Molecular and Process Modeling of Selected Novel Solvents for CO2 Capture

Abstract

Scientists believe that reducing current greenhouse gas emissions is essential to slow global warming. CO2 capture via absorption using aqueous amine solvents remains the most widely used industrial process for mitigating the effects of climate change. The high energy demand to regenerate conventional solvents, such as the benchmark 30 wt.% Monoethanolamine (MEA), and solvent degradation are the primary technical barriers to implementing this technology. In the search for novel amines, it is imperative to know their thermodynamic properties that affect the economic design of the CO2 capture plant. One of the challenges when evaluating the performance of novel amines is the limited experimental data for new amines at relevant process conditions. This, combined with a lack of a rapid and practical framework to determine the most suitable solvent, guides this thesis's work. Given the recent advancement in molecular modeling tools, molecular-based equations of state provide a suitable platform for designing such screening frameworks. The main objective of this thesis is to apply a robust solvent screening tool using the soft-SAFT molecular-based EoS to assess novel solvents for CO2 capture. The 36 alternative novel amines investigated in this thesis belong to six families including: (1) aminoalcohols, (2) alkylethanolamines, (3) dialkylaminoalcohols, (4) cyclic amines, (5) diamines, and (6) multiamines. The soft-SAFT molecular models of these amines were developed to calculate the thermophysical properties and CO2 absorption capacities at process conditions. This thesis also highlights the predictive power of soft-SAFT in cases where no experimental data was available. The modeling was extended to calculate the two key performance indicators of cyclic capacity and regeneration energy as screening criteria to find the optimum solvent. In our search for the most efficient replacement amine, both DEEA and DETA show good potential in terms of a high cyclic capacity (Δα) and low regeneration energy (Qregen). Results presented here bolster the significance of using molecular equation of state as a practical tool in the search for novel amines for CO2 capture.

Date of Award	Dec 2022
Original language	American English
Supervisor	Maria Lourdes Vega Fernandez (Supervisor)