阅读说明：本技术 用于分离甾醇和富含脂肪酸和树脂酸的馏分的方法 (Process for separating sterols and fractions rich in fatty acids and resin acids ) 是由 维莱·涅米宁 蒂莫·索米宁 萨米·卡特拉萨洛 莱纳·科波宁 亚里·埃克布洛姆 于 2018-06-01 设计创作，主要内容包括：本发明涉及一种用于从妥尔油沥青中回收甾醇和富含脂肪酸和树脂酸的馏分的方法,所述方法包括：a)用碱使该妥尔油沥青皂化,以将该沥青中包括的酯水解成游离醇和呈盐形式的有机酸,b)用矿物酸使该皂化的沥青酸化,以将这些呈盐形式的有机酸转化成游离有机酸并形成有机相和水相；其中以产生pH值至多3.8的水相的量提供矿物酸,c)从该有机相中分离出该pH值至多3.8的水相,d)在薄膜蒸发器中对该有机相进行蒸发分馏,以获得富含脂肪酸和树脂酸的馏出物和富含甾醇的底部馏分,e)对该底部馏分进行蒸发分馏以获得富含甾醇的馏出物,以及f)对该富含甾醇的馏出物中的甾醇进行结晶纯化,其中该方法在步骤c)与步骤d)之间不包括添加碱的步骤。(The present invention relates to a process for the recovery of sterols and a fraction enriched in fatty acids and resin acids from tall oil pitch, said process comprising: a) saponifying the tall oil pitch with a base to hydrolyze esters included in the pitch to free alcohol and organic acids in salt form, b) acidifying the saponified pitch with mineral acids to convert the organic acids in salt form to free organic acids and form an organic phase and an aqueous phase; wherein mineral acid is provided in an amount to produce an aqueous phase having a pH of at most 3.8, c) separating the aqueous phase having a pH of at most 3.8 from the organic phase, d) subjecting the organic phase to evaporative fractionation in a thin film evaporator to obtain a distillate enriched in fatty acids and resin acids and a sterol-enriched bottom fraction, e) subjecting the bottom fraction to evaporative fractionation to obtain a sterol-enriched distillate, and f) subjecting the sterol in the sterol-enriched distillate to crystallization purification, wherein the process does not comprise a step of adding a base between step c) and step d).)

1. A process for recovering sterols and a fraction rich in fatty acids and resin acids from tall oil pitch comprising

a) Saponifying the tall oil pitch with a base to hydrolyze esters included in the pitch to free alcohol and organic acids in salt form,

b) acidifying the saponified pitch with a mineral acid to convert the organic acids in salt form to free organic acids and form an organic phase and an aqueous phase; wherein the mineral acid is provided in an amount to produce an aqueous phase having a pH of at most 3.8,

c) separating the aqueous phase having a pH of at most 3.8 from the organic phase,

d) subjecting the organic phase to evaporative fractionation in a thin film evaporator to obtain a distillate enriched in fatty acids and resin acids and a sterol-enriched bottom fraction,

e) subjecting the bottom fraction to evaporative fractionation to obtain a sterol-enriched distillate, an

f) Crystallizing and purifying the sterol in the sterol-enriched distillate,

wherein the process does not comprise a step of adding a base between step c) and step d).

2. The process according to claim 1, wherein the mineral acid is provided in the acidification in an amount to produce an aqueous phase having a pH value of at most 3.4, preferably at most 3.0, more preferably 1.0-3.0 and most preferably 1.3-3.0.

3. A process according to claim 1 or 2, wherein the sterols in the sterol-enriched distillate are purified by solvent crystallization, preferably the solvent comprises hydrocarbons, alcohols and optionally water, and most preferably the solvent comprises methyl ethyl ketone, methanol and water.

4. The process according to any one of claims 1 to 3, wherein the organic phase is subjected to a pre-treatment step to remove water from the organic phase prior to step d), the pre-treatment step preferably being carried out in a vacuum degasser.

5. The method according to any one of claims 1 to 4, wherein the thin film evaporator in step d) is a wiped film evaporator.

6. Process according to any one of claims 1 to 5, wherein the thin film evaporator in step d) is not equipped with a dephlegmator.

7. The method according to claim 5 or 6, wherein the wiped film evaporator is operated at a temperature in the range of 160 ℃ to 250 ℃, preferably 180 ℃ to 240 ℃ and at a pressure in the range of 10Pa to 1000Pa, preferably 50Pa to 500 Pa.

8. Process according to any one of claims 1 to 7, wherein the evaporative fractionation step d) produces an amount of distillate of at least 10 w-%, preferably at least 15 w-%, more preferably at least 20 w-% and most preferably at least 25 w-% of the amount of organic phase obtained in step c).

9. Process according to any one of claims 1 to 8, wherein the evaporative fractionation of step e) is carried out in a short-path evaporator.

10. The process according to claim 9, wherein the short-path evaporator is operated at a temperature in the range of 220 ℃ to 280 ℃, preferably 230 ℃ to 270 ℃ and at a pressure of 1Pa to 100Pa, preferably 5Pa to 50 Pa.

11. The method according to any one of claims 1 to 10, wherein the saponification step a) is performed in the presence of NaOH and/or KOH and at least 10 w-%, preferably 10 w-% to 100 w-%, more preferably 15 w-% to 60 w-% and most preferably 20 w-% to 55 w-%, water calculated on the weight of the tall oil pitch.

12. Process according to any one of claims 1 to 11, wherein after the saponification step a) the amount of free sterols is at least 90 w-%, preferably at least 95 w-% and most preferably at least 98 w-% of the sterol equivalents.

13. The method according to any one of claims 1 to 12, wherein the tall oil pitch is mixed tall oil pitch.

14. The process according to any one of claims 1 to 13, wherein the distillate from step d) rich in fatty acids and resin acids is recycled to a crude tall oil distillation process to distill fatty acids and resin acids and leave tall oil pitch as bottom fraction.

15. Process according to any one of claims 1 to 13, wherein the distillate enriched in fatty acids and resin acids from step d) is used for the preparation of biodiesel.

Technical Field

The present invention relates to a process for the recovery of sterols and fractions rich in fatty acids and resin acids from tall oil pitch.

Background

Cardiovascular disease is considered one of the most common diseases worldwide, and its occurrence is further increasing. The most important individual risk factor is elevated serum LDL cholesterol levels, and therefore, lowering LDL cholesterol blood concentrations is the most effective single measure for both prevention and effective treatment of cardiovascular disease. Since the early 50 s of the 20 th century, phytosterols (e.g., sitosterol) have been known to lower serum cholesterol levels. Food products rich in phytosterols or derivatives thereof (such as phytostanol esters) are widely available. In addition to the food industry, phytosterols are used, for example, as raw materials for steroids in the pharmaceutical industry and as emulsifiers in the cosmetic industry. Phytosterols are produced commercially from vegetable oil deodorizer distillates and wood-based materials. Fatty acids and resin acids are widely used as raw materials in the chemical industry (e.g., in soaps, detergents, lubricants, emulsifiers, rubbers, coatings, paints, inks, and adhesives).

Crude tall oil is a major by-product in the pulping process, mainly comprising fatty acids, resin acids and unsaponifiables (such as sterol compounds). When crude tall oil is distilled to tall oil, a distillation residue called tall oil pitch is formed. The composition of tall oil pitch varies depending on the source of the wood material and also depending on the pulping process used. Tall oil pitch includes fatty acids, resin acids, sterol compounds, long chain alcohols, terpene compounds and undefined degraded and/or polymerized molecules resulting from these components, as well as other wood extracted materials. Both sterols and long chain alcohols exist in free form and are esterified with fatty acids to form esters. Most of the sterols in tall oil pitch are in the form of fatty acid esters, but some free sterols are also present. The content of free sterols can be, for example, 1 w-%, and the content of esterified sterols is, for example, 12 w-% of the bitumen, calculated as sterol equivalents (i.e., expressed as free sterols). Tall oil pitch is typically burned for energy production or in asphalt, but it can also be used as a source for recovery of valuable components such as sterols, fatty acids and resin acids.

WO 2008/099051 discloses two alternative methods for recovering fatty acids, resin acids and sterols from tall oil pitch. The first method option comprises saponifying tall oil pitch, acidifying the saponified pitch, separating the aqueous phase from the organic phase, subjecting the organic phase to evaporative fractionation to obtain a distillate enriched in sterols, fatty acids and resin acids and subjecting the distillate to evaporative fractionation to obtain a sterol-enriched bottom fraction and a distillate enriched in fatty acids and resin acids and subjecting the sterols in the sterol-enriched bottom fraction to crystallization purification. Acidification of saponified pitch accelerates phase separation but leads to the problem of increased re-esterification of sterols with fatty acids and thus lower yields of sterols and fatty acids. The problem of re-esterification is solved by collecting the fatty acids, resin acids and sterols all in the first distillate minimizing the contact time between the mineral acids (which act as re-esterification catalyst) and the sterols and fatty acids and thereby eliminating the effect of the mineral acid catalyst. However, such distillation is very energy consuming and therefore expensive.

The second process option disclosed in WO 2008/099051 solves the problem of re-esterification by treating the separated organic phase with alkali to break up the excess mineral acid used to acidify the saponified pitch. The alkali treated organic phase is then distilled in a first evaporative fractionation to produce a distillate enriched in fatty acids and resin acids and a sterol-enriched bottoms fraction. The sterol-enriched bottom fraction is then subjected to evaporative fractionation to obtain a further sterol-enriched distillate, and finally this sterol-enriched distillate is subjected to crystallization purification to obtain sterols.

However, there is still a need for an improved process for recovering sterols and fractions rich in fatty acids and resin acids from tall oil pitch.

Disclosure of Invention

The present invention relates to a process for the recovery of sterols and a fraction enriched in fatty acids and resin acids from tall oil pitch, said process comprising

a) Saponifying the tall oil pitch with a base to hydrolyze esters included in the pitch to free alcohol and organic acids in salt form,

b) acidifying the saponified pitch with a mineral acid to convert the organic acids in salt form to free organic acids and form an organic phase and an aqueous phase; wherein the mineral acid is provided in an amount to produce an aqueous phase having a pH of at most 3.8,

c) separating the aqueous phase having a pH of at most 3.8 from the organic phase,

d) subjecting the organic phase to evaporative fractionation in a thin film evaporator to obtain a distillate enriched in fatty acids and resin acids and a sterol-enriched bottom fraction,

e) subjecting the bottom fraction to evaporative fractionation to obtain a sterol-enriched distillate, an

f) Crystallizing and purifying the sterol in the sterol-enriched distillate,

wherein the process does not comprise a step of adding a base between step c) and step d).

Detailed Description

It is therefore an object of the present invention to provide a process for obtaining sterols from tall oil pitch. A fraction enriched in fatty acids and resin acids is also obtained. This can be used for further recovery of fatty acids and resin acids or other valuable fractions of acids. This fraction may also be recycled to the crude tall oil distillation process for distillation of fatty acids and resin acids. In this way, the sterols contained in this fraction can be recycled to the process for recovery. The method according to the invention is suitable for tall oil pitch based on pine wood as well as mixed tall oil pitch based on crude tall oil obtained from e.g. pine wood, spruce and/or birch. Pine pitch is a preferred starting material because the overall process is smoother and the composition of the unsaponifiable material makes it easier to obtain a sterol product that meets the requirements of sterols to be used in food and supplements. In addition, pine pitch produces higher sterol yields. However, the method is also well suited for mixing tall oil pitch.

It has now surprisingly been found that the pre-addition of a base to neutralize the mineral acid used to enhance phase separation before the evaporative fractionation is carried out (option 2 in WO 2008/099051) is not necessary to avoid re-esterification during the evaporative fractionation. It may even seem advantageous to perform the corresponding method without this addition of base.

Thus, the present invention provides a process with faster overall throughput due to the lack of a step of adding a base. There is no need to estimate the amount of base required to be added to the organic phase to neutralize the mineral acid as required by the closest prior known methods. This estimation is time consuming and cumbersome, since the water content of the organic phase also needs to be measured. Since the overall process of separating sterols and fractions rich in fatty and resin acids from tall oil pitch is faster, using the process of the present invention, higher annual yields can be achieved by a simplified process lacking the equipment required for base addition.

The process according to the invention thus eliminates one step of the prior known processes and therefore requires less investment since no equipment for adding the base and subsequent mixing is required. Moreover, the cost of laboratory analysis aimed at estimating the amount of alkali required to neutralize the organic phase is eliminated. Further, the use of chemicals (alkali) is reduced and, therefore, less salt is concentrated in the heavy residue.

An advantage of the present invention is that the process of eliminating the risk of forming an emulsion is further simplified. In the prior known methods, base overload may easily occur due to the challenging task of accurately estimating the amount of base required, and such overload of the base easily leads to partial formation of the emulsion. Breaking up such emulsions will increase processing time and make water removal (drying) more complicated. Emulsion formation can also impair the evaporative fractionation step.

In the present disclosure, "phytosterol (plant sterol)", "phytosterol (phytosterol)", "sterol", and "sterol compound" are used interchangeably. Sterols quantified in the assays in the present disclosure are sitosterol, campesterol, stigmasterol, sitostanol and campestanol. These are the most abundant sterols in tall oil pitch. However, pitch also contains other sterols. Sterols can be in free form (sterol alcohols) or esterified to fatty acids (sterol fatty acid esters). For quantification purposes, the term "sterol equivalents" is used. The term "sterol equivalent" refers to sterols present in free and esterified form, but amounts are expressed as amounts in the free form. Thus, the amount of sterol equivalents corresponds to the total amount of sterols.

Thus, the method according to the present invention comprises saponifying tall oil pitch. This saponification step a) is performed with a base to hydrolyze the esters in tall oil pitch to free alcohols (sterols and long chain alcohols) and organic acids in salt form (fatty acids and resin acids). The base used is preferably an aqueous solution of an alkali metal hydroxide. Preferably, sodium hydroxide or potassium hydroxide or a combination thereof is used. For example, an aqueous solution of 20 w-% sodium hydroxide may be used. Preferably, water is added to tall oil pitch at a level of at least 10 w-%, preferably at a level of 10 w-% to 100 w-%, more preferably at a level of 15 w-% to 60 w-% and most preferably at a level of at least 30 w-%. This amount of water also includes the water in which the added base is dissolved. Thus, in the saponification step, water is present in an amount of at least 10 w-% of the tall oil pitch, preferably 10 w-% to 100 w-%, more preferably 15 w-% to 60 w-% and most preferably 20 w-% to 55 w-%. In the saponification step, the sterol ester is converted to free sterol and fatty acid in salt form. The amount of alkali metal hydroxide is preferably sufficient to provide substantially complete saponification of the sterol ester in the bitumen to free sterols and fatty acids. The amount of alkali metal hydroxide should be at least equal to the amount defined by the saponification number of the pitch. Preferably, the base is added in excess of, for example, 1% to 15% or more preferably in excess of about 7% to 13%. Saponification is typically performed at a temperature of 80 ℃ to 220 ℃, preferably 90 ℃ to 200 ℃, more preferably 95 ℃ to 180 ℃ and most preferably 100 ℃ to 160 ℃. The saponification is preferably performed at a temperature of at most 160 ℃, more preferably at most 150 ℃, still more preferably at most 140 ℃ and most preferably less than 130 ℃. Organic co-solvents such as ethanol, propanol, hexane, heptane or ketones (e.g., methyl ethyl ketone) or mixtures thereof may be used. However, it is preferred not to use a co-solvent, since co-solvents make the saponification step more complicated and more expensive, and the co-solvent needs to be recovered before the subsequent process steps. In order to achieve an overall good yield of resin acids and fatty acids and sterols in the process according to the invention, it is important that the saponification is efficient. Thus, saponification is performed to provide at least 90 w-%, preferably at least 95 w-% and most preferably at least 98 w-% of free sterols in tall oil pitch in sterol equivalents.

The acidification step b) of the saponified tall oil pitch is performed with a mineral acid, such as sulfuric acid or hydrochloric acid, and preferably with sulfuric acid. Typically, an aqueous solution of 30 w-% sulfuric acid may be used, but other concentrations, e.g. 10 w-% to 93 w-%, may also be used. The amount of mineral acid is such that the pH of the aqueous phase is at most 3.8, preferably at most 3.4, more preferably at most 3.0. Preferably, the pH is at least 1.0, more preferably at least 1.3 and most preferably at least 1.4. Thus, a pH of 1.0 to 3.0 is generally very preferred, and 1.3-3.0 is most preferred. After acidification, the temperature of the reaction mixture is maintained below 100 ℃, e.g., 5 to 120 minutes, without stirring, to separate the aqueous and organic phases.

Preferably, the acidification step b) is performed on saponified pitch having at least 90 w-%, preferably at least 95 w-% and most preferably at least 98 w-% of the sterol equivalents present as free sterols. This improves the efficiency of the overall process.

Acidification improves the phase separation step c) by making it faster and more efficient. Preferably, the phase separation is accomplished by allowing the acidified saponified tall oil pitch to stand and settle for at most 120 minutes, more preferably at most 90 minutes, still more preferably at most 60 minutes, even more preferably at most 30 minutes and most preferably 15 minutes. The residual water content of the organic phase after phase separation is generally at most 5 w-%, preferably at most 4 w-%, more preferably at most 3.5 w-%.

Residual water may be removed from the organic phase, for example, by a vacuum degasser to produce a dried organic phase. The phase separation is sufficiently effective to be accomplished by simply allowing the acidified and saponified pitch to settle for a short period of time (e.g., 5 to 120 minutes) and leaving only a low level of residual water in the organic phase. Preferably, the organic phase is subjected to a step for removing residual water from the organic phase (preferably in a vacuum degasser) prior to step d). Most preferably, the drying of the organic phase is carried out as a first step of evaporative fractionation by means of a vacuum degasser.

In the present disclosure, "organic phase" means an organic phase containing residual amounts of water, i.e. the material that is fed to the drying step (i.e. to the evaporation unit).

The evaporative fractionation steps d) and e) according to the present invention are preferably carried out by continuously feeding the bottom fraction of the first evaporator to the second evaporator.

In the first evaporative fractionation step d), fatty acids and resin acids are distilled. This evaporative fractionation may be performed by using a thin film evaporator without a dephlegmator, i.e., the thin film evaporator is not equipped with a dephlegmator. In this apparatus, the distillate obtained from the thin film evaporator is not fed to the partial condenser. Thus, the fraction or part of the fraction enriched in fatty acids and resin acids is preferably not recycled to the thin film evaporator.

Alternatively and preferably, the thin film evaporator is a Wiped Film Evaporator (WFE).

The wiped film evaporator is operated at a temperature preferably in the range of 160 ℃ to 250 ℃, more preferably 180 ℃ to 240 ℃ and at a pressure preferably in the range of 10Pa to 1000Pa, more preferably 50Pa to 500 Pa.

The distillate enriched in fatty acids and resin acids obtained in the first thin film evaporation, also referred to herein as the fatty acid and resin acid enriched fraction, may be further distilled to obtain fatty acids and resin acids or valuable fractions of these organic acids, respectively.

It has now been realized that the distillate from step d) enriched in fatty acids and resin acids may preferably be recycled to the crude tall oil distillation process for distilling the fatty acids and resin acids and leaving the tall oil pitch as bottom fraction. This is a convenient way of utilizing the fatty acids and resin acids comprised in the distillate fraction enriched in fatty acids and resin acids obtained in step d) of the process of the present invention. At the same time, the sterols contained in the distillate of step d) can also be recycled into the process of the invention by using the obtained tall oil pitch as starting material or as part of the starting material in the process of the invention. In this way, overall recovery of sterols from bitumen is more efficient.

Preferably, the fraction enriched in fatty acids and rosin acids can be used for the production of biodiesel.

Introducing the sterol-enriched bottom fraction obtained in step d) into a second evaporative fractionation step e). The second evaporative fractionation is preferably performed in a thin film evaporator to distill the sterols and leave heavy components in the bottom fraction. The second thin film evaporator is preferably a Short Path Evaporator (SPE). The short-path evaporator is preferably operated at a temperature in the range of 220 ℃ to 280 ℃, more preferably 230 ℃ to 270 ℃ and at a pressure in the range of 1Pa to 100Pa, more preferably 5Pa to 50 Pa.

It has been recognized that in order to obtain a high sterol concentration in the sterol-enriched distillate obtained in the second distillation, a considerable amount of distillate is produced in the second evaporative fractionation. Thus, the evaporative fractionation step d) is performed to produce a distillate in an amount of at least 10 w-%, preferably at least 15 w-%, more preferably at least 20 w-% and most preferably at least 25 w-% of the amount of the organic phase obtained in step c).

It is also surprisingly noted that the most preferred way of performing steps d) and e) in the process of the invention is to use a wiped film evaporator in step d) and a short path evaporator in step e). The removal of residual water from the organic phase is then preferably effected by means of a vacuum degasser before the wiped-film evaporator.

After evaporative fractionation, the sterols in the distillate are purified by using conventional crystallization methods (step f) of the process of the invention), such as solvent crystallization, to obtain a sterol blend consisting essentially of 4-desmethyl sterols and limited amounts of other sterol compounds. Preferably, the resulting sterol product should meet the regulatory requirements set by the main jurisdictions (such as in the EU) for pine/wood-based sterol blends. Preferably, the solvent comprises a hydrocarbon, an alcohol and optionally water. More preferably, the solvent comprises methyl ethyl ketone, methanol and water. The crystallization purification is preferably performed using two crystallizations. One or two washing steps may also be included in the purification. The purification by crystallization can be carried out according to any of the existing known methods.

Surprisingly, the method according to the invention is very suitable for using mixed tall oil pitch as starting material.

An additional benefit of this process is that sterols are preferably more efficiently concentrated in the sterol-enriched distillate than the corresponding fractions obtained from acidified/neutralized saponified pitch in prior known processes. The high sterol content in the fraction subjected to sterol crystallization is of great value, since thereby an increased sterol yield can be obtained. The sterol content of tall oil pitch derived from pine-based pulp is usually already higher than in pitch from mixed pulp. Thus, when this method is applied to pine pitch, a higher sterol content will be obtained in the sterol-enriched fraction than in the present example.

In the present specification, the amounts given in percent are intended to mean weight percent (w-%), unless otherwise indicated. Sterols quantified in the assays in the present disclosure are sitosterol, campesterol, stigmasterol, sitostanol and campestanol. The analysis was performed by gas chromatography.

The invention will be described in more detail by the following non-limiting examples.

Example 1

2.0kg of tall oil pitch (containing 13.8 w-% sterol equivalents) originating from a pine and birch based mixed pulp was heated to 85 ℃ in an autoclave and 1.0kg of 20% NaOH was added. The reaction mixture was heated to increase the temperature from 85 ℃ to 140 ℃ over a period of 40 minutes. This temperature was maintained for 30 minutes and then the mixture was cooled to 95 ℃ over a period of 50 minutes. Saponification is performed with continuous mixing. Saponification was almost complete because the amount of free sterol measured was 13.6 w-% (corresponding to 99% of the sterol equivalents contained in the starting bitumen). 895g of 30% sulfuric acid was added to the saponified tall oil pitch and the mixture was further mixed for 60 minutes, after which mixing was stopped for 60 minutes to allow the aqueous and organic phases to separate. The aqueous phase was drained (pH 1.6) and 1933g of organic phase were collected. During acidification and phase separation, the temperature was maintained at about 95 ℃. The evaporative fractionation was then performed in a continuous manner using the following arrangement. The organic phase was distilled in a Wiped Film Evaporator (WFE) at 210 ℃ and 100Pa and the bottom fraction from the WFE was distilled in a Short Path Evaporator (SPE) at 240 ℃ and 10 Pa. Fractions were collected during the time the system was operating under steady conditions (fractions were withdrawn at the beginning and end of the distillation). Thus, water and lamp end-ups (small amounts of low-boiling organic compounds) were collected in the cold trap in an amount of 5.2 w-% of the total amount of collected fractions. The WFE distillate fraction accounted for 26.1 w-% of the total amount of collected fractions, and this WFE distillate fraction corresponded to a fraction enriched in fatty acids and resin acids. This distillate fraction contained 2.8 w-% sterols. The sterol-enriched residue was distilled in the SPE to obtain 43.3 w-% sterol-enriched distillate (containing 28.5 w-% sterols) based on the total amount of collected fractions. The bottom fraction (residue) from the SPE distillation (25.4 w-% of the total amount of collected fractions) contained 1.6 w-% sterols (1.5 w-% esterified). The sterol yield in the sterol-enriched SPE distillate fraction was calculated to be 91.6 w-% based on the sterol amount of the fraction.

Example 2: comparative test of base addition to organic phase before thin film evaporation

The reaction was performed as described in example 1, except that the water content of the organic phase (4.2 wt-%) was determined after the aqueous phase was drained off and the pH of the aqueous phase (1.6) was measured to determine the amount of NaOH to be added in order to neutralize the residual sulfuric acid present in the organic phase. This took 90 minutes. 200 μ l of 50% NaOH was then added to the organic phase (generated as disclosed in example 1) and the reaction mixture was mixed for 60 minutes at 95 ℃. The evaporative fractionation apparatus and conditions were maintained the same as in example 1. The WFE distillate fraction accounted for 23.8 w-% of the total amount of collected fractions, and 4.1 w-% of the total amount of collected fractions was collected in the cold trap. The sterol-enriched residue from the WFE was distilled in a Short Path Evaporator (SPE) to obtain a sterol-enriched distillate comprising 45.8 w% of the total amount of collected fractions. The sterol-enriched distillate contained 28.0 w-% sterols. The bottom fraction (26.3 w-% of the total collected fraction) contained 2.1 w-% sterols (1.9 w-% esterified). The sterol yield sterol-enriched distillate was calculated to be 90.6 w-%, based on the sterol amount of the fraction.

Example 3: purification of the sterols obtained in example 1 by crystallization

167g of the SPE distillate produced in example 1 was dissolved by reflux in 176g of a solvent mixture containing 5% water, 38% methanol and 57% methyl ethyl ketone. After dissolution, the sterols were crystallized by cooling to 30 ℃ and held at 30 ℃ overnight. The crystals were filtered through a pressure filter and washed at 25 ℃ with a solvent mixture of the same composition as used in the crystallization. The sterol crystals were dried and analyzed. The yield of sterol crystals was 72 w-%, and the product contained 95 w-% sitosterol, campesterol, stigmasterol, sitostanol and campestanol. By applying a second recrystallization step, a sterol product with a higher sterol content can be obtained.

Evaluation of the results from examples 1 and 2:

example 1 is a process according to the invention and example 2 is a corresponding process but with the addition of a base to neutralise the excess mineral acid added in the acidification step to enhance phase separation. As can be seen from the sterol content of the fractions in table 1, sterol esters (1.5 w-% equivalent) were only found in the SPE residue of example 1.

TABLE 1 comparison of the characteristics and results of example 1 and example 2

^*The sterols contained in the sterol-enriched fraction (SPE distillate) of the total sterol content of all fractions are given in w%

^**The amount of sterol equivalents present as esters is calculated from the total weight of the fraction and 2(1.9 w-% equivalents). At the last line of table 1, the amount of esterified sterols (the amount of sterol equivalents present as esters) is calculated from the total weight of the fraction. In example 2, higher amounts of sterol ester were present. Thus, despite the addition of a base intended to reduce re-esterification of sterols, more sterol esters are formed during the process of example 2.

The lesser amounts of water and low boiling organic compounds obtained in the cold trap in example 2 may indicate that some emulsification has occurred and therefore that more water remains in the organic phase. This may also be associated with a higher level of sterol ester formed in example 2.

The sterol yield upon evaporation was slightly better in example 1. The same applies to the sterol content in the SPE distillate in example 1. This means that the method according to the invention gives improved results. However, the main benefit is the simplification of the process by eliminating the addition of base and the problems associated therewith.