The densities of four ionic liquids: 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide ([E³Mim][Nf₂]), n-propyl-n-methylpyrrolidinium bis(fluorosulfonyl)imide ([PMpyr][Nf₂]), 1-butyl-1-methylpyrrolidinium bis(fluorosulfonyl)imide ([BMpyr][Nf₂]), and 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonil)imide ([BMpyr][NTf₂]) were measured at temperatures (293.15 to 413.15) K and pressures (0.1 to 60) MPa. The experimental density data were modeled using the modified Tammann–Tait equation and the average absolute percentage deviations between measured and calculated values for all studied ionic liquids were less than 0.004%. The optimized parameters were used to calculate the isothermal compressibility, the isobaric thermal expansivity, the internal pressure, and the difference between specific heat capacities at constant pressure and at constant volume. The cation and anion influences on the properties of the ionic liquids were examined. The longer alkyl chains on cations are related to lower density of ionic liquids and ionic liquids with imidazole based cation are denser than those with pyrrolidinium cation. The presence of more stabile [NTf₂]⁻ anion in ionic liquids leads to greater densities comparing to [Nf₂]⁻ anion.

中文翻译：

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[Nf ₂ ]和[NTf ₂ ]阴离子在高压下的离子液体的密度和导出的体积特性

四种离子液体的密度：1-乙基-3-甲基咪唑双（氟磺酰基）酰亚胺（[E ³ Mim] [Nf ₂ ]），正丙基-正甲基吡咯烷鎓双（氟磺酰基）酰亚胺（[PMpyr] [Nf ₂ ]），1-丁基-1-甲基吡咯烷鎓双（氟磺酰基）酰亚胺（[BMpyr] [Nf ₂ ]）和1-丁基-1-甲基吡咯烷鎓双（三氟甲基磺酰基）酰亚胺（[BMpyr] [NTf ₂]）在温度（293.15至413.15）K和压力（0.1至60）MPa下测量。使用改良的Tammann-Tait方程对实验密度数据进行建模，所有研究的离子液体的测量值与计算值之间的平均绝对百分比偏差均小于0.004％。优化的参数用于计算等温压缩率，等压热膨胀率，内部压力以及在恒定压力和恒定体积下的比热容之间的差。研究了阳离子和阴离子对离子液体性能的影响。阳离子上较长的烷基链与离子液体的密度较低有关，具有咪唑基阳离子的离子液体比具有吡咯烷鎓阳离子的离子液体致密。存在更稳定[NTf与[Nf ₂ ] ^-阴离子相比，离子液体中的₂ ] ^-阴离子导致更大的密度。