Doctor of Philosophy, The Ohio State University, 2018, Chemical Engineering

Membrane processes are attractive for gas separation applications, including H2 purification and CO2 capture. Advanced nanostructured polymer membranes based on facilitated transport mechanism showed potential in H2 purification for fuel cell applications due to its oxidative stability and ability to simultaneously remove CO2 and H2S from a feed gas. In addition, the membranes could achieve high CO2 permeance and hence also suitable for CO2 capture from flue gas. In this work, CO2-selective membranes research development from lab-scale to field-test was conducted. CO2-selective membranes comprised of a quaternaryammonium hydroxide mobile carrier, a quaternary ammonium fluoride fixed-site carrier, borate-based additives, and crosslinked polyvinylalcohol was developed. The optimized membrane composition containing tetrafluoroboric acid demonstrated oxidative stability with a CO2 permeance of 100 GPU and CO2/H2 selectivity > 100 for at least 144 hours at 120°C with humid air as the sweep gas. The membrane was scaled-up to fabricate 14-in wide flat sheet membranes with > 1400-ft long in total length. The scale-up membrane performed similarly compared to the lab-scale membranes and demonstrated the potential for membrane processes that use air as the sweep gas including the H2 purification in fuel cell applications. Fabrication of CO2-selective membranes was scaled-up to prepare membranes with 14-in wide and > 150-ft long with a uniform selective-layer thickness of around 15 microns. The membrane contained aminoisobutyric potassium salt and polyvinylamine as the carriers for facilitated transport of acid gases and crosslinked polyvinylalcohol as the membrane matrix. The scale-up membranes demonstrated similar performances as the lab-scale membranes with a CO2 permeance > 200 GPU, CO2/H2 selectivity > 200, and H2S/H2 selectivity > 600 and were used for a field test of prototype spiral-wound membrane modules with autothermal reformate gas as the feed gas. The modeling (open full item for complete abstract)

Committee: W.S. Winston Ho (Advisor); Bhavik Bakshi (Committee Member); NIcholas Brunelli (Committee Member) Subjects: Chemical Engineering

Doctor of Philosophy, The Ohio State University, 2007, Chemical Engineering

In this work, new CO2-selective membranes were synthesized and their applications for fuel cell fuel processing and synthesis gas purification were investigated. In order to enhance CO2transport across membranes, the synthesized membranes contained both mobile and fixed site carriers in crosslinked poly(vinyl alcohol). The effects of crosslinking, membrane composition, feed pressure, water content, and temperature on transport properties were investigated. The membranes have shown a high permeability and a good CO2/H2 selectivity and maintained their separation performance up to 170°C. One type of these membranes showed a permeability of 8000 Barrers and a CO2/H2selectivity of 290 at 110°C. The applications of the synthesized membranes were demonstrated in a CO2-removal experiment, in which the CO2 concentration in retentate was decreased from 17% to < 10 ppm. With such membranes, there are several options to reduce the CO concentration of synthesis gas. One option is to develop a water gas shift (WGS) membrane reactor, in which both WGS reaction and CO2-removal take place. Another option is to use a proposed process consisting of a CO2-removal membrane followed by a conventional WGS reactor. In the membrane reactor, a CO concentration of less than 10 ppm and a H 2concentration of greater than 50% (on dry basis) were achieved at various flow rates of a simulated autothermal reformate. In the proposed CO2-removal/WGS process, with more than 99.5% CO2 removed from the synthesis gas, the CO concentration was decreased from 1.2% to less than 10 ppm (dry), which is the requirement for fuel cells. The WGS reactor had a gas hourly space velocity of 7650 h-1 at 150°C and the H2 concentration in the outlet was more than 54.7% (dry). The applications of the synthesized CO2-selective membranes for high-pressure synthesis gas purification were also studied. We studied the synthesized membranes at feed pressures > 200 psia and temperatures ranging from 100-150 °C. The effects of (open full item for complete abstract)

Committee: W.S. Winston Ho (Advisor) Subjects:

BA, Oberlin College, 2011, Physics and Astronomy

There are a range of environmental and industrial applications to capturing carbon dioxide from gas mixtures. Currently, materials being used in these applications bind carbon dioxide too strongly for practical purposes, such that they require large amounts of energy to be regenerated for reuse. Highly porous materials called metal-organic frameworks (MOFs) could serve much more effectively as carbon-capturing materials, as they suck up large amounts of carbon dioxide gas at pressures and temperatures that are nearly ideal for carbon-capture applications. Moreover, they require much less energy than current materials to release the carbon dioxide and be regenerated. Additionally, many different structures can be created fairly easily, so scientists are on the hunt for the ideal carbon-capturing MOF. In this thesis we study Mg-MOF-74, a particularly promising metal-organic framework material for separating carbon dioxide from gas mixtures. We use infrared spectroscopy to probe the interactions between the Mg-MOF-74 host and both carbon dioxide and methane. By shining infrared radiation on Mg-MOF-74 with gases trapped in it and looking at which frequencies of radiation are absorbed by the bound gases, we can learn about the binding nature of the framework. This in turn helps us to better understand the properties are are preferable in metal organic frameworks, and will aid chemists in fabricating new structures that are ideal for carbon-capture and other applications.

Committee: Stephen FitzGerald PhD (Advisor) Subjects: Molecular Physics; Physical Chemistry; Physics

Doctor of Philosophy, The Ohio State University, 2023, Chemistry

Metal-organic frameworks (MOFs) are crystalline, porous materials constructed from metal ions or clusters linked by organic ligands. The resulting structures exhibit a range of pore sizes that can be tailored to specific applications. MOFs have attracted significant attention in recent years due to their potential applications in areas such as gas adsorption and separation, catalysis, drug delivery, and sensing. There are a variety of methods that can be used to synthesize MOFs, including solvothermal, microwave, and sonochemical routes. These methods offer varying degrees of control over the size, shape, and porosity of the resulting MOFs, and can be optimized to produce MOFs with specific properties. The sharply rising atmospheric CO2 concentration is a major environmental concern. The biggest challenge for current CO2 capture technologies is the high energy penalty associated with regeneration. Therefore, the US Department of Energy (DOE) has launched the Carbon Negative Shot as a call for innovations in CO2 removal technologies to support net zero emission of CO2 by 2050 and to target a reduction in the cost to $100 per metric ton of CO2. MOFs, as a new generation of solid absorbents, have the potential to directly harvest CO2 from air and can be easily tuned for energy efficient regeneration. Our group has developed a Zn‒OH functionalized benzotriazolate MOF, 1-ZnOH (Zn(ZnOH)4(bibta)3, bibta2‒ = 5,5-bibenzotriazolate), derived from CFA-1 (Coordination Framework Augsburg-1) that shows excellent performance for trace CO2 capture. Short Zn...Zn distances in 1-ZnOH enable inter-cluster hydrogen bonding, which is responsible for its high CO2 adsorption capacity. Postsynthetic metal exchange has been applied to CFA-1 to generate a series of MOFs with tunable CO2 binding strength and uptake capacity. Chapter 2 of this thesis will describe the application of Density Functional Theory (DFT) calculations and column breakthrough experiments to assess the role of metal (open full item for complete abstract)

Committee: Casey Wade Dr. (Advisor); Christine Thomas Dr. (Committee Member); Robert Baker Dr. (Committee Member) Subjects: Chemistry

BA, Oberlin College, 2019, Physics and Astronomy

In this thesis, we designed and built a gas flow-through system to study dynamic adsorption separation of hydrogen isotopes in metal-organic frameworks (MOFs). MOFs are porous, crystalline materials composed of metal complexes connected by organic linkers. They have been proposed as a cheaper, more energy efficient approach to hydrogen isotope separation than current industrial methods. We have previously found evidence of a zero-point energy-based separation mechanism for hydrogen isotopes in two MOFs: Co-MOF-74 and Cu(I)-MFU-4l. This mechanism, chemical affinity quantum sieving (CAQS), has been extensively studied under static equilibrium conditions. The system in this work was developed so that CAQS could be studied under dynamic conditions that more closely resemble those in industrial separation. Breakthrough analysis is an established technique for studying dynamic separation in porous materials. Generally, a breakthrough experiment involves flowing a gas mixture through a fixed bed of adsorbent material and measuring the composition of the effluent flow. In this work, a 1:1 mixture of common hydrogen and its isotope deuterium was flowed through 71 mg of Co-MOF-74 or 22 mg of Cu(I)-MFU-4l. A quadrupole mass spectrometer was used to monitor the composition of the effluent flow. We saw preferential adsorption of deuterium over common hydrogen in Co-MOF-74 at 77K and Cu(I)-MFU-4l at 170K, 140K, and 110K. This behavior was absent in Cu(I)-MFU-4l at 77K, a phenomenon that we would like to investigate further. Minimal adsorption occurred in both MOFs at room temperature, as expected. A selectivity of deuterium over common hydrogen was calculated for each temperature. These selectivities were approximately 30% lower than comparable literature values. Our goal is to make improvements to our system and methods to measure the selectivity more accurately and reproducibly. Notably, all measured selectivities were higher than the selectivity of the Girdler Sulfide method a (open full item for complete abstract)

Committee: Stephen FitzGerald (Advisor) Subjects: Materials Science; Physics

Doctor of Philosophy, The Ohio State University, 2018, Chemical Engineering

Polymeric facilitated transport membranes (FTMs) driven by reversible amine-CO2 reactions were developed in this study for selective CO2 separation from flue gas (CO2/N2) and syngas (CO2/H2). For post-combustion carbon capture, a FTM was synthesized in a composite membrane configuration with a 170 nm selective layer coated on a nanoporous substrate. In the selective layer, polyvinylamine with amine-sites covalently bonded to the polymer backbone was used as fixed-site carrier and an amino acid salt, synthesized by deprotonating sarcosine with 2-(1-piperazinyl)ethylamine, was blended as mobile carrier. Multi-walled carbon nanotubes wrapped by a copolymer poly(vinylpyrrolidone-co-vinyl acetate) were dispersed in the selective layer as reinforcement fillers to refrain the selective layer penetration upon vacuum suction. The membrane demonstrated a CO2 permeance of 1451 GPU (1 GPU = 10-6 cm3(STP)·cm-2·s-1·cmHg-1) and a CO2/N2 selectivity >140 at testing conditions relevant to this separation modality. A field trial with 1.4 m2 spiral-wound membrane modules fabricated from this FTM was conducted with actual flue gas at National Carbon Capture Center in Wilsonville, AL. The separation performances of the modules agreed well with those of the lab-scale flat-sheet membranes. A 500-h stability was demonstrated in spite of the interference of system upset and flue gas outage. Two membrane processes were designed for the FTM to decarbonizing coal-derived flue gas with 90% CO2 recovery. Power plant combustion air and a CO2-depleted retentate within the membrane system were identified as effective sweep gases to provide the transmembrane driving force. Both membrane processes yielded a capture cost ca. 40/tonne CO2 in 2011 dollars, which nearly met the target set by the U.S. Department of Energy for 2025. For pre-combustion carbon capture, FTMs were tailored for a single-stage membrane process to decarbonize coal-derived syngas. In these membranes, water-s (open full item for complete abstract)

Committee: W.S. Winston Ho (Advisor); Liang-Shih Fan (Committee Member); Andre Palmer (Committee Member) Subjects: Chemical Engineering; Polymers

PhD, University of Cincinnati, 2010, Engineering and Applied Science: Chemical Engineering

The goal of this research is to develop zeolite membranes that can simultaneously provide high H2 selectivity and high H2 permeance while possessing adequate hydrothermal and chemical resistances for hydrogen separation from fuel gases and WGS reaction at high temperature of 400 to 550°C. This dissertation work consists of three main parts of research including (1) the development of microwave-assisted method for synthesis of MFI zeolite membranes from template free precursors by seeded secondary growth; (2) controlled modification of MFI zeolite channels by chemical deposition and understanding the mechanism of high H2-selectivity against slightly bigger gases with high H2 permeance at elevated temperatures; and (3) the demonstration of high temperature water gas shift reaction (WGS) in the modified MFI zeolite membrane for enhanced CO conversion. Membranes have been synthesized by seeded secondary growth method from a template-free precursor solution containing NaOH, SiO2, H2O, and Al2(SO4)3 under conventional and microwave heating methods. The effects of precursor composition and synthesis conditions on the membrane formation and membrane quality have been investigated. The MFI zeolite membranes obtained by seeded secondary from the template-free precursor tend to develop oblique orientation. Gas permeation tests on small molecules, such as H2 and CO2, and large molecules, such as SF6 have shown that the membranes were free of pinholes and contain minimal amount of non-zeolitic intercrystal spaces. The zeolite membranes obtained from template-free precursors do not need a firing for template removal that avoids the risk of defect formation during the template removal process. The microwave synthesis method was found to dramatically reduce the hydrothermal synthesis duration as compared to the traditional heating method, and hence is more energy-efficient. According to the molecular dynamic diffusion theory, the MFI-type zeolite pore size is incapable of obtain (open full item for complete abstract)

Committee: Junhang Dong PhD (Committee Chair); Anastasios Angelopoulos PhD (Committee Member); Peter Panagiotis Smirniotis PhD (Committee Member); Henk Verweij PhD (Committee Member) Subjects: Chemical Engineering

PhD, University of Cincinnati, 2003, Engineering : Chemical Engineering

Molecular simulation studies of two polyphosphazene polymers including poly[bis(2,2,2-trifluoroethoxy)phosphazene] (PTFEP) and poly[bis(3-methylphenoxy)phosphazene] (PBMP) are presented in this dissertation. Self-diffusion and sorption of seven gases (He, H 2 , O 2 , N 2 , CH 4 , CO 2 , and Xe) in PTFEP have been investigated by molecular dynamics and Grand Canonical Monte Carlo (GCMC) simulations of two amorphous cells and the alfa-orthorhombic crystalline supercell. In the case of the MD simulation of diffusion coefficients, values obtained for both amorphous and crystalline PTFEP are comparable and agree with experimental values obtained for semicrystalline samples. Diffusion coefficients follow a linear correlation with the square of effective diameter of gas molecules according to the correlation of Teplyakov and Meares. On the other hand, solubility coefficients obtained from GCMC simulation of the amorphous cells are approximately four to five times higher than would be expected on the base of the amorphous content of the experimental semicrystalline samples alone. The results suggest that while the crystalline domains in semicrystalline PTFEP samples do not reduce gas diffusivity they significantly reduce gas solubility. A new gas solubility correlation that includes both the Lennard-Jones potential well depth parameter, ε/κ, and the Flory interaction parameter, χ, successfully correlates gas solubility coefficients for all gases including CO 2 . The elevated CO 2 solubility coefficients above the linear correlation of Teplyakov and Meares were attributed to a quadrupole-dipole interaction with the trifluoroethoxy groups of PTFEP by ab initio molecular orbital calculations of CO 2 and model compounds (CH 4 , CH 3 CH 3 , CH 3 CH 2 CH 3 , CF 4 , CF 3 CH 3 , and CF 3 CH 2 CH 3 ). In addition, molecular dynamics simulations of an alfa-supercell indicated that the mesophase transition is associated with a conformational change from the planar cis-trans conformati (open full item for complete abstract)

Committee: Dr. Joel R. Fried (Advisor) Subjects:

Doctor of Philosophy, University of Toledo, 2011, Chemistry

Ionic liquids (ILs) are a class of molten salts with melting points below 100 °C. Their unique properties including high thermal stability, wide viscosity range, negligible vapor pressure under room temperature, and the capability of undergoing multiple solvation interactions make them ideal candidates as gas chromatography (GC) stationary phases and sorbent coatings in solid-phase microextraction (SPME). The first part of this dissertation includes an introduction of ionic liquids and their applications as GC stationary phases. The following chapters in this part introduce various example of utilizing ILs as GC stationary phases. Functionalized ILs containing different functional groups and tris(pentafluoroethyl)trifluorophosphate (FAP) anion have been characterized using the solvation parameter model and applied as selective GC stationary phases. A total of fifteen ILs are examined on the basis of multiple solvation interactions. The effect of cation functional group, cation type, and counter anion has been thoroughly evaluated. The binary mixtures consisting of two PILs have been employed as highly selective GC stationary phases. The effects of PIL composition on the bleed temperature, system constants, and separation selectivity are examined. PILs have been proven to be an ideal class of SPME sorbent coatings with promising thermal stability, extraction efficiency, and selectivity. The second part of this dissertation begins with an introduction of the application of ILs and PILs as sorbent coatings in SPME. Two chapters are then presented describing the design, synthesis, and application of two different types of PILs as sorbent coatings in SPME for the selective extraction of CO2. The presence of functional groups within the PILs results in different mechanism of CO2 capture. The analytical performances of the PIL fibers are evaluated and compared to that of the commercial fibers. The PIL-fibers and a selected commercial fiber are applied for the selective ext (open full item for complete abstract)

Committee: Jared Anderson PhD (Advisor); Jon Kirchhoff PhD (Committee Member); Xiche Hu PhD (Committee Member); Maria Coleman PhD (Committee Member) Subjects: Chemistry

Doctor of Philosophy in Engineering, University of Toledo, 2010, Chemical Engineering

Two diamino room temperature ionic liquids, 1,3-di(3-aminopropyl)imidazolium bis[(trifluoromethyl)sulfonyl]imide (monocationic RTIL or mRTIL) and 1,12-di[3-(3- aminopropyl)imidazolium]dodecane bis[(trifluoromethyl)sulfonyl]imide (dicationic RTIL or diRTIL) were synthesized using a Boc protection method. The two RTILs were incorporated within the 6FDA-MDA backbones to tune the solubility properties and improve the separation of CO2 from CH4.The mRTIL was reacted with 2,2-bis(3,4-carboxylphenyl) hexafluoropropane dianhydride (6FDA) to produce 6FDA-RTIL oligomers. Two oligomers, one with 6.5 repeat units and another with 3.3 repeat units, were further reacted with 6FDA and m-phenylenediamine (MDA) where the compositions of RTIL ranged from 6.5 to 25.8 mol% to form block copolyimides. The diRTIL was successfully reacted with 6FDA and MDA and formed 6FDA-(MDA/diRTIL) random copolyimides with a concentration of diRTIL up to 30 mol%. An 8 mol% diRTIL based block copolyimide with an oligomer size of 9 repeat units was also synthesized. The separation performance of all RTIL based copolyimides followed a trade-off relationship and did not exhibit a significant improvement for CO2/CH4 gas pair. The incorporation of RTIL caused the change in the free volumes, free volume distributions of the copolyimides and did not increase the CO2 solubility of the polyimides. The increase in the RTIL mol% resulted in a decrease in molecular weight, 5% weight loss temperature, glass transition temperatures (Tg) and an increase in density. The long block copolyimides exhibited a higher d-spacing, fractional free volume (FFV) and specific free volume (SFV) than those of the short block copolyimides. The diRTIL based copolyimides exhibited smaller d-spacings, FFVs and SFVs with the increase in mol% of diRTIL. In addition, the 8 mol% diRTIL based block copolyimide exhibited a lower density, higher d-spacing, FFV and SFV than those of the 10 mol% random copolyimide. The RTIL monomers contain mor (open full item for complete abstract)

Committee: Maria Coleman Dr. (Committee Chair); Jared Anderson Dr. (Committee Member); Sasidhar Varanasi Dr. (Committee Member); Saleh Jabarin Dr. (Committee Member); Isabel Escobar Dr. (Committee Member) Subjects: Chemical Engineering; Chemistry

Master of Science, The Ohio State University, 2012, Chemical and Biomolecular Engineering

Increasing global population and demand for energy has raised concerns of excessive anthropogenic greenhouse gas emissions from consumption of fossil fuels. Coal, in particular, will continue to be the backbone energy source for the electricity generation. Coal-fired power plants are expected to contribute 33% of the domestic and 40% of the global CO2 emissions (EIA, 2010). In response to this global problem, the Environment Protection Agency (EPA) on March 27 of this year proposed the nation's first carbon pollution standard that would limit the amount of CO2 emissions from new power plants. The Clean Coal Research Group at The Ohio State University has developed an innovative high temperature technology –the Carbonation Calcination Reaction (CCR) process - that utilizes limestone sorbents to simultaneously remove the CO2 and SO2 from coal combustion flue gas. A 120 kWth sub-pilot scale CCR system has demonstrated the ability to capture greater than 90% CO2 and almost 100% SO2 from coal combustion flue gas. However, application of the CCR process on the industrial scale requires solid circulation rates on the order of thousands of tons per hour, in which case the gas-solid separation efficiency and sorbent recyclability become crucial issues that need to be addressed. This thesis addresses two critical parts of the CCR process – the particulate capture device and the hydrator. Two cyclones were designed and tested for their separation efficiency of fine Ca(OH)2 powder. The two cyclones in series design demonstrated exceptional capture efficiency during our cold model tests. Testing for its capture efficiency as part of the sub-pilot scale CCR system yielded over 99% efficiency for Ca(OH)2 powder with particle size distribution less than 10 ¿¿¿¿m. The current cyclone design provides a cost-effective way to control the gas-solid separation of the flue gas stream containing micro-size particles. In addition, a bench-scale high temperature hydrator was fabricated to (open full item for complete abstract)

Committee: Liang-shih Fan Dr. (Advisor); Jacques Zakin Dr. (Committee Member) Subjects: Chemical Engineering

Doctor of Philosophy, The Ohio State University, 2010, Aeronautical and Astronautical Engineering

A flow control scheme using endwall suction and vortex generator jet (VGJ) blowing was employed to reduce the turbine passage losses associated with the endwall flow field and midspan separation. Unsteady midspan control at low Re had a significant impact on the wake total pressure losses, decreasing the area-average losses by 54%. The addition of leading edge endwall suction resulted in an area-average total pressure loss reduction of 57%. The minimal additional gains achieved with leading edge endwall suction showed that the horseshoe vortex was a secondary contributor to endwall loss production (primary contributor- passage vortex). A similar flow control strategy was employed with an emphasis on passage vortex (PV) control. During the design, a theoretical model was used that predicted the trajectory of the passage vortex. The model required inviscid results obtained from two-dimensional CFD. It was used in the design of two flow control approaches, the removal and redirection approaches. The emphasis of the removal approach was the direct application of flow control on the endwall below the passage vortex trajectory. The redirection approach attempted to alter the trajectory of the PV by removing boundary layer fluid through judiciously placed suction holes. Suction hole positions were chosen using a potential flow model that emphasized the alignment of the endwall flow field with inviscid streamlines. Model results were validated using flow visualization and particle image velocimetry (PIV) in a linear turbine cascade comprised of the highly-loaded L1A blade profile. Detailed wake total pressure losses were measured, while matching the suction and VGJ massflow rates, for the removal and redirection approaches at ReCx=25000 and blowing ratio, B, of 2. When compared with the no control results, the addition of steady VGJs and endwall suction reduced the wake losses by 69% (removal approach) and 68% (redirection approach). The majority of the total pressure los (open full item for complete abstract)

Committee: Jeffrey Bons PhD (Advisor); James Gregory PhD (Committee Member); Jen-Ping Chen PhD (Committee Member); Mohammad Samimy PhD (Committee Member) Subjects: Engineering

Doctor of Philosophy, The Ohio State University, 2009, Chemistry

The growth of zeolite L membranes with controlled thicknesses in the sub-micron to micron region is examined. It was demonstrated that by controlling the concentration of the zeolite solid load and suspension viscosity, dip-coating provided a method to prepare zeolite seed layers of controlled thicknesses. Disk-shaped zeolite L crystals, with size distribution of 0.5-2 microns in diameter, were used as seed crystals for the growth of 2-7 micron thick membranes. For the synthesis of sub-micron sized membranes, seed crystals from 20-60 nanometers were used. The optimum secondary growth conditions was found to occur at 60 hours of growth time (40 hours for sub-micron membranes) using a temperature of 110°C with a solution composition of 10K2O:1Al2O3:20SiO2:2000H2O. Membranes were characterized by electron microscopy and single gas permeation studies, providing confirmation of membrane densification. Composite, defect-free membranes consisting of zeolite Y layers on the surface of microporous α-Al2O3 support disks were prepared using externally synthesized nanocrystalline and sub-micron crystals. Polycrystalline layers were formed by two different hydrothermal secondary growth procedures. Nanocrystalline zeolite Y seeded membranes were utilized as chemical sensors for the detection of chemical warfare agents. Sensor traces were established to show that despite the good membrane sensitivity to DMMP, sensor recovery times were too long for practical applications. Due to the ability of small molecules to pass one another inside the micropores of zeolites, two different zeolite Y membrane types were prepared from sub-micron crystallites to investigate their gas transport and separation properties. Single gas permeances for helium were determined in the temperature range of 30-130°C for both membrane types. The separation factors of equimolar mixtures of CO2 and N2 were measured at the same temperatures and at feed pressures from 1.4-4 bar. Both membrane types showed high s (open full item for complete abstract)

Committee: Prabir Dutta PhD (Advisor); Susan Olesik PhD (Committee Member); Patrick Woodward PhD (Committee Member); Rajendra Singh PhD (Committee Member) Subjects: Chemistry; Materials Science

Doctor of Philosophy, The Ohio State University, 2008, Chemical Engineering

Proton-exchange membrane fuel cells (PEMFCs) have become a very active research area for both mobile and stationary applications, particularly for fuel cell vehicles. Compared to inner combustion engines, PEMFCs can decrease pollution and increase the energy efficiency. New proton-exchange membrane (PEM) materials and new technologies for fuel processing are the most important and challenging parts in this research field.Nafion® and other perfluorinated sulfonic acid membranes are still the only commercial PEM materials so far. However, their high cost and low performance at high temperatures significantly limit their applications. In this research, new five-member ring and six-member ring soft segment-containing sulfonated polyimide (SPI)-based membranes and new sulfonated polybenzimidazole (SPBI)-based membranes were successfully synthesized. The resulting membranes could outperform Nafion® at various conditions, particularly at high temperatures and low relative humidities (RHs). Moreover, the new membrane materials should be much more cost-effective since the starting materials are more than two orders of magnitude less expensive than those for Nafion® membranes. In the research on fuel processing, amine carriers were successfully incorporated into the SPBI copolymer or the crosslinked poly(vinyl alcohol) (PVA) matrix, which could react reversibly with acid gases, such as CO2. Thus, the resulting membranes have shown very promising CO2 selectivity vs. the other gas molecules, such as H2 and CH4, by the facilitated transport mechanism. These newly synthesized membranes have many applications in the field of gas separations, including the low pressure synthesis gas purification for fuel cell applications, the high pressure synthesis gas purification for refinery industrial applications, and the high pressure natural gas purification to obtain high purity CH4.

Committee: W.S. Winston Ho PhD (Advisor); L. James Lee PhD (Committee Member); Kurt Koelling PhD (Committee Member); Isil Erel PhD (Committee Member) Subjects: Chemical Engineering; Energy; Polymers

Doctor of Philosophy, Case Western Reserve University, 1990, Macromolecular Science

Ultrathin Langmuir-Blodgett (LB) films were prepared using amphiphiles containing fluorocarbon side chains and hydrophilic spacer groups in the main chain to demonstrate their applicabilities as gas separation membranes. The solid substrates used for support included silicon wafers, hydrophobic microporous polypropylene films (Celgard 2400), and silicone rubber films. The pressure-area isotherms indicated that all the amphiphiles were able to self-organize into densely packed monolayers. The stability of the monolayer was evident by the lack of appreciable creep. The layer spacings of the fluorocarbon amphiphiles were determined by X-ray diffraction and Ellipsometry. The layer spacing increased with the copolymer concentration. The tilt of the fluorocarbon side chain was also evident in the measurements. The SEM photographs showed that the LB films of the fluorocarbon amphiphiles could bridge the pores of the Celgard 2400 support if the number of the LB layers was adequately high. A 50:50 mixture of CH4/CO2 was used for permeation experiments. While the homopolymers with no hydrophilic main chain showed no reduction in gas permeabilities, the copolymers with high monomer concentrations showed a good barrier ability due to the increase in interactions both between and within layers. A decrease in gas permeation with increasing number of the LB layers was observed. The gas permeability ratio of CO2 to CH4 was improved by coating the Celgard 2400 supported amphiphilic LB film with a layer of highly permeable but non-selective silicone rubber. The improvement in gas separation was attributed to the effective coverage of the micropores on the LB film by the silicone rubber coating. A model was developed to predict the permeation performance of the LB membranes with a laminated structure. The model correlated with gas permeability to the number, the thickness, and the porosity of the LB monolayers and the thickness of the coating material. The model predictions for CO2/CH (open full item for complete abstract)

Committee: Jerome Lando (Advisor) Subjects: Chemistry, Polymer

Doctor of Philosophy, Case Western Reserve University, 2013, Macromolecular Science and Engineering

Multilayer co-extrusion, a highly flexible and unique process, has enabled the study of the permeation, mechanical, and optical properties of multilayer films. Gas separation membranes are strongly dependent upon the permeation of specific gases, which is controlled by the polymer structure and morphology. Poly(ether block amide) (PEBA) thermoplastic elastomers have an inherently high permeability and good selectivity for acid gases such as CO2. A series of PEBA copolymers containing poly(tetramethylene oxide) and polyamide-12 was studied to explore the influence of mechanically induced orientation and copolymer composition on gas permeability and morphology. Upon orientation, PEBA copolymers with high polyether content exhibited up to 3.5x reduction in permeation with increasing strain as a result of strain induced crystallization. To maintain high flux for membrane applications, elastic recovery and thermal treatment proved beneficial in reversing the effects of uniaxial orientation on PEBA copolymers. Gas separation membranes were produced through co-extrusion and subsequent orientation of films containing PEBA as the selective material and PP composites as the support, which are made porous through two methods: 1) inorganic fillers or 2) crystal phase transformation. Two membrane systems, PEBA/(PP + CaCO3) and PEBA/¿-PP, maintained a high CO2/O2 selectivity while exhibiting reduced permeability. Incorporation of an annealing step either before or after orientation improves the membrane gas flux by 50 to 100 %. The improvement in gas flux was a result of either elimination of strain induced crystallinity, which increases the selective layer permeability, or improvement of the PP crystal structure, which may increase pore size in the porous support layer. Forced assembly multilayer co-extrusion of commercially available polyurethane (PU) and polycaprolactone (PCL) polymers was used to create a continuous periodic alternating layer architecture that exh (open full item for complete abstract)

Committee: Eric Baer (Advisor); LaShanda Korley (Committee Member); Lei Zhu (Committee Member); Kenneth Singer (Committee Member) Subjects: Engineering; Plastics; Polymers