Use of liquid carbon dioxide to remove hexane from soybean oil

Liquid carbon dioxide (L-CO2) was investigated as a means to separate hexane from the mixture of soybean oil (SBO) and hexane resulting from the hexane extraction of soybeans. Using a fractionation tower, 5 vol of CO2 (i.e., 100, 200, 300, 500, and 1000 L expanded gas) were passed through 50 mL of two concentrations of n-hexane (i.e., 10 and 25% w/w) in SBO. After passing through the hexane/SBO mixture, the expanded CO, was passed through a chilled collection flask to capture extracted hexane and SBO. The raffinate SBO was removed from the column and analyzed for residual hexane using International Organization for Standardization Method 9832:2002. Residual hexane decreased as the amount of L-CO2 used increased and was less than 20 ppm after 200 L of CO2. The amount of SBO extracted increased with the volume of CO2 used. Significantly more SBO and hexane were collected from the 25% sample than the 10% sample. During the extraction of the mixture, the CO2 selectively carried over TG with lower M.W. This research demonstrates the ability to use L-CO2 to remove hexane from mixtures of hexane and SBO at both low pressures and temperatures.