The Development of CO2-Switchable Technologies For Separation of Organic Compounds
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The increasing environmental impact of society has created the need for the modification of current and the implementation of new industrial processes which are less environmentally harmful. However, these new or modified processes must be less material-, time-, and cost-intensive such that they are more economically beneficial than the processes they are to supplant. The described research was inspired by these two ideas and is comprised of two projects, both focused on the creation of recyclable, CO2-switchable methods of separating organic compounds. The development and optimization of switchable water, a CO2-switchable ionic strength aqueous solvent is described. The solvent system, an amine/aqueous mixture, had the ability to switch from low to high ionic strength via the application and removal of CO2. This solvent system was able to achieve salting-out of water-miscible organics in comparable amounts to several inorganic salts typically used for salting-out. The switchable water system was explored for use in several industrial applications. A homogeneous catalysis recycling system was developed for the hydroformylation of styrene. A catalyst was able to be recovered and recycled five times with minimal loss of activity. The use of switchable water to expedite the settling of clay suspensions was also explored. Switchable water, when used as process water did not settle bulk clay solids as quickly as a CO2-only treatment, but did however increase the settling rate of small clay fines resulting in lower turbidities of the supernatant. The solvent could be recovered from settled clay suspensions and recycled up to three times. Finally, efforts towards the realization of CO2-switchable chiral resolving agents are presented. It is hypothesized that chiral nitrogenous bases could be used as switchable resolving agents by forming diastereomeric salt pairs with racemic alcohols via the application of CO2. After separation of the diastereomers, removal of CO2 would afford the resolved alcohol enantiomers and the chiral base. Efforts towards the synthesis of a library of chiral nitrogenous bases and the screening of their reactivity with CO2-treated alcohols are described. Several bases were generated, but the necessary reactivity between the bases and the racemic alcohols in the presence of CO2 was not observed.