Effect of introducing a cyclobutylmethyl group into an onium cation on the thermodynamic properties of ionic clathrate hydrates

Abstract

Ionic clathrate hydrates (ICHs) have been applied to thermal storage materials, which can be utilized as unusual thermal energy sources. In the present study, we developed a novel ICH including...

Thermodynamic Properties of Tetra-n-butylammonium and Tetra-n-butylphosphonium Hydroxycarboxylate Semiclathrate Hydrates

“…The dissociation enthalpy of water ice was in good agreement with the reference within an uncertainty of less than 2 kJ·kg –1 . We have reported the dissociation enthalpies measured with the same DSC. − ,,,,, The overall uncertainty in the dissociation enthalpy measured in this study is less than 3 kJ·kg –1 .…”

“…Typical DSC thermograms of TBA-HDC and TBP-HDC SCHs at a heating rate of 0.02 K min –1 are shown in Figure . From the vertices of the apparent dissociation enthalpy curves, as shown in Figure , we determined the stoichiometric compositions and true dissociation enthalpies (Δ d H ) of SCHs. ,,, The obtained dissociation enthalpies (Δ d H ) of TBA-HDC and TBP-HDC SCHs are summarized in Table . The dissociation enthalpy of TBA-HDC and TBP-HDC SCHs was slightly larger than that of nonhalide-based SCHs, which have equilibrium temperatures close to those of TBA-HDC and TBP-HDC SCHs. ,,,,, …”

“…To determine the stoichiometric compositions, the apparent dissociation enthalpy (per mass of aqueous solution, not per mass of SCH) at each composition was measured using a micro differential scanning calorimeter (DSC) (Setaram, μDSC VIIevo). The apparent dissociation enthalpy reaches the maximum value at stoichiometric composition ,,, because either excess amount of water or guest salt remains at a composition except for the stoichiometric composition. We prepared approximately 20 mg of TBA-HDC or TBP-HDC aqueous solutions for DSC measurements.…”

“…We have reported the dissociation enthalpies measured with the same DSC. [11][12][13]19,22,23,31,32 The overall uncertainty in the The crystal structures of TBA-HDC and TBP-HDC SCH were estimated by powder X-ray diffraction (PXRD). To compare the crystal structures of SCH, we measured the PXRD patterns of TBA-Suc and TBA-Mala SCHs as well as those of TBA-Tar, TBP-Tar, and TBP-Mala SCHs.…”

“…Thermodynamic properties of SCHs depend on the combination of cations with anions. − Generally speaking, the phosphonium cation decreases the equilibrium temperature of SCH compared to the ammonium cation with the same alkyl chains as the phosphonium one. Thermodynamic properties of SCHs are suitable for PCMs in cold chains because of not only the equilibrium temperatures within 270–300 K at atmospheric pressure but also the relatively large dissociation enthalpies (160–220 kJ·kg –1 ). ,− According to the working temperatures of PCMs needed in cold chains, developing SCHs with various equilibrium temperatures is required. For example, SCHs with the equilibrium temperatures of 280–283 K are suitable for the storage of vegetables and fruits, 275–281 K for vaccines, , 278–288 K for air conditioning, and 288–308 K for cooling of the lithium-ion battery .…”