Liquid purification or separation – Processes – Liquid/liquid solvent or colloidal extraction or diffusing...
Patent
1990-01-12
1991-12-17
Sever, Frank
Liquid purification or separation
Processes
Liquid/liquid solvent or colloidal extraction or diffusing...
203 16, B01D 1100
Patent
active
050732676
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an improved process for the extraction of volatile compounds with carbon dioxide and to the volatile compounds obtained by this process.
Conventionally, the two most important physicochemical methods for the extraction of substances are distillation and the use of solvents.
It is known that the drawback of distillation is that the mixtures of substances to be separated must be heated the more strongly the lower the vapour tension of the substances to be separated. Distillation reaches its limits when the substances are no longer heat-stable. The use of vacuum certainly widens the field of application of this separation process, but only in a supplementary boiling range of about 100.degree. to 150.degree. C.
Solvent extraction can be used only in a limiting manner, since the choice of the appropriate solvent or solvents frequently presents difficulties, or there is no suitable solvent at all. This method reaches its limits when the solubility properties of the constituents of the mixture to be separated are so close that it is no longer possible to obtain an efficient separating effect. The presence of residual solvents in an amount which is frequently not negligible and indeed significant in the extracts and consequently the perfumed or foodstuff end products has caused consumers to realize the danger of such extracts, which has led to more and more stringent national and international regulations on the use of certain solvents.
All of these problems justify the use of supercritical fluids, which offer most of the advantages sought.
It is known that a gas is in the supercritical state when it is at a temperature and under a pressure greater than those of its critical point (31.degree. C. and 73.times.10.sup.5 Pa for CO.sub.2); this state, fluid, is neither the liquid state nor the gaseous state; its solvent power depends largely on the temperature and the pressure at which it happens to be.
Extraction by supercritical CO.sub.2 is a well-established technique today which can be successfully employed for the recovery of volatile products responsible for aroma. Thus, the extraction is effected by percolating supercritical gas through the starting material, put in an appropriate form, after which the separation of the compounds extracted is effected, preferably, by simply lowering the pressure of the percolation mixture to a pressure below the critical pressure of CO.sub.2, preferably between 45 and 57.times.10.sup.5 Pa. In addition it is possible to lower the temperature to a value below the critical temperature of CO.sub.2 ; the temperature in the separators is, for example, between +10.degree. C. and +25.degree. C. at most, whereas the pressure generally does not exceed 64.times.10.sup.5 Pa.
An extraction process of this type is rapid. Unfortunately, loss of the most volatile compounds or the most polar compounds occur, these compounds being either lost during let-down, when the apparatus is brought back to atmospheric pressure, or lost during the evaporation of the solid carbon dioxide which is formed during let-down, or are not recovered in the separator because the solubility in liquid or supercritical CO.sub.2 is too high.
Various techniques have been proposed to date to improve the recovery of these compounds: modification of the size and the geometry of the separator or bubbling of CO.sub.2 in a solvent, which CO.sub.2 is liberated during the evaporation of the solid carbon dioxide. However, these techniques do not bring sufficient improvement.
The present invention provides a solution to this problem. To this end, it is proposed, according to the invention, to add an appropriate trapping medium in the separator of a supercritical carbon dioxide extractor.
The subject of the present invention is, thus, a process for the extraction of volatile compounds from a starting material with supercritical carbon dioxide, according to which a percolation of supercritical gas through the said starting material is conducted, the carbon dioxide loading with extractable compounds, th
REFERENCES:
patent: 4770780 (1988-09-01), Moses
patent: 4867997 (1989-09-01), Wiesenberger et al.
Adda Jacques
Lorne Jean-Luc
Institut National de la Recherche Agronomique
Sever Frank
LandOfFree
Process for the extraction of volatile compounds with supercriti does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for the extraction of volatile compounds with supercriti, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for the extraction of volatile compounds with supercriti will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-833891