Date of Award

12-2023

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry and Chemical Engineering

First Advisor

M. Toufiq Reza

Second Advisor

Maria E. Pozo de Fernandez

Third Advisor

Manolis M. Tomadakis

Fourth Advisor

Nasheen Nur

Abstract

Greenhouse gas (GHG) capture is a fundamental technology in the fight against climate change. Some species of devastating GHGs like fluorinated compounds are released directly to the air from industrial processes. Some GHGs are co-produced in sustainably derived biofuels which require absorptive upgrading. The development of more efficient, cost effective, and environmentally friendly methods of capturing GHG’s from pollutant sources and industrial streams is of utmost importance in the fight against climate change. Deep eutectic solvents have entered the separations stage as potential disruptors to conventional solvent choices for a variety of applications. Deep eutectic solvents (DES) are compounds of a hydrogen bond donor (HBD) and a hydrogen bond acceptor (HBA) that contain a depressed melting point compared to their individual constituents. These solvents are generally described as room temperature green tunable solvents. This dissertation explores the thermodynamic potential of DES-GHG systems for their use as absorbents. Through examination of the various combinations of DES’s a mechanistic understanding is developed which offers insights into which solvent components work best for a given application and why. The applications include absorption of fluorinated GHG R-32, CO2 capture from biogas and the effects impurities have on the system, siloxane capture as an inhibitor to CO2 uptake and biogas utilization, use of DES in upgrading model syngas systems, and the procedure required to make thermodynamic predictive software (COSMO-RS) accurate for studying more exotic systems of R-134a.

For each outlined topic a host of DES candidates from the type 3 or type 5 database was studied dependent upon the solutes energetic structure as computed through Turbomole software using density functional theory. A search for novel DES combinations and compositions was undertaken through the computation of thermodynamic parameters such as ln activity, solubility, and henry’s constants with the use of COSMO-RS. An understanding of absorption mechanisms was arrived at through the examination of energetic structures, enthalpic mixing analysis, and comparisons of the resulting thermodynamic absorption values. Influence of independent systematic parameters were examined through varying pressure, temperature, and compositions while comparing resulting thermodynamics. EHS analyses were performed on the viable DES candidates per system using VEGA KNN predictive software and Fischer Scientific SDS databases to understand the environmental and human worker safety/impacts of utilizing the DES components in industry. Aspen Plus V12 was utilized to compare DES system with conventional adsorbents on performance and energy requirements. Parameters for Aspen Plus V12 were found through literature, generated with COSMO-RS, and neural networks when necessary.

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