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.

I detta arbete studeras absorption av växthusgasen koldioxid (CO2) i ammoniaklösning. Målet med arbetet är att undersöka hur väl teknik med vegetabilisk olja kan förhindra avdunstning av ammoniaklösning vid absorptionen och på så vis främja grön kemi. En jämförelse görs sedan med en mer beprövad teknik med nedkylning. Därefter undersöks vilka salter som fälls ut vid absorptionen vid de båda teknikerna samt olika koncentration ammoniak (NH3). Genom att blanda ammoniak, etanol (C2H5OH) och vatten (H2O) i olika förhållanden i ett absorptionstorn erhölls den absorberande lösningen. CO2 i gasform fördes sedan in i reaktorn. I genomförda experiment gav teknik med vegetabiliskt oljemembran samma eller lägre materialförlust av ammoniaklösning som teknik med nedkylning. Högre halt av etanol innebar sänkt löslighet av ammoniumsalter vilket gav större utfällning av salter i utförda experiment. Detta kan observeras genom att jämföra kristallvikten i utförda experiment. Kristallerna analyserades med röntgendiffraktion (XRD). Salterna kunde identifieras genomatt jämföra erhållet resultat med standardprov från litteratur. Dock fanns avvikelser mellanresultatet och standardprov, vilket gjorde analysen svårtolkad.

Thin zeolite films have great potential in several novel application areas such as: structured catalysts, membranes and sensors. To fully exploit the advantages of these films it is of great importance to determine the properties of the films. A powerful technique for studies of phenomena at surfaces or in thin films is FTIR/ATR-spectroscopy (Fourier Transform Infra Red / Attenuated Total Reflection). Furthermore, thin zeolite films may be utilized for enhanced selectivity and sensitivity for this technique. In this work films with a thickness of 200 nm of the zeolites ZSM-5 and silicalite-1 were grown on ZnSe, ZnS, ZrO2, Si and Ge ATR elements using a method that had been developed previously. The coated elements were evaluated in a gas sensor application by comparing the sensitivity for a hydrocarbon of zeolite-coated elements versus a standard 10 cm gas cell. The sensitivity was approximately 85 times higher for the coated elements compared to the gas cell at low hydrocarbon concentration. The response time was investigated by exposing the coated element to a step increase of an analyte and recording the response as a function of time. The response was relatively fast, equilibrium was achieved after approximately 250 s, but already after a few seconds a strong signal could be detected. The coated elements were also used to determine single gas adsorption isotherms. The systems studied were n-hexane/silicalite-1 and p-xylene/silicalite-1. Adsorption isotherms determined at varying temperatures were typical for microporous materials. Capillary condensation was observed at higher concentration of the adsorbent. Henry constants and heats of adsorption determined from low-pressure data agreed well with previously reported data in the literature. / Godkänd; 2004; 20070126 (ysko)

In this study, well defined ZSM-5 films were prepared on monoliths, ceramic foams, alumina beads, glass beads and crushed quartz glass by further refinement of a method originally developed at the division of Chemical Technology, Luleå University of Technology. The supports were seeded with silicalite-1 seeds and hydrothermally treated, either at 75 °C or at 150 °C in a single or several steps. By adding sodium to the solution the aluminum concentration increased in the zeolite, which is beneficial for catalytic activity. Consequently, films with different Si/Al ratios could be prepared. The film thickness could be controlled from 110 nm to 9000 nm. Short hydrothermal treatments and use of multi-step synthesis was utilized to prevent excessive bulk crystallization and ultrasound treatment was beneficial in order to remove sedimented crystals on top of the zeolite films. The choice of support material and its influence on the performance of thin ZSM-5 film catalysts was examined by testing the reactivity of the zeolite- coated materials in two reactions; para-xylene isomerization and triisopropylbenzene cracking. ZSM-5 films with a thickness of 150, 350, 800 and 2300 nm, respectively, were prepared on alumina beads and quartz glass. Based upon the zeolite content, the films on quartz glass were much more active for para-xylene isomerization and for cracking of triisopropylbenzene, which is attributed to poisoning of the films on alumina due to impurities in the support. Model parameters were fitted to experimental results. The simulations indicated that thicker films contained a higher fraction of defects, which may be caused by open grain boundaries and cracks. These defects explain higher xylene diffusivities and higher triisopropylbenzene cracking activity for thicker films. As expected, thicker films possessed higher diffusion resistance than thin films despite the higher fraction of defects. The present work has given substantial and valuable fundamental understanding of the performance of thin molecular sieve film catalysts. These findings will be beneficial for development of materials that may be used in novel industrial applications. / Godkänd; 2003; 20070216 (ysko)

Zeolites are very useful in many technological applications such as catalysis, separation and purification of gases and solvents, ion-exchange, etc. The production of zeolites is nowadays carried out with a variety of reagents, such starting materials render large scale production of zeolites expensive. Hence alternative synthesis routes for zeolite production at a lower cost are currently under investigation. One of these routes involves the use of natural aluminosilicate raw materials which have many advantages such as their availability, low price, workability, etc. The aim of the present work was to provide routes to produce synthetic zeolites of industrial attractiveness derived from non-expensive Bolivian raw materials like clays and diatomites. In particular, the work was focused on the synthesis of intermediate- and low-silica zeolites: zeolite Y and zeolite A. The raw materials as well as intermediate materials and final zeolite products were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), nitrogen gas adsorption, inductively coupled plasma mass spectrometry (ICP-SFMS), and UV-VIS spectroscopy.The first part of the study addressed the synthesis and characterization of intermediate silica zeolite Y from diatomite. Prior to synthesis, the diatomite was leached in sulfuric acid to remove impurities, but this step also resulted in dealumination. Therefore, aluminum sulfate was used as an extra source of aluminum. The raw materials were reacted hydrothermally at 373 K in aqueous medium with sodium hydroxide. Variations in parameters like the Na2O/SiO2 ratio and synthesis time were investigated. As a result, micro-sized crystals of zeolite Y were obtained. It was possible to achieve high zeolite yield at a Na2O/SiO2 ratio of 0.9, which produced zeolite Y with a SiO2/Al2O3 ratio of 3.9. Also, synthesis of almost pure zeolite Y with a SiO2/Al2O3 ratio of 5.3 in low yield at a Na2O/SiO2 ratio of 0.6 was achieved. In this respect, diatomite behaved similarly to colloidal silica in traditional syntheses, with both sources of silica having a high degree of polymerization. Zeolite Y with the latter SiO2/Al2O3 ratio might be useful for the production of ultra-stable zeolite Y for use as FCC catalyst.A similar acid leaching procedure, this time with hydrochloric acid, was used for dealumination of diatomite to increase the SiO2/Al2O3 ratio and to reduce the amount of iron in producing well-crystallized ZSM-5 from diatomite in combination with sodium hydroxide and n-butyl amine under appropriate synthesis conditions.The second part of this study dealt with the synthesis of low silica zeolite A from Bolivian montmorillonite-type clay. This clay did contain significant amounts of quartz. Hence, an alkali fusion treatment was applied to the clay by fusing the clay at high temperature with NaOH to make the material more reactive and to take advantage of all the silica present in the clay. The raw clay had a SiO2/Al2O3 ratio of 4, and sodium aluminate was added to the mixture to decrease this ratio to 2. An optimization of the synthesis time was performed. The final zeolite product exhibited high brightness despite the presence of iron in appreciable amount in the starting material and the final product. This was attributed to the magnesium in the raw material, which exerted a masking effect on iron. The latter was incorporated into extraneous magnesium aluminosilica compounds, thereby increasing brightness and strongly decreasing the overall yellowness. This simple method appears as a promising alternative to the complex and costly techniques suggested to reduce the iron content in natural raw materials, especially kaolin.To summarize, this work reports the synthesis of zeolites with promising characteristics from Bolivian raw materials. However, further optimization is required to qualify these products for industrial applications. Moreover, this study might help in the development of poor regions of the Bolivian Altiplano and open up for large scale production, since the methods developed in this work are simple and non-expensiveand other impurities for synthesis of high silica ZSM-5 zeolite. This procedure was successful in producing well-crystallized ZSM-5 from diatomite in combination with sodium hydroxide and n-butyl amine under appropriate synthesis conditions.The second part of this study dealt with the synthesis of low silica zeolite A from Bolivian montmorillonite-type clay. This clay did contain significant amounts of quartz. Hence, an alkali fusion treatment was applied to the clay by fusing the clay at high temperature with NaOH to make the material more reactive and to take advantage of all the silica present in the clay. The raw clay had a SiO2/Al2O3 ratio of 4, and sodium aluminate was added to the mixture to decrease this ratio to 2. An optimization of the synthesis time was performed. The final zeolite product exhibited high brightness despite the presence of iron in appreciable amount in the starting material and the final product. This was attributed to the magnesium in the raw material, which exerted a masking effect on iron. The latter was incorporated into extraneous magnesium aluminosilica compounds, thereby increasing brightness and strongly decreasing the overall yellowness. This simple method appears as a promising alternative to the complex and costly techniques suggested to reduce the iron content in natural raw materials, especially kaolin.To summarize, this work reports the synthesis of zeolites with promising characteristics from Bolivian raw materials. However, further optimization is required to qualify these products for industrial applications. Moreover, this study might help in the development of poor regions of the Bolivian Altiplano and open up for large scale production, since the methods developed in this work are simple and non-expensive.

No description available.

To deal with the increasing demand of renewable fuels, more efficient processes for the production of biofuels are needed. Zeolite membranes have the potential to improve many existing processes that could be used for production of biofuels. Methanol is a potential biofuel that may be produced from synthesis gas in an equilibrium limited reaction. The production of methanol from synthesis gas could be improved by use of a membrane reactor, which could increase the conversion of synthesis gas to methanol per pass in the reactor. Methanol and several other biofuels can be prepared by first gasifying biomass to synthesis gas. Synthesis gas produced from biomass usually contains large amounts of CO2 that must be removed before methanol synthesis. However, commercial processes for CO2 removal are very energy intense, and a membrane process could also improve this process and offer lower energy costs and less complicated and more compact equipment.In the present work, ZSM-5 membranes were prepared and evaluated for removal of CO2 and H2S from synthesis gas. Both synthesis gas prepared from gas cylinders and synthesis gas obtained from a black liquor pilot plant gasifier were used. The separations were performed at industrial relevant conditions, i.e. high pressures. It was found that the CO2 fluxes were very high for CO2 separation from synthesis gas free from H2O and H2S prepared from gas cylinders. CO2 fluxes up to 657 kg m-2 h-1 were observed for a binary mixture (CO2 and H2). The high flux was a result of a thin membrane film, an open graded support, a high pressure drop, resulting in a high diffusivity. A CO2/H2 separation factor of 32.1 was observed at 275K and the selectivity was controlled by CO2 adsorption, blocking the transport of H2. It was also found that the CO2 flux and separation factor decreased substantially when CO2 and H2S was separated from synthesis gas, derived from black liquor, also containing H2O and H2S. This was probably an effect of competitive adsorption of H2S and H2O, which are probably blocking the other molecules from permeating through the membrane.Mathematical models of a traditional methanol synthesis process and two alternative membrane processes were developed. Recorded experimental permeation data for a ZSM-5 membrane was used as input to the models. The estimated performance of the traditional process was compared with a membrane reactor process (MRP) and a membrane module process (MMP). The mathematical model indicated that the MRP is the best alternative, since it enabled one pass operation, due to the highest conversion per pass. The MMP is however better from a practical point of view compared to the MRP since membrane and catalyst is separated and the membrane and reactor can be operated at their optimal respective temperatures and the membrane and catalyst can be replaced independently. By adding more membrane modules, the performance of the MMP will however approach that of the MRP, to the price of higher complexity of the process.

Iron ore pellets are an important refined product used as a raw material in steel manufacturing. In order to meet the requirements of the blast furnace process for steel production, the iron ore is upgraded in a number of steps including, among others, flotation. The induced hydrophobicity of the iron ore concentrate caused by adsorption of the flotation collector may affect the pellet strength both in wet and dry state. In order to minimize the influence of the collector on pellet properties it is important to understand the mechanism by which the collector interacts with iron oxides and what factors may affect this interaction.In this work, the adsorption of a commercial fatty acid type collector Atrac 1563 as well as four model compounds on synthetic iron oxides was studied in-situ using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). The effect of collector concentration, ionic strength, calcium ions and sodium silicate on the collector adsorption was investigated. The mechanism of adsorption of anionic collectors on iron oxides at pH values above the point of zero charge was found to be similar to that of non-ionic collectors. At pH values above the point of zero charge, sodium cations were found to increase collector adsorption on magnetite by reducing electrostatic repulsion while negatively charged silicate species were shown to reduce collector adsorption by blocking magnetite surface sites. Calcium ions were found to significantly enhance the adsorption and possibly induce precipitation of the collector on magnetite even in the presence of sodium silicate suggesting that a high concentration of calcium in the process water could possibly enhance the contamination of the iron ore with the flotation collector, which has been previously shown to have a negative effect on both flotation and pelletization processes.

Stabilization of arsenic contaminated soils by iron oxides has been proposed as a remediation technique to prevent leaching of arsenate into the environment. However, fundamental studies are needed to establish under which conditions the complexes formed are stable. A new method based on ATR-FTIR spectroscopy was adapted to study the adsorption of arsenate species on iron oxides. The measurements required the use of D2O as solvent. The amount of arsenate complexes adsorbed on the iron oxide increased with decreasing pD in the range studied, viz. pD 4-12. Arsenate complexes adsorbed at pD 4 desorbed from the film to some extent as the pD was increased to 8.5 or 12. The stability of arsenate complexes adsorbed on the iron oxide evidently changed with the change in pD, most likely due to the electrostatic repulsion between the negatively charged oxoanion and the more negatively charged iron oxide as the pD increased. From competitive adsorption experiments it was found that arsenate species were more strongly bonded to the iron oxide than phosphate species. Furthermore, it was found that two different phosphate complexes formed on the iron surface at pD 4, one deuterated and the other one de-deuterated. The complexes showed very different stability. The deuterated phosphate complex was desorbed easily from the iron oxide film as arsenate was added to the system whereas the de-deuterated phosphate complex only desorbed slightly from the film upon adding arsenate.This work has increased the fundamental knowledge of the iron oxide/arsenate/phosphate system, which will be of importance for the development of more effective soil remediation techniques.