US2754309A - Vegetable oil refining - Google Patents

Description

United States Patent VEGETABLE OIL REFINING Hans Wolif and Lester P. Hayes, Decatur, 111., assignors to A. E. Staley Manufacturing Company, Decatur, 111., a corporation of-Delaware No Drawing. Application March 4, 1953,

' Serial No. 340,388

12 Claims. 01. 260-424) This invention relates, generally, to innovations and improvements in the refining of vegetable oils. More particularly, the invention pertains to the use of ketene as a degumming agent for lecithin-bearing vegetable oils, such as soybean oil, cottonseed oil, perilla oil, linseed oil, peanut oil, corn oil and tung oil whereby such oils can be rendered both heat break-free and acid break-free. The break-free vegetable oils provided by this invention are suitable for edible and industrial purposes requiring vegetable oils of the highest quality.

Crude vegetableoils of the class referred to above contain substances which in contact with water tend to settle. out or separate from the main body of the oil. Such substances are commonly referred to and designated as gum or gums and they are obtained in the commercial refining of vegetable oils, such as crude soybean oil, by the addition of water to the crude oil followed by centrifuging the mixture to separate the water component containing the gums from the main body of the oil. These gums, after drying, and in certain instances after known additional treatments, are marketed commercially as lecithin.

The separation of the gums or lecithins is carried out not only because of the commercial value of these substances as by-products but also because their presence in the oil is undesirable for most of the ultimate uses made of the oils. However, the water degumming treatment normally does not remove the final traces of lecithin or other gum-forming substances. The residual amounts. of these substances remaining in the oil, even though small, are suficient to cause a darkening and clouding of the oils on heating, usually with the formation of a visible black flock. This flock is commonly known and referred to in the art as break and an oil which shows such fluocculation or darkening on heating is considered to contain break.

If an oil on heating to 550 F. shows no darkening or flock but on the contrary tends to get lighter, i. e. heat bleaches, such an oil is considered to be heat break-free oil or a non-break oil. In addition, if the oil on heating. to 550 F. in the presence of hydrochloric acid shows no darkening or flock but lightens in color, it is considered to be an acid break-free or Gardner break-free oil according to. American Oil Chemists Society, Oflicial Method Ca 40, May, 1949.

The so-called break in industrial oils is undesirable because it interferes with various processing operations and shows up adversely in finished products. For example, large quantities of soybean oil are used by the paint and varnish industry, one of the principal uses therein being in the preparation of alkyd resins. These resins are used extensively in making white enamels (e. g. refrigerator enamels) and other high grade industrialfinishes and any break in the oil tends to darken and detract from the white color of such finishes.

' Break is also. undesirable when degummed vegetable oils are used for making edible oils since the, production of edible vegetable oils usually involves a deodorization 2,754,309 Patented July 10-, 1956 step wherein the oils are heated in the presence of steam to temperatures of 350-500 F. at pressures substantially below atmospheric. If there is break in the oils when they are deodorized in such a manner, they turn darkand their flavor is adversely affected.

Heretofore, the most extensively used technique for obtaining break-free vegetable oils has been the so-called alkali-refining process. Essentially this process consists of Washing either the crude oil or the water degummed oil with aqueous caustic solution. The byproduct of this alkali-refining operation is referred to as soapstock and is a dark greasy substance consisting mainly of a mixture of soaps, neutral oil and water. The alkali-refining technique entails loss of valuable neutral oil, partly by entrainment of the neutral oil in the soapstock and partly by hydrolysis of the neutral oil.

In addition to the alkali-refining technique, a number of other methods have been proposed for obtaining breakfree oils but insofar as has been learned, such methods have not been adopted in the industry. Patent No. 2,410,926, dated November 12, 1946, for example, mentions sulfarnic, oxalic, citric, picric'and maleic acids as being useful degumming agents for obtaining breakfree oils. Patent No. 2,448,434, dated August 31, 1948, discloses the use of halogenated lowaliphatic acids as degumming agents for use in preparing break-free vegetable oils. None of the degumming agents disclosed in these. patents has proven to be commercially successful for one reason or another.

It has been found according to the present invention that the use. of ketene in the process of water degumming vegetable oils permits the economic production of; breakfree oils and ofiers unexpected advantages over the methods used and suggested in the prior art. The first member of the. group of ketenes is itself known as ketene and has theformula CHzzCO. Ketene is readily available and. can be made on a commercial scale by known methods, such as by cracking or pyrolyzing acetone. This compound is a gas at ordinary temperatures.

The present invention offers the following advantages and improvements over the conventional alkali-refining process for refining vegetable oils to obtain break-free oils:

(1) The. break-free oils maynow be obtained in the degumming operation. alone and no additional refining step is required, whereas-alkali refining involves an added step over andabove the degumming treatment.

(2) Fatty acids can now be recovered in a single step as oncedistilled fatty acids during thedeodorization operation. These fatty acids are much more valuable than the soapstock obtained in the alkali-refining technique from which pure fatty acids can be recovered only in a two-step separation, i. e. acidification and distillation.

(3 The loss of neutral oil is substantially reduced because of the elimination of the separate alkali-refining step and because there is little or no hydrolysis involved.

(4) The deodorizedbreak-free oil has excellent flavor and good stability.

Certainother advantages of the invention will, in part, be obvious and will, in. part, appear hereinafter.

One of theunexpected features of the, present invention is the fact that break-free oils can normallybe made more efficiently from crude vegetable oils which havenot been either partially refined or allowed to stand long enough to permit a portion of the gums to settle out. In fact, the process of the present invention works better when used to refine-raw crude oils which have notv been allowed to stand or settle or refinedin any way.

While vegetable oils broadly may be treated inaccordance with the present invention, especially lecithinbearing vegetable oils, it has particular utility inconnec tion with the treatment of. soybean oil since soy lecithin is the most important commercial lecithin. In addition to soybean oil, other oils which may be treated to advantage in accordance with the present invention are corn oil, cottonseed oil, peanut oil, linseed oil, perilla oil and tung oil.

An important object of the invention is an economical method of obtaining heat and acid break-free vegetable oils, particularly soybean oil, without the use of alkali, by treating the crude oil in a water degumming operationwith a very small quantity of ketene (CHzzCO).

Another object of the invention is a method of obtaining heat and break-free vegetable oils, particularly soybean oil, without the formation of soapstock, and with little or no loss of neutral oil which comprises incorporating in the water degumming step or in association therewith a small amount of ketene, agitating the mixture of water, oil and ketene for a suitable period, and then separating the aqueous phase from the oil by a suitable method, the resulting degummed oil being heat and acid break-free and of a quality useful for making edible oils of superior flavor characteristics and for formulating white baked-on enamels and for other industrial uses.

Another object of the invention is an economical onestep method of degumming lecithin-bearing vegetable oils to render the same'both heat and acid break-free;

Another object of the invention is a method of degumming lecithin-bearing vegetable oils to render the same both heat and acid break-free which is especially eflicient in connection with oils which have not been partially degummed as the result of standing or partial refining.

Still another object of the invention is an economical process of making heat and acid break-free vegetable oils wherein fatty acids can be recovered during deodorization of the break-free oils as once-distilled free fatty acids.

Other objects of the invention will, in part, be obvious, and will, in part, appear hereinafter.

The process of the present invention involves incorporating a minor amount of ketene into a vegetable oil and then subjecting the oil to aqueous degumming treatment. The amount of ketene added may be as little as 0.015% by weight based on the weight of the oil and the particular amount added in any refining operation will depend upon the times and temperatures employed. In generab'when higher temperatures are employed, i. e.

60400 C., the times of treatment may be shorter and a the quantities of ketene used may be smaller, whereas at lower temperatures, e. g. 30 60 C., longer times are required and higher concentrations of ketene should be used. Accordingly, it will beseen that the concentrations of ketene used, the periods of treatment and the temperatures employed are factors which may vary within rather wide limits and there is a relatively wide range of particular conditions or combinations which are useful and give satisfactory results. In general, the preferred temperature range is from 6085 C. and preferably the ketene is added to the oil in a concentration of approximately 0.015-0.02% based on the weight of the oil. The ketene may be added to the oil rapidly either before or after the water is added, and the mixture stirred or agitated; The duration of the treatment is not critical but should be kept as short as practical in the interest of economy. The period of treatment will usually run from to minutes.

Full crude vegetable oils which have not been partially refined either by a refining treatment or by standing so as to allow the gums to settle out, respond more effivciently to the process of the present invention than do partially refined vegetable oils. In fact, full crude'vegetable oils containing on the order'of 0.5% break require smaller amounts of the ketene than do partially refined vegetable oils containing smaller break contents The following specific examples will serve iurther to Example 1 Ketene gas (CH2:CO) was generated according to the procedure outlined on page 122, vol. 5 of Journal of Organic Chemistry (1940), J. W. Williams and C. D. Hurd. The ketene stream was standardized by passing it for a given time through one normal aqueous solution of sodium hydroxide and back-titrating the amount of sodium hydroxide not neutralized.

The stream of ketene was introduced into 500 ml. of solvent extracted soybean oil at 60 .C. The oil contained 0.52% of break according to the Gardner test. The oil was vigorously stirred during the addition of the ketene which was allowed to continue for approximately. seconds before it was stopped. During this addition,

0.065 gram of ketene was passed through 450 grams of V the oil. This is the equivalent to the addition of 0.014% of ketene based on the weight of the oil. To the oil thus treated with ketene was added 6.75 grams of water (1.5% based on the weight of the oil) with mild stirring. After stirring the mixture for 15 minutes at a temperature of C., the mixture was placed in a centrifuge and the oil phase was separated from the aqueous phase. The resulting oil was break-free according to both the heat break test and the Gardner break test. The oil was bleached in the usual manner with bleaching clays and active carbon and then deodorized at a temperature of a 225 C. at a pressure of 4 ml. of mercury. Prior to deodorization the break-free oil had a free fatty acid content of 0.32% and after deodorization the free fatty acid content was 0.008%. The free fatty acids were recovered from the distillate.

The oil that was obtained was first quality edible soybean oil. The lecithin that was obtained on drying the gums from the separated aqueous phase was of good quality and was equal to the lecithin obtained by the conventional water degumrning process.

Example 2 To 500 ml. ofextracted soybean oil 7.5 grams of water was added. While the mixture was vigorously agitated, a stream of ketene was passed through the mixture for 160 seconds at 60 C. (0.26 gram of ketene or 0.058% on the basis of the weight of the'oil). As soon as the addition of the ketene was discontinued, the agitation of the mixture was stopped and the mixture was centrifuged so as to separate the aqueous phase'from the oil. The oil that was obtained was break-free and of good quality.

Example 4 The process of Example 3 was repeated but the ketene introduction was stopped afteronly seconds (0.13 gram of ketene or 0.026%). The oil that was obtained was not'break-free.

Example 5 The process of Example 3 was repeated but at a lower" temperature of 30 C. The oil that was obtained was not break-free. The process was repeated at 30 C. but

the ketene passage was prolonged to 220 seconds which yielded an oil that was break-free.

Example 6 Through 500 m1. of crude corn oil ketene gas Was passed for 160 seconds until 0.26 gram was added which is equivalent to 0.058% of ketene on the basis of the weight of the corn oil. The ketene was introduced in the oil while the oil was at a temperature of 60 C. 6.75 grams of Water (1.5% of the weight of the oil) was then added to the corn oil and the mixture was agitated for 15 minutes at 60 C. The mixture was then centrifuged and the oil obtained was break-free and of good quality.

Example 7 Ketene was passed through 500 ml. of crude peanut oil at 60 C. for 320 seconds until 0.12% ketene had been passed based on the weight of the oil. 1.5% of water based on the weight of the oil was added to the oil and the mixture was stirred for 15 minutes and then centrifuged. The oil obtained was break-free and of good quality.

Example 8 The procedure of Example 7 was repeated but the addition of the ketene was discontinued after 160 seconds. The oil that was obtained was not break-free.

The methods of the present invention may be carried out in known type equipment, either as a batch process or as a continuous process.

In view of the foregoing disclosure, those skilled in the art will be able to practice the invention either according to the specific embodiments and directions set forth above, or according to other embodiments which will be obvious. Accordingly, all matter set forth above is intended to be interpreted as illustrative and not in a limiting sense.

What is claimed as new is:

1. In the process of degumming a vegetable oil by treating the oil with water and thereafter separating the aqueous gum-containing phase from the oil phase, the improvement which comprises, treating the oil with a fraction of one per cent by weight of ketene while the oil is being treated with water.

2. The method of refining a vegetable oil so as to degum the same and obtain a break-free oil which comprises, intimately mixing with the vegetable oil suificient water for degumming and a fraction of one per cent by weight of ketene, and separating the resulting aqueous phase from the oil phase.

3. The method of refining a vegetable oil so as to degum the same and obtain a break-free oil which comprises, introducing into the oil in a relatively short period of time a fraction of one per cent by weight of ketene, thereafter mixing the oil with sufficient water for degumming for a relatively longer period, and separating the resulting aqueous phase from the break-free oil phase.

4. The method of refining a lecithin-bearing vegetable oil so as to degum the same and render it break-free which comprises, intimately admixing with the oil a small percentage of water and a fractional per cent of ketene based on the weight of the oil, agitating the mixture of oil, water and ketene until the aqueous phase will readily separate from the oil phase, and separating the said phases.

5. The method of refining a lecithin-bearing vegetable oil so as to degum the same and render it break-free which comprises, intimately admixing with the oil at a temperature in the range of about 30100 C. of at least about 0.015% of ketene and at least about 1.5% of water based on the weight of the oil, agitating the mixture until the aqueous phase will readily separate from the oil phase, and separating the said phases.

6. In the process of degumming soybean oil by treating the oil with water and thereafter separating the aqueous gum-containing phase from the oil phase, the improvement which comprises, treating the oil with a fraction of one per cent by weight of ketene while the oil is being treated with water.

7. The method of refining soybean oil so as to degum the same and obtain a break-free oil which comprises, intimately mixing with the soybean oil sufiicient water for degumming and a fraction of one per cent by Weight of ketene, and separating the resulting aqueous phase from the oil phase.

8. The method of refining soybean oil so as to degum the same and obtain a break-free oil which comprises, introducing into the oil in a relatively short period of time a fraction of one per cent by weight of ketene, thereafter mixing the oil with sufiicient Water for degumming for a relatively longer period, and separating the resulting aqueous phase from the break-free oil phase.

9. The method of refining soybean oil so as to degum the same and render it break-free which comprises, intimately admixing with the oil a small percentage of water and a fractional per cent of ketene based on the weight of the oil, agitating the mixture of oil, water and ketene until the aqueous phase will readily separate from the oil phase, and separating the said phases.

10. The method of refining soybean oil so as to degum the same and render it break-free which comprises, inti mately admixing with the oil at a temperature in the range of about 30100 C. of at least about 0.051% of ketene and at least about 1.5 of water based on the weight of the oil, agitating the mixture until the aqueous phase will readily separate from the oil phase, and separating the said phases.

11. The method of refining a lecithin-bearing vegetable oil so as to degum the same and render it break-free which comprises, intimately admixing with the oil a small percentage of water and a fractional per cent of ketene based on the weight of the oil, agitating the mixture of oil, water and ketene until the aqueous phase will readily separate from the oil phase, separating the said phases, deodorizing the separated oil with steam at elevated temperature and subatmospheric pressure, and recovering the distillate containing steam-distilled fatty material.

12. The method of refining soybean oil so as to degum the same and render it break-free which comprises, intimately admixing with the oil a small percentage of water and a fractional per cent of ketene based on the weight of the oil, agitating the mixture of oil, Water and ketene until the aqueous phase will readily separate from the oil phase, separating the said phases, deodorizing the separated oil with steam at elevated temperature and subatmospheric pressure, and recovering the distillate containing steam-distilled fatty material.

References Cited in the file of this patent UNITED STATES PATENTS

Claims (1)

1. IN THE PROCESS OF DEGUMMING A VEGETABLE OIL BY TREATING THE OIL WITH WATER AND THEREAFTER SEPARATING THE AQUEOUS GUM-CONTAINING PHASE FROM THE OIL PHASE, THE IMPROVEMENT WHICH COMPRISES, TREATING THE OIL WITH A FRACTION OF ONE PER CENT BY WEIGHT OF KETENE WHILE THE OIL IS BEING TREATED WITH WATER.