Engineering Porous Organic Cages into Effective Separations Devices: Porous Liquids and Fiber Sorbents
Author(s)
Borne, Isaiah Hilton
Advisor(s)
Editor(s)
Collections
Supplementary to:
Permanent Link
Abstract
Climate change caused by anthropogenic CO2 emissions pose a critical threat to society. The increase in CO2 concentration from the combustion of fossil fuels must be addressed by capturing and sequestering the gas or using it as a feedstock for valuable chemicals. Cleaner energy sources like natural gas and hydrogen must be efficiently and effectively purified from CO2 to be widely used. CO2 capture and storage are typically achieved via the use of physical and chemical solvents, which are mature technologies that have been proven to work on the industrial level. Although these solvent-based gas separation systems are mature, they suffer from various issues like low gas capacities, high regeneration energies, and large operating units/capital costs. There has not been a major innovation in solvent-based gas separations in decades. Porous liquids present an opportunity to revolutionize the gas separations field.
Porous liquids imbue liquids with intrinsic microporosity that is typically associated with microporous solids. By dissolving discrete, porous materials in bulky solvents that cannot penetrate the pores, we can develop flowing liquids with intrinsic micropores. This dissertation details the development of porous organic cages engineering those materials into porous liquids. Three main objectives are addressed in this dissertation: 1) use fundamental thermodynamic properties help the characterization and development of Type II porous liquids, 2) determine the potential for porous liquids to be used in large-scale gas separations, and 3) engineer imine-based porous organic cages into materials that can withstand chemically harsh environments or mechanically stressful processes.
Work on the first objective showed two main results. First, we show that key thermodynamic experiments can be used to quickly characterize and understand fundamental properties of Type II porous liquids. DSC experiments and partial molar volume measurements are conducted to: 1) prove that porous organic cages can actually dissolve in bulky solvents to create porous solutions and 2) quickly determine if a candidate porous liquid is actually porous without doing expensive and time-intensive PALS experiments. Second, we show that computational tools can be used to accelerate the solvent selection for Type II porous liquids and the computational predictions are validated experimentally
In the second objective, a high-level techno-economic analysis is conducted to determine the potential of Type II porous liquids for gas separations. For a case study, we designed a process using a Type II porous liquid to separate concentrated CO2 from CH4. Porous liquids were shown to have lower capital costs and operating costs compared to current industrial physical solvents. The absorption efficiency of these materials were comparable to industrial standards as well. A major issue with the porous liquids is their cost and low selectivity compared to industrial standard solvents. This work presents design goals for future porous organic cages and Type II porous liquids, which should make these materials more effective for gas separations.
Lastly in the third objective, a reaction scheme is employed to imbue imine based porous organic cages with acid gas stability. In many situations where CO2 is present, there is also H2S and other acidic gases that can degrade separations materials and pose health threats to those exposed to it. The development of a new, highly soluble and acid gas stable porous organic cage is detailed along with preliminary work on engineering it into a Type II porous liquid. In addition to acid gas stability, we probe the mechanical and chemical stability of imine based porous organic cages by fabricating fiber sorbents embedded with porous organic cages. The porous organic cages are exposed to harsh solvents, high energy input, and mechanical stress to create fiber sorbents which can be used as solid adsorbents for gas separations. The porous organic cages retain their gas separation properties after the fiber spinning process, showing that these materials can withstand harsh conditions and still be useful for gas separations.
Sponsor
Date
2022-09-29
Extent
Resource Type
Text
Resource Subtype
Dissertation