Specific Heat Capacities of Two Functional Ionic Liquids and Two Functional Deep Eutectic Solvents for the Absorption of SO<sub>2</sub>

The specific heat capacities (<i>C</i><sub>p</sub>) of four absorbents (1,1,3,3-tetramethlylguanidinium lactate, monoethanolammonium lactate, betaine-ethylene glycol, and l-carnitine-ethylene glycol), which can chemically absorb sulfur dioxide (SO<sub>2</sub>) with low concentrations, were measured by a Calvet BT 2.15 calorimeter in a temperature range of 318.15 K–363.15 K. The measured specific heat capacities as a function of temperature were correlated with a second-order empirical polynomial equation. The result indicates that the equation can accurately fit the measured specific heat capacities. All the measured specific heat capacities increase with increasing temperature. 1,1,3,3-Tetramethlylguanidinium lactate has the lowest specific heat capacity. The measured specific heat capacities of the four absorbents are lower than that of water, which is beneficial to the desulfurization process.