(316e) Trans-FREE Hydrogenation of Vegetable Fat in Vapor Phase Modified Supercritical CO2

Environmental and human safety concerns have become determining factors in chemical engineering and process development. Currently, there is a strong emphasis on the development of more sustainable processes. Solvents that have interesting potential as environmentally alternatives to organic solvents include water, ionic liquids, fluorous phases, and supercritical or dense phase fluids. Environmental sustainability is the process of making sure current processes of interaction with the environment, are pursued with the idea of keeping the environment as pristine as possible, by avoiding a severe level of degradation, for future generations. Carbon dioxide is often promoted as a sustainable solvent, as CO2 is non-flammable, exhibits a relatively low toxicity and is naturally abundant. However, injudicious use of carbon dioxide in a process or product can reduce rather than enhance overall sustainability.

The partial hydrogenation of fats and oils has the purpose of providing products with the desired melting profile and texture, according to their final use. The hydrogenated oil is more stable and less sensitive to oxidation. The hydrogenation of sunflower oil was carried out in fixed bed reactor in supercritical carbon dioxide – SC CO2 (80%v/v) containing added hexane (20%v/v). The specific objective for the research presented here was the determination of supercritical carbon dioxide/hexane cosolvent mixture over a range of pressure and temperature settings to obtain an estimate of the temperature-pressure parameters that would be best for obtaining low trans fatty acids in the hydrogenated products. The use of a small percentage of cosolvent, may provide additional lipid solubility at lower temperature and pressure conditions and allow use of supercritical carbon dioxide/hexane at lower pressures than pure carbon dioxide, an important consideration when designing large scale processing equipment.

The results from this study show that the solubility of vegetable oils in SC CO2 can be increased due to the addition of an appropriate cosolvent, e.g. hexane, which allows a reduction in operating pressure which assures complete miscibility in the reactive mixture for a given temperature and feed composition in comparison with the system using only SC CO2 as solvent. On the other hand, the feasibility of continuous single-phase hydrogenation increases because of the minimization the risk due to the use of modified SC CO2 under mild conditions instead of some flammable solvents such as SC propane or DME. The process safety for the entrainers was evaluated using the DOW's Fire and Explosion Index to determine the most suitable modifier for the reaction.