(707d) Experimental Measurements of Amine-Functionalized Ionic Liquids and Carbon Dioxide for Gas Separation

Ionic liquids, organic salts with low melting points, have shown great potential to replace the current carbon capture technology which uses an aqueous amine solution. The major problems with aqueous amine solutions are high parasitic energy load, corrosion and degradation in the presence of oxygen. This work focuses on ionic liquids which can chemically complex to the carbon dioxide for gas separation by experimentally measuring the carbon dioxide capacity, heat of absorption, and viscosity.

The capacity of carbon dioxide in ionic liquids was measured using a stoichiometric method at room temperature and pressures between (10 ? 1000) mbar. Carbon dioxide uptake is as high as one mole of carbon dioxide per mole of ionic liquid, with tunable capacity by placement of the amine on the anion or cation and choice of substituents.

The heat of absorption of the gas in the ionic liquid was investigated by calorimetry. This gives information regarding the heat of reaction with carbon dioxide, which determines the energy requirement to remove the carbon dioxide from the ionic liquid. We see very low enthalpies for ionic liquids which physically dissolve carbon dioxide and enthalpies which are much higher for the amine-functionalized ionic liquids. However, the enthalpy can be varied significantly by careful choice of substituents.

Another important property of ionic liquid and carbon dioxide mixtures is viscosity. The addition of carbon dioxide to the ionic liquid typically results in a large increase in viscosity, which could hinder industrial applications. Additives such as water, which would be present in the ionic liquid during removal of carbon dioxide from flue gas, were examined to lower the viscosity. The addition of just 0.1 % water by weight showed a 10 % decrease in viscosity, but at a cost of slightly decreased carbon dioxide uptake.