Microporous catalysts belong to a class of materials that exhibit pore networks in the molecular dimension, that is, channel diameters less than 2 nm. The industrially most important microporous catalysts are zeolites, which are crystalline aluminosilicates and consist of interlinked alumina (AlO4) and silica (SiO4) tetrahedra forming pores and cavities of molecular dimensions. Zeolites can act as very strong solid acids and function as heterogeneous catalysts in various industrial processes used to obtain polyethylene terephthalate (PET) or polyvinyl chloride (PVC). They are crucial for products with a significant market demand such as plastics used in bottles, packaging materials and household consumable goods as well as for coatings of pharmaceutical pills and detergents. Recently, zeolites have been found to have increased applications in aqueous and biphasic reactions that use reactants derived from biomass to arrive at petrochemical products. Thus, surface acidity in zeolites is crucial to understand to tune parameters such as activity and selectivity of zeolite catalysts to optimize product distributions. The objective of this dissertation was to validate the use of non-invasive nuclear magnetic resonance (NMR) techniques to characterise surface acidity in zeolites by benchmarking the NMR results to various more established zeolite characterisation techniques, such as Fourier transform infrared (FTIR) spectroscopy and temperature-programmed desorption (TPD). Furthermore, the use of the tapered element oscillating microbalance (TEOM) to characterise internal and external acidity in zeolites was explored. IR and TPD techniques were used to assess important acidity parameters such as type, number, location and strength of acid sites of ZSM-5 zeolites with varying silica-alumina ratio (SAR = SiO2/Al2O3). The use of NMR relaxation time analysis of pyridine adsorbed in ZSM-5 was then explored as a model system to study surface acidity in microporous materials. Correlation with pyridine TPD results suggested that NMR relaxation time analysis probes the effective strength of pyridine adsorption sites, which varies with SAR. NMR relaxation time analysis was then further shown to be applicable to characterise non-acidic surface properties such as the hydrophilic and hydrophobic surface character. Lastly, the NMR techniques developed at high magnetic field strength (300 MHz) were transferred to a portable, low-cost benchtop low-field (43 MHz) magnet and shown to be applicable for base probe molecules other than pyridine, that is, ammonia (NH3) as well as zeolite framework types other than ZSM-5, that is, chabazite (CHA).

The primary aim of this thesis is to investigate and quantify the self-diffusion processes of gaseous molecules adsorbed in industrially relevant microporous zeolite materials using Pulsed Field Gradient Nuclear Magnetic Resonance (PFG NMR). The main body of this work involves the use of weakly adsorbing hydrocarbon gases (CH4, C2H6 and C3H¬8) adsorbed in a large pore β-zeolite structure. This thesis describes the development of a solely PFG NMR based technique for measuring the molecular displacements of these species at varying length-scales. This enabled the characterisation of self-diffusion regimes across zeolite beds and within individual zeolite crystallites. The characterisation of self-diffusion processes within single zeolite crystallites was critical with respect to accounting for quantitative discrepancies reported in the literature between PFG NMR and alternative measurement techniques. This approach also revealed that the transitions in the Gaussian probability distributions of the molecular displacements in the aforementioned self-diffusion regimes could be recorded by varying the experimental time-scale for observing molecular motion. This technique was extended to characterise the self-diffusion processes of the aforementioned hydrocarbons in small (≤ 1 μm) and large (≥ 15 μm) zeolite crystallites to investigate the dependence of this technique on zeolite geometry. It was found that the self-diffusion coefficients within single crystallites were in good agreement with one another, despite their differing crystallite geometries. This technique was subsequently used to study the self-diffusion behaviour of two-component hydrocarbon gaseous mixtures with differing sorption properties co-adsorbed in β-zeolite. Excellent chemical shift resolution was obtained for chemically similar species using NMR spectroscopy, relaxometry and diffusometry without the use of Magic Angle Spinning (MAS). This connoted that conventional PFG NMR is capable of precisely characterising individual species in real world multi-component systems. This thesis also describes the self-diffusion of ammonia in small pore chabazite structures, which are typically used in Selective Catalytic Reduction (SCR) processes. It was found that the self-diffusion coefficient of this strongly adsorbing species increased with molecular loading up to a certain point. This peculiar behaviour implied a strong concentration and inter-molecular dependence within the zeolite structure. Lastly, the techniques which were developed at high magnetic field strengths (300 MHz) were transferred to a lower field strength (43 MHz) benchtop spectrometer at the Johnson Matthey Technology Centre (JMTC). This describes the first characterisation of mass transport behaviour of weakly interacting sorbates in zeolites using a portable spectrometer. This presents an excellent opportunity for future off-line molecular displacement measurements to be made for complex and real-world systems in a matter of minutes.

Thesis (PhD)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: We investigate a model system for particle diffusion in elastically coupled one-dimensional narrow channels. The elastic coupling of the channels is such that channels mutually affect the stochastic dynamics of particles. This kind of constrained and coupled stochastic diffusion may occur in supramolecular lattices where pore occupancy by guest particles may induce a reversible mechanical deformation of the lattice hence, affecting particle evolution in neighbouring pores. The model is explored first for out-of-equilibrium conditions, where we look mainly at the kinetic properties of the system, and thereafter under equilibrium conditions, where we try to understand the nature of dynamic correlation within the coupled channel system. For an out-of-equilibrium version of the model the focus is placed on the steady state behaviour of the two elastically coupled finite channels. The channels are kept in contact with particle reservoirs at the boundaries. Three current-density regimes of different distinct behaviour are identified using a simulation experiment. The sensitivity of the system mean occupancy profile and the steady state particle flux to small and large coupling parameter strength are explored. We find that, for small coupling strength, the system steady state profile and flux behaviour can be approximated by a simple mean field theory ignoring density-density correlations. We present the analytic description of the system using a cellular automaton formalism and then we generalize the theory for a multi-coupled channel system using a hopping particle dynamics approach. For small coupling parameter values, the analytic results are confirmed by the stochastic simulation. From the equilibrium perspective, we model the elastically coupled channel system as a system of infinite narrow channels having a uniform guest particle occupancy and we calculate density fluctuation correlation functions. The elastic coupling between channels is modelled as short range interacting potential and the particle evolution is modelled through Langevin dynamics. The dynamics are cast into the functional integral formalism expressed in terms of the collective particle number density, current density and the associated density response fields. The resulting generating functional takes these fields into consideration within the random phase approximation (RPA) up to second order. For a short range interaction potential, we uncover the behaviour of the system by looking at the influence of the inter-channel interaction strength on the dynamic density-density correlation functions. We conclude that the system long time limit effective friction coefficient is reduced with increase in the coupling parameter values while the strength of thermal forces for the effective system becomes renormalized. We also find out that the RPA breaks down under certain conditions, signalling a transition to a behaviour that is no longer characterised by a homogeneous density. The work presented here provides the beginnings for microscopic insights into the filling, filtering and storage processes for which certain types of microporous materials can be utilised. / AFRIKAANSE OPSOMMING: Ons ondersoek ’n modelstelsel vir die diffusie van deeltjies in elasties gekoppelde, eendimensionele nou kanale. Die elastiese koppeling is sodanig dat die stogastiese dinamika wedersyds be¨ınvloed word. Hierdie gekoppelde en aan dwangvoorwaardes onderhewig diffusie kan in supermolekulˆere roosters gebeur waar die besetting van holtes deur deeltjies ’n omkeerbare meganiese vervorming van die kristalrooster kan veroorsaak en sodoende die tydontwikkeling in ’n aangrensende porie be¨ınvloed. Die model word eers vir nie-ewewig toestande ondersoek, waar ons hoofsaaklik die kinetiese eienskappe van die stelsel beskou, en daarna word dit vir ewewig ondersoek, waar ons die aard van die dinamiese korrelasie binne die gekoppelde kanaalstelsel probeer verstaan. Vir die nie-ekwilibrium weergawe van die model word die fokus op die gedrag van twee gekoppelde en eindige kanale se bestendige toestand gerig. Die porie¨e bly aan hulle eindpunte in kontak met reservoirs van deeltjies. Daar word drie deeltjiestroom-digtheid gebiede ge¨ıdentifiseer met behulp van ’n simulasieeksperiment. Die sensitiewiteit van die stelsel se gemiddelde deeltjiebesettingsprofiel en die deeltjievloed in ’n bestendige toestand is ondersoek vir groot en klein koppelingsparameters. Vir klein koppelingsterkte vind ons dat die stelsel se bestendige toestand deeltjiebesettingspofiel en deeltjievloed deur ’n eenvoudige gemiddelde-veld teorie beskryf kan word, waar digtheid-degtheids korrelasies verontagsaam kan word. Ons bied die analitiese beskrywing aan vir die gekoppelde stelsel deur van ’n sellulˆere outomaat-formalisme gebruik te maak, en om dan die teorie te veralgemeen vir ’n stelsel bestaande uit vele aanmekaar gekoppelde porie¨e ,deur gebruik te maak van ’n formalisme waarin deeltjies tussen holtes hop. Die analtiese resultate word vir kleine waardes van die koppelingsparameter deur ’n rekenaarsimulasie bevestig. Vir die ekwilibrium gesigspunt modelleer ons die gekoppelde stelsel van kanale as oneindig nou, met ’n homogene verdeling van die deeeltjiebesetting en ons bereken digtheids-korrelasiefunksies. Die elastiese vebinding tussen porie¨e word deur ’n kortrykwydte potensiaal gemodelleer en die deeltjies se dinamika met behulp van Langevindinamika. Die dinamika word met behulp van die funksionaal integraalformalisme uitgedruk in terme van die deeltjiegetaldigtheid-, stroomdigtheid- en meegaande antwoordvelde. Die resulterende genererende funksionaal neem hierdie hoeveelhede tot tweede order binne die “random field approximation” (RPA). Vir ’n potensiaal met kort rykwydte, ondersoek ons die stelsel se gedrag deur die dinamiese digtheid-digtheidskorrelasie te ondersoek. Ons lei af dat die stelsel se langtyd effektiewe wrywingsko¨effisi¨ent afneem met die toename in die koppelingsparameter se waardes terwyl die sterkte van die termiese kragte vir die effektiewe stelsel renormeer word. Ons vind ook dat die RPA onder sekere omstandighede sy geldigheid verloor, wat ’n oorgang kan beteken wat nie meer deur ’n homogene digtheid beskryf kan word nie. Die werk wat hier aangebied word dui die eerste stappe aan vir hoe mikroskopiese insigte vir vul-, filter- en stoorprosesse vir sekere tipes mikroporeuse materiale gebruik kan word.

Conventionally, crystalline microporous materials such as zeolites and metal-organic frameworks (MOFs) are synthesized through the hydrothermal route or the trial-and-error approach. Other synthetic strategies may lead to the synthesis of microporous materials with new architectures or interesting properties. The general aim of this thesis is to investigate some new synthetic routes towards crystalline microporous materials. A top-down and post-synthesis method is reported in Chapter 4. Some zeolites are built up by layers and double-4-ring pillars. Germanium is preferentially located in the double-4-ring sites of a zeolite framework and is hydrolytically unstable. The idea of the top-down method is to disassemble these zeolites to the layer structures by dissolving the Ge-containing pillars and reassemble them to a new framework. This method is applied to the germanosilicate IWW and ITH zeolites for the first time. The effects of framework chemical compositions, Ge distributions and disassembling conditions on the top-down treatment process are investigated. The products obtained from the top-down treatment are characterised. An ionic liquid assisted strategy for the synthesis of zeolites is described in Chapter 5. The ionic liquid assisted strategy is a solvent free reaction. The raw materials are transformed to zeolites through a solid state reaction. The ionic liquids are first used as structure-directing agents (SDAs) in this solvent free reaction to replace the expensive quaternary ammonium hydroxide. A TON zeolite is synthesized using 1-ethyl-3-methylimidazolium bromide as the SDA. Moreover, the ionic liquid assisted strategy is considered as a “green chemistry” synthetic route due to the high yield of the zeolites and the minor production of waste water. Many aluminophosphates have been successfully synthesized through ionothermal routes. Most of them are synthesized using 1-alkyl-3-methylimidazolium based ionic liquids. A new ionic liquid, 1-(2-hydroxyl-ethyl)-3-methylimidazolium chloride ([HOEmim]Cl), is prepared and used for the ionothermal synthesis of aluminophosphate materials. A zeolite analogue with the CHA framework has been synthesized. At high synthetic temperatures, the products are large single crystals. The structures of the framework and the SDA are investigated by single crystal diffraction and other characterisation methods. Flexible MOF materials are usually synthesized by a trial-and-error approach. Recently a flexible MOF compound was synthesized using 5-sulfoisophthalic acid (SIP) as the ligand. It was proposed the sulfonate is weakly coordinated to the metal, which brings flexibility to the compound, and the carboxylate groups keep the framework intact. 2-sulfoterephthalic acid (STP) which also contains one sulfonate group and two carboxylate groups is believed to be an alternative ligand for the targeted synthesis of flexible MOFs. In Chapter 7, a MOF compound is synthesized using STP and 4, 4'-bipyridine (Bpy) as ligands to validate the proposed strategy can be generalized. Variable temperature single crystal diffraction analysis solves the structure and reveals a reversible structure transformation upon dehydration and rehydration.

L'exploitation des ressources non conventionnelles de roches mères telles que les schistes gazeux contribue de plus en plus au mix énergétique mondial en raison de la raréfaction des ressources conventionnelles. L'exploitabilité de ces réservoirs repose principalement sur la qualité, la teneur et le type de matière organique qu'ils contiennent. En effet, il est admis que plus de la moitié des hydrocarbures présents dans les schistes sont adsorbés dans la matière organique solide, appelée kérogène, dont la structure est microporeuse et amorphe, et qui représente à la fois la source et le réservoir d'hydrocarbures. Le kérogène se trouve sous forme dispersée dans la matière minérale et représente environ 5% de la masse totale de la roche. La compréhension des propriétés de transport des fluides à l'échelle des micropores, en particulier leur dépendance aux conditions thermodynamiques et aux propriétés structurelles du matériau, revêt une importance cruciale pour l'optimisation de la récupération de ces ressources. De ce point de vue, l'objectif principal de cette thèse vise à bien documenter les propriétés de transport des hydrocarbures à travers les kérogènes et améliorer leur description théorique. Pour ce faire, nous avons fait le choix d'étudier les propriétés de transport des fluides à travers ces matériaux en utilisant une approche numérique basée sur des simulations moléculaires de type dynamique moléculaire et Monte Carlo, conduites sur des modèles moléculaires de kérogène mature et sur un système modèle simplifié. Ceci nous a permis d’explorer les mécanismes de transport à une échelle où l'observation expérimentale est difficile, voire impossible, et également de nous situer dans des conditions thermodynamiques supercritiques (haute pression, haute température) caractéristiques des réservoirs de gaz de schiste. La première partie de ce travail a consisté à étudier les propriétés de transport et d'adsorption des fluides purs dans des structures de kérogène mature reconstruites par simulations moléculaires. Ensuite, la dépendance des propriétés de transport aux variations des conditions thermodynamiques (température à gradient de pression fixe) ainsi qu'à la distribution de tailles de pores a été étudiée. Concernant le deuxième objectif, afin de mieux comprendre et modéliser la diffusion des fluides à l'échelle d'une constriction microporeuse entre deux pores, nous avons étudié un système modèle constitué d'une seule fente microporeuse formée dans un solide mono-couche. L'étude a consisté à simuler la diffusion de transport d'un fluide à travers la constriction en variant les paramètres géométriques (rapport d’aspect entre la largeur du pore et la taille des molécules diffusantes) et thermodynamiques (température, chargement en fluide). Ces résultats de simulations ont été comparés aux prédictions d'un modèle théorique, fondé sur la théorie cinétique des gaz et la mécanique statistique classique, qui prend en compte l'effet de la température sur la porosité accessible ainsi que l'effet du chargement en fluide à l'entrée du seuil de pore. Un bon accord a été observé entre les valeurs simulées des coefficients de diffusion et les prédictions du modèle proposé. Ce système a ainsi contribué à la compréhension des phénomènes de tamisage moléculaire survenant lors du franchissement d'une constriction microporeuse, inhérents au transport de fluides dans les matériaux microporeux tels que le kérogène. / The share of unconventional resources in the global energy mix is expected to rise because of the shortage of conventional fossil resources. The major part of these unconventional resources are found in source rocks such as gas shales. The profitability of shale reservoirs strongly depends on the quality, type and content of organic matter contained in the rock. Indeed, it is admitted that more than half of the hydrocarbons stored in the shale are adsorbed in the solid organic matter, the so-called kerogen. The latter exhibits a microporous amorphous structure, and acts as both the source and the reservoir of hydrocarbons. Kerogen is finely dispersed in the mineral matrix and represents about 5% of the total mass of the rock. The understanding of the transport of fluids at the microporous scale is of crucial importance for optimizing the recovery of these resources. More specifically, how the structural properties of the microporous material and thermodynamic conditions influence its transport properties is an open question. In this regard, the main objective of this thesis is to document the transport properties of hydrocarbons through kerogens and to improve their theoretical description. To do so, we opted for a numerical approach based on molecular simulations of molecular dynamics and Monte Carlo codes performed on molecular models of mature kerogen, as well as simplified model systems. We thus explored transport mechanisms at the molecular scale, at which experimental observations are difficult, if not impossible. Supercritical thermodynamic conditions (high pressure, high temperature) were considered, which are characteristic of shale gas reservoirs. The first part of this work has consisted in studying the transport and adsorption properties of pure fluids in mature kerogen structures reconstructed by molecular simulations. We studied the dependence of the transport properties on the variations of the thermodynamic conditions (pressure gradient at a fixed temperature) as well as the influence of the pore size distribution. In order to better understand and describe the diffusion of fluids at the scale of a microporous constriction between two pores, the second objective of this thesis focused on a model system, which consisted of a single-layer solid with a slit aperture of controllable width. We simulated the diffusional transport of simple fluids through the constriction for various geometrical parameters (aspect ratio between the width of the pore and the size of the diffusing molecules) and thermodynamic conditions (temperature, fluid loading). These simulations results have been compared to the predictions of a theoretical model, based on the kinetic theory and classical statistical mechanics, which accounts for the effect of temperature on the accessible porosity and the effect of fluid loading at the entrance of the pore. A good agreement was observed between the simulated values of the diffusion coefficients and the predictions of the proposed model. The investigation of this simplified system helped in understanding the molecular sieving phenomena inherent to the transport of fluids in microporous materials such as kerogen.

Gegenstand der Arbeit ist die PFG NMR (nuclear magnetic resonance with pulsed field gradients), wobei speziell die apparativen und experimentellen Bedingungen untersucht werden, welche sich durch die Verwendung ultra-hoher gepulster magnetischer Feldgradienten von bis zu 35T/m ergeben. Motiv für die Arbeit ist die Untersuchung von Diffusionserscheinungen in mikroporösen Wirtssystemen mit inneren magnetischen Feldgradienten oder/und kurzen T2-Relaxationzeiten. Nach Zusammenstellung der notwendigen Werkzeuge zur mathematischen Beschreibung von PFG NMR-Experimenten werden die aus der Literatur bekannten Impulssequenzen kritisch untersucht und durch eigene Weiterentwicklungen ergänzt. Für wichtige PFG NMR-Impulssequenzen wird eine verallgemeinerte Schreibweise vorgestellt und auf beliebige Formen der gepulsten magnetischen Feldgradienten ausgedehnt. Weiterhin werden Störeinflüsse auf das PFG NMR-Experiment untersucht und zunächst in allgemeiner Form Möglichkeiten zu deren Beseitigung bzw. Unterdrückung dargestellt. Die so gewonnenen Erkenntnisse fanden konkrete Anwendung bei der Konzeption und dem Bau des PFG NMR-Spektrometers Fegris 400 NT. Dieses Gerät wird, soweit es den Gegenstand der Arbeit berührt, ebenfalls beschrieben und in der Anlage dokumentiert. Abschließend sind einige Untersuchungen, die mit dem Fegris 400 NT durchgeführt wurden und in der dargestellten Form erst mit diesem Gerät möglich waren, kurz skizziert, wobei für weitergehende Informationen auf die entsprechenden Veröffentlichungen verwiesen wird.

Made available in DSpace on 2014-12-17T14:06:51Z (GMT). No. of bitstreams: 1 ThiagoC.pdf: 1828528 bytes, checksum: f789d02379757a5c26566b00a092e4c1 (MD5) Previous issue date: 2009-02-03 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / heterogeneous catalyst such as a silicoaluminophosphate, molecular sieve with AEL (Aluminophosphate eleven) structure such as SAPO-11, was synthesized through the hydrothermal method starting from silica, pseudoboehmite, orthophosphoric acid (85%) and water, in the presence of a di-isopropylamine organic template. For the preparation of SAPO-11 in a dry basis it was used as reactants: DIPA; H3PO4; SiO4; Pseudoboehmite and distilled water. The crystallization process occurred when the reactive hydrogel was charged into a vessel and autoclaved at 200?C for a period of 72 hours under autogeneous pressure. The obtained material was washed, dried and calcined to remove the molecular sieves of DIPA. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared spectroscopy (FT-IR), nitrogen adsorption (BET) and thermal analysis (TG/DTG). The acidic properties were determined using adsorption of nbutylamine followed by programmed thermodessorption. This method revealed that SAPO-11 shows an acidity that ranges from weak to moderate. However, a small quantity of strong acid sites could be detected there. The deactivation of the catalysts was conducted by artificial coking followed by the cracking of the n-hexane in a fixed bed with a continuous flow micro-reactor coupled on line to a gas chromatograph. The main products obtained were: ethane, propane, isobutene, n-butane, n-pentane and isopentane. The Vyazovkin (model-free) kinetics method was used to determine the regeneration and removal of the coke / Um catalisador heterog?neo do tipo silicoaluminofosfato, peneira molecular com estrutura AEL (Aluminophosphate eleven), como o SAPO-11, foi sintetizado pelo m?todo hidrot?rmico a partir de alumina hidratada (pseudobohemita), ?cido fosf?rico 85%, s?lica gel, ?gua e di-isopropilamina (DIPA) usada como direcionador estrutural org?nico. Para a prepara??o de SAPO-11 em base seca foram necess?rias como reagentes: DIPA; H3PO4:; SiO4; Pseudoboehmita e ?gua destilada. O processo de cristaliza??o ocorreu ? temperatura de 200 0C durante 72 h, quando foi poss?vel obter a fase pura para o SAPO-11. O material obtido foi lavado com ?gua deionizada, seco e calcinado para remover as mol?culas do direcionador. Posteriormente a amostra foi caracterizada por difra??o de raios-X (DRX), microscopia eletr?nica de varredura (MEV), espectroscopia de absor??o na regi?o do infravermelho (FT-IR), adsor??o de nitrog?nio (BET) e an?lise t?rmica via TG/DTG. As propriedades ?cidas foram determinadas usando adsor??o de n-butilamina seguida de termodessor??o programada. Este m?todo revelou que a amostra SAPO-11 apresenta uma acidez tipicamente fraca a moderada. Entretanto, uma pequena quantidade de s?tios ?cidos fortes foi detectada. A desativa??o dos catalisadores foi conduzida pelo coqueamento artificial da amostra, seguida da rea??o de craqueamento do n-hexano em um microrreator catal?tico de leito fixo com fluxo cont?nuo acoplado em linha com um cromat?grafo a g?s. Como principais produtos foram obtidos: etano, propano, isobutano, n-butano,e n-pentano, isopentano. Para determinar a regenera??o e a remo??o do coque foi aplicado o m?todo cin?tico Vyazovkin (Model Free Kinetics)

abstract: Membrane-based gas separation is promising for efficient propylene/propane (C3H6/C3H8) separation with low energy consumption and minimum environment impact. Two microporous inorganic membrane candidates, MFI-type zeolite membrane and carbon molecular sieve membrane (CMS) have demonstrated excellent thermal and chemical stability. Application of these membranes into C3H6/C3H8 separation has not been well investigated. This dissertation presents fundamental studies on membrane synthesis, characterization and C3H6/C3H8 separation properties of MFI zeolite membrane and CMS membrane. MFI zeolite membranes were synthesized on α-alumina supports by secondary growth method. Novel positron annihilation spectroscopy (PAS) techniques were used to non-destructively characterize the pore structure of these membranes. PAS reveals a bimodal pore structure consisting of intracrystalline zeolitic micropores of ~0.6 nm in diameter and irregular intercrystalline micropores of 1.4 to 1.8 nm in size for the membranes. The template-free synthesized membrane exhibited a high permeance but a low selectivity in C3H6/C3H8 mixture separation. CMS membranes were synthesized by coating/pyrolysis method on mesoporous γ-alumina support. Such supports allow coating of thin, high-quality polymer films and subsequent CMS membranes with no infiltration into support pores. The CMS membranes show strong molecular sieving effect, offering a high C3H6/C3H8 mixture selectivity of ~30. Reduction in membrane thickness from 500 nm to 300 nm causes an increase in C3H8 permeance and He/N2 selectivity, but a decrease in the permeance of He, N2 and C3H6 and C3H6/C3H8 selectivity. This can be explained by the thickness dependent chain mobility of the polymer film resulting in final carbon membrane of reduced pore size with different effects on transport of gas of different sizes, including possible closure of C3H6-accessible micropores. CMS membranes demonstrate excellent C3H6/C3H8 separation performance over a wide range of feed pressure, composition and operation temperature. No plasticization was observed at a feed pressure up to 100 psi. The permeation and separation is mainly controlled by diffusion instead of adsorption. CMS membrane experienced a decline in permeance, and an increase in selectivity over time under on-stream C3H6/C3H8 separation. This aging behavior is due to the reduction in effective pore size and porosity caused by oxygen chemisorption and physical aging of the membrane structure. / Dissertation/Thesis / Doctoral Dissertation Materials Science and Engineering 2015

The anthropogenic carbon dioxide (CO2) emission into the atmosphere, mainly through the combustion of fossil fuels, has resulted in a balance disturbance of the carbon cycle. Overwhelming scientific evidence proves that the escalating level of atmospheric CO2 is deemed as the main culprit for global warming and climate change. It is thus imperative to develop viable CO2 capture and sequestration (CCS) technologies to reduce CO2 emissions, which is also essential to avoid the potential devastating effects in future. The drawbacks of energy-cost, corrosion and inefficiency for amine-based wet-scrubbing systems which are currently used in industry, have prompted the exploration of alternative approaches for CCS. Extensive efforts have been dedicated to the development of functional porous materials, such as activated carbons, zeolites, porous organic polymers, and metal-organic frameworks (MOFs) to capture CO2. However, these adsorbents are limited by either poor selectivity for CO2 separation from gas mixtures or low CO2 adsorption capacity. Therefore, it is still highly demanding to design next-generation adsorbent materials fulfilling the requirements of high CO2 selectivity and enough CO2 capacity, as well as high water/moisture stability under practical conditions. Metal-organic frameworks (MOFs) have been positioned at the forefront of this area as a promising type of candidate amongst various porous materials. This is triggered by the modularity and functionality of pore size, pore walls and inner surface of MOFs by use of crystal engineering approaches. In this work, several effective strategies, such as incorporating 1,2,3-triazole groups as moderate Lewis base centers into MOFs and employing flexible azamacrocycle-based ligands to build MOFs, demonstrate to be promising ways to enhance CO2 uptake capacity and CO2 separation ability of porous MOFs. It is revealed through in-depth studies on counter-intuitive experimental observations that the local electric field favours more than the richness of exposed nitrogen atoms for the interactions between MOFs and CO2 molecules, which provides a new perspective for future design of new MOFs and other types of porous materials for CO2 capture. Meanwhile, to address the water/moisture stability issue of MOFs, remote stabilization of copper paddlewheel clusters is achieved by strengthening the bonding between organic ligands and triangular inorganic copper trimers, which in turn enhances the stability of the whole MOF network and provides a better understanding of the mechanism promoting prospective suitable MOFs with enhanced water stability. In contrast with CO2 capture by sorbent materials, the chemical transformation of the captured CO2 into value-added products represents an alternative which is attractive and sustainable, and has been of escalating interest. The nanospace within MOFs not only provides the inner porosity for CO2 capture, but also engenders accessible room for substrate molecules for catalytic purpose. It is demonstrated that high catalytic efficiency for chemical fixation of CO2 into cyclic carbonates under ambient conditions is achieved on MOF-based nanoreactors featuring a high-density of well-oriented Lewis active sites. Furthermore, described for the first time is that CO2 can be successfully inserted into aryl C-H bonds of a MOF to generate carboxylate groups. This proof-of-concept study contributes a different perspective to the current landscape of CO2 capture and transformation. In closing, the overarching goal of this work is not only to seek efficient MOF adsorbents for CO2 capture, but also to present a new yet attractive scenario of CO2 utilization on MOF platforms.

Theoretical investigation of microporous materials for adsorption and catalysis Microporous materials are defined by a presence of pores with diameter smaller than 2 nm. They comprise a large variety of materials from amorphous materials to very well defined crystalline materials like zeolites or metal organic frameworks. Microporous materials are industrially very important group of materials used for adsorption, gas capture, molecular sieving, or heterogeneous catalysis. Zeolites are by far the most important group of microporous materials due to their use as catalysts for the petroleum cracking. One of the main limitations of the zeolite use in catalysis is their limited pore size. This obstacle can be solved by use of hierarchical zeolites with a secondary mesopore network which allows overcoming the diffusion problems. The aims of this study can be divided into two parts. In the first part, the structures of two-dimensional and hierarchical zeolites were investigated theoretically to identify the structure of new materials and to obtain reliable models to study the hierarchical zeolites. In the second part, the catalytic properties of several microporous materials were modelled to explain their experimental activity. The results of this thesis were used to identify the structure of a large...