FR2581384A1 - Process for the extraction of tocopherol with the aid of methanol - Google Patents

Abstract

A material containing tocopherol is placed in contact with a quantity of methanol sufficient to form two phases, one of which is enriched in tocopherol, the latter phase then being separated and sufficiently cooled to cause the formation of two new phases, one of which is a second methanol phase enriched in tocopherol, which is separated to recover therefrom an even more purified tocopherol. The invention finds its main application in the preparation of vitamin E.

Description

 The invention relates to a process for the purification of tocopherol. It is known that the tocopherol compounds, also called vitamin E, are the active constituent of certain vegetable oils. Vitamin E activity refers to the physiological activity of this group of nutrients. Substances with vitamin E-like activity all belong to a particular set of compounds, which are derivatives of chromannol-6. These compounds are all tocol derivatives having a C16 isoprenoid side chain. The term "tocol" refers to 2-methyl-2- (4 ', 8', 12'-trimethyltridecyl) chromannol-6. These compounds, referred to herein as homologs, are alpha-, beta-, gamma- and delta-tocopherol, which are of primary importance for vitamin E type activity.

Among the other compounds also having a vitamin E-type activity, referred to herein as the "tocopherol" and "tocopherol homologs", are the compounds usually referred to as toco-mono, di- and tri- enols. These toco-enols are distinguished from other tocopherol homologs, but only because they possess an isoprenolated side chain.
Unsaturated C16. Natural toco-enols are also of interest because of their vitamin-E-type activity, and they are typically isolated-at the same time as tocopherol-saturated homologues, when using these natural sources to collect vitamin. E.

 These tocopherol homologs are isolated from a variety of natural sources, which are widely distributed in normal foods. They are found in maximum concentrations in certain cereal oils, particularly in mas and wheat oils, and also in barley and rye. But they are also found in other vegetable oils, such as safflower oil, soybean oil, peanut oil, cottonseed oil, linseed oil, sunflower oil, rapeseed oil, palm oil and other vegetable sources.

 Natural counterparts of tocopherol are generally isolated from natural products such as vegetable oils through various combinations of techniques such as esterification, saponification, extraction, distillation, ion exchange, adsorption chromatography, precipitation of sterols and crystallization. The tocopherol concentrate as isolated varies according to the particular separation technique used, and also, of course, from the vegetable source.

 A well-known industrial activity lies in the subsequent treatment of tocopherols and the upgrading of tocopherols other than alpha-tocopherols to increase their activity as vitamin E. However, for this, it is desirable and even necessary to isolate the homologues of the tocopherol having a vitamin E type activity, and separating sterols and other impurities.

 Among the known methods for isolating tocopherols are US Pat. No. 3,402,182, which relates to a method for separating mixtures of tocopherol homologues into individual components using an anion exchange form of basic form. This technique tends to be long and expensive. In addition, the resins tend to become clogged and lose their effectiveness.

 U.S. Patent No. 4,454,329 discloses a liquid phase fractionation process for isolating tocopherols in a purified form from a product stream. According to this process, it is possible to use one or more organic solvents, among them methanol, by putting them in contact with the esterified products for hydrogenation of a deodorized distillate, or with the residue remaining after elimination of the product, of the acids. esterified fat. The mixture of the solution in the solvent and the product containing the tocopherol is allowed to stand, then the supernatant is removed (solvent layer) and the solvent is removed from the recovered supernatant to retain only the tocopherol concentrate.

 The ease with which tocopherols are isolated from natural sources depends on the similarity of the properties of the impurities and the solubility properties of the tocopherols. For example, dehydrated sterols have properties similar to those of tocopherols, and their separation is extremely difficult. Dehydrated sterols have boiling points so close to those of tocopherols that no known distillation technique can separate them. Moreover, they can not be extracted properly by crystallization. Finally, they are not extracted by aqueous basic extraction, for the reason that they are extracted by the organic solvent together with tocopherol.

 It is an object of the present invention to provide a process for further purification of tocopherol-containing substances through a series of at least two extractions to take advantage of the differences which result in differences in extraction temperatures. Other objects of the invention will emerge from the description below.

This object is achieved, according to the invention, by a process in which a series of at least two extractions are carried out, the extraction temperatures being different for each extraction. This process for the purification of tocopherol comprises the steps of
(1) contacting a substance containing tocopherol with a sufficient amount of methanol to form two phases comprising
(A) a methanol phase, which contains the tocopherol and some impurities that were initially in the filler, and
(B) a phase consisting of impurities,
(2) to separate the phases,
(3) to sufficiently lower the temperature of the materials of the phase (A) to occur phase separation, separation forming two phases comprising
(C) a methanol phase enriched in tocopherol and
(D) a raffinate phase of tocopherol and impurities,
(4) to separate the phases, and
(5) to recover the tocopherol from the materials of the
phase (C).

Substances of: phases B and D may be subject to
another extraction. In addition, the materials of one or
the other. phases B or D may be added as a
charge material or combined with the charging material
for the extraction operation of steps 1 or 3.

The purification of tocopherol carried out by a series
-extractions at different temperatures takes advantage of
differences that exist-in terms of the solubility of the
tocopherol at different temperatures. The first extrac
stage 1, carried out at the highest temperature, will be
bilize a greater amount of tocopherol because the
The ability of tocopherol in methanol increases with
temperature. The second extraction, from step 3, takes place at a lower temperature, is more selective and gives a
highly purified tocopherol.

If we change the order of the temperatures, extracting
first tocopherol at the lowest temperature, - the second - extraction (step 3), at a higher temperature, would
very difficult to achieve. Moreover, if we obtained a system
two-phase system, it would result in an undesirable
on the purity of tocopherol. We will not be able to optimize
and improve purity as part of an extrac process
multiple use using different temperatures for each--
extraction by lowering the temperature of an extraction
to the next.

As regards the process according to the invention, the metha
used must be as dry as possible. Solubility
tocopherol drops rapidly when water is added
to methanol. Methanol should therefore preferably contain
less than 1% by weight of water.

One can also adjust the respective volumes of methanol
and the filler material corresponding to the extractions
steps 1 and 3, depending on certain characteristics
such as the concentration of tocopherol in the filler and the chosen temperature.

 If the temperature of the tocopherol-enriched phase is lowered, a natrial phase separation occurs, and another extraction is to be made.

As the tocopherol, at lower temperatures, is more solubl in methanol than are the impurities, phase C can be recovered more purified tocopherol than phase D.

Various preferred variants of the invention may be used. For example, it will be possible, in the context of a preferred embodiment of the process according to the invention, not only to lower the temperature of the methanol of the phase
A, tocopherol-enriched and separated, but also add a feedstock containing tocopherol supplementa.1.re course of step 3, while lowering the temperature. In another preferred embodiment of the invention, the methanol is extracted from the material of phase A after the separation step of step 2 and before the second extraction at lower temperature of step 3.

 After separation of the C and D phases, the tocopherol can be recovered by a suitable method, such as crystallization, distillation, vacuum purification or even further extraction. A less preferred method of recovery is to add water to the methanol phases enriched in tocopherol. Although the addition of water leads to the formation of an easily extractable tocopherol phase, e-au is difficult to extract from methanol, and a new use of methanol can not be carried out because the presence of water in methanol interferes with the extraction of tocopherol.

Preferably, this process is carried out against the current, which makes it possible to carry out during each extraction a certain number of contacts between the phases. More particularly, these contacts are made by successful contacts
because tocopherol, which initially shares with
impurities other than tocopherol, can be removed from the impurity-containing phase in one of the subsequent contacts, while impurities that have been extracted at the same time to arrive in the methanol phase can be extracted in the phase containing the impurities.

 The term "extraction" here refers to the dissolution and removal of a particular constituent from a mixture in a solvent. Here, tocopherol is the constituent, and methanol is the solvent. When a two-phase system can be realized, the tocopherol can be extracted with methanol. According to the present invention, the fact of carrying out several extractions, the temperature of each extraction being always lower than the temperature of the previous extraction, ultimately leads to a separated tocopherol having an ever greater purity. Indeed, the purity improves thanks to the lowering of the temperature. Both tocopherol concentrates at different concentrations and natural organic sources can be used as fillers in the context of the invention. Representative but non-exhaustive examples of tocopherol-containing substances are safflower and soybean oils. , peanut, cotton, flax, sunflower, rapeseed and palm. The starting materials may also be taken from other plant sources such as palm leaves, lettuce, alfalfa, rubber, latex and a variety of other plant materials.

 The substances which are representative of tocopherols and which are separated as impurities include sterols, sterol hydrocarbons, squalene and hydrocarbons. In addition, these substances can be separated even if their boiling point is the same as that of tocopherol.

 The present invention can be applied in all cases to fillers whose tocopherol content may be low or high. The temperature used in the extraction of step 3 of the process according to the invention is sufficiently lowered to ensure separation into two phases. The difference between the extraction temperature in step 1 and the extraction temperature in step 3 depends to a large extent on the particular circumstances and needs. For the extraction of step 3 (second extraction of tocopherol), the temperature difference should be at least 153C, and preferably at least 200C. Thus, there can be a temperature difference sufficient to modify the solubility tocopherol and impurities, with the result that the tocopherol of phase C is purer than the tocopherol of phase D. If desired, it could cause-phase separation by chasing methanol, or it can be add as filler for the second extraction an organic substance containing tocopherol.

 Preferably, the temperature of each extraction is adjusted according to the concentration of the tocopherol in the filler. The differences in tocopherol solubility at different temperatures can then be advantageously used. For example, when the tocopherol is extracted with methanol at a low temperature, there will be less tocopherol that will be solubilized, but the tocopherol will have a much higher purity than it could have at a higher temperature. Consequently, when a filler material has a low tocopherol content, it will be advantageous to use a low temperature extraction because the selectivity of the extraction with respect to tocopherol will be greater, the latter then having less of impurities. The de-tocopherol concentrate thus obtained will have a much higher purity.

 Any feedstock containing tocopherol can be used in this process. The fillers which may be used may contain from 3 to 35, from 35 to 50 or from 50 to 75 and even from 75 to 95% by weight of tocopherol. When the filler contains more than 75-8% by weight of tocopherol, the second extraction will preferably be at a temperature below 250C.

-Although the exact difference between the temperature of the extraction step 1 and that of the extraction step 3 depends to a large extent on the particular circumstances and needs, this temperature difference should be at least 150C, and preferably at least 200C. These two temperatures (extraction step 1 and extraction step 3) could be set to any two values in the temperature range in which the methanol is liquid. However, in practice, the low temperature extraction (step 3) should be performed at room temperature (250C) or at lower temperatures, and in this case the high temperature extraction should be carried out at a lower temperature. temperature of at least 150C higher, and preferably at least 200C higher.Thus, the low temperature extraction could conveniently be carried out at a temperature of
at about 60 ° C, the high temperature extraction being at a higher temperature anywhere from about 40 to about 1000 ° C. However, overall, the low temperature extraction can be conveniently carried out at a temperature
from about -98 to about 60 ° C, while the high temperature extraction (step 1) could then be suitably carried out at temperatures
from about 10 to about 1000C. Preferably, the low temperature extraction is carried out at about -10 to about 600 ° C while the high temperature extraction is realistic at about 40 to about 900 ° C.

 An elevated extraction temperature may advantageously lead to solubility. higher tocopherol in the methanol phase. In addition, when the pressure is higher than the atmospheric pressure, it is possible to use even higher temperatures. The pressure used in the process according to the invention can be from one to four atmospheres. Under 4 atmospheres, the maximum temperature can be about 100 0C. For temperatures above 900C, the preferred range of pressures is from about 1 to about 3 atmospheres. Of course, the minimum permissible temperature for low temperature extraction is the freezing point of methanol.

 During the extraction of step 3, the tocopherol can be recovered by gradually lowering the temperature, which leads to the gradual formation of the separated phase. It will then be possible either to gradually remove the phase in formation, or to remove it or recover it periodically at the different stages of formation of the tocopherol phase. it is important to observe that the formation phase tends to have an impurities / tocopherol ratio higher than the methanol phase (C) from which it is derived. Thus, the newly formed phase (phase D) will not have a tocopherol as pure as the material recovered from phase C after removal of methanol.If the temperature is not reduced to the freezing point of methanol, with gradual recovery or During the formation phase, the methanol remaining after removal of the tocopherol phase should be distilled off to allow the recovery of an extremely pure tocopherol.

 Another important variable you can play on is volume. The respective volumes of filler and methanol can be adjusted depending on the temperature to provide a two-phase system.

The low temperature extraction can be performed with a volume of methanol greater than the volume of the filler, to maximize the recovery of tocopherol. Accordingly, the ratio of the methanol volume to the volume of the filler may range from about 1.5: 1 to about 20: 1, preferably from about 2: 1 to about 12: 1. In particular, the ratio of methanol volume to charge volume for high temperature extraction may be in the range of about 1: 1 to about 12: 1.

 Tocopherol from the methanol phase can be used to separate a variety of recovery techniques. These methods include crystallization, vacuum distillation, precipitation, adsorption, or even the addition of water or another polar substance causing the separation of a distinct tocopherol phase. Whatever the recovery technique used, the temperatures and pressures used must be appropriate to the particular recovery technique used.

After the extraction of step 1 or step 3, the impurity phase of phase D, and sometimes phase
B, contains certain amounts of tocopherol. In such a case, another extraction may be performed to recover this tocopherol, or the materials may be combined with an additional filler. However, it is more particularly preferred to use a continuous extraction system operating by successive contacts so as to allow a certain number of contacts between the phases. Such a system, when used for the entire process (both in the extraction step 1 and the extraction step 3), minimizes the amount of tocopherol removed with the impurities, and decreases the amount of tocopherol impurities remaining in methanol enriched in tocopherol.

 Any apparatus suitable for liquid / liquid extraction operations may be used. The process according to the invention can therefore be carried out continuously or in a discontinuous manner. However, it is preferred to use a continuous extraction system. The most preferred continuous process consists of a number of counter-current phase contacts (multi-stage counter-current continuous system). When these contacts are made successively, the tocopherol which was initially re-stained with the impure organic material is transferred to the methanol phase at a later stage. Similarly, impurities that initially shared with methanol will transfer to the non-polar phase during subsequent phase-to-phase contacts. Such a system, in the process according to the invention, will give tocopherol with a high yield and purity.

 The invention will be better understood with reference to the following examples, in which all the percentages and parts are by weight, unless otherwise stated.

Example I
For the first step, two extractions were carried out at room temperature (about 240C). The filler used contained 64.5% by weight of tocopherol. During the extraction of NO 1 from the first stage, 100 g of filler was mixed with 400 g of methanol during extraction number two, 83 g of the 325 g filler were mixed together. During each extraction, a phase A and a phase B were formed.
Phase A - methanol phase containing tocopherol and certain impurities which were initially in the filler,
Phase B - Impurities phase (raffinate)
Phase A and B were separated, and phase A of both extractions was combined, then a sufficient amount of methanol was removed to make the dry extract of the combined phase from 12.6 to 20% by weight. Then the temperature of the remaining combined phase was reduced to 40C (reduction of about 200C) to form another system consisting of the following two phases:
Phase C - Methanol phase enriched in tocopherol; and
Phase D - raffinate phase of tocopherol and impurities.

 Samples of the 6 phases were analyzed, and the results are shown in Tables 1 and 2).

Example II
Two extractions were carried out continuously using two columns connected in series. Column 1 was maintained at 509C. Pure bottom methanol was introduced therein and countercurrently contacted with a feedstock comprising 39.4% by weight of tocopherol and fed to the top. The feedstock used for column 1 was the raffinate from the extraction in column 2.

After extraction in column 1 at 500 ° C., the tocopherol-enriched methanol was introduced into column 2, which was maintained at 200 ° C., and countercurrent methanol was contacted with methanol. (at 24 C)

Extraction <SEP> Phase <SEP> Mass <SEP> total <SEP> Mass <SEP> total <SEP>% in <SEP> weight <SEP> of <SEP> toco- <SEP> Mass <SEP> total
<tb><SEP> of <SEP><SEP><SEP> phase of <SEP> solids <SEP><SEP> phenol <SEP><SEP><SEP> solids <SEP> toco
<SEP> Phenol
<tb> 1 <SEP> A <SEP> 432 <SEP> g <SEP> 54.3 <SEP> g <SEP> 75.5 <SEP>% <SEP> 41.0 <SEP> g
<tb><SEP> B <SEP> 64.1 <SEP> g <SEP> 46 <SEP> g <SEP> 50.7 <SEP>% <SEP> 23.3 <SEP> g
<tb> 2 <SEP> A <SEP> 355.6 <SEP> g <SEP> 44.7 <SEP> g <SEP> 75.5 <SEP>% <SEP> 33.7 <SEP> g
<tb><SEP> B <SEP> 52.8 <SEP> g <SEP> 38.9 <SEP> g <SEP> 50.7 <SEP>% <SEP> 19.2 <SEP> g
<tb> TABLE 2 (at 4 C)

Phase <SEP> Mass <SEP> total <SEP> Mass <SEP> total <SEP>% in <SEP> weight <SEP> of <SEP> toco- <SEP> Mass <SEP> total
<tb><SEP> of <SEP><SEP><SEP> phase of <SEP> solids <SEP><SEP> phenol <SEP><SEP><SEP> solids <SEP> toco
<SEP> Phenol
<tb> C <SEP> 427.1 <SEP> g <SEP> 66 <SEP> g <SEP> 78.3 <SEP>% <SEP> 51.7 <SEP> g
<tb> D <SEP> 70.8 <SEP> g <SEP> 33 <SEP> g <SEP> 66.8 <SEP>% <SEP> 22.0 <SEP> g
<tb> contains 48.3% by weight of tocopherol. The raffinate from column 2 was then used as the feedstock for column 1. Samples of the tocopherol-enriched methanol, both downstream of column 1 and column 2, were taken. samples of the feedstock from columns 1 and 2, as well as the residual raffinate from column 2. The results are shown below.

Table 3
Results of the analysis after removal of the methanol in the samples.

% by weight of% by weight
tocopherol impurities
in the low
solids boiling point
lition in
the subjects
solid
Methanol phase enriched with tocopherol after column 1 48.1 10.8
Methanol phase enriched in tocopherol after column 2 74.0 2.2
Column 2 filler 48.3 5.6
Raffinate from column 2 and used as a feedstock in column 1 39.4 10.3
Final raffinate after column 1 19.1 13.7
After the second extraction at 200C, about 81% of the total tocopherol (initially in the filler) was in the methanol phase, and about 19% of the tocopherol remained in the final raffinate of the filler.

 Of course, the invention is not limited to the embodiments described above and shown, from which we can provide other modes and other embodiments, without departing from the scope of the invention. .

Claims (5)

claims  A process for the purification of tocopherol, characterized in that it comprises the steps of  (1) contacting a tocopherol-containing material with a sufficient amount of methanol to form two phases, comprising  (A) a methanol phase containing tocopherol and some impurities which were initially in the filler, and  (B) a phase impurities,  (2) to separate the phases;  (3) to sufficiently lower the temperature of the material of the phase (A) to occur phase separation, which leads to two phases comprising  (C) a methanol phase enriched in tocopherol, and  (D) a raffinate phase consisting of tocopherol and impurities,  (5) to separate the phases, and  (6) recovering the tocopherol from the material of phase (C).  2. Method according to claim 1, characterized in that step 1 takes place at a temperature of about 10 to about 1000C and under a pressure  about 1 to 4 atmospheres, and that the temperature of step 3 is about -98 to about 600 ° C, provided, however, that the temperature of step 3 is at least about 150 ° C lower than the temperature of step 3. step 1.  3. Method according to claim 2 characterized in that removes methanol from the material of phase A after step 2 and before step 3.  4. Process according to claim 1, characterized in that step 1 takes place at a temperature of approximately 40 to approximately 900 ° C and under a pressure  d about 1 to about 3 atmospheres, and that the temperature of step 3 is about -10 to about 600C, provided that the temperature of step 3 is at least about 200C lower than the temperature of step 1.  5. Method according to claim 3, characterized in that for the entire process is used a continuous multi-stage system against the current.