Thermodynamic Properties of Ionic Semiclathrate Hydrate Formed with Tetrabutylammonium Propionate

Abstract

The phase equilibrium temperature and dissociation heat of tetrabutylammonium propionate (TBAPr) hydrate are reported. TBAPr hydrate is a type of ionic semiclathrate hydrates and also could potentially be used as thermal energy storage material. The temperature‐composition phase diagram of the TBAPr hydrate was determined in a defined range of mass fractions. Considering the dissociation heat of differential scanning calorimetry (DSC) measurements, multiple peaks of heat flow were observed in the TBAPr‐water system at the TBAPr mass fraction lower than 0.35, and there was a single peak at the mass fraction higher than 0.37.

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, 2018 , 2019 ; Shimada et al, 2018 , 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.…”

“…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, 2018 , 2019 ; Shimada et al, 2018 , 2019 ; Koyama et al, 2019 ).…”

“…Three different samples prepared from three different TBPOx aqueous solutions were measured for a given mass fraction. The visual observations with the similar apparatus and method were performed in the previous studies (Yamauchi et al, 2017a , b ; Arai et al, 2018 , 2019 ; Shimada et al, 2018 ; Koyama et al, 2019 ). These studies supported the reliability of the equilibrium temperature obtained in this study.…”

“…Clathrate hydrates are crystalline compounds consisting of the space-filling cages of water molecules and other molecules called guest compounds enclosed within the cages. They show various physical properties depending on the type of guest compounds contained (Nakayama and Hashimoto, 1980 ; Nakayama et al, 1983 ; Mayoufi et al, 2011 ; Sakamoto et al, 2011 ; Sato et al, 2013 ; Yamauchi et al, 2017a , b ; Arai et al, 2018 ; Shimada et al, 2018 , 2019 ). Ionic semiclathrate hydrates have unique structures.…”

“…The semiclathrate hydrates composed with anions with carboxylic acid anions in the guest compounds have been previously investigated (Nakayama and Torigata, 1984 ; Yamauchi et al, 2017a , b ; Arai et al, 2018 ; Shimada et al, 2018 , 2019 ). Carboxylic acid anion containing compounds are more environmentally benign, unlike those which incorporate halide anions.…”