Global Climate & Energy Project
CO2 CaptureNovel Ionic Liquids for Pre-Combustion CO2 Capture
Start Date: July 2012
Joan F. Brennecke1, Brandon L. Ashfeld2, Edward J. Maginn1, William F. Schneider1, 2 and Mark A. Stadtherr1, 1Department of Chemical and Biomolecular Engineering, 2Department of Chemistry and Biochemistry, University of Notre DameObjective
This research will follow a systematic approach to the design and development of novel ionic liquids for the separation of carbon dioxide (CO2) from pre-combustion gases with the overall goal of mitigating CO2 emissions from gasification-based power plants. This project seeks to increase the capacity for CO2 capture well above the level achieved thus far in conventional post-combustion IL systems.Background
In pre-combustion capture, coal, biomass or other fuel is processed in a gasifier and converted to a synthetic gas (syngas) consisting primarily of hydrogen and carbon monoxide (CO). The CO can be converted to CO2 and more hydrogen by adding water and taking advantage of the water-gas-shift reaction. Chemical impurities and CO2 are removed from hydrogen prior to its use as a clean-burning fuel. This process has the potential of capturing and removing 90 percent of CO2 emissions from power plants - major contributors to global warming.
This project explores the use of ionic liquids (ILs) in pre-combustion capture. ILs are salts with low melting points, wide liquid-phase operating ranges and endless tunability. While ILs for post-combustion CO2 capture are a popular research topic, less attention has been focused on ILs for pre-combustion systems. To our knowledge, ILs appropriate for pre-combustion CO2 separation do not currently exist.
IL-absorbent materials have many advantages over conventional pre-combustion CO2 capture technologies, including longer lifetimes and higher stability over a range of process conditions. Conventional pre-combustion capture relies on physical solvents, such as Rectisol (chilled methanol). However, ILs can operate at higher temperatures than Rectisol. Thus, a major advantage of ILs would likely be reduced energy consumption, since neither the absorption solvent nor the pre-combustion gases would have to be chilled. In addition, ILs require no added water as a diluent or carrier.
ILs can also be tuned in a variety of ways, such as altering the structure and components of positive and negative ions, or by including an additive that changes the process chemistry. This flexibility offers the potential of tuning a given absorption process to specific gas conditions and compositions at individual power plants.
Absorbent materials for pre-combustion CO2 capture must be able to (1) separate CO2 from hydrogen; (2) take advantage of the much higher total and partial pressures of CO2; and (3) operate at high temperatures.
The goal of this project is to design materials that can capture and release CO2 using temperature or pressure swings. The fundamental approach will be to develop, synthesize and test pre-combustion ILs using computational property predictions, and systems analysis and life cycle analysis modeling (see Figure 1). This model-driven development framework will lead to new materials with the desired selectivity that will enable tuning of the absorption capacity for pre-combustion CO2 separation.
This approach should yield three novel types of ILs for pre-combustion CO2 capture:
Understanding and controlling these cooperative reactions will play a key role in developing a viable pre-combustion IL technology capable of capturing 90 percent of CO2 emissions from power plants with low operating and capital costs.