Mixed-gas Transport in Microporous Polymer Derivatives for Energy-Efficient Gas Separations
Over the past forty years, membrane-based gas separations have emerged as a promising alternative to energy-intensive separation processes such as amine absorption and cryogenic distillation. However, a trade-off between permeability and selectivity as well as issues of decreased performance at high...
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| Format: | Thesis |
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Massachusetts Institute of Technology
2024
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| Online Access: | https://hdl.handle.net/1721.1/153404 |
| _version_ | 1826205399230971904 |
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| author | Mizrahi Rodriguez, Katherine |
| author2 | Smith, Zachary P. |
| author_facet | Smith, Zachary P. Mizrahi Rodriguez, Katherine |
| author_sort | Mizrahi Rodriguez, Katherine |
| collection | MIT |
| description | Over the past forty years, membrane-based gas separations have emerged as a promising alternative to energy-intensive separation processes such as amine absorption and cryogenic distillation. However, a trade-off between permeability and selectivity as well as issues of decreased performance at high pressures have hindered widespread membrane deployment. In response, there is a growing body of research aimed to developing materials formulations that address these polymer-specific disadvantages. Polymers of intrinsic microporosity (PIMs) were designed as ultrahigh-free-volume materials with inefficient chain packing and high surface areas, resulting in pure-gas performance beyond that of traditional glassy polymers. Hybrid systems such as mixed-matrix membranes (MMMs) also emerged as a means of increasing overall separation performance and reducing plasticization. Despite the surge in available material platforms for membrane-based separations, the performance and fundamental underpinnings of binary and ternary mixed-gas transport in these microporous polymers and MMMs remains underexplored.
This thesis combines synthetic chemistry, materials science, and chemical engineering to develop a platform of functionalized PIM derivatives and to investigate their pure- and mixed-gas transport properties in industrially relevant conditions. Approaches to increase diffusion-based performance in PIMs are developed, including methods to functionalize PIMs with carboxylic acid and amine functionalities, template free volume elements through protection/de-protection chemistries, and fabricate MOF–polymer composites. The effects of polymer functionalization, free volume manipulation, and membrane hybridization on transport are investigated via pure-gas testing and sorption–diffusion analysis, to elucidate structure–property relationships between polymer packing structure and gas diffusion. Polymers with identical backbone structures and varying backbone functionality are subsequently used as a platform to investigate the effects of CO₂ sorption affinity on the binary and ternary mixed-gas transport. Among the PIMs considered, amine-functionalized PIM-1 shows a notable increase in mixed-gas selectivity compared to the pure-gas case. The generalizability of this approach is investigated through aminefunctionalization of a different family of polymers, poly(aryl ether)s (PAEs). Results indicate that amine-functionalization can serve as a promising route to increase mixed-gas transport performance while also reducing CO₂-based plasticization. The influence of CO₂ sorption affinity on transport is finally investigated through ternary mixed-gas tests in toxic gas mixtures containing H₂S. Taken together, this thesis derives connections between macromolecular chemistry and complex gas transport performance in PIMs. By developing these structure-property-performance relationships, this work provides context for the potential of PIMs in industrial applications and rational design handles for future development of high-performing membrane solutions. |
| first_indexed | 2024-09-23T13:12:04Z |
| format | Thesis |
| id | mit-1721.1/153404 |
| institution | Massachusetts Institute of Technology |
| last_indexed | 2024-09-23T13:12:04Z |
| publishDate | 2024 |
| publisher | Massachusetts Institute of Technology |
| record_format | dspace |
| spelling | mit-1721.1/1534042024-01-25T03:31:06Z Mixed-gas Transport in Microporous Polymer Derivatives for Energy-Efficient Gas Separations Mizrahi Rodriguez, Katherine Smith, Zachary P. Massachusetts Institute of Technology. Department of Materials Science and Engineering Over the past forty years, membrane-based gas separations have emerged as a promising alternative to energy-intensive separation processes such as amine absorption and cryogenic distillation. However, a trade-off between permeability and selectivity as well as issues of decreased performance at high pressures have hindered widespread membrane deployment. In response, there is a growing body of research aimed to developing materials formulations that address these polymer-specific disadvantages. Polymers of intrinsic microporosity (PIMs) were designed as ultrahigh-free-volume materials with inefficient chain packing and high surface areas, resulting in pure-gas performance beyond that of traditional glassy polymers. Hybrid systems such as mixed-matrix membranes (MMMs) also emerged as a means of increasing overall separation performance and reducing plasticization. Despite the surge in available material platforms for membrane-based separations, the performance and fundamental underpinnings of binary and ternary mixed-gas transport in these microporous polymers and MMMs remains underexplored. This thesis combines synthetic chemistry, materials science, and chemical engineering to develop a platform of functionalized PIM derivatives and to investigate their pure- and mixed-gas transport properties in industrially relevant conditions. Approaches to increase diffusion-based performance in PIMs are developed, including methods to functionalize PIMs with carboxylic acid and amine functionalities, template free volume elements through protection/de-protection chemistries, and fabricate MOF–polymer composites. The effects of polymer functionalization, free volume manipulation, and membrane hybridization on transport are investigated via pure-gas testing and sorption–diffusion analysis, to elucidate structure–property relationships between polymer packing structure and gas diffusion. Polymers with identical backbone structures and varying backbone functionality are subsequently used as a platform to investigate the effects of CO₂ sorption affinity on the binary and ternary mixed-gas transport. Among the PIMs considered, amine-functionalized PIM-1 shows a notable increase in mixed-gas selectivity compared to the pure-gas case. The generalizability of this approach is investigated through aminefunctionalization of a different family of polymers, poly(aryl ether)s (PAEs). Results indicate that amine-functionalization can serve as a promising route to increase mixed-gas transport performance while also reducing CO₂-based plasticization. The influence of CO₂ sorption affinity on transport is finally investigated through ternary mixed-gas tests in toxic gas mixtures containing H₂S. Taken together, this thesis derives connections between macromolecular chemistry and complex gas transport performance in PIMs. By developing these structure-property-performance relationships, this work provides context for the potential of PIMs in industrial applications and rational design handles for future development of high-performing membrane solutions. Ph.D. 2024-01-24T19:28:52Z 2024-01-24T19:28:52Z 2022-05 2024-01-16T18:28:17.922Z Thesis https://hdl.handle.net/1721.1/153404 In Copyright - Educational Use Permitted Copyright MIT http://rightsstatements.org/page/InC-EDU/1.0/ application/pdf Massachusetts Institute of Technology |
| spellingShingle | Mizrahi Rodriguez, Katherine Mixed-gas Transport in Microporous Polymer Derivatives for Energy-Efficient Gas Separations |
| title | Mixed-gas Transport in Microporous Polymer Derivatives for Energy-Efficient Gas Separations |
| title_full | Mixed-gas Transport in Microporous Polymer Derivatives for Energy-Efficient Gas Separations |
| title_fullStr | Mixed-gas Transport in Microporous Polymer Derivatives for Energy-Efficient Gas Separations |
| title_full_unstemmed | Mixed-gas Transport in Microporous Polymer Derivatives for Energy-Efficient Gas Separations |
| title_short | Mixed-gas Transport in Microporous Polymer Derivatives for Energy-Efficient Gas Separations |
| title_sort | mixed gas transport in microporous polymer derivatives for energy efficient gas separations |
| url | https://hdl.handle.net/1721.1/153404 |
| work_keys_str_mv | AT mizrahirodriguezkatherine mixedgastransportinmicroporouspolymerderivativesforenergyefficientgasseparations |