## 3 Results and Discussion
### Effects of Varying System Pressure  
Table 4 shows the results of the pressure analysis. Vapor liquid systems are typically operated at pressures higher than atmospheric to maximize gaseous solubility. As pressure increases, non-ideal interactions tend to have less of an overall effect on the studied systems as has been seen in other vapor liquid studies [12]. The significance of this pressure analysis is to determine how well the difluoromethane and DES system will respond to increases in pressure, and if the studied solvent combinations will behave differently. The solubility of difluoromethane was computed for each solvent combination at four different pressures; 1, 3, 6, and 9 bar. The baseline solubility is promising as the lowest is 18% mol solvent per mol difluoromethane at 25 \({}^{\circ}\)C and 1 bar for MTOA: Eucalypttol at a 1:1 molar ratio. With increase in pressure, solubility increases with values reaching up to 86% mol/mol solubility at 9 bar. The solubilities are consistent among the solvents with minor deviations due to the similarity of the surface charges. The trends are relatively linear between solubility and pressure. The solvents containing MTOA are shown to increase at a higher rate starting with the lowest solubilities and ending with the highest or equal. The lowest solubility for MTOA is with eucalypttol at 1 bar with 18.03 mol/mol. The highest for MTOA and the highest of the solvents is 86.2 mol/mol which is achieved at 9 bar for the three HBD combinations of PEG, camphor, and eucalypttol. This result is likely described through hole theory, as MTOA is geometrically dissimilar from the others by being asymmetrical. This generally offers lower viscosities and pressure-assisted pore filling [30; 38]. The HBA combinations for N4 Br, N8 Br, and BTACI all have similar solubilities, exhibiting deviations of no more than 10%. A 10% deviation is only witnessed at 1 bar, with decreasing discrepancy with an increase in pressure. The surface charge distribution is highest in the van der Waals and lowest in the hydrogen bond accepting region of the four studied HBA; this is likely the cause of this slight anomaly, as at higher pressures the polar interactions increase in significance, and the higher amount of van der Waals surfaces becomes a less dominating factor. \begin{table}
\begin{tabular}{l c c c c c c} \hline
**HBD** & **Ratio** & **Pure** & **N4 Br** & **N8 Br** & **BTACI** & **MTOA** \\ \hline - & - & - & \(-1.61\) & \(-1.43\) & \(-1.61\) & \(-1.16\) \\ PEG & 1:1 & \(-0.71\) & \(-1.39\) & \(-1.39\) & \(-1.27\) & \(-1.03\) \\ PEG & 1:2 & - & \(-1.27\) & \(-1.27\) & \(-1.2\) & \(-0.97\) \\ PEG & 1:3 & - & \(-1.19\) & \(-1.19\) & \(-1.14\) & \(-0.93\) \\ PEG & 2:1 & - & \(-1.48\) & \(-1.33\) & \(-1.48\) & \(-1.08\) \\ PEG & 3:1 & - & \(-1.52\) & \(-1.36\) & \(-1.52\) & \(-1.10\) \\ Camphor & 1:1 & \(-0.44\) & \(-1.34\) & \(-1.34\) & \(-1.19\) & \(-0.99\) \\ Camphor & 1:2 & - & \(-1.18\) & \(-1.18\) & \(-1.08\) & \(-0.89\) \\ Camphor & 1:3 & - & \(-1.07\) & \(-1.07\) & \(-1.00\) & \(-0.83\) \\ Camphor & 2:1 & - & \(-1.45\) & \(-1.28\) & \(-1.45\) & \(-1.06\) \\ Camphor & 3:1 & - & \(-1.50\) & \(-1.31\) & \(-1.50\) & \(-1.09\) \\ Eucalypttol & 1:1 & \(-0.03\) & \(-1.27\) & \(-1.27\) & \(-1.11\) & \(-0.92\) \\ Eucalypttol & 1:2 & - & \(-1.07\) & \(-1.07\) & \(-0.95\) & \(-0.78\) \\ Eucalypttol & 1:3 & - & \(-0.93\) & \(-0.93\) & \(-0.85\) & \(-0.68\) \\ Eucalypttol & 2:1 & - & \(-1.41\) & \(-1.22\) & \(-1.41\) & \(-1.02\) \\ Eucalypttol & 3:1 & - & \(-1.47\) & \(-1.27\) & \(-1.47\) & \(-1.06\) \\ Lidocaine & 1:1 & \(-0.58\) & \(-1.27\) & \(-1.27\) & \(-1.16\) & \(-0.98\) \\ Lidocaine & 1:2 & - & \(-1.10\) & \(-1.10\) & \(-1.04\) & \(-0.89\) \\ Lidocaine & 1:3 & - & \(-1.00\) & \(-1.00\) & \(-0.96\) & \(-0.83\) \\ Lidocaine & 2:1 & - & \(-1.41\) & \(-1.25\) & \(-1.41\) & \(-1.05\) \\ Lidocaine & 3:1 & - & \(-1.46\) & \(-1.29\) & \(-1.46\) & \(-1.08\) \\ \hline \end{tabular}
\end{table}