Patent GB-687473-A (GB)
Title: Improvements in or relating to solvent fractionation of refined glyceride oils
IPC: C11B7/00
Filed: 1947-10-09
Abstract: In treating a natural glyceride oil containing a gum or break constituent to separate therefrom a fraction of the more unsaturated glycerides as a polar solvent extract, the concentration of the gum or break constituent is reduced or the constituent is removed, and the oil is then treated with a polar solvent which is but <PICT:0687473/III/1> partially miscible with the oil at normal atmospheric temperatures by countercurrently contacting the oil with the solvent while maintaining the resultant system of oil and solvent below the temperature of complete miscibility of the two.  In order for the solvent to be sufficiently selective, the number of permissible carbon atoms in the molecule of the solvent per polar group must not exceed a maximum which is dependent upon the nature of the polar group.  Data are given for the maximum number corresponding with specific polar groups.  In addition to one or more polar groups the solvents may also contain non-polar groups (such as ethylenically linked pairs of carbon atoms) which, although of lower selectivity-imparting power than the polar groups, may nevertheless increase the selective solvent action of the polar solvent.  Examples of polar solvents which may be used for the fractionation of soya bean oil are n- and iso-propyl alcohol, methyl and ethyl lactate, diacetin, betamethoxy and ethoxy ethanol, furfuryl alcohol, methyl formate, glycol diacetate, ethyl oxalate, methyl levulinate, methyl or ethyl acetoacetate, acetaldehyde, furfural, diuacetyl, acetonyl acetone, nitromethane, nitroethane, propionitrile, trimethyl phosphate and triethyl phosphate.  The removal of or reduction in the concentration of gum in the oil may be effected by alkali treatment (refining) by known methods.  In some cases washing with water by known methods suffices.  The solvent-oil ratio may be 3-30 : 1 and preferably 6-15 : 1.  As shown, alkali-refined soya bean oil is continuously fed to a packed vertical column 10 from the storage container 11 through a conduit 15 and a distributer head 15a which is shown situated near the middle level of the column but may be at any level between the lower and upper quarters of the column.  The conduit 15 may pass through the heat-exchanger 17.  At the same time furfural is continuously fed to the upper part of the column 10 from the container 12 through the feed line 22 which may pass through the heat-exchanger 23.  If desired 1-15 per cent of petroleum naphtha may be added to the oil before extraction.  The temperature or temperature gradient of the column 10 may be controlled by means of heat-exchange jackets or, for large installations, by external heat-exchange elements such as those shown at 24 and 26.  The raffinate fraction is drawn off at the top of the column 10 through the line 36 and passed to the still 38 in which the solvent is recovered and is returned to the container 12 via the condenser 46 and line 48.  The raffinate fraction drawn off from the still through line 41 may then be freed from any remaining solvent by means of the steam stripper 42.  The solution of the extract fraction in the polar solvent is drawn off from the bottom of the column through the line 49.  All of it may be passed through a still 54 for the removal of solvent, which passes via condenser 56, line 57 and part of line 48 to the storage container 12.  The extract fraction from the still 54 may pass via line 58, steam stripper 59 and line 60 entirely to storage, or a portion of the stripped extract fraction may be fed as a "reflux" to the bottom portion of column 10 through line 60A and distributer head 71.  A reflux may also be obtained by drawing off a portion of the extract solution from the line 49 through a line 61, removing the major portion of the solvent in the still 62, drawing off the residual extract fraction through line 67, heat-exchanger 68 and line 69 and introducing the fraction through the distributer head 71 into the column 10. Petroleum naphtha from a container 13 may be substituted for some or all of the reflux of extract fraction introduced into the lower part of column 10, the naphtha being fed to the column 10 through line 14 and heat-exchanger 14a.  In two other examples alkali-refined linseed oil and water-degummed soya bean oil respectively are solvent-extracted with furfural by similar methods and in a fourth example water-degummed soya bean oil is extracted with a mixture of furfural and light petroleum naphtha and additional naphtha is fed as reflux to the column.  The complete or partial removal of the gum constituent from the oil before solvent extraction eliminates the troublesome emulsification of the oil with the solvent which otherwise occurs, e.g. when crude linseed oil or crude soya bean oil is extracted with furfural.  Specification 644,917 is referred to.