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Trisubstituted imidazolium-based ionic liquids as innovative heat transfer media in sustainable energy systems Ma#gorzata Musia#, Micha# Kuczak, Anna Mrozek-Wilczkiewicz, Robert Musiol, Edward Zorebski, and Marzena Dzida ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.8b01317 • Publication Date (Web): 04 May 2018 Downloaded from http://pubs.acs.org on May 5, 2018
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ACS Sustainable Chemistry & Engineering
Trisubstituted imidazolium-based ionic liquids as innovative heat transfer media in sustainable energy systems Małgorzata Musiał,1 Michał Kuczak,1 Anna Mrozek-Wilczkiewicz,2,3 Robert Musiol,1 Edward Zorębski,1 Marzena Dzida1* 1
University of Silesia in Katowice, Institute of Chemistry, Szkolna 9, 40-006 Katowice,
Poland 2
Silesian Center for Education and Interdisciplinary Research, University of Silesia in
Katowice, 75 Pułku Piechoty 1A, 41-500 Chorzów, Poland 3
University of Silesia in Katowice, Institute of Physics, Uniwersytecka 4, 40-007 Katowice,
Poland Corresponding Author E-mail:
[email protected] ABSTRACT One of the possible research directions for developing modern energy sector is searching for innovative working fluids with exceptional properties, which leads to reduce energy consumption and the costs of the operation of the system. As a continuation of our investigations of ionic liquids (ILs) for their use as heat transfer fluids (HTFs), we present new thermophysical properties of 1-ethyl-2,3-dimethyl-1H-imidazol-3-ium bis[(trifluoro methyl)sulfonyl]azanide ([C2MMIm][TFSI]) and
1-butyl-2,3-dimethyl-1H-imidazol-3-ium
bis[(trifluoromethyl)sulfonyl]azanide ([C4MMIm][TFSI]). Speeds of sound were conducted in the temperature range from 298 to 323 K and in the pressure range from 0.1 to 76 MPa. The temperature and pressure dependence of densities, isobaric heat capacities and related quantities was obtained by acoustic method. The viscosities, the TGA, and the cytotoxicities were also conducted. The thermal conductivities, energy storage densities, Prandtl numbers, 1 ACS Paragon Plus Environment
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isobaric heat capacities, viscosities, densities, isobaric thermal expansibilities, isothermal and isentropic compressibilities of [CnMMIm][TFSI] are compared with 1-alkyl-3-methyl-1Himidazol-3-ium bis[(trifluoromethyl)sulfonyl]azanides [CnMIm][TFSI], n = 2, 4) and 1-alkyl1-methylpyrrolidinium bis[(trifluoromethyl)sulfonyl]azanides ([CnMPyr][TFSI], n = 3, 4) considered as good candidates as HTFs and commercial HTFs. The wide liquidity range (~450 K), high decomposition onset temperature (~763 K), significant energy storage density (~1.95·106 J·m-3·K-1) of [C2MMIm][TFSI] and [C4MMIm][TFSI] predestine them as heat transfer media in sustainable energy systems. Keywords: trisubstituted imidazolium-based ionic liquids; heat transfer media; energy storage density; cytotoxicity; high pressure INTRODUCTION Sustainable energy sector development includes searching out advanced HTFs, alternative sources of energy as well as improvement of applied technology. HTFs are defined as gases or liquids that are able to transfer thermal energy from one system to another.1,2 Exemplary commercial HTFs base on hydrogenated terphenyl (Therminol66), mixture of approximately 90% phenylcyclohexane and 10% bicyclohexyl (TherminolVP-3), and mixture of isomeric dibenzyltoluenes (MarlothermSH).3–5 Thus, the current generation of organic HTFs is volatile within operating temperatures and also can decompose.6 Whereas, the thermophysical properties of ILs are generally superior to those of organic compounds, i.e. they are thermally and chemically stable, non-flammable. They are characterized by the broad range of liquid phase stability as well as the low vapour pressure under high temperatures that make them non-volatile and not-explosive.7 Making extended literature review for our recent paper,8 we have found that the imidazolium-based ILs with the tetrafluoroborate, hexafluorophosphate anions as well as imidazolium- and pyridinium-based ILs with the diethyl phosphate, methyl sulfate, trifluoromethanesulfonate, thiocyanate and bis[(trifluoromethyl)sulfonyl]azanide 2 ACS Paragon Plus Environment
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ACS Sustainable Chemistry & Engineering
anions have been tested as potential HTFs. Moreover, Chernikova et al.9 analysed the thermal stabilities, saturated vapour pressures, viscosities, densities, heat capacities, thermal conductivities, corrosion activities, radiation stabilities and toxicities of 25 different ILs with [CnCmIm], [CnMCmIm], [CnCmPyr], [CnCmPy] (n,m = 1–16) cations and abovementioned anions and compared them with HTFs such as DowthermA, Syltherm800, PMS100 or Shell ThermiaB. They noticed that [CnCmIm][TFSI], [CnMCmIm][TFSI] and [CnCmPyr][TFSI] series are the best promising HTF candidates among the studied ILs, mainly because they have high thermal and chemical stabilities, relative low viscosities as well as thermal conductivities comparable to HTFs. Recently, we confirmed that [CnMIm][TFSI] (n = 3, 4), [CnMPyr][TFSI] (n = 3, 4) can be considered as sustainable HTFs.8 In this work, as a continuation of our previous research, we analysed the usefulness of two trisubstituted imidazolium-based ILs, namely [C2MMIm][TFSI] and [C4MMIm][TFSI] as heat transfer media. In [CnMMIm][TFSI] characteristic H-bond contribution is switched off by methylation at the C(2)–H position in the imidazolium cation.10 As a consequence [CnMMIm][TFSI] have higher melting points and viscosities than [CnMIm][TFSI], but viscosities are still low in comparison with other ILs.11 We have chosen [CnMMIm][TFSI] with n = 2 and 4, because the shorter chain attached to the imidazolium cation resulted in lower toxicities and viscosities in comparison with their homologues with longer alkyl chain length in cation.12 The most important advantage is that the thermal stability of [CnMMIm][TFSI] is higher than [CnMIm][TFSI].13 An onset temperature of [C2MMIm][TFSI] and [C4MMIm][TFSI] equals 766
K
and
763
K,
respectively.
The
1-alkyl-2,3-dimethyl-1H-imidazol-3-ium
bis[(trifluoromethyl)sulfonyl]azanides are successfully used as extractants.14 Paul et al.15-17 studied the natural convection heat transfer of [C4MMIm][TFSI] and [C4MIm][TFSI] in a rectangular cavity with different aspect ratios. Furthermore, some trialkylimidazolium ILs have already been investigated as a components of IoNanofluids considering as heat transfer
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media.6,18,19 In this work we aimed to find out the usefulness of [C2MMIm][TFSI] as a potential HTF and to confirm that the [C4MMIm][TFSI]20 is a promising candidate as HTF. Therefore, the pρT, pCpT data, decomposition, melting, and glass transition temperatures, viscosities, thermal conductivities, energy storage densities, Prandtl numbers, isothermal and isentropic compressibilities, isobaric thermal expansibilities of [CnMMIm][TFSI] (n = 2, 4) are compared to [CnMPyr][TFSI] (n = 3, 4), [CnMIm][TFSI] (n = 2, 4) as well as commercial HTFs (TherminolVP-3, Therminol66, MarlothermSH). The ρ(p,T), Cp(p,T) and related quantities
were
obtained
by
acoustic
method.20
Additionally,
cytotoxicities
of
[CnMMIm][TFSI] are compared with those of [CnMPyr][TFSI] and [CnMIm][TFSI] (n=3, 4).8
EXPERIMENTAL SECTION Materials. The ILs were purchased from Iolitec. We investigated the same samples as in the recent study. 21 Table 1 presents parameters of the used samples.
Table 1 Parameters of the used samples names
1-ethyl-2,3-dimethyl-1H-imidazol-3-ium
water
CAS
M
puritya
numbers
g×mol-1
%
[C2MMIm][TFSI]
174899-90-2
405.33
>99
