Thermophysical Properties of 1-Butyl-3-Methylimidazolium Bis(trifluoromethylsulfonyl)imide at High Temperatures and Pressures

Abstract

-Pressure-density-temperature (p,ρ,T) data of the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [BMIM][NTf 2 ] at T = (273.15 to 413.15) K and pressures up to p =140 MPa are reported with an estimated experimental relative combined standard uncertainty of Δρ/ρ = ±(0.01 to 0.08)% in density. The measurements were carried out with a newly constructed Anton-Paar DMA HPM vibration-tube densimeter. The system was calibrated using double-distilled water, aqueous NaCl solution, methanol, toluene and acetone. An empirical equation of state for fitting the (p,ρ,T) data of [BMIM][NTf 2 ] has been developed as a function of pressure and temperature. This equation is used for the calculation of the thermophysical properties of the ionic liquid, such as isothermal compressibility, isobaric thermal expansibility, thermal pressure coefficient, internal pressure, isobaric and isochoric heat capacities, speed of sound and isentropic expansibility.

Speed of Sound and Ultrasound Absorption in Ionic Liquids

“…As illustration, we presented the comparison of density calculated by an indirect acoustic method as a function of pressure to ones measured directly by high pressure densimeter, as well as, speeds of sound and isentropic compressibilities reported in literature (Figures 25 and 26). 14,17,214,218 The results underscore previous warnings as to the enormous errors incurred by using the Safarov's approximation for calculation of high-pressure speed of sound data.…”

“…where N is the number of points of the data set considered. y1 -data reported by Dzida et al 214 , y2 -data reported by b Esperança et al 17 , c Gomes de Azevedo et al 14 , d Hamidova et al 218 , e Currás et al 286 , f Wojnarowska et al 287 and g Safarov et al 207…”

“…An increase of the nonlinearity of u(T) with decreasing the temperature, together with a similar temperature effect on the viscosity (see Figure 8) Only six publications were dedicated to the experimental speed of sound under high pressures , 14,15,17,29,214 which were obtained from direct measurements, and all other high pressure data had been estimated from the equation of state. 196,199,200,207,218 The equation by Sun et al 219 was chosen by Dzida et al 29,214 to smooth out the speed of sound, pressure and temperature: (4)…”

“…25,27,114 The acoustic method, which has found wide acceptance as a precise tool for the determination of thermodynamic properties of compressed liquids is an attractive alternative to the direct determination of the pρT data of liquids. 4,8,29,40 14,15,29,17,214 Additionally, pρT data of [C4C1im][NTf2], 218 [C6C1im][NTf2], 207 The pressure dependencies of the density and heat capacity, isentropic compressibility, the isothermal compressibility, isobaric expansibility, isochoric thermal-pressure coefficient, isochoric heat capacity are calculated by acoustic method using the well-known thermodynamic relationships. 8,14,15,29 214 are in a very good agreement with data obtained by high pressure densimeter 14,17,207,218,286 , while a bad agreement with the high-pressure specific volumes obtained using dilatometer 287 17 and with excellent agreement with calculated by the acoustic method by Gomes de Azevedo et al 14 (the maximum deviation is 0.0013 GPa -1 at 10 MPa and 303.15 K).…”

Smart Fluid Systems: The Advent of Autonomous Liquid Robotics

“…Ionic Liquids (ILs) are salts which are liquid below the boiling temperature of water, are based on ionic structures, very frequently having low vapor pressures at room temperature or below, normally featuring a high viscosity and potentially could be either hydrophobic or hydrophilic . As an example, 1‐ethyl‐3‐methylimidazolium ethylsulphate (EtOSO 3 ) has a melting point of 175 K. Furthermore they are non‐flammable, and commonly thermally stable over a wide range of temperatures . This would make them a suitable candidate for future space grade lubricants that seldom operate at temperatures lower than 230 K .…”