Solubility of Carbon Dioxide in Pentaerythritol Esters

The solubility of CO2 in 5 pentaerythritol tetraalkyl esters was measured at 283.15 K. The esters were pentaerythritol tetrabutyrate (PEC4), pentaerythritol tetravalerate (PEC5), pentaerythritol tetrahexanoate (PEC6), pentaerythritol tetraheptanoate (PEC7), pentaerythritol tetraoctanoate (PEC8). CO2 solubility in a commercial polyolester oil (Castrol Icematic SW32) was also measured. A static synthetic method was used, performing the experiments in a stainless steel cell with observation windows that was immersed in a thermostatic bath. Solubility was measured by charging known amounts of oil and CO2 in the cell and subtracting the amount of CO2 in the vapor phase, assuming that this consisted of CO2 alone. The estimated uncertainties were ±0.03 K for temperature, ±2 kPa for pressure, and a maximum of ±0.015 for the liquid phase mass fraction. Seventy points were measured, showing a clearly non-ideal behavior of the mixtures and a miscibility gap with PEC8 at mole fractions higher than 0.94.