In this dissertation the gas permeation process within four hybrid inorganic-organic membranes is modeled at the micro level using molecular dynamics (MD) and at the meso scale level using a diffusion mechanism. The predicted permeances and relative selectivity of CO₂ and CH₄ are compared with the experimental results. In the MD simulation a single-pore silica crystal framework model with and without inserted phenyl groups are used to define two membrane structures. We designate the two cases as PSPM and SPM respectively. To mimic the diffusion of gas across the membrane, a three-region system with a repulsive wall potential on the edge is employed. Results from the SPM model indicate that the pore size affects the permeance but not the selectivity. In the PSPM model the permeance decreases significantly when the pore size is below a critical value. The extent of decrease varies with the type of gas and this is reflected in the large selectivity in the PSPM model. When the initial diameter is 0.4 nm the model shows a selectivity of 17.3, which is very close to experimental results. At this selectivity the CO₂ permeance is 2.87 Ã 10^-4 mol m⁻²s⁻¹Pa⁻¹ and the CH₄ permeance is 1.66 Ã 10⁻⁵ mol m⁻²s⁻¹Pa⁻¹. For different gases we also studied the motions of the phenyl groups in the pore during the permeation process. The results show that in CO₂ diffusion the phenyl groups moves in a larger range than in CH₄ diffusion. The density profile of gas molecules that the phenyl groups see is analyzed using double layer phenyl groups . The results show that the number of phenyl groups cannot affect the permeation. In the meso scale study a mixed mechanism model with a grid framework is developed to model the permeation process. In the model the membrane is assumed to consist of various grids which follow three major diffusion mechanisms. Models with different grid sizes are employed for the four membranes. Parameters in each model are estimated from the permeance results of the two gases. By comparing the estimated parameters in the surface diffusion mechanism with the reported values, the acceptable grid models are determined and the models with the minimum number of grids are studied. The diffusion is dominated by the activated Knudsen diffusion mechanism at lower temperatures and follows the surface diffusion mechanism when the temperature is above a critical value. In the diffusion of both gases within the four membranes the surface diffusion portion is very close but the activated Knudsen diffusion portion is not. This explains why the permeation with high selectivity occurs at lower temperatures. By comparing the results it shows the two studies can validate each other. On the other hand the two methods can be complementary as the diffusion model is able to predict the permeance within the right range and the MD model is able to predict the selectivity more accurately. / Ph. D.

In this work the synthesis, characterization, and gas transport properties of hydrogen selective silica membranes were studied along with the catalytic reforming of CH₄ with CO₂ (CH₄ + CO z 2 CO + 2 H₂) in a hydrogen separation membrane reactor. The silica membranes were prepared by chemical vapor deposition (CVD) of a thin SiO₂ layer on porous supports (Vycor glass and alumina) using thermal decomposition of tetraethylorthosilicate (TEOS) in an inert atmosphere. These membranes displayed high hydrogen permeances (10⁻⁸ - 10⁷ mol m⁻² s⁻¹ Pa⁻¹) and excellent H₂ selectivities (above 99.9 %) over other gases (CH₄, CO, and CO₂). The membranes were characterized using Scanning Electron Microscopy and Atomic Force Microscopy, and the mechanism of gas transport was studied applying existing theories with a newly developed treatment. The catalytic reforming of CH₄ with CO₂ was carried out in a membrane reactor installed with a hydrogen separation ceramic membrane. The reaction was conducted at various pressures (1 - 20 atm) and temperatures (873 K and 923 K) at non-equilibrium conditions, and the results were compared with those obtained in a packed bed reactor in order to evaluate performance of the membrane reactor for the reaction. It was found that concurrent and selective removal of hydrogen from the reaction in the membrane reactor resulted in considerable enhancements in the yields of the reaction products, H₂ and CO. The enhancements in the product yields in the membrane reactor increased with pressure showing a maximum at 5 atm, and then decreased at higher pressures. This was due to a trade-off between a thermodynamic quantity (hydrogen production by the reaction) and transport property (hydrogen separation through the membrane). It was also found that the reverse water-gas shift (RWGS) reaction occurred simultaneously with the reforming reaction giving the detrimental effect on the reaction system by reducing the amount of hydrogen production in favor of water. This was particularly significant at high pressures. / Ph. D.

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

Clonal haematopoiesis of indeterminate potential, or CHIP are a family of mutations present in the general population. CHIP-mutations are prevalent in the haematopoietic stem cells and in the more mature cell populations, T-lymphocytes, B-lymphocytes and myeloid cells (CD3+, CD19+ and CD33+ cells) in blood. By separating these cell populations using magnetic isolation, extracting DNA from the cell populations, and detecting the same mutation in all cell populations, one can prove the presence of CHIP-mutations in a hematopoietic stem cell. At least 50 ng good quality DNA is needed for the gene analysis to detect CHIP-mutations. The magnet separated cell population may be very small, so the DNA extraction method must be optimized to achieve enough DNA yield. The main purpose of the method development was to compare two storage methods before DNA-extractions, and then three different DNA-quantification methods after the DNA-extractions. After the best storage and quantification methods were identified, five samples of cryo-preserved viable cells were used to isolate cell populations using magnetic beads covered in specific antibodies and a magnetic field, and then quantified. Results of the study showed that the best way was to store the cells in ATL-buffer and Proteinase K. To quantify DNA, qPCR was the most accurate method, since the other methods showed incorrect results because of the low DNA concentrations. Magnet cell separation was partly successful. All except one of the DNA yields from the cell separation protocols reached the critical amount of DNA, but some yields were not pure yields of the sought-after cell population. In general, the method must be worked on more with further research.

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