US3531506A - Color stabilization of fatty-acid forerunnings - Google Patents

Description

United States Patent "ice 3,531,506 COLOR STABILIZATION OF FATTY-ACID FORERUNNINGS Sasauka Sekhar Naskar, Witten (Ruhr), Hans Leo Hiilsmann, Wengern, and Gustav Renckhotf, Witteu (Ruhr), Germany, assignors to Dynamit Nobel Aktiengesellschaft, Witten (Ruhr), Germany N0 Drawing. Filed June 25, 1969, Ser. No. 836,624 Claims priority, application Gzrmany, June 26, 1968,

Int. cl. Cllc 1/10 US. Cl. 260419 11 Claims ABSTRACT OF THE DISCLOSURE Discoloration and subsequent darkening of fatty-acid forerunnings are prevented by heating the fatty acids with at least one alkyl ester of silicic acid, polysilicic acid and/or carbonic acid at a temperature of approximately 180-250 C., and then distilling the resultant mixture to recover the fatty acids. The heating step is carried out for about 0.5-8 hours.

BACKGROUND OF THE INVENTION The state of the art can be seen from a consideration of US. Pat. 2,862,943 and from German DAS 1,214,212. Inorganic and organic compounds have been conventionally employed in the art for preventing discoloration. However, as discussed in said German publication, these conventional processes have many disadvantages. When using the organic and inorganic compounds of boric acid, unsaponifiable condensation products of the fatty acids are obtained in the distillation residue. In fact, the production of exactly these condensation products from fatty acids is described in DAS 1,073,665, wherein oxygencontaining boron compounds are employed as condensation catalysts. The yield of unsaponifiable condensation products, in accordance with this process, is up to 92%. US. Pat. 2,583,028 and British Pat. 1,081,522 describe the treatment of fatty acids with boron trifiuoride or with the ether complex thereof. However, extremely grave corrosion problems are encountered in these processes.

One of the objects of the present invention is to provide a process for preventing the discoloration and subsequent darkening of fatty-acid forerunnings.

Another object of the present invention is to provide a novel process for purifying fatty acids and for preventing the formation of unsaponifiable compounds therein which overcomes the disadvantages and deficiencies of the prior art methods.

A further object of the invention is to provide fatty acids of improved color, even when using low grade substances as starting materials.

These and other objects and advantages of the present invention will become apparent to those skilled in the art from a consideration of the following specification and claims.

SUMMARY OF THE INVENTION In accordance with the present invention, it has been 3,531,506 Patented Sept. 29, 1970 found that the discoloration and subsequent darkening of the first-or forerunnings of fatty acids having 8-12 carbon atoms can be prevented by heating the fatty acids with about 0.2-2% by weight, preferably 0.5-1% by weight, based on the amount of fatty acid employed, of an alkyl ester of silicic acid, polysilicic acid, carbonic acid or mixtures thereof. Heating is conducted for approximately 0.5-8 hours, preferably 2-4 hours, to temperatures of about ISO-250 0., preferably to ZOO-240 C., under normal pressure. Slight superatmospheric pressures of up to about 5 atmospheres gauge can be optionally used when a low-boiling alkyl ester of silicic acid and/or carbonic acid is employed. Thereafter, the fatty acids are distilled.

The fatty-acid forerunnings treated in accordance with the present invention are obtained as the first runnings or heads during the distillation of fatty acids from the hydrolysis of coconut oil or palm nut oil. The neutralization of the free fatty acids in crude coconut oil and palm nut oil with alkali results in the formation of soap. The separated soap solution is known as soap stock, which contains some neutral oil. It is hydrolyzed or split by acidulation with mineral acids which causes a separation of the fatty acids along with the neutral oil. This mixture of fatty matters is known as acid oil. This acid oil is hydrolyzed, and the fatty acids obtained by distillation have an inferior color quality as compared with fatty acids obtained by the direct hydrolysis of coconut or palm nut oil. Also, a distinction should be made between the fatty acids from hydrolyzed acid oil obtained by splitting of soap stock during the refining of coconut oil or palm nut oil, and fatty acids from the pressure-hydrolysis of coconut oil or palm nut oil. The fatty acids from hydrolyzed acid oil obtained by splitting of soap stock exhibit a poorer color quality than the fatty acids obtained by direct hydrolysis of coconut oil or palm nut oil and tend to exhibit discoloration and subsequent darkening to an even greater extent than the latter. The process of the present invention, however, makes it possible to also produce color-stable distillates from the fatty acids from hydrolyzed acid oil obtained by splitting of soap stock during the refining of coconut oil and palm nut oil.

In Examples 1 to 4, set out below, fatty-acid forerunnings of a relatively low quality were employed, stemming from fatty acids'from hydrolyzed acid oil. A comparison with Examples 5 and 6 makes it clear that the color stability of fatty-acid forerunnings obtained from the hydrolysis of coconut oil or palm nut oil under pressure is considerably higher.

The color stability of the fatty-acid forerunnings treated in accordance with the invention as well as that of the untreated materials was determined by heating the samples in a small glass tube having a diameter of 14 millimeters and a filling height of 115 millimeters to 200 C. during a period of 6 hours. This heating test was conducted in a thermostatically controlled oven which was not opened during the entire duration of the test. The test tubes were each covered with a cap.

The color intensity was measured in iodine color number units, wherein the iodine color number indicates how many milligrams of free iodine are contained in milliliters of aqueous iodine-potassium iodide solution at the same depth of color, when measured at a layer thickness of 25 millimeters.

The process according to the present invention can be conducted batch-wise as well as continuously.

The following examples are given merely as illustrative of the present invention and are not to be considered as limiting. Unless otherwise noted, the percentages therein and throughout the application are by weight.

3 EXAMPLES THE INVENTION Example 1 The untreated fatty-acid forerunnings employed had the following composition, according to gas chromatographic analysis (numerical data in percent by weight): C -acid: 0.2; C -acid: 68.4; C -acid: 23.5; C -acid: 7; C -acid: 0.5; C -acid: 0.2; methyl heptyl ketone: 0.2 and methyl nonyl ketone: 0.2.

2,400 parts by weight of the above described fatty-acid forerunnings, containing approximately 2% of water, were dehydrated with agitation and mixed, at a sump temperature of 240 C., with 0.5% by weight of silicic acid tetrabutyl ester or the dibutyl ester of carbonic acid. The treatment time was 3 hours. During this time, a temperature of 240 C. was maintained. Thereafter, the sump temperature was lowered to 100 C. by cooling, and the contents of the flask distilled over a small distillation column under a vacuum of 3-5 torr [mm. Hg] within about 2 hours, 3 fractions being withdrawn, For comparison purposes, 2,400 parts by weight of untreated fattyacid forerunnings were distilled under the same conditions (Example 1a).

As fraction 1, 55-10% by weight was obtained; as fraction 2, 76-78% by weight; as fraction 3, 57% by weight, based on the initial charge of anhydrous fatty-acid forerunnings. The amount of residue was 79% by weight.

The values are compiled in Table I.

Example 2 The procedure of Example 1 was repeated with the exception of the treatment time, amounting to 8 hours, all of the other conditions being identical to those set forth in Example 1. Table I shows the measured values which were obtained.

Example 3 2,400 parts by weight of the above fatty-acid forerunnings were dehydrated, and 1% by weight of the ethyl 4 ester of polysilicic acid was added thereto at2007 C LThe charge was maintained at 200 C. for 6 hours and then distilled under a vacuum. Three fractions were obtained. The data resulting from this experiment are listed in Table II.

Example 4 Five tons of the above fatty-acid forerunnings were dehydrated at 450 torr. At 220 C., 0.7% by weight of the tetrabutyl ester of silicic acid was added, and the temperature of the charge was maintained at 220-240" C. for 3 hours. Thereupon, the charge was cooled to C. and fractionally distilled in a continuous distillation plant under a vacuum of 5 torr. The characteristic data of the thus-obtained three fractions are set forth in Table II.

Example 5 (a) 2,400 parts by weight of fatty-weight forerunnings from the hydrolysis of coconut oil were dehydrated, and 0.5 by weight of the ethyl ester of polysilicic acid was added thereto at 240 C. The charge was maintained at 240 C. for 3 hours and thereafter distilled under a vacuum. The characteristic data of the three fractions and the residue can be seen from Table III.

(b) For comparison purposes, 2,400 parts by weight of untreated fatty acids from a coconut oil hydrolysis were distilled under the same conditions as set forth in (a), in three fractions, the resulting data also being shown in Table III.

Example 6 2,400 parts by weight of fatty-acid forerunnings derived from the hydrolysis of coconut oil and palm nut oil were dehydrated and then mixed with 0.8% by weight of the ethylbutyl ester of carbonic acid at C. Within 6 hours, the temperature was increased to 240 C., and the charge was subsequently distilled under a vacuum. The characteristic values of the three fractions and the residue are indicated in Table III.

TABLE I Fraction I C llodiIne 0 or 0. Duration of Amount after 6 4 treatment; (percent Iodine hours at Example Additive (hours) by wt.) Acid No. color N 0. 200 C.

1(a) Without additive 0 8. 8 380 5. 2 104 1(b). 0.5% by weight of the tetrabutyl ester of oi'tho- 3 9. 0 378 1. 0 38 si icic aci 1(c). 0.5%dby weight of the dibutyl ester of carbonic 3 9. 8 377 1. 5 48 am 2(a) 0.5% by weight of the teti-abutyl ester of ortlio- 8 8. 6 381 1 33 silicic acid. 2(1)) 0.5%oy weight of the dibutyl ester of carbonic 8 8. 1 379 1. 3 42 Fraction II Fraction III Residue C 1Iorilne Iodinc 0 or 0. Color No. Content of Amount Iodine after 6 Amount Iodine after 6 Amount unsaponifiable (percent Acid Color hours at (percent Acid Color hours at (percent compounds Example by Wt.) No. No 200 C. by wt.) No. No 200 C. by wt.) (percent by wt.)

TABLE II Content of Iodine unsapon- Color N 0.. ifiable com- Amount Iodine after 6 pounds (percent Color hours at (percent Fraction by wt.) Acid No. No 200 C by w Example 3 1 7.8 381 1 18.0 0.8 2 79. 5 375 1 6.2 0. 6 5. 5 312 2. 2 15. 3 1. 0 7. 2 252 3. 6 Example 4 1 6 384 1. 2 53 0.9 2 78 376 1 7. 8 0. 6 12 320 2. 1 18. 2 0. 5 Residue 4 6. 6

TABLE III Content of Iodine unsapon- Color No. ifiable com- Amount Iodine after 6 pounds (percent Color hours at (percent Fraction by wt.) Acid No. No 200 C. by wt.)

Example (a). l 5. 2 360 1 12 0. 6 2. 83. 2 353 1 4. 2 0.3 6. 4 256 1. 2 l4 0. 4 R 5. 2 242 1. 5 Example 5(b) 5.0 359 2. 2 60 0.6 83. 4 352 1.8 35 0. 3 6. 8 254 l 0 0. 4 4. 8 241 l. 6 Example 6 1. 5. 3 340 1 15 0. 7 2. 83. 0 335 l 3.8 0. 2 3. 6. 6 242 1. 3 l3 0. 2 Residue 5. 1 230 1. 8

The alkyl esters shown in the examples are merely exemplary of the additives which may be employed in accordance with the invention. Generally, the alkyl groups in said alkyl esters have from 1 to 4 carbon atoms (usually designated as lower alkyl) and include groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl and tert-butyl.

The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included herein.

We claim:

1. A process for preventing the discoloration and subsequent darkening of fatty-acid forerunnings having from 8 to 12 carbon atoms which comprises heating the fatty acids with at least one alkyl ester of an acid selected from the group consisting of silicic acid, polysilicic acid and carbonic acid at a temperature of approximately 180- 250 C., and then distilling the resultant mixture to recover the fatty acids.

2. The process of claim 1, wherein 0.22% by weight of said alkyl ester of silicic acid, polysilicic acid or carbonic acid or a mixture thereof is added to said fatty-acid forerunnings.

3. The process of claim 1, wherein the alkyl ester additive is heated with said fatty-acid forerunnings for about 0.5-8 hours.

4. The process of claim 1, wherein a low-boiling alkyl ester of silicic acid or carbonic acid or a mixture thereof is heated with said fatty-acid forerunnings under a slight superatmospheric pressure of up to about 5 atmospheres gauge.

5. A process for preventing the discoloration and subsequent darkening of fatty-acid forerunnings having from 8 to 12 carbon atoms which comprises heating the fatty acids with about 0.2-2% by weight of an alkyl ester of silicic acid, polysilicic acid or carbonic acid or a mixture thereof for approximately 0.5-8 hours at a temperature of about -250 0., and then distilling the resultant mixture to recover the fatty acids.

6. The process of claim 5, wherein 0.51% by weight of said alkyl ester is added to said fatty-acid forerunnings.

7. The process of claim 5, wherein heating is carried out for 2-4 hours.

8. The process of claim 5, wherein the mixture of fattyacid forerunnings and alkyl ester is heated at 200240 C.

9. The process of claim 5, wherein a low-boiling alkyl ester of silicic acid or carbonic acid or a mixture thereof is heated with said fatty-acid forerunnings under a slight superatmospheric pressure of up to about 5 atmospheres gauge.

10. The process of claim 5, wherein said process is conducted continuously.

11. The process of claim 5, wherein the alkyl groups in said alkyl ester have from 1 to 4 carbon atoms.

References Cited UNITED STATES PATENTS 3,052,701 9/1962 Hampton 2604l9 LEWIS GOTTS, Primary Examiner E. G. LOVE, Assistant Examiner