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- All Subjects: Carbon Capture
- Creators: Dirks, Gary
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 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.
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
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 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