxylation of the free acid creates free-radical phenyl groups which form covalent crosslinks through other portions of the polymer structure. Since ester crosslinks may be vulnerable to hydrolysis in aggressive gas feed streams, this new mechanism of crosslinking may create a more robust membrane for aggressive separations. In addition to the physical aging study, supercritical carbon dioxide conditioning of the two glycol crosslinked polyimides is compared to the free acid polymer. In this case, the free acid polymer is not crosslinked since the esterification crosslinking reaction occurs at much lower temperature than the decarboxylation mechanism. The free acid polymer displays an atypical permeation response under supercritical carbon dioxide conditions which suggests a structural reorganization of the polymer occurs. The crosslinked polymers do not exhibit this type of response. Mixed gas permeation confirms a substantial decrease in the productivity of the free acid polyimide and reveals the enhanced stability of the crosslinked polyimides following the supercritical carbon dioxide conditioning. Finally, examination of structurally similar fluorine-containing polyimides following approximately 18 years of aging allows the study of polymer structure on physical aging. A 6FDA-based polyimide is compared to a BPDA-based polyimide to understand the effects of bulky, CF3 groups on physical aging, and polyimides with diamine isomers reveal the effects of structural symmetry on physical aging.

As microalgas vêm sendo utilizadas na área ambiental nos processos de biomitigação de CO2, uma vez que o utilizam em seu metabolismo para produzirem biomassa celular, a qual pode ser utilizada para fins nutricional e comercial. Neste sentido, o presente trabalho teve como objetivo a obtenção de oligossacarídeos prebióticos oriundos de biomassa microalgal por meio de hidrólise fosfórica em diferentes condições moderadas de pH e termopressurização. Foi utilizada biomassa de um cultivo utilizado no sistema de tratamento de efluente gasoso de uma churrascaria de Curitiba, comparativamente com duas biomassas comerciais, Chlorella vulgaris e Spirulina platensis. Foram realizadas análises microscópicas e físico-químicas para a caracterização das biomassas, tais como umidade, cinzas, teor de carboidratos, lipídeos e proteínas. A partir da massa lipídica total foram realizadas transesterificações alcalinas e os resultados analisados por métodos cromatográficos, antes e após clarificação dos ésteres metílicos. A título de comparação inicial com as biomassas in natura, as biomassas passaram por pré-tratamentos: remoção dos lipídeos com organossolventes, purificação da parede celular com detergente SDS (Sódio Dodecil Sulfato) e recuperação do resíduo polimérico extraído pelo detergente. Estas biomassas derivadas bem como as integrais foram hidrolisadas em termopressurizador a 4,5 atm (156 oC), utilizando ácido fosfórico a pH 2,0 ou controles com água (solvólise). Adicionalmente foram realizados ensaios enzimáticos com α-amilase e β-1,3 glucanase nos oligossacarídeos resultantes dos hidrolisados fosfóricos das biomassas in natura. Com as três biomassas de microalgas in natura foi realizado planejamento fatorial 32, frente às variáveis ácido fosfórico (pH 2,5, 2,0, e 1,5) e pressão atmosférica (3 atm – 147 oC, 4,5 – 156 oC e 6,0 atm – 175 oC). Para todos os hidrolisados foram analisados pH após a hidrólise, teor de açúcar redutor e de açúcar total e perfil cromatográfico. Os oligossacarídeos obtidos foram utilizados como fonte de carbono para o cultivo de microrganismos probióticos, Bifidobacterium animalis e Lactobacillus casei, para avaliação do crescimento, pH e produção de ácidos graxos de cadeia curta (AGCC). Os resultados indicaram que apesar de ter sido inoculada uma cepa de C. vulgaris no sistema de fotobiorreatores de mitigação de CO 2 da churrascaria, não se instalou um cultivo puro e, portanto, foi denominado de mescla Devons. O componente majoritário para todas as biomassas foi proteína, sobretudo para S. platensis (59,5 %). As transesterificações alcalinas mostraram a eficiência no processo, indicando semelhança no perfil da cromatografia gasosa da mescla Devons e C. vulgaris. O tratamento com SDS mostrou maior eficiência na remoção de proteínas, sobretudo em S. platensis. As hidrólises das biomassas pré-tratadas mostraram maior teor de oligossacarídeos na amostra in natura para mescla Devons, deslipidificada e tratada com SDS para C. vulgaris e semelhança entre a in natura e os dois primeiros tratamentos para S. platensis. Os resultados dos ensaios enzimáticos indicaram predominância de oligossacarídeos oriundos de laminarina (β-1,3 glucana), portanto prebióticos e resistentes à ação amilásica do trato gastrointestinal (TGI) superior. Os resultados do planejamento fatorial mostraram que a biomassa in natura de S. platensis foi a que apresentou os melhores resultados de hidrólise em quantidade de açúcar liberado, seguida da biomassa de mescla Devons e C. vulgaris. As melhores condições de produção e pureza de oligossacarídeos foram próximas ao ponto central do planejamento fatorial. Os cultivos dos probióticos utilizando os hidrolisados fosfóricos permitiu o crescimento das baterias benéficas (Lactobacillus e Bifidobacterium), e diferenças no pH, bem como na produção de AGCC, sobretudo ácido lático, monitorado por cromatografia líquida. Portanto, este trabalho mostra que foram produzidos oligossacarídeos prebióticos a partir do tratamento fosfórico da biomassa de microalgas, resultando uma nova aplicação em potencial de tal biomassa formada a partir do CO2 e outros componentes voláteis presentes no efluente gasoso da churrascaria. / Microalgae have been utilized in the environmental area in CO2 biomitigation processes as they use it in their metabolism for the production of cellular biomass, which can then be utilized for nutritional and commercial purposes. Within this scope, the current research elected as the main objective, the obtention of nutraceutical oligosaccharides from microalgae biomasses through a phosphoric acid hydrolysis under different and moderated pH and thermopressurization conditions. One biomass, coming from a gaseous effluent treatment system from a steakhouse was compared to commercial biomasses, Chlorella vulgaris e Spirulina platensis. Microscopic and physicochemical analyses were carried for these biomasses characterization, namely moisture, ashes, carbohydrates, lipids and protein contents. Alkaline methyl transesterifications were realized in the total lipid fractions and then the corresponding products analyzed by chromatographic methods. As compared to the native biomasses, they were subjected to pretreatments: organic solvents removal of lipids, cell wall purification with detergent SDS (Sodium Dodecyl Sulphate) and recovery of polymeric molecules of the later extracts. These derived biomasses fractions, as well as the whole ones were partially or totally hydrolyzed with thermopressurization at 4.5 atm (156 °C) using diluted phosphoric acid at pH 2 or with water as controls (solvolysis). Enzyme assays were further performed with α- amylase and β-1,3 glucanase in the phosphoric acid hydrolyzed oligosaccharides from native biomasses. A 32 factorial design was carried out with the three samples of whole microalgae biomasses, considering the variables phosphoric acid pH (2.5, 2.0, e 1.5) and atmospheric pressure (3 atm – 147 oC, 4.5 – 156 oC and 6.0 atm – 175 o C). For all hydrolysates were analyzed pH after hydrolysis, total and reducing sugar contents and chromatographic profiles. The resulting oligosaccharide samples were offered as carbon source for the culture of probiotic microorganisms Bifidobacterium animalis e Lactobacillus casei for the evaluation of bacterial growth and short chain fatty acids (SCFAs) production. Overall results indicated that irrespective to the pure native of the C. vulgaris inoculum into the CO2 mitigation system of the steakhouse, a pure massive biomass did not result and hence the designation of Devons’ blend for. The major component of microalgae biomasses was protein, above all for S. platensis (59.5 %). Alkaline transesterification showed the efficiency of the process, indicating similarity among the methyl esters arising either from C. vulgaris or the Devons’ blend as analyzed by gas chromatography. SDS treatment was more efficient for protein removal in the case of S. platensis biomass. The pretreated biomasses once hydrolysed displayed higher oligosaccharide contents for the Devons’ blend native, C. vulgaris delipidified and SDS-treated sample as well some similarity between native and both pretreatments in the case of S. platensis. The enzymatic assay indicated predominance of laminarin oligosaccharides (β-1,3 glucan), therefore prebiotics are resistants to amylasic action in upper gastroinstestinal tract. The factorial design showed that the particular S. platensis native biomass led to the best result of hydrolysis to reducing simple and oligosaccharidic sugars, then decreasingly followed by the Devons’ blend and C. vulgaris and the best conditions for the production and purity of the oligosaccharides were close to the central point of the factorial design. Probiotic cultures from the phosphoric acid hydrolysates allowed the Lactobacillus and Bifidobacterium, beneficial bacteria growth, pH differences and short chain fatty acids production, above all, lactic acid, as monitored by high performance liquid chromatography. Therefore, this research indicated the feasibility of nutraceutical or prebiotic oligosaccharide production from microalgae biomasses, thus revealing a novel technological destination for these particular biomasses and fractions, once formed at the expense of CO2 and other volatile components from the gaseous effluent from a steakhouse.

D’après les limites d’acceptation pour la mise en décharge des déchets, les REFIOM (Résidus d’Epuration des Fumées d’Incinération d’Ordures Ménagères) sont considérés comme déchets dangereux, car ils libèrent des quantités importantes de chlorures et de métaux lourds lorsqu’ils entrent en contact avec de l’eau. Ces solides doivent par conséquent être traités avant leur mise en décharge. A côté des traitements visant l’acceptabilité des REFIOM en décharge, quelques recherches entrevoient la possibilité de valoriser ces résidus, notamment dans des matériaux cimentaires. <p>Les recherches présentées ici s’inscrivent dans cette tendance nouvelle et visent l’élaboration d’un procédé combinant traitement et valorisation des REFIOM. <p>Les REFIOM représentent en fait différents types de résidus provenant des installations que rencontrent les fumées issues de l’incinération des déchets. La composition des résidus diffère selon leur origine. Il est dès lors apparu essentiel de considérer chaque type de résidu séparément et de poursuivre l’élaboration d’un traitement sur un seul type de REFIOM. Nous avons choisi de concentrer les recherches sur les Cendres Volantes de Chaudière (CVC), ces résidus se retrouvant dans tout incinérateur. <p>Le traitement des CVC est basé sur l’extraction de fractions valorisables et la séparation de fractions contaminées, permettant d’obtenir des résidus acceptables en décharge ou, idéalement eux-mêmes valorisables. <p>Une séparation magnétique permet d’extraire environ 10% en poids des CVC mais ne semble pas exploitable dans le cadre du traitement des CVC car les particules magnétiques contiennent des impuretés (composés non magnétiques) et que le résidu final reste contaminé. <p>Une étude de la répartition des éléments en fonction de la taille des particules (granulochimie) est effectuée sur les CVC. Il apparaît intéressant de séparer la fraction inférieure à 38 µm obtenue lors d’une séparation granulométrique, effectuée en voie humide en utilisant une solution dense. En effet, cette fraction semble être nettement plus contaminée en Pb (soluble) que le reste des CVC. Une telle séparation constitue dès lors la première étape du traitement des CVC. Elle est suivie par des étapes de lavage des fractions obtenues, visant à extraire les sels solubles (chlorures et métaux). Les lavages sont envisagés à contre-courant afin d’utiliser au mieux l’eau de lavage. Une recirculation interne des solutions est également prévue, de sorte que, théoriquement, le procédé ne génère pas d’effluents liquides. Une étape de précipitation de composés métalliques (PbS dans ce cas-ci) est prévue après le lavage des boues. <p>Le procédé de traitement des CVC produirait ainsi des boues et des granulats décontaminés, des sels et des précipités métalliques. Seules certaines étapes du procédé ont été investiguées en laboratoire ;des essais supplémentaires sont encore nécessaires pour optimiser chaque étape, comprendre les phénomènes physico-chimiques qui se produisent et assurer des filières de valorisation. <p>/<p>Municipal Solid Waste Incineration (MSWI) fly ashes and Air Pollution Control (APC) residues are considered as hazardous waste according to the limits for the acceptance of waste at landfills, because high amounts of chlorides and heavy metals leach from the solids when those are in contact with water. These residues have thus to be treated before they can be accepted in landfill. Several treatments aim to limit the leaching of the residues. Beside these treatments, some research works go further the treatment and consider the valorisation of MSWI fly ashes and APC residues, e.a. in cementitious materials. <p>The present work follows the new trend and aims to build up a process that combines treatment and valorisation of MSWI fly ashes and APC residues. <p>MSWI fly ashes and APC residues come from the devices encountered by the flue gases from waste incineration. The residues composition differs according to their origin. It seems thus essential to consider each type of residues separately and to develop the treatment only on one sort of residue. Boiler Fly Ashes (BFA) were chosen because they exist in every modern MSWI plant. <p>The BFA treatment is based on the extraction of valorisable fractions and on the separation of contaminated fractions, which makes the final residues less hazardous; these final residues would then be acceptable in landfill, or, even better, be valorisable. <p>A magnetic sorting extracts ~10% (wt.) of BFA; however, such a separation would not be useful in a treatment process because the magnetic particles contain some impurities (non magnetic particles) and the final residue is still hazardous. <p>The repartition of the elements according to the particles size has been studied on BFA. It seems interesting to separate the BFA at 38 µm by a wet sieving process using a dense solution. The lower fraction presents a higher contamination in Pb (soluble) than the larger. Consequently, the first step of the BFA treatment consists of a wet sieving. Washing steps follow the sieving and aim to extract soluble salts (chlorides, heavy metals). These washings work in a counter-current way to optimise the use of water. The solutions are recycled in the process, which implies the absence of liquid effluents. A precipitation step of some metallic compounds (PbS in this case) is foreseen after the washing of the lower fraction. <p>The BFA treatment process would produce decontaminated sludge and coarse fractions, salts and metallic compounds. Some steps of the process have been investigated at lab-scale; further studies are necessary to optimise each step, to understand the observed reactions and to guarantee valorisation channels. / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished