Patent GB-626924-A (GB)
Title: Improvements in or relating to the production of vitamin concentrates
Filed: 1944-05-16
Abstract: Concentrates of vitamins, e.g. A or D, are obtained from oils such as animal or vegetable oils, especially fish oils, by fractionation with a solvent having a critical temperature well below the decomposition temperature of the oil, preferably below 450 DEG  F., and whose miscibility with the oil decreases as the temperature increases in the range near the critical temperature, to form an extract phase and a raffinate phase, flowing the extract phase upwardly under conditions of increasing temperature to precipitate a portion of the oil and recovering the vitamin concentrate from the extract phase. The extraction is preferably carried out in a vertically extended fractionation zone, having a solvent inlet and a raffinate phase outlet near the lower end, an extract phase outlet near the upper end and a charge oil inlet at an intermediate part of the said zone, the temperature being increased with elevation in at least part of the zone and being in the range near the critical temperature in which the miscibility of the oil decreases with increasing temperature. The process thus consists of an absorption step in which the solvent absorbs a part of the oil to give a lighter solvent phase and a heavier oil phase and a rectification step in which the solvent phase flows upwards through a zone of increasing temperature.  The oil phase moves downwards and the temperature may optionally be decreased in its direction of flow to a minimum at the raffinate phase outlet. The process may be carried out in a single tower or two or more towers may be used.  Preferably, the temperature ranges from at or just below the critical temperature at the top of the tower to about 40-50 DEG  F. below the critical temperature at the base.  Suitable solvents are the low molecular weight hydrocarbons, particularly the paraffin hydrocarbons and mixtures thereof, e.g. methane, ethane, propane, the butanes and the pentanes, but ammonia, dichlorodifluoromethane and halogenated hydrocarbons in general may also be used.  Specified vitamin containing oils are cod, shark and halibut liver oils and fish body oils.  Preferred embodiments of the invention incorporate as additional features the dilution of the oil with the solvent prior to its introduction into the tower; the evaporation of the solvent from the vitamin concentrate and return of said solvent to the rectification zone; and a neutralizing step in which the concentrate is treated with caustic alkali to remove free fatty acids which are separated and stripped with steam.  In modified processes part of the solvent phase is drawn off from a point in the upper half of the tower, heated to separate out an oil phase and either of these phases may be returned to the original or to a fresh rectification zone or may be extracted to recover a vitamin concentrate.  In examples: (1) and (3) shark liver oil is rectified with propane in a tower to give a vitamin A concentrate from the solvent phase; (2) the oil phase obtained from (1) is given a further rectification treatment as in (1) and an additional quantity of vitamin A concentrate is obtained from the solvent phase which is mixed with the overhead product from (1) and is refractionated to give a concentrate of increased potency; and (4) dogfish liver oil is treated as in (1) to give a vitamin concentrate.  The Specification as open to inspection under Sect. 91 comprises also a process for the production of a vitamin concentrate by contacting an oil with a low boiling solvent within a range between 100 DEG  F. below the critical temperature and a few degrees above the critical temperature to obtain two phases and isolating the vitamin-enriched oil from the phase containing it, the temperature not being substantially higher than 450 DEG  F.  This subject-matter does not appear in the Specification as accepted.