Carbon dioxide solubility in reference and vegetable lubricants developed for two stroke engines

The solubilities of carbon dioxide, CO2, in a reference semi-synthetic oil and in a developed vegetable-sunflower-based oil for two stroke engines have been measured from 283 K to 348 K and pressures up to 9 MPa in a high pressure gas solubility apparatus that works in isochoric conditions. The densities of the developed vegetable oil from 293 K to 353 K and pressures up to 60 MPa were also measured by using a vibrating tube technique. It was found that the solubility of CO2 in the vegetable oil is higher than in the reference semi-synthetic oil. The solubility of CO2 in both lubricants decreases when the temperature increases. In addition, we have found that the solubilities of O2 in these lubricants are between 7 and 10 times lower than those of CO2. Furthermore, PC-SAFT EoS was employed to model the solubility behavior of CO2 in both lubricants and the goodness of Carvalho and Coutinho model for prediction of CO2 solubility in low volatile solvents was checked for these lubricants.

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► CO2 solubilities in the developed oil are higher than in semi-synthetic reference oil.
► Compressibility of the semi-synthetic oil is higher than that of the vegetable oil.
► O2 solubilities in both lubricants are between 7 and 10 times lower than those of CO2.
► CO2 solubility in the vegetable oil is well predicted by Carvalho–Coutinho method.