This work concerns evaluation by permeation measurements and modeling of thin (<2µm) MFI molecular sieve membranes and, to a smaller extent, synthesis of such materials. The membranes have been synthesized on graded a-alumina microfiltration filters using The seed film method. Scanning electron microscopy and x-ray diffraction were used for characterization in addition to permeation measurements. Mathematical models describing membrane flux for real membranes and defect distributions were developed. Defect distributions were calculated from porosimetry data and were further used for prediction of single gas permeation characteristics for real membranes. The models confirm the experimental findings, with respect to ideal selectivities as a measurement of membrane quality. Membrane permeation simulations indicate increasing ideal selectivities, with increasing film thickness, for quotients containing SF6. Thereby a high quality membrane could possess low ideal selectivities. This finding was confirmed by comparing experimental data of several membranes with varying thickness. The correlation between multi component separation data and commonly used quality criteria was investigated. It was found that commonly used single gas permeation quotients (ideal selectivity) between light inorganic gases, especially those containing sulphurhexaflouride (SF6), is less appropriate for membrane quality measurement. The porosimetry experiment showed on the other hand a good agreement between experimental data and separation performance of the membranes, as expected. ZSM-5 membranes with low aluminum content and silicalite-1 membranes with similar material properties, such as defect distribution and thickness were evaluated with multi component hydrocarbon isomers permeation. The ZSM-5 membrane had lower permeances and a slightly better butane isomer separation performance than the silicalite-1 membrane. The latter membrane showed a minimum in separation selectivity between two C6 isomers whereas the ZSM-5 membrane showed an almost constant selectivity, independent of temperature, but with lower permeances. ZSM-5 membranes with a high aluminum content catalyzed the formation of diethylether and ethylen at temperatures exceeding 150°C from a water/ethanol mixture. The membrane separated a mixture of C4 isomers with good performance at elevated temperatures. However these membranes suffered from temperature instability problems. / Godkänd; 2002; 20070224 (ysko)

Molecular sieve films and colloidal particles may have great potential for further utilization in novel technological sophisticated applications such as structured catalysts, sensors and membranes. The work presented in this thesis concerns the synthesis molecular sieve films and the crystallization of zoned MFI materials for novel catalyst and sensor applications. The seeding method developed at the division has been modified for the preparation of MFI and FAU type films on a variety of steel substrates ranging from ordinary carbon steel to highly corrosion resistant stainless steel. The films were characterized by SEM, XRD and gas adsorption techniques. The results revealed that the type of steel did not affect the film morphology, the thickness or the preferred orientation of the crystals, whereas the thermal stability was dependent on the steel. Films on various stainless steel supports were stable during calcination, whereas films on carbon steel supports peeled off upon rinsing after calcination because a relatively thick magnetite/hematite film formed. Pre-calination of carbon steel improved the zeolite film stability upon calcination. Zoned MFI materials (colloidal zoned MFI crystals and zoned films) were synthesized in this work in order to improve the catalytic performance of MFI. A two-step crystallization method was developed to prepare zoned MFI materials, in which precursor ZSM-5 colloidal particles or film were grown in a silicalite-1 synthesis solution directly or after acid treatment. It was shown that zoned MFI materials did not form when the ZSM-5 surface had a high aluminum content. In this case, polycrystalline aggregates or a sandwich film formed due to secondary nucleation. After reducing the aluminum content to half by acid treatment of ZSM-5, secondary nucleation of new silicalite-1 crystals was inhibited and zoned MFI material was obtained. / Godkänd; 2003; 20070216 (ysko)

A novel synthesis method called a two-stage varying-temperature synthesis was developed for the investigation of kinetics and mechanism of the crystallization of discrete colloidal crystals of TPA-silicalite-1. Briefly, this method involves a rapid change in treatment temperature at some point during the crystallization. By extending the duration of the period at the initial synthesis temperature, the crystal concentration and final crystal size varied until they were approximately equal to those obtained for a complete synthesis at the initial temperature. At this point in the crystallization, it was concluded that the nucleation stage was completed. In the TPAOH-TEOS-H2O system, the nucleation was a continuous process and the rate of nucleation was initially high immediately after the start of hydrothermal treatment, but then exponentially declined throughout the nucleation period. In the TPAOH-SiO2-H2O-ethanol system, where SiO2 was colloidal amorphous silica, the nucleation was still a successive process, whereas the nucleation profile was more similar to that usually considered to occur during zeolite syntheses with an autocatalytic increase in the nucleation rate. When the synthesis conditions were identical, except for the silica source in the above two systems, the nucleation period for the TPAOH-SiO2-H2O-ethanol system was longer than that for the TPAOH-TEOS-H2O system. This was presumably due to the fact that the colloidal silica particles needed to depolymerize to reach a supersaturation concentration in order for nucleation and crystal growth to occur. Also, it was found that irrespective of silica sources, the vast majority of nucleation occurred during an induction period before linear crystal growth started. The two-stage synthesis method could also be used to produce particularly small colloidal crystals of TPA-siliclaite-1 with reduced synthesis times and high yields. Using this method involves starting a synthesis at a lower temperature and ending the synthesis at a higher temperature. After determining the nucleation stage, an elevated temperature can be used to accelerate the crystal growth and reach higher equilibrium yields controlled by the final temperature. The effects of temperature, dilution and alkalinity on the synthesis were studied to optimize syntheses. The effect of aging on the kinetics and mechanism for crystallization of colloidal TPA-silicalite-1 with varying silica source was also investigated with the two-stage synthesis procedure. With the TEOS silica source, aging for up to 15 days at room temperature had no significant effect on the nucleation and crystallization at a low synthesis temperature. Whereas with amorphous silica, aging caused the nucleation kinetics to become increasingly similar to those for syntheses with TEOS. Thus, with sufficient aging of more economical amorphous silica sources, the properties of the final products approached that with the more exotic TEOS silica source, viz., small colloidal crystals with a narrow crystal size distribution. / Godkänd; 2000; 20070318 (ysko)

The preparation of zeolite macrostructures in the form of bilayered hollow tubes and microspheres is presented. The bilayered hollow ZSM-5/silicalite-1 tubes were prepared using carbon fibers as a substrate. The surface of the fibers was modified and colloidal silicalite-1 seed crystals adsorbed. The fibers were then treated with a synthesis mixture yielding ZSM-5. After separation of the fiber/zeolite composites a second treatment resulting in the crystallization of silicalite-1 was performed. Finally, the carbon fibers were removed by calcination leaving hollow tubes. Silicalite-1 micropsheres were prepared using macroporous anion exchange resins as shape directing macro-templates. Resin beads were hydrothermally treated with a synthesis solution yielding silicalite-1 resulting in the crystallization of silicalite-1 in the pores of the resin. The resin was then removed by calcination leaving self-bonded silicalite-1 micropsheres identical in shape and size to the original resin beads. The zeolite macrostructures were extensively characterized using SEM, XRD, EDS-analysis, Raman spectroscopy, nitrogen adsorption and microhardness measurements. / Godkänd; 1999; 20070322 (ysko)

The solid state reaction between sodium tri-titanate and sodium carbonate, forming mainly sodium penta-titanate, was investigated. Experiments were carried out in a micro-differential reactor made of quartz glass at various temperatures between 800°C and 880°C and in a pilot fluidized bed reactor operated in a semi-batch mode. In the micro-differential reactor, basic kinetic data was obtained by measuring the release of carbon dioxide during the reaction. Different kinetic models were considered to describe the conversion, such as the Valensi-Carter model for diffusion controlled reaction rates and the phase-boundary model for first-order reaction kinetics. Furthermore, a model that included both diffusion in the solid material and the chemical kinetics was derived. This model described the experimental data obtained in the micro-differential reactor very well. Finally, rating models describing the conversion obtained in a fluidized bed and in an entrained flow reactor were developed. / Godkänd; 1999; 20070403 (ysko)

The work presented in this thesis was aimed to synthesize zeolite films in the absence of organic additives to avoid the potentially detrimental calcination procedure. Furthermore, the support surface was seeded with colloidal seed crystals prior to film growth. This technique has previously been used to prepare thin zeolite films. The films were characterized by Scanning electron microscopy (SEM), X-ray diffraction (XRD) and gas permeation experiments. Films of three different types of zeolites were synthesized in this work; FAU-type zeolite, ZSM-5 and zeolite NaA. The thickness of the FAU-type zeolite films could be controlled by varying the synthesis temperature and duration. However, a maximum film thickness was found. Prolonged hydrothermal treatment caused the film thickness to decrease due to the transformation of FAU into zeolite P. The adsorbed seeds were oriented with the <111> pyramid parallel to the surface of the support. During growth, the crystals constituting the films became randomly oriented. The ZSM-5 films were tested as membranes for the separation of butane isomers. The selectivity for n-butane/i-butane had a maximum value of 17.8 at 220°C. Furthermore, the ZSM-5 membranes were found to be catalytically active, converting ethanol into diethylether and ethylene. The growth of silicious species into the porous support during zeolite NaA membrane synthesis was examined. Higher temperatures of synthesis resulted in relatively more growth into the porous support compared to the film growth on top of the support. By using a multi-step synthesis procedure at low temperature, thicker films with less growth into the support could be prepared. / Godkänd; 2001; 20070315 (ysko)

The main objective of this thesis was to acquire a better understanding of the mechanisms involved in the preparation of Silicalite-1 films in general and on gold surfaces in particular. Molecular sieve films on gold surfaces were prepared using the seed film method. The deficiency of negative charge on a gold surface in aqueous solution was overcome by a coupling agent (gamma-mercaptopropyltrimethoxysilane or sodium hydrosulfide). The resulting negatively charged surface was modified by a cationic polymer, facilitating the adsorption of negatively charged colloidal silicalite-1 seed crystals. The seed crystals were grown into a continuous molecular sieve film during hydrothermal treatment in synthesis solution. Reflection absorption infrared spectroscopy was found to be an excellent method to gain insight about the structures formed after each step in this preparation procedure. The recorded vibrational spectra were compared with vibrational modes calculated from the dynamic matrix of the clusters concidered. These comparisons showed that the organic coupling agent was oriented with the methylene chain perpendicular to the gold surface, the cationic polymer introduces disorder in the silane layer, the silanol groups predominantly form 6-membered puckered Si-O rings upon condensation and that linear defects in the films are formed during the hydrothermal treatment. The effects of seed size and hydrothermal treatment time on the formation of linear defects were investigated. / Godkänd; 1999; 20070320 (ysko)

The preparation of molecular sieve based catalysts in appropriate macroforms suitable for practical utilization is of great technological importance. This thesis is dedicated to the preparation of metal containing molecular sieve macrostructures (modified macrostructures). Modified molecular sieve macrostructures were prepared by the resin templating method. Firstly, molecular sieves were synthesized within the pore structure of macroporous anion exchange resin beads. After this step, a certain degree of ion exchange capacity is retained by the resin facilitating the secondary insertion of metal anions. Metal anionic species were ion exchanged into the resin-molecular sieve composites obtained in a following step. Finally, the resin was removed by calcination leaving behind self-bonded metal containing molecular sieve spheres with a shape and size similar to the original resin beads. V, W, Cr and Pd containing macrostructures were prepared by the method. Resin-silica composites, in which the structure of the silica was changed from amorphous to crystalline silicalite-1 were used for the preparation of the V and W spheres. The Cr and Pd containing spheres were prepared from resin-zeolite beta composites. The properties of the product spheres (metal content, crystallinity, morphology, nature of the metal species, etc.) were extensively characterized by atomic adsorption spectrometry, X-ray diffraction, scanning electron microscopy, energy dispersive, Raman and UV-vis spectroscopy, nitrogen adsorption and chemisorption measurements. The materials prepared are of interest for application mainly in the area of catalysis. / Godkänd; 2002; 20070222 (ysko)

Godkänd; 1998; 20070322 (ysko)

Syftet med denna studie var att öka kunskapen kring förträngningskristallisation av metalklorider så som litiumklorid. Många kloridsalter har tidigare uppvisat svårigheter att kristallisera med förträngningskristallisation på grund av höga lösligheter av kloridsalter i organiska lösningsmedel. I detta arbete undersöktes också utfällning av metaller med det konjugerande basen av organiska syror så som citronsyra, ättiksyra, myrsyra och glukonsyra för att möta ny forskning om lakning av katodmaterial med dessa syror. Denna studie utgörs av en litteraturstudie med fakta om nämnda system för att på så vis finna de faktorer som påverkar utsikterna för kristallisation med lösningsmedel. Inom litteraturstudien var fokus också på att finna korrelationer mellan systemkomponenternas egenskaper och möjligheterna för systemet att kristallisera. Vidare var den insamlade informationen också föremål för diskussion för att sedan ge förslag på framtida experiment för att förstå dessa system bättre. Dessutom utfördes experiment på litium- och nickelklorider samt litiumkarboxylater med flera olika lösningsmedel. Experimenten visade att ingen av de testade lösningsmedlen fällde ut litium- och nickelklorid förutom ättiksyra och DMSO som fällde ut nickelklorid. Av de testade karboxylaterna visade det sig möjligt att fälla ut en fast fas från en laklösning innehållande Li, Ni, Mn och Co genom att tillsätta aceton. Dock kunde varken litiumglukonat, acetat eller format fällas ut med de lösningsmedel som användes. Från denna studie drogs slutsatsen att en trolig anledning för utebliven utfällning av kloridsalterna var deras förmåga att bilda lösliga komplex med kloridjoner och lösningsmedel och att framtida forskning på dessa system bör fokusera på att minska denna komplexbildning. Ett annat hinder som uppdagades av experimenten var fasseparation av vatten och organfas, speciellt när aceton och acetonitril användes. Därför rekommenderades det också att undersöka dessa system vid högre temperaturer. För karboxylatsystemen rekommenderades också att framtida forskning bör fokusera på att undersöka tillsatts av olika lösningsmedel vid olika pH eftersom detta troligen påverkar komplexbildning i dessa system. / The purpose of this study was to increase the understanding of antisolvent crystallization on metal chloride salts, in particular lithium chloride. Many chloride salts have previously been shown to be challenging for antisolvent crystallization due to high solubilities of metal chlorides in many organic solvents. In addition, precipitating metals using the conjugate base of organic acids, such as citrate,acetate, formate and gluconate as anions were also tested to reach beyond chloride systems and to meet the current research on battery leaching. The study was produced by a literature survey collecting information about the mentioned systems for antisolvent crystallization in order to assess the main factors affecting the possibilities for antisolvent crystallization in these systems. Within the literature study focus was also to investigate eventual correlations between the characteristics of the components in the system to the outcome upon solvent addition. Furthermore, the assessed information was discussed and evaluated in order to give suggestions on future experiments in order to understand these systems better. In addition, lithium and nickel chlorides and carboxylates were experimentally screened for different antisolvents. It was concluded that none of the tried antisolvent could precipitate concentrated solutions of lithium and nickel chloride except for acetic acid and DMSO which precipitated nickel chloride. Of the tried metal carboxylates it was possible to precipitate metal citrates from a leachate containing Li, Ni, Mn and Co using acetone. However, neither lithium gluconate, acetate or formate could be precipitated with the solvents tried. The study concluded that a probable reason for the challenges of precipitation of metal chlorides is their tendency to form soluble chloro and solvo complexes and that future research on these systems should focus on decreasing the complex formations. Another obstacle found by the experiments is the occurrence of salt induced phase separation in several systems, in particular those containing acetone and acetonitrile. Therefore, it was recommended to investigate these systems at elevated temperatures. For the carboxylate systems it was concluded that screening for promising antisolvents in future research should be done at different pH in order to assess the effect of chelation with the cations.