Please join the department as Javad Noroozi defends their PhD thesis on design of improved carbon capture solvents using molecular simulation
Abstract
Study of the equilibrium compositions of complex chemically reacting systems by means of experimental measurements and thermodynamic modeling tools is of great interest and importance in chemistry, biology, and chemical engineering. Systems involving ionic species (especially aqueous electrolyte systems) are of particular significance and have long been studied using these approaches, but their modeling by means of molecular-based methodology is in its relative infancy.
Carbon capture and storage (CCS) technology using reactive absorption is currently considered to be one of the most mature technologies to reduce greenhouse gas emissions by CO 2 capture from point sources, and the discovery of more economically effective solvents technologies is crucial to encourage its future deployment. In this thesis, I develop a general predictive and computationally efficient molecular-based simulation framework for calculating the thermodynamic properties of the electrolyte solutions involved. The framework is based on an exact translation of molecular simulation methodology to the standardstate quantities of a conventional electrolyte solution thermodynamic model. The reaction equilibrium constants are calculated by a combination of ab initio electronic structure calculations and classical force-field-based solvation free energy simulations. The resulting nonlinear equations of the thermodynamic model are then solved to predict the speciation and related solution properties, including the CO 2 partial pressure in equilibrium with the solution.
I provide evidence that the precision of the results arising from the predictive framework is comparable to or better than that of existing experimental methodologies. The methodology also permits the calculation of species with very small solution concentrations, far exceeding the capability of existing experimental methodologies. The framework thus provides a screening methodology for discovering new CO 2 solvents that is more costeffective than experimental approaches.
I demonstrate the application of this framework to the reactive absorption of CO 2 in aqueous monoethanolamine (MEA) solvent as a benchmark case, the first time that a quantitatively accurate predictive approach requiring no experimental data has been successfully applied to calculate all solution species concentrations for this system, including the partial pressure of CO 2 above the solution. The methodology is also applied to predict protonation and carbamate formation equilibrium constants and the related standard reaction enthalpies for a large set of alkanolamines in aqueous solution; the latter quantities for many of the species considered have never been measured experimentally. Potential byproducts of the methodology are its ability to predict the standard state chemical potentials and enthalpies of individual species in aqueous solution, and the intrinsic hydration free energy of the proton as a function of temperature.
Supervisor: Professor Nasser Abukhdeir