Pyrrolidinium-Based Ionic Liquids as Sustainable Media in Heat-Transfer Processes

摘要

Ionic liquids are viewed as green media for many engineering applications and exhibit exceptional properties, including negligible vapor pressure, null flammability, wide liquid range, and high thermal and chemical stabilities. We present new thermophysical properties of 1-alkyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imides ([C_nC₁pyr][NTf₂] with n = 3, 4) for future application them as heat-transfer media. The speed of sound was measured at pressures up to 100 MPa and at temperatures from 293 K to 318 K. The pρT, pC_pT data, and derived thermophysical properties were determined using the acoustic method. TGA of [C_nC₁pyr][NTf₂] and cytotoxicity of [C_nC₁pyr][NTf₂] and their imidazolium counterparts ([C_nC₁im][NTf₂]) are investigated. The physicochemical properties of [C_nC₁pyr][NTf₂] are compared with those of [C_nC₁im][NTf₂] and commercial heat-transfer fluids (Therminol VP-1, Therminol 66, Marlotherm SH). [C₃C₁pyr][NTf₂] and [C₄C₁pyr][NTf₂] have a wide liquid range of ～480 K and high decomposition onset temperatures of 771 and 776 K, respectively. [C_nC₁pyr][NTf₂] exhibit high energy storage density of ～1.98 MJ m–3 K–1, which is slightly dependent on temperature and pressure. The thermal conductivity of [C_nC₁pyr][NTf₂] is comparable to that of commercial heat-transfer fluids. [C_nC₁pyr][NTf₂] have lower toxicity for normal human dermal fibroblast cells than [C_nC₁im][NTf₂]. Thus, [C_nC₁pyr][NTf₂] are promising heat-transfer fluid candidates.]]>