# Hydrates for Cold Storage: Formation Characteristics, Stability, and Promoters
## 2 Materials and Methods
### Methods and Procedures  
For production of R141b hydrate, the system to which pure water and ice cube were added were investigated. The R141b mixed solution with a concentration of 27.65 wt% was prepared according to the saturated hydration number (water: R141b = 17:1), that is, a guest solution equal to the saturated hydration number, ignoring the volume change after the solution was mixed. Subsequently, 60 mL of the mixed solution was added to each reaction vessel. The TME hydrate was produced used a similar system. However, an excessive amount of solute was consumed when preparing the solution according to the saturated hydration number; in the experiment water was excessive and the final concentration of TME aqueous solution was 36.36 wt%. Subsequently, 32 mL of the solution was added to each reaction vessel. The cycle stability of TBAB/TBAC was evaluated using pure water and promoting methods (ice cube, stirring, and stirring + graphene). The TBAB and TBAC-mixed aqueous solutions were prepared at an equimolar ratio by mixing pure TBAB and TBAC aqueous solutions (40.00 and 36.50 wt%, 20 and 20 mL, respectively) and there was minor excess of TBAB/TBAC solute, ignoring the volume change after the solute was dissolved in water and the volume change after the solutions were mixed. After the two solutions were mixed, 40 mL of the solution was added to each reaction vessel. The specific experimental working conditions are shown in Table 2. After the solution was prepared, the reaction vessel was placed in a 5 \({}^{\circ}\)C water-bath. For the stirred system, a magnetic stirrer was used at 500 rpm. In all the experiments, the formation of the hydrates was observed under 0.1 MPa. When the state of hydrate formation no longer changed, the reaction vessel was removed, the sample was dissociated at ambient temperature (about 25 \({}^{\circ}\)C), and the induction and dissociation times were recorded. At the end of the hydrate cycle formation stability experiment, the hydrate crystals of the systems with added ice cubes were transferred to the heating and freezing microscope stage. The temperature was increased to 25 \({}^{\circ}\)C at 20 \({}^{\circ}\)C/min until the hydrates were completely dissociated, after which the temperature was lowered to 5 \({}^{\circ}\)C at 20 \({}^{\circ}\)C/min \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Gueset Molecule** & **State** & **Water** & **Molar Mass** & **Hydration** & **Dissociation** & **Dissociation Heat** & **Dissociation Pressure** \\
**Molecule** & **Miscibility** & **(g/mol)** & **Number** & **Temperature** & **(k/kg)** & **(MPa)** \\ \hline R141b & Liquid & No & 116.94 & 17 \({}^{\text{a}}\) & 6.5 \({}^{\text{b}}\) & 330 \({}^{\text{b}}\) & 0.1 \\ TME & Powder & Yes & 120.15 & 3 \({}^{\text{c}}\) & 10.4–29.7 \({}^{\text{d}}\) & 113.6 \(\pm\) 5.9–282.5 \(\pm\) 4.7 \({}^{\text{d}}\) & 0.1 \\ TBAB & Powder & Yes & 322.37 & 26 or 38 \({}^{\text{e}}\) & 12.3 \({}^{\text{f}}\) & 184.8 \(\pm\) 1.9 \({}^{\text{f}}\) & 0.1 \\ TBAC & Powder & Yes & 277.92 & 32.7 or 30.4 \({}^{\text{g}}\) & 15.0 \({}^{\text{f}}\) & 186.7 \(\pm\) 1.9 \({}^{\text{f}}\) & 0.1 \\ TBAB/TBAC & Powder & Yes & — & — & 12.3–15.3 \({}^{\text{f}}\) & 184.8 \(\pm\) 1.9–205.0 \(\pm\) 4.0 & 0.1 \\ \hline \hline \end{tabular}  
* \({}^{\text{a}}\) The data reported by [PERSON] et al. [25]. \({}^{\text{b}}\) The data reported by [PERSON] et al. [26]. \({}^{\text{c}}\) The data reported by [PERSON] et al. [27]. \({}^{\text{d}}\) The data reported by [PERSON] et al. [28] at TME aqueous solution concentrations of 20–62.5 wt %. \({}^{\text{c}}\) The data reported by [PERSON] et al. [29] at TBAB aqueous solution concentrations of 40 and 32 wt %. \({}^{\text{f}}\) The data reported by [PERSON] et al. [24] in TBAB, TBAC, and (TBAB + TBAC) mixed hydrate systems at \(x\) = 0.036 and 0.1 MPa (x was the total mole fraction of guest molecules in all aqueous solution). \({}^{\text{g}}\) The data reported by [PERSON] et al. [30] at TBAC aqueous solution concentrations of 20 and 25 wt %.  
\end{table}