US2314621A - Process of refining oils of edible type - Google Patents

Description

Patented ar. 23,1943

one or EDLE as y William Kelley, Eos Angelica, Calii'l, assign'or, by mesne assignments, to Fiitrcl (Company oi'Caliiornia, Los Angeles, (Daliik, a corporation of California No Drawing. Application March 20, 1939,

Serial No. 263.055

Claims.

My invention relates to a process for refining oils of the general type-of edible oils, such as derived from vegetable, animal and fish sources,

and relates in particular to a process which is especially suited to the refining of .vegetable'or seed oils, such as cottonseed oil. Oils of this type are'also used in the arts.

To provide an understanding of the importance of my invention reference may be had to the cottonseed oil refining industry wherein the process generally followed is that of the American Oil Chemists Society. The loss of weight due to the carrying out of this refining process may be as high as. 30% or 40% on low grade crude oil mixtures, but for prime stock itordinarily ranges from 4 to 7%, and in most instances will be in the neighborhood of 5%. The caustic refined oils of edible type may be used in many instances without further purification, but it is also desirable at times to decolorize the caustic refined oil by contacting with anadsorbent. The loss of oil resulting from the decolorizing step is ordinarily in the range of 0.7%. It is an object of my present invention to provide a process for use in refining oils of the above character wherein the refining will be ordinarily in the neighborhood of to of the refining loss resulting from the use of the standard practiceand in certain instances much less than this. For example, I find-that by use of my process I am able to completely purify or process, with a be individually used and in conjunction with other steps diiiering from the process herein set forth.

It is an object of the invention to provide a process of the above character wherein certain of the impurities of the oil are separated by coagulation. This step'of coagulation employs simplecoagulating'means in small quantity capable of combining with or inducing'coagulation of these impurities.

It is an object of the invention to provide a process of the character set forth in'the preceding paragraph wherein the coagulant has an aqueous content and in the preferred practice of the invention includes the addition. of a small amount of water, ordinarily in the amount of 0.5% to 2.0% of the volume of crude oil mixture to be treated under suitable conditions of temperature, and also the addition of a supplementary coagulation medium consisting preferably of a-finely divided material, which not only enters into the accomplishment of the complete effect of coagulating but also permits the oil to be readily filtered from the coagulate.

loss of less than 2%, an oil which gives a loss of 6% when processed in the ordinary manner of refining oils of this type.

It is a further object of the invention to provide a process for refining'oil of-the above character wherein a number of simple steps are consecutively employed, each of which contributes to the efflcacy of the succeeding step or steps, with the result that marked economies are accomplished. The principal steps of my process are three in number, and may be referred to as steps of purification (1) by coagulation, (2) by adsorption and (3) by neutralization. Depending upon the intended use of the finished oil, the process may or It is a further object of the invention to provide a process for refining oils of the above character wherein the oil is prepared for a step of neutralization by a step of 1 adsorption wherein certain constituent elements which act as interferents or inhibitors to the efiectiveness of the. neutralizing medium are either removed by absorption and/ or converted by catalyzation.

It is a further object of the invention to provide a process for refining oils of the above character wherein the oil is neutralized substantially without loss of oil resulting from the application of a' quantity of caustic solution to the oil body to be refined, and wherein the soap stock produced in the neutralizing step contains substantially only the neutralizing fatty acids and a large part of the coloring matter.

' process is one of the reasons for the smaller, loss may not include a final step of decolorizlng or polishing-by use of an adsorbent. Certain of these steps arein themselves. sub-combinations of the complete preferred process set forth herein and are susceptible of separate utility in attaining specific valuable results. Accordingly, these steps may be selectively used to meet refining conditions imposed by individual characteristics of different specific oils. For example, the important steps or sub-combination processes may or greater yield inmy process as compared to the standard process referred to hereinabove.

In the practice of the process, I find that by a V suitable preparation or purification. of the oil a prior to the neutralizing step I am able to use a relatively weak caustic solution for the purpose of neutralization and to neutralize the fatty acid content of the oil substantially without the caustic attacking the neutral oil so as to convert a part of the oil into a soap. In this way certain losses found inthe prior practice of refining oils of this type are avoided. In some practices of the inventions, particular step of preparation of .the

This characteristic of the purities process for'neutralizing ployed need be very little in excess of the theoretical amount required to neutralize the acid content of the oil, wherein the strength of the caustic may be relatively weakv and wherein a rapid settling of the foots from the neutralized oil is attained even though a weak caustic solution is employed.

It .is an object of the invention to provide a process for purification of oils of the character described wherein the initial step of purification by coagulation employs a' small quantity of aqueous fluid, and also a relatively small quantity of filter cake consisting of adsorbent material which has been used for treatment or-decolorization of a similar oil and has retained therein a quantity of such oil. In this process of purification by coagulation certain unwanted constituents or imcombine with the water to form a "break consisting of small with this break, the fine particles of adsorbent material serve to assist in the coagulating effect and to cause a rapid and'eflective separation of the coagulate from .the oil. It appears that the oil entrained in the filter cake is given up to the body of oil to replace the impurities removed from the original oil body by coagulation so that it is found in most instances that the weight of the oil separated from the coagulate or foots is greater than or equal to the weight of the original oil body subjected to purification by coagulation.

It is an object of the invention to provide a an oil, wherein there is added during the step which I refer to as purification by coagulation a comminuted solid or porous material having the functions of forming a coagulate from which the oil may be readily separated by filtration.

' It is an object of the invention to provide a process for purification of oil by a step of coagulation wherein supplementary coagulants are employed. In the preferred practice of the invention these supplementary coagulants are added to the oil body at different times, and-cooperate to produce a coagulate which readily separates from the'oil.

visible globules, and combined- It is an object of the invention. to provide a process wherein the loss of oil resulting from the retention of oil in the filter cake is; substantially avoided, this characteristic oi; the; process involving the bringing of'the filter cake: i'nto con tact with a body of, oil and causing release of the oil from the filter cake, displacing. it with a fluid having a greater afilnity for the comminuted matcrial than has the retained oil. so thatthe same will be recovered instead of being discarded with the used filter cake.

It is a further object of the invention to provide a process of the character set forth in the preceding paragraph wherein the filter cake is added to a quantity of oil in a preceding stage in the process and the entrained oil is displaced from the particles of the adsorbentmaterial by a fluid for which the adsorbent has a natural aflinity, this released or displaced oil being thus combined with the body of oil which is being treated.'

. In one use of the extended form of my process, for example, in the treating of crude cottonseed oil, the crude oil is first purified by coagulation to remove glutinous substances, coloring matter and finely divided materials. v

V (a) To accomplish coagulation a small amount of coagulant is added to the oil at a relatively low temperature. This coagulant is characterized by ability to cause agglomeration of impurities which are to be removed and to also'produce coagulation. The coagulant above-referred to It is an object of the invention to provide a process wherein one of the supplementary coagulants is characterized by ability to agglomerate impurities which are dispersed throughout the oil body to be purified, and another of which is of a character to give weight to the mass or coagulate containing the impurities so that they will readily separate from the oil.

It is a further object of the invention to provide a process for refining oils of the type herein thought possible that the adsorbent material has a catalytic effect. In this process the filter cake. gives up'its retained oil to the body of refined oil to compensate for loss in weight resulting from the removal of the fatty acids from the oil.

is preferably an aqueous solution or mixture and the amount thereof is ordinarily just suflicient to produce the desired effect of agglomeration and a degree of coagulation. For 'most oils this coagulant may be simply water, or it maybe a mixture of water with other simple elements: for example, one of the salts or grain alcohol. I find that for many oils and, namely, for crude cottonseed oil, 1.3% of water, by weight, may be added to the oil at a temperature of substantially F. Ifind, however, that the amount of coagulant is variable between about 0.5% and 2.0%, by weight, depending on the crude oil stock which is to be purified. At this time the oil is stirred at a moderate speed and the stirring is ordinarily continued for approximately 5 minutes. The agitation produced by the stirring should be such that agglomeration of the impurities which are dispersed throughout the oil and a degree of coagulation will take place without any tendency towards emulsification of the oil.

(b) To the oil mixture I then add a supplementary. coagulant to' assist in the complete coagulation of the small bodies or globules of impurities and the coagulant which has caused agglomeration of these impurities. This supplementary coagulant is preferably of a character to give weight to the coagulate and may include or consist of a comminuted material of suitable weight is then added to the oil and the stirrin is continued until a complete and well-defined coagulation or break is perceived in the oil. The coagulate produced appears as small bodies or globules in the oil containing water, particles of adsorbent and the impurities which are being separated and removed from the oil by coagulation. A period of about 15 minutes is sufilcient under ordinary conditions to "accompl sh this completed coagulation.

(c) The coagulate thus formed in the crude oil is now separated from the oil. The preferred 1- method of accomplishing this is to allow the oil and coagulate mixture to stand so that in a period of about 4 hours the coagulate will settle to the bottom. The oil may then be drawn-01f from the layer of coagulate, after which the oil retained with the coagulate may be removed;

as, for example, by filtration which is readily ac After filtration it.

so that the retained oil in the filter cake is given to the body of oil purified by the first step of purification by coagulation. It is found that the weight of the body of purified oil is equal to and sometimes greater than the weight of the original crude oil to be purified by coagulation, the reason for this being that the oil displaced from the added filter cake while. it is intermixed with the body of oil replaces the weight of materials removed with the coagulate; accordingly, the first step of the process, which may be referred to as coagulant processing, is accomplished substantially without loss.

(d) The coagulant processed oil is thenprepared for neutralization by subjecting it to a step of purification by adsorption and/or catalyzation. This is accomplished by adding to the oil a, relatively small quantity 8f absorbent or catalytic material of the nature of fullers earth. but preferably being a clay of aluminum silicate origin. The amount of adsorbent here required is ordinarily in the range of 2% by weight of the=' body of oil, this adsorbent or catalytic material being mixed with the oil under relatively low temperature conditions, usually not exceedin 149 F. The material is retained in contact with the oil for a period of time-ordinarily about one noun-after which the oil is separated from the material, leaving a cake and a. body of oil conditioned or prepared for neutralization and saponification of its fatty acid content under such conditions that the neutralizing agent will not saponify any material quantity of the oil but will merely saponify the fattyacid content of the oil body.

. (e) The prepared oil resulting from the fore going step d is now refined with a weal; caustic solution, for example a caustic having a density of about 6 ea. in a quantity suificient to neutralize the fatty acid and remove coloring convstituents from the oil. Owing to the fact that the caustic solution is weal: as. compared to. the solutions ordinarily employed in refining of oils of this type, any small excess of this solution over that required to accomplish the specified results of neutralization and decolorization will not act to saponify the oil. Therefore, the loss of wei ht from the bodv "of oil is substantially only that of the saponified fatty acid and the color-forming constituents. The particles of soap or soapy solution containingjhe saponified atty acid and color constituents are found to be relatively fine and therefore tend to separate slowly from the oil, either by gravity or centrifugal action.

(f) To accomplish a more ready separation of the soap particles from the oil, I add thereto a supplementary settling agent having coagul nt characteristics. This is preferably a comminuted material: for example. filter cake, which gives u ts retained oil to the bodv of neutralized l.

thereby eliminating substantially the entire loss tice set out hereinabove.

ing to them sumcient weight to cause them to.

separate readily. If the oil is now allowed to settle it will be ordinarily found that in the bottom of the settling vessel or tank there will be a layer of caustic liquor containing adsorbent and the color constituents from the oil and a layer of saponified fatty acid with some content of adsorbent. The neutralized oil may be then separated from the foots in any of the known manners. It will be found to be substantially free of fatty acid and of such color and sweetness that it maybe used to produce salad oil or otherwisein the arts.

(9) Where an oil of lighter color is required, or where oil of special characteristics is required for a particular use in the arts, the refined oil from step .1 may be contacted with an adsorbent of comminuted form in the customary manner. In my process the retention of oil by the adsorbent material does not constitute a loss for the reason that the spent filter cake is passed back into the preceding stage or stages of the process. The adsorbent in its use in decolorizing the oil maytake on an amount of oil amounting to about 30%, for example, by weight of the adsorbent. Part or all of this filter cake may be used in step or step b wherein its o l content will b replaced by aqueous solution. Where the charg= ing stock cons sts of a prime grade cottonseed oil. the reduction in weight of the original crude oil treated amounts, at the end of t e refinin step, to about l%-and in many instances much less than this value-and the overall loss or reduction in quantity of oil from start to finish of the plant operation, or at the end of the decolorizing step q, is ordinarily less than 2% for a starting raw cotton oil of around 1.2 free fatty acid content.

In the treatment of certain grades and types of oils the order of applying some of the treating agents may change from the preferred prac- For example. in the first step of purification a the comminuted co= agulant may be mixed with the crude oil prior to the application of the liquid coagulant. and

in some instances it is possible to eliminate the It is found that the characteristics of oils vary I materially in accordance with various factors,

including source of the material from which the oil is obtained, methods of extraction or pressing. et ceera. I find in many instances that treatment of oils of this general type may utilize the p inciples of my invention in a fewer number of steps, as illustrated in the following example. In an alternative practice of the inven ion the crude oil mixture is purified by coagulation, and is prepared for neutralization of fatty acid and removal of color in a single step, eliminating the intermediate separate step oi mentary coagulant, in the form of neutralization and removal of oil.

' settle from the oil.

- the refining steps e and I.

mixed with a small quantity of coagulating solution, preferably of aqueous character, at-a temperature of approximately 110 F. The supplespent filter cake, is then added and the mixture is stirred under such conditions as to produce a break of the coagulate from the main body of oil in the may beseparated in condition for color by use of a caustic solution. To the purified and prepared oil separated from the coagulate, approximately 10% by weight of 6 31%. caustic soda solution is added and the oil is stirred for a sufficient period of time .to bring form of fine particles which from the oil, leaving the same the caustic solution into- 4 2,814,621 purifying or preparation of e oil by adsorption such aiiinity for said aqueous content that said or catalyzation. The crude oil mixture is first aqueous content will displace retained oil from said adsorbent substance; separating the oil from the coagulate resulting from the preceding step; and refining the oil.

2. A method of purifying glyceride oil stock comprising the steps of adding an aqueous treating agent to the oil and also a comminuted adsorbent material with entrained oil, said comminuted adsorbent material being of hygroscopic nature; and agitating the oilso as to bring the treating agent and the comminuted adsorbent material into intimatecontact with each other and with the oil stock whereby the oil will be treated and entrained oil released from said com- 7 minuted adsorbent material into said oil stock.

contact with all of the fatty-acid content of the.

This may be ordinarily accomplished in about one hour. The temperature, of the oil is then gradually raised to a maximum of about 1'10 F., after which the roots are allowed to This usually takes about 4 hours. The clear oil is .then pumped of! and washed by stirring it rapidly with 10% of water which has been previously heated to a temperature of about 180 F., and the temperature of the entire mixture of oil and water is slowly brought up to 180 F. and stirred rapidly for minutes. The water is allowed to settle from the oil.

-This water is found to contain slight traces of coloring matter. The oil is then dried under vacuum; and if a lighter color is desired, it may be bleached by contact with a finely divided adsorbent of the character. hereinbefore described.

In ordinary plant operations a reasonably large quantity of the refined oil may be subjected to further decolorizing, and the oil retained in the filter cake resulting therefrom may be returned to the oil production of the plant by using such filter cake in the first step of coagulation and preparation of the oil for neutralization, or .in

the oil and keeping the overall plant loss at a very low value. In the use of my process, I avoid the step of steaming the filter cakeas is the ordinary practice of recovering a small part of the a part of this retained oil my process enables the plant operator to recover substantially all ofit. The importance of the invention willbe recognized when we take into consideration that the contents of a tank of crude oil mixture weighs ordinarily 60,000 pounds. In-the use of my procass I ordinarily save 4%, content as compared to other processes now extensively employed. This means a saving to the industry of $100 or more per each tank car of oil processed.

An additional advantage of the process is that the fatty acid resulting from the method of refining employed, stock, has substantially twice the value p t P und of the crude fatty acids obtained from refining oils of this type-in the ordinary manner.- The reason for thisis that the ,fatty acids are relatively pure as compared to the fatty acids obtained directly from the soap stock produced in the ordinary edible oil refining process.

I claim as my invention:

1.'A method of purifying a glyceride oil mixture of the character described, comprising: mixing theoilwith an agglomerant having an aqueous content. and a filter cake which comprises. retained oil and an adsorbent substance having thereby recovering or 2,400 pounds. of this 3. A'method of purifying a glyceride oil mixture of the character described, comprising: refining the oil with an aqueous refining solution and employing at least part of the aqueous refining solution to displace into the oil retained oil from filter cake comprising used adsorbent of hygroscopic character and such retained oil, the

7 used adsorbent from which the entrained oil has been displaced assisting in the separation from the refined oil of soap stock resulting from the refining action of the refining solution on the original oil.

4;. A method in the purifying of glyceride oil, of recovering oil retained with adsorbent material of hygroscopic character as the result of bleaching a quantity of oil of the type being treated, which method consists in mixing the adsorbent, with its retained oil, with a body of oil, and combining aqueous material with the adsorbent wherebyit will release said retained oil I into said body of oil.

5. A method of recovering glyceride oil from filtercake, consisting of used adsorbent'material retained oil, and instead of recovering merely resulting from the preceding step;

of hygroscopic character and retained oil, comprising: bringing the adsorbent. material, having retained oil, into contact with an aqueous material in the presence of a body of oil, whereby the aqueous material will release the retained oil from the adsorbent into the oil of said body of oil.

6. A method of purifying a glyceride oil mixture of thecharacter described, comprising: mixing the oil with about two per cent or less of water and a quantity of filter cake comprising clay and retained oil,such clay for water so that the water will displace oil therefrom: separating the oil from the agglomeration subjecting the oil to a-refining step wherein a caustic solution and. filter cake are added to the oil, this second filterv cake also consisting of clay and retained oil, and the caustic solution having sufficient aqueous content to displace the retained oil from after reacidulation of he soap material of hygroscopic character having retained oil therein to agglomerate impurities and release said retained oil into the oil being treated; separating the coagulate thus formed from the oil: bleaching the purified oil by contacting the same with 'a quantity of adsorbent material; separating the oil from the adsorbent material and 8. A method of purifying an oil mixture of the character described, comprising: refining the oil with an aqueous alkaline refining solution of such having an affinity its retained oil: and caustic refining the bleached aaiaeai' low strength that it will have substantially no reaction on the oil but having suificient strength to neutralize the fatty acid of the oil, and employing at least part of the aqueous refining solution to displace into the oil retained-oil from filter cake comprising used adsorbent of hygroscopic character and such retained oil, the used adsorbent from which the entrained oil has been displaced assisting in the separation from the refined oil of soap stock resulting from the refining action of the refining solution on the original oil.

9. A method of purifying an oil mixture of the character described, comprising: refining the oil with the aqueous caustic refining solution of subs'tantially 6 Baum strength and employing at least part of the aqueous refining solution to displace into the oil retained oil from filter cake comprising used adsorbent of hygroscopic character and such retained oil, the used adsorbent from which the entrained oil has been displaced assisting in the separation from the refined oil of soap stock resulting from the refining action 5 of the refining solution on the original oil.

10. A method of purifying an oil mixture of the character described, comprising: subjecting the oil to a' preliminary purification to prepare it for refining; and refining the oil with an aque- 10 ous refining solution and employing at least part 15 the entrained oil has been displaced assisting in the separation from the refined oil of soap stock resulting from the refining action of the refining solution on the original 11.