US2563327A - Miscella refining - Google Patents

Description

Patented Aug. 7, 1951 MISCELLA REFINING Robert G. Folzenlogen,

Hamilton County, Ohio, assignor, by mesne assignments, to The Buckeye Cotton Oil Company, Memphis, Tenn, a corporation of Ohio No Drawing. Application June 27, 1949, Serial No. 101,683

12 Claims. i

This invention relates to the refining of solvent extracted vegetable oils, and more particularly to the refining of such oils in the presence of the extraction solvent.

One of the disadvantages which has deterred wider adoption of refining processes involving the addition of an aqueous alkaline refining agent to the solvent solution of extracted oil for the purpose of neutralizing the oil and of reducing color is the rather low emciency of color removal. Usually the recovered oil from such refining is subjected to a second refining in order that its color may be suificiently light to meet current standards for edible use, as in shortening for example.

It is therefore an object of the present invention to provide an improved process of refining solvent extracted vegetable oils in the presence of the extraction solvent, whereby color removal from the oil is markedly improved.

A further object is to provide a process for the alkali refining of solvent extracted vegetable oils in the presence of the extraction solvent, in which process color removal from the oil is efiiciently effected in a shorter time and with the use of less alkali.

Other objects and advantages will appear in the following description of the various embodiments of the invention.

It has been observed in the course of my association with the refining of oil-solvent solutions (sometimes referred to in the art as miscellas) that color removal may be improved by continued agitation of the miscella with the refining lye over a long period or by the use of an increased quantity of the refining lye. However, either of these expedients is conducive to excessive oil saponification and an attendant increase in oil loss.

I have found that agitation of the refining lye and miscella in the presence of certain non-ionic ethers markedly improves color removal and permits reduction both in the agitating time and in the amount of refining lye hitherto necessary for desired color reduction. The reason for the effectiveness of the non-ionic ether is not understood but I am of the opinion that the action is not due solely to emulsification efiecting more intimate-contact. In support of this position I point t my observations that some of the ethers employed are not recognized as emulsifying agents and that other materials which are well known in the art as emulsifying agents, such as soaps, monoglycerides, alkyl sulfates, alkyl benzene sul- Columbia Township,

2 fonates and other sulfates and sulfonates having emulsifying action, have substantially no power to improve color removal during refining.

In accordance with my invention, the lye is intimately mixed with the miscella in the presence of at least one non-ionic ether compound, liquid at about F., and of the group consisting of (1) ethers of polyhydric alcohols, said alcohols containing from two to three hydroxyl groups and having from two to eight carbon atoms in the carbon skeleton, and (2) non-ionic derivatives of such of said ethers as contain unreacted hydroxyl groups.

It is to be understood that although ethers used in the practice of my invention are identified as ethers of polyhyclric alcohols, such ethers may be iormed from compounds other than polyhydric alcohols, such as polyhydric alcohol anhydrides for example.

Various types of non-ionic ether compounds may be employed in the practice of the invention as will be apparent from the list of compounds given below. It will be noted, moreover, that with respect to derivatives of those ether compounds which contain unreacted hydroxyl groups, such derivatives may be formed, for example, by reaction of the hydroxyl group with carboxylic acids, compounds containing an unreacted alcoholic'hydroxyl group, phenols, amines and mercaptans. Thus, for example, tetraethylene glycol or the monoethyl ether of ethylene glycol per se may be used, or those non-ionic derivatives which are liquid at about 80 F. and which may be formed by reaction of other compounds with the unreacted hydroxyl groups of the glycol may be employed. With respect to such derivatives, it is important to observe that the success of the in vention does not depend on the type of derivative employed provided that it is liquid at about 80 R, that it is non-ionic, and that it contains the ether groups intact. Having such chemical and physical properties the derivative (or the original ether) can be used in the practice of my invention and an improvement in the ease of color removal during miscella refining will be observed.

As will be noted from the following detailed description, the essential distinguishing features of the refining procedure of my invention over those hitherto employed are in the use of the ether compound and in the attendant permissible reduction in lye usage and agitating time.

amass? The miscella coming from the extraction step usually contains more solvent than oil, but my refining procedure does not require large quantities of solvent and it may be desirable from the standpoint of economy in handling, storage, etc, to remove a portion of the solvent before performing the refining operation. Such reductions in the amount of solvent may be achieved by the usual evaporation facilities known in the art. I prefer to carry out the refining procedure on miscellas containing from about 25 per cent to about 50 per cent oil.

I have found also that it is preferable to refine the miscella with reasonable promptness after recovery from the extraction procedure. Under the same conditions of operation it will be found that color reduction in the case of fresh miscella will be somewhat greater than that obtained in the refining of aged miscella. Thus an advantage will be gained by arranging to refine the miscelia promptly as it is delivered from the extraction unit or from the miscella concentration.

In such practices involving refining substantially immediately after extraction or miscella concentration, the temperature of the miscella may be well above 100 F. as it is charged to the refining equipment. Cooling the miscella before addition of the refining lye is unnecessary. The temperature at which the refining agent is mixed with the miscella in the presence of the nonionic ether compounds is therefore not a limitation. Ordinarily the temperature will range from about 80 F. to just below the boiling point of the miscella. According to my experience, however, good color reduction in minimum time is effected at temperatures between 130 to 140 F,, preferably at about 135 F. when the. miscella is constituted of about 40 to 50 per cent oil in commercial hexane. Such temperatures of course will also vary depending on the solvent used in the extraction, lower boiling solvents of course requiring lower temperatures if the refining is conducted at atmospheric pressure.

The advantages of my invention are realized when the miscella is constituted of extraction solvents other than hexane. Thus improved results in color reduction are also noted in the case of miscellas formed by the use of extraction solvents such as benzene, heptane. commercial mixtures containing such hydrocarbons, and other aliphatic and aromatic hydrocarbon extraction solvents and solvent mixtures known in the art. The invention is of particular advantage, of course, in the refining of those miscellas formed in the use of solvents which dissolve a considerable quantity of highly colored constituents from the oil-bearing meats.

The concentration of the refining lye will vary, depending on the proportion and kind of minor constituents contained in the oil and dissolved in the miscella. Higher concentrations are preferably used when the concentration of free fatty acid and color constituents is high. However, the necessary adjustments to compensate for such variations in miscella constitution are known to those versed in the art and have no influence on the advantages of using the nonionic ethers in accordance with my invention. By way of illustration, however, I have found that aqueous solutions containing from about 5 per cent to about 20 per cent sodium hydroxide may be used, final choice depending on the refiners judgment.

As indicated generally above, practice of the instant invention makes possible a considerable saving in lye usage. For example, before my discovery of the advantageous action of non-ionic ethers in reducing color, it was necessary to use 200 to 225 per cent of the maximum per cent sodium hydroxide prescribed by the rules of the National Cottonseed Products Association in the regular refinin of hydraulic cottonseed oils of the same free fatty acid content as oleic acid (per cent NaOH=per cent F. F. A./5.2+.54). Even with such large caustic usages, agitation times of 70 to minutes were required to obtain desired color removal. Use of the present invention not only permits an appreciable reduction in the time of agitation required to effect color removal, but also permits reduction in the caustic usage to 100-175 per cent of the maximum prescription above referred to for hydraulic oils of comparable free fatty acid content. Under normal conditions and with normal hexane miscellas, obtained in the extraction of cottonseed oil for example, 125-150 per cent of maximum will suffice. Both of these permissible reductions are conducive to lower refining loss. as thou versed in the art well know.

The following examples will illustrate 'the manner in which my invention may be practiced, but it is to be understood that the procedures therein described are merely illustrative and are not intended to be limiting.

Example 1.-By titration with N/10 sodium hydroxide solution, the apparent free fatty acid (as oleic acid) content of a concentrated cottonseed oil miscella containing about 40% oil and about 60% hexane was determined as 2.6%. From this determination 125% of maximum per cent sodium hydroxide prescribed by the rules of the National Cottonseed Products Association for hydraulic pressed cottonseed oil of comparable free fatty acid content was calculated as 33%, or 10.8% of 12% sodium hydroxide solu- 189.5 .parts by weight of the miscella were chosen for the refining procedure of my invention. This quantity of miscella required 20.5 part by weight of 12% sodium hydroxide solution on the basis of the foregoing calculation.

To the miscella at 130 1". were added .13 part by weight of polypropylene glycol of about 400 molecular weight. This amount of glycol was about 0.625% of the weight of the lye calculated for use in the refining step. The mixture was agitated and 20.5 parts by weight of 12% sodium hydroxide solution were added. The mixture was agitated 15 minutes, the temperature being maintained at 130 F. The mixture was then allowed to settle, the refined miscella being decanted from the precipitated foots and subsequently filtered. The Lovibond color of a 5% inch column of this refinedmiscella was 35 yellow, 3.5 red. The same miscella refined under comparable conditions without the addition of the polypropylene rlycol was too dark to read on the Lovibond scale.

In the further testing of the invention substantially in accordance with Example 1, refinings of cottonseed oil miscella at F. with 15 minutes agitation, of the maximum percentage of 12% sodium hydroxide being used, gave the following specific color results when the indicated amounts of non-ionic ethers were used. It should be noted here that in all cases comparable refinings without the use of the non-ionic ether resulted in refined miseellas which were Per Cent Color-of Refined bigger Miscella on Non Ionic Ether caustic Soda Yellow Red Soln Monothioether of dodecyl merca tan and polyethylene glycol contai lng about 10 ethylene grou s 0.6 30 2. 2 Monoether of tall oil an polyethylene 1 glycol containing about 10 ethylene groups 0. 6 30 2. 3 Monoether of polyethylene glycol and sorbitan monooleate (a commercial product sometimes referred to as Tween 81) 0. 6 25 0. 9 Monoether of polyethylene glycol and sorbitan monooleate (a commercial product sometimes referred -to as Tween 81) 0. 22 20 1.8 Monoether of polyethylene glycol and sorbitan monooleate (a commercial product sometimes referred to as Tween 81) 0. 11 30 4. 9 Monoether of polyethylene glycol and sorbitan monooleete (a commercial product sometimes referred to as Tween 81) 0.05 30 8.8 Monoether of octylphenol and polyethylene glycol containing about 10 ethylene groups l. 2 60 M Monoester of octaethylene glycol and the fatty acids of cottonseed oil hydro genated to about 70 I. V 0. 6 20 1.3 Monoether of dodecyl phenol and hexadecaethylene glycol 0. 6 30 2.8 Dipropylcne glycol 0.625 35 3. 2 Reaction product of one mol monoethanolamine and six mols of ethylene oxide 0. 625 35 3. Reaction product of one mol of a mixture of amines derived from coconut oil and six mols of ethylene oxide 0. 5 20 2. 1

Example 2.-To 250 cc. of soybean oil miscella (at about 80 F.) containing about 40% oil were added .11 gram of polypropylene glycol having a molecular weight of about 400. To th stirred mixture were then added 18 grams of 12% aqueous sodium hydroxide solution. The mixture was agitated for 15 minutes, the temperature being maintained at about 80 F.

In this example the amount of sodium hydroxide used was 150% of the N. C. P. A. maximum and the amount of polypropylene glycol was 0.625% of the weight of the lye. Y

The refined miscella had a color of 30 yellow, 5.0 red, whereas the same miscella refined in a comparable way without the use of the polypropylene glycol had a color of 70 yellow, 11.5 red.

Example 3.-The ether formed by the condensation of octylene glycol with about 7 mols of ethylene oxide was used in this example.

To 250 cc. of cottonseed oil miscella (at about 80 F.) containing about 40% oil were added .23 gram of the ether. To the stirred mixture were then added 11.3 grams of 12% aqueous sodium hydroxide solution. Th mixture was agitated at about 80 F. for 5 minutes.

In this example the amount of sodium hydroxide used was 125% of the N. C. P. A. maximum and the amount of non-ionic ether was 2.0% of the weight of the lye.

The refined miscella had a color of 35 yellow, 4.9 red, whereas the same miscella refined in a comparable way without the use of the ether had a color of '70 yellow, 30 red.

Example 4.The conditions of refining the miscella of Example 3 were repeated employing the ether resulting from the condensation of 2-methyl pentanediol-2,4 with about '7 mols of ethylene oxide. The refined miscella had a color of 35 yellow, 4.8 red.

As an auxiliary example, one can obtain the benefits of the present invention by use of a mixture of the ether used in Example 4 with polypropylene glycol having a molecular weight of about 400. a

As will be noted from the above examples, marked improvement in color is obtained when the amount of non-ionic ether employed is as low as 0.05 per cent based on the weight of the ,lye. However. even smaller amounts such as 0.02 per cent (based on the lye) or some oi. the more active ethers efiect noticeable improvement in color. Obviously all ethers covered in the present application are not equally effective in their efilciency to promote removal of color and mixtures may be employed if desired. Amounts of some compounds such as the monobutyl ether of ethylene glycol and the diethyl ether of diethylene glycol, which are necessary to achieve desired color in the refined miscella, may exceed 6 percent of the weight of the lye and even greater proportions, such as 10 per cent, may be necessary in some instances.

Instead of adding the non-ionic ether to the mlscella prior to addition of the lye as shown in the above examples, the addition may be made separately but simultaneously with the lye, or shortly after the lye has been added, or in admixture with the lye, the essential requirement being that the non-ionic ether be present substantially throughout the period in which the lye and miscella are mixed.

Refined miscellas with markedly improved color were also obtained by agitating miscella with caustic soda solution in the presence of the following non-ionic ethers not heretofore specifically mentioned.

Hexaethylene glycol Nonaethylene glycol Dodecethylene glycol Lauric acid monoester of diethylene glycol Acetic acid diester of diethylene glycol Laurie acid diester of tetraethylene glycol Laurie acid diester of nonaethylene glycol.

Stearic acid monoester of octaethylene glycol Monoester of octaethylene glycol and coconut oil fatty acids Diethyl ether of ethylene glycol Monobutyl ether of ethylene glycol Dibutyl ether of ethylene glycol Monobenzyl ether of ethylene glycol Monoethyl ether of diethylene glycol Diethyl ether of diethylene glycol Monobutyl ether of diethylene glycol Dimethyl ether of diethylene glycol Dimethyl ether of tetraethylene glycol Dibutyl ether of tetraethylene glycol Dilauryl ether of tetraethylene glycol Monoether of dodecyl phenol and heptaethylene glycol Monomethyl ether of octaethylene glycol Monoethyl ether of octaethylene glycol Monoether of octaethylene glycol and cholesterol Monoether of dodecyl phenol and decaethylene glycol Monomethyl ether of dodecaethylene glycol Monoether of dodecaethylene glycol and cholesterol Monomethyl ether of hexadecaethylene glycol Reaction product of one mol ethylene dlamine and six mols of ethylene oxide Monoester of the fatty acids of cottonseed oil hydrogenated to about 70 I. V.-and the polyglycol obtained by the condensation of one mol of monoethyl ether of diethylene glycol with two mols of ethylene oxide 7 Monoester of the fatty acids of cottonseed oil hydrogenated to about 70 I. V. and the polyglycol obtained by the condensation of one mol of monoethyl ether of diethylene glycol with six mols of ethylene oxide Monoester of the fatty acids of cottonseed oil hydrogenated to about 70 I. V. and the polyglycol obtained by the condensation of one mol of monoethyl ether of diethylene glycol with eight mols of ethylene oxide Monoester of the fatty acids of cottonseed oil hydrogenated to about 70 I. V. and the monoethyl ether of tetraethylene glycol Monoester of the fatty acids of cottonseed oil hydrogenated to about 70 I. V. and the monoethyl ether of octaethylene glycol Monoester of the fatty acids of cottonseed oil hydrogenated to about 70 I. V. and the monoethyl ether of decaethylene glycol Polypropylene glycol of about 300 mol. wt. (Wyandotte Chem. Corp. Sample -2990, Pluracol P-284) about pentapropylene glycol Ether-glycol derived by the reaction of one mol coconut oil fatty alcohols with 1.8 mols isobutylene oxide Ether-glycol derived by the reaction of one mol coconut oil fatty alcohols with 2.4 mols isobutylene oxide Alpha monobutyl ether of glycerol Monoester of the fatty acids of cottonseed oil hydrogenated to about 70 I. V. and diglycerol Polyglycoi of about 300 mol. wt. prepared from a mixture of 2.6 mols ethylene oxide and 1 mol propylene oxide prepared byWyandotte Chem. Corp. and sometimes referred to as Puracol 2.6-M-298 Polyglycol obtained by reacting 1 mol ethylene glycol with 3 mols isobutylene oxide Monomethyl ether of a polyglycol prepared by the reaction of two mols ethylene oxide with one mol propylene oxide (Wyandotte Chem. Corp. Sample 0-2897, Alkyl Pluracol) Monopropyl ether of a polyglycol prepared by the reaction of two mols ethylene oxide with. one mol propylene oxide (Wyandotte Chem.

Corp. Sample 0-2894, Alkyl Pluracol) From the above it is clear that the number of compounds which may be successfully used in the practice of my invention is very great. Of outstanding preference, however, are those polyglycols containing at least two glycol units, each unit containing from two to four carbon atoms, and derivatives of such polyglycols in which the hydrogen atoms of one or both hydroxyl groups are substituted by etheriflcation with alkyl groups containing from one to eighteen carbon atoms.

The above description of the invention has been confined specifically to miscellas obtained in the extraction of cottonseed oil and soybean oil, and the invention is of particular importance in the case of cottonseed oil miscellas. However, the advantage of improved color obtainable with reduction in lye usage and with reduction in agitation time in the practice of the invention is realizedin the refining of miscellas obtained in the solvent extraction of other oleaginous materials.

Moreover, although the specific description of the invention has been-related to batch refining. it is to be understood that the advantages of my contribution may also be realized in continuous refining procedures employing continuous mixing of miscella and lye followed by continuous centrifugal separation of the refined miscella and precipitated foots.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. In the process of refining vegetable oils in solution in volatile solvents, the step of agitating said solution with an aqueous solution of sodium hydroxide in the presence of at least one nonionic compound, liquid at about F.. and of the group consisting of (l) ethers of polyhydric alcohols, said alcohols containing from two to three hydroxy groups and having from two to eight carbon atoms in the carbon skeleton thereof, and (2) non-ionic organic derivatives of such of said ethers as contain unreacted hydroxyl groups.

2. The process of claim 1, in which the designated compound is a polyglycol containing at least two glycol units, each unit containing from two to four carbon atoms.

3. The process of claim 2, in which the designated compound is polypropylene glycol having a molecular weight of about 400.

4. The process of claim 2, in which the hydrogen atom of one hydroxyl group of the polygiycol is substituted.

5. The process of claim 2, in which the hydrogen atom of one hydroxyl group of the polyglycol is etherifled.

6. The process of claim 2, in which the hydrogen atom of one hydroxyl group of the polygiycol is substituted with an alkyl group having from 51 to 1-8 carbon atoms.

7. The process of claim 2, in which the hydrogen atoms of both hydroxyl groups of the polyglycol are substituted.

8. The process of claim 2, in which the hydrogen atoms of both hydroxyl groups of the polyg lycol are etherified.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,190,589 Clayton Feb. 13, 1940 2,278,838 De Groote Apr. 7, 1942 2,307,058 Moeller Jan. 5, 1943

Claims (1)

1. IN THE PROCESS OF REFINING VEGETABLE OILS IN SOLUTION IN VOLATILE SOLVENTS, THE STEP OF AGITATING SAID SOLUTION WITH AN AQUEOUS SOLUTION OF SODIUM HYDROXIDE IN THE PRESENCE OF AT LEAST ONE NONIONIC COMPOUND, LIQUID AT ABOUT 80* F., AND OF THE GROUP CONSISTING OF (1) ETHERS OF POLYHYDRIC ALCOHOLS, SAID ALCOHOLS CONTAINING FROM TWO TO THREE HYDROXY GROUPS AND HAVING FROM TWO TO EIGHT CARBON ATOMS IN THE CARBON SKELETON THEREOF, AND (2) NON-IONIC ORGANIC DERIVATIVES OF SUCH OF SAID ETHERS AS CONTAIN UNREACTED HYDROXYL GROUPS.