Method for producing and purifying sterols

Abstract

The presently claimed invention relates to a process for the production and purification of sterols from oil distillates or oil distillation residues, particularly from the latter. Specifically, the presently claimed invention relates to a process for obtaining sterols in a pure form having reduced impurities and improved color.

Description

Technical Field

[0001] The presently claimed invention relates to a process for the production and purification of sterols from oil distillates or oil distillation residues, in particular from the latter. Specifically, the presently claimed invention relates to a process for obtaining sterols in a pure form with reduced impurities and improved color. Background Art

[0002] It is generally known to produce sterols from distillates obtained from the deacidification of vegetable oils or from distillation residues accumulated in the production of methyl esters, and more particularly in the production of methyl esters for "biodiesel" applications from crops.

[0003] Phytosterols and their esters have cholesterol-lowering properties, i.e., these substances are capable of reducing the cholesterol level in the blood. Therefore, they are used as food additives, for example, in the production of margarine, frying oils, sausages, ice cream, etc. The production of sterols and other unsaponifiable components (e.g., tocopherols) from distillates obtained, for example, from the deacidification of vegetable oils has been variously described in the patent literature, see EP-A2 0 610 742 (Hoffmann-LaRoche), GB-A1 2,145,079 (Nisshin Oil Mills Japan) and EP-A1 0 333 472 (Research and Development Board of Palm Oil).

[0004] EP 0 656 894 B1 (Henkel) describes a process for producing sterols in which, in the presence of a basic catalyst, the distillation residue from methyl esters (consisting essentially of glycerides, sterols, sterol esters and tocopherols) is transesterified with methanol. After neutralizing the catalyst, removing the excess methanol by distillation and optionally removing the catalyst by washing, the sterols are crystallized by reducing the reaction temperature from about 65 °C to 20 °C. The crystals thus obtained are washed with methanol and water. Unfortunately, the yield of sterols is not satisfactory.

[0005] EP 2 635 592 B1 (Verbio) discloses a process for obtaining phytosterols and tocopherols using a multiphase separation system for separating sterols and / or tocopherols.

[0006] EP1179535 B1 and EP1179536 B1 (both: BASF) disclose a process for the production of sterols by a two-step transesterification to obtain sterols from vegetable oil distillates. The crystallization of the resulting sterols and the washing with methanol and fatty acid methyl esters (FME) are disclosed as subsequent process steps in the dependent claims. Although "methyl esters" are disclosed as solvents used in the examples in EP1179536 B1, the "methyl esters" actually used in the examples and disclosed in the specification are FMEs from the transesterification of vegetable oils. EP1179535 B1 discloses the use of "FME" in its examples; it is also disclosed in

[0036] and

[0042] of EP1179535 B1 that the crystals obtained in examples a) and b) are "washed with a suitable solvent". However, which solvents these actually might be are not disclosed.

[0007] EP1169335 B1 (BASF) discloses a process for the crystallization of sterols from a specific mixture of methanol and FME in a specific ratio and for washing the resulting crystals. The aim of this disclosure is to provide sterols with a high yield and "good color quality". According to this disclosure, the key is the optimal amount and ratio of methanol during the crystallization process and thus the crystallization temperature which is said to result in the required improvement. The crystals obtained are then washed with FME, and it is said that this step further improves the color quality of the obtained sterol crystals.

[0008] It is noted that the "methyl esters" disclosed by EP1169335 B1 are clearly "FME", since these two descriptions / terms can be used interchangeably, as can be seen, for example, from

[0008] , where the washing of the crystals is mentioned twice, but the first time "methyl esters" are used, while "FME" is used the second time. Thus, claim 1 in the binding German version correctly uses the term "FME" (whereas claim 1 in the English translation incorrectly uses the term "fatty acid ester").

[0009] Therefore, the problem solved by the currently claimed invention is to provide sterols in high yield and high purity by an economical method avoiding high-pressure reactions, while more economically utilizing the distillation residues from the transesterified oils.

[0010] Several methods for the production of sterols from distillates have been reported. However, it remains a challenge to carry out methods for increasing the sterol yield without using solvents that are toxicologically and ecologically unsafe. In addition, it also remains a challenge to improve the color of sterols in high purity. Summary of the Invention

[0011] Surprisingly, it has been found that the yield, color and purity of phytosterols are significantly affected by the downstream processing technology used for vegetable oil distillates and the solvents used for purification. Therefore, the choice of solvent used in the purification process plays an important role in improving the color of phytosterols and reducing the impurity level without affecting the yield of the final product.

[0012] Therefore, the presently claimed invention generally relates to sterol production and more particularly to a method for producing sterols from the distillation residue of transesterified oils. In order to obtain sterols in pure form, they must be converted from the esterified state to the free state, otherwise it is difficult to separate them from the components accompanying them. The conversion to free sterols can be carried out, for example, by hydrolysis, saponification or transesterification. The presently claimed invention relates to the use of the transesterification mechanism. In addition, the present invention relates to a purification method in which the color of the final phytosterol product is significantly improved, and the amount of phytosterol esters as impurities and the solvent content are significantly reduced.

[0013] These improvements have been achieved with the method for producing and purifying sterols according to the present invention, said method comprising at least the following steps:

[0014] (a) providing an oil distillate or preferably an oil distillation residue, said distillate or residue containing sterol esters and partial glycerides;

[0015] (b) optionally transesterifying the partial glycerides with a lower alcohol in the presence of a basic catalyst to form fatty acid alkyl esters and glycerol;

[0016] (c) in the case of applying step (b), at least partially removing the excess lower alcohol, said basic catalyst, said glycerol and / or said fatty acid alkyl esters, preferably at least removing said lower alcohol and said fatty acid alkyl esters, more preferably at least removing said lower alcohol, glycerol and said fatty acid alkyl esters, and most preferably removing all four, each of these components being removed individually or jointly in a single step or as two, three or more steps, in parallel or sequentially, to form a product containing said sterol esters;

[0017] (d) optionally purifying the distillate or residue or - if steps (b) and (c) are applied - the product resulting from step (c) using an adsorbent;

[0018] (e) in the presence of a basic catalyst, transesterifying the sterol esters in the distillate or residue or - if steps (b) and (c) are applied - the product resulting from step (c) or - if step (d) is applied - the product resulting from step (d) with a lower alcohol to form free sterols;

[0019] (f) Optionally, at least partially remove the excess lower alcohol, the basic catalyst, the glycerol, and / or the fatty acid alkyl ester, preferably at least remove the lower alcohol and the fatty acid alkyl ester, more preferably at least remove the lower alcohol, glycerol, and the fatty acid alkyl ester, and most preferably remove all four. Each of these components is removed individually or jointly in a single step or as two, three, or more steps, either in parallel or sequentially.

[0020] (g) Optionally, add water to the product resulting from step (e), or – if step (f) is applied – to the product resulting from step (f), in an amount of 15% to 25% based on the mass of the total batch, to set the mass ratio of sterol:fatty acid alkyl ester (calculated as FME):lower alcohol (calculated as methanol):water to be substantially 1:2.5 - 3:2.2 - 2.5:0.8 - 1.2. During the addition of water, homogenize the reaction mixture by mixing to form an emulsion / suspension.

[0021] (h) Crystallize the sterol in the mixture obtained from step (e), (f), or (g) – depending on whether such steps are employed – under conditions of optional mixing.

[0022] (i) Remove the sterol crystals from the mother liquor by physical means.

[0023] (j) Wash the sterol crystals obtained in step (i) individually or jointly with a solvent, where the solvent is an organic solvent and / or a solvent mixture of more than one organic solvent. The organic solvent optionally but not preferably also contains water. The solvent is preferably a solvent mixture containing at least one aprotic polar solvent, more preferably a solvent mixture of at least one protic polar solvent and at least one aprotic polar solvent, and most preferably an azeotropic one.

[0024] (k) Optionally dry the obtained sterol crystals to remove one or more of the solvents; and

[0025] (l) Optionally melt-dry and form granules of the sterol crystals.

[0026] Definitions:

[0027] Before describing in detail the exemplary embodiments of the presently claimed invention, definitions important for understanding the presently claimed invention are given.

[0028] It should be understood that the present invention is not intended to be limited to the specific methods, protocols, reagents, etc. described herein, as these may vary, provided that the intent and purpose of the present invention are or can be achieved by these. It should also be understood that the terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the presently claimed invention, which is limited only by the appended claims. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art.

[0029] Unless otherwise noted, the following definitions are provided to illustrate and define the meaning and scope of various terms used to describe the present invention and the appended claims. These definitions should not be construed literally as they are not general definitions and are only relevant to the present application. The meaning of terms not defined herein is generally known to those skilled in the art or in the literature.

[0030] As used in this specification and the appended claims, the singular forms of "a" or "an" also include the respective plural forms unless the context clearly dictates otherwise.

[0031] In the context of the presently claimed invention, the terms "about" and "approximately" indicate an interval of accuracy that will be understood by those skilled in the art to still ensure the technical effect of the feature being discussed. The terms generally represent a deviation of ±20%, preferably ±15%, more preferably ±10%, and even more preferably ±5% from the indicated value. It should be understood that the term "comprising" is not limiting.

[0032] For the purposes of the presently claimed invention, the term "consisting of" is considered a preferred embodiment of the term "comprising". If a group is defined hereinafter as including at least a certain number of embodiments, this means that a group consisting preferably only of these embodiments is also covered.

[0033] Unless otherwise stated in the application as described above or below, if the terms "first", "second", "third" or "(a)", "(b)", "(c)", "(d)", "i", "ii", etc. relate to steps of a method or use or assay, there is no time or time interval consistency between these steps, i.e., these steps can be carried out simultaneously, or there can be a time interval of seconds, minutes, hours, days, weeks, months or even years between these steps. However, preferably, these steps are carried out in the order implied by their numerical or hierarchical names, i.e., first (a), then (b), then (c), etc., or first i), then ii), then iii), etc.

[0034] The term "final sterol product" refers to the phytosterol obtained after the purification step.

[0035] The term "(oil) distillate" encompasses edible vegetable oil distillates (VOD), which are even preferred.

[0036] The term "(oil) distillation residue" encompasses distillation residues of transesterified oils, which are even preferred. The distillation residue of the transesterified oil is preferably a fatty acid alkyl ester distillation residue, more preferably a fatty acid methyl ester distillation residue, especially a residue from biodiesel production.

[0037] The term "partial glycerides" encompasses all combinations of monoglycerides, diglycerides and / or triglycerides. In the case of oil distillates as starting materials, only triglycerides are present or almost only triglycerides are present, and there are few or no monoglycerides and diglycerides, while in the case of typical oil distillation residues, mainly triglycerides and diglycerides are present and only a small amount of monoglycerides.

[0038] Of course, it is also intended to combine various embodiments and preferred options of the various process steps disclosed herein in an actual complete process, so that for a specific performance of the overall process of one process step, a general process is selected; for another process step in the overall process, a preferred embodiment is selected; and for yet another process step, the most preferred option, etc. Thus, a general embodiment of one process step can be combined with a preferred embodiment of the next process step and with the most preferred embodiment of another process step. All such combinations are generally possible and are covered by the present disclosure. Detailed Description

[0039] Although the presently claimed invention will be described with respect to specific embodiments, the description should not be construed as restrictive.

[0040] In a first embodiment, the presently claimed invention relates to a method for producing and purifying sterols from an oil distillate, i.e., providing an oil distillate in step a) of the method.

[0041] In a second preferred embodiment, the presently claimed invention relates to a method for producing and purifying sterols from an oil distillation residue, i.e., providing an oil distillation residue, especially a distillation residue of a transesterified oil, in step a) of the method.

[0042] I. Method for Producing Sterols

[0043] a) Raw material for producing sterols, especially a distillation residue from a transesterified oil:

[0044] In an embodiment of the presently claimed invention, a distillation residue from a transesterified, more particularly non-refined oil (preferably having a residual acid value below 2) is used as a raw material for producing sterols.

[0045] Such residues can be obtained using known prior art methods as outlined above. Particularly suitable residues are from the post-treatment of vegetable oils containing sterols and usually also tocopherols. These residues are obtained by several esterification and transesterification steps, treatment with acids, etc., all of which are known in the art. One such known method is the production of biodiesel (i.e., fatty acid methyl esters).

[0046] Preferably, the oil distillation residue comprises residues derived from oils selected from the group consisting of soybean oil, sunflower oil, rapeseed oil, high erucic acid rapeseed oil (HEAR), low erucic acid rapeseed oil (CANOLA; low erucic acid CANadian oil), coconut oil, palm oil, palm kernel oil, and mixtures thereof; more preferably, the oil distillation residue comprises residues derived from soybean oil, sunflower oil, rapeseed oil (such as HEAR or CANOLA); even more preferably, the oil distillation residue comprises residues derived from sunflower oil, rapeseed oil, preferably HEAR.

[0047] These residues are preferably residues from the following: from coconut oil, from palm kernel oil, from palm oil, from soybean oil, from sunflower oil, from rapeseed oil (such as from HEAR and / or CANOLA); more preferably from soybean oil, sunflower oil, rapeseed oil (such as HEAR); even more preferably from sunflower oil and / or rapeseed oil, and especially HEAR, having an acid value of 0 to 10, preferably from 0 to 6, and comprising a mixture of diglycerides and triglycerides, FME, sterol esters, wax esters, and free sterols, preferably comprising 1 to 7 wt% triglycerides, 3 to 15 wt% diglycerides, 15 to 40 wt% FME, 40 to 50 wt% (especially 42 to 47 wt%) sterol esters, 3 to 4 wt% wax esters, and 3 to 15 wt% free sterols, as well as small amounts of monoglycerides.

[0048] In another embodiment of the presently claimed invention, the oil distillate is used as a raw material for the production of sterols. These distillates are preferably distillates of the following oils: coconut oil, palm kernel oil, palm oil, soybean oil, sunflower oil, rapeseed oil (such as from HEAR and / or CANOLA); more preferably soybean oil, sunflower oil, rapeseed oil (such as from HEAR); even more preferably sunflower oil and / or rapeseed oil from HEAR, containing 45 to 65 wt% triglycerides and 35 to 55 wt% sterol esters (total to 100%).

[0049] b) First transesterification step - transesterification of partial glycerides (optional):

[0050] If the content of unsaponifiable matter in the distillate or preferably the distillation residue is too low, by combining this process step with process step c), the distillate or distillation residue can be concentrated to a content of unsaponifiable matter containing sterol esters and usually also tocopherols as follows. Relative to the total weight of the concentrated distillate or distillation residue, the unsaponifiable matter is about greater than 20%, such as 35 to 60% by weight, preferably 40 to 55% by weight and more preferably 45 to 50% by weight.

[0051] In the currently claimed invention, in the process step of "transesterification of partial glycerides", preferably only triglycerides, diglycerides and monoglycerides are reacted with a short-chain alcohol to form fatty acid esters. The sterol esters remain substantially bound. Only a small amount of free sterols are formed. Methanol is preferably used as the alcohol, but other lower C2 to C4 alcohols can also be used, but they are not preferred.

[0052] Preferably, the lower alcohol is added in an amount of 5 to 40% by weight, and preferably 10 to 20% by weight, based on the transesterified oil distillation residue.

[0053] Preferably, the lower alcohol is selected from the group consisting of methanol, ethanol and isopropanol.

[0054] In a preferred embodiment, methanol is added in an amount of 5 to 40% by weight, and preferably 10 to 20% by weight, based on the transesterified oil distillation residue.

[0055] In one embodiment, the reaction is preferably carried out for a period of 2 to 20 minutes, especially 5 to 20 minutes and even more particularly 8 to 15 minutes, at a temperature of 80°C to 145°C, and more particularly preferably at a temperature of 80°C to 100°C. At these temperatures, a pressure of 2 to 10 bar, preferably 2 to 3 bar, is spontaneously established. Under these conditions corresponding to low-pressure transesterification, a catalyst must be added, and any basic transesterification catalyst can be used as the catalyst.

[0056] Preferably, the basic transesterification catalyst is selected from the group consisting of sodium methoxide, sodium hydroxide and potassium hydroxide.

[0057] In a preferred embodiment, a methanol solution of 30% sodium methoxide is the preferred basic catalyst, and the catalyst is preferably used in an amount of 0.5 to 1.8% by weight and more preferably 1.0 to 1.5% by weight, based on the transesterified oil distillation residue.

[0058] In another less preferred embodiment, in an alternative to low-pressure transesterification, transesterification can also be carried out under pressure. In this case, the reaction is preferably carried out at 220 °C to 260 °C and a pressure of 20 to 80 bar. For the residues accumulated during the distillation of the oil transesterified under high pressure, there is no need to add any catalyst, since the catalyst (usually a divalent metal soap such as Mn, Zn or Ca) is already present in a large excess.

[0059] This high-pressure transesterification may be reasonable if the acid value of the transesterified oil distillation residue is higher than 1, more particularly higher than 5.

[0060] In the currently claimed invention, suitable reactors are, for example, stirred batch autoclaves and continuous reactors such as turbulent tube reactors.

[0061] If optional step b) is applied, then step c) is applied, including steps c.1), c.2), c.3) and / or c.4). c.1) Removal of the excess alcohol (optional):

[0062] In an embodiment of the currently claimed invention, in the process step of "removing the excess alcohol", the hot reaction mixture of the "transesterification of partial glycerides" is expanded into a receiver while distilling off 55 to 85% of the excess alcohol. When using methanol, the system is significantly cooled to 65 °C to 85 °C, preferably to 75 °C to 85 °C. The residual alcohol remaining in the reaction product is preferably not distilled off and is used as a solubilizer in subsequent steps.

[0063] c.2) Removal of the catalyst (optional):

[0064] In an embodiment of the currently claimed invention, the catalyst is present in the distillation residue of the oil transesterified under pressure. These catalysts are preferably zinc soaps (2,000 - 3,500 ppm), but other soaps are also suitable. The distillation residue can also contain many other metals (such as Fe, Al or Na) at concentrations up to 300 ppm, and heavy metals (such as Pb, Cr or Ni) at concentrations up to 20 ppm. Non-metals (such as P, Si or S) are present at concentrations up to 300 ppm. The catalyst soaps and other metal compounds are soluble in the reaction mixture from the "transesterification of partial glycerides".

[0065] In order to be able to remove the catalyst, they are preferably converted into insoluble compounds with an acid and precipitated, as described in EP 0 656894B1. An aqueous solution of citric acid or phosphoric acid is preferably used as the acid. The amount of acid used is preferably one to two times the metal molar concentration. At the same time, the addition of the acid neutralizes the basic transesterification catalyst (such as sodium methoxide) used in the low-pressure transesterification of partial glycerides.

[0066] After precipitation, the precipitated metal-containing sludge is removed. Centrifugation is preferably carried out. If 15 to 30% of the excess alcohol remains in the product in the "removing excess alcohol" process step, phase separation is improved.

[0067] Alternatively, for centrifugation, the precipitated metal is adsorbed. Preferred adsorbents are amorphous silica gels loaded with organic acids, such as of the Trisyl type (specifically, Silica, 4030Silica, CP2-7887Silica, from Grace). In the case of removing metals by adsorption, all of the alcohol can be removed in the previous "removing excess alcohol" process step.

[0068] In both of these alternative processes, a residual metal content of less than 1 ppm can be achieved.

[0069] c.3) Removal of glycerol (optional):

[0070] In embodiments of the presently claimed invention, the catalyst-free product still contains excess alcohol and free glycerol. To prevent any reverse reaction in the next "removing fatty acid alkyl ester" step, free glycerol and residual alcohol are removed from the catalyst-free product by decantation or other phase separation means and, if desired, washed with water. The product is then preferably dried.

[0071] c.4) Removal of fatty acid alkyl ester (optional):

[0072] To concentrate the sterol ester, for example in a thin-film evaporator, the fatty acid ester is preferably distilled off. The methyl ester is preferably distilled at a temperature of 170 °C to 200 °C and a pressure of 1 to 5 mbar.

[0073] According to the presently claimed invention, partial glycerides are transesterified in the "transesterification of partial glycerides" process step. Since the sterols still exist to a large extent in the form of sterol esters, they have a higher boiling point and are not distilled off during the distillation of the fatty acid ester. They are completely retained as a concentrated valuable product in the bottom fraction. In addition, other low-boiling components - if present - can be removed and are preferably removed simultaneously, or - even more preferably - sequentially by this distillation method.

[0074] In embodiments of the presently claimed invention, the wax ester is also distilled off like the fatty acid ester and is subsequently separated from the fatty acid ester by winterizing. In this way, a sterol-free methyl ester or ethyl ester with a purity exceeding 97% is obtained.

[0075] Particularly preferred embodiments involving process steps b), c1), c3) and c4) are described below:

[0076] Using a lower alcohol (preferably methanol) as a solvent and reactant, and an alkaline transesterification catalyst (preferably sodium methoxide) as a catalyst, the distillate or preferably the distillation residue is subjected to transesterification. The aim is to convert the remaining glycerides in the residue into fatty acid alkyl esters (preferably methyl esters). After transesterification, the formed glycerol is removed by standard methods (such as decantation). This transesterification process and subsequent glycerol removal can be repeated once, twice or more times, but usually repeating once is sufficient, so it is a preferred embodiment.

[0077] Then the excess lower alcohol (preferably methanol) is removed, and subsequently optionally the remaining glycerol is further removed, which may reform as a separate phase during or after the removal of the lower alcohol (preferably methanol). Then, the formed fatty acid alkyl ester (preferably methyl ester) can be removed by, for example, distillation, thereby increasing the yield of the fatty acid alkyl ester, i.e., "biodiesel" in the case of fatty acid methyl ester.

[0078] d) Purification step by adsorption (optional):

[0079] As a further optional process step, an adsorbent (such as clay, earth and oxide) can be used to purify the distillate or preferably the distillation residue – or if steps (b) and (c) are applied – the product produced by step (c). Suitable adsorbents are well known, such as Trisyl grade (for example, specifically, Silica, 4030Silica, CP2-7887Silica, from Grace). By selecting a suitable adsorbent, this treatment allows for improving color, reducing the soap content and / or adsorbing trace metals and / or metal ions, preferably all of these are improved.

[0080] This treatment can be carried out at ambient temperature or elevated temperature. Considering the high viscosity of the residue or the concentrated residue, it is preferably treated at a high temperature. Suitable temperatures are from ambient temperature to about 100 °C, where a temperature of about 60 °C to 90 °C is preferred, mainly to obtain a good combination of the required viscosity and energy cost. Suitable treatment durations can be from 10 minutes to several hours, for example any time from even 5 to 10 hours. The duration mainly depends on the required degree of removal and the amount of contaminants present in the residue or the concentrated residue. At 75 °C to 90 °C, the duration is preferably about 0.5 to 10 hours, more preferably 1 to 5 hours, even more preferably 1 to 3 hours, and most preferably about 2 hours.

[0081] e) Second transesterification step - transesterification of sterol esters:

[0082] In the presence of a basic catalyst, the sterol esters in the distillate or the distillation residue or - if steps (b) and (c) are applied - the product resulting from step (c) or - if step (d) is applied - the product resulting from step (d) are transesterified with a lower alcohol to form free sterols. In the case where step (b) is omitted, step (e) is of course the first transesterification step. However, for the sake of consistency, it is still named "second transesterification step" herein.

[0083] In an embodiment of the presently claimed invention, the sterol esters are concentrated to more than 20%, preferably more than 30%, and even more preferably more than 40% in the bottom product of the fatty acid ester distillation process. In the presence of a catalyst, they are converted to free sterols by transesterification with a short-chain C1 to C3 alcohol (preferably methanol). Since the transesterification of sterol esters has to be carried out under more stringent conditions than the transesterification of partial glycerides, a larger amount of alcohol and catalyst as well as a longer reaction time are required.

[0084] The amount of alcohol added is 40 to 80% by weight and preferably 50 to 60% by weight of the bottom product of the fatty acid ester distillation process. In the case where methanol is the transesterification reagent, 40 to 60% by weight of the bottom product of the fatty acid ester distillation process is used. Herein, the catalyst can also be any basic transesterification catalyst, preferably those disclosed above as being available and preferred for the first transesterification reaction.

[0085] Depending on the pressure and time conditions, the second transesterification reaction is preferably carried out in the temperature range of 25 °C to 150 °C.

[0086] In a first embodiment of the presently claimed invention, the second transesterification reaction is carried out at a temperature of 78 °C to 145 °C and more particularly 80 °C to 100 °C, and a pressure of 2 to 10 bar, preferably 2 to 3 bar for a period of 2 to 10 hours, preferably 4 to 10 hours, and more particularly 5 to 8 hours. The distinct advantage of this embodiment is that a very high conversion rate is achieved in a relatively short time.

[0087] Furthermore, by using this embodiment in combination with the first embodiment described for the "first transesterification" step, it has been found that by combining two separate transesterification steps, the method for producing sterols can be made more economical and environmentally friendly. In the first transesterification step, monoglycerides, diglycerides, and triglycerides are reacted with a lower alcohol in the presence of a basic catalyst. Under mild conditions, the sterol esters mainly remain bound, and only a small amount of free sterols (< 1% by weight) are formed. After removing the excess alcohol, the transesterification catalyst, and glycerol, the fatty acid esters are removed, preferably by distillation, to produce a concentrate of sterol esters at the bottom of the column.

[0088] Then, in a second transesterification step carried out under more extreme conditions, the sterol esters are decomposed into free sterols. Due to the fact that impurities are removed in this transesterification step and the sterol esters are present in concentrated form, free sterols can be obtained under more economically favorable conditions. The first transesterification step proceeds very quickly and saves time, so it can be carried out in a simple reactor (e.g., preferably a tubular reactor).

[0089] Due to the reduced amount of starting product, a relatively small stirred reactor is sufficient for the second transesterification.

[0090] In a second embodiment of the presently claimed invention, the second transesterification step is carried out in the range from room temperature (e.g., 25 °C) to 100 °C, preferably to 95 °C, more preferably to 90 °C, and even more preferably to 88 °C, preferably in the range from 40 °C to 75 °C, and particularly preferably in the range from 55 °C to 70 °C, e.g., at a temperature of 60 to 65 °C, and additionally particularly at normal pressure, and for a period of 5 to 8 hours. The reaction can be carried out with or without reflux depending on the selected temperature and pressure. When methanol is selected - which is the most favorable alcohol used - when operating at ambient pressure, the reaction is carried out at or slightly below the boiling temperature of methanol. Good temperature control can thus be achieved.

[0091] This embodiment of the invention enables an energy-saving and cost-effective performance of the method and avoids expensive pressurized reactors as well as the complex and costly generation and maintenance of temperature and pressure. However, it is of course also possible to carry out the reaction at a higher pressure and thus also at a higher temperature, which results in a shorter reaction time (see above), but this is not preferred for reasons of energy consumption.

[0092] Furthermore, the low reaction temperature during the second transesterification step helps to reduce the operating costs relative to known methods and thus also improves the economy of the method relative to previous conventional methods.

[0093] However, of course, depending on the duration used for transesterification, at lower temperatures, compared to higher temperatures, the reaction duration must be extended, otherwise a satisfactory yield cannot be obtained. Thus, the net benefit in terms of energy savings depends on the entire process flow, the equipment used, and the temperature and duration of the reaction, since a simple shortening of time would result in a higher reaction temperature (if the yield is to remain constant) or a lower yield (if the duration remains constant). Optimizing such parameters of the reactor process based on the guidance disclosed herein is well within the skills of a typical chemical engineer.

[0094] II. Crystallization of sterols

[0095] According to the presently claimed invention, the free sterols produced by the method disclosed above are then purified by crystallization. However, the transesterified oil distillation residue, which is preferably used as a raw material in the method according to the presently claimed invention, contains impurities that are further concentrated in the product in the method described herein and interfere with the crystallization process. f) Removal of excess lower alcohol, basic catalyst, glycerol, and / or fatty acid alkyl ester (optional):

[0096] According to the presently claimed invention, other process steps can be optionally carried out, such as flash evaporation of excess alcohol, catalyst removal, and glycerol removal.

[0097] Thus, excess lower alcohol, basic catalyst, glycerol, and / or fatty acid alkyl ester are optionally removed at least partially from the reaction mixture obtained in the "second transesterification" step, preferably at least lower alcohol and fatty acid alkyl ester are removed, more preferably at least lower alcohol, glycerol, and fatty acid alkyl ester are removed, and most preferably all four are removed, and each of these components is removed individually or jointly in a single step or as two, three, or more steps, either in parallel or sequentially. For this purpose, reference is made to the preferred embodiments and features described above for process steps c.1) to c.4).

[0098] According to one embodiment (hereinafter referred to as "catalyst removal (II)"), the catalyst used in the transesterification of sterol esters is soluble in the reaction mixture. To be able to remove the catalyst, it is converted into an insoluble compound with an acid and precipitated, as described in EP 0 656 894 B1. After precipitation, the precipitated salt is removed. To achieve the separation of the organic phase from the aqueous phase, according to the present invention, 30 to 200% by weight, and preferably 50 to 100% by weight, of FME is added to the mixture based on the amount of the product used in the transesterification of sterol esters.

[0099] g) Addition of water to the reaction mixture (optional):

[0100] Optionally, water is added to the reaction mixture obtained in the "second transesterification" step, if said step is applicable, having at least partially removed the excess lower alcohol, basic catalyst, glycerol and / or fatty acid alkyl ester from the reaction compound (see above), and water is added in an amount in the range of 15% to 25% based on the mass of the total batch to set the mass ratio of sterol:fatty acid alkyl ester (calculated as FME):lower alcohol (calculated as methanol):water to be substantially 1:2.5 - 3:2.2 - 2.5:0.8 - 1.2. During the addition of water to the homogenized reaction mixture, an emulsion / suspension is formed by mixing;

[0101] Adding water can remove the substances that hinder the crystallization of sterols in a particularly simple way. Thus, by adding water, glycerol, catalyst and contaminants present in the reaction mixture are separated from the reaction mixture, and these substances enter the aqueous phase. In addition, the added water extracts a large amount of methanol that may still be present in the reaction mixture, so that the solubility of sterols is significantly reduced, and they crystallize out or at least start to crystallize.

[0102] Furthermore, during the addition of water to the reaction mixture, it has surprisingly been determined that when a specific water concentration is reached, spontaneous and very complete crystallization of sterols can already be observed at the reaction temperature, where a three-phase system (composed of an FME phase (i.e., the organic phase), an aqueous phase and sterol crystal form) is formed simultaneously, and the densities of the respective three phases increase in the above order.

[0103] Therefore, it has been shown that adding in particular in accordance with the aforementioned amount ratio of sterol:fatty acid alkyl ester (calculated as FME):lower alcohol (calculated as methanol):water being substantially 1:2.5 - 3:2.2 - 2.5:0.8 - 1.2 is particularly effective, achieving a clear separation of the three phases, thus greatly simplifying the further treatment of the reaction mixture, which in turn has a very positive impact on the economy of the process, especially with regard to energy saving and time saving of the starting products and obtaining the desired phytosterols.

[0104] To achieve the separation of the organic matter and the aqueous phase, according to the present invention, 30 to 200% by weight, and preferably 50 to 100% by weight, of FME can be added to the mixture based on the amount of the product used in the transesterification of sterol esters.

[0105] Optionally, the excess lower alcohol, basic catalyst, glycerol and / or fatty acid alkyl ester are at least partially removed from the three-phase system, and each of these components is removed separately or jointly in a single step or as two, three or more steps, in parallel or sequentially for said components. For this purpose, reference is made to the preferred embodiments and features described above for process steps c.1) to c.4).

[0106] h) Crystallization of sterols:

[0107] According to the invention claimed herein, the free sterols are then purified by crystallization. Successful crystallization generally requires a free sterol concentration of at least 20 to 25% by weight. As described above, sterol concentrations of >40% by weight can be achieved according to the method of the invention claimed herein and are thus well suited for this crystallization process step of the invention disclosed below.

[0108] If the concentration is still below the value that does not allow reasonable crystallization, it can be increased by distilling off the fatty acid esters produced in the "transesterification of sterol esters" process step. This procedure corresponds to the "removal of fatty acid alkyl esters" step (see above).

[0109] If, according to an embodiment of the invention claimed herein, the transesterification of sterol esters is carried out under pressure and the precipitated metal soaps are removed by adsorption, it is advantageous to add FME as a solvent. In this case, based on the amount of the product used in the transesterification of sterol esters, the amount of FME is again 30 to 200% by weight, and preferably 50 to 100% by weight.

[0110] In one embodiment, the invention claimed herein relates to the purification of a sterol fraction which, in addition to lower alcohols, mainly contains fatty acid alkyls (especially methyl esters), and the purification takes place by a known method, namely by slowly cooling a hot mixture (about 50 °C - 70 °C) to form phytosterol crystals, which crystals are formed in a crystallizer at a temperature of 15 °C to 50 °C, preferably 20 °C to 45 °C, more preferably 25 °C to 35 °C, even more preferably 20 °C to 30 °C. If necessary, the basic catalyst from the transesterification present in the mixture can be neutralized in advance, for example by adding citric acid or other organic or inorganic acids which are also suitable or acceptable for the intended subsequent use of the sterols; preferably, if the feed for crystallization permits, this neutralization is omitted.

[0111] In another embodiment, the emulsion / suspension in step (e), (f) or (g) is cooled to a temperature of 15 °C to 50 °C, preferably 20 °C to 45 °C, more preferably 25 °C to 35 °C, especially in an Armstrong crystallizer (available from Armstrong Corporation), so that the sterols crystallize in step (h), where the first crystals appear at about 65 °C to 50 °C, and when not carried out in one batch but in two batches, where the second batch is the filtered mother liquor of the first batch, then the crystals of the first batch appear at about 65 °C, while the crystals of the second successive batch appear at about 55 °C to 50 °C, and are subsequently further slowly cooled to 25 °C to 35 °C to obtain crystallization.

[0112] The lower alcohol is preferably selected from the group consisting of: methanol, ethanol and isopropanol. The lower alcohol is more preferably methanol.

[0113] In an embodiment of the presently claimed invention, only those mixtures having a weight ratio of sterol to methanol of from 100:25 to 100:75 in their production should be used. Otherwise, methanol must be added or distilled off. Under these conditions, crystallization starts at a temperature of 60 °C - 65 °C.

[0114] In another embodiment of the presently claimed invention, the ratio of sterol:methanol is in the range of 1:0.1 to 1:5, preferably 1:0.5 to 1:3, more preferably 1:0.5 to 1:2.5.

[0115] In an embodiment of the presently claimed invention, phytosterol crystals are formed at a temperature of from 15 °C to 50 °C, preferably 20 °C to 45 °C, more preferably 25 °C to 35 °C, even more preferably 20 °C to 30 °C, for example 20 °C, 21 °C, 22 °C, 23 °C, 24 °C, 25 °C, 26 °C, 27 °C, 28 °C, 29 °C, 30 °C, 31 °C, 32 °C, 33 °C, 34 °C or 35 °C.

[0116] In another embodiment of the presently claimed invention, phytosterol crystals are formed at a temperature of from 15 °C to 50 °C and more preferably at each temperature between 15 °C and 50 °C.

[0117] In an embodiment of the presently claimed invention, in order to increase the sterol yield, after filtering the crystal suspension according to process step i), a part of the mother liquor is recycled to, for example, the crystallization process. In the "catalyst removal (II)" process step, the return stream can be fed into the system together with the fatty acid ester. Alternatively, of course, a second separate crystallization of the waste mother liquor can be carried out to obtain more sterol therefrom. If necessary, further crystallization or further recycling to a previous crystallization can occur. Another method of recycling the mother liquor is to introduce it into the first (b) or second (e) transesterification step.

[0118] The recycling rate of the mother liquor depends to a large extent on the starting materials and thus also on the composition of the mother liquor. It can be in the range from 0.1 to 5.0, but in principle it can also be higher. A recycling ratio of 0.2 to 3.0 is preferably established.

[0119] III. Purification of Phytosterols

[0120] i) Removal of sterol crystals from the mother liquor by physical methods:

[0121] According to the presently claimed invention, the sterol crystals are separated by physical, in particular mechanical means (such as filtration, centrifugation and / or decantation, preferably filtration and / or centrifugation, more preferably filtration).

[0122] j) Washing of the sterol crystals:

[0123] In accordance with the invention claimed herein, a further purification step is carried out on the isolated sterol crystals.

[0124] In accordance with the invention claimed herein, the sterol crystals are further purified using a solvent or solvent system. The sterol crystals obtained in step i) (either as a separate process step or as a combined process step) are purified using an organic solvent and / or a solvent mixture of more than one organic solvent, which optionally further contains water but preferably does not further contain water, preferably a solvent mixture containing at least one aprotic polar solvent, more preferably a solvent mixture of at least one protic polar solvent and at least one aprotic polar solvent, and most preferably it is an azeotropic mixture.

[0125] In an embodiment of the invention claimed herein, the phase containing sterol (mainly containing sterol crystals) is washed with methanol to wash the crystals free of fatty acid alkyl esters (especially fatty acid methyl esters), wherein the amount of methanol is in the range of 20% to 800%, preferably 50% to 800%, more preferably in the range of 125% to 700%, more preferably 125% to 600%, more preferably in the range of 200% to 550%, and particularly preferably 200% to 400%, in each case based on the mass of the sterol crystal phase.

[0126] In another embodiment of the invention claimed herein, the purification of the sterol crystals preferably occurs in the presence of a solvent system (i.e., a solvent mixture) containing at least one polar aprotic solvent.

[0127] Preferably, the purification of the sterol fraction occurs in the presence of at least one polar aprotic solvent or nonpolar solvent selected from the group consisting of ethyl acetate, methyl ethyl ketone, and methyl acetate, dichloromethane, N-methylpyrrolidone, tetrahydrofuran, acetone, dimethylformamide, acetonitrile, dimethyl sulfoxide, heptane, and hexane, wherein ethyl acetate, acetone, methyl ethyl ketone, methyl acetate, heptane, and hexane are preferred.

[0128] More preferably, the purification of the sterol fraction occurs in the presence of at least one polar aprotic solvent selected from the group consisting of ethyl acetate, methyl ethyl ketone, and methyl acetate, dichloromethane, N-methylpyrrolidone, tetrahydrofuran, acetone, dimethylformamide, acetonitrile, and dimethyl sulfoxide, wherein ethyl acetate, acetone, methyl ethyl ketone, and methyl acetate are preferred, and wherein ethyl acetate, methyl ethyl ketone, and methyl acetate are even more preferred.

[0129] Particularly preferably, methyl acetate is used as the sole polar aprotic solvent.

[0130] In a preferred embodiment of the presently claimed invention, the purification of the sterol fraction takes place in the presence of at least one polar aprotic solvent and at least one polar protic solvent, which solvents are mixed together and / or form an azeotrope in the solvent system, wherein preferably, the polar protic solvent is selected from the group consisting of: water, ethanol, methanol, isopropanol, butanol, and acetic acid; more preferably selected from the group consisting of: water, ethanol, methanol, and isopropanol.

[0131] Particularly preferably, methanol is used as the sole polar protic solvent.

[0132] Preferably, the amount of the polar aprotic solvent present ranges from 25 to 75% by weight based on the amount of phytosterol, more preferably ranges from 30 to 50% by weight based on the amount of phytosterol, and each value is between 30% and 50% based on the amount of phytosterol, wherein ethyl acetate, methyl ethyl ketone, and methyl acetate are preferred polar aprotic solvents, and methyl acetate is more preferred as the sole polar aprotic solvent.

[0133] Preferably, the amount of the polar protic solvent present ranges from 5 to 50% by weight based on the amount of phytosterol, preferably ranges from 10 to 30% by weight based on the amount of phytosterol, and each value is between 10% and 30% based on the amount of phytosterol, wherein methanol is the preferred polar protic solvent.

[0134] After washing with at least one polar aprotic solvent and at least one polar protic solvent, the sterol crystals can be washed with a methyl ester (e.g., FME or methyl acetate, preferably methyl acetate).

[0135] According to a particularly preferred embodiment, the phase containing sterol (mainly containing sterol crystals) is washed.

[0136] 1) Optionally, wash with methanol at least once;

[0137] 2) Wash with a solvent mixture of at least one protic polar solvent and at least one aprotic polar solvent at least once, preferably one to three times, more preferably two or three times, and the solvent mixture is preferably an azeotropic mixture; and

[0138] 3) Preferably, wash with methanol at least once, more preferably one to three times, even more preferably once or twice.

[0139] The advantageous features and embodiments in this embodiment correspond to the preferred features and embodiments described above for step k).

[0140] In a further embodiment of the presently claimed invention, after step i) and before step j), the sterol crystals can be washed with a methyl ester (e.g., methyl ester and / or ethyl ester, in particular methyl fatty acid ester) to further "pre-wash" the crystals, further increasing the purity and / or color of the sterol crystals to be obtained.

[0141] k) Further drying of the sterol (optional):

[0142] The washed sterol crystals can be dried using various types of conventional dryers to remove the remaining solvent. Applying reduced pressure helps to increase the removal of solvent traces. This step is used for drying or "pre-drying", depending on the method employed and the desired content of residual solvent in the final sterol product to be obtained. The latter, of course, mainly depends on the intended use of the sterol.

[0143] Thus, in one embodiment, the sterol obtained as sterol crystals can be further dried by stripping, at a temperature of 150 °C to 170 °C for 1 to 3 hours, to remove the solvent.

[0144] l) Further purification of the sterol by melt drying to remove trace amounts of solvent within the sterol (optional):

[0145] After the "conventional" drying in the previous step k), the (pre)-dried crystals can be preferably melted under reduced pressure to remove the trace amounts of solvent encapsulated within the crystals. In this way, the residual content of the solvent can be further reduced, thereby obtaining certain higher product quality, i.e., also suitable for critical applications, such as direct application to humans in nutritional products or pharmaceutical products.

[0146] The melted sterol needs to be solidified. This can be done by simple cooling with any form of agitation, such as in an extruder, paddle dryer, etc. Other known methods for solidifying melts are granulation, in equipment such as granulators (including spray granulators), which can form near-spherical droplets, or simply in a dropping tower, where the molten material is dropped into cooler air or gas. All such methods ultimately obtain particulate solid sterol, which is preferably in a form that does not show dust but has good flowability and preferably high density, to obtain sterol particles with easy-to-handle characteristics. In addition, rolling, pressing, melting, and spraying (drying) are suitable particle formation processes.

[0147] Thus, in a further embodiment, the obtained and preferably (pre)-dried sterol is subjected to a particle formation process, preferably granulation, more preferably spray granulation, which is preferably carried out under liquid nitrogen to obtain solid, near-spherical, low-to-no-dust sterol particles with a very low content of organic solvents, suitable for direct use (including human oral administration).

[0148] In an embodiment of the presently claimed invention, for measuring the Gardner color number, the phytosterol is provided in the form of a 10 wt% pyridine solution. Preferably, when measured as 10 wt% sterol in pyridine, the Gardner color number of the final sterol product is less than 4.0. More preferably, when measured as 10 wt% sterol in pyridine, the Gardner color number of the final sterol product is less than 3.0, preferably less than 2.0, more preferably less than 1.5, even more preferably less than 1, such as less than 0.9, 0.8, 0.7, 0.6, 0.5, and any value between and below 4 and 0.5.

[0149] Preferably, based on the total weight of the purified phytosterol, the solvent content in the purified phytosterol is below 100 ppm, more preferably below 50 ppm, more preferably below 20 ppm, and even more preferably below 10 ppm, such as 5 or 1 ppm or even lower, and each value is between and below 100 and 1 ppm.

[0150] Preferably, based on the total weight of the purified phytosterol, the sterol ester content in the purified phytosterol is below 10 wt%, more preferably below 5 wt%, more preferably below 2 wt%, even more preferably below 1 wt%, and most preferably below 0.5 wt%, such as 0.1 wt%, 0.05 wt%, and each value is by weight between 5 wt% and 0.05 wt% and below.

[0151] Advantages:

[0152] The presently claimed invention is associated with at least one of the following advantages:

[0153] 1. The method is applicable to various starting mixtures and does not involve the use of solvents that are toxicologically and ecologically unsafe.

[0154] 2. The better utilization of the distillation residue results in an economically and ecologically safe method that is easy to implement on an industrial scale.

[0155] 3. Due to the lower pressure / temperature of the transesterification, the energy consumption is lower.

[0156] 4. The Gardner color number of the obtained phytosterol is less than 4.

[0157] 5. By using the above purification method, phytosterol is obtained in a high yield with a very low sterol ester content (i.e., < 10%).

[0158] 6. The solvent content of the final product is very low (below 100 ppm).

[0159] Last but not least, the present invention relates to two particularly preferred embodiments as follows:

[0160] 1. A method for producing sterols, the method comprising:

[0161] (a) Providing an oil distillation residue that contains sterol esters and partial glycerides;

[0162] (b) Transesterifying the partial glycerides with a lower alcohol in the presence of a basic catalyst to form fatty acid alkyl esters and glycerol;

[0163] (c) Removing the excess lower alcohol, basic catalyst, glycerol, and fatty acid alkyl esters, each of the four components being removed in a single step or as two, three, or more steps, either in parallel or sequentially, to form a product containing sterol esters; and

[0164] (d) Refer to previous step (d);

[0165] (e) Transesterifying the sterol esters with a lower alcohol in the presence of a basic catalyst at a temperature of 25 °C to 90 °C and atmospheric pressure to form free sterols;

[0166] (f) Refer to previous step (f);

[0167] (g) Optionally adding water to the product resulting from step (e), or - if step (f) is applied - to the product resulting from step (f), in an amount of 15 to 25% based on the mass of the total batch, to set the mass ratio of sterol:fatty acid alkyl ester (calculated as FME):lower alcohol (calculated as methanol):water to be substantially 1:2.5 - 3:2.2 - 2.5:0.8 - 1.2. During the addition of water, the reaction mixture is homogenized by mixing to form an emulsion / suspension;

[0168] (h) Crystallizing the sterols in the mixture obtained from step (e), (f), or (g) under conditions of optional mixing;

[0169] (i) Removing the sterols from the mother liquor by physical means;

[0170] (j) Washing the sterol crystals obtained in step (i) individually or jointly with at least one solvent, where the solvent is an azeotrope of a protic polar solvent and an aprotic polar solvent, where the protic polar solvent is selected from the group consisting of water, ethanol, methanol, isopropanol, and the aprotic polar solvent is selected from the group consisting of ethyl acetate, methyl ethyl ketone, and methyl acetate;

[0171] (k) Optionally drying the obtained sterol crystals to remove the solvent;

[0172] (l) Optionally, by hot forming, such as granulation (e.g., spray granulation), rolling (clandering), pressing, melting, and spraying (drying), the sterol crystals are melted, dried, and granulated;

[0173] (m) Optionally, by redissolving the sterol in a lower alcohol between steps (j) and (k), steps (h) to (j) are repeated.

[0174] 2. A method for producing sterol, the method comprising:

[0175] (a) Providing an oil distillation residue that contains sterol esters and partial glycerides;

[0176] (b) Transesterifying the partial glycerides with a lower alcohol in the presence of a basic catalyst to form fatty acid alkyl esters and glycerol;

[0177] (c) Removing the excess lower alcohol, basic catalyst, glycerol, and fatty acid alkyl esters, each of the four components being removed in a single step or as two, three, or more steps, either in parallel or sequentially, to form a product containing sterol esters; and

[0178] (d) Refer to the previous step (d);

[0179] (e) Transesterifying the sterol esters with a lower alcohol in the presence of a basic catalyst at a temperature of 90 °C to 145 °C, more particularly 120 °C to 130 °C, for 4 to 10 hours, and more particularly for 5 to 8 hours, at a pressure of 2 to 10 bar;

[0180] (f) Refer to the previous step (f);

[0181] (g) Optionally adding water to the product produced in step (e), or - if step (f) is applied - to the product produced in step (f), in an amount of 15 to 25% based on the total batch mass, to set the mass ratio of sterol:fatty acid alkyl ester (calculated as FME):lower alcohol (calculated as methanol):water to be substantially 1:2.5 - 3:2.2 - 2.5:0.8 - 1.2. During the addition of water, the reaction mixture is homogenized by mixing to form an emulsion / suspension;

[0182] (h) Crystallizing the sterol in the mixture obtained from step (e), (f), or (g) under optionally mixed conditions;

[0183] (i) Removing the sterol from the mother liquor by physical means;

[0184] (j) Wash the sterol crystals obtained in step (i) individually or jointly with at least one solvent, wherein the solvent is an azeotrope of a protic polar solvent and an aprotic polar solvent, wherein the protic polar solvent is selected from the group consisting of water, ethanol, methanol, isopropyl alcohol, and the aprotic polar solvent is selected from the group consisting of ethyl acetate, methyl ethyl ketone, and methyl acetate;

[0185] (k) Optionally dry the obtained sterol crystals to remove the solvent;

[0186] (l) Optionally subject the sterol crystals to melt drying and particle formation by hot forming, such as granulation (e.g., spray granulation), rolling, pressing, melting, and spraying (drying);

[0187] (m) Optionally repeat steps (h) to (j) by redissolving the sterol in a lower alcohol between steps (j) and (k). Example:

[0188] The presently claimed invention will now be described in more detail by reference to the following specific, non-limiting examples.

[0189] Example 1:

[0190] At 122 °C, in the presence of 37.5 g (= 1.5%) of sodium methoxide, 2.5 kg of the distillation residue from transesterified palm kernel oil (having a residual acid value of 3.5) was transesterified with 375 g (= 15%) of methanol. A pressure of 5 bar was established. After 8 minutes, the reaction mixture was discharged into a glass flask, and 58 g (= 2.3%) of a 50% citric acid solution was introduced therein. 80% excess methanol was "flashed out" while simultaneously neutralizing the catalyst. The mixture was cooled to 75 °C.

[0191] After stirring for 15 minutes, 250 g of water was added, and stirring was continued at 75 °C for 60 minutes. Then the mixture was cooled, and the aqueous phase was discharged. The organic phase was washed twice with 250 g of water.

[0192] To remove FME, the product was evaporated in a thin-film evaporator at 180 °C and 3 mbar. The feed was run at 90 °C. The temperature of the condenser was 50 °C. For a throughput of 150 g / min, a distillate-to-bottoms product ratio of 75:25 was obtained. Based on the distillation residue from transesterified palm kernel oil, the methyl ester yield was thus 70%.

[0193] Then, at 120 °C, 130 g of the bottom product was transesterified by adding 65 g (= 50%) of methanol and 2.6 g (= 2.0%) of sodium methoxide. After 5 h, the reaction was stopped by adding 4.0 g (= 3.1%) of 50% citric acid, and the excess methanol was flashed out. The mixture was cooled to 75 °C.

[0194] After stirring for 15 min, 13 g of water was added to the reaction mixture, and after stirring again for 30 min at 75 °C, 110 g of FME was added to promote phase separation. Phase separation occurred at 60 °C. After the aqueous phase separated, the organic phase was washed with 39 g of water. Then:

[0195] a) The organic phase was heated to 65 °C, then the stirrer and heater were turned off. After 60 minutes, the mixture was cooled to 25 °C and as many crystals as possible were obtained, or

[0196] b) The organic phase was heated to 65 °C and then poured into an unheated container. After 25 minutes, the mixture was cooled to below 30 °C and as many crystals as possible were obtained.

[0197] The crystals obtained in Examples 1a) and 1b) were washed with a suitable solvent. After drying, sterols were obtained in a yield of 15.5 g, equivalent to 42.7%, based on the total sterol content of the distillation residue of the transesterified palm kernel oil. The sterol concentration in the final product was >95%.

[0198] Example 2:

[0199] The procedure described in Example 1 was repeated up to and including the transesterification of the sterol esters. In the subsequent washing step, in addition to 110 g of FME, 20% of the mother liquor obtained in Example 1b) was added to the mixture. All other steps were carried out as in Example 1 and crystallization was carried out as in Example 1b).

[0200] By recycling 20% of the mother liquor, the sterol yield increased to 19 g, thus reaching 52.3%, based on the total sterol content of the distillation residue from the transesterified palm kernel oil. The sterol concentration in the final product was >95%.

[0201] Example 3:

[0202] As the raw material, rapeseed methyl ester distillation residue with an unsaponifiable matter content of 20 to 25 wt% was selected as the starting material.

[0203] To convert the remaining glycerides in the residue into methyl esters, transesterification was carried out with methanol (as the reactant) and sodium methoxide (as the catalyst) at 80 °C and 2.5 bar for 10 minutes, followed by removal of the resulting glycerol. Then the transesterification and glycerol removal (so-called methanol removal) were repeated before removing the excess methanol and then glycerol was removed again. Finally, the methyl esters formed during the transesterification were removed by a distillation method.

[0204] By the method described above, the unsaponifiable matter in the residue was concentrated to about 45 - 50 wt%.

[0205] For the purification of the concentrated residue, i.e., to improve color, reduce soap content and adsorb trace metals, treatment is carried out at 80 °C with Trisyl (an activated earth available from Grace, specifically Silica, 4030Silica, CP2-7887Silica) for 2 hours, followed by removal of Trisyl by filtration.

[0206] To convert the sterol esters in the concentrated residue to free sterols, another transesterification is carried out at 60 °C to 65 °C and atmospheric pressure with methanol (as the reactant) and sodium methoxide (as the catalyst) for 6 to 7 hours.

[0207] Subsequently, the reaction mixture is slowly cooled to 25 - 30 °C in an Armstrong crystallizer (available from Armstrong), whereby crystallization of the sterols takes place, and the reaction mixture additionally contains 100 wt% methanol based on the content of sterols.

[0208] After crystallization is complete, the crystals are filtered out, washed with pure methanol to remove FME, and dried to constant weight.

[0209] Example 4 - Purification of sterol crystals:

[0210] The sterol crystals obtained by the method described and disclosed in Example 3 are subjected to the following purification steps.

[0211] After crystallization is completed according to Example 3 and under nitrogen (up to 2 bar), the crystals are filtered out, washed with pure methanol to remove FME, and further washed with the following solvents:

[0212] - ethyl acetate and its azeotrope with methanol; or

[0213] - methyl ethyl ketone and its azeotrope with methanol; or

[0214] - methyl acetate and its azeotrope with methanol;

[0215] Subsequently, washing is carried out with pure methanol.

[0216] The crystals are further melted and dried to constant weight and granulation is carried out to form granules.

[0217] The results obtained are compared with an experiment in which the crystals are washed with FME and subsequently with pure methanol.

[0218] The results obtained are summarized in Tables 1 - 3 (laboratory scale) and Tables 1a - 3a (industrial scale, e.g., plant scale). In each table, Examples C1 and T1 refer to the same batch of sterols from the same rapeseed methyl ester distillation residue. The same applies to C2 and T2, C3 and T3, and C4 and T4 (if applicable). Therefore, Example C1 must be compared with Example T1, and so on.

[0219] Table 1 - The solvent used is an azeotrope of ethyl acetate and methanol (laboratory scale)

[0220] Experiment Number Solvent for Washing Color Purity Yield C1 1 FME Wash + 3 Methanol Washes 2.1 98.8 73.7 C2 1 FME Wash + 3 Methanol Washes 2.4 96.8 65.6 C3 1 FME Wash + 3 Methanol Washes 4 98.4 58.1 C4 1 FME Wash + 3 Methanol Washes 1 99.6 72 T1 2 Azeotrope Washes of Ethyl Acetate / Methanol + 1 Methanol Wash 1.2 99.5 74.6 T2 2 Azeotrope Washes of Ethyl Acetate / Methanol + 1 Methanol Wash 1.2 98.4 72.6 T3 2 Azeotrope Washes of Ethyl Acetate / Methanol + 1 Methanol Wash 3 100 69.5 T4 2 Azeotrope Washes of Ethyl Acetate / Methanol + 1 Methanol Wash 0.6 99.7 72

[0221] n.d. = not determined

[0222] Table 1a - The solvent used is an azeotrope of ethyl acetate and methanol (industrial scale)

[0223] Experiment Number Solvent for Washing Color Purity Yield C1 1 FME Wash + 3 Methanol Washes 2.7 n.d. 62.5 T1 2 Azeotrope Washes of Ethyl Acetate / Methanol + 1 Methanol Wash 0.7 n.d. 61.2

[0224] n.d. = not determined

[0225] Table 2 - The solvent used is an azeotrope of methyl ethyl ketone and methanol (laboratory scale)

[0226]

[0227]

[0228] n.d. = not determined

[0229] Table 2a - The solvent used is an azeotrope of methyl ethyl ketone and methanol (industrial scale)

[0230] Experiment Number Solvent for Washing Color Purity Yield C1 1 FME Wash + 3 Methanol Washes 1.9 n.d. 59.2 T1 2 Azeotrope Washes of Methyl Ethyl Ketone / Methanol + 1 Methanol Wash 1.2 n.d. 64.9

[0231] n.d. = not determined

[0232] Table 3 - The solvent used is an azeotrope of methyl acetate and methanol (laboratory scale)

[0233] Experiment Number Solvent for Washing Color Purity Yield C1 1 FME Wash + 3 Methanol Washes 4 98.4 58.4 C2 1 FME Wash + 3 Methanol Washes 2.7 99.1 62.6 C3 1 FME Wash + 3 Methanol Washes 3.6 99.1 62.6 C4 1 FME Wash + 3 Methanol Washes 3.0 100 75.1 T1 2 Azeotrope Washes of Methyl Acetate / Methanol + 1 Methanol Wash 3.2 99.3 71.8 T2 2 Azeotrope Washes of Methyl Acetate / Methanol + 1 Methanol Wash 1.2 99.1 74.7 T3 2 Azeotrope Washes of Methyl Acetate / Methanol + 1 Methanol Wash 1.6 99.1 74.7 T4 3 Azeotrope Washes of Methyl Acetate / Methanol 0.5 100 77

[0234] n.d. = not determined

[0235] Table 3a - The solvent used is an azeotrope of methyl acetate and methanol (industrial scale)

[0236] Experiment Number Solvent for Washing Color Purity Yield C1 1 FME Wash + 3 Methanol Washes 2.2 n.d. 62.7 T1 2 Azeotrope Washes of Methyl Acetate / Methanol + 1 Methanol Wash 1.0 n.d. 67.7

[0237] n.d. = not determined

[0238] Conclusion:

[0239] According to Table 1 (laboratory scale), in the cases of T1 to T4, the color of the final sterol product is significantly better compared to the cases of C1 to C4. Compared with the former, the purity is at least slightly better, and for T1 to T4, the yield is at least the same or even better. As can be seen from Table 1a (plant scale), compared with C1, the color of T1 is significantly improved, while the yield remains more or less unchanged.

[0240] According to Table 2 (laboratory scale), the color of the final sterol product, and especially the yield, is significantly better in the cases of T1 to T3 compared to the cases of C1 to C3. Compared with the former, the purity of T1 to T3 is slightly better. As can be seen from Table 2a (plant scale), compared with C1, the color and yield of T1 are improved.

[0241] According to Table 3 (laboratory scale), in the cases of T1 to T4, the yield of the final sterol product, and especially the color, is significantly better compared to the cases of C1 to C4. Compared with the former, for T1 to T4, the purity is at least the same or even slightly better. As can be seen from Table 3a (plant scale), compared with C1, the color and yield of T1 are improved.

[0242] Those skilled in the art will understand that changes can be made to the above embodiments without departing from their broad inventive concept. Therefore, it should be understood that the present invention is not limited to the specific embodiments disclosed, but is intended to cover modifications within the spirit and scope of the presently claimed invention as defined by the appended claims.

Claims

1. A method for producing and purifying sterols, said method at least comprises the following steps: (a) Providing an oil distillate or an oil distillation residue, said distillate or residue containing sterol esters and partial glycerides; (b) Transesterifying said partial glycerides with a C1-4 lower alcohol in the presence of a basic catalyst to form fatty acid alkyl esters and glycerol; (c) At least partially removing the excess of said lower alcohol, said basic catalyst, said glycerol and / or said fatty acid alkyl esters, each of these components being removed in a single step or as two, three or more steps, either in parallel or sequentially, to form a product containing said sterol esters; (d) Subjecting the product resulting from step (c) to a purification step using an adsorbent; (e) Transesterifying the sterol esters in the product resulting from step (d) with a C1-3 lower alcohol in the presence of a basic catalyst to form free sterols; (f) At least partially removing the excess of said lower alcohol, said basic catalyst, said glycerol and / or said fatty acid alkyl esters, each of these components being removed in a single step or as two, three or more steps, either in parallel or sequentially, either alone or in combination; (g) Adding water to the product resulting from step (e) or the product resulting from step (f), adding said water in an amount of 15% to 25% based on the mass of the total batch, to set the mass ratio of sterols: fatty acid alkyl esters calculated as FME: lower alcohol calculated as methanol: water to be substantially 1: 2.5-3: 2.2-2.5: 0.8-1.2, and during the addition of water, homogenizing the reaction mixture by mixing to form an emulsion / suspension; (h) Crystallizing the sterols in the mixture obtained from step (e), (f) or (g); (i) Removing the sterol crystals from the mother liquor by physical means; (j) Washing the sterol crystals obtained in step (i) two or three times separately or jointly with a solvent, wherein said solvent is an azeotropic solvent mixture of at least one protic polar solvent and at least one aprotic polar solvent, wherein said protic polar solvent is selected from ethanol, methanol and isopropanol, and said aprotic polar solvent is selected from ethyl acetate, methyl ethyl ketone and methyl acetate; (k) Optionally drying the sterol crystals to remove said solvent, and (l) Optionally melting, drying and forming granules of the sterol crystals.

2. The method according to claim 1, wherein in step (a) an oil distillation residue derived from vegetable oil is provided.

3. The method according to claim 2, wherein said oil distillation residue contains residues derived from oils selected from soybean oil, sunflower oil, rapeseed oil, HEAR, coconut oil, palm oil, palm kernel oil and mixtures thereof.

4. The method according to claim 3, wherein said oil distillation residue contains residues derived from sunflower oil, rapeseed oil or HEAR.

5. The method according to claim 1, wherein step (b) is applied, and in step (b), the transesterification of the partial glycerides is carried out for a period of 5 to 20 minutes at a temperature of 80°C to 145°C and a pressure of 2 to 10 bar.

6. The method according to claim 5, wherein the transesterification of the partial glycerides is carried out for a period of 8 to 15 minutes at a temperature of 80°C to 100°C and a pressure of 2 to 3 bar.

7. The method according to claim 1, wherein the lower alcohols used in steps (b) and (e) include alcohols selected from the group consisting of methanol, ethanol, and isopropanol.

8. The method according to claim 7, wherein the lower alcohol is methanol.

9. The method according to claim 1, wherein steps (b) and (c) are applied, and in step (c), the removal of the excess lower alcohol is carried out by allowing expansion until the reaction temperature has cooled to a temperature of 65°C to 85°C.

10. The method according to claim 1, wherein the basic catalyst is selected from sodium methoxide, sodium hydroxide, and potassium hydroxide.

11. The method according to claim 1, wherein steps (b) and (c) are applied, and in step (c), the removal of the basic catalyst is carried out by adding an aqueous solution of an acid, precipitating the catalyst, and separating the precipitate.

12. The method according to claim 1, wherein steps (b) and (c) are applied, and in step (c), the fatty acid alkyl ester is removed by distillation.

13. The method according to claim 12, wherein the distillation is carried out at a temperature of 170°C to 200°C and a pressure of 1 to 5 mbar.

14. The method according to claim 1, wherein in step (e), the transesterification of the sterol ester is carried out for a period of 5 to 8 hours at a temperature of 40°C to 70°C and atmospheric pressure.

15. The method according to any one of claims 1 to 14, wherein in step (e), the transesterification of the sterol ester is carried out for a period of 4 to 10 hours at a temperature of 80°C to 145°C and a pressure of 2 to 10 bar.

16. The method according to any one of claims 1 to 14, wherein the method further comprises cooling the emulsion / suspension of step (e), (f), or (g) to a temperature of 15°C to 50°C, thereby crystallizing the sterol in step (h), wherein the first crystals appear at 65°C to 50°C, and when carried out not in one batch but in two batches, wherein the second batch is the filtered mother liquor of the first batch, then the crystals of the first batch appear at 65°C, and the crystals of the second consecutive batch appear at 55°C to 50°C, and then further slowly cooled to 25°C to 35°C to obtain crystallization.

17. The method according to any one of claims 1 to 14, wherein the sterol crystals in step (i) are separated by physical means selected from filtration, centrifugation, and / or decantation from the mother liquor.

18. The method according to any one of claims 1 to 14, wherein in step (j), the protic polar solvent is methanol, and the aprotic polar solvent is selected from ethyl acetate, methyl ethyl ketone, and methyl acetate.

19. The method according to any one of claims 1 to 14, wherein the washing in step (j) further comprises using methanol.

20. The method according to any one of claims 1 to 14, wherein stripping is carried out at a temperature of 150 °C to 170 °C for 1 to 3 hours, thereby drying the sterol in step (k) to remove the solvent.

21. The method according to any one of claims 1 to 14, wherein the particle formation in step (l) is accomplished by granulation under liquid nitrogen.

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