Termodynamické vlastnosti skupiny izomerických iontových kapalin

0545067 - ÚCHP 2022 eng A - Abstrakt
Rotrekl, Jan - Bendová, Magdalena - Wagner, Zdeněk - Storch, Jan - Velíšek, Petr
Termodynamické vlastnosti skupiny izomerických iontových kapalin.
[Thermodynamic properties of a group of isomeric ionic liquids.]
Albuquerque, 2021.
[International Symposium on Solubility Phenomena and Related Equilibrium Processes /19./. 11.07.2021-16.07.2021, Albuquerque, New Mexico]
Institucionální podpora: RVO:67985858
Klíčová slova: ionic liquids * density * isobaric heat capacity * velocity of sound
Obor OECD: Chemical process engineering

For this study we have synthesized two sets of ionic liquids (ILs) with imidazolium cation and bis(trifluoro-methylsulfonyl)imide anion. In the first set the common substituent at the N1-position of the cation was butyl, whereas in the other set it was an oligoether 2-(2-ethoxyethoxy)ethyl. At the N3-position the cation was substituted with different C5-alkyls, namely pentyl, isopentyl, 3-pentyl, cyclopentyl (in both sets) and neopentyl substituent in the oligoether-substituted set. In total 11 different ionic liquids were studied. Prior to any measurement the ILs were analyzed as to the water content using the Karl Fischer titration. In order to characterize these new species, density together with the velocity of sound was measured as a function of temperature by means of Anton Paar DSA 5000 vibrating tube densitometer. Further, the isobaric heat capacity was measured by means of differential scanning calorimeter μDSC III evo by Setaram.
Density, velocity of sound and isobaric heat capacity of 11 pure ILs were measured in temperature range from 20 to 70°C. Because two sets of ILs were prepared with different C5-substituent we can compare the effect of isomerism in one set, as well as compare the two sets between each other. For all the ILs in one set values of studied properties are very close for IL substituted with linear or branched alkyl substituent. Significant difference occurred with the introduction of cyclopentyl into the structure. Regarding the density, the cyclopentyl substitution led to an increase by about 5% and 4%, in the butyl-substituted and oligoether-substituted set, respectively. In the case of the velocity of sound a similar increase was observed. The cyclopentyl substitution led to a decrease of isobaric heat capacity in both set of ILs. These results are in agreement with the expected relation between the heat capacity and molar volume. Comparing the two sets of ILs, replacing the butyl-substituent with the oligoether one resulted in significant increase of the isobaric heat capacity, while the densities showed only a very small decrease. This change of the chemical structure led also to significant increase in the velocity of sound. This can be explained by strengthening of the ion-ion interactions in the oligoether-substituted ILs, in comparison with the butyl-substituted ones.

Trvalý link: http://hdl.handle.net/11104/0322018