Sustainable Processes Using Sub- and Super Critical Fluids

Abstract

“Process intensification” as a part of necessary sustainable development and “green” revolution uses also high pressure as a processing tool. The main impetus for this is on one way driven by environmental concerns to reduce the usage of conventional solvents and energy. On the other hand high pressure is a tool to design and produce the products with completely new and specified properties. Extraction of substances from plant materials and their “in situ” formulation in products with specific properties is at the moment one of the very promising applications of supercritical fluids. Other advanced processes are polymer processing in/with supercritical fluids, use of sub-and supercritical fluids as sustainable reaction media, etc. The presentation will give also a limited overview of processes and applications of sub-and supercritical fluids as green processing media. For these processes recent advances and trends of developments will be presented. There are several processes using sub- and supercritical fluids which are already developed to the commercial scale, like dry cleaning, high pressure sterilization, jet cutting, thin-film deposition for microelectronics, separations of value-added products from fermentation broths in biotechnology fields and as the solvent in a broad range of synthesis. All of these applications lead to sustainable manufacturing methods that are not only ecologically preferable but also give the products with very special properties. One of the most important advantages of the use of supercritical fluids is selective extraction of components or fractionation of total extracts. This is possible by the use of different gases for isolation/fractionation of components and/or by changing process parameters. Phase equilibria of sunflower and soybean oils in propane and sulphur hexafluoride (SF6) have been investigated. For both systems, the transition of the two-phase system to one-phase system was observed visually at 25°C and 40°C and at different system compositions generally in the range of 0.2–0.7 weight fraction of propane. High-pressure vapor−liquid-phase equilibria (P−T−x−y) for the soybean oil−SF6 and sunflower oil−SF6 systems were investigated at temperatures of (25°C and 40°C) in the pressure range from (1 to 50) MPa. The phase behavior of two vegetable oils in sulfur hexafluoride (SF6) was studied using an isothermal−analytical method in combination with a visual-synthetic method using a variable-volume cell. Moreover, the phase inversions for the vegetable oil−SF6 systems were also recorded at both temperatures under investigation.