WO2010063450A1

WO2010063450A1 - Method for reducing the 3-mcpd content in refined vegetable oils

Info

Publication number: WO2010063450A1
Application number: PCT/EP2009/008557
Authority: WO
Inventors: Klaus Schurz
Original assignee: Süd-Chemie AG
Priority date: 2008-12-02
Filing date: 2009-12-01
Publication date: 2010-06-10
Also published as: EP2361298B1; HUE035623T2; DK2361298T3; DE102008060059A1; ES2637347T3; EP2361298A1; PL2361298T3; PT2361298T

Abstract

The invention relates to a method for refining oils, wherein a crude oil is first degummed in such a manner that a degummed oil is obtained, the degummed oil is admixed with a bleaching earth and bleached, wherein a bleached oil is obtained, the bleaching earth is separated off from the bleached oil, and so a filter oil is obtained and the filter oil is deodorized, characterized in that water is added to the crude oil for the degumming, and the degumming is carried out without addition of acid at a temperature of below 70°C, and the degummed oil is preferably separated off from an aqueous phase, the degummed oil is heated to a temperature in the range from 80 to 100°C and the bleaching earth is added to the heated degummed oil in an amount of greater than 1.5% by weight, and the bleaching is carried out at a temperature in the range from 80 to 100°C.

Description

Applicant: Süd-Chemie AG

PROCESS FOR REDUCING THE 3 - M C P D - G E H A L T S IN REFINED PLANT OILS

The invention relates to a process for refining oils wherein a crude oil is first degummed to obtain a degummed oil, the degummed oil is mixed with a bleaching earth and bleached to obtain a bleached oil which separates the bleaching earth from the bleached oil so that a filter oil is obtained and the filter oil is desorbed.

In the industrial production of oils and fats, bleaching earths are used to remove turbidity, discoloration or even to remove oxidation accelerators. Adsorptive cleaning significantly improves the taste, color and storage stability of oils and fats. For purification, different classes of bleaching earths are used. A first group is the class of highly active, mostly montmorillonite-based bleaching earths (HPBE = High Performance Bleaching Earth). In particular, this group comprises acid-reacted montmorillonites, the acid activation being carried out in a complex process by dealuminating the crude clays with concentrated acids at high temperatures, usually at boiling heat. In this process, a bleaching earth product with a very high specific surface area and a large pore volume is obtained. Even the use of small amounts of this highly active bleaching earth leads to significant purification of the crude oils. Low amounts used in the bleaching process are therefore desirable, because the used bleaching earth for a residual the amount of oil binds, whereby the yield is reduced, and on the other hand, the used bleaching earth must be disposed of in accordance with applicable regulations.

A disadvantage of these highly active bleaching earths is the fact that dealuminating with acid during production results in large quantities of acidic salt-rich waste waters, which can be treated or disposed of only in complex processes. The high costs for waste disposal and the complex production process justify the comparatively high prices of such highly active bleaching earths.

Another group is the class of natural active clays (NABE = Natural Active Bleaching Earth). These naturally occurring bleaching earths have been used for hundreds of years for the purification of fats and oils. These nature-active systems (also called filler earth or filler earth) can be made available at very low cost. However, they have only a low bleaching power, so they are usually not suitable for the cleaning of hard to bleach oils and fats. Furthermore, in comparison with highly active bleachers, it is necessary to use substantially larger amounts of the adsorbent in order to achieve the desired bleaching result. As a result, however, higher losses of oil or fat must be accepted, since the bleaching earths can not be separated in pure form and certain amounts of oil or fat remain in the bleaching earth.

A compromise between low production costs and acceptable activity is represented by the third bleaching earth class, the so-called surface activated systems (SMBE = surface modified bleaching earth). Here, a natural active raw clay with small amounts of acid is applied and thus achieved an "in situ activation". In particular, attapulgite and hormite containing have for this process Rohtone proven. These have a very high specific surface area of natural raw materials of about 100 to 180 m ² / g and a pore volume of about 0.2 to 0.35 ml / g. However, since salts formed in the acid activation or unreacted portions of the acid are not washed out, they remain on the product and are at least partially deposited in the pores. As a result, these acid-activated bleaching earths generally do not achieve the same efficiency as achieved by highly active bleaching earths (HPBE) produced by dealuminating with acid. However, the simple manufacturing process allows a comparatively low-cost production, with no acid effluents being a particular advantage.

A subgroup of the SMBE is the Dry Milled Bleaching Earth (DMBE) .The raw clay is generally treated with an aqueous solution of the acid for the production of the SMBE, whereas for the DMBE a solid acid, mostly citric acid, is used for the activation mull the solid acid together with the raw clay.

In US 5,004,570 a process for bleaching oils is described wherein in a suitable vessel a slurry is prepared comprising the oil to be bleached, a neutral bleaching earth and a chelating polyvalent carboxylic acid. The carboxylic acid has an even number of carboxyl groups, wherein the carboxyl groups are arranged in pairs and the carboxyl groups of each pair can assume an ecliptic confirmation.

No. 5,151,211 claims a bleaching earth composition comprising a neutral bleaching earth comprising attapulgite and smectite in a ratio in the range of 0.3: 1 to 1.5: 1, the proportion of attapulgite and smectite being at least 65% by weight. % of the bleaching earth corresponds. Furthermore, the cooperation a polyvalent carboxylic acid having an even number of carboxyl groups, which are arranged in pairs, wherein the carboxyl groups can each adopt an eclipsed arrangement.

US 6,346,286 D1 claims a bleaching earth composition comprising a mixture of a particulate clay and a particulate polyvalent carboxylic acid wherein the carboxylic acid has a pK _a in the range of 1 to 7 and is substantially free of salts of organic acids. The clay has a moisture content of not more than 8% by weight based on the clay. Further, the polyvalent carboxylic acid is contained in a proportion in the range of 1 to 8 wt .-%, based on the composition in this. Furthermore, US Pat. No. 6,346,286 B1 describes a bleaching process in which the oil to be bleached is brought into contact with a particulate composition which comprises particles of a clay mineral and particles of at least one organic acid, the organic acid being substantially free of salts of the organic acid. Among others, citric acid is mentioned as a suitable organic acid.

After bleaching, the refined oil should meet certain color, taste and durability requirements. Thus, the oil must not be too dark and, depending on the type of oil, have a yellow to green color. Furthermore, the oil should be preserved over a longer period without taste deterioration, so do not taste rancid.

No. 7,179,491 B1 describes a process for bleaching oils, which process does not require any degumming of the oil or the use of alkali or other chemicals, such as acids or bases. The oil is extracted from marine sources, mammals or fish. The crude oil is first degassed in a vacuum. After the vacuum is broken with gaseous nitrogen was first silicic acid is added to the oil and again applied to the reactor vacuum. The vacuum is broken again and bleaching earth is added to the mixture. After vacuum has been re-applied to the reactor, the mixture is bleached. The vacuum is broken again and then the solid components are separated from the bleached oil by filtration.

In today's usual treatment, the oil is first degassed after drying and dried, for example, to remove dissolved oxygen. Subsequently, mucilages, in particular phospholipids, are removed. For this purpose, the dried and degassed oil is treated with phosphoric acid and stirred at about 95 ° C and atmospheric pressure for about 15 to 20 minutes. In order to be able to separate off the mucilages more easily, further water is added at the end of the degumming, for example in a proportion of 0.2% by weight. After a short while, the

Lecithin phase separated, for example by centrifugation. Subsequent bleaching of the degummed oil involves two stages, wet bleaching and vacuum bleaching. For wet bleaching, the degummed oil is mixed with 0.1 to 0.5% by weight of water and after the oil has been heated to 95 ^° C., 0.3 to 2% by weight of bleaching earth is added. The mixture is then stirred at normal pressure for about 20 minutes. Subsequently, a vacuum is applied (for example, 100 mbar) and the oil is stirred for a further 30 minutes at 95 ⁰ C. After bleaching, the spent bleaching earth is separated off, for example by filtering the mixture through a suction filter covered with a paper filter.

After bleaching, the oil is still deodorized. For this purpose, superheated steam, which has an outlet temperature of about 240 ⁰ C, passed through the oil to remove free fatty acids as well as unpleasant flavors and odors. The deodorization is carried out in vacuo at a pressure in the range of less than 5 mbar, preferably 1 to 3 mbar. After refining, the oil must meet certain requirements in terms of, for example, color, taste and shelf life. For example, the oil should not appear brown, but depending on the variety have a yellow to green color. A benchmark for this is the Lovibond color number red, which should be as low as possible. To increase the shelf life, the oil should have a very low iron or phosphorus content. Furthermore, the oil should be as insensitive as possible to oxidation in order to prevent the development of a rancid odor and taste.

In addition to the type of bleaching earth used, the process control during degumming and bleaching has a clear influence on the result of the oil refining. Thus, DE 10 2006 035 064 A1 describes a process for bleaching oils and fats, wherein

providing a crude oil derived from a vegetable or animal source; the crude oil is heated to a temperature in the range of 35 to 55 ⁰ C; - a bleaching earth is added to the heated crude oil; the heated crude oil is bleached; and the bleaching earth is separated from the bleached crude oil.

With this method it is possible, under otherwise identical conditions, ie with the same amount of added bleaching earth and the same bleaching conditions, to achieve lower Lovibond color numbers red and yellow than when the bleaching earth is added at 95 ^° C. To bleach a given color of the So reaching a lower level of bleaching earth is sufficient. The method has the advantage that the oil for the addition of Bleaching earth does not have to be heated to high temperatures and the bleaching mass can be reduced.

In oil refining, however, unwanted impurities can be generated, which can develop a harmful effect when consumed by humans.

3-monochloropropane-1,2-diol (3-MCPD) can arise in the production of food, e.g. in the production of soy sauce, in baking and toasting, but also in the refining of vegetable oils and fats. In animal experiments, 3-MCPD has been shown to be carcinogenic. In addition, its mutagenicity could be detected in vitro, but not in vivo. There is also evidence that 3-MCPD affects fertility in mammals.

3-MCPD can be present in the centers of life either in free or in bound form, for example in the form of a

Ester. 3-MCPD was found in different fats and oils. The concentration in vegetable fats and oils can range from several hundred to several thousand ppm, calculated as free 3-MCPD. The mechanism by which 3-MCPD is formed during the refining of fats and oils has not yet been fully elucidated. However, model studies have shown that chloride ions as well as glycerol and mono-, di- and triglycerides are potential starting materials in the formation of 3-MCPD.

For the content of 3-MCPD, limit values have already been prescribed in the EU for various foods. For example, a maximum of 20 ppm of 3-MCPD may be present in soy sauce or hydrolysed vegetable proteins. The EU expert panels and the WHO / FAO set a tolerable daily intake (TDI) of 2 micrograms per kilogram of human body weight. It is an object of the present invention to provide a process for refining oils by first degumming a crude oil so as to obtain a degummed oil, adding a bleaching earth to the degummed oil and bleaching to obtain a bleached oil , the

Bleaching earth is separated from the bleached oil, so that a filter oil is obtained, and the filter oil is deodorized, which leads to the lowest possible formation of 3-MCPD.

This object is achieved in a method having the features of patent claim 1. Advantageous embodiments of the method according to the invention are the subject of the dependent claims.

In the method according to the invention the degumming of the crude oil is carried out only with water without the addition of acids. The oil is then bleached at a temperature in the range of 80 to 100 ⁰ C, preferably at a temperature of about 95 ⁰ C. Surprisingly, it was found that the degumming has a significant influence on the concentration of 3-MCPD, which in the refining of oils and fats, bleaching has a significantly lower influence or the addition of bleaching earth lowers the concentration of 3-MCPD in the refined oil or fat after degumming. This was particularly surprising because even when using highly active bleaching earths (HPBE), which are prepared by extraction of Rohhtonen with hydrochloric acid, and therefore

Chloride levels, lower levels of 3-MCPD were found than after degumming and subsequent bleaching of the degummed oil, but no bleaching earth was added on bleaching. The inventors believe that precursors of 3-MCPD are formed during degumming, which are then converted to 3-MCPD during deodorization. According to the invention, therefore, there is provided a process for refining oils wherein a crude oil is first degummed to obtain a degummed oil, the degummed oil is mixed with a bleaching earth and bleached to obtain a bleached oil, the bleaching earth of the Bleached oil is separated, so that a filter oil is obtained, and the filter oil is deodorized, wherein:

for the degumming, water is added to the crude oil and the degumming is carried out without addition of acid at a temperature of less than 70 ^° C., and the degummed oil is preferably carried out by an aqueous process

Phase is separated, the degummed oil to a temperature in the range of

80 to 100 ⁰ C is heated and to the heated degummed oil, the bleaching earth in an amount of more than 1.5 wt .-% is added, and the bleaching at a temperature in the range of 80 to

100 ⁰ C is performed.

In the method according to the invention, a crude oil is initially provided in the usual way. This can be obtained, for example, in an oil mill by pressing. The crude oil can also be degassed and dried in the usual way.

The crude oil is then mixed with water and stirred at a relatively low temperature.

The degumming is preferably carried out in such a way that the crude oil is mixed with water before bleaching. The amount of water added for degumming is preferably less than 15% by weight, more preferably less than 10% by weight. According to one embodiment, the added amount of water is at least 0.2 wt .-%, according to another embodiment, at least 0.5 wt .-% and according to yet another embodiment at least 1% by weight. The percentages are based on the crude oil used. The degumming is carried out without the addition of acids.

The degumming is performed at a relatively low temperature of less than 70 ⁰ C, preferably less than 60 ⁰ C, preferably in the range of 35 to 55 ° C, more preferably in the range of 40 to 50 ⁰ C.

The treatment time of the oil for degumming is preferably selected in the range of 10 to 30 minutes, more preferably 15 to 25 minutes. After degumming, the

Lecithin phase separated from degummed oil, for example by centrifugation, decantation or by filtration. If the amount of water is less than 0.5% by weight, removal of the water phase may be omitted. However, it is preferred that even with smaller amounts of water, the water phase is separated from the degummed oil.

The degummed oil is heated to a temperature in the range of 80 to 100 ⁰ C, preferably 90 to 98 ⁰ C, preferably about 95 ⁰ C. It has been found that excessively high temperatures in lead lead to an increase in the concentration of 3-MCPD in the refined oil. Overheating of the oil should therefore be avoided. The bleached earth is then added to the heated degummed oil. It has been found that when too low amounts of bleaching earth, the concentration of 3-MCPD or 3-MCPD precursors, which have formed during degumming, can not be reduced sufficiently. The bleaching earth is therefore added to the heated degummed oil in an amount of more than 1.5% by weight, preferably in an amount in the range of from 2.0 to 3.0% by weight, based on the crude oil. The inventors assume that bleaching earth has only a low adsorption power for 3-MCPD or its precursors. It was found that 3-MCPD or whose precursors are contained in the oil only in amounts in the ppm range. However, an increase in bleaching amount used for bleaching above 1.5% by weight results in a marked reduction in the amount of 3-MCPD in the refined oil.

After adding the bleaching earth to the heated oil, the oil is then bleached in a conventional manner.

The bleaching can be done by applying directly after addition of the bleaching earth vacuum, so without having previously given water to the crude oil. The bleaching then takes place as pure vacuum bleaching. The vacuum bleaching is carried out at elevated temperature, more preferably at temperatures of 80 to 110 ⁰ C.

According to one embodiment, the bleaching is carried out in at least two stages, with first wet bleaching and then vacuum equalization.

For wet bleaching, the crude oil is first mixed with water. The amount of water is preferably selected in the range of 0.05 to 1.5 wt .-%, particularly preferably 0.1 to 1 wt .-%. The mixture is then stirred at 80 to 100 ^° C., particularly preferably 90 to 95 ^° C.

Subsequently, the vacuum is carried out at the above conditions, ie preferably at temperatures of 80 to 95 ⁰ C and a pressure in the range of about 100 mbar.

After bleaching, the bleaching earth is separated from the bleached oil. For this purpose, conventional methods can be used. The bleaching earth can be allowed to sediment and the supernatant clear oil can be decanted off. Usually, the bleached oil is filtered, for example through a paper filter, so that a filter oil is obtained. This after the separation of the bleaching earth Here, oil obtained from the bleached oil is referred to as a filter oil, regardless of the method used to separate the bleaching earth. The filter oil is finally deodorized. For this purpose, usual methods are used under the usual conditions.

For this purpose, superheated steam is passed through the oil, whereby a Vollraffinat is obtained. The superheated steam preferably has an outlet temperature in the range of 200 to 290 ⁰ C. The deodorization is preferably carried out for a time period of 30 minutes to 2 hours. The deodorization can be carried out in one stage, wherein the outlet temperature of the superheated steam is kept substantially constant. However, it is also possible to carry out the deodorization in several stages, wherein the temperature of the superheated steam is changed during deodorization. In this case, preferably superheated steam is first introduced, which has a temperature in the range of 250 to 290 ⁰ C. This first step is preferably carried out for a period of 20 to 45 minutes. Subsequently, the outlet temperature of the steam, is lowered, preferably in a range of 200 to 240 ⁰ C. The superheated steam is then preferably passed through the oil for a further 30 to 120 minutes. According to the inventors, deodorization releases 3-MCPD, which the inventors believe to be previously bound in precursors, for example, glycerides or compounds derived therefrom.

With the method according to the invention can be achieved with all bleaching earths a low concentration of 3-MCPD in the refined oil, so both for HPBE, as well as for SMBE and HUB. However, by careful selection of the bleaching earths used for bleaching, a further reduction in the level of 3-MCPD in the refined oil can be achieved.

For bleaching, surface-rich bleaching earths are preferably used.

According to one embodiment, it is provided that the bleaching earth has a specific surface area of more than 175 m ² / g, according to another embodiment a specific surface area of more than 220 m ² / g, and according to another embodiment a specific surface area of more than 300 m ² / g According to one embodiment, the bleaching earth has a specific surface area of less than 400 m ² / g.

Furthermore, according to a preferred embodiment, the bleaching earths used in the process according to the invention have a specific pore volume of more than 0.2 ml / g, more preferably more than 0.3 ml / g, particularly preferably a specific pore volume of more than 0.4 ml / g. According to one embodiment, the bleaching earth has a pore volume of more than 0.45 ml / g and, according to another embodiment, a pore volume of less than 0.95 ml / g. According to one embodiment, a bleaching earth is selected which has a pore volume in the range of 0.4 to 1.0 ml / g.

The specific surface area (BET surface area) and the specific pore volume are determined by means of nitrogen porosimetry according to DIN 66131 and evaluation according to the BJH method. The total pore volume refers to pores with a diameter of 2 to 130 nm.

The ion exchange capacity of the bleaching earths is preferably more than 15 meq / 100 g, preferably more than 25 meq / 100 g and in one embodiment more than 40 meq / 100 g. In itself, all customary bleaching earths can be used in the process according to the invention. As bleaching earth, therefore, both natural bleaching earths (NABEs) can be used, as well as acid-activated bleaching earths. Surface-activated bleaching earths (SMBE) can be used as acid-activated bleaching earths as well as highly active bleaching earths (HPBE), which are obtained by extraction of a crude clay with strong acids.

However, it has been found that the nature of the activation of the bleaching earth used in the process according to the invention has an influence on the amount of 3-MCPD contained in the refined oil. It was surprisingly found that acid-activated bleaching earths lead to lower concentrations of 3-MCPD in the refined oil. This is particularly surprising since the addition of acid during degumming leads to an increase in the concentration of 3-MCPD in the refined oil, ie the formation of 3-MCPD or of precursors of this compound is presumably acid-catalyzed.

The acid activated bleaching earth, as a 10% slurry in water, preferably has a pH of less than 5, and more preferably less than 4. In one embodiment, the pH of the slurry is greater than 2. In one embodiment, the slurry has a pH of less than 8.5, and in another embodiment has a pH of less than four. The pH is determined with a pH electrode.

On the one hand surface-activated bleaching earths (SMBE) can be used as acid-activated bleaching earths. These surface-activated bleaching earths are obtained by acid-plating a natural raw clay leaving excess acid on the clay. So no washing step is carried out after the activation. Before activation, the raw clay can be prepared in the usual way and, for example, dried or ground.

The surface activation of the raw clay can be carried out by covering the raw clay with a, preferably aqueous, solution of the acid used for the activation.

The assignment can be done, for example, by moving the raw clay and the solution of the acid is sprayed onto the raw clay. But there are also other methods possible to apply the solution of the acid to the raw clay, such as soaking.

The activation of the raw clay can be carried out, for example, in aqueous

Phase to be carried out. For this purpose, the acid is brought into contact with the crude clay as an aqueous solution. In this case, it is possible to proceed by initially slurrying the crude clay, which is preferably provided in the form of a powder, in water. Subsequently, the acid is added in concentrated form. However, the raw clay can also be slurried directly in an aqueous solution of the acid, or the aqueous solution of the acid can be applied to the raw clay. According to an advantageous embodiment, the aqueous acid solution can be, for example, preferably broken or powdered

Rohton be sprayed, the amount of water is preferably chosen as low as possible and, for example, a concentrated acid or acid solution is used. The amount of acid may preferably be between 1 and 10% by weight, more preferably between 2 and 6% by weight of a strong acid, in particular a mineral acid such as sulfuric acid, based on the anhydrous crude clay (atro). If necessary, excess water can be evaporated and the activated raw clay then ground to the desired fineness. As already explained above, no washing step is required in this embodiment of the method according to the invention. After abandonment of aqueous solution of the acid is only, if necessary, dried until reaching the desired moisture content. Most of the water content of the resulting bleaching earth product is adjusted to a proportion of less than 20 wt .-%, preferably less than 10 wt .-%.

The activation can be carried out with both inorganic and organic acids. Suitable inorganic acids are, for example, sulfuric acid, phosphoric acid or else hydrochloric acid. A suitable organic acid is, for example, citric acid.

Preferably, the excess acid and the salts formed during activation are not washed out. Rather, after the task of acid, as usual in the acid activation, preferably no washing step is carried out, but the treated raw clay dried and then ground to the desired particle size.

However, it is also possible to activate the raw clay dry and, for example, to mill the raw clay together with a solid acid. A suitable acid is, for example, citric acid. When grinding, the grain size is set in the desired range.

The amount of acid used for activation is preferably selected to be greater than the ion exchange capacity of the raw clay, preferably in the range of 100 to 140% of the ion exchange capacity of the raw clay.

A highly active bleaching earth (HPBE) is preferably used as the acid-activated bleaching earth. These highly active bleaching earths are obtained by extracting a crude clay at elevated temperature, preferably at about boiling heat, with a strong acid. Essentially aluminum ions from the Crisis are detached tallstruktur. After extraction, the bleaching earth is separated from the aqueous phase, for example by filtration, and then washed with water. This method is known per se to the person skilled in the art. The highly activated bleaching earth will also be ground to the desired grain size.

The grain size or the mean grain size of the bleaching earth should preferably be selected so that a complete and simple separation of the used bleaching earth from the refined product is possible. Preferably, the mean grain size of the powdered raw clay is selected in a range of 10 to 63 μm. Typically, the fineness is chosen so that on a sieve with a mesh size of 63 microns about 20 to 40 wt .-% of the mixture remain (sieve residue) and on a sieve with a mesh size of 25 microns about 50 to 65 wt .-% of Stay behind. This can be referred to as typical bleaching earth fineness.

The inventive method is suitable in itself for the refining of any oils and fats. However, the method according to the invention is particularly suitable for the refining of vegetable oils.

Furthermore, the bleaching process according to the invention is particularly suitable for low-phosphorus oils, which preferably have a phosphorus content of less than 100 ppm.

With particular preference, the process according to the invention is suitable for the bleaching of palm oil.

The invention will be explained in more detail with reference to examples. Examples:

The following analysis methods were used:

Surface / pore volume:

The specific surface was carried out on a fully automatic nitrogen porosimeter from Micromeritics, type ASAP 2010, in accordance with DIN 66131. The pore volume was determined using the BJH method (E.P Barrett, L.G. Joyner, P.P. Haienda, J. Am. Chem. Soc. 73 (1951) 373). Pore volumes of certain pore size ranges are determined by adding up incremental pore volumes, which are derived from the evaluation of the pore size ranges

Adsorption isotherms are obtained according to BJH. The total pore volume according to the BJH method refers to pores with a diameter of 2 to 130 nm.

Oil Analysis:

The color numbers in oils (Lovibond color numbers) were determined according to AOCS Cc 13b-45. Chlorophyll A determination was according to AOCS Cc 13d-55.

Ion exchange capacity:

To determine the ion exchange capacity (IUF), the raw clay to be investigated was added over a period of two hours

105 ⁰ C dried. Thereafter, the dried material was reacted with an excess of aqueous 2N NH ₄ Cl solution for one hour under reflux. After a service life of 16 hours at room temperature, it was filtered, whereupon the filter cake was washed, dried and ground, and the NH ₄ content in crude clay was determined by determining the nitrogen (CHN analyzer from Leco) according to the manufacturer's instructions. The proportion and type of exchanged metal ions was determined in the filtrate by ICP spectroscopy. Determination of dry residue

About 50 g of the air-dry mineral to be examined are weighed out on a sieve of the desired mesh size. The sieve is connected to a vacuum cleaner, which sucks all parts which are finer than the sieve through the sieve by means of a suction slot circulating under the sieve bottom. The strainer is covered with a plastic lid and the vacuum cleaner is switched on. After 5 minutes, the vacuum cleaner is switched off and the amount of coarser particles remaining on the sieve is determined by differential weighing.

Loss on ignition:

In a calcined, weighed porcelain crucible with lid, approx. 1 g of dried sample is weighed to the nearest 0.1 mg and annealed for 2 hours at 1000 ^° C. in a muffle furnace. Thereafter, the crucible is cooled in a desiccator and weighed.

Determination of 3-MCPD content

An aliquot of the oil to be examined is dissolved in t-BME / ethyl acetate and treated with a deuterated standard solution and a NaOCH ₃ solution. Subsequently, the fatty acids are separated from the aqueous phase with hexane. The aqueous phase is mixed with phenylboronic acid and derivatized in a water bath at 80 ^° C. for 20 minutes. After cooling, the 3-MCPD derivative is extracted with n-hexane and measured by GC-MS (EH +, SIM mode). Chromatography column: Fused silica capillary coated with methyl silicone / phenyl silicone. example 1

Bleaching a palm oil

A sample of crude palm oil is first heated to the temperature indicated in Table 1 for degumming and then dried and degassed for 15 minutes at 100 mbar. After degassing, the palm oil was added to the amount of 50% phosphoric acid or water indicated in Table 1 and stirred for 15 minutes at ambient pressure.

Subsequently, if appropriate, the aqueous phase was separated off (index "f" in Table 1), for the bleaching the oil was adjusted to the temperature indicated in Table 1 and then the amount of bleaching earth indicated in Table 1 was added. The oil was first bleached for 20 minutes at atmospheric pressure and then for 30 minutes at a reduced pressure of 100 mbar. The oil was filtered hot through a paper filter. The filtered oil was deodorized by first for 30 minutes superheated steam, which had an outlet temperature of 270 ⁰ C, and then for 60 minutes superheated steam, which had an outlet temperature of 240 ⁰ C, passed through the oil. Finally, the concentration of 3-MCPD was determined. The results are summarized in Table 1.

Table 1: Refining of palm oil

Table 1 (continued)

MM

SUPREME 112 FF, Supreme 114 FF, SUPREME 118 FF: Süd-Chemie AG, Munich

The bleaching earths used in the examples have the properties listed in Table 2:

As can be seen from Table 1, in a blank where the palm oil is not degummed and the bleach is run as a blank, that is, without the addition of bleaching earth, a relatively high level of 3-MCPD of 5,500 ppm is produced. If degumming is additionally carried out, the amount of 3-MCPD increases to 6,150 ppm when water is added, and when phosphoric acid is added, a very high concentration of 3-MCPD of 11,800 ppm is determined.

If a bleaching earth is added after degumming during bleaching, significantly lower concentrations of 3-MCDP are measured in full raffinate. The use of bleaching earth therefore does not increase the concentration of 3-MCPD in the Vollraffinat but adsorbs during the oil refining emerging 3-MCPD or precursors of this compound.

If acid is added during degumming, higher values for 3-MCPD in full raffinate are measured in comparison to degumming with water only. The amount of 3-MCPD decreases with decreasing amount of acid added during degumming (at a constant concentration of the acid) and with decreasing acidity of the aqueous solution. However, higher amounts of 3-MCPD are measured than in a degumming only with the addition of water.

If the temperature during degumming is further lowered and / or the amount of water added during degumming is reduced, this likewise leads to a decrease in the measured amount of 3-MCPD.

Claims

claims

A process for refining oils, wherein a crude oil is first degummed to obtain a degummed oil, the bleached oil is mixed with a bleaching earth and bleached to obtain a bleached oil, the bleaching earth is separated from the bleached oil, so that a filter oil is obtained, and the filter oil is deodorized, characterized in that

water is added to the crude oil for degumming and the degumming is carried out without the addition of acid at a temperature of less than 70 ^° C.,

the degummed oil to a temperature in the range of

80 to 110 ⁰ C is heated and to the heated degummed oil, the bleaching earth is added in an amount of more than 1.5 wt .-%, and

the bleaching is carried out at a temperature in the range of 80 to 100 ⁰ C.

2. The method according to claim 1, characterized in that for degumming the crude oil water in an amount of less than 15 wt .-% is added.

3. The method according to claim 1 or 2, characterized in that the degummed oil is separated from an aqueous phase,

4. The method according to any one of the preceding claims, characterized in that the bleaching earth has a specific surface area of more than 175 m ² / g.

5. The method according to any one of the preceding claims, characterized in that the bleaching earth has a pore volume of more than 0.2 ml / g.

6. The method according to any one of the preceding claims, characterized in that the ion exchange capacity of the bleaching earth is more than 15 meq / 100g.

7. The method according to any one of the preceding claims, characterized in that the bleaching earth activated an acid

Bleaching earth is.

8. The method according to claim 7, characterized in that the acid-activated bleaching earth is an HPBE.

9. The method according to any one of the preceding claims, characterized in that the oil is a vegetable oil.

10. The method according to any one of the preceding claims, characterized in that the oil is palm oil.