Solvation Thermodynamic Properties of Hydrogen Sulfide in [C4mim][PF6], [C4mim][BF4], and [C4mim][Cl] Ionic Liquids, Determined by Molecular Simu

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• 作者：Joel S谩nchez-Badillo ; Marco Gallo ; Sandra Alvarado ; Daniel Glossman-Mitnik
• 刊名：Journal of Physical Chemistry B
• 出版年：2015
• 出版时间：August 20, 2015
• 年：2015
• 卷：119
• 期：33
• 页码：10727-10737
• 全文大小：622K
• ISSN：1520-5207

文摘

Removal of hydrogen sulfide (H₂S) and acid gases from natural gas is accomplished by absorption processes using a solvent. The gas solubility in a liquid can be used to measure the degree of removal of the gas and is quantified by the Henry鈥檚 constant, the free energy of solvation at infinite dilution, or the excess chemical potential. In this work, Henry鈥檚 constants and thermodynamic properties of solvation of H₂S were calculated in three ionic liquids: [C₄mim][PF₆], [C₄mim][BF₄], and [C₄mim][Cl] ([C₄mim], 1-butyl-3-methyl imidazolium). The first step in this work was the evaluation of the force fields for the gas and condensed phases in order to obtain accurate values for the excess chemical potential for H₂S on each ionic liquid using free energy perturbation techniques. In the H₂S鈥揫C₄mim][PF₆] and H₂S鈥揫C₄mim][BF₄] systems, the results obtained by molecular simulation agree with the experimental values reported in the literature. However, the solvation free energy calculated for the H₂S鈥揫C₄mim][Cl] system can be considered predictive because of the lack of experimental data at the simulated conditions. Based on these results, the best solvent for removing H₂S is [C₄mim][Cl] because it has the highest affinity for this species (lowest value of the Henry鈥檚 constant). Also, solvation thermodynamic properties such as enthalpy and entropy were calculated in order to evaluate their contribution to the free energy of solvation.