Determination of Oxygen Solubility in Refinery Streams with a Membrane-Covered Polarographic Sensor

A membrane-covered polarographic sensor is commonly used to measure dissolved oxygen activities in test fluids. However, it is incapable of determining the oxygen concentration or solubility in fluids directly. To convert the activity to its corresponding concentration, the oxygen solubility data are needed. For complex samples such as refinery hydrocarbon streams, a complementary technique for oxygen solubility measurement is often employed to aid the polarographic determination of the dissolved oxygen concentration. In this work, an indirect polarographic method has been developed to determine the oxygen solubility in a refinery hydrocarbon, thus eliminating the need of any complementary techniques. The method involves mixing an air-saturated hydrocarbon sample with an oxygen-free reference solvent such as toluene at various blending ratios. The oxygen solubility in the sample can be obtained by regression of the measured activities versus the volume fractions of the sample. The determined oxygen solubilities for several common hydrocarbons are consistent with the literature data.