EP2164627A1

EP2164627A1 - Process for the gentle refining of vegetable oils using natural bleaching earth

Info

Publication number: EP2164627A1
Application number: EP08773856A
Authority: EP
Inventors: Klaus Schurz
Original assignee: Sued Chemie AG
Current assignee: Sued Chemie AG
Priority date: 2007-07-04
Filing date: 2008-07-03
Publication date: 2010-03-24
Also published as: US20100298587A1; CA2691861A1; DE102007031039A1; WO2009003710A1

Abstract

The invention relates to a process for bleaching oils or fats. For this, a naturally active or non-naturally active bleaching earth is provided in a first vessel (10) and an organic acid in a second vessel (11). In a mixing vessel (8), the oil or fat which is to be bleached is admixed with bleaching earth and the organic acid, wherein the bleaching earth and the organic acid are added individually. Subsequently, the oil or fat which is to be bleached is bleached in a conventional manner.

Description

PROCESS FOR THE SAFE REFINING OF PLANT OILS WITH NATURAL LI CHE RD E

The invention relates to a process for bleaching oils and fats.

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-activated montmorillonites, wherein the acid activation is 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 these highly active _

Bleaching earth leads to noticeable cleaning of the crude oils. Low amounts used in the bleaching process are desirable because the used bleaching earth binds to a residual amounts of oil, 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 amounts of acidic, high-salinity wastewater, which can only be treated or disposed of 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 naturally active systems (also called filler earths) 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, much larger amounts of the adsorbent must be used in comparison to highly active bleaching earths 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 naturally active raw clay with small amounts of acid is applied and thus achieved an "in situ activation". Attapulgite and hormone-containing raw clays have proven particularly suitable for this process. 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.

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 with the carboxyl groups arranged in pairs and the carboxyl groups of each pair being able to adopt an eclipsed conformation.

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. Further, the composition contains a polyvalent carboxylic acid having an even number of carboxyl groups arranged in pairs, the carboxyl groups each having an eclipsed configuration. - -

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 pKg 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. As a suitable organic acid, u.a. Called citric acid.

The refining of oils and fats each requires a careful selection of the bleaching earth used to obtain a satisfactory result. This applies in particular to naturally active as well as surface-modified bleaching earths. Fats and oils are extracted from natural sources. Therefore, fluctuations also occur between different batches of the same type of oil. Especially in small to medium-sized farms, different types of oil are refined in the same plant. In this case, it would be desirable to be able to individually adjust the bleaching earth individually to the crude oil to be purified by adjusting the amount of bleaching earth and its degree of activation in each case to the oil.

The present invention therefore an object of the invention to provide a method for bleaching oils and fats, which allows an individual vote of the bleaching earth on the oils and fats to be bleached. 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 process according to the invention for bleaching oils and fats,

a natural or non-natural active bleaching earth is provided in a first container;

an organic acid provided in a second container;

an oil or fat to be bleached provided in a mixing vessel;

- added the bleaching earth and the solid organic acid individually metered to the oil to be bleached; and

- the oil to be bleached bleached.

In contrast to the previously customary procedure, the bleaching earth is not previously sprayed with the acid in advance or ground together with the acid to achieve intimate mixing, but the bleaching earth and the solid organic acid are not mixed until immediately before the bleaching or individually metered to be added to the oil or fat to be bleached. This makes it possible, on the one hand, to adjust the amount of acid and the amount of bleaching earth individually to the oil to be cleaned, so that differences between different batches of the same type of oil can be taken into account. On the other hand, several bleacher sorts can be stored, which are then mixed for bleaching with a likewise stored solid acid. As a result, in an operation where various oils are refined, the - -

used bleaching earths are individually adjusted by selecting a suitable bleaching earth and this is then mixed with the also stored separately, preferably solid organic acid. This is particularly advantageous from a cost point of view for companies that process varying types of oil.

As bleaching earths, natural or non-natural bleaching earths can be used. In the context of the invention, a naturally active or non-naturally active bleaching earth is understood as meaning a bleaching earth which has not yet undergone any activation steps, in particular not yet having been charged with an acid. The bleaching earth may already have some activity in the bleaching of oils and fats without acid addition, but this bleaching effect can be enhanced by the addition of an organic acid. These naturally active or non-natural bleaching earths are usually obtained from natural sources, ie mined in a mine. They are then dried and ground. The naturally active or non-natural active bleaching earth provided in the process according to the invention is prepared per se in the customary manner, ie it has a customary moisture content and a customary fineness. The moisture of the bleaching earth is usually adjusted to a water content in the range of 5 to 50 wt .-%, preferably 10 to 30 wt .-%. The fineness of the bleaching earth is usually adjusted so that the residue is on a sieve of mesh size 63 microns in the range of about 5 to 45 wt .-%, preferably 20 to 40 wt .-%. The mean particle diameter d ₅₀ is preferably in the range from 15 to 45 μm, preferably from 20 to 40 μm, particularly preferably from 25 to 35 μm. The naturally active or non-natural active bleaching earth is preferably provided in a form that it is free-flowing and flow out of the first container under the action of gravity _

can, without the need for a corresponding conveyor is required.

The organic acid is provided in a second container. The organic acid can be provided in dissolved form, preferably as an aqueous solution, or else as a solid powder. Again, the organic acid is preferably provided in a mold so that it can automatically flow out of the second container under the action of gravity.

In particular, when the bleached oils are used as food, such acids are preferably used as organic acids which are harmless under food law. Particular preference is given to using organic acids which are in solid form at room temperature. The organic acids preferably have at least two carboxyl groups. Exemplary organic acids, which are advantageously present in solid form at room temperature, are citric acid, oxalic acid or even tartaric acid. The use of citric acid is particularly preferred.

The oil or fat to be bleached is provided in a mixing vessel. This mixing container can be a preliminary container in which the oil or fat to be bleached is mixed with the naturally active or non-naturally active bleaching earth and the organic acid, in order subsequently to be transferred to a bleaching tank. However, the mixing container can also be designed so that after the addition of the naturally active or non-natural active bleaching earth and the organic acid, the oil or fat can be bleached directly in the mixing container. As a mixing container conventional containers can be used. These mixing containers are preferably equipped with a mixing device, for example in the form of an agitator. However, as a mixing device, for example, can also act a steam injection, with which - -

superheated steam is introduced into the mixed with the bleaching earth and the organic acid oil.

The naturally active or non-natural active bleaching earth and the organic acid are then added individually to the oil to be bleached. For this purpose, according to one embodiment, the first container can be provided with a first controllable metering device and the second container with a second controllable metering device, which can each be controlled individually. The metering can be carried out, for example, in such a way that a corresponding valve is provided on the first container or on the second container, through which the amount of naturally active or non-naturally active bleaching earth taken from the first container and the quantity of the product removed from the second container organic acid can be regulated in terms of quantity. But it can also be provided a special conveyor, for example, in solid starting materials, a screw conveyor or liquid starting materials, a pump with which the flow rate of the added bleaching earth and the organic acid can be controlled. After the addition of the bleaching earth and the organic acid, the oil or fat to be bleached is bleached. For this purpose, usual parameters are met. After the addition of bleaching earth and organic acid, the oil is heated, for example, at normal pressure to preferably 60 to 100 ⁰ C, preferably 70 to 95 ⁰ C, particularly preferably 80 to 9O ⁰ C and for a time of 10 to 40 minutes, preferably 15 to Stirred for 25 minutes. The treatment time depends on the oil or fat to be treated and can be determined individually, for example by sampling during bleaching. Subsequently, vacuum (for example 30 to 150 mbar, preferably 60 to 100 mbar) applied and the oil for about 10 to 60 minutes, preferably 20 to 40 minutes at about 80 to 14O ⁰ C, preferably 90 to 120 ⁰ C stirred. Subsequently, the bleaching earth is separated by, for example, the oil on with a Filtered filter covered with a paper filter is filtered. The filtration is preferably carried out at elevated temperature, preferably in the range of 60 to 90 ⁰ C, particularly preferably 70 to 85 ° C.

In the method according to the invention, the amount of added organic acid can be tailored individually to the oil to be bleached and to the natural or non-natural bleaching earth used. The appropriate amount can be determined by the expert by appropriate preliminary tests. Preferably, the proportion of the organic acid based on the weight of the naturally active or non-naturally active bleaching earth in a range from 0.1 to 10 wt .-%, preferably 1 to 5 wt .-%, particularly preferably 2 to 4 wt .-% selected.

The proportion of naturally active or non-naturally active bleaching earth added during bleaching depends on the oil to be bleached. By preliminary tests, however, the appropriate amount can be determined. Based on the weight of the oil to be bleached, the amount of bleaching earth added is preferably in the range from 0.01 to 10% by weight, preferably 0.1 to 5% by weight, particularly preferably 0.5 to 3% by weight. selected.

According to a preferred embodiment, the organic acid is provided in solid form. If the acid is present in solid form, it is known to be stable even after prolonged storage, so that no loss of quality must be accepted. Furthermore, a solid powder can be metered very well, for example via a screw conveyor. As a further advantage, organic acids, when in solid form, are less aggressive, ie corrosion on the reservoirs occurs only to a minor extent, or more favorable materials can be used to make the reservoir. _

As already explained above, the solid organic acid should be able to flow out of the reservoir under the effect of gravity. Surprisingly, it has been found that with certain organic acids, in particular citric acid, bridging occurs when the organic acid is stored in pure form. Preferably, therefore, the solid organic acid is mixed with a suitable flow aid. The flow agents used are preferably those flow aids which are harmless under food law. Suitable examples are silicon dioxide, diatomaceous earth or talc.

A clay mineral is preferably used as flow aid, in particular preferably a naturally active or non-naturally active bleaching earth.

The flow aid is preferably added in an amount of 5 to 30% by weight based on the solid organic acid. If smaller amounts of flow aid are added, bridge formation in the reservoir can not be reliably suppressed. If higher amounts of flow aids are used, the amount of added solid increases, which is particularly disadvantageous if the flow aid involved does not simultaneously show a bleaching effect on the oil or fat to be treated. Preferably, the amount of the flow aid is selected in a range of 6 to 25 wt .-%, particularly preferably 7 to 15 wt .-%.

The bleaching earth and the organic acid can be added to the oil or fat to be bleached in various ways.

According to a first embodiment, the organic acid and the naturally active or non-natural active bleaching earth are added separately to the mixing vessel to be mixed there with the oil or fat. The organic acid can also be in the form - -

be added to an aqueous solution. This is particularly advantageous if an aqueous solution of the organic acid is also used for other process steps, such as degumming of the oil. It is in this case then only a single reservoir required.

In another embodiment, the bleaching earth and the solid organic acid are blended into a bleaching mixture just prior to addition to the oil or fat to be bleached. The natural or non-natural active bleaching earth and the solid organic acid are removed to the desired amounts from the reservoirs and mixed intensively via a mixing device. The resulting bleaching mixture is then added to the oil or fat to be bleached.

As a mixing device, a screw conveyor is preferably used. The screw conveyor is supplied with the bleaching earth and the solid organic acid. In the screw conveyor then an intimate mixing of bleaching earth and organic acid takes place.

In order to achieve intimate mixing, the solid organic acid preferably has an average particle size D ₅₀ in the range from 20 to 40 μm.

According to a preferred embodiment of the process, the oil or fat to be bleached is degummed to a phosphorus content of less than 15 ppm prior to the addition of the bleaching earth and the organic acid.

The method according to the invention is explained in more detail below with reference to examples and a figure. It shows

Figure 1: a schematic representation of a device, as it can be used to carry out the method according to the invention. FIG. 1 shows schematically a device for carrying out the method according to the invention. The crude oil, which has been obtained, for example, by pressing corresponding plant seeds in an oil mill, is first subjected to drying and degassing (not shown), for example to remove dissolved oxygen from the oil. The degassed crude oil, which has a phosphorus content in the range of about 250 ppm, is then stored in a crude oil tank 1. From the crude oil tank 1, the crude oil is first fed to a degumming stage. For this purpose, the crude oil from the crude oil tank 1 is fed to a degumming tank 2. In the degumming stage, mucilages, in particular phospholipids, are separated off. Degumming may include pre-degumming as well as acid degumming. In the pre-degumming water is added to the crude oil and the mixture is stirred at about 70 to 80 ⁰ C at atmospheric pressure. The aqueous lecithin phase is subsequently separated off. The crude oil after pre-degumming has a phosphorus content in the range of about 100 to 200 ppm. In the case of the acid degumming shown in FIG. 1, the pre-degummed oil in the degumming tank 2 is mixed with an acid. As the acid, for example, a 50% citric acid can be used, which is taken from an acid storage tank 3. The Entschleimungsbehälter 2 is provided with a stirrer 4, which allows intensive mixing of acid and crude oil. The offset with the acid crude oil is heated in Entschleimungsbehälter 2 to about 70 to 100 ⁰ C and then stirred at atmospheric pressure. Exemplary conditions are an acid amount of 0.06 wt% of a 50% citric acid, a treatment temperature of about 95 ° C and a treatment time of about 15 minutes. At the end of acid degumming, water may still be added with the amount of water chosen at about 0.2% by weight to facilitate the separation of the gums. To separate off the aqueous phase, the mixture is transferred to a centrifuge 5, in which the aqueous phase containing the mucilage is removed from the Slime crude oil is separated. The mucilages are collected in a container 6. After acid degumming, the oil has a phosphorus content in the range of about 10 to 20 ppm. Degumming is necessary in combination with subsequent bleaching to reduce the proportion of phospholipids (phosphors) in the oil as well as the metals. If the degumming is dispensed with, the phosphorus and iron contents are often too high, even at sufficiently low Lovibond red / yellow color numbers in the refined oil. After degumming, the oil may optionally be dried and degassed (not shown). For phosphorous poor crude oils, such as palm oil, acid degumming may optionally be dispensed with and bleaching carried out directly. The degummed oil is first collected in a storage tank 7 for degummed oil.

The degumming is followed by a bleaching of the oil, in which first a wet bleaching and then a vacuum bleaching can be carried out. For this purpose, the degummed oil is transferred from the storage tank 7 into a mixing tank 8. In the mixing tank 8, the degummed oil is mixed with the bleaching earth and the citric acid. For this purpose, bleaching earth, which is stored in a bleacher silo 9, is transferred to a first feed container 10. Powdered citric acid (a), which is mixed with a flow aid (b), for example a naturally active or non-naturally active bleaching earth, is stored in a second feed tank 11. From the first storage tank 10, the bleaching earth is fed to a screw conveyor 12. Furthermore, the feed screw 12 is supplied from the second storage tank 11, the solid citric acid and the flow aid, so that the components are mixed in the screw conveyor 12. The bleaching mixture is then fed to the mixing tank 8, where it is intensively mixed with the degummed oil by means of the agitator 13. It is not necessary, - -

According to a further embodiment, only the bleaching earth can be transferred with the conveying screw 12 into the mixing tank 8, and separately, the citric acid from the second collecting container can be added directly to the mixing tank Delivery line 14 is provided, via which the citric acid is transferred directly into the mixing tank 8. From the mixing tank 8, the degummed oil mixed with the bleaching earth and citric acid passes into a bleacher 15. In the bleacher 15, the oil is initially heated to atmospheric pressure of about 80 to 100 ^° C. and stirred for about 20 minutes, then vacuum (for example 100 mbar) is applied and the oil is stirred for a further 30 minutes at about 90 to 120 ^° C. The oil is then fed to a filter 16 in which the used bleaching earth is bleached As a filter, for example, one with a Filterp apier occupied filter chute can be used. The filtration is carried out at a temperature of about 80 ⁰ C.

After bleaching, the oil can still be deodorized. The deodorization is not shown in FIG. For deodorization, superheated steam, having an exit temperature of about 240 to 260 ⁰ C, passed through the oil to remove free fatty acids and 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 has a phosphorus content of less than 3 ppm and an iron content of less than 0.1 ppm.

Example 1: Refining rapeseed oil

A degummed rapeseed oil was added with 0.75% by weight of the bleaching agents listed in Table 1 and then for 30 minutes bleached at 105 ⁰ C, wherein a reduced pressure of 60 mbar was applied. For deodorization, at a reduced pressure of less than 1 mbar, hot water vapor, which had an outlet temperature of 235 ^° C., was passed through the mixture for 60 minutes. Subsequently, the still hot oil is filtered through a paper filter to separate solids from the oil. The properties of the refined oils are summarized in Table 1.

Table 1: Refining of degummed rapeseed oil with various bleaching agents

c \

In Comparative Examples VI to V5, the following commercially available bleaching earths were used:

Supreme ^Φ 110 FF, ^Supreme® 112 FF, Optimum ⁰ 214 FF, Optimum ^Φ 210 FF; Manufacturer: Süd-Chemie AG, Munich, DE

For Examples El to E4 according to the invention, the following naturally active bleaching earth (NABE) was used:

EX 1221 (I); Manufacturer: Süd-Chemie AG, Munich, DE

In the bleaching according to the invention (El to E4), the following addition methods were used:

a: addition of a mixture of EX 1221 (I) and citric acid (El);

b: separate simultaneous addition of EX 1221 (I) and citric acid (E2);

c: addition of an aqueous citric acid solution (50%) and subsequent addition of EX 1221 (I) (E3);

d: Addition of EX 1221 (I) and subsequent addition of an aqueous citric acid solution (50%) (E4).

The parameters given in Table 1 were determined according to the following methods:

Lovibond red color number: The Lovibond red color number was determined in a 5% "cuvette (or crude ( ^* ) in a 1" cuvette) according to AOCS Cc 13b-45.

Chlorophyll A: Chlorophyll A determination was according to AOCS Cc 13d-55.

Peroxide value (POZ): The peroxide value was determined by the DGF method F-I 3b

Induction Period (IP): For the measurement of the induction period, the rancimat test was carried out in each case (Rancimat 743, Fa. - -

Metrohm). For this purpose, a constant air flow was passed through the heated sample and collected in a measuring vessel filled with distilled water. Oxidation results in short-chain organic acids, especially formic acid, which dissolve in the distilled water of the measuring vessel. The conductivity of the distilled water was measured as a function of time. The conductivity initially remains constant and then increases. A tangent was created on the rising branch of the curve and the induction time was read on the x-axis.

Anisidine number (ANZ): The determination was carried out according to C-VI 6e (77)

E ₂₃ 2_L The extinction at 232 nm was measured in a 1% solution in hexane. It is a measure of the number of conjugated double bonds produced by the decomposition of peroxides. It is therefore a measure of the oxidative preloading of the oil.

E ₂₇₀ : The absorbance at 270 nm was measured in a 1% solution in hexane. It is a measure of the number of conjugated triple bonds and therefore reflects the oxidative bias of the oil.

P, Fe, Ca, Mg: The determination of the elements was carried out by ICP according to DEV E-22

Example 2: Determination of flowability

To determine the vertical flowability of citric acid or natural bleaching earth powder or their mixtures with each other, the following experimental setup is used:

Citric acid (H ₃ Cit) is in proportion with natural bleaching earth (HUB) - -

95 5

90 10

85 15

80 20

75 25

70 30

intimately mixed. The total amount is 100 g. The educts as well as the mixtures prepared are each transferred to a powder funnel, which is closed at the bottom with a watch glass. The diameter of the Pulvertrichterauslaufes is 2.8 cm, the height is 14 cm. After removing the watch glass, it is observed - for the time being without any further mechanical action - whether the material drains very well or even well (assessment "++ to +"). If this is not the case, try tapping with (slightly) a little light to start a leak (if yes, judgment "x to o"). If there is no fluidity even then the assessment is "-").

The results are summarized in Table 2:

- -

Table 2: Flow behavior of mixtures of citric acid and flow aids

- -

REFERENCE ZE I CHENLI STE

1. First crude oil tank

2. Degumming tank

3. Acid storage tank

4th agitator

5. Centrifuge

6. Waste container

7. Storage tank for degummed oil

8. mixing tank

9. Bleacher silo

10th first template

11. second storage tank

12. Auger 13. Stirrer

14. Support line

15. Bleacher

16. Filter

Claims

- PERSONAL CLAIMS

1. A process for bleaching oils and fats, wherein:

a natural or non-natural bleaching earth is provided in a first container (10);

providing an organic acid in a second container (11);

an oil or fat to be bleached is provided in a mixing container (8);

the bleaching earth and the organic acid are added individually to the oil to be bleached; and

the oil or fat to be bleached is bleached.

2. The method of claim 1, wherein the organic acid is provided in solid form.

3. The method according to any one of the preceding claims, wherein the organic acid is citric acid.

4. The method according to any one of claims 2 or 3, wherein the solid organic acid has an average particle size D ₅₀ in the range of 20 to 40 microns.

5. The method according to any one of claims 2 to 4, wherein the solid organic acid, a flow aid is added.

6. The method of claim 5, wherein the flow aid is a natural active bleaching earth.

7. The method according to any one of claims 5 or 6, wherein the flow aid, based on the solid organic acid, in an amount of 5 to 30 wt -.% Is contained. - -

A process according to any one of claims 2 to 7, wherein the bleaching earth and solid organic acid are blended into a bleaching mixture prior to addition to the oil or fat to be bleached.

A process according to claim 8, wherein the solid organic acid and the bleaching earth are mixed in a screw conveyor.

10. The method according to any one of the preceding claims, wherein the oil or fat has been degummed prior to addition of the bleaching earth and the organic acid to a phosphorus content of less than 15 ppm.