(433f) Effects of Contaminants to Physical Solvents for Pre-Combustion CO2 Capture

The pre-combustion capture process involves converting fossil fuel into syngas, primarily a mixture of carbon monoxide and hydrogen, usually by gasification. During pre-combustion, coal is first transformed into hydrogen and CO₂. In a CO₂ separation unit, the carbon dioxide is separated from the hydrogen using a solvent, such as ionic liquids (ILs). This process has the potential of capturing and removing 90 percent of CO₂ emissions from power plants - major contributors to global warming.

ILs are salts with many advantages over conventional pre-combustion CO₂ capture materials, including low melting points, longer lifetimes and higher stability over a range of process conditions. While ILs for CO₂ capture are a popular research topic, less attention has been focused on the impact of contaminants, i.e., water and  coal derived contaminants (primarily H₂S), on ILs for pre-combustion carbon capture process. We explore the use of physical solvents for pre-combustion carbon capture.   Four solvents have been under investigation, including PDMS, hybrid-PDMS, and two types of ILs, i.e., P888 allyl Tf₂N and allyl pyridinum Tf₂N, with different initial viscosity. A 1-liter Continuous Stirred Tank Reactor (CSTR) equipped with a 2-liter gas buffer tank has been used to measure CO₂ isotherms and CO₂ breakthrough curves at different temperatures. For CO₂ solubility and kinetics measurement without contaminants, a dynamic pressure-step method was applied, while a continuous flow operation was used for CO₂ breakthrough measurement in the presence of H₂O and H₂S.  Effects of H₂O and H₂S on these solvents physiochemical properties will be discussed. This study has established an understanding of the influence of precombustion contaminants, i.e., H₂O and H₂S, on solvents physiochemical properties, including CO₂ solubility, CO₂ absorption kinetics, viscosity, and so on.