US2394968A

US2394968A - Vitamin concentration

Info

Publication number: US2394968A
Application number: US516295A
Authority: US
Inventors: Leo J Van Orden
Original assignee: MW Kellogg Co
Current assignee: MW Kellogg Co
Priority date: 1943-12-30
Filing date: 1943-12-30
Publication date: 1946-02-12
Anticipated expiration: 1963-02-12

Description

Feb. 12, 1946. J. VAN ORDEN VITAMIN CONCENTRATION Filed Dec. 30, 1943 x fly M (A J07 J J g u h L 5 aw w m mmmm ufil imi 1: m

a N w w a ATTOHZYEYIE Patented Feb. 12, 1946 UNITED STATES PATENT OFFICE VITAMIN CONCENTRATION Application December 30; 1943, Serial No. 516,295

6 Claims.

This invention relates to improvements in the treatment of fatty oils for separating from such oils one, or more than one, fraction superior to the original oil in at least one respect. More particularly the invention relates to improvements in methods of treating such oils with a solvent whose miscibility with the oil decreases with increasing temperature. Still more particularly the invention relates to improvements in the treatment of such oils in a counter-current fractionating process by means of a solvent of the nature of propane.

The invention relates particularly to improvements in such treatments of fatty oils which require close control of operating conditions in order to maintain the proportion of the oil separated at the desired amount. A principal application of the improved process is the treatment of fatty oils to separate a relatively small proportion of the oil as the desired product. An

example of this type of operation is the treatment of natural oils to separate therefrom fractions which are concentrated in vitamins. A second application of the invention is in the treatment of oils whose constituents all have molecular weights of the same order of magnitude in order to separate the oil into fractions in accordance with differences in chemical constituents. An example of this application of the invention is the treatment of a fraction of an oil containing both saturated and unsaturated fatty acids, or esters thereof, to effect separation of the oil into fractions having higher and lower iodine numbers than the original oil. While the last-mentioned treatment represents an important application of the invention, for example in the separation of fatty oils into stocks suitable as drying oils and as soap stock, the invention will be described in detail by reference to the separation of concentrates of fat soluble vitamins from natural oils containing such vitamins. It will be understood, however, that the process illustrated is of broader application as will be apparent from the following description.

The natural oils which are treated for the separation of vitamin concentrates in accordance with the improved process include oils obtained from fish, animal and vegetable sources. However, inasmuch as fish oils, such as fish liver oils and fish body oils, constitute the most fruitful present source of fat-soluble vitamins the invention has particular application to the treatment of fish oils. These include liver oils, such as those of the cod and halibut, which are sources of vitamins A and D, and various shark liver oils which are sources principally of vitamin A. The various fish body oils,-a1so may be treated to produce concentrates of oil vitamins A and D.

Vitamin containing oil may be treated to produce concentrates thereof at relatively low temperatures by means of solvents for such oils, or portions thereof, whose miscibility with the oils decreases with increasing temperature. Such solvents ordinarily are normally gaseous and must be employed under conditions of substantial superatmospheric pressure in order to provide the required degree of miscibility of the solvent with the vitamin oil. The solvent and vitamin oil are contacted under sufficient superatmospheric pressure and at a temperature efiective to cause the formation of two homogeneous mirtures of the solvent and the oil which represent immiscible liquid phases of differing densities. The lighter phase consists principally of the solvent and a portion of the oil. The heavy phase consists of the remainder of the oil and a small proportion of the solvent. It is found that the separation of the oil in this manner concentrates the vitamins in one or the other of the oil fractions contained in the two phases. For example, in the treatment of various fish oils containing vitamin A or vitamin D it is found that the fraction of the oil contained in the lighter phase is concentrated in these vitamins as compared to the original oil.

The concentrating step may be carried out in batch operations in which the mixture of solvent and oil is brought to the temperature and pressure at which the oil is distributed between the phases in the manner effective to produce the desired concentration of the vitamin content of the oil. The phase containing the vitamin concentrate is then'treated to separate and recover the oil content thereof from the accompanying solvent, the latter being recycled to the concentrating step. Likewise solvent is recovered from the other phase for reuse.

The solvents employed for concentrating vitamins in the process on which this invention is an improvement, are those whose miscibility with the vitamin oil decreases as the temperature increases in a range substantially below temperatures at which there occurs thermal decomposition, or other chemical alteration, of the vitamin oil. Preferably, the solvent employed is one having a critical temperature well below the decomposition temperature of the vitamin oil and one whose miscibility with the oil decreases as the temperature is increased in the range from a temperature 'sufilclently lower than the critical temperature of the solvent to produce complete miscibility of the solvent and oil to ahigher temperature, as much as 50 F. above the critical temperature of the solvent, at which the solvent and oil are substantially immiscible. The low molecular weight hydrocarbons are particularly advantageous for use in the process as solvents, and of these the low molecular weight paraflin hydrocarbons are especially useful because they are inert to substantially all constituents of vitamin-containing oils. Consequently, the low-boiling normally gaseous and normally liquid parafiln hydrocarbons such as methane, ethane, propane, the butanes, and the pentanes are preferred for use as solvents in the process although the use of the corresponding olefin hydrocarbons is not excluded. The preferred solvent for the process, by reason of its miscibility with the oils at relatively low temperatures and the relative ease with which it can be liquefied, is propane. While the paraflin hydrocarbon solvents preferably are employed in the relatively pure state, mixtures thereof may be employed with advantage. For example, mixtures of ethane and propane, or mixtures of butane and methane may be employed to produce solvents having the desired properties. The low-boiling hydrocarbons are particularly advantageous for use in the present process as solvents, but other solvents having relatively low critical temperatures may be employed, such as ammonia and halogenated hydrocarbons such as dichlordifluor methane.

In the concentration of fat soluble vitamins by this method it is found necessary ordinarily to separate from the oil a relatively small proportion thereof as the concentrate. For example in the concentration of vitamins A and D in various fish oils it is desirable ordinarily to effect a ten-fold concentration of the vitamins. This ordinarily requires including in the light phase no more than about of the oil charge. Excluding all but this small proportion of the oil from the light phase requires maintaining the latter at a maximum temperature in the range of temperatures in which small changes produce great changes in the miscibility of the solvent with the oil. For example in an operation in which 7% of the oil is included in the light phase, to produce a ten-fold concentration at an eiliciency of 70%, a decrease of 1 F. in the temperature may increase the proportion of the oil included in the light phase to about 10% with a loss of about 20% in the vitamin concentration. Since it is diillcult to control the temperature within 1 F., particularly in a continuous operation, it is evident the regulation of the concentration, at high degrees of concentration, presents a serious problem in operation.

The separation of fatty oil fractions whose constituents all have molecular weights of the same order of magnitude into subfractions difiering substantially in their degrees of unsaturation presents an equally serious problem. In such separation a change of 1 F. in the temperature makes an even greater change in the proportion of the oil fraction included in the light phase.

It is an object of this invention to provide an improved method of operation in which close regulation of the separation of fatty oils, such as the degree of concentration of the vitamin oil, is accomplished relatively easily.

The invention will be described in detail by reference to the accompanying drawing which illustrates diagrammatically apparatus suitable for use in various embodiments of the invention.

In the drawing Fig. 1 illustrates an embodiment of the invention in which the solvent and the vitamin oil are passed concurrently first through a mixing chamber and then into a settler to separate the two phases.

Fig. 2 illustrates an embodiment of the invention in which the solvent and oil are passed counter-currently through an extraction tower at the necessary temperature and pressure.

Fig. 3 illustrates an embodiment of the invention in which the solvent and oil are passed counter-currently through an extraction tower and the tower is provided with means for refiuxing to increase the degree of concentration of the vitamin oil. Fig. 3 also illustrates a method of separating, and returning for reuse, the solvent in the light phase.

In Fig. l the vitamin oil is introduced into the system through line 10 which is provided with a pump II and heating means 12. The solvent employed in the operation, which will be referred to as propane by way of example,

is introduced into the system through line I3 which is provided with a pump I4 and heating means i5. Lines I0 and I3 connect with a mixing chamber I6 which is integral with a large settler H. The solvent and oil are mixed by passage thereof through chamber l6 which is provided with suitable baflles or other means for effecting intimate contact of the oil and the solvent. The oil and solvent are preheated at 12 .and i5 to the temperature at which it is desired to maintain the mixing and settling zones. Alternatively the mixture may be heated to the desired temperature. Instead of preheatin both the oil and the solvent, one or the other, preferably the solvent, is preheated to a slightly higher temperature than the temperature desired in the extraction zone and the superheated material is contacted with the other component of the mixture in an unheated condition whereby the resulting mixture is at the desired temperature.

The mixture of oil and solvent is discharged from chamber l6 into settler I! in which the liquids are maintained sufliciently quiescent to permit complete separation of the phases. This is assisted by the provision of a baifie member 18 in settler I! which restricts the turbulent portion of the mixture of solvent and oil to one end of settler l1. Separation of the phases is accomplished substantially in that end of settler l1 and the heavy and light phases flow under and over balfle I 8 into the more quiescent portion of settler IT in which substantially complete separation of the phases is effected. The heavy, or bottom, phase is withdrawn by means of a drawofi' leg l9 which provided additional time for the separation of any light material occluded in that phase. The heavy phase is withdrawn from the leg l9 through line 20 which is provided with a valve 2| I The light phase in settler I1 flows over baffle 22 into the end section of settler l1. Any heavy material which is occluded therein is permitted to settle into the bottom of this section from which it may be drawn off continuously or intermittently through line 23, provided with a valve 24. The light phase is withdrawn from settler I! through line 25 which is provided with a valve 26.

In the treatment of a fish oil, such as a fish liver oil, to concentrate vitamin A the proportions of oil and propane introduced into the mixer l6 and the temperature and pressure employed are regulated to distribute the oil in the phases separated in settler I! such that the required proportion of the total oil charged is included in the upper, or light, phase. This proportion is governed by the degree of concentration desired and the efiiciency of separation of the vitamins in the concentrate phase. For example, if a ten-fold concentration is desired no more than 10% of the oil should go in the concentrate phase and this amount should be reduced in the proportion by which the efficiency of vitamin separation is less than 100%. Depending upon the character of the oil and the other conditions a ratio of 10 to .100 parts of propane to 1 partof oil is desirable. The pressure employed necessarily must be sufiiciently high to insuremaintaining liquid phase conditions duringthe operation. Ordinarily a pressure of about 50 pounds per square inch higher than the vapor pressure of the solvent at the highest operating temperature is satisfactory a1- though higher pressures are not excluded. The

required temperature necessarily is aiTected by the pressure, the propane-oil ratio, and the degreeof concentration desired. For effecting concentrations with propane the optimum temperature ordinarily will be in the range of 165 to 210 F. In thisimproved method of operation it is preferred'to operate at temperatures not higher than the critical temperature of the propane phase.

The light phase withdrawn through line 25 is reduced in pressure to permit separation of the oil and propane. Prior to such separation, or after partial separation, .the oil may be treated in propane solution to effect further refinements. For example it may be subjected to neutralization to remove free fatty acids.

To control the degree of concentration efiected in the apparatus illustrated in Fig. l the product withdrawn as a component of the light phase in line 25 is frequently examined for bulk and quality. It is found that these vary considerably w with minor changes in the temperature in settler 11. When efiecting concentrations of the order of magnitude of the ten-fold concentration described above in which less than 10% of the feed isincluded in the propane phase the temperatures necessarily are so close to the temperature of'complete immiscibility of the propane with the oil that minor changes in temperature effect great changes in miscibility. In efiecting concentration of the oil to that degree it is found that variations of as little as 1 F. in the temperature produces considerable variations in the degree of concentration of the oil. Since the regulation of the temperature within such a limit is extremely diflicult the final and exact control of the degree of concentration effected in settler I1 is provided in accordance with this invention by control of the pressure on that vessel.

The temperature in settler I1 is controlled as closely as possible by controlling the temperature of the entering components of the mixture contained therein to produce the desired distribution of the oil in the phases. Closer control of such distribution is maintained, however, by regulating the pressure on vessel 11, preferably by manipulation of valve 26. Opening valve 26 ,sufllciently to produce only a slightly increased flow of the upper phase therethrough substantially lowers the pressure in vessel ll. This reduces the miscibility of the oil with propane and reduces the proportion of the oil which is included in the light phase. Consequently, if tests of the products withdrawn through line 25 indicate insuflicient concentration of the vitamins valve 26 is opened slightly to reduce the pressure. Conversely if the proportion of the fresh feed in the upper phase is less than that desired it can be increased by slightly constricting valve 26 to increase the pressure existing in vessel l1. This renders the oil and propane more miscible and increases the proportion of the oil included in the upper phase.

More eflicient concentration of the vitamin oil is provided by counter-current contact of the propane in the oil as illustrated in Fig. 2. Referring to Fig. 2 the oil from which a concentrate is to be extracted is introduced into extraction tower 21 by means of line 28 which is provided witha pump 23 and heating means 30. The propane is introduced into tower 21 by means of line 3| which is provided with a pump 32 and heating means 33. Suitable'baflle members are provided in tower 21 to insure intimate contact of the propane and the oil. The propane stream flows upwardly through tower 2'1 counter-current to a descending stream of vitamin oil which is thus stripped of the portions thereof which are miscible with the propane at the temperature and pressure employed. The conditions are regulated to efiect the inclusion in the propane phase oi the desired proportion of the oil charge. The unabsorbed material collects in the bottom of tower 21 and is withdrawn through line 34 provided with a valve 35. The propane phase, containing the more readily miscible oil which may include the desired vitamin concentrate, is withdrawn overhead through line 38 provided with a valve 31. The temperature in the tower 21 is controlled primarily by proper preheatin of the material charged thereto at 30 and 33. Final control of the degree of concentration is provided by varying the pressure in the manner described in connection with Fig. 1. Since the volume of material withdrawn through line 36 is ordinarily greater than that withdrawn through line 34 the tower pressure can be controlled conveniently by suitable regulation of the valve 31 in a manner similar to that described in connection with valve 26 of Fi l.

The method of concentration of fat soluble vitamins illustrated in Fig. 3 is superior to those of Figs. 1 and 2 in that it permits a great degree of concentration while recovering in the concentrate a maximum proportion of the vitamin content of the original oil. The method of operation illustrated in Fig. 3 is superior for the reasonthat it provides for a rectificationof the extracted oil whereby a greater proportion of the vitamin content of the oil charge is recovered in the concentrate than is possible by the methods of operation of Figs. 1 and 2. Tower 38 of Fig. 3 difiers from tower 21 of Fig. 2 principally in that the oil is charged to tower 38 from line 39. provided with heating means 40 and a pump 4|, at an intermediate point in the tower, and in the-provision of heating coils 42 in that portion of tower 38 above the oil charge point.

Propane is charged to tower 38 from line 43 which connects with storage drum 44 and is provided with heating means 45 and a pump 46.

Towers 38 is operated in a manner whereby a maximum temperature is maintained in the top of the tower and a minimum temperature is maintained in the bottom of the tower. The temperature in the bottom of the tower is controlled conveniently by introducing propane from line 43 at the temperature desired at that point. The oil introduced through line 39 may be heated to the same temperature, whereby the temperature in the tower is substantially uniform between the oil and propane charge points, or the temperature at the point of introduction of the oil may be maintained substantially above the minimum, bottom, temperatute of tower 38. This may be accomplished by superheating the oil introduced through line 39 or heating coils (not shown) may be provided below the oil charge point.

That part of tower 38 between the charge points functions principally as an absorption zone, regardless of the presence or absence of a temperature gradient. The oil from line 39 which is unabsorbed at the charge point in the stream of propane flows downwardly against the upwardly rising stream of propane by reason of the greater gravity of the oil phase. As the oil flows downwardly it comes incontact with propane which is less saturated with respect to the oil whereby more and more of the oil is absorbed in the propane phase. The existence of a temperature gradient in the absorption zone, whereby the oil comes into contact with cooler propane as it descends the tower, also facilitates the absorption of oil by the propane phase. The unabsorbed oil, which contains propane in solution therewith, is permitted to collect in the bottom of tower 38. Ordinarily the interface between the propane phase and the oil phase is maintained below the propane charging point, as is illustrated in Fig. 2. However, it may be desirable, in order to obtain an intensified stripping effect, to maintain the interface a substantial distance up the tower and above the propane charging point, as illustrated in Fig. 3. This lower phase is withdrawn from tower 38 through line 41 which is provided with a valve 48.

Above the oil charge point the upwardly rising propane phase is heated to progressively higher temperatures, as it moves up the tower, to a maximum temperature in the top of the tower. As the propane stream containing abso-rbed oil passes upwardly through this portion of the tower from a point of relatively low temperature to a point of relatively high temperature the less soluble portions of the dissolved oil are precipitated as a separate, and heavier, phase containing a substantially lesser proportion of propane than the propane phase. Such precipitated oil flows downwardly from the point of precipitation in counter-current contact with the upwardly flowing propane stream. As this precipitated phase flows downwardly it passes from a zone of higher temperature to a zone of lower temperature at which the capacity of the propane stream to absorb the oil is greater than that at the temperature at which the heavy phase was precipitated. Consequently the propane stream tends to reabsorb oil precipitated from the propane phase at a higher temperature and at a higher point in tower 38. This continuous absorption, precipitation, reabsorption, reprecipitation, etc., in tower 38 above the oil charge point provides highly efficient rectification of the vitamin o-il whereby efficient separation of that portion of the oil containing the vitamin content thereof is effected. For example, in the fractionation of fish oils to separate vitamins A and D the method of treatment just described permits a greater degree of recovery of the vitamin content of the oil in the concentrate which is contained in the propane phase withdrawn from the top of the tower.

The maximum temperature employed in tower 38 is maintained ordinarily at the top of the tower. This temperature may be higher than the critical temperature of the propane or other solvent, but it is preferred ordinarily to operate at temperatures below the critical temperature. The temperatures ordinarily used fall within the range of temperatures between the critical temperature and 30 F. below the critical temperature. In this range relatively low maximum temperatures are employed for the top temperature in the tower when'operating the tower to take overhead a relatively great proportion of the oil feed whereas higher temperatures are employed to take overhead smaller proportions of the oil feed. The top temperature in tower 38 is maintained at the level at which the desired proportion of the oil remains absorbed in the propane phase. For any particular combination of oil and solvent the top temperature is selected, with reference to the ratio of solvent to oil charged to the tower, to maintain the proportion of the oil which remains absorbed'in the propane phase at the desired figure. As the proportion of oil absorbed is greater when relatively high ratios of propane to oil are employed it is evident that relatively high top temperatures are employed when using relatively high ratios of solvent to oil in order to restrict. the proportion of oil which remains absorbed in the solvent phase to the desired figure.

The temperature at the bottom of the tower is maintained as low as feasible to maintain the efilciency of absorption at a high level. However, this temperature must be maintained above the temperature at which complete miscibility of the solvent and oil occur. The preferred bottom temperatures ordinarily are 40 to 50 F. or more below the critical temperature of the solvent. When employing propane as the solvent to effect the concentration of fish oil containing vitamin A or vitamin D, or both, the combination of a top temperature of 190 to 210 F. with a bottom temperature of to F. is effective to produce substantial concentration of the vitamins. The temperature at the oil charge point may be the same as the bottom temperature. This facilitates absorption of oil in the propane phase but, on the other hand, the provision of a slight temperature differential between the bottom temperature and the temperature at the oil charge point effects rectification of the oil in the tower below the oil charge point. It is found ordinarily, however, that a differential of at least 10 F. should be maintained between the oil charge point and the top of the tower.

The propane stream may be heated by a series of heating means, as shown, to gradually raise the temperature throughout the portion of the tower above the oil charge point, or the oil may be heated to the desired maximum temperature at a single point above the oil charge point. However, the latter method would concentrate the precipitated material at that point to a degree which may interfere with eflicient settling. A true temperature gradient is preferred therefore to distribute the precipitated material in the tower in a manner which promotes efficient rectification.

The propane phase containing the desired proportion of the fish oil charge is withdrawn from liquid phase and as a gas passes overhead in separator 52 and the oil is- The propane is withdrawn overhead through line 53 which is provided with cooling means 54 and conthe top of tower 38 through line 49. Avalve 50 is provided in line pressure on tower 38 and, secondarily, the rate of withdrawal of the propane phase from tower 38. The pressure in line 49 onthe exit side of valve 50 is permitted to be sufficiently low to eflect substantial evaporation of the propane and this effect is promoted by heating the mixture at Line 49 connects with a Separator 52 in which the oil and propane are permitted to separate as a phase. The propane collected in the bottom of separator 52.

nects with storage drum 44. In this manner the propane is returned for reuse. Make-up propane is introduced into the system through line 55 which is provided with pump 55 and connects with line 53.

The oil separated in the bottom of separator 52 is withdrawn through line 51 at a rate eilective to maintain a constant liquid level therein. Any necessary variations in the rate of withdrawal are provided for by suitable control means connecting liquid level control 59 and pump 58. Variations in the rate of flow of liquid through line 51 are recorded by the meter 60 in line 51 and valve 50 is then adjusted with each change in the rate of flow as reflected at meter 60 to maintain the flow through line 51 at a rate corresponding to the desired degree of separation of the oil.

If the temperature in tower 38 rises slightly there is an immediate decrease in the quantity or oil carried overhead through line 49. This is reflected immediately by a lowering of the liquid level in separator 52 as a result of which control means 59 operates to decrease the rate of withdrawal of liquid through line 51 to maintain the liquid level in 52. The decreased rate of flow is recorded at meter 60, in response to which valve 50 is closed slightly. This has the effect of raising substantially the pressure on the liquids in the interior of tower 38. This increases the miscibility of the propane phase with the oil and increases the proportion of oil in the propane phase withdrawn through line 50. This effects the restora= tion of the proportion of oil taken overhead to the figure at which it was prior to the decrease in temperature. The increased amount of oil taken overhead and separated in separator 52 tends to raise the liquid level at that point, with a resulting automatic increase in the rate of withdrawal of liquid product by means of pump 58. Since it is much easier to control the pressure on the tower by this means, than it is to control the temperature, this method of control permits much closer regulation of the quantity of the oil taken overhead in the propane phase.

By an alternative method of controlling the operation of tower 38 pump 58 is set to withdraw liquid through line 51 at a constant rate corresponding to the desired degree of separation of oil in the overhead phase. Suitable automatic control means 59 is connected to valve 50 wherebi valve 50 is opened and closed slightly in response to variations in the liquid level in separator 52. When this method is employed separator 52 preferably is substantially elongated whereby slight changes in the quantity of oil introduced through line 49 are reflected by substantial changes in the liquid level.

While the control methods discussed above are based on responses to variations in the quantity 9 to regulate, primarily, the

of oil taken overhead the invention also includes within its scope the regulation or the pressure in response to variations in the quality of the oil. By such means variations in the vitamin concentration of the charge oil are compensated for to produce an overhead product of constant concentration.

The pressure employed in the extraction zone is maintained sufliciently above the'vapor pressure of the solvent employed to permit substantial variation in the tower pressure without reducing it to a point below the vapor pressure of the solvent. Ordinarily a maximum operating pressure of 50 pounds per square inch higher than the vapor pressure of the solvent is sufliciently high since adjustments of 10 to pounds in the operating pressure are suflicient to counteract whatever temperature variations ordinarily occur in the operation of the tower. However, if experience shows that greater variations are to be expected a higher operating maximum pressure should be employed.

I claim:

1. A method for treating a fatty oil to efiect separation thereof into a plurality of fractions having different properties which comprises continuously contacting said oil with a liquefied normally gaseous solvent in a mixing zone in a ratio and under conditions of temperature and superatmospheric pressure such that the miscibility of the solvent and oil decreases as the temperature rises and said oil and solvent form solvent and rafilnate phases between which the oil is divided in a predetermined proportion to produce in said solvent phase an oil component representing the proportion of said oil desired in said component, continuously withdrawing portions of the two phases from said zone, and then varying the pressure in the mixing zone directly with variations in the proportion of said oil in said solvent phase to maintain the desired distribution of the oil in the phases.

2. A method for treating a vitamin containing oil to separate therefrom a portion containing vitamins in higher concentration than in said oil which comprises continuously contacting said oil with a liquefied normally gaseous solvent in a mixing zone in a ratio and under conditions of temperature and superatmospheric pressure such that the miscibility of the solvent and oil decreases asthe temperature rises and said oil and solvent form two phases between which the oil is divided in a predetermined proportion to produce in one phase a vitamin oil component having the vitamin concentration desired in the concentrate product of the operation, continuously withdrawing portions of the two phases from said zone, and then varying the pressure in the mixing zone inversely with variations in the vitamin concentration in said vitamin oil component to maintain a distribution of the oil, in the phases corresponding to the concentration of vitamins desired in the product.

3.' A method for treating a vitamin containing oil to separate therefrom a portion containing vitamins in higher concentration than in said oil which comprises continuously contacting said oil with a liquefied normally gaseous solvent in a mixing zone in a ratio and under conditions of temperature and superatmospheric pressure such that the miscibility of the solvent and oil decreases as the temperature rises and said oil and solvent form an upper phase containing solvent and a portion of said oil enriched in vitamins, continuously Withdrawing a portion of said upper phase, and then varying the pressure in the mixing zone inversely with variations in the vitamin concentration of the oil component of said upper phase to maintain in said upper phase a proportion of the oil which corresponds to the vitamin concentration desired in the product.

4. A method for treating a vitamin containing oil to separate therefrom a portion containing vitamins in higher concentration than in said oil which comprises continuously contacting said 011 with a liquefied normally gaseous hydrocarbon solvent in a mixing zone in a ratio and under conditions of temperature and superatmospheric pressure such that the miscibility of the solvent and oil decreases as the temperature rises and said oil and solvent form two phases between which the oil is divided in a predetermined proportion to produce in one phase a vitamin oil component having the vitamin concentration desired in the product, continuously withdrawing portions of the two phases from said zone, and

. then varying the pressure in the mixing zone inversely with variations in the vitamin concentration in said vitamin oil component to maintain a distribution of the oil in the phases corresponding to the concentration of vitamins desired in the product.

5. A method for treating a vitamin containing 011 to separate therefrom a portion containing vitamins in higher concentration than in said oil which comprises continuously contacting said oil with a liquefied propane solvent in a mixing zone in a, ratio and under conditions of temperature and superatmospheric pressure such that the miscibility of the solvent and oil decreases as the temperature rises and said oil and solvent form two phases between which the oil is divided in a predetermined proportion to produce in one phase a vitamin oil component having the vitamin concentration desired in the product, continuously withdrawing portions of said phase containing the vitamin concentrate, and then varying the pressure in the mixing zone inversely with variations in the vitamin concentration 0! said vitamin oil component to maintain a distribution of the oil in the phases corresponding to the concentration of vitamins desired in the product.

6. A method for treating vitamin containing oil to separate therefrom a portion containing vitamins in higher concentration than in said oil which comprises passing through a contact zone a liquefied normally gaseous solvent, continuously introducing said oil into said contact zone and into said stream of solvent, maintaining the ratio of solvent to oil and conditions of temperature and superatmospheric pressure in said contact zone such that the miscibility of the solvent and oil decreases as the temperature rises and said oil and solvent form two phases between which the oil is divided in a predetermined proportion to produce in one phase a vitamin oil component having the vitamin concentration desired in the product, continuously withdrawing said vitamin containing phase, and then varying the pressure in said contact zone inversely with variations in the vitamin concentration in said vitamin oil component to maintain a distribution of the oil in the phases corresponding to the concentration of vitamins desired in the product.

LEO J. VAN ORDEN.