(297a) Reactive Separation of CO2 with Liquid Absorbents: Novel Approaches

Growth of the global economy, industry and population lead to increasing demand for energy.  Until emission-free renewable energy resources account for a significant portion of the market, traditional fossil fuels (e.g., oil, gas and coal) will remain the main sources of energy on the planet; likely for the next several decades.  Before transport to the consumer or direct utilization in power generation or by the chemical industry, fossil fuels, especially natural gas, requires removal of undesirable acid gases including CO₂.  Additionally, CO₂ is an unavoidable product of fossil fuel combustion.  To meet the specifications and potential upcoming regulations on emissions of CO₂ into the atmosphere, development and worldwide utilization of efficient CO₂ capture and sequestration technologies are required.  Certain microporous molecular sieves are proven to selectively remove CO₂, but reactive separation of acid gases can offer the lowest losses and highest product purity.

This presentation will specifically discuss the CO₂ reaction mechanisms with various amine blends in aqueous, non-aqueous and ionic liquids solutions targeting highly selective and more economically efficient CO₂ scrubbing from, e.g., flue gas.  We developed the experimental capabilities to revisit the classic acid-base (CO₂-amine) chemistry and gain a more in-depth fundamental understanding of CO₂ reaction mechanisms with various reactive solutions.  In-situ ¹³C and ¹H Nuclear Magnetic Resonance (NMR) spectroscopy using a built-in micro reactor was used to provide real time insights on reaction mechanisms and product speciation under conditions for CO₂ absorption and regeneration. 

A new approach to non-aqueous CO₂-amine carbon capture is based on the utilization of a combination of a nucleophilic amine CO₂ sorbent (Lewis base) with a second, non-nucleophilic Brønsted base; a “Mixed Base” system.  The effects of amine type, amine basicity, and the use of non-aqueous solvents on the reaction pathway and product stability will be discussed.  It will become apparent that both Lewis and Brønsted basicity are key components in the chemistry.  Proper choice of these bases and non-aqueous solvent allows capture of CO₂ molecules to tailor reaction conditions (T, P) to specific applications.   The implications of these findings for further amine studies will be outlined.