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.

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.

The greenhouse effect and the limited fossil oil resources have increased the demand of renewable fuels. Zeolite membranes have potential applications in numerous separation processes, and could be useful in the development of efficient processes for renewable fuel production. Methanol synthesis from synthesis gas is equilibrium limited, and continuous removal of products in a zeolite membrane reactor could improve the productivity of a conventional methanol synthesis process. In this work, membranes of two types of zeolite structures, MFI and FAU, were synthesized and evaluated for the separation of methanol from synthesis gas. The synthesis gas was represented by a mixture of hydrogen, carbon dioxide and water. All evaluated membranes were found to display large permeances of methanol and water. At conditions where methanol and water were adsorbing, hydrogen and carbon dioxide were blocked from permeating through the membranes, and the membranes were hence selective. More polar membranes were found to be selective also at higher temperatures. Separation data for one of the membranes were used for modelling the performance of membrane processes for methanol synthesis. It was found that the one pass COx conversion would be much higher in a membrane process than in a traditional synthesis process, assuming that the same membrane performance would be obtained at reaction conditions as that observed at room temperature and atmospheric pressure. It was also found that the total membrane area needed in the membrane processes was practically reasonable.In the process of developing defect free zeolite membranes, it is important to have a tool to characterize flow-through defects. One such tool is permporometry. In this work, permporometry data was compared with SEM observations and mixture separation data. It was shown that permporometry can detect small defects, and that permporometry data correlate well with SEM observations and membrane separation performance.In summary, the present work has contributed to the knowledge of multicomponent separation processes in zeolite membranes. The work has also shown that zeolite membranes could be useful in the challenge of producing renewable fuels, for example by continuously removing products in equilibrium limited processes.

ZSM-5 is an aluminosilicate with high silica ratio with suitable properties for catalysis, ion exchange, adsorption and membrane applications. ZSM-5 is usually produced industrially from concentrated systems in which there is formation of an amorphous gel phase. Typical syntheses of ZSM-5 require sources of silicon and aluminium, a mineralizer and an organic molecule as so-called templating agent. The silicon and aluminum sources widely used for the synthesis are pure reagent chemicals and in particular quaternary ammonium compounds like tetrapropyl ammonium hydroxides (TPA-OH), are employed as templating agents. Unfortunately, these compounds are rather expensive. Demand for inexpensive sources of aluminosilicates for the synthesis of ZSM-5 has increased during the last two decades. Natural raw materials such as kaolin clay and diatomaceous earth (diatomite) are two potential inexpensive sources of silica and alumina. Moreover, the molecule n-butylamine (NBA) has been reported as a low-cost templating agent to replace the quaternary ammonium compounds. The aim of this work was to show for the first time that leached metakaolinite or diatomite in combination with sodium hydroxide and n-butylamine could be used as inexpensive raw materials for the synthesis of ZSM-5 without using an additional source of silica. After synthesis optimization, both sources of aluminosilicate were found to behave differently during the course of synthesis and led to slightly different products. The chemical composition of the raw materials and the products were determined using inductively coupled plasma-sector field mass spectrometry (ICP-SFMS). Crystallinity was examined by X-ray diffractometry (XRD), the morphology was studied by extreme-high-resolution scanning electron microscopy (XHR-SEM) and the specific surface area was estimated from nitrogen adsorption data by the BET method. The chemical composition of individual crystals was determined by energy dispersive spectrometry (EDS). Dealumination of the raw materials by acid leaching made it possible to reach appropriate SiO2/Al2O3 ratios and reduced the amount of impurities. The final ZSM-5 products had a SiO2/Al2O3 ratio in the range 20 – 40. The use of leached diatomite allowed reaching higher yield of ZSM-5 crystals within comparable synthesis times. However, low amounts of mordenite were formed, which was related to the high calcium content of diatomite. Another considerable advantage of diatomite over kaolin is that diatomite does not require heat treatment at high temperature to convert the kaolin to reactive metakaolin. Further characterization of the system by XHR-SEM and EDS at low voltage was carried out in order to understand the nucleation and early growth of the ZSM-5 zeolite crystals. The observations with unprecedented detail strongly suggest that nucleation and the succeeding growth occurs on the gel surface. The growth rates in the various crystallographic directions already at an early stage are such that the shape of the growing crystals resembles that of the final crystals. However, as the early growth is interface mediated, the growth rate along the gel particles is high and the gel particles will become partially embedded inside the growing crystals at an early stage. The Si and Al nutrients are probably transported along the solid/liquid interface and possibly through the liquid in the form of nanoparticles detaching from the gel. The organic template was initially contained in the liquid. However, it remains unclear at which stage the template becomes incorporated in the solid material. EDS at low voltage was also used to gain compositional information about the sodium/calcium ion exchanged products and extraneous phases when kaolin and Bolivian montmorillonite clay were used for the synthesis of zeolite A by alkali fusion. In order to evaluate the cation exchange capacity (CEC) of the synthesized zeolite, ICP-SFMS and EDS were compared. The EDS method used in this work resulted in (Na,Ca)/Al ratios in equivalent moles very close to 1.0 as expected and was therefore found more reliable than ICP-SFMS to measure cation exchange capacity for zeolite A. To summarize, the present work shows that it was possible to synthesize well-crystallized ZSM-5 zeolite from inexpensive raw materials such as leached metakaolin or leached diatomite, sodium hydroxide and n-butyl amine. Furthermore, the crystallization mechanism evidenced in this system might be more general and also apply for other concentrated systems, e.g. those using TPA as structure-directing. Finally, this work displays that EDS at low voltage can provide valuable local compositional information in the field of zeolite synthesis.