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Description
The large-scale anthropogenic emission of carbon dioxide into the atmosphere leads to many unintended consequences, from rising sea levels to ocean acidification. While a clean energy infrastructure is growing, mid-term strategies that are compatible with the current infrastructure should be developed. Carbon capture and storage in fossil-fuel power plants is

The large-scale anthropogenic emission of carbon dioxide into the atmosphere leads to many unintended consequences, from rising sea levels to ocean acidification. While a clean energy infrastructure is growing, mid-term strategies that are compatible with the current infrastructure should be developed. Carbon capture and storage in fossil-fuel power plants is one way to avoid our current gigaton-scale emission of carbon dioxide into the atmosphere. However, for this to be possible, separation techniques are necessary to remove the nitrogen from air before combustion or from the flue gas after combustion. Metal-organic frameworks (MOFs) are a relatively new class of porous material that show great promise for adsorptive separation processes. Here, potential mechanisms of O2/N2 separation and CO2/N2 separation are explored.

First, a logical categorization of potential adsorptive separation mechanisms in MOFs is outlined by comparing existing data with previously studied materials. Size-selective adsorptive separation is investigated for both gas systems using molecular simulations. A correlation between size-selective equilibrium adsorptive separation capabilities and pore diameter is established in materials with complex pore distributions. A method of generating mobile extra-framework cations which drastically increase adsorptive selectivity toward nitrogen over oxygen via electrostatic interactions is explored through experiments and simulations. Finally, deposition of redox-active ferrocene molecules into systematically generated defects is shown to be an effective method of increasing selectivity towards oxygen.
ContributorsMcIntyre, Sean (Author) / Mu, Bin (Thesis advisor) / Green, Matthew (Committee member) / Lind, Marylaura (Committee member) / Arizona State University (Publisher)
Created2019
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Description
Global warming resulted from greenhouse gases emission has received widespread attention. Meanwhile, it is required to explore renewable and environmentally friendly energy sources due to the severe pollution of the environment caused by fossil fuel combustion. In order to realize a substantial adsorption process to resolve the environmental issues, the

Global warming resulted from greenhouse gases emission has received widespread attention. Meanwhile, it is required to explore renewable and environmentally friendly energy sources due to the severe pollution of the environment caused by fossil fuel combustion. In order to realize a substantial adsorption process to resolve the environmental issues, the development of new adsorbents with improved properties has become the most critical issue. This dissertation presents the work of four individual but related studies on systematic characterization and process simulations of novel adsorbents with superior adsorption properties.

A perovskite oxide material, La0.1Sr0.9Co0.9Fe0.1O3-δ (LSCF1991), was investigated first for high-temperature air separation. The oxygen sorption/desorption behavior of LSCF1991 was studied by thermogravimetric analysis (TGA) and fixed-bed breakthrough experiments. A parametric study was performed to design and optimize the operating parameters of the high-temperature air separation process by pressure swing adsorption (PSA). The results have shown great potential for applying LSCF1991 to the high-temperature air separation due to its excellent separation performance and low energy requirement.

Research on using nanostructured zeolite NaX (NZ) as adsorbents for CO2 capture was subsequently conducted. The CO2/N2 adsorption characterizations indicated that the NZ samples lead to enhanced adsorption properties compared with the commercial zeolites (MZ). From the two-bed six-step PSA simulation, NZ saved around 30% energy over MZ for CO2 capture and recovery while achieving a higher CO2 purity and productivity.

A unique screening method was developed for efficient evaluation of adsorbents for PSA processes. In the case study, 47 novel adsorbents have been screened for coal bed methane (CBM) recovery. The adsorbents went through scoring-based prescreening, PSA simulation, and optimization. The process performance indicators were correlated with the adsorption selectivity and capacities, which provides new insights for predicting the PSA performance.

A new medium-temperature oxygen sorbent, YBaCo4O7+δ (YBC114), was investigated as an oxygen pumping material to facilitate solar thermochemical fuel production. The oxygen uptake and release attributes of YBC114 were studied by both TGA and a small-scale evacuation test. The study proved that the particle size has a significant effect on the oxygen pumping behavior of YBC114, especially for the uptake kinetics.
ContributorsXu, Mai (Author) / Deng, Shuguang (Thesis advisor) / Lind, Marylaura (Committee member) / Lin, Jerry Y.S. (Committee member) / Green, Matthew D. (Committee member) / Seo, Dong-Kyun (Committee member) / Arizona State University (Publisher)
Created2020
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Description
Mixed-ionic electronic conducting (MIEC) oxides have drawn much attention from researchers because of their potential in high temperature separation processes. Among many materials available, perovskite type and fluorite type oxides are the most studied for their excellent oxygen ion transport property. These oxides not only can be oxygen adsorbent or

Mixed-ionic electronic conducting (MIEC) oxides have drawn much attention from researchers because of their potential in high temperature separation processes. Among many materials available, perovskite type and fluorite type oxides are the most studied for their excellent oxygen ion transport property. These oxides not only can be oxygen adsorbent or O2-permeable membranes themselves, but also can be incorporated with molten carbonate to form dual-phase membranes for CO2 separation.

Oxygen sorption/desorption properties of perovskite oxides with and without oxygen vacancy were investigated first by thermogravimetric analysis (TGA) and fixed-bed experiments. The oxide with unique disorder-order phase transition during desorption exhibited an enhanced oxygen desorption rate during the TGA measurement but not in fixed-bed demonstrations. The difference in oxygen desorption rate is due to much higher oxygen partial pressure surrounding the sorbent during the fixed-bed oxygen desorption process, as revealed by X-ray diffraction (XRD) patterns of rapidly quenched samples.

Research on using perovskite oxides as CO2-permeable dual-phase membranes was subsequently conducted. Two CO2-resistant MIEC perovskite ceramics, Pr0.6Sr0.4Co0.2Fe0.8 O3-δ (PSCF) and SrFe0.9Ta0.1O3-δ (SFT) were chosen as support materials for membrane synthesis. PSCF-molten carbonate (MC) and SFT-MC membranes were prepared for CO2-O2 counter-permeation. The geometric factors for the carbonate phase and ceramic phase were used to calculate the effective carbonate and oxygen ionic conductivity in the carbonate and ceramic phase. When tested in CO2-O2 counter-permeation set-up, CO2 flux showed negligible change, but O2 flux decreased by 10-32% compared with single-component permeation. With CO2 counter-permeation, the total oxygen permeation flux is higher than that without counter-permeation.

A new concept of CO2-permselective membrane reactor for hydrogen production via steam reforming of methane (SRM) was demonstrated. The results of SRM in the membrane reactor confirm that in-situ CO2 removal effectively promotes water-gas shift conversion and thus enhances hydrogen yield. A modeling study was also conducted to assess the performance of the membrane reactor in high-pressure feed/vacuum sweep conditions, which were not carried out due to limitations in current membrane testing set-up. When 5 atm feed pressure and 10-3 atm sweep pressure were applied, the membrane reactor can produce over 99% hydrogen stream in simulation.
ContributorsWu, Han-Chun (Author) / Lin, Jerry Y.S. (Thesis advisor) / Deng, Shuguang (Committee member) / Jiao, Yang (Committee member) / Emady, Heather (Committee member) / Muhich, Christopherq (Committee member) / Arizona State University (Publisher)
Created2020
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Description
Climate change poses a serious challenge humankind. Society’s reliance on fossil fuels raises atmospheric CO2 concentrations causing global warming. Already, the planet has warmed by 1.1 °C making it nearly impossible to heed the advice of the IPCC (2022) and prevent warming in excess of 1.5 °C by 2050. Even

Climate change poses a serious challenge humankind. Society’s reliance on fossil fuels raises atmospheric CO2 concentrations causing global warming. Already, the planet has warmed by 1.1 °C making it nearly impossible to heed the advice of the IPCC (2022) and prevent warming in excess of 1.5 °C by 2050. Even the current excess of CO2 in the atmosphere poses significant risks. Direct air capture (DAC) of CO2 offers one of the most scalable options to the drawdown of carbon. DAC can collect CO2 that is already diluted into the atmosphere for disposal or utilization. Central to most DAC are sorbents, i.e., materials that bind and release CO2 in a capture and release cycle. There are sorbents that cycle through a temperature swing. Others use a moisture swing, or a pressure swing or combinations of all of them. Since DAC is still a nascent technology, advancement of sorbents is an important part of DAC development. There is a nearly infinite combination of possible sorbents and form factors of sorbents that can be deployed in many different variations of DAC. Our goal is to develop a methodology for characterizing sorbents to facilitate rational choices among different options. Good sorbent characteristics include high capacity, fast sorption and desorption kinetics, low energy need for unloading, and longevity. This work presents the development of a systematic approach to evaluate sorbents from the milligram to tonne scale focusing on the important characteristics mentioned above. The work identified a good temperature swing sorbent whose characterization moved from the mg to kg scale without loss in performance. This work represents a first step in systematizing sorbent characterization for rational sorbent development programs.
ContributorsStangherlin Barbosa, Thiago (Author) / Lackner, Klaus (Thesis advisor) / Cirucci, John (Committee member) / Dirks, Gary (Committee member) / Arizona State University (Publisher)
Created2022
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Description
The cost of capturing carbon dioxide (CO2) from ambient air needs to be greatly reduced if it is to contribute significantly to mitigating climate change. Ion-exchange resin (IER) with quaternary ammonium cation binds CO2 when dry and releases it when wet without supplemental energy, making the process attractive for economical

The cost of capturing carbon dioxide (CO2) from ambient air needs to be greatly reduced if it is to contribute significantly to mitigating climate change. Ion-exchange resin (IER) with quaternary ammonium cation binds CO2 when dry and releases it when wet without supplemental energy, making the process attractive for economical Direct Air Capture (DAC). In this study, a design case basis was developed for a system of collectors capable of capturing 1000 tons/day of CO2 via moisture swing sorption. The model uses varying weather parameters such as temperature, wind speed, and relative humidity to understand the impact of weather on the sorbent loading, cycle time (capture and regeneration), and net water loss. Two independent isotherm models, namely Flory Huggins and the modified Langmuir isotherm model were used to estimate the water and CO2 loading of the resin respectively as a function of relative humidity. The capture model suggests a higher capture rate during the summer and daytime (in a diurnal cycle) as the relative humidity is lower. A design optimization model was developed to minimize the capture time and maximize the sorbent loading. The crude rate production and the net water loss can help conduct an economic analysis to determine the cost of carbon capture.
ContributorsTalha, Mohammad Abu (Author) / Green, Matthew (Thesis advisor) / Lackner, Klaus (Committee member) / Cirucci, John (Committee member) / Arizona State University (Publisher)
Created2023