A solution thermodynamic study of soybean oil/solvent systems by inverse gas chromatography

Inverse gas chromatography (IGC) has seen wide application in the characterization of molten polymers, fibrous materials, and natural products, such as proteins and carbohydrates, over the past fifteen years. This study describes a relatively simple IGC technique for evaluating solute-solvent interactions using a refined soybean oil as a solvent. Utilizing soybean columns that are 5–20% by weight of the inert support has allowed the determination of a number of thermodynamic solution parameters for 22 solute-solvent pairs in the temperature range of 55–125°C. Weight and mole fraction activity coefficients, along with Henry's Law constants at infinite dilution, are presented for six solute classes. In general, activity coefficients increase with carbon number for n-alkanes, alkyl-substituted benzenes, and n-alkanoic acids at all temperatures investigated, while the reverse is found for the n-alkanols. The activity coefficient data indicate that aromatic solutes, chlorinated hydrocarbons, ketones, and cyclohexane can readily dissolve soybean oil. Calculated heats of mixing for n-alkanols were found to be positive (to 2.84 kcal/mole) while recorded enthalpic interactions were weak for aromatic solutes, lower alkanes, and chlorinated hydrocarbons. The relevance of the above data to such problems as oil dissolution and solvent devolatilization are discussed. Presented at the American Oil Chemists' Society Annual Meeting in Phoenix, Arizona, in May 1988.