(506c) Use of Ionic Liquids as Physical Solvents for Selective Capture of CO2 From Fuel Gas Streams

This study is to investigate the potential use of ionic liquids (ILs) as physical solvents for selective CO2 capture from post water-gas-shift reactor streams at elevated pressures and temperatures. The equilibrium gas solubility (x*) and the volumetric mass transfer coefficients (kLa) for CO2, H2 and a gas mixture (CO2, H2, CH4, CO, Ar) in three ILs (TEGO IL K5, TEGO IL P51P and TEGO IL P9) were determined. The data were obtained in an agitated reactor, equipped with sight-windows, in wide ranges of pressure, temperature, mixing speed, and liquid height.

Under the operating conditions investigated, the CO2 solubilities in the three ionic liquids increased with pressure at constant temperature and decreased with temperature at constant pressure. Also, the volumetric liquid-side mass transfer coefficients of CO2 increased with mixing speed, pressure, and temperature and decreased with liquid height. The CO2 solubilities in the TEGO IL K5 were greater than those in the other two ILs. Under similar operating conditions, the CO2 solubilities in the three ILs were greater than those of H2, which reflects the selective nature of ILs to capture CO2. In addition, the ILs appeared to have negligible vapor pressure up to 500 K, which presents an advantage over conventional physical solvents currently employed for CO2 capture from post water-gas-shift reactor streams.

This study demonstrated the thermal stability of the ILs and highlighted their ability to selectively capture CO2 at temperatures up to 500 K and pressures as high as 30 bars.

ACKNOWLEDGMENT

The technical effort was performed in support of ongoing Carbon Dioxide research at the National Energy Technology Laboratory of the U.S. Department of Energy under RDS contract DE-AC26-04NT41817.