Epoxides from plant oils
Fraunhofer Institute for Interfacial Engineering and Biotechnology
Use and production of plant epoxides
- Vegetable oils as renewable raw materials for the production of epoxides.
Through epoxidation of unsaturated fatty acids and triglycerides products with increased polarity and reactivity are generated. These epoxides can, for example, be used as PVC stabilizers, plasticizers, cross-linkers in powder coatings, in epoxy resins, or as additives in lubricating oils. Normally, epoxides are manufactured from petrochemical base substances. Recently, plant-based epoxides have been obtained on an industrial scale, primarily from soy oil. In this context, the so-called Prilezhaef reaction is used, in which the olefinic double bonds of the unsaturated fatty acids are oxidized by peracid to expoxides (oxiranes). The peracid formation takes place via a chemical process, frequently in situ, based on reaction of hydrogen peroxide with acetic or formic acid using stronger mineral acids or ion exchange resins as the catalyst.
- Simplified reaction diagram of a chemo-enzymatic epoxidation and reaction of an immobilized lipase (Novozym® 435).
An alternative to the chemical process is chemo-enzymatic epoxidation, in which the enzyme lipase catalyzes the peracid formation from fatty acids and hydrogen peroxide. Substantial advantages of the chemo-enzymatic methods are thus the milder process conditions and a higher selectivity of the conversion. The undesired ring-opening reactions, which occur in the chemical methods, can, for example, be avoided to a very great extent in chemo-enzymatic processes.
The Fraunhofer IGB focuses on the optimization of chemo-enzymatic epoxidation of different vegetable oils and fatty acids, which are not in competition with the food industry. In this context, the oil of the annual, herbaceous Iberian dragon’s head, for example, is used. Using commercially available enzymes, e.g., an immobilized lipase from Candida antarctica (Novozym® 435, Fig. 2), we optimized the manufacturing[DFW1] process. In this context, for example, the influence of substrate concentration, hydrogen peroxide addition, the quantity of lipase used, and the temperature on the turnover of different substrates was investigated. As a result of the optimization of different process parameters, the different unsaturated fatty acids and oils could be converted into the corresponding epoxides with an efficiency of 100 % using Novozym® 435.
- Thin-layer chromatographic analysis of the lipase-catalyzed conversion of oleic acid (OA) to epoxy stearic acid (ESA).
Beyond this, we also have screened for appropriate new enzymes. In this context, we have succeeded in identifying new, not commercially-available enzymes, which also catalyze peracid formation and thus in a subsequent step the expoxidation of unsaturated fatty acids. The produced epoxides are currently being investigated with regard to their technical utilization, and the manufacturing process is also being further optimized with regard to the product properties. On the basis of these results, a process design for the manufacture of epoxides on a technical scale should be prepared and assessed with regard to its cost-effectiveness.