Research Orientation

The working group deals with the use of compressed or supercritical CO₂ as a solvent substitute for various applications. The CO₂ extraction of natural products is still the main focus of the group, since the obtained extracts, but also the solid residues, are absolutely solvent-free without additional treatment and therefore have an excellent quality. In addition, fractional separation allows two completely different products to be obtained from one raw material. The solid residues still contain extremely valuable substances which can be isolated in a subsequent solid-liquid extraction and recovered as an additional product.

The current focus is on the isolation of natural substances, whereby two CO₂ fractions and a solvent product are obtained from one natural substance. This requires the construction and commissioning of a suitable solid-liquid extraction plant, which can also be optimally operated with the counter-current principle. The introduction of substances into a solid solid matrix by supercritical CO₂ (CO₂ impregnation) is becoming more and more important, as this achieves an even distribution of the substances over the entire cross-section, the products are solvent-free and the treatment times are drastically shorter than with other processes. This has already been successfully used for impregnating parts of artificial hip and knee joints, dyeing plastics and inserting metals into plastics. This process will also be used to investigate the production of long-term pharmaceuticals, consisting of a biodegradable plastic and the active ingredients contained therein, as well as doped films or other components for the sensor area. For liquid starting materials, micromixers are suitable, as they drastically reduce the extractor volume at high pressure while maintaining or improving efficiency. This has already been successfully implemented for the separation of water and ethanol and will be investigated for further systems in the future. The production of finest powders in the micro- or nanometer range using supercritical CO₂ is also a promising topic for future research.

Main areas of research:

• High pressure extraction using supercritical CO₂ for the isolation of natural substances for products of the food, cosmetics, pharmaceutical and food supplement industry.
• Fractional separation of the HP extracts, results in different products from the same raw material based on the different solubility at corresponding p and T conditions.
• HP cleaning of various materials e.g. removal of residual solvent content from pharmaceutical or cosmetic products which cannot be further reduced by conventional methods.
• Introduction and uniform distribution of substances in various carrier materials (CO₂ impregnation, dyeing, catalysts).
• Application of elements of microtechnology in high-pressure technology, e.g. micromixers for HP extractions of liquid starting materials.
• Production of powdery products in the micro- and nanometer range by various high-pressure processes such as RESS or GAS processes.
• Construction and operation of a classic solid-liquid extraction plant as an alternative or supplement to CO₂ high-pressure extraction. Development of combined processes e.g. CO₂ extraction of the non-polar components (fats, oils, waxes) and subsequent liquid extraction of the polar ingredients.
• Projects with membrane test rig (reverse osmosis, ultrafiltration).