Organizational Unit:

School of Chemical and Biomolecular Engineering

Permanent Link

https://hdl.handle.net/1853/70759

Parent Organization

Organizational Unit

College of Engineering

ArchiveSpace Name Record

https://finding-aids.library.gatech.edu/agents/corporate_entities/407

Full item page

Publication Search Results

Now showing 1 - 10 of 55

Analyzing Sorption Exclusion Effects for the CO2/CH4 Gas Pair Using Matrimid® CMS Dense Films

(Georgia Institute of Technology, 2023-07-31) Vessel, Taylor C.

This thesis uses the so-called dual-mode sorption model to analyze Matrimid® polyimide-derived carbon molecular (CMS) thin films. This model provides a useful framework to analyze and understand sorption in complex CMS morphology. The model is also helpful to connect morphology to the pyrolysis process used to create it. The dual mode model includes coexisting continuous and dispersed Langmuir terms. The model parameters related to these environments are reported and discussed in this work. CMS based membranes have been applied towards many different gas-pair separations. CMS thin films have appealing separation performance for key gas pairs; the carbon dioxide/methane pair, which is practically important, is the focus of this study. Previous measurements on CMS film sorption for this pair have been done. Surprisingly, applying the dual-mode sorption model to such thin films created from Matrimid® over a range of pyrolysis temperatures has not been done previously and is considered here. This thesis characterizes sorption properties of such CMS thin films for the CO2./CH4 pair and adds insights relevant to their separation. Suggestions for the next steps to extend this study are also provided.
Rechargeable Zn-Based Batteries for Large Scale Energy Storage: Operando Imaging, Material Designing and Device Engineering

(Georgia Institute of Technology, 2020-11-19) Wu, Yutong

Energy storage technologies have the potential to change the energy infrastructure from relying heavily on fossil fuels to mostly using temporally intermittent renewable energy sources. Lithium-ion battery is the dominant energy storage solution for portable electronics, but have safety concerns stemming from flammable organic electrolytes, which is more severe when batteries are scaled up for applications in electric vehicles and utilities. And due to the stacked powder-film-on-current-collector geometry, lithium-ion batteries have limitations in scalability and maintainability. Batteries using aqueous electrolyte (e.g. Zn-air) are intrinsically safe, and flow batteries (e.g. Zn-Br) are attractive choice for large scale energy storage. However, these two technologies (Zn-air and Zn-Br) have problems such as rechargeability, self-discharge, and power density. This research identifies the limiting factors of both portable and large-scale batteries, especially zinc-based ones, and innovate at the material and device levels to overcome these limitations. Specifically, Section 1 introduces the background and motivation of this research. Section 2 identifies the root cause for irreversible electrochemical reaction of Zn anode, namely passivation and dissolution, and leverage nanoscale materials design to address these problems. Section 3 develops an in situ visualization platform for studying Br electrochemistry in Zn-Br batteries. Phenomena such as phase separated Br2 formation, self-discharge, and phase change of Br2 product will be imaged, to bridge the gap between electrolyte composition and electrochemical performance. Section 4 uses a hollow fiber based flow battery geometry design to significantly enhance the volumetric power density. The device is universal, scalable, and not limited to electrolyte types. Section 5 provides a conclusion to this research and provides future directions. The outcomes of this research (e.g. in operando imaging platform, design principle of reversible metal anode, high power density electrochemical reactor) provides insights for portable scale and grid scale energy storages and other electrochemical flow devices. To note that the videos in this work is in .avi format.
Structure and stability of carbon molecular sieve membranes derived from 6FDA:BPDA-dam precursors

(Georgia Institute of Technology, 2020-07-24) Hays, Samuel

Carbon molecular sieve (CMS) membranes are an advanced class of membrane materials useful for many different gas-pair separations. One drawback of CMS membranes, as with many membranes, is a tendency for performance to decrease over time, termed physical aging. This work sheds light on the physical mechanism controlling physical aging in polyimide-derived CMS membranes and explores several techniques to minimize the effects.
Transition metal-containing carbon molecular sieve membranes for advanced olefin/paraffin separations

(Georgia Institute of Technology, 2017-07-21) Chu, Yu-Han

In this work, carbon molecular sieve (CMS) dense film membranes derived from 6FDA-DAM:DABA (3:2) polyimide precursor were studied for separation of mixed olefins (C2H4 and C3H6) from paraffins (C2H6 and C3H8). Olefin-selective CMS membranes with high performance can be made by pyrolysis of metal-containing polymeric precursors. Pyrolyzed at 550°C with a fast ramp rate, CMS membranes with integrated Fe2+ (2.2 wt% in the precursor) showed 19% higher C2H4/C2H6 and 11% higher C3H6/C3H8 sorption selectivity than that of the neat CMS membrane. Additional investigations with a quaternary mixture feed (C2 and C3 hydrocarbons) show that C2H4 permeability above 10 Barrers with C2H4/C2H6 permselectivity near 11 were achieved for the 3.2 wt% Fe loading case. Although Fe incorporation did not appear to promote C3H6/C2H6 permselectivity, Fe is useful to achieve impressive C2 pair olefin/paraffin separation. Deconvolution of the C2H4/C2H6 permselectivity for the more extensively studied 2.2 wt% loading case was also revealing. While both sorption and diffusion selectivity increased due to the Fe incorporation, a larger influence is seen on the diffusion selectivity versus the sorption selectivity. This added diffusion selectivity was dominated by a contribution from an entropic factor with Fe, which is the feature for CMS materials to surpass conventional polymer membranes.
Hybrid fiber sorbents for odorant removal from pipeline natural gas

(Georgia Institute of Technology, 2017-06-27) Chen, Grace

Pipeline natural gas is typically odorized with about 10 ppm of mercaptans for safety purposes in case of a leak. However, when burned in air inside of gas turbines, these sulfur compounds react with alkali material present in air to form a corrosive combustion product which corrodes the inside of the turbine and reduces its efficiency and lifetime. It is therefore of interest to remove mercaptan odorants from pipeline natural gas before introduction into combustion turbines for the purposes of preventing or delaying corrosion associated with SOx production. The overall goal of the current project was to investigate several metal organic frameworks (MOFs) and zeolites for the removal of a common odorant, t-butyl mercaptan (TBM), from natural gas and to evaluate their ability to be practically and economically integrated into a cyclic adsorption system in a fiber module configuration. Several MOFs were synthesized and characterized for TBM adsorption capacity, selectivity, cyclic regenerability, and stability, and compared to benchmark zeolites using gravimetric sorption methods. These aspects are important to the economic viability of a TBM removal system. Results showed that MOFs can be advantageous over zeolites for this application, and the highest performing materials were chosen for further studies with fiber spinning. The materials were incorporated into hybrid cellulose acetate polymer fibers and their adsorption performances were reevaluated gravimetrically and in an automated temperature swing adsorption (TSA) system. Both MOF and zeolite hybrid fibers were successfully fabricated with high sorbent loadings, and continued to exhibit high sorption capacities and selectivities to TBM in the model natural gas flow, while remaining stable to multiple temperature swing regeneration cycles. Different operating conditions were varied in the TSA system to determine their effects on the breakthrough curve, adsorption capacity, and mass transfer. The overall results demonstrate a proof of concept that fiber sorbent creation and implementation is feasible and worth further investigation for odorant removal from pipeline natural gas in an industrial setting. This research ties together to the two major challenges in adsorption applications: materials design and system implementation, which pushes forward the development of an industrial scale system for odorant removal from natural gas.
Tuning carbon molecular sieve membrane performance for challenging gas separations

(Georgia Institute of Technology, 2017-04-05) Wenz, Graham Benjamin

Membranes are emerging as tools for energy efficient alternatives to thermally-driven phase-changed based gas separations. As direct replacement of traditional separation processes with membrane-based processes is currently not feasible due to the low separation efficiency of current membrane materials, development of advanced membrane materials is of significant interest. Carbon molecular sieve (CMS) membranes have emerged as a new material that can surpass the polymer productivity-selectivity “upper bound”. As CMS membranes are commonly formed by the high temperature pyrolysis of polymeric precursors, they are uniquely situated for translation from lab-scale academic materials, to applications in large-scale industrial gas separation processes. Furthermore, the bimodal pore size distribution present in CMS materials results in an attractive combination of productivity and exquisite size and shape selectivity. However, deeper fundamental knowledge of the complex amorphous CMS microstructure is desired to facilitate directed engineering of separation performance of CMS membranes for challenging gas separations. This work focuses on advancement of the fundamental understanding of CMS membranes by investigation of various formation and post-synthetic treatments and their effects on gas transport. While this work focused on modification of CMS membranes derived from the high performance 6FDA:BPDA-DAM(1:1) polyimide precursor, the framework developed allows for extension to CMS materials derived from different precursors or formation conditions.
Effect of aggressive gas on separation properties of carbon molecular sieve hollow fiber membranes

(Georgia Institute of Technology, 2016-01-15) Karwa, Shweta

A practical membrane separation process is considered in this study for removal of CO2 from natural gas in the presence of H2S. Carbon molecular sieve (CMS) materials derived from Matrimid® and 6FDA:BPDA-DAM have been used for this particular separation. Optimization of V-treatment for CMS has been done in this study to prevent collapse of the substructure of polymer hollow fibers upon pyrolysis. Most importantly, this treatment was proven that this method is scalable. Details of interaction of H2S with CMS membranes were also clarified in this work and found to be different for CMS starting from different precursors. In addition to the measured changes in transport performance, analytical characterization techniques proved that H2S conditions CMS membranes by chemical interaction. The H2S conditioning led to a permanently reduced permeance through the CMS membrane, thereby making the membrane less attractive for industrial use. To prevent this poisoning, a novel method, called chlorine fixation, for neutralizing the reactive edges of the CMS was explored. The study has benchmarked the performance of CMS membranes in a sour gas feed. This work has established a framework for providing a potentially practical hollow fiber membrane technology for aggressive gas separation.
Characterization and use of pollen as a biorenewable filler for polymer composites

(Georgia Institute of Technology, 2015-04-06) Fadiran, Oluwatimilehin Olutayo

Fillers are often incorporated in polymer matrices in order to improve cost, mechanical, thermal, and transport properties. This work explores the hypothesis that pollen, a natural particle, has the potential to be an effective biorenewable reinforcing filler due to its unique surface architectures, high strength, chemical stability, and low density. Pollens from sources such as ragweed plants are ubiquitous natural materials that are based on sustainable, non-food resources. Pollen is a remarkable example of evolutionary-optimized microscale particle with structures and/or chemistries tailored for effective adhesion to a variety of surfaces and protection of genetic material under different dynamic and environmental conditions. The pollen shell is perhaps the most chemically resistant naturally occurring material. As many pollens achieve pollination simply by being carried by wind, they are very light-weight. These properties make pollen an attractive option as a natural filler for polymers. This research aims to characterize pollen interfacial properties and utilize pollen as an effective reinforcing filler in polymer materials. In this work, interfacial properties are characterized using Fourier transform infrared spectroscopy (FTIR), the BET method, and inverse liquid chromatography (ILC). These techniques were useful in determining the effect of surface treatments and further chemical modifications on pollen interfacial properties. Characterizing these properties allowed for improved understanding and utilization of pollen as a filler by revealing the enhanced surface interactions and surface properties of acid-base treated pollens when compared to as received untreated pollens. Epoxy and polyvinyl acetate (PVAc) matrices were used to demonstrate the effectiveness of pollen as a filler, as a function of pollen loading and surface treatments/chemical modifications. Scanning electron microscopy (SEM) was used to determine interfacial morphology, a high throughput mechanical characterization device (HTMECH) was used to determine mechanical properties, and differential scanning calorimetry (DSC) was used to determine glass transition behavior. In epoxy, pollen was an effective load bearing filler only after modifying its surface with acid-base hydrolysis. In PVAc, pollen was an effective load bearing filler only after an additional functionalization with a silane coupling agent. Finally, the species of pollen incorporated in PVAc matrices was varied in order determine the effect of the size of surface nano- and micro- structures on wetting, adhesion, and composite properties. Composites containing pollen displayed enhanced wetting and interfacial adhesion when compared to composites with smooth silica particles. Additionally, it was observed that pollen with smaller surface structures were wetted more effectively by the polymer matrix than pollen with larger structures. However, mechanical properties did not suggest significant changes in interfacial adherence with varied pollen microstructure size. The results of this work highlight the feasibility and potential of utilizing pollen as a natural filler for creating high strength, light-weight polymer composites with sustainable filler.
Fundamentals of transport in poly(ethylene terephthalate) and poly(ethylene furanoate) barrier materials

(Georgia Institute of Technology, 2015-04-03) Burgess, Steven K.

The increasing use of polymeric materials in food packaging applications is due to many factors; however, most are related to cost. While poly(ethylene terephthalate) (PET) is currently the industry standard for soft-drink bottles, more stringent requirements on the barrier properties to oxygen are needed for PET to expand further into more demanding markets (i.e., juice, etc). The current work examines the fundamental oxygen and carbon dioxide permeation and sorption properties of amorphous, caffeine antiplasticized PET and amorphous poly(ethylene furanoate) (PEF), which is a new biologically sourced polyester that exhibits significantly enhanced performance compared to petroleum-sourced PET. The fundamental transport data reported herein at 35°C illustrate that amorphous PEF exhibits significant reductions in permeability for oxygen (11X), carbon dioxide (19X), and water (2X) compared to amorphous PET. Such impressive barrier enhancements are unexpected since PEF exhibits a higher free volume compared to PET. Further investigation into the fundamental chain motional processes which contribute to penetrant diffusion, as probed via dynamic mechanical and solid-state NMR methods, reveals that the polymer ring-flipping motions in PEF are largely suppressed compared to those for PET. Such behavior allows for rationalization of the reduced transport properties compared to PET. Additional characterization techniques (i.e., thermal, mechanical, density, etc.) are used to develop a more complete understanding of PEF and caffeine antiplasticized PET, with the ultimate goal of relating these properties to penetrant transport.
Amine-functionalized polymeric hollow fiber sorbents for post-combustion CO₂ capture

(Georgia Institute of Technology, 2015-01-12) Li, Fuyue

Polymeric hollow fiber sorbents were functionalized with amine moieties for improving the carbon dioxide sorption capacity from flue gas to reduce the greenhouse gas emissions from coal-fired power plants. Three different experimental pathways were studied to form the amine-functionalized hollow fiber sorbents. Aminosilane functionalized cellulose acetate (CA) fibers, polyethyleneimine (PEI) functionalized polyamide-imide (PAI, Torlon® fibers and PEI post-infused and functionalized Torlon®-silica fibers were formed. CO₂ equilibrium sorption capacity data were collected by using the pressure decay sorption cell and thermal gravimetric analyzer. Other physio-chemical properties of the amine-functionalized fiber sorbents were characterized by using fourier-transform infrared spectroscopy, elemental analysis, and scanning electronic microscopy. Different reaction conditions were studied on the effect of sorption isotherms. Aminosilane-CA fibers were the first proof-of-concept for forming the amine functionalized polymer hollow fibers. PEI-PAI fibers were designed as a new method to reach enhanced sorption capacities than Aminosilane-functionalized CA fibers. PEI post-infused and functionalized Torlon®-silica fibers have further enhanced sorption capacity; however they easily degrade with similar reaction for forming PEI-PAI fibers. Lumen-side barrier layers were created successfully via post-treatment technique of using the crosslinked Neoprene® polymer onto PEI-functionalized PAI fibers. PEI-functionalized PAI fibers also have good cyclic stability and low heat of sorption.