Process for separating sterols and a fraction rich in fatty acids and resin acids

Abstract

The present invention relates to a method for recovering sterols and a fraction rich in fatty acids and resin acids from tall oil pitch, the method comprising: a) saponifying the tall oil pitch with an alkali to hydrolyze esters included in the pitch into free alcohols and organic acids in the form of salts, b) acidifying the saponified pitch with a mineral acid to convert the organic acids in the form of salts into 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 with a pH value of at most 3.8, c) separating the aqueous phase with a pH value 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 rich in fatty acids and resin acids and a bottom fraction rich in sterols, e) subjecting the bottom fraction to evaporative fractionation to obtain a distillate rich in sterols, and f) subjecting the sterols in the sterol-rich distillate to crystallization purification, wherein the method does not include a step of adding an alkali between step c) and step d).

Description

Technical Field

[0001] The present invention relates to a process for recovering sterols and a fraction rich in fatty acids and resin acids from tall oil pitch. Background Art

[0002] Cardiovascular disease is considered to be one of the most common diseases worldwide, and its occurrence is further increased. The most important personal risk factor is that serum LDL cholesterol levels rise, and therefore, reducing the blood concentration of LDL cholesterol is the most effective single measure for both prevention and effective treatment of cardiovascular disease. Since the early 1950s, it has been known that plant sterols (for example, sitosterol) can reduce serum cholesterol levels. Food products rich in plant sterols or their derivatives (such as plant stanol esters) are widely available. In addition to the food industry, plant sterols are also used in the pharmaceutical industry, for example, as a raw material for steroids and in the cosmetics industry as an emulsifier. Plant sterols are commercially produced by vegetable oil deodorization distillates and wood-based materials. Fatty acids and resin acids are widely used as raw materials in the chemical industry (for example, in soaps, detergents, lubricants, emulsifiers, rubber, coatings, paints, inks and adhesives).

[0003] Crude tall oil is the main by-product in the pulping process, mainly including fatty acids, resin acids and unsaponifiable matter (such as sterol compounds). When crude tall oil is distilled into tall oil, a distillation residue called tall oil pitch is formed. The composition of tall oil pitch varies according to the source of the wood material and also according to 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 and other wood extracts produced by these components. Sterols and long-chain alcohols are both present in free form and 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, 1w%, and the content of esterified sterols is, for example, 12w% of pitch, calculated as sterol equivalents (i.e., expressed as free sterols). Tall oil pitch is often burned for energy production or used in asphalt, but it can also be used as a source for recovery of valuable components such as sterols, fatty acids, and resin acids.

[0004] WO 2008 / 099051 discloses two alternative methods for recovering fatty acids, resin acids and sterols from tall oil pitch. The first method option includes saponifying tall oil pitch, acidifying the saponified pitch, separating the aqueous phase from the organic phase, evaporating and fractionating the organic phase to obtain a distillate rich in sterols, fatty acids and resin acids and evaporating and fractionating this distillate to obtain a bottom fraction rich in sterols and a distillate rich in fatty acids and resin acids and sterols in the bottom fraction rich in sterols are crystallized and purified. Acidifying the saponified pitch accelerates phase separation, but can lead to an increase in the re-esterification of sterols with fatty acids and therefore a problem of low sterol and fatty acid yields. The problem of re-esterification is solved by minimizing the contact time between mineral acid (which acts as a re-esterification catalyst) and sterols and fatty acids and eliminating the influence of the mineral acid catalyst by collecting fatty acids, resin acids and sterols in the first distillate. However, this distillation is very energy-consuming and therefore expensive.

[0005] The second method option disclosed in WO 2008 / 099051 solves the problem of re-esterification by treating the separated organic phase with alkali to destroy the excess mineral acid used to acidify the saponified bitumen. Then, in a first evaporative fractionation, the alkali-treated organic phase is distilled to produce a distillate rich in fatty acids and resin acids and a bottom fraction rich in sterols. Then, the bottom fraction rich in sterols is evaporated and fractionated to obtain a further distillate rich in sterols, and finally this distillate rich in sterols is subjected to crystallization purification to obtain sterols.

[0006] However, there remains a need for an improved process for recovering sterols and fatty acid and resin acid rich fractions from tall oil pitch. Summary of the invention

[0007] The present invention relates to a process for recovering sterols and a fraction rich in fatty acids and resin acids from tall oil pitch, the process comprising

[0008] a) saponifying the tall oil pitch with an alkali to hydrolyze the esters included in the pitch into free alcohols and organic acids in the form of salts,

[0009] b) acidifying the saponified bitumen with a mineral acid to convert the organic acids in salt form into free organic acids and to form an organic phase and an aqueous phase; wherein the mineral acid is provided in an amount to produce an aqueous phase with a pH value of at most 3.8,

[0010] c) separating the aqueous phase having a pH value of at most 3.8 from the organic phase,

[0011] d) subjecting the organic phase to evaporative fractionation in a thin film evaporator to obtain a distillate rich in fatty acids and resin acids and a bottom fraction rich in sterols,

[0012] e) subjecting the bottom fraction to evaporative fractionation to obtain a sterol-rich distillate, and

[0013] f) purifying the sterols in the sterol-rich distillate by crystallization,

[0014] The method does not include a step of adding a base between step c) and step d). DETAILED DESCRIPTION

[0015] Therefore, the object of the present invention is to provide a method for obtaining sterols from tall oil pitch. A fraction rich in fatty acids and resin acids is also obtained. This can be used to further recover fatty acids and resin acids or other valuable fractions of acids. This fraction can also be recycled to the crude tall oil distillation process for distilling 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 pine-based tall oil pitch and mixed tall oil pitch based on crude tall oil obtained from, for example, pine, spruce and / or birch. Pine pitch is a preferred starting material because the entire processing is smoother and the composition of the unsaponifiable matter makes it easier to obtain a sterol product that meets the requirements of sterols to be used in foods and supplements. In addition, pine pitch produces a higher sterol yield. However, the method is also well suited for mixed tall oil pitch.

[0016] Now surprisingly, it has been found that the preliminary addition of a base to neutralize the mineral acid used to enhance the phase separation before carrying out the evaporative fractionation (option 2 in WO 2008 / 099051) is not necessary to avoid re-esterification during the evaporative fractionation. It even appears to be beneficial to carry out the corresponding method without this addition of a base.

[0017] Thus, the present invention provides a process with faster overall throughput due to the lack of a step to add alkali. There is no need to estimate the amount of alkali required to be added to the organic phase to neutralize the mineral acid as required by the closest prior known process. This estimation is time consuming and cumbersome because the water content of the organic phase also needs to be measured. Since the overall process of separating sterols and a fraction rich in fatty acids and resin acids from tall oil pitch is faster, using the process of the present invention, a higher annual output can be achieved through a simplified process that lacks the equipment required for alkali addition.

[0018] The process according to the invention thus dispenses with one step of the prior known processes and requires less investment since no equipment for adding alkali and subsequent mixing is required. Moreover, the costs of laboratory analysis aimed at estimating the amount of alkali required to neutralize the organic phase are eliminated. Further, the use of chemicals (alkali) is reduced and, therefore, less salt is concentrated in the heavy residue.

[0019] The invention has the advantage of further simplifying the process eliminating the risk of emulsion formation. In prior known processes, alkali overloading may easily occur due to the challenging task for accurately estimating the amount of alkali required, and such overloading of alkali easily leads to partial formation of emulsions. Breaking such emulsions will increase the processing time and make water removal (drying) more complicated. Emulsion formation may also impair the evaporative fractionation step.

[0020] In the present disclosure, "plant sterol", "phytosterol", "sterol" and "sterol compound" are used interchangeably. The sterols quantified in the analysis in the present disclosure are sitosterol, campesterol, stigmasterol, dihydrositosterol 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 alcohol) or esterified to fatty acids (sterol fatty acid esters). For quantification purposes, the term "sterol equivalent" is used. The term "sterol equivalent" refers to sterols that exist in free and esterified form, but the amount is expressed as the amount when in free form. Therefore, the amount of sterol equivalent corresponds to the total amount of sterols.

[0021] Therefore, the method according to the present invention comprises saponifying the tall oil pitch. This saponification step a) is performed with an alkali to hydrolyze the esters in the tall oil pitch into free alcohols (sterols and long-chain alcohols) and organic acids (fatty acids and resin acids) in the form of salts. The alkali 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 20w% sodium hydroxide can be used. Preferably, water is added to the amount of the tall oil pitch at a level of at least 10w%, preferably at a level of 10w% to 100w%, more preferably at a level of 15w% to 60w% and most preferably at a level of at least 30w%. This amount of water also includes water in which the added alkali is dissolved. Therefore, in the saponification step, the water present is at least 10w% of the amount of the tall oil pitch, preferably 10w% to 100w%, more preferably 15w% to 60w% and most preferably 20w% to 55w%. In the saponification step, sterol esters are converted into free sterols and fatty acids in the form of salts. The amount of alkali metal hydroxide is preferably sufficient to provide substantially complete saponification of sterol esters 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 bitumen. Preferably, the added alkali exceeds, for example, 1% to 15% or more preferably exceeds about 7% to 13%. Saponification is generally performed at a temperature of 80°C to 220°C, preferably 90°C to 200°C, more preferably 95°C to 180°C and most preferably 100°C to 160°C. Saponification is preferably performed at a temperature of at most 160°C, more preferably at most 150°C, still more preferably at most 140°C and most preferably less than 130°C. Organic co-solvents such as ethanol, propanol, hexane, heptane or ketones (e.g., methyl ethyl ketone) or mixtures thereof can be used. However, co-solvents are preferably not used because co-solvents make the saponification step more complicated and more expensive, and co-solvents need to be recovered before 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. Therefore, the saponification is performed to provide at least 90w%, preferably at least 95w% and most preferably at least 98w% of free sterols based on the sterol equivalent in the tall oil pitch.

[0022] 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 sulfuric acid is used. An aqueous solution of 30w% sulfuric acid can generally be used, but other concentrations, for example, 10w% to 93w%, can 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. Therefore, 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°C, for example, for 5 to 120 minutes without stirring, to separate the aqueous and organic phases.

[0023] Preferably, the acidification step b) is carried out on a saponified bitumen having at least 90 w%, preferably at least 95 w% and most preferably at least 98 w% of the sterol equivalent present as free sterols. This increases the efficiency of the overall process.

[0024] 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 typically at most 5w%, preferably at most 4w%, more preferably at most 3.5w%.

[0025] Residual water can be removed from the organic phase, for example, by a vacuum degasser to produce a dried organic phase. Phase separation is effective enough to be completed by only allowing the acidified and saponified pitch to rest for a short time (e.g., 5 minutes 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 performed in a vacuum degasser) before step d). Most preferably, the drying of the organic phase is achieved as a first step of evaporative fractionation by a vacuum degasser.

[0026] In the present disclosure, "organic phase" means the organic phase containing residual amounts of water, ie the material that is fed to the drying step, ie to the evaporation unit.

[0027] The evaporative fractionation steps d) and e) according to the present invention are preferably performed by continuously feeding the bottom fraction of the first evaporator into the second evaporator.

[0028] In the first evaporative fractionation step d), fatty acids and resin acids are distilled. This evaporative fractionation can be performed by using a thin film evaporator without a partial condenser, i.e., the thin film evaporator is not equipped with a partial condenser. In this device, the distillate obtained from the thin film evaporator is not fed to the partial condenser. Therefore, the fraction or part of the fraction rich in fatty acids and resin acids is preferably no longer recycled to the thin film evaporator.

[0029] Alternatively and preferably, the thin film evaporator is a wiped film evaporator (WFE).

[0030] The wiped film evaporator is operated at a temperature preferably in the range of 160 to 250°C, more preferably 180 to 240°C and at a pressure preferably in the range of 10 to 1000 Pa, more preferably 50 to 500 Pa.

[0031] The fatty acid- and resin acid-rich distillate obtained in the first thin-film evaporation (also referred to herein as a fatty acid- and resin acid-rich fraction) can be further distilled to obtain fatty acids and resin acids or valuable fractions of these organic acids, respectively.

[0032] It has now been recognized that the distillate rich in fatty acids and resin acids from step d) can preferably be recycled to the crude tall oil distillation process for distillation of fatty acids and resin acids and leaving tall oil pitch as a bottom fraction. This is a convenient way to utilize the fatty acids and resin acids included in the distillate fraction rich 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 to the process of the present invention by using the obtained tall oil pitch as starting material or as part of the starting material in the process of the present invention. In this way, the overall recovery of sterols from pitch is more efficient.

[0033] Preferably, the fraction rich in fatty acids and rosin acids can be used to prepare biodiesel.

[0034] The sterol-rich bottom fraction obtained in step d) is introduced 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 the 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°C to 280°C, more preferably 230°C to 270°C and at a pressure in the range of 1 Pa to 100 Pa, more preferably 5 Pa to 50 Pa.

[0035] It has been recognized that in order to obtain a high sterol concentration in the sterol-rich distillate obtained in the second distillation, a considerable amount of distillate is produced in the second evaporative fractionation. Therefore, 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).

[0036] It is also surprising to note that the most preferred way to carry out steps d) and e) in the process of the present invention is to use a wiped film evaporator in step d) and a short path evaporator in step e). Removal of residual water from the organic phase is then preferably achieved by a vacuum degasser before the wiped film evaporator.

[0037] After evaporative fractionation, the sterols in the distillate are purified by using conventional crystallization methods (step f) of the method of the present invention) (such as solvent crystallization) to obtain a sterol blend consisting mainly of 4-desmethyl sterol and limited amounts of other sterol compounds. Preferably, the sterol product obtained should meet the regulatory requirements set by major 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. Crystallization purification is preferably performed using two crystallizations. One or two washing steps may also be included in the purification. Crystallization purification can be performed according to any existing known method.

[0038] Surprisingly, the process according to the invention is very suitable for using mixed tall oil pitch as starting material.

[0039] An additional benefit of this process is that sterols are preferably concentrated more efficiently in the sterol-rich distillate than in the corresponding fraction obtained from the acidulated / neutralized saponified pitch in the prior known processes. A high sterol content in the fraction subjected to sterol crystallization is of great value, since an increased sterol yield can thereby be obtained. The sterol content of tall oil pitch originating from pine-based pulp is generally already higher than the sterol content in pitch from mixed pulp. Therefore, when this process is applied to pine pitch, a higher sterol content will be obtained in the sterol-rich fraction than shown in the current example.

[0040] In this specification, amounts given in percentages mean weight percent (w%) unless otherwise stated. The sterols quantified in the analysis in the present disclosure are sitosterol, campesterol, stigmasterol, dihydrositosterol and campestanol. The analysis was performed by gas chromatography.

[0041] The present invention will be described in more detail by means of the following non-limiting examples.

[0042] Example 1

[0043] 2.0 kg of tall oil pitch (containing 13.8 w% sterol equivalent) derived from a mixed pulp based on pine and birch was heated to 85 ° C in an autoclave, and 1.0 kg of 20% NaOH was added. The reaction mixture was heated to increase the temperature from 85 ° C to 140 ° C during 40 minutes. This temperature was maintained for 30 minutes, and the mixture was then cooled to 95 ° C during 50 minutes. Saponification was performed with continuous mixing. Saponification was almost complete, as the amount of free sterols measured was 13.6 w% (corresponding to 99% of the sterol equivalent contained in the starting pitch). 895 g 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 separate the aqueous and organic phases. The aqueous phase (pH was 1.6) was discharged, and 1933 g of the organic phase was collected. During acidification and phase separation, the temperature was maintained at about 95 ° C. Then, evaporative fractionation was performed in a continuous manner using the following arrangement. The organic phase was distilled at 210°C and 100 Pa in a wiped film evaporator (WFE), and the bottom fraction from the WFE was distilled at 240°C and 10 Pa in a short path evaporator (SPE). The fractions were collected during the time when the system was operating under stable conditions (the fractions were discharged at the beginning and end of the distillation). Thus, water and lamp end products (a small amount of low-boiling organic compounds) accounting for 5.2w% of the total amount of the collected fractions were collected in the cold trap. The WFE distillate fraction accounted for 26.1w% of the total amount of the collected fractions, and the WFE distillate fraction corresponded to a fraction rich in fatty acids and resin acids. This distillate fraction contained 2.8w% sterols. The sterol-rich residue was distilled in the SPE to obtain a sterol-rich distillate (containing 28.5w% sterols) accounting for 43.3w% of the total amount of the collected fractions. The bottom fraction (residue) from the SPE distillation (25.4w% of the total fractions collected) contained 1.6w% sterols (1.5w% esterified). The sterol yield in the sterol-rich SPE distillate fraction was calculated to be 91.6w% based on the sterol amount of the fraction.

[0044] Example 2: Comparative test of adding base to the organic phase before thin film evaporation

[0045] The reaction was carried out as described in Example 1, except that the water content of the organic phase was determined after the aqueous phase was discharged (4.2 wt-%) and the pH of the aqueous phase was measured (1.6) 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. Then 200 μl of 50% NaOH was added to the organic phase (produced as disclosed in Example 1), and the reaction mixture was mixed at 95° C. for 60 minutes. The evaporative fractionation apparatus and conditions were kept the same as in Example 1. The WFE distillate fraction accounted for 23.8 w% of the total amount of the collected fractions, and 4.1 w% of the total amount of the collected fractions was collected in the cold trap. The sterol-rich residue from the WFE was distilled in a short path evaporator (SPE) to obtain a sterol-rich distillate accounting for 45.8 w% of the total amount of the collected fractions. The sterol-rich distillate contained 28.0 w% sterols. The bottom fraction (26.3 w% of the total amount of fractions collected) contained 2.1 w% sterols (1.9 w% esterified). Based on the sterol amount of the fraction, the sterol yield of the sterol-rich fraction was calculated to be 90.6 w%.

[0046] Example 3: Crystallization purification of sterols obtained in Example 1

[0047] 167g of the SPE distillate produced in Example 1 was dissolved in 176g of a solvent mixture containing 5% water, 38% methanol and 57% methyl ethyl ketone by reflux. After dissolution, the sterol was crystallized by cooling to 30°C and kept overnight at 30°C. The crystals were filtered through a pressure filter and washed with a solvent mixture of the same composition used in the crystallization at 25°C. The sterol crystals were dried and analyzed. The yield of the sterol crystals was 72w%, and the product contained 95w% of sitosterol, campesterol, stigmasterol, dihydrositosterol and campestanol. By applying a second recrystallization step, a sterol product with a higher sterol content can be obtained.

[0048] Evaluation of the results from Example 1 and Example 2:

[0049] Example 1 is a process according to the invention and Example 2 is a corresponding process but with the addition of a base to neutralize 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 were only found in the SPE residue of Example 1 (1.5 w% equiv.).

[0050] Table 1. Comparison of features and results between Example 1 and Example 2

[0051]

[0052] *Sterols in the sterol-rich fraction (SPE distillate) out of the total sterol content in all fractions, given in w%

[0053] ** The amount of sterol equivalents present as esters is calculated based on the total weight of the fraction and 2 (1.9 w% equivalents). At the last row of Table 1, the amount of esterified sterols (the amount of sterol equivalents present as esters) is calculated based on the total weight of the fraction. In Example 2, a higher amount of sterol esters is present. Therefore, despite the addition of a base intended to reduce re-esterification of sterols, more sterol esters are formed during the process of Example 2.

[0054] The lower 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 more water remains in the organic phase. This may also be related to the higher levels of sterol esters formed in Example 2.

[0055] The sterol yield upon evaporation is slightly better in Example 1. The same applies to the sterol content in the SPE distillate in Example 1. This means that the process according to the invention gives improved results. However, the main benefit is the simplification of the process by omitting the addition of base and the problems associated therewith.

Claims

1. A process for recovering sterols and a fraction rich in fatty acids and resin acids from tall oil pitch, the process comprising a) saponifying the tall oil pitch with an alkali to hydrolyze the esters included in the pitch into free alcohols and organic acids in the form of salts, b) acidifying the saponified bitumen with a mineral acid to convert the organic acids in salt form into free organic acids and to form an organic phase and an aqueous phase; wherein the mineral acid is provided in an amount to produce an aqueous phase with a pH value of at most 3.8, c) separating the aqueous phase having a pH value 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 rich in fatty acids and resin acids and a bottom fraction rich in sterols, e) subjecting the bottom fraction to evaporative fractionation to obtain a sterol-rich distillate, and f) purifying the sterols in the sterol-rich distillate by crystallization, The method does not include a step of adding a base between step c) and step d).

2. The method according to claim 1, wherein: The mineral acid is provided in the acidification in an amount that results in an aqueous phase having a pH of at most 3.

4.

3. The method according to claim 1, wherein: The mineral acid is provided in the acidification in an amount that produces an aqueous phase with a pH value of at most 3.

0.

4. The method according to claim 1, wherein: The mineral acid is provided in the acidification in an amount to produce an aqueous phase with a pH of 1.0 to 3.

0.

5. The method according to claim 1, wherein: The mineral acid is provided in the acidification in an amount that produces an aqueous phase with a pH of 1.3 to 3.

0.

6. The method according to claim 1, wherein: The sterols in the sterol-rich distillate are purified by crystallization from solvents including hydrocarbons, alcohols and water.

7. The method according to claim 6, wherein: The solvents include methyl ethyl ketone, methanol and water.

8. The method according to claim 1, wherein: Prior to step d), the organic phase is subjected to a pretreatment step in order to remove water from the organic phase.

9. The method according to claim 8, wherein: This pretreatment step was performed in a vacuum degasser.

10. The method according to claim 1, wherein: The thin film evaporator in step d) is a wiped film evaporator.

11. The method according to claim 1, wherein: The thin-film evaporator in step d) is not equipped with a partial condenser.

12. The method according to claim 10, wherein: The wiped film evaporator is operated at a temperature in the range of 160°C to 250°C and at a pressure in the range of 10 Pa to 1000 Pa.

13. The method according to claim 10, wherein: The wiped film evaporator is operated at a temperature in the range of 180°C to 240°C and at a pressure in the range of 50Pa to 500Pa.

14. The method according to any one of claims 1 to 13, wherein: The evaporative fractionation step d) produces a distillate in an amount of at least 10 w% of the amount of organic phase obtained in step c).

15. The method according to any one of claims 1 to 13, wherein: The evaporative fractionation step d) produces a distillate in an amount of at least 15% by weight of the amount of organic phase obtained in step c).

16. The method according to any one of claims 1 to 13, wherein: The evaporative fractionation step d) produces a distillate in an amount of at least 20 w% of the amount of organic phase obtained in step c).

17. The method according to any one of claims 1 to 13, wherein: The evaporative fractionation step d) produces a distillate in an amount of at least 25 w% of the amount of organic phase obtained in step c).

18. The method according to any one of claims 1 to 13, wherein: This evaporative fractionation of step e) is carried out in a short path evaporator.

19. The method according to claim 18, wherein: The short path evaporator is operated at a temperature in the range of 220°C to 280°C and at a pressure of 1 Pa to 100 Pa.

20. The method according to claim 19, wherein: The short path evaporator is operated at a temperature in the range of 230°C to 270°C and at a pressure of 5 Pa to 50 Pa.

21. The method according to any one of claims 1 to 13, wherein: The saponification step a) is performed in the presence of NaOH and / or KOH and at least 10 w% of water, calculated on the weight of the tall oil pitch.

22. The method according to any one of claims 1 to 13, wherein: The saponification step a) is performed in the presence of NaOH and / or KOH and 15 to 60 w% of water, calculated on the weight of the tall oil pitch.

23. The method according to any one of claims 1 to 13, wherein: The saponification step a) is performed in the presence of NaOH and / or KOH and 20 to 55 w% of water, calculated on the weight of the tall oil pitch.

24. The method according to any one of claims 1 to 13, wherein: After this saponification step a), the amount of free sterols is at least 90 w-% in sterol equivalents.

25. The method according to any one of claims 1 to 13, wherein: After this saponification step a), the amount of free sterols is at least 95 w-% of sterol equivalents.

26. The method according to any one of claims 1 to 13, wherein: After this saponification step a), the amount of free sterols is at least 98% by weight of sterol equivalents.

27. The method according to any one of claims 1 to 13, wherein: The tall oil pitch is a blended tall oil pitch.

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

29. The method according to any one of claims 1 to 13, wherein: The distillate from step d) rich in fatty acids and resin acids is used for the preparation of biodiesel.

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