Phase Equilibrium Relations of Semiclathrate Hydrates Based on Tetra-n-butylphosphonium Formate, Acetate, and Lactate

Abstract

Phase equilibrium (temperature−composition) relations of tetra-n-butylphosphonium formate (TBP-For), acetate (TBP-Ace), and lactate (TBP-Lac) semiclathrate hydrate systems have been measured. The highest equilibrium temperatures of TBP-For, TBP-Ace, and TBP-Lac semiclathrate hydrates were 280.9, 284.6, and 283.8 K at the atmospheric pressure, respectively, where the composition of tetran-butylphosphonium carboxylate was approximately 0.035 ± 0.001 (mole fraction) in every system. The dissociation enthalpies of tetra-nbutylphosphonium carboxylate semiclathrate hydrates were measured by differential scanning calorimetry. The dissociation enthalpies of TBP-For, TBP-Ace, and TBP-Lac semiclathrate hydrates were (187 ± 3), (193 ± 3), and (177 ± 3) J•g −1 , respectively.

Thermophysical Property Measurements of Tetrabutylphosphonium Oxalate (TBPOx) Ionic Semiclathrate Hydrate as a Media for the Thermal Energy Storage System

“…In the previous studies of ionic semiclathrate hydrates, similar tendencies of temperature increase and decrease with mass fraction in solution were reported (Yamauchi et al, 2017a,b;Arai et al, 2018Arai et al, , 2019Shimada et al, 2018Shimada et al, , 2019. From the low mass fraction to a specific mass fraction for each ionic semiclathrate hydrate, the phase equilibrium temperature tended to rise with the increase of the mass fraction.…”

“…After keeping at −20 • C for 10 min to complete the formation of the hydrate crystals, the system temperature was increased from −20 • C to 20 • C under a heating rate of 2 • C min −1 to dissociate the hydrate crystals. The reliability of the higher heating rate of 2 • C min −1 used in this process in determining the dissociation temperature was shown in previous studies (Yamauchi et al, 2017a;Arai et al, 2018;Shimada et al, 2018).…”

“…At that specific mass fraction, the highest phase equilibrium temperature was observed. The previous studies also reported that the congruent point would be at the mass fraction of the highest phase equilibrium temperature (Yamauchi et al, 2017a,b;Arai et al, 2018Arai et al, , 2019Shimada et al, 2018Shimada et al, , 2019Koyama et al, 2019).…”

“…TBP hydrates consisting of carboxylic acid anions were reported in the previous studies (Arai et al, 2018;Shimada et al, 2018Shimada et al, , 2019. Further investigation of the thermophysical properties of hydrate will lead to expand the application range of hydrates.…”

N-Ethyl-N-propylpyrrolidinium Bis(fluorosulfonyl)amide Ionic Liquid Electrolytes for Sodium Secondary Batteries: Effects of Na Ion Concentration

“…[16][17] Many ILs based on TFSA − and FSA − have been reported to date. [18][19][20][21][22][23][24] FSA − forms significantly less viscous ILs than TFSA − and other chemically inert anions. [25][26][27][28][29] A low viscosity provides the fluidity needed to operate energy storage devices at room-to-intermediate temperatures.…”