Hexane elimination from soybean oil by continuous packed tower processing with supercritical CO2

Hexane elimination is the most energy-consuming step in the industrial extraction of soybean oil. It utilizes three sets of equipment: two evaporation stages in series followed by a stripper at a pressure of about 0.07 bar. The final hexane residue in the oil is about 1000 ppm. We propose an alternative to the present process for hexane elimination, based on the extraction of the soybean oil/hexane mixture with supercritical CO₂ in a continuous countercurrent packed tower. In this work, we tested a soybean oil/hexane mixture feed containing 10% by weight of hexane. Various pressures and temperatures of the column were tested to reduce hexane residue in the oil. The extraction process was demonstrated to be very effective for hexane separation. Indeed, at the bottom of the column we recovered soybean oil containing quantities of hexane as low as 20 ppm when we operated at 120 bar, 40°C. The effect of process parameters is also discussed.