Characterization of semi-permeable films promotes the systematic selection of membranes and process design. When acquiring the diffusive and sorption properties of gas transport in non-porous membranes, the time lag method is considered the conventional method of characterization. The time lag method involves monitoring the transient accumulation of species due to permeation on a fixed volume present in a downstream reservoir. In the thesis at hand, an alternative approach to the time lag technique is proposed, termed as the short cut method. The short cut method appoints the use of a two reservoir system, where the species decay in the upstream face of the membrane is monitored, in combination with the accumulation on the downstream end. The early and short time determination of membrane properties is done by monitoring the inflow and outflow flux profiles, including their respective analytical formulas. The newly proposed method was revealed to have estimated the properties at 1/10 the required time it takes for the classical time lag method, which also includes a better abidance to the required boundary conditions. A novel design of the upstream reservoir, consisting of a reference and working volume, is revealed, which includes instructional use, and the mechanics involved with its operation. Transient pressure decay profiles are successfully obtained when the reference and working volumes consisted of only tubing. However when tanks were included in the volumes, large errors in the decay were observed, in particular due to a non-instantaneous equilibration of the pressure during the start up. This hypothesis was further re-enforced by examining different upstream tank-based configurations. iii In the end, a validated numerical model was constructed for the purpose of simulating the two reservoir gas permeation system. A modified form of the finite differences scheme is utilized, in order to account for a concentration-dependent diffusivity of penetrants within the membrane. Permeation behavior in a composite membrane system was disclosed, which provided a new perspective in analyzing the errors associated with the practical aspect of the system.

Zeolite membranes are considered to be a promising alternative to polymeric membranes and they have the potential to separate gases under harsh conditions. Silicalite-1 membranes in particular are easy to prepare and suitable for several industrial applications. In this research project, silicalite-1/ceramic composite membranes were prepared using the pore plugging hydrothermal synthesis method and supports with zirconium oxide and/or titanium oxide as active layers. The effect of the support’s pore size on the morphology and permeation performance of the prepared membranes was investigated using five supports with different active layer pore sizes in the range of 0.14 – 1.4 m. The prepared membranes were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), electron diffraction spectrometer (EDS), single gas and binary gas mixtures permeation tests. The results confirmed the presence of a typical silicalite-1 zeolite structure with a high internal crystalline order grown inside the pores of the active layer of the supports, with a dense film covering most of the supports active layers. Silicalite-1 crystals in the prepared membranes were preferably oriented with either a- or b-axes perpendicular to the support surface. Single gas permeation results illustrated that the observed permeances were not directly related to the kinetic diameter of permeants. Instead, the transport of the studied gases through the prepared membranes occurred by adsorption followed by surface diffusion mechanism. Binary gas tests performed with CO2 and N2 mixtures showed that the prepared membranes were selective and very permeable with CO2/N2 permselectivities up to 30 and a CO2 permeances in the order of 10-6 mol m-2 Pa-1 s-1. A model was developed, based on Maxwell−Stefan equations and Extended Langmuir adsorption isotherm, to describe the transport of binary CO2 and N2 mixtures through the prepared silicalite-1 membranes. The model results showed that the exchange diffusivities (D12 and D21) were less dependent on the feed pressure and feed composition compared to the permeances and the permselectivities. Hence, they are more appropriate to characterize the intrinsic transport properties of the prepared silicalite-1 membranes.

Produced water (PW) is an oil and gas extraction byproduct that contains a variety of contaminants. PW was traditionally disposed of in deep injection wells or released into the environment. However, these practices may have environmental consequences. The reuse of PW for power water injection (PWI) can help to reduce these impacts by providing a renewable source of water that can be used to maintain production pressure and increase oil recovery. Additionally, the reuse of PW can save oil companies money on water treatment, transporting and disposal costs. Ultrafiltration membranes are used to separate oil from water in produced water. However, ultrafiltration membranes are susceptible to severe fouling by oil molecules, which can reduce their performance. This research investigated the use of Pebax® coating to improve the performance of ultrafiltration membranes for oily-water mixture. The results showed that Pebax® coating can enhance the resistance of membranes to fouling to fouling. The optimal balance between fouling resistance and water flux was found to be achieved by applying very thin coating layers and using appropriate solvents (e.g., n-Butanol). The Pebax® coating creates an essentially defect-free layer on the membrane surface, as seen by the SEM images. Additionally, the coated membranes outperformed the untreated membranes in terms of fouling resistance. This result demonstrated that oil molecules showed less adhesion on the surface and penetration inside membrane pores, thus reducing fouling. Overall, the findings of this research point to PEBAX® coating as a potential means of enhancing the ability of ultrafiltration membranes to resist fouling in the process of separating oil from water. To analyze the long-term performance of coated membranes and to optimize the coating procedure, additional research is required.

The vast majority of commercial gas separation membrane systems are polymeric because of processing feasibility and cost. However, polymeric membranes designed for gas separations have been known to have a trade-off between permeability and selectivity as shown in Robeson's upper bound curves. The search for membrane materials that transcend Robeson's upper bound has been the critical issue in research focused on membranes for gas separation in the past decade. To that end, many researchers have explored the idea of mixed matrix membranes (MMMs). These membranes combine a polymer matrix with inorganic molecular sieves such as zeolites. The ideal filler material in MMMs should have excellent properties as a gas adsorbent or a molecular sieve, good dispersion properties in the polymer matrix of submicron thickness, and should form high quality interfaces with the polymer matrix. In order to increase gas permeance and selectivity of polymeric membranes by fabricating MMMs, we have fabricated mixed matrix membranes using carbon nanotubes (CNTs) and nano-sized mesoporous silica. Mixed matrix membranes containing randomly oriented CNTs showed that addition of nanotubes to a polymer matrix could improve its selectivity properties as well as permeability by increasing diffusivity. Overall increases in permeance and diffusivity for all tested gases suggested that carbon nanotubes can provide high diffusivity tunnels in the CNT within the polymer matrix. This result agreed well with molecular simulation estimations. In order to prepare ordered CNTs membranes, we have developed a simple, fast, commercially attractive, and scalable orientation method. The oriented CNT membrane sample showed higher permeability by one order of magnitude than the value predicted by a Knudsen model. This CNT membrane showed higher selectivities for CO₂ over other gas molecules because of preferential interaction of CO₂ with the amine functionalized nanotubes, demonstrating practical applications in gas separations. Recently, mesoporous molecular sieves have been used in MMMs to enhance permeability or selectivity. However, due to their micrometer scale in particle size, the composite membrane was extremely brittle and tended to crack at higher silica loading. In this study, we have developed fabrication techniques to prepare MMMs containing mesoporous MCM-41 nanoparticles on the order of ~50 nm in size. This smaller nanoparticle lead to higher polymer/particle interfacial area and provides opportunity to synthesize higher loading of molecular sieves in polymer matrix up to ~80 vol%. At 80 vol% of nano-sized MCM-41 silica loading, the permeability of the membrane increased dramatically by 300 %. Despite these increases in permeability, the separation factor of the MMMs changed only slightly. Therefore, these nanoscale molecular sieves are more suitable for commercialization of MMMs with very thin selective layers than are micro-sized zeolites or molecular sieves. / Ph. D.

Polymeric membranes for gas separation are limited in their performance by a trade-off between permeability and selectivity. New methods of design are necessary in making membranes, which can show both high permeability and selectivity. A mixed matrix membrane is one such particular design, which brings in the superior gas separation performance of inorganic membranes together with the easy processability and price of the polymers. In a mixed matrix membrane, the inorganic phase is dispersed in the polymeric continuous phase. Nanocomposite membranes have a more sophisticated design with a thin separation layer on top of a porous support. The objective of this research was to fabricate thin SWNT nanocomposite membranes for gas separation, which have both high permeability and selectivity. SWNT/polyacrylic nanocomposite membranes were fabricated by orienting the SWNTs by high vacuum filtration. The orientation of SWNTs on top of the porous support was sealed by UV polymerization. For making these membranes, the CNTs were purified and cut into small open tubes simultaneously functionalizing them with COOH groups. Gas sorption of CO2 in COOH functionalized SWNTs was lower than in purified SWNTs. Permeabilities in etched membrane were higher than Knudsen permeabilities by a factor of 8, and selectivities were similar to Knudsen selectivities. In order to increase the selectivities, SWNTs were functionalized with zwitterionic functional groups. Gas sorption in zwitterion functionalized SWNTs was very low compared to in COOH functionalized SWNTs. This result showed that the zwitterionic functional groups are kinetically blocking the gas molecules from entering the pore of the CNT. SWNT/polyamide nanocomposite membranes were fabricated using the zwitterion functionalized SWNTs by interfacial polymerization. The thickness of the separation layer was around 500nm. Gas permeabilities in the CNT membranes increased with increasing weight percentage of the SWNTs. Gas permeabilities were higher in COOH SWNT membrane than in zwitterion SWNT membrane. Gas selectivities were similar to the Knudsen selectivities, and also to the intrinsic selectivities in the pure polyamide membrane. The water flux in SWNT-polyamide membranes increased with increasing weight percentage of zwitterion functionalized SWNTs, along with a slight increase in the salt rejection. Membranes exhibited less than 1% variability in its performance over three days. / Ph. D.

Dans le cadre d’un projet d’Intensification de Procédés de Rhodia, nous avons développé des dispositifs millifluidiques fonctionnant dans des conditions opératoires inexplorées auparavant au labortoire, jusqu’à 300 °C et 50 bar, pour l’acquisition de données physicochimiques. Ainsi, une étude rhéologique sur des solutions de sel de nylon a été réalisée, ce qui a permis de fournir une nouvelle corrélation utile pour le dimensionnement du procédé industriel de polymérisation du polyamide-6,6. Par ailleurs, une étude cinétique de la polymérisation de l’éthylène glycol avec l’acide adipique a permis de déterminer les coefficients cinétiques de la réaction ainsi que l’énergie d’activation correspondante. Finalement un procédé miniaturisé avec élimination de l’eau produite par la réaction de polycondensation permettant de déplacer l’équilibre atteint par la réaction a été mis en œuvre ainsi que son modèle. / This work originated from a Rhodia’s Process Intensification project, where new physicochemical data are needed. We have developed at the laboratory new millifluidic devices which operate in conditions previously unexplored: up to 300 °C and 50 bar. A rheological study on nylon salt solutions was carried out and a new correlation based on the experimental results was provided. It is now used in the design of the industrial process of polyamide-6,6 synthesis. Moreover, a kinetic study on the polymerization of ethylene glycol with adipic acid allowed us to determine the kinetic coefficients of the reaction and the corresponding activation energy. Finally, a millifluidic process where the water produced by the polymerization reaction is eliminated by stripping and membrane separation was also developed, allowing for the chemical equilibrium to be shifted. A model describing this process has also been proposed.

Porous materials (e.g. zeolites, activated carbon, etc.) have found various applications in industry, such as the use as sorbents, catalyst supports and membranes for separation processes. Recently, much attention has been focused on synthesizing porous polymer materials. A vast amount of tailor-made polymeric systems with tunable properties has been investigated. Very often, however, the starting substances for these polymers are of petrochemical origin, and the processes are all in all not sustainable. Moreover, the new polymers have challenged existing characterizing methodologies. These have to be further developed to address the upcoming demands of the novel materials. Some standard techniques for the analysis of porous substances like nitrogen sorption at 77 K do not seem to be sufficient to answer all arising questions about the microstructure of such materials. In this thesis, microporous polymers from an abundant natural resource, betulin, will be presented. Betulin is a large-scale byproduct of the wood industry, and its content in birch bark can reach 30 wt.%. Based on its rigid structure, polymer networks with intrinsic microporosity could be synthesized and characterized. Apart from standard nitrogen and carbon dioxide sorption at 77 K and 273 K, respectively, gas sorption has been examined not only with various gases (hydrogen and argon) but also at various temperatures. Additional techniques such as X-ray scattering and xenon NMR have been utilized to enable insight into the microporous structure of the material. Starting from insoluble polymer networks with promising gas selectivities, soluble polyesters have been synthesized and processed to a cast film. Such materials are feasible for membrane applications in gas separation. Betulin as a starting compound for polyester synthesis has aided to prepare, and for the first time to thoroughly analyse a microporous polyester with respect to its pores and microstructure. It was established that nitrogen adsorption at 87 K can be a better method to solve the microstructure of the material. In addition to that, other betulin-based polymers such as polyurethanes and polyethylene glycol bioconjugates are presented. Altogether, it has been shown that as an abundant natural resource betulin is a suitable and cheap starting compound for some polymers with various potential applications. / Das Bestreben, ölbasierte Produkte durch nachwachsende Rohstoffe zu ersetzen, hat dazu geführt, dass in immer größerer Zahl günstige, reichlich vorhandene Naturstoffe als Ausgangsstoffe für chemische Synthesen untersucht werden. In dieser Arbeit werden Polymere auf Basis von Betulin, einem aus Birkenrinde extrahierten Naturstoff, vorgestellt. Betulin ist zu 30 Gewichtsprozent in Birkenrinde enthalten. Da Betulin ein Nebenprodukt der Holzindustrie ist, ist es kostengünstig und sein Einsatz als Ausgangsstoff äußerst lukrativ. Die ersten Berichte über Betulin-basierte Polymere sind in den 1980er Jahren in Russland und Finnland erschienen, in den Ländern mit großen natürlichen Vorkommen an Birken. Betulin wurde in dieser Arbeit verwendet, um sogenannte mikroporöse Polymere herzustellen. Dies sind Stoffe mit Poren von molekularer Dimension. Mikroporöse Materialien sind wegen ihrer potentiellen Anwendung als Katalysatorträger und Gasseparationsmembranen hochinteressant. Die Klasse mikroporöser Polymere wurde durch die Synthese von unlöslichen Betulin-basierten Polyesternetzwerken erweitert. Außerdem gelang es, lösliche Polyester in Form dünner Filme herzustellen. Diese zeigten vielversprechende Ergebnisse in der Trennung von Stickstoff und Kohlendioxid und weisen somit Potential für die Nutzung als Membran auf. Dies könnte z. B. für Kohlendioxid-Reduzierung in Postcombustion-Verfahren interessant sein. Überdies wurde gezeigt, dass Stickstoffadsorption bei 77 K nicht ohne weiteres als Standardmethode für die Analyse von mikroporösen Materialien geeignet ist und dass die mikroporösen Materialien ferner durch Stickstoffadsorption bei 87 K und andere Gassorptionsmethoden bei verschiedenen Temperaturen zu charakterisieren sind. Diese Arbeit trägt zum besseren Verständnis mikroporöser Polymere bei.

Trimesoyl chloride (TMC) crosslinked poly(vinyl alcohol) (PVA) / chitosan (CS) membranes and synthetic polyimide membranes were prepared for pervaporation dehydration of isopropanol and gas separation. PVA membranes were interfacially crosslinked with different amounts of TMC/hexane, and the degree of crosslinking was characterized by Fourier Transform Infrared Spectroscopy - Attenuated Total Reflectance Spectroscopy (FTIR-ATR) and water uptake. The asymmetric structure of the PVA-TMC membranes was revealed by FTIR-ATR. Thermal analysis was performed to understand the pyrolysis mechanism, which was supposed to be a combination of elimination of water and/or trimesic acid followed by breakage of the main chain. Water permeation and pervaporation dehydration of isopropanol were conducted, and the results showed that PVA-3TMC had the best overall pervaporation properties among the four PVA-TMC membranes studied. Sorption properties and pervaporation behavior of the PVA-3TMC membrane were investigated. The effects of water/isopropanol on the polymer matrix and the possible change of the degree of crystallinity induced by the sorbed water were believed to account for the sorption properties. For water permeation and pervaporation dehydration of isopropanol in a heating-cooling cycle, the permeation flux did not change significantly, and the selectivity was improved by the formation of crystallites during the heating run. For pervaporation in the diluting and concentrating runs at 60 °C, there was no change in the membrane permeability. Chitosan membranes were interfacially crosslinked in TMC/hexane with different crosslinking time. The membrane with a higher degree of crosslinking showed a higher degree of swelling in water at room temperature. A two-stage thermal decomposition mechanism was proposed based on thermal analyses. Pure gas permeation was performed with CO2 and N2 at room temperature, and CS-TMC-2 showed the best performance, with a CO2 permeability of ~163 Barrer and a CO2/N2 permeability ratio of ~42. Pervaporation was carried out for dehydration of isopropanol with the unconditioned and conditioned membranes, and the CS-TMC-3 membrane showed the best pervaporation performance. Pervaporation and gas separation properties were affected by the crosslinking-induced relaxation and the mobility/packing properties of the CS-TMC matrices. 4,4'-(Hexafluoroisopropylidene) diphthalic anhydride (6FDA)-based and 2,2-bis[4-(3,4-dicarboxyphenoxy) phenyl]propane dianhydride (BPADA)-based copolyimides were synthesized from one-step high-temperature polymerization in m-cresol. Polymers were characterized with Gel Permeation Chromatography (GPC), FTIR, Nuclear Magnetic Resonance Spectroscopy (NMR), Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). Surface free energies and interfacial free energies were calculated from contact angles to characterize hydrophilicity of the polyimide membranes. Gas permeation properties of 6FDA-based copolyimide membranes were studied with N2, O2, H2, He and CO2, and pervaporation dehydration of isopropanol was performed with 6FDA-based and BPADA-based membranes. An empirical linear moiety contribution approach was proposed, and the moiety contribution factors were used to illustrate the effects of dianhydrides and diamines on permselectivities of the copolyimide membranes. Bulky side groups, flexibility of polymer main chains, structures of monomer moieties, and interactions between gas molecules and polymer chains were shown to affect gas permselectivities, while in pervaporation, both sorption and diffusion properties were affected by the interactions between penetrants and polymer matrices as well as the steric effects of monomer moieties.

Trimesoyl chloride (TMC) crosslinked poly(vinyl alcohol) (PVA) / chitosan (CS) membranes and synthetic polyimide membranes were prepared for pervaporation dehydration of isopropanol and gas separation. PVA membranes were interfacially crosslinked with different amounts of TMC/hexane, and the degree of crosslinking was characterized by Fourier Transform Infrared Spectroscopy - Attenuated Total Reflectance Spectroscopy (FTIR-ATR) and water uptake. The asymmetric structure of the PVA-TMC membranes was revealed by FTIR-ATR. Thermal analysis was performed to understand the pyrolysis mechanism, which was supposed to be a combination of elimination of water and/or trimesic acid followed by breakage of the main chain. Water permeation and pervaporation dehydration of isopropanol were conducted, and the results showed that PVA-3TMC had the best overall pervaporation properties among the four PVA-TMC membranes studied. Sorption properties and pervaporation behavior of the PVA-3TMC membrane were investigated. The effects of water/isopropanol on the polymer matrix and the possible change of the degree of crystallinity induced by the sorbed water were believed to account for the sorption properties. For water permeation and pervaporation dehydration of isopropanol in a heating-cooling cycle, the permeation flux did not change significantly, and the selectivity was improved by the formation of crystallites during the heating run. For pervaporation in the diluting and concentrating runs at 60 °C, there was no change in the membrane permeability. Chitosan membranes were interfacially crosslinked in TMC/hexane with different crosslinking time. The membrane with a higher degree of crosslinking showed a higher degree of swelling in water at room temperature. A two-stage thermal decomposition mechanism was proposed based on thermal analyses. Pure gas permeation was performed with CO2 and N2 at room temperature, and CS-TMC-2 showed the best performance, with a CO2 permeability of ~163 Barrer and a CO2/N2 permeability ratio of ~42. Pervaporation was carried out for dehydration of isopropanol with the unconditioned and conditioned membranes, and the CS-TMC-3 membrane showed the best pervaporation performance. Pervaporation and gas separation properties were affected by the crosslinking-induced relaxation and the mobility/packing properties of the CS-TMC matrices. 4,4'-(Hexafluoroisopropylidene) diphthalic anhydride (6FDA)-based and 2,2-bis[4-(3,4-dicarboxyphenoxy) phenyl]propane dianhydride (BPADA)-based copolyimides were synthesized from one-step high-temperature polymerization in m-cresol. Polymers were characterized with Gel Permeation Chromatography (GPC), FTIR, Nuclear Magnetic Resonance Spectroscopy (NMR), Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). Surface free energies and interfacial free energies were calculated from contact angles to characterize hydrophilicity of the polyimide membranes. Gas permeation properties of 6FDA-based copolyimide membranes were studied with N2, O2, H2, He and CO2, and pervaporation dehydration of isopropanol was performed with 6FDA-based and BPADA-based membranes. An empirical linear moiety contribution approach was proposed, and the moiety contribution factors were used to illustrate the effects of dianhydrides and diamines on permselectivities of the copolyimide membranes. Bulky side groups, flexibility of polymer main chains, structures of monomer moieties, and interactions between gas molecules and polymer chains were shown to affect gas permselectivities, while in pervaporation, both sorption and diffusion properties were affected by the interactions between penetrants and polymer matrices as well as the steric effects of monomer moieties.

Poly(ether-b-amide) (Pebax® grade 1074) is a waterproof breathable block copolymer containing soft poly(ethylene oxide) and rigid polyamide 12 segments. Its intrinsic gas permeabilities to nitrogen, oxygen, methane, helium, hydrogen, and carbon dioxide were tested under different feed pressures (0.3 – 2.5 MPa) and temperatures (20 – 80 °C). This helps to obtain a comprehensive understanding of the polymer, because prior work reported in the literature addressed only a few gases and used inconsistent membrane preparation and test methods. Relatively high polar (or quadrupolar)/nonpolar gas selectivity were observed. CO2/N2 selectivity was demonstrated to be as high as 105±0.4 in Pebax®1074, with CO2 permeability coefficient of approximately 180±1 Barrer at room temperature. Additionally, the effects of solvent used in membrane preparation, heat treatment, membrane thickness, and polymer solution concentration on the membrane permeability were evaluated. Pebax® is a highly breathable material, thus its application as breathable chemically-resistant protective clothing was studied. Dimethyl methylphosphonate (DMMP) – a sarin simulant – was selected as the challenge agent. The liquid pervaporation of pure water (simulating perspiration) and pure DMMP were measured for Pebax®1074, Pebax®2533, nitrile, latex, poly(vinyl chloride), low density polyethylene, silicone, and silicone-polycarbonate copolymer under pervaporation mode. Pebax®1074 was not only the most water permeable material but also the most selective of all the tested materials for water/DMMP – making it a very promising material for this application.