(408j) Gas Capture by Ionic liquids

With the rapid development of the global industrialization process, a large number of gases, such as CO₂, SO₂, NH₃ and H₂S, have been produced. Among of them, CO₂ and SO₂ have caused air pollution problems, resulting in a serious harm to the environment and human health. On the other hand, CO₂ and SO₂ are also important source for synthesizing chemicals. Recently, ionic liquids (ILs) have been regarded as one of the most promising alternative solvents for capturing CO₂ or SO₂ due to their special physicochemical properties, such as negligible vapor pressure and designable character. For example, it was found that N-butylpyridinium thiocyanate ([C₄Py][SCN]) can absorb 0.841 gSO₂/g IL at 293 K and 0.10 MPa¹.

In this work, the mechanism of CO₂/SO₂ absorption in different kinds of ILs were systemically studied by molecular simulations. The microscopic structure, interaction energy and dynamic properties of the mixtures of ILs and CO₂/SO₂ were investigated. The results of interaction energy and fractional free volume of ILs showed that unlike non-polar gas CO₂, the interaction energy of cation-anion and free volume do not play a dominant role in SO₂ absorption. The solvation of SO₂ in ILs is controlled by enthalpy. Both the cations and anions play an important role in SO₂ solubility. Based on the above studies, a serial of ILs were synthesized for capturing CO₂/SO₂. Moreover, the energy and economic analysis of whole process of CO₂ capture with ILs were simulated. It was found that the IL process saved about 15% regeneration heat energy consumption and 11.5% total capture cost compared to the MEA process.

Acknowledgment

This work was supported by the National Natural Scientific Fund of China 51674234.

Reference

1. J. Zeng, H. S. Gao, X. C. Zhang, H. F. Dong, X. P. Zhang, S. J. Zhang, Chem. Eng. J, 2014, 251, 248-256.