Zeolite membranes are formed as a thin zeolitic layer on the supports. They are usually synthesized by hydrothermal methods in batch systems. In this study, MFI and SAPO-34 type zeolite membranes were produced on macroporous tubular alumina supports in a recirculating flow system at elevated temperatures for the first time in the literature. During the synthesis, the synthesis mixture is flown between the reservoir and the membrane module which includes the support material. The synthesis temperatures were 180&deg / C and 220&deg / C, and the corresponding system pressures were approximately 20 and 30 bars for MFI and SAPO-34, respectively. The CH4 and n-C4H10 single gas permeances were measured through MFI membranes and the performance of membranes was investigated in the separation of equimolar CH4/n-C4H10 mixtures. The best MFI membrane had a CH4 single gas permeance of 1.45x10-6 mol/m2-s-Pa and CH4/n-C4H10 ideal selectivity of 35 at 25oC. The membranes preferentially permeated n-C4H10 in the separation of mixtures. The n-C4H10/CH4 separation selectivity was 43.6 with a total permeance of approximately 0.8x10-6 mol/m2-s-Pa at 25oC. The ideal selectivities of CO2/CH4 of SAPO-34 membrane synthesized in stagnant medium were 227, and &gt / 1000 at 220 and 200oC, respectively. Formation of amorphous structure and the additional secondary phases (impurities) were observed on SAPO-34 membranes synthesized in recirculating flow system. The results showed that it is possible to produce SAPO-34 and high quality MFI membranes by a recirculating flow system operating at elevated temperature.

Inorganic porous materials are widely used in a number of applications, where is a need to functionalize and produce materials with a multiscale porosity. The first part of the thesis describes how a novel and facile powder processing approach, using pulsed current processing (PCP) or, as it is commonly called, spark plasma sintering (SPS), has been employed to produce mechanically stable, hierarchically porous bodies from different porous powders. Surfactant-templated mesoporous spheres were PCP-treated to yield meso/macro porous monoliths. The bimodal pore size can be tailored by choice of templating molecules in the aerosol-assisted synthesis process and by the particle size of the spheres. Diatomite powders were used to produce macro/macroporous monoliths. The densification behaviour of this inexpensive and renewable macroporous raw material was evaluated in detail, and an optimum temperature range was identified where the PCP process yields mechanically strong monoliths. Binder-less, hierarchically porous zeolite monoliths were produced from various zeolite powders, e.g. silicalite-1, ZSM-5 and zeolite Y. Line-broadening analysis of X-ray powder diffraction data by the Rietveld method and electron microscopy showed that the formation of strong interparticle bonds during the PCP process is associated with a local amorphization reaction that is induced by the high contact stress and temperature. Xylene isomerisation studies showed that binder-less ZSM-5 monoliths display a high catalytic selectivity. Direct (in-situ) nanoparticle functionalization of surfactant templated mesoporous silica particles has also been demonstrated. Pre-synthesized TiO2 nanoparticles were dispersed in a precursor solution, containing surfactant and silica source, and processed in an aerosol-generator to produce spherical nanoparticle-functionalized mesoporous particles.

La caolinita, constituyente principal del caolín, es una arcilla de fórmula 2SiO(2) Al(2).O(3).2H(2)O que da lugar a un producto de calcinación denominado metacaolinita, muy utilizado como materia prima en la síntesis de zeolitas de bajo contenido en SiO(2), como por ejemplo las zeolitas del grupo de la faujasita NaA, NaX y NaY (Breck, 1974). Aunque la producción de zeolita A para detergencia a partir de la metacaolinita ha sido ampliamente descrita en numerosas patentes y trabajos de investigación, el mecanismo de esta reacción se conoce desde hace muy pocos años. La síntesis de zeolitas del tipo X o Y ha sido también descrita, aunque con menos profusión, y su obtención a partir de la caolinita requiere una técnica más elaborada que ha sido escasamente descrita. La adición de una fuente externa de SiO(2) es la vía mejor conocida (Covián, 1991), aunque el proceso presenta una conversión baja y da lugar a productos de baja calidad con la consiguiente pérdida de valor en el mercado que ello supone. El ajuste de la razón SiO(2)/Al(2)O(3) por extracción de aluminio es un proceso concebible pero poco estudiado hasta la fecha. En otro orden de cosas, se han realizado numerosos esfuerzos por desarrollar procesos de obtención de aluminio a partir de fuentes diferentes de la bauxita como consecuencia de que su distribución en el mundo ha originado situaciones de potencial escasez. El caolín, por el contrario, se halla extensamente distribuido y es un mineral rico en aluminio por lo que se constituye en el sustituto por excelencia de la bauxita. Los procesos de obtención de aluminio a partir de caolín desarrollados han tenido como objetivo, consecuentemente, la maximización del rendimiento de las reacciones químicas implicadas, así como una optimización tecnológica y económica de los procesos que diera lugar a un producto con un coste competitivo. Los procesos de obtención de aluminio a partir de caolín mencionados arriba han sido analizados en el presente trabajo desde una perspectiva diferente: la de acondicionar el caolín a base de ajustar su razón SiO(2)/Al(2)O(3) en vez de agotar el aluminio presente en el mismo. Se han estudiado tres procesos diferentes no tan sólo en cuanto a la naturaleza de los reactivos empleados, sino también en las operaciones unitarias que comportan. Por orden de novedad creciente, se ha estudiado el ajuste empleando ácido clorhídrico en disolución acuosa, hidrógenosulfato de sodio y ácido sulfúrico. Los resultados obtenidos muestran que, si bien los tres métodos resultan viables, existen diferencias que es necesario tener en cuenta a la hora de escoger uno de ellos: mientras que la cinética de la reacción con HCl puede explicarse en base al modelo de nucleación de Hulbert y Huff (1970), modelo cinético de orden uno, las cinéticas de las reacciones con NaHSO(4) y H2SO(4) se explican adecuadamente mediante un modelo de núcleo decreciente (MND), un modelo cinético de orden cero. Esto, unido a las bajas energías de activación halladas, redunda en un mejor o peor control del punto final de la reacción: mientras que con el ácido clorhídrico se alcanzan valores elevados de la razón SiO(2)/Al(2)O(3), el punto final de la reacción es difícil de determinar. El hidrógenosulfato de sodio da lugar a valores inferiores de la razón SiO(2)/Al(2)O(3), pero muestra un comportamiento más favorable al apreciarse una detención paulatina de la reacción por resistencia a la difusión en la capa de cenizas. Este es también el caso del ácido sulfúrico, aunque en este reactivo juega un papel relevante la posibilidad de forzar su agotamiento corno método de detener la reacción. La calidad de los productos obtenidos mediante los tres reactivos varía sensiblemente obteniéndose productos de diferente composición química y diferentes características texturales dependiendo no sólo del proceso escogido sino también de las condiciones de operación. Es interesante hacer aquí mención a los contenidos en hierro y titanio, que dan coloración al producto final, pues existen diferencias notables en los productos obtenidos mediante un procedimiento u otro. Aunque existen numerosos procesos descritos para la separación de los minerales de hierro y titanio presentes en el caolín, poca cosa se puede hacer cuando hierro y titanio se hallan constituyendo la estructura cristalina de la caolinita misma. El proceso de ajuste de la razón SiO(2)/Al(2)O(3) brinda una oportunidad de rebajar los contenidos en estas especies dando lugar a productos de mayor valor final. Con el fin de comprender mejor las reacciones del caolín con hidrógenosulfato de sodio y con ácido sulfúrico se presenta un estudio acerca del mecanismo de reacción por el cual cursan las reacciones con cada uno de estos reactivos. Los resultados obtenidos se comparan con los hallados para la reacción con ácido clorhídrico. Una vez conseguido el ajuste de la razón SiO(2)/Al(2)O(3) por reacción con los tres agentes mencionados, se muestra que su reacción con hidróxido de sodio manifiesta diferencias importantes que cabrá analizar con el objeto de conocer en profundidad el proceso de obtención de zeolita X a partir de caolines con razón SiO(2)/Al(2)O(3) ajustada. La característica más relevante de estos materiales consiste en que dan lugar a una curva concentración - tiempo para Si y Al que es muy similar a la obtenida para caolines a los que se les ha añadido una fuente de silicio altamente soluble y también a la que presenta el caolín calcinado a temperaturas iguales o superiores a 900ºC. Los análisis por difracción de rayos X muestran, asimismo, que los sólidos en suspensión presentan un aspecto amorfo durante tiempos prolongados sin que se aprecien fases zeolíticas de ninguna clase, hecho que sugiere la viabilidad del empleo de caolines con razón SiO(2)/Al(2)O(3) ajustada mediante ácidos o sales inorgánicas en la obtención de zeolita X. Así lo muestran los ensayos realizados en este sentido, en los que se ha obtenido una zeolita X a partir de caolines tratados con ácido clorhídrico. Finalmente se proponen sendos esquemas de proceso para la obtención de zeolita X a partir de caolines tratados con los reactivos estudiados y se efectúan diversas consideraciones acerca de los mismos.

Detta examensarbete är en förundersökning till Glafos undersökning angående rening av glasbrukens processvatten från antimon med zeolit. Förundersökningen gick ut på att via experiment ta reda på hur mycket antimon som adsorberas av behandlad (för optimering: dels med NaNO3 och dels med NaCl) och obehandlad zeolit (porstorlek 0.4 nm). pH mättes och ställdes eftersom det har betydelse för adsorptionen, åtminstone vid väldigt lågt pH. När lösningarna hade filtrerats mättes den kvarvarande antimonhalten med atomabsorptionsspektrofotometri. Mätningarna visade att i genomsnitt 53 % av Sb-halten i lösningarna hade adsorberats av zeoliten. Förundersökningen visade att det inte blir någon adsorption då pH är väldigt lågt (under 1). Den visade också att när pH är över 4 verkar det inte ha någon betydelse om zeoliten är behandlad eller inte. Zeoliten bör behandlas med NaCl först i en tank med omrörning, sedan blandas i processvattnet (vars pH justerats till pH 4) i en tank eller bassäng och därefter filtreras. Tidsfaktorn för hur lång tid det tar för zeoliten att nå jämvikt och temperaturens inverkan bör även undersökas. / The aim of this diploma work is to study the removal of antimony from glassworks process water using zeolites. The experimental part of the studies were carried out to find the quantity of antimony adsorbed by the zeolite. The studies included treated (for optimization: partly with NaNO3 and partly with NaCl) and untreated zeolite. The pore size is 0.4 nm. pH was measured and adjusted because it is important for the antimony adsorption. When the solutions were filtrated the content of antimony left was measured with atomic absorption spectrophotometry. The measurements showed an average uptake of antimony by the zeolite of 53 %.The preinvestigation indicates that with a very low pH (below 1) there is no antimony adsorption. It also indicates that with pH above 4 it does not matter if the zeolite are treated or not. In further investigations the zeolite should be treated with NaCl in a stirred tank, then be mixed in the process water (pH is set to 4) in a tank or basin and then be filtrated. The time to reach equilibrium and the influence of temperature should also be investigated.

Die wachsende Weltbevölkerung und die stetigen Entwicklungen in der Industrie benötigen einerseits immer größere Mengen an Grundchemikalien und führen andererseits zu einem ständig steigenden Energiebedarf. Die Dissertation behandelt daher die Themen Zeolithe und Kathodenmaterialien, welche zwei aktuelle Forschungsschwerpunkte der chemischen Industrie darstellen. Der Fokus der Arbeit lag in der Steuerung der Partikelgröße durch die hydrothermale und mikrowellenunterstützte Kristallisation.

Developing new membrane morphologies and modifying the existing membrane materials are required to obtain membranes with improved gas separation performances. The incorporation of zeolites and low molecular-weight additives (LMWA) into polymers are investigated as alternatives to modify the permselective properties of polymer membranes. In this study, these two alternatives were applied together to improve the separation performance of a polymeric membrane. The polycarbonate (PC) chain characteristics was altered by incorporating p-nitroaniline (pNA) as a LMWA and the PC membrane morphology was modified by introducing zeolite 4A particles as fillers. For this purpose, pure PC and PC/pNA dense homogenous membranes, and PC/zeolite 4A and PC/pNA/zeolite 4A mixed matrix membranes (MMM) were prepared by solvent-evaporation method using dichloromethane as the solvent. The pNA and zeolite 4A concentrations in the casting solutions were changed between 1-5% (w/w) and 5-30% (w/w), respectively. Membranes were characterized by SEM, DSC, and single gas permeability measurements of N2, H2, O2, CH4 and CO2. They were also tested for their binary gas separation performances with CO2/CH4, CO2/N2 and H2/CH4 mixtures at different feed gas compositions. DSC analysis of the membranes showed that, incorporation of zeolite 4A particles into PC/pNA increased the glass transition temperatures, Tg, but incorporation of them to pure PC had no effect on the Tg, suggesting that pNA was a necessary agent for interaction between zeolite 4A and PC matrix. The ideal selectivities increased in the order of pure PC, PC/zeolite 4A MMMs and PC/pNA/zeolite 4A MMMs despite a loss in the permeabilities with respect to pure PC. A significant improvement was achieved in selectivities when the PC/pNA/zeolite 4A MMMs were prepared with pNA concentrations of 1 % and 2 % (w/w) and with a zeolite loading of 20 % (w/w). The H2/CH4 and CO2/CH4 selectivities of PC/pNA (1%)/zeolite 4A (20%) membrane were 121.3 and 51.8, respectively, which were three times higher than those of pure PC membrane. Binary gas separation performance of the membranes showed that separation selectivities of pure PC and PC/pNA homogenous membranes were nearly the same as the ideal selectivities regardless of the feed gas composition. On the other hand, for PC/zeolite 4A and PC/pNA/zeolite 4A MMMs, the separation selectivities were always lower than the respective ideal selectivities for all binary gas mixtures, and demonstrated a strong feed composition dependency indicating the importance of gas-membrane matrix interactions in MMMs. For CO2/CH4 binary gas mixture, when the CO2 concentration in the feed increased to 50 %, the selectivities decreased from 31.9 to 23.2 and 48.5 to 22.2 for PC/zeolite 4A (20%) and PC/pNA (2%)/zeolite 4A (20%) MMMs, respectively. In conclusion, high performance PC based MMMs were prepared by blending PC with small amounts of pNA and introducing zeolite 4A particles. The prepared membranes showed promising results to separate industrially important gas mixtures depending on the feed gas compositions.

The aim of this study was to determine the adsorption capacity of activated carbon and organo-zeolites for removal of pesticides in water. In order to prepare organo-zeolite, two kinds of cationic surfactants, namely, hexadecyltrimethyl ammonium bromide (HTAB) and dodecyltrimethyl ammonium bromide (DTAB) were used. Adsorption studies of cationic surfactant on zeolite were investigated in respect to initial concentration of cationic surfactant, time, and temperature. It has been found that the best fitted isotherm equation was Langmuir equation. The observed adsorption rates were found to be equal to the second order kinetic model. The activation energies of cationic surfactant adsorption was determined by using Arrhenius equation.

Aprotic solvents are organic solvents which do not easily react with a substance dissolved in it and they do not exchange protons despite of their high ion and polar group dissolving power. Therefore, this characteristic property makes aprotic solvents very suitable intermediates in many industries producing pharmaceuticals, textile auxiliaries, plasticizers, stabilizers, adhesives and ink. Dehydration of these mixtures and recirculation of valuable materials are substantial issues in industrial applications. The conventional method for recovery of aprotic solvents has been distillation, which requires excessive amount of energy to achieve desired recovery. Hydrophilic pervaporation, which is a membrane based dehydration method with low energy consumption, may become an alternative. Because of high dissolving power of aprotic solvents only inorganic membranes can be employed for this application. In this study three types of inorganic membranes (NaA zeolite, optimized silica and HybSi) were employed. Main objective of this studys to investigate effect of membrane type and various operationg parameters (feed composition at a range of 50-5% and temperature at a range of 50-100oC) on pervaporative dehydration of aprotic solvents / dimethylacetamide, dimethylformamide and n-methylpyrrolidone. During the experiments, feed samples were analyzed with Karl Fischer Titration Method / permeate samples were analyzed with Gas Chromatography. Experiments showed that proper dehydration of aqueous aprotic solvent mixtures was succeded with all three membranes investigated. In the target feed water content range (50 to 20%wt), permeate water contents were higher than 98%wt which was quite acceptable for all membranes. Moreover, NaA zeolite membrane performed higher fluxes than optimized silica and HybSi in composition range of 50 to 15% water at 50oC. It was also observed that HybSi membrane had higher fluxes and permeate water contents than optimized silica membrane for all solvents. On the other hand, the rates of decrease in permeate fluxes changed depending on the type of solvent for optimized silica and HybSi membranes. With both membranes, permeate flux of dimethylformamide decreased much slower than that of n-methylpyyrolidone. Furthermore, the results showed that permeate fluxes of HybSi membrane increased with increasing operation temperature due to the change of solvent activity in mixture. In addition, an Arrhenious type equation was used to describe changes in fluxes with changing temperature. It was also found that activation energy of water for diffusion through HybSi membrane was calculated as 8980 cal/mol.

A deposition - precipitation method was developed to produce magnesium hydroxide / zeolite 4A (Mg(OH)₂ - Z4A) nanocomposites at mild conditions and the effect of processing variables such as precursor concentration, type of base added, and synthesis time on the composition, size, and morphology of the nanocomposite were studied. It was determined that the precursor concentration, basicity, and synthesis time had a significant effect on the composition, size, and morphology of the deposited magnesium hydroxide (Mg(OH)₂) nanostructures. The properties of the Mg(OH)₂ - Z4A such as surface area, pore volume and composition were characterized. Mg(OH)₂ - Z4A samples and bare zeolite 4A were dispersed in Ultem® polymer to form a mixed matrix membrane. The thermal and mechanical properties of the resulting films were investigated. It was found that the addition of rigid bare zeolites into the polymer decreased the mechanical properties of the polymer composite. However, some of these adverse effects were mitigated in the polymer composite loaded with Mg(OH)₂ - Z4A samples. Isotherms for the adsorption of Mg(OH)₂ petals on zeolite 4A were measured in order to determine the optimum conditions for the formation of magnesium hydroxide / zeolite 4A nanocomposites at ambient conditions. The loading of the Mg(OH)₂ can be determined from the adsorption isotherms and it was also found that the adsorption of Mg(OH)₂ on zeolite A occurs via 3 mechanisms: ion exchange, surface adsorption of Mg²⁺ ions, and surface precipitation of Mg(OH)₂. Without the addition of ammonium hydroxide, the predominant processes are ion exchange and surface adsorption of Mg²⁺ ions. In the presence of ammonium hydroxide, Mg(OH)₂ crystals are precipitated on the surface of zeolite 4A at moderate Mg²⁺ ions concentration and the loading of Mg(OH)₂ was found to increase with increasing Mg²⁺ ions concentration. A detailed examination of the interactions between Mg(OH)₂ and functional groups on the zeolite surface was conducted. Solid-state 29Si, 27Al, and 1H NMR spectra were coupled with FTIR measurements, pH and adsorption studies, and thermogravimetric analyses to determine the interactions of Mg(OH)₂ with surface functional groups and to characterize structural changes in the resulting zeolite after Mg(OH)₂ deposition. It was discovered that acid - base interactions between the weakly basic Mg(OH)₂ and the acidic bridging hydroxyl protons on zeolite surface represent the dominant mechanism for the growth of Mg(OH)₂ nanostructures on the zeolite surface.

Mixed-matrix hollow fiber membranes are being developed to offer more efficient gas separations applications than what the current technologies allow. Mixed-matrix membranes (MMMs) are membranes in which molecular sieves incorporated in a polymer matrix do separation between gas mixtures based on the molecular size difference and/or adsorption properties of the component gases vis-à-vis the porous structure and the nature of adsorption sites in the molecular sieve. The development of MMMs to deliver on its promises has however been slow. The major challenges encountered in the efficient development of MMMs are associated with some of the paradigm shifts involved in their processing. For instance, mixed-matrix hollow fiber membranes are prepared by a dry-wet jet spinning method. For an efficient large scale processing of hollow fibers the rheology and kinetics of phase separation of the MMM dopes are important control variables in the process design. Therefore, this research thesis aims to study the rheology and phase separation kinetics of mixed-matrix membrane dopes. In research efforts to develop predictive models for the shear rheology of suspensions of zeolite particles in polymer solutions it was found that MFI zeolite suspensions have relative viscosities that dramatically exceed the Krieger-Dougherty predictions for hard sphere suspensions. Our investigations show that the major origin of this discrepancy is the selective absorption of solvent molecules from the suspending polymer solution into the zeolite pores. Consequently, both the viscosity of the polymer solution and the particle contribution to the suspension viscosity are greatly increased. A predictive model for the viscosity of porous zeolite suspensions incorporating a solvent absorption parameter, α, into the Krieger-Dougherty model was developed. We experimentally determined the solvent absorption parameter and our results are in good agreement with the theoretical pore volume of MFI particles. In addition, fundamental studies were conducted with spherical nonporous silica suspensions to elucidate the role of colloidal and hydrodynamic forces on the rheology of mixed-matrix membrane dopes. Also in this thesis, details of a novel microfluidic device that enables measurements of the phase separation kinetics via video-microscopy are presented. Our device provides a well-defined sample geometry and controlled atmosphere for in situ tracking of the phase separation process. We have used this technique to quantify the phase separation kinetics (PSK) of polymer solutions and MMM dopes upon contact with an array of relevant nonsolvent. For the polymer solution, we found that PSK is governed by the micro-rheological and thermodynamic properties of the polymer solution and nonsolvent. For the MMM dopes, we found that the PSK is increased by increased particles surface area as a result of surface diffusion enhancement. In addition, it was found that the dispersed particles alter the thermodynamic quality of the dope based on the hydrophilic and porous nature of suspended particles.