YING IL

YING

IL

A sgmposfurn presented under joint sponsorship of the Unbersitg of Minnesota and tlcc Minnesota Secttan, American Chemicd Societg, Minneapolis, Minn., March 27 to 29, IS47

Herbert J. Passino The M. W . Kellogg Company, Jersey City, N. J .

A review of the techniques arid principles involved in the

Process Operation

new Kellogg Solexol process is given. The Solexol process is concerned primarily with the countercurrent extraction of animal, vegetable, and marine oils and fats, using liquid propane as a solvent. Various schematic diagrams are presented depicting the application of the process to the refining and fraetionating of oils such as menhaden, sardine, soybean, linseed, cod liver, and tall oils. Accnmpanying tables give various properties of the fractions obtained from the different oils by the application of the Solexol process.

Figures 1 and 2 illustrate the Solexol countercurrent extraction process. One is a general flow without neutralization; the other pictures practically the same operation with neutralization. In these figures, a reflux stream is shown running from the bottom of the strippr back to the tower. In subsequent figures, this has not always been illustrated, but it should not be assumed that it was not used. Reflux Tms used in most of the cases cited but eliminated in the drawings for purpoves of simplicity. This is also the case for propane addition in niultitoiver operation. In Figure 6, propane is added a t the bottom of the various towers, but this is not shown in other multitower systems. Howcvcr; small amounts of propane are added customarily t o the bottom of each tower. During thc first stages of the work while much was being learned about the process, all of the oils were treated with caustic to remove the fatty acids, so that a t that time the bothcrsome problem of forming soaps in the presence of these oil2 and the expenditure of considerable time and effort attempting to rcmove these soaps was still encountered. It has more recently been demonstrated conclusively that it is possible to eliminate the use of caustic in the complete refining of oils, such as corn, soybean, cottonseed, linseed, and others. It is, however, in some instances, still desirable to employ caustic. For example, when attempting to concentrate vitamins or sterols and other similar derivatives from fish liver oils and the like, often it is advantageous to remove the fatty acids prior to the fractionation operation. The necessity for this will be discussed a t more length later in this paper.

HE purpose of this paper is to explain the principles involved in the new Kellogg Solexol process for the separation and refining of vegetable oils. In many years of research in the petroleum field, there have been developed processcs and techniques which might be applicable in the glyceride processing field. One of the topics studied extensively, and for which a large number of commercial units were designed and fabricated in the petroleum field, was that of countercurrent extraction. Six or eight years back, it was decided that it might be advantageous to loolc rather closely into the possibilities of the application of some of these techniques to the refining of oils other t,han petroleum. After a study of the commercial methods being used a t that time in the glyceride industry, and after securing a working knowledge of some of the problems which still existed in this field, in collaboration with The Chemical Foundation, an attempt was made to develop a continuous process for conducting some of these glyceride refining operations. The bibliography given here shows the scope of the previous work on solvent extraction of vegetable oils and fats. The studies carried out were for the most part incomplete and on a batch basis: thePe were used to develop and expand solvent refining and to demonstrate its applicability on a continuous basis. Although the major port,ion of the early work was carried out on the concentrat,ion of vitamins, studies were conducted also on natural oils which one ordinarily encounters in the drying oil field. Some of the data discussed here may seem only remotely related to the drying oil question, but such material has been included to give the reader a more rounded background on the possibilities of this process, as well as to enable him to obtain a broader conception of the principles involved. Perhaps the best way to initiate a discussion of the application of the Solexol process to glyceride oils is first to delve into t,he question of the mechanics and the principles involved.

SEPARATION

The various technique3 employed in operating the procoss (Figure 1) can be explained by the refining of tallov, an operation which involves merely the separation of color bodies. Only two fractions are produced-namely, a small one containing thc color bodies, oxidized fats, etc., and a large one which is a tallow product much improved in color over the charge material. Although the refining of tallow has little to do with the drying oil question, the principles involved in handling this separation are the same as are encountered in carrying out the more complcx separations on soybean oil, menhaden oil, cod livcr oil, etc. Thc crude stock, in this case tallow, enters the middle of the tower, while the liquid propane enters the bottom. The propane i3 pumped into the extraction tower under a pressure sufficient to keep it in liquid form a t the desired operating tempcraturo. 280

INDUSTRIAL AND ENGINEERING CHEMISTRY

February 1949

281

concentrate the glycerides selectively in the propane phase, while rejecting the insoluble color bodies, the oxidized fats (which contain more active groups than the fats themselves), and other complex materials. TEMPERATURE

I I

I

fl

r xN5oL U B L E S

Figure 1. General Flow without Neutralization

The temperatures in the extraction tower are regulated in such a way that approximately 99% of the tallow is dissolved, while the remaining 1% flows to the bottom of the tower as an insoluble phase. In this way, 99% of the tallow dissolved in the propane passes out the top of the tower into a stripper where, by dropping the pressure, volatilization of the solvcnt occurs. The stripper shown here is a so-called high pressure stripper-that is, it is operated in the vicinity of 300 pounds, so that this propane may be recycled after condensation without the necessity of recompressing it back from atmospheric to the operating pressure. Commercially, the remainder of the propane is removed a t atmospheric pressure in another stripper which is not shown in Figure 1. This steam treatment, in the case of tallow, can be and usually is eliminated. Provisions are made (Figure 1) for refluxing the top of the tower by recycling some of the oil from the bottom of the stripper to the tower. Referring back to the extraction tower, the bottoms, or insoluble phase, is withdrawn from the bottom along with a small amount of propane, usually 0.6 to 0.7 volume of propane per volume of oil, and goes to another stripper (not shown) where the last traces of propane are removed for recyling purposes. The net result of such a separation is to divide the tallow stock into two fractions: an insoluble fraction made up largely of color bodies, oxidized fats, and materials which are somewhat complex in structure; and a refined overhead product. In the case of tallow, starting with a dark brown tallow and removing a 2% bottoms fraction, it is possible to produce a 9Svo overhead fraction with a color of approximately 10Y-2R in a 5.25-inch Lovibond cell. SOLVENT

For the most part the solvents used in the process were propane or one of the other low molecular weight hydrocarbons. A number of solvents were investigated, but in the caRe of each oil, considering all the factors involved, economic and otherwire, one of the lighter paraffins appeared to be the best solvent. This was so in any c w with regard to the solvents which have been investigated thus far. Propane is a nonpolar solvent. It is possible, as a result, that those derivatives of less complexity-that is, those having fewer active groups in the molecule-would be more soluble in such a solvent than would be derivatives of higher complexity. In the caSe of the tallow example cited, since color bodies are practically always derivatives containing many active groups, they might be less soluble in a solvent such as propane than would be an ester, such as a triglyceride. Therefore, i t may be possible to

The next question to arise in carrying out surh a n extraction ir one of control of the amount of material rejected. I n such a countercurrent extraction, this can best be explained as follows: Referring once again to the tallow, if one contacts tallow with propane under pressure a t room temperature, it is found to be completely soluble. In these studies, however, it was noted that as the temperature was increased to a given temperature level which will be referred to as the phase point of that oil, two phases began to appear. In other words, although a t r w m temperature the tallow and propane were completely miscible, by the tinic 150' F. was reached, the development of an additional phase was noticed. As the temperat,ure was increased and approached the critical temperature of the solvent the amount of this phase increased steadily. This is contrary, of course, to the temperature effect which is noted with ordinary liquid solvents, where a temperature increase usually results in an increased solubility rather than a decreased one. The reason for this reversal of the temperature effect, in the case of propane, is that the solvent has a low critical temperature-namely, about 206' F. If a solvent such as propane is maintained in the liquid form under pressure and approaches the critical temperature by the gradual introduction of heat, there will be a marked density variation. Since the solubility of any component included in this work depends primarily on the density of the solvent involved, there will be a gradual decrease in solubility as the density of the solvent drops. Therefore, as the critical temperature of propane is approached and as the density continues to drop, there will be less and less of a given material in solution. At any one temperature, a specific amount of oil will be dissolved and, in turn, a corresponding amount of insoluble phase formed. This so-called insoluble phase can be adjusted at will by a variation of tcniperature in the tower a t a given pressure. Thus, in a single tower, after introducing an oil, the fraction removed from the bottom of the tower may vary anywhere from 0 at lower temperatures t o 100% if the operating temperature in the tower is raised t o the vicinity of the critical temperature of the propane. DENSITY AND COMPLEXITY OF COMPONENTS

I t has been found that two fundamental characteristics of a compound control its degree of solubility in a given hydrocarbon solvent. These two characteristics are first, molecular weight, and secondly, degree of complexity. Because of this, many oils can be separated into numerous interesting and valuable fractions. The use of a solvent such as propane in a countercurrent estraction operation as described introduced mother interesting aspect of the prineiples involved when working near the critical temperature of a given solvent. It is, of course, not necessary nor is it usually desirable to maintain the temperature a t a constant value throughout the tower. For example, if the temperature at the bottom of the tower where the propane is introduced is maintained at 150' F., a t the top of the tower a t 170' F., and if a uniform gradient exists between the top and bottom of the tower, then with the one solvent, propane, a series of solvents are available in the tower. By maintaining the temperature gradient an appreciable change in the density of the propane has been effected a t any given point in the tower. In other words, a t the bottom of the tower, the density may be 0.5, whereas higher up in the tower, because of the increase in temperature and the proximity to its critical temperature, the propane may drop off in density to 0.4 or lower.

282


Thus, by regulating conditions so that the solvent is at different density levels, there are essentially a great number of solvents present; or in one tower, all the advantages which might be gained by having present a series of hydrocarbon solvents--for example, pentane, hexane, and heptane-are realizrd.

I

Vol. 41, No. 2

in the listing of various fractions from different oils, that the fractions do not represent products which have been produced in a pilot' plant for a short period of time, say for an hour or two, but rather are fractions which have been withdrawn from a continuous pilot plant operation under constant control and opcration for a period of many hours or days. One can bo certain, (ts a result, that product st,reams are being measured which are in equilibrium. The data on the variouj cuts, in some cases, are sparse and some of the fractions are in the process of being analyzed and evaluated. I t will not, be possible, therefore, to say loo much about the quality of some of thesc fractions. It is hoped that it will be possible in the future t,o give a considerable amount of information on the quality and probable utilization of some of the fractions shown in the tables which follow. MENHADEN OIL

SOAPS

.T*S

0 L ,ElL

e5

Figure 2. General Flow with Neutralization

At the lowest point in the t m e i , an equilibrium is reached whereby certain constituents dissolve in propane, having for example, a density X. A little higher in the ton-er, the density of the propane is changed to some lower value, X-Y. The solubility relationships, as a result, also have changed to Such an extent that an additional bottoms phase drops out; this falls downward and recontacts a higher propane density phase. I t can be seen that in this way an effective internal reflux can be attained in the tower, as well as the advantage of the presence of a multiplicity of solvents.

Figure 3 shows the flow of a propane countercurrent extraction of menhaden oil in a three-tower system from which four cuts have been removed. The crude oil enters the middle of the first tower and the liquid propane enters the bottom. A so-called 2% color body fraction is removed from the bottom of this initial tower. Xext, 98Yc of the oil which is in propane solution is passed into the middle of the second tower where, by a readjustment of the operating conditions, it is found that 20% of the oil is eliminated as a bottoms fraction. The remaining 78(,Tc, in a fashion similar to that which occurred in the first tower, is pumped into the third tower, vhere a third set of conditions result in the elimination of the 68% bottoms fraction; after this a 10% vitamin A concentrate is isolated a? an overhead product.

NEUTRALIZATION

Khen neutralization is used (Figure 2) and it should be stressed that for the most part it is not employed, the operation is cairied out in the folloning manner: A small amount of propane is mixed with the crude oil, and caustic is added to this mixture. The resulting emulsion passes through mixing valves so that intimate contact between the oil, propane, and caustic is effected. After traveling through the mixing valves, the emulsion goes into the first tower shown on Figure 2; this is a so-called settling tower where the soaps settle to the bottom and are withdrawn in a water phase. The neutralized propane-oil phase is removed overhead and passes into the extraction tower where it undergoes contact with propane in much the same way as shown in Figure 1.

It has been learned that in this neutralization step, quantitative removal of the fatty acids can be accomplished with only negligible losses of oil to the soap phase. Stocks with 8 to 10Tc free fatty acids, for instance, have been neutralized, and by doing 60 in propane dilution, it has been possible to limit the loss of neutral oil in such cases to less than 0.2%. In like manner, the neutralization of high potency vitamin oils has been carried out effectively with extremely low losses of vitamins to the soap solution. Crude vitamin Oil? with potenciea of 30,000 units of vitamin A per gram and higher have been neutralized yith less than 0.2% loss of vitamins to the soaps. Results The remainder of the paper will be devoted to a discussion of some of the results obtained employing this process for the refining of various glyceride materials. These results were obtained in the first pilot plant built for this operation. since then operations have been improved. It should be remembered,

Figure 3.

Menhaden Oil (Table I)

Table I gives the re5ults of inspections obtained on the various fractions produced by the method illustrated in Figure 3. I t can be seen that the original color of the crude was about 11+ on the Gardner scale. The removal of the 27, fraction resulted in a cut on which no color reading could be obtained, since it was piactically jet black. The remaining 98% next was refraclionated in the second tower to vield a 20(,Tc high iodine value bottoms fraction. The most important specification on this fraction is its iodine value. The iodine value of the crude was 175, whereas the iodine value of the 2074 fraction has been increased to 225. In other words, the unsaturated constituents which are preaent in the oil are more insoluble than are the saturated ones. This can be noted in the color body fraction, as well as in the high iodine value fraction. One of the principles on which this separation i? based i i that


February 1949 Table I.

Menhaden Oil Fractionation Ia

Fraction Crude I Yield, wt. % ’ 2 Color, Gardner lirt: Black Color, Lovibond b ... . . Vitamin A potency unit 100 Unsaponifiable oil, % 1.2 0.9 Free f a t t y acids, % 1.3 0.5 SaDonification No. 193 190 Iodine No. 175 260 a See Figure 3. b Lovibond readings are on a 5.25-inch cell.

. .. .

I1 20 10

.. ., ..

I11 68 430Y-3.OR

0:4

0.8 0.4 189 225

0.3 194 165

IV 10 7

...

800 6.8 11.8 192 90

Table 11.

Menhaden Oil Fractionation IIa Crude

li+

50Y-7.6R 50 1.0 1.3 192 184

I 3.0 Black

I1 89 7 60Y-3.4R

0.6

0.5 0.5 193 187

. 0’.6 ,

260 lS7

in the overhead vitamin cut, and the vitamin potency has bcen increased tenfold. The iodine number of the vitamin fraction is but 105, as compared to 184 in the crude, indicating the concentration of saturated glycerides in the overhead. The unsaponifiable oil content followed the same trend as in the previous menhaden oil run, going from 1.0% in the crude to 6.1 % in the vitamin concentrate, SARDINE OIL

the more complex materials are less soluble. Thus, the unsaturated glycerides, being more complex and hence having more active groups present in the molecule, are rejected, in this case, to the bottoms or more insoluble phase. The next fraction, the 68% intermediate cut, definitely has a much lighter color, while its iodine value has dropped below that of the charge. The last fraction, 10% of the charge, which is the vitamin concentrate, has a number of interesting specifications. In addition to having a lighter color and a potency of 800 vitamin A units per gram compared to the charge potency of 100, the unsaponifiable oil content has increased from 1.2 to 6.8, while the iodine value has dropped from 175 to 90. Most of the free fatty acids which were present in the charge now have been concentrated in the overhead, so that the fatty acid values of the intermediate fractions are all below 0.5%. Preliminary tests have shown that the elimination of some of these unsaponir fiables results in 37 ssp COLOR BODIS r N T E R M E D / A I € the isolation of FRACT~DN better drying oil Figure 4. Menhaden Oil (Table 11) fractions. Figure - 4 depicts a similar processing of menhaden oil, except that no split has been made of the intermediate fraction between the vitamin concentrate and the color body fraction. In this second case, the crude menhaden oil was pumped into the first tower and 8 3% color body fraction removed from the bottom, while 97% of the menhaden oil, dissolved in propane, passed over into the second tower; from this an 8% vitamin concentrate was removed. Inspections on these three cuts are given in Table 11. Because a large middle fraction, for example, 89%, was taken, little variation in the iodine value occurred between the crude and the so-called paint oil fraction. As a result, the color is improved. Once again, the fatty acids have been concentrated

Fraction Yield, wt. % Color, Gardner Color, Lovibondb Vitamin A potency Unsaponifiab!e oil, % Free f a t t y acids, % Saponification No. Iodine No. a See Figure 4. b 5.25-inch cell.

283

I11 8 6 28Y-2.8R 500 6 .I 10.4 194 105

Much the same sort of separation as used in processing menhaden oil was carried out on sardine oil, as can be seen from Figure 5. Here, a three-tower system was employed from which four cuts were isolated: a color body fraction; a high iodine value fraction; an intermediate iodine value fraction; and a vitamin concentrate.

C O L O R BODIES

Figure 5.

ss7. r,v

HIGH

FRA c r/O N

47

7’

rN7EqMEOI4TE F m cn ON

IV

Sardine Oil (Table 111)

Table I11 gives the inspections on these various fractions. The iodine value on the crude was 185; the 35% high iodine fraction was raised to 240. The fatty acid values follow the same order as those obtained in the menhaden run, and once again the vitamin A potency, as well as the vitamin D potency, which is not shown, were greatly enhanced.

Table 111. Fraction Yield, wt. % Color, Gardner Vitamin A potency Free f a t t y acids, Saponification No. Iodine No. 0 See Figure 5.

Sardine Oil Fractionationa Crude

..11

350 1.0 192 185

I

I1

3.0 Black

35.0 8

111 47 0 4

0.5 184 250

i):4 188 240

0;3 192 160

IV 15.0 5 2 100 6.0 194 110

The color on this charge stock has decreased from an original 11 Gardner to a 4 to 5 value on fractions I11 and IV. In the case of sardine oil, even though a 35% high iodine value fraction was removed as compared to the 20% removed with menhaden oil, a higher iodine value was obtained. The iodine value of the crude sardine oil, however, was slightly higher than that of the menhaden oil. SOYBEAiU OIL

Figure 6 represents the propane fractionation of soybean oil. The system pictured results in the isolation of four fractions from soybean oil. The isolation of all these fractions, however, is not necessary for the straight refining of soybean oil, as will be discussed later. A 2% color body fraction (Figure 6) which


284

contained not only the color bodies but also all the break material present in the oil, was removed. The next fraction, 11,was a 25% high iodine value cut, and the third represented a 72% intermediate edible fraction. The fourth and last fraction was a 1% unsaponifiable free fatty acid concentrate rich in tocopherol.. and sterols.

I t appears that the removal of the 1% overhead fraction which is rich in sterolcl and tocopherols in no way harmed the stability of the edible oil fraction. This is somewhat surprising and probably can be explained on the basis that all the tocopherols and other inhibitors are not removed in this 1% cut. In other words, there may be an excess of tocopherols and other inhibitors over that nceded for stabilization of the oil, so that the removalof a portion of them has little effect on the resulting qtability of the reddual fraction. Figure 7 pictures a straight refining operation on soybean oil. Tn this case, the only steps involved are a single tower extraction of the crude oil to eliminate a 2% color body break material bottoms fraction, and deodorization of the 98% overhead cut to remove the remaining fatty acids, as well as to accomplish additional bleaching.

Table IV shows the inspections on these four fractions. The first sample, the fraction, despite being a bottoms cut, had a much lower iodine value than the chaige, and this was accounted for by the presence of the break material. The free fatty acid value of this cut increased, from 0.4% in the elude, to 5%. The fatty acids concentrated here represent those which are higher in molccular weight and more complex in structure and, as a result, those which would be more difficult to remove through any subsequent steam deodorization.

Table IV.

Soybean Oil Fractionation Is

Fraction Crude Yield, wt. Color Lovibondb 75-Y25R Iodin; No. 135 Free f a t t y acids % 0.4 Unsaponifiable Ail, % 0.9 Saponification N o . 192 a See Figure 6. b 5.25-inch cell.

X

I 2.0 100 5.0 2.5 190

I1 25.0 75Y-8R 155 0 02 0.3 192

111 72.0 25Y-2.5R 128 0.04 0.3 102

IV 1.0

ii5

20.0 60.0

80

The next fraction, 25Yc, had an iodine value of 155, as compared t o the original oil with its iodine value of 135. Without any treatment with caustic, the free fatty acid value dropped t o 0.02% from the original 0.4% present in the charge, and the unsaponifiable oil content decreased from 0.9 to 0.3%. Cut 111, the 72% edible oil sample, had an iodine value of 128, as well as a greatly improved color; the original color was 75Y-25R, whereas the edible fraction, before deodorization, had a color of 25Y-2.5R (5.25-inch cell). This latter color, on deodorization, dropped to less than 10Y-l.0R. As with the high iodine value fraction, tho free fatty acid value was much lower, 0.04 against 0.4 in the crude. The 1% overhead fraction was rich in unsaponifiables, as can be seen from its value of 60 against 0.9% in the feed, and the free fatty acids increased from 0.4 to 2OY0. In other words, by the removal of a 2% bottoms and a 1% overhead cut, a middle fraction was left from which the great bulk of the fatty acids, as v-ell as the unsaponifiables, had been removed. Stability tests on the edible oil fraction indicated that this oil is superior in so far as keeping qualities are concerned.

Vol. 41. No. 2

S7LT.F ,?€NNEO

Scr8,Fa.v O,L

r 2P COLOR EODi€3

Figure 7.

Soybean Oil (Table V)

Table V shows the inspections on the samples obtained from such an operation. Starting with a typical extractrd crude soybean oil, the removal of a 27, bottoms fraction resulted in a 98% overhead cut which had a Lovibond rcading of 35Y-3R (5.25-inch cell) before deodorization. This, in turn, on treatment with steam a t low pressures resulted in a final refined soybean oil yield of 97.570 with a color of IOY-1 OR. In this operation, starting with an original free fatty acid value of 0.8%, and without the use of any caustic, the free fatty acid value of the refined oil was lowered t o 0.04. As a result, by the simple removal of one fraction from crude oil in a single pass followed by deodorization, a completely refined oil was obtained. Evaluation tests on the stability of this oil indicated that it possessed excellent stability characteristics.

Table V. Soybean Oil Fractionation 11"

a

Fraction Yield, a t , % Color, Lo\-ibond Free fatty acids, % Iodine KO. Saponification No. Unsaponifiable oil, R See Figure 7.

Crude

I

I1

..

2.0 Black 5.0 100 190 2.6

35Y-3R 0.4 185

0.8 135 192

0.9

98,O

192 0.9

I11 97.5

10Y-1.OR 0.04 135 192

0.9

A number of comparisons were carried out, in the course of this work, between the quality of edible fractions obtained in soybean oil refining by the Solexol method us. conventional alkali refining, and it was concluded that it is most advantageous to completely eliminate the use of caustic in the refining of edible oils, such as soybean, cottonseed, corn, etc.

February 1949


285

LINSEED OIL

Figure 8 represents a refining operation which was conducted on raw linseed oil. In this case, the raw linseed oil was pumped to the center of the tower, the propane introduced a t the bottom, and a 1.5 color body ashcontaining fraction was removed. The 98.5% overhead fraction, after the elimination of propane and steam treatment, represented refined linseed oil. Table VI gives results of inspections of fractions I and I1 shown in the linseed oil diagram. The crude ail, which had an original Gardner color of 11,following removal of a 1.5% bottom fraction, rcsulted in the production of a 98.57. overhead cut with a Gardner color of 4. The iodine number had not changed. The ash content which was originally 0.1% was increased to 6.2% in Figure 8. Raw Linseed the bottoms and was not detectOil (Table VI) able in the overhead. The free fatty acid values shown (Table VI) are those of a product which wa3 not steam treated. This value can be dropped by steam treatment to a satisfactory level.

Table VI.

a

Linseed Oil Fractionation 1~

Fraction Yield wt. % Color: Gardner Iodine No. Ash content % SaponifioatiAn N O . Free fatty acids, % See Figure 8.

Crude

..

11 185 0.1 193 0.8

I 1.5 Black

I1 98.5

6.2 200 1.8

0.00 193 0.75

170

4

Table VII. Fraction

Linseed Oil Fractionation Ira Crude I I1 111

..

11 185 0.1 193 0.8 a

1.5 Black 170 6.2 200 1.8

48.5 6

205 0.00 193 0.1

50.0 1 165 0.00 193 1.4

See Figure 9.

The iodine value was increased from 185 in the crude to 205 in the 48.5% fraction, while it dropped to 165 in the 50% fraction. The ash content of both the drying oil fractions is 0. By this method of separation, the high iodine value fraction had a free fatty acid value of 0.1 as coinpared to the crude value of 0.8. The 50% overhead fraction had increased to 1.4. With any oils where the free fatty acid value gets so high that it does not appear feasible to remove the fatty acids by steam trmtment, it is possible to eliminate them effectively by the use of a preliminary caustic neutralization in propane solution. COD LIVER OIL

Figure 10 represents a processing scheme for the application of the Solexol process to the extraction of cod liver oil. In the case of vitamin oils, such as cod liver oil, caustic neutralization umally is employed, as was previously mentioned, because the primary concern is concentration of the vitamins present. It has been found in the studies on these vitamin oils that the vitamins present in the oil have solubilities similar to some of the free fatty acids appearing in the oil. As a result, if not removed prior to concentration, they evidently find their way into the vitamin concentrate. This is not completely objectionable, since it is possible to neutralize the concentrate with relatively low losses

185

Figure 9 is a diagrammatic sketch of an operation which was made to split raw linfieed oil into three fractions: the first was a color body ash fraction; the other two were low and high iodine value fractions from linseed oil. Table VI1 gives the inspections of these cuts. The color of the crude, 11, was reduced t o 6 in the so-called high iodine value fraction from linseed oil and to 1 in the low iodine value fraction

Figure 10. Cod Liver Oil (Table VIII)

/.e-? COLOR

flOOl&S

48 s?

H/GX

Z,v

FRacrioh.

Figure 9. Raw Linseed Oil (Table VII)

of vitamins. I t is, however, more feasible to neutralize the crude oil when the vitamin potency is lower. Therefore, as shown in Figure 2, the crude cod liver oil is contacted with caustic and propane; next it goes through a series of mixing valves and thence into a settling tower, where the soaps are removed essentially vitamin-free. The neutral oil then is passed into the extraction tower a t the mid-point, propane enters the bottom, and three cuts are isolated. These have been designated as: a 25% high iodine value fraction; a 70.5% intermediate iodine value fraction; and a 4.5% vitamin concentrate. Table VI11 gives the inspections on these fractions. The 25y0 cut had a vitamin potency of 150 as compared to the original crude oil of 2000 vitamin A units per gram. The free fatty acid


286

values are not discussed, because neutralization was employed and essentially all the fatty acids were removed. A slight excess of acids usuLtlly is maintained to ensure no entry of caustic into the extraction tower. The iodine value of the 25% cut WRS increased to 210 from the original crude value of 162. The unsaponifiable oil content dropped from 1.4 to 0.7%, and the color increased from 6+ to 9- on the Gardner scale. The second fraction, which was the bulk cut of this run, had inspections which approximated fairly closely those of the crude, except for vitamin content and color. Here, as in the 25% fraction, the vitamin potency dropped to 150, and the color showed a pronounced drop from 6f to 1- on the Gardnrr scale. Cut I11 increased in vitamin A potency from an original of 2000 to 41,000; the unsaponifiable content jumped from 1.4 t o 10.6%.

of processing. The iodine value which was 210 in the Z5yObottoms was 195 in the 50c;b bottoms, while the iodine value of the 70% cut dropped from 155 to 149 in the 45.5'3 fraction. It is possible that whereas some of the cod liver oil glycerides have not been t,oo successfully used in drying oil formulations in the past, fractions produced by this cxtract'ion mcthod will be of more interest. This situation might exist, since by removing appreciable quantitiej of the unsaponifiables present, in the oil, it is probable also that large percentages of so-called oxidation and polymerization inhibitors which occur in these oils have been removed. This may or may not result in the isolation of fractions which can find broader application in the drying oil field.

I n

i

Cod Liver Oil Fractionation Ia

Table VIII. Fraation Yield, wt. % Vitamin A potency Free fatty acids, $6 Iodine No. Saponification KO. Unsaponifiable oil, % Color, Gardner a See Figure 10.

I 25

Crude

2000 0.8

150 0.07 210 182 0.7 9-

162

186 1.4 6+

I1 70.5 150

0.04 155 188 1.0

Vol. 41, No. 2

I11 4.5 41,000 0.5 82 185

10.0

-

1-

The above fraction I11 does not represent by any means, the ultimate concentrate which can be obtained from cod liver oil by this fractionation. Concentrates from cod liver oil, having potencies close to 300,000 vitamin A units per gram can be obtained.

s7.

ssp

COLORB o a i ~ s Ras/w A w n F R A C r / dN

Figure 12. Tall Oil (Table X)

With regard to the cod liver oil vitamin concentrates, destearinization in propane solution also is part of the processing scheme. By carrying out this destearinixat,ion, the potency, of course, is increased corresponding t o the amount of stearine removed. It is advantageous to use a solvent such as propane which can be emploved in t,he extraction zone, as well as for the crystallization medium. In other words, it is possible to take the overhead from the top of the tower containing a vitamin oil concentrate, partially depropanize, and in so doing, chill the solution down sufficiently so that the stearine crystallizes out; after this it can be fihered. Filtration in propane solution results in the isolation of a clean stearine cake with negligible oil lasses. The same recovery system for the propane for recycle purposcs can be used for both systems.

I1 .5G HIGH

7

&?si:

IV-

.TNTE~M~D 17, ,AT€

FRA cTI ON

FR*CT,OA,

T A L L OIL

Figure 11. Cod Liver Oil (Table IX)

Figure 11 s h o w a sllghtly different breakdown of cod liver 011. Once again neutralization was employed, and the same vitamin concentrate was obtained. The intermediate fractionq, however, instead of being broken into a 25 t o 70 split, were a 50 to 45 split. Table I X follows the changes which occur by this variation

Table IX. Fraction Yield,.wt. % Vitamin A potenc Free fatty acids, Iodine No. Saponification No. Unsaponifiable oil, % Color, Gardner a See Figure 11.

%

Cod Liver Oil Fractionation IIa Crude 26bO

0.8 162 186 1.4 6 f

I 50 150

0.1

195 184

0.7 7 f

I1 45.5

150 0.01 149 188 1.1 1

I11 4.5 41,000 0.2 76 189 10.6

-

The last oil which will be discussed in this paper is tall oil. Although relatively little work was done on this oil, and it is still in its preliminary stages, it might be of interest, to present t,hose results which we have obtained thus far. Figure 12 s h o m one method of processing tall oil which was used. Tall oil mas passed into the center of the tower and propane in t,he bottom, and decolorized by the removal of a 5% color body fraction. The 957, overhead next mas split into two fractions, a 357, rosin acid fraction and a 60% fatt'y acid-rosin acid cut,. I n t,his extraction, an attempt was made to obtain a fract,ion relatively rich in rosin acids and low in fatty acids. Vi7ith a more efficient tover, both split,s probably could b o made simultaneously-that is, a split in which hut two fractioiis are obtained, one high in rosin acids, the ot,her high in fatty acids. Table X shows t,he analytical results obtained on thc friivtions shown in Figure 12. The fatty acid value of the charge way 4570 and the rosin acid value was 497,. The 357, cut, in which an attempt was made to concentrate the rosin acids, resulted

INDUSTRIAL AND E N G I N E E R I N G C H E M I S T R Y

February 1949

~

~

Table X. Fraction

Tall Oil Fractionation I" Charge

Yield, wt. % Color Gardner Fatty(acids, 4 Rosin acids Saponificati'on No. Acid No. See Figure 12.

d

49 175 162

Table XI. Fraction Yield, wt. % Color Gardner F a t t i acids, Rosin acids, lo Saponification No. Acid No. See Figure 13.

r

I 5.0

Black 40

55 145 110

I1 35.0 14 20

I11 60.0 8

1E 146

172

60 33 177

Tall Oil Fractionation IIa Charge

18% 45 49 176

8

e v 70 ? COLOR BODIES j?oslr A = , ~ -

287

~~

162

I 5.0

Black

40 55 145 110

I1 70.0 11 30 63 176 162

111

25.0 7 87 6 178 176

Acto FRacrioN

F A T w

Figure 13. Tall Oil (Table XI)

In a rosin acid fraction of 73%, while the fatty acid content dropped to 20%. The saponification number followed this change by dropping from 175 to 165. Figure 13 shows a similar tall oil fractionation where an attempt was made to isolate a fatty acid-rich fraction. In this case, a 25% cut was removed as an overhead product, after the removal of a 5 % color body fraction, and a 70% rosin acid-fatty acid fraction. Analytical results on these fractions are shown ln Table XI. The fatty acid value in fraction I11 increased to 87%, while the rosin acid content dropped t o 6%. Additional studies on tall oil are being carried out in attempts to improve the decolorization of the oil, as well as the fatty acid-rosin acid separation. Many of the results obtained and pictured in this paper were the initial runs made on oils, and more extensive studies have been and are being carried out on the various oils. It appears from

the work which has been conducted thus far that the application of the Solexol process in the glyceride oil field should bring about some striking changes in the refining of various fats and oils, and its commercial acceptance is already definitely established. Bibliography (1) Drew, D. A., and Hixson, A. N., Trans.Ant. Znst. Chem. Engra., 40, 675 (1944). (2) Hixson, A. W., and Bockelmann, J. B., Ibid., 38,891 (1942). (3) Hixson, A. W., and Hixson, A. N., Ibid., 37,927 (1941). (4) Hixson, A. W., and Miller, R., U. S. Patent 2,219,652 (1940). (5) Ibid., 2,226,129 (1940). (6) Ibid., 2,247,496 (1041). (7) Ibid., 2,344,089 (1944). (8) Ib$d., 2,388,412 (1945). (9) Larner, H. B., U. S. Patent 2,432,021 (1947). (10) Schaafsma, A., Ibid., 2,118,454 (1938). (11) Van Orden, L., Ibid., 2,394,968 (1946). RBCIIYED February 26, 1948.

Synthetic Drying Oils Don S. Bolley National Lead Company, Brooklyn I , N . Y. 'The drying oil chemist has become accustomed to consider synthetic drying oils as oils prepared through chemical treatment of fatty oils. A n extensive and critical literature review of drying oils of this nature was made. These included dehydrated castor, methods of increasing un*aturation, maleic oils, drying oil esters of polyhydric alcohols, nonfatty drying oils, and copolymerized drying ails. Experimental data are given on the comparative properties of linseed pentaerythritol ester with linseed ail and soybean pentaery thritol ester with soybean oil.

T

materials is given in Table I. Drying oil, as used in this discussion, means an oil-like material which dries by oxidation when exposed in a thin film to the air. This might be considered a restricted definition; the more general definition is: an oil-like material which dries when exposed in a thin film. The general term would include oxidizing resinous solutions dissolved in thinner which dry by solvent evaporation. A raw drying oil is one obtained from the seeds or nuts directly by hydraulic pressing, expelling, or solvent extraction. I t has had no additional treatment except possibly a storage period to allow suspended material to settle out. The soybean and edible

HE term, synthetic drying oils, as used by the paint and

varnish chemist, as well as the drying oil chemist, might be misleading t o those outside of the field. Synthetic drying oil usually means an oil which has been prepared through chemical treatment of fatty oils. Less frequently, i t may refer t o drying materials of an oily nature which have been made from nonfatty materials. Since the drying oil chemist uses a variety of special terms in reference to oils, a suggested classification of various drying oil

Table I. Drying Oil Materials Raw drying oils Refined drying oils Modified drying oils Synthetic f a t t y drying oils Synthetic nonfatty drying oils Copolymerized drying oils Drying varnishes Drying oil resins

YING IL

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