Indian American develops efficient carbon capture method

Amitesh Maiti, a researcher at the Lawrence Livermore National Laboratory (LLNL), has devised a computational screening method using ionic liquid solvent to enhance the process of carbon dioxide (CO2) separation, a step known as ‘carbon capture’.

Ionic liquids, a type of salt that melts at 100 degrees Celsius, have advantages over traditional solvents for the separation of CO2 from its polluting source such as flue gas because they are highly stable, non-corrosive and do not evaporate even at high temperature.

Current carbon capture technology is based on a general purpose solvent monoethanolamine (MEA), which chemically absorbs CO2. However, it is a non-selective corrosive which requires large-scale equipment and it works only under low to moderate partial pressure of CO2.

“With ionic liquids serving as the solvent, the process could be a lot cleaner and more accessible than that used today,” says Amitesh.

There is also a huge choice of ions, which could potentially be optimised for CO2 capture.

“By creating a computational tool that can decipher ahead of time which ionic liquids work best to separate CO2, it can be a much more efficient process when field tests are conducted,” he added.

“It’s a great advantage to have a method that can quickly and accurately compute CO2 solubility in any solvent, especially under the range of pressures and temperatures as would be found in a coal-fired power plant,” Amitesh said.

Advantages include high chemical stability, low corrosion, almost zero vapor pressure, supportable on membranes and a huge library of ion choices which can be potentially optimised for CO2 solubility.

Originally from Kolkata, Amitesh has earned his Ph.D in Condensed Matter Physics, University of California, Berkeley, 1992, MS, Physics, University of North Carolina, Chapel Hill, 1988 and B.Sc, Physics (honors), University of Calcutta, India, 1986.

Amitesh’ s work involved devising a computational strategy that can reliably screen any solvent, including an ionic liquid, for high CO2 capture efficiency.

Over the last few years several ionic liquids have been tested to be efficient solvents, providing data that could be useful in optimising the choice of ionic liquids for CO2 capture. “But each new experiment costs time and money and is often hindered because a specific ionic liquid may not be readily available,” he said.

Amitesh developed a quantum-chemistry-based thermodynamic approach to compute the chemical potential of a solute (CO2 in this case) in any solvent at an arbitrary dilution.

He found that this result coupled with an experimentally fitted equation-of-state data for CO2 can yield accurate solubility values in a large number of solvents, including ionic liquids.

He confirmed this by directly comparing the computed solubility with experimental values that have been gradually accumulating over the last few years.

He used this method to predict new solvent classes that would possess CO2 solubility nearly two times as high as the most efficient solvents experimentally demonstrated.

“With the vast choices of ions, we have barely scratched the surface of possibilities,” Amitesh said.

He hopes that the accuracy of the computational method will allow scientists to see useful trends, which could potentially lead to the discovery of practical solvents with significantly higher CO2 capture efficiency.

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