Specific Heat Capacity of Non-Functional and Functional Ionic Liquids during the Absorption of SO2

Ionic liquids (ILs), a new type of absorbents, are widely used to absorb sulfur dioxide (SO2) in flue gas. However, the lack of data on the physical properties of ILs has severely hampered their industrial applications. Unlike previous reports on the specific heat capacity of pure ILs, this work not only focuses on measuring the specific heat capacity of pure ILs but also provides the specific heat capacity of IL and SO2 mixtures during the absorption process. First, we measured the specific heat capacities of six ILs including functional ILs, 1,1,3,3-tetramethylguanidinium lactate ([TMG][Lac]), [TMG][suberate], [TMG][dodecanedioate], and 1-butyl-3-methylimidazolium acetate ([Bmim][Ac]), and non-functional ILs, [TMG][tetrafluoroborate] and [Bmim][tetrafluoroborate], at 303.15-333.15 K. We found that the specific heat capacities of the ILs with or without absorbed SO2 increase with temperature. The specific heat capacity of ILs increases with the increase of the amount of absorbed SO2. Then, we investigated the effect of the length of anionic alkyl side chains on the specific heat capacity of SO2 absorption and found that the specific heat capacity of ILs with shorter alkyl side chains was smaller than that of ILs with longer alkyl side chains. We simulated the absorption process using Gaussian software and found that the specific heat capacities of ILs and SO2 systems were mainly caused by the vibration of molecules.

Automated summary

This study measured the specific heat capacities of six ILs and found that the specific heat capacities of ILs increase with temperature regardless of the presence of absorbed SO2. The specific heat capacity of ILs also increases with the amount of absorbed SO2. Additionally, the length of anionic alkyl side chains in ILs affects the specific heat capacity of SO2 absorption.