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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.

Global warming is believed to be caused by the extensive emission of greenhouse gases, such as carbon dioxide, into the atmosphere by combustion of fossil fuels, such as coal, oil and natural gas.To reduce the emission of carbon dioxide and hence avoid global warming, alternative fuels derived from renewable resources are desired. Another reason for the worldwide interest in finding alternative fuels is that the reserves of the fossile fuels are limited and the oil and gas resources will eventually run out.Biogas and natural gas are interesting alternatives with no or at least reduced emission of fossil carbon dioxide to the atmosphere as compared to coal and oil. Both gases mainly consist of methane (60–95%) but may also contain a large fraction of carbon dioxide and water. Removal of carbon dioxide and water from biogas and natural gas is of great importance mainly to lower the transportation costs and to increase the heat value of the gas. The most commonly used separation technique is amine absorption. This is an expensive and complex process and alternative techniques are desired. Zeolites are an interesting alternative due to their great potential both as selective adsorbents and membranes. Due to the unique pore structure zeolites are capable of separating species in a mixture based on the molecule size and adsorption properties. Since water, carbon dioxide and methane all have a molecular size smaller than the pore size of the zeolite ZSM-5 studied in the present work, the molecules can enter and adsorb in the pores and hence the separation is based on adsorption rather than size.In the present work, the single component adsorption of water, carbon dioxide and methane in zeolite ZSM-5 was studied using in-situ Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy and the method was successfully further used to study multicomponent adsorption in zeolites.For single gas adsorption experiments, recorded infrared spectra of adsorbed water, carbon dioxide and methane showed characteristic well separated bands for each gas. Adsorbed concentrations of water, carbon dioxide and methane were determined from the recorded infrared spectra. For single gas experiments, the Langmuir model was fitted to the adsorption isotherms and the model matched the experimental data very well. The fitted Langmuir parameters obtained in the present work showed good agreement with values reported in the literature.For multicomponent adsorption experiments, the Ideal Adsorbed Solution Theory (IAST) was used to predict the adsorbed concentrations of water, carbon dioxide and methane using the single component adsorption isotherm parameters as input. The IAST accurately predicted the adsorbed concentrations of both carbon dioxide and methane when adsorbed from binary mixtures. Internary mixtures, also including water, the IAST accurately predicted the adsorbed concentration of methane, however it severely underestimated the adsorbed concentration of carbon dioxide.The latter is probably an effect of a non-ideal behavior of carbon dioxide in the presence of water.The CO2/CH4 adsorption selectivity was determined for various gas compositions and temperatures showing a general increase in the selectivity with decreasing temperature, which is related to the higher heat of adsorption of carbon dioxide. This indicates that the separation of carbon dioxide from biogas and natural gas should be more efficient at lower temperatures. Compared to the literature, the selectivity observed in the present work is relatively high indicating that low silica Na-ZSN-5 may be an effective membrane material.

The common European Energy and Climate policy states that in 2020 the share of biofuels for inland transports should be 10 %. Such a stipulation calls for a commercially sustainable biofuel production. A promising route for Sweden is biofuel production via gasification of black liquor, which could replace about 25 % of the current Swedish consumption of transportation fuel. The main components in the gas produced by black liquor gasification are H2, CO, CO2, N2, CH4 and H2S, which has been reported in previous work. In the present work, trace components in synthesis gas produced via black liquor gasification have been characterized, since trace components could influence the subsequent fuel synthesis. Of the trace components, the most abundant ones were benzene at an average concentration of about 60 ppm, followed by COS, with an average concentration of about 50 ppm. In addition, low amounts (i.e. a few ppm), of C2-hydrocarbons were observed in the gas. No tars were observed in the gas, but tars were observed in some deposits at pipe walls. The concentration of particles in the synthesis gas was very low; < 0.1 mg/Nm3. Submicron particles were comprised of elements such as C, O, Na, Si, S, Cl, K, and Ca, and these particles probably originated from black liquor. Larger particles were comprised mainly of Fe, S and Ni and were probably the result of corrosion of steel in the plant pipe-work. Synthesis gas was also purified by passing beds of active carbon and zinc oxide, mixed with hydrogen gas from cylinders and in the present work, for the first time, catalytically converted to methanol using bench scale equipment during 45 hours in total. The space time yield of methanol produced at a pressure of 25 bar was 0.16-0.19 g methanol/ (g catalyst h) and comparable results were obtained using synthesis gas from gas cylinders with pure gas. The spent catalyst, exposed to gas from the gasifier, was slightly enriched in Ca and Na at the inlet of the reactor and in B and Ni at the outlet of the reactor. Ca, Na and B probably stem from black liquor whereas Ni probably originates from the stainless steel in the equipment. A slight deactivation of the catalyst exposed to gas from the gasifier was identified but it was not possible to reveal the origin of the deactivation. However, the surface area and mesoporosity of the catalyst was reduced. As expected, the produced methanol also contained water and traces of hydrocarbons up to C4, ethanol and dimethyl ether. In summary, this work has shown that the synthesis gas produced by gasification of black liquor is pure and that methanol synthesis from the gas is quite feasible.

Zeolite membranes exhibiting high flux and high selectivity are of major interest for potential future applications. In order to achieve high flux and high selectivity, the zeolite film must be thin (< 1 µm) and free from flow-through defects. The development of thin defect free zeolite membranes requires powerful tools for characterization of flow-through defects in the membranes. Permporometry is one of the most straightforward and powerful techniques for characterization of flow-through pores in ceramic membranes. In permporometry, the flow of a non-condensable gas, e.g., helium, through the membrane is monitored as a function of the activity of a strongly adsorbing compound, e.g., hydrocarbon.In the present work, MFI membranes prepared by a seeding method were characterized by permporometry using helium as the non-condensable gas and n-hexane or benzene as the adsorbing compound. In order to appreciate permporometry data, the membranes were also characterized by scanning electron microscopy (SEM), single gas permeation and separation experiments. The permporometry data were then compared to the SEM morphology of the membranes, permeances of different probe molecules and membrane separation performance.In order to determine the conditions of the permporometry experiment leading to blocking of zeolite pores, a model describing helium transport in the zeolite pores in the presence of n-hexane or benzene was developed. The model is based on percolation theory and knowledge of the adsorption isotherms and adsorption sites for n-hexane and benzene in the zeolite pores. Parameters needed in the model were estimated by Density Functional Theory (DFT) using a Local-Density Approximation (LDA), the most sophisticated theory yet applied to this system. Based on the permporometry data, it was demonstrated that the model could adequately describe helium transport in zeolite pores in the presence of the hydrocarbons.The sensitivity of the permporometry technique towards the defect size has been improved considerably. It was revealed that high quality MFI membranes prepared in the present work contained mainly micropore defects which are most like the defects in the zeolite crystal lattice (intracrystalline defects).The work has shown how permporometry data could be used to estimate the area distribution of the flow-through defects in the membranes. The results on the defect distribution were corroborated by the SEM observations and the separation experiments. The width of cracks, including support cracks, and open grain boundaries observed by SEM was in excellent agreement with the defect width estimated from permporometry data. A straightforward correlation was observed between separation data and permporometry data, i.e. membranes of higher quality according to permporometry analysis exhibited greater separation performance. Also, the permeance of molecules diffusing through defects in the membrane in the separation experiment was found to scale with the permeance of helium through the defects measured in the permporometry experiment. In addition, this work showed that single gas permeance ratios could not detect slight variations in the membrane quality. For membranes with similar however slightly different amount of defects, the ratios are mainly affected by the membrane thickness and support morphology.To summarise, the present work demonstrates that permporometry data adequately reflect membrane quality and that permporometry is a very powerful technique for MFI membrane characterization.

Cryogenic scanning electron microscopy (cryo-SEM), image analysis (IA) of SEM micrographs and X-ray microtomography (XMT) were used to obtain new information about the morphology of iron ore green pellets in this work. Cryo-SEM and freeze fracturing was used to observe entrapped air bubbles and arrangement of particles around the bubbles and in the matrix of wet green pellets. The observations of samples prepared by plunge and unidirectional freezing indicate that unidirectional freezing facilitates the observation of entrapped bubbles with minimum formation of artifacts, whereas plunge freezing enables observation of the degree of water filling at the outer surface of wet pellets with minimum amount of artifacts. It was also observed in the wet pellets that the size of the water domains in the matrix is quite small and the finer grains are mixed with coarser grains resulting in a denser matrix, whereas no fine grains were observed in the vicinity of the air bubbles. Two types of pellets prepared with and without addition of extra flotation reagent prior to balling were studied using IA and XMT. IA of scanning electron micrographs of epoxy impregnated pellets was used to separate bubble porosity from packing porosity and to quantify the former. The individual SEM micrographs acquired by a backscattered electron detector were reconstructed to provide the entire two-dimensional (2D) sections of the pellets. The 2D data obtained by IA were unfolded to three-dimensional (3D) by stereology and relatively good agreement with XMT data was observed. The size and amount of air bubbles could be quantified with both techniques. The addition of extra flotation reagent was found to increase the number of entrapped air bubbles and slightly decrease the median bubble diameter. The additional entrapped air bubbles due to the addition of extra flotation reagent was shown to be responsible for the difference in total porosity observed by mercury porosimetry between the two types of pellets. Mercury intrusion porosimetry (MIP) is shown in this work to produce inappropriate results with regard to the porosity due to bubble entrapment, it only provides values for total porosity and the throat size distribution of the porosity. In summary, this work has shown that cryo-SEM, IA of SEM micrographs and XMT are powerful and very useful methods for characterization of the morphology of iron ore green pellets.