Design and Modeling of Nanostructured Palladium-Based Hydrogen-Selective Membranes
Hydrogen and its isotopes are crucial in various fields, including established applications such as ammonia production to emerging applications such as energy storage, transportation fuel, and nuclear fusion. The emerging applications are projected to grow exponentially, making the separation of hyd...
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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/1721.1/155597 |
| _version_ | 1826210220621168640 |
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| author | Kim, Lohyun |
| author2 | Karnik, Rohit N. |
| author_facet | Karnik, Rohit N. Kim, Lohyun |
| author_sort | Kim, Lohyun |
| collection | MIT |
| description | Hydrogen and its isotopes are crucial in various fields, including established applications such as ammonia production to emerging applications such as energy storage, transportation fuel, and nuclear fusion. The emerging applications are projected to grow exponentially, making the separation of hydrogen from other gases a critical step in meeting some of these growing needs. This thesis focuses on the separation needs for nuclear fusion and decalin dehydrogenation.
Nuclear fusion reactors such as the one being developed by MIT and Commonwealth Fusion Systems generate energy through the fusion of hydrogen isotopes (deuterium and tritium). However, due to the scarcity of tritium, minimizing the amount of tritium inventory and recycling of tritium is essential to achieve fuel self-sufficiency and scale up fusion. This process requires the separation of fuel gases from helium, a major byproduct of fusion reactions. Pd-based membranes, recognized for high permeance and selectivity, offer a promising solution for this separation with minimal energy, cost, and footprint. However, these membranes have not yet been tailored for nuclear fusion applications. There are no comprehensive models explaining the transport of hydrogen isotope mixtures through Pd, and Pd membranes can be damaged by helium embrittlement caused by tritium decay and operate in a limited temperature range of ~600-700 K that places constraints on design given the high temperatures of the reactor exhaust, and molten salt blanket (~1000 K).
This thesis aims to develop Pd-based membranes for nuclear fusion for the removal of helium and recycling of deuterium and tritium. The first objective is to develop an integrated hydrogen multicomponent transport model for Pd membranes. Building on this understanding, the next aim is to design nanostructured Pd composite membranes that can remain stable at temperatures of 1000 K and allow for migration of defects due to radiation or helium entrapment to interfaces.
The transport model for hydrogen isotope mixtures via Pd membrane was developed based on the solution-diffusion mechanism. The model additionally accounts for isotopic interactions during transport and all major kinetic steps, including surface reaction and bulk diffusion. The model predictions exhibited good agreement with various empirical measurements in the literature and in the laboratory, validating its accuracy. This model can be integrated with a flow resistance circuit, enabling the identification of major transport mechanisms and potential behavior of various Pd-based membranes.
Considering the potential operating conditions in the reactor, three types of Pd composite membranes were developed: Pd film, Pd islands, and Pd plug membranes. An ultrathin Pd film membrane was developed by integrating a graphene layer acting as a flexible intermediate layer. The membrane demonstrated a reversible change of gas flow rate by a factor of ~10 in response to hydrogen, attributed to a reversible phase transition of Pd in the presence of hydrogen, implying potential uses for gas sensing and flow control. A membrane with densely-packed Pd islands on graphene was developed using a new fabrication method and exhibited excellent thermal resistance at 1000 K for 100 hours owing to the isolated nature of the islands. Finally, a Pd plug membrane was developed by creating isolated plugs inside the pores of the support layer. The membrane showed hydrogen permeance of ~1⨉10-7 mol/m2·s·Pa at a temperature of 800 K. The permeance of helium and nitrogen was similar to the baseline leakage of the gas module, indicating negligible leakage of the membrane. By implementing the transport model, the lower bound of hydrogen selectivity against helium was estimated to be ~150 at 800 K. The membrane showed stable performance at 800 K for 100 h.
A second application is the dehydrogenation of decalin, a promising cycloalkane that serves as an effective source and liquid mobile carrier for hydrogen. Dehydrogenation reactions are also important in petrochemical refining. The dehydrogenation process, typically occurring at 500 K, produces hydrogen mixed with decalin, tetralin and naphthalene, with a low yield necessitating an effective separation process. Compared to current thermal separation methods, integrating membrane technology with the dehydrogenation process can significantly enhance hydrogen production and separation. Nanoporous graphene membranes, notable for their high permeance and selectivity due to atomic thickness and size-selective pores, are particularly promising. This thesis explored the use of nanoporous graphene membranes for separating hydrogen from a mixture of decalin isomers and tetralin at 500 K. The graphene exhibited hydrogen permeance 1000 times higher than typical polymeric membranes, and its size-selective pores enabled much higher hydrogen selectivity compared to Knudsen selectivity. The membrane maintained stable performance at 500 K for 40 days, demonstrating its outstanding thermal stability. The different permeances between decalin isomers and tetralin suggest complex impacts of surface interactions and diffusion across the graphene layer.
In conclusion, this thesis developed new composite membranes with Pd and graphene, designed for nuclear fusion reactors and the decalin dehydrogenation process. Empirical and theoretical analyses confirmed their stable and outstanding performance under unique operational conditions. This research facilitates the integration of these advanced membranes into both applications, promising advancements in hydrogen-selective membrane technology. |
| first_indexed | 2024-09-23T14:46:22Z |
| format | Thesis |
| id | mit-1721.1/155597 |
| institution | Massachusetts Institute of Technology |
| last_indexed | 2024-09-23T14:46:22Z |
| publishDate | 2024 |
| publisher | Massachusetts Institute of Technology |
| record_format | dspace |
| spelling | mit-1721.1/1555972024-07-11T03:15:52Z Design and Modeling of Nanostructured Palladium-Based Hydrogen-Selective Membranes Kim, Lohyun Karnik, Rohit N. Massachusetts Institute of Technology. Department of Mechanical Engineering Hydrogen and its isotopes are crucial in various fields, including established applications such as ammonia production to emerging applications such as energy storage, transportation fuel, and nuclear fusion. The emerging applications are projected to grow exponentially, making the separation of hydrogen from other gases a critical step in meeting some of these growing needs. This thesis focuses on the separation needs for nuclear fusion and decalin dehydrogenation. Nuclear fusion reactors such as the one being developed by MIT and Commonwealth Fusion Systems generate energy through the fusion of hydrogen isotopes (deuterium and tritium). However, due to the scarcity of tritium, minimizing the amount of tritium inventory and recycling of tritium is essential to achieve fuel self-sufficiency and scale up fusion. This process requires the separation of fuel gases from helium, a major byproduct of fusion reactions. Pd-based membranes, recognized for high permeance and selectivity, offer a promising solution for this separation with minimal energy, cost, and footprint. However, these membranes have not yet been tailored for nuclear fusion applications. There are no comprehensive models explaining the transport of hydrogen isotope mixtures through Pd, and Pd membranes can be damaged by helium embrittlement caused by tritium decay and operate in a limited temperature range of ~600-700 K that places constraints on design given the high temperatures of the reactor exhaust, and molten salt blanket (~1000 K). This thesis aims to develop Pd-based membranes for nuclear fusion for the removal of helium and recycling of deuterium and tritium. The first objective is to develop an integrated hydrogen multicomponent transport model for Pd membranes. Building on this understanding, the next aim is to design nanostructured Pd composite membranes that can remain stable at temperatures of 1000 K and allow for migration of defects due to radiation or helium entrapment to interfaces. The transport model for hydrogen isotope mixtures via Pd membrane was developed based on the solution-diffusion mechanism. The model additionally accounts for isotopic interactions during transport and all major kinetic steps, including surface reaction and bulk diffusion. The model predictions exhibited good agreement with various empirical measurements in the literature and in the laboratory, validating its accuracy. This model can be integrated with a flow resistance circuit, enabling the identification of major transport mechanisms and potential behavior of various Pd-based membranes. Considering the potential operating conditions in the reactor, three types of Pd composite membranes were developed: Pd film, Pd islands, and Pd plug membranes. An ultrathin Pd film membrane was developed by integrating a graphene layer acting as a flexible intermediate layer. The membrane demonstrated a reversible change of gas flow rate by a factor of ~10 in response to hydrogen, attributed to a reversible phase transition of Pd in the presence of hydrogen, implying potential uses for gas sensing and flow control. A membrane with densely-packed Pd islands on graphene was developed using a new fabrication method and exhibited excellent thermal resistance at 1000 K for 100 hours owing to the isolated nature of the islands. Finally, a Pd plug membrane was developed by creating isolated plugs inside the pores of the support layer. The membrane showed hydrogen permeance of ~1⨉10-7 mol/m2·s·Pa at a temperature of 800 K. The permeance of helium and nitrogen was similar to the baseline leakage of the gas module, indicating negligible leakage of the membrane. By implementing the transport model, the lower bound of hydrogen selectivity against helium was estimated to be ~150 at 800 K. The membrane showed stable performance at 800 K for 100 h. A second application is the dehydrogenation of decalin, a promising cycloalkane that serves as an effective source and liquid mobile carrier for hydrogen. Dehydrogenation reactions are also important in petrochemical refining. The dehydrogenation process, typically occurring at 500 K, produces hydrogen mixed with decalin, tetralin and naphthalene, with a low yield necessitating an effective separation process. Compared to current thermal separation methods, integrating membrane technology with the dehydrogenation process can significantly enhance hydrogen production and separation. Nanoporous graphene membranes, notable for their high permeance and selectivity due to atomic thickness and size-selective pores, are particularly promising. This thesis explored the use of nanoporous graphene membranes for separating hydrogen from a mixture of decalin isomers and tetralin at 500 K. The graphene exhibited hydrogen permeance 1000 times higher than typical polymeric membranes, and its size-selective pores enabled much higher hydrogen selectivity compared to Knudsen selectivity. The membrane maintained stable performance at 500 K for 40 days, demonstrating its outstanding thermal stability. The different permeances between decalin isomers and tetralin suggest complex impacts of surface interactions and diffusion across the graphene layer. In conclusion, this thesis developed new composite membranes with Pd and graphene, designed for nuclear fusion reactors and the decalin dehydrogenation process. Empirical and theoretical analyses confirmed their stable and outstanding performance under unique operational conditions. This research facilitates the integration of these advanced membranes into both applications, promising advancements in hydrogen-selective membrane technology. Ph.D. 2024-07-10T20:17:24Z 2024-07-10T20:17:24Z 2024-05 2024-06-13T16:43:47.939Z Thesis https://hdl.handle.net/1721.1/155597 In Copyright - Educational Use Permitted Copyright retained by author(s) https://rightsstatements.org/page/InC-EDU/1.0/ application/pdf Massachusetts Institute of Technology |
| spellingShingle | Kim, Lohyun Design and Modeling of Nanostructured Palladium-Based Hydrogen-Selective Membranes |
| title | Design and Modeling of Nanostructured Palladium-Based Hydrogen-Selective Membranes |
| title_full | Design and Modeling of Nanostructured Palladium-Based Hydrogen-Selective Membranes |
| title_fullStr | Design and Modeling of Nanostructured Palladium-Based Hydrogen-Selective Membranes |
| title_full_unstemmed | Design and Modeling of Nanostructured Palladium-Based Hydrogen-Selective Membranes |
| title_short | Design and Modeling of Nanostructured Palladium-Based Hydrogen-Selective Membranes |
| title_sort | design and modeling of nanostructured palladium based hydrogen selective membranes |
| url | https://hdl.handle.net/1721.1/155597 |
| work_keys_str_mv | AT kimlohyun designandmodelingofnanostructuredpalladiumbasedhydrogenselectivemembranes |