ABSTRACT

Isobaric molar heat capacity (Cp) of eight ionic liquids (ILs) was measured from 283.15 K to 338.15 K with a micro DSC III calorimeter with a heating rate of 0.25 K*min-1 using batch cells. Cp values were determined with an expanded uncertainty about 2%. Four of the selected ILs are imidazolium based with the anions hexylsulfate, trifluoromethanesulfonate, tris(pentafluoroethyl)trifluorophosphate and bis(trifluoromethylsulfonyl)imide whereas the other three are pyrrolidinium-based ILs with trifluoromethanesulfonate, tris(pentafluoroethyl)trifluorophosphate or bis(trifluoromethylsulfonyl)imide anions. The last one is tetrabutylphosphonium tris(pentafluoroethyl)trifluorophosphate. Phase transitions in the temperature range are only observed for 1-butyl-2,3-dimethylimidazolium trifluoromethanesulfonate and tetrabutylphosphonium tris(pentafluoroethyl)trifluorophosphate; isobaric molar heat capacities are determined in solid phase for both ILs. The results showed that Cp values increase with temperature and they present the usual strong dependence with the molar mass of the IL: Cp increases with the molecular weight of the IL. Moreover, it was found that isobaric specific heat capacities, cp, for phosphate-based ILs are the lowest, followed by imide-based ones, and ILs with anions containing sulphur atoms show the highest cp values. Finally, a group contribution method was used for predicting molar heat capacity for three of the studied ILs obtaining good agreement with experimental data.

Compounds

#	Formula	Name
1	C15H17F18N2P	1-butyl-2,3-dimethyl-1H-imidazolium trifluorotris(perfluoroethyl)phosphate(V)
2	C8H11F6N3O4S2	1-ethyl-3-methylimidazolium bis((trifluoromethyl)sulfonyl)imide
3	C10H17F3N2O3S	1-butyl-2,3-dimethylimidazolium trifluoromethanesulfonate
4	C12H24N2O4S	3-ethyl-1-methyl-1H-imidazolium hexyl sulfate
5	C14H18F18NOP	1-(2-methoxyethyl)-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate
6	C10H18F6N2O5S2	1-(2-methoxyethyl)-1-methylpyrrolidinium bis((trifluoromethyl)sulfonyl)amide
7	C10H20F3NO3S	1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate
8	C22H36F18P2	tetrabutylphosphonium tris(pentafluoroethyl)trifluorophosphate
9	C4H10O	butan-1-ol

Datasets

The table above is generated from the ThermoML associated json file (link above). POMD and RXND refer to PureOrMixture and Reaction Datasets. The compound numbers are included in properties, variables, and phases, if specificied; the numbers refer to the table of compounds on the left.
Type	Compound-#	Property	Variable	Constraint	Phase	Method	#Points
POMD	1	Molar heat capacity at constant pressure, J/K/mol ; Liquid	Temperature, K; Liquid	Pressure, kPa; Liquid	Liquid	Large sample (1 g) DSC	12
POMD	2	Molar heat capacity at constant pressure, J/K/mol ; Liquid	Temperature, K; Liquid	Pressure, kPa; Liquid	Liquid	Large sample (1 g) DSC	12
POMD	3	Triple point temperature, K ; Crystal 2			Crystal 2 Crystal 1 Air at 1 atmosphere	DSC	1
POMD	3	Triple point temperature, K ; Crystal 1			Crystal 1 Liquid Air at 1 atmosphere	DSC	1
POMD	3	Triple point temperature, K ; Crystal 2			Crystal 2 Crystal 1 Air at 1 atmosphere	DSC	1
POMD	3	Triple point temperature, K ; Crystal 1			Crystal 1 Liquid Air at 1 atmosphere	DSC	1
POMD	3	Molar enthalpy of transition or fusion, kJ/mol ; Crystal 2			Crystal 2 Crystal 1 Liquid	DSC	1
POMD	3	Molar enthalpy of transition or fusion, kJ/mol ; Crystal 1			Crystal 1 Liquid Air at 1 atmosphere	DSC	1
POMD	3	Molar enthalpy of transition or fusion, kJ/mol ; Crystal 2			Crystal 2 Crystal 1 Liquid	DSC	1
POMD	3	Molar enthalpy of transition or fusion, kJ/mol ; Crystal 1			Crystal 1 Liquid Air at 1 atmosphere	DSC	1
POMD	3	Molar heat capacity at constant pressure, J/K/mol ; Liquid	Temperature, K; Liquid	Pressure, kPa; Liquid	Liquid	Large sample (1 g) DSC	4
POMD	3	Molar heat capacity at constant pressure, J/K/mol ; Crystal 2	Temperature, K; Crystal 2	Pressure, kPa; Crystal 2	Crystal 2	Large sample (1 g) DSC	3
POMD	4	Molar heat capacity at constant pressure, J/K/mol ; Liquid	Temperature, K; Liquid	Pressure, kPa; Liquid	Liquid	Large sample (1 g) DSC	12
POMD	5	Molar heat capacity at constant pressure, J/K/mol ; Liquid	Temperature, K; Liquid	Pressure, kPa; Liquid	Liquid	Large sample (1 g) DSC	12
POMD	6	Molar heat capacity at constant pressure, J/K/mol ; Liquid	Temperature, K; Liquid	Pressure, kPa; Liquid	Liquid	Large sample (1 g) DSC	12
POMD	7	Molar heat capacity at constant pressure, J/K/mol ; Liquid	Temperature, K; Liquid	Pressure, kPa; Liquid	Liquid	Large sample (1 g) DSC	12
POMD	8	Triple point temperature, K ; Crystal 2			Crystal 2 Crystal 1 Air at 1 atmosphere	DSC	1
POMD	8	Triple point temperature, K ; Crystal 2			Crystal 2 Crystal 1 Air at 1 atmosphere	DSC	1
POMD	8	Triple point temperature, K ; Crystal 1			Crystal 1 Liquid Air at 1 atmosphere	DSC	1
POMD	8	Molar enthalpy of transition or fusion, kJ/mol ; Crystal 2			Crystal 2 Crystal 1 Air at 1 atmosphere	DSC	1
POMD	8	Molar enthalpy of transition or fusion, kJ/mol ; Crystal 1			Crystal 1 Liquid Air at 1 atmosphere	DSC	1
POMD	8	Molar enthalpy of transition or fusion, kJ/mol ; Crystal 2			Crystal 2 Crystal 1 Air at 1 atmosphere	DSC	1
POMD	8	Molar heat capacity at constant pressure, J/K/mol ; Crystal 1	Temperature, K; Crystal 1	Pressure, kPa; Crystal 1	Crystal 1	Large sample (1 g) DSC	2
POMD	8	Molar heat capacity at constant pressure, J/K/mol ; Crystal 2	Temperature, K; Crystal 2	Pressure, kPa; Crystal 2	Crystal 2	Large sample (1 g) DSC	5
POMD	9	Molar heat capacity at constant pressure, J/K/mol ; Liquid	Temperature, K; Liquid	Pressure, kPa; Liquid	Liquid	Large sample (1 g) DSC	12

Thermodynamics Research Center / ThermoML | Journal of Chemical Thermodynamics

Isobaric heat capacity of nanostructured liquids with potential use as lubricants

Salgado, Josefa, Teijeira, Tamara, Parajo, Juan Jose, Fernandez, Josefa, Troncoso, Jacobo

ABSTRACT