Production of sterols from tall oil pitch

Abstract

The present invention describes a method for treatment of a stream comprising tall oil pitch (TOP) for the production of at least a stream comprising sterols, said method comprising: - performing a hydrolysis step in a reactor for breaking ester bonds in compounds of the tall oil pitch (TOP), for the production of a hydrolyzed tall oil pitch (TOP) stream; - performing a separation step on the hydrolyzed tall oil pitch (TOP) stream after the hydrolysis step, as an intermediate treatment before the reactive distillation step, for removal of part of the water content from the hydrolyzed tall oil pitch (TOP) stream, wherein the separation step is performed at a lower pressure than the hydrolysis step; - performing a reactive distillation step of the hydrolyzed tall oil pitch (TOP) stream in a column after the separation step; and - producing a stream rich in sterols from the column.

Description

[0001] PRODUCTION OF STEROLS FROM TALL OIL PITCH

[0002] Field of the invention

[0003] The present invention relates to a method and system for producing sterols from tall oil pitch. Moreover, the present invention also relates to a sterol fraction obtainable by the method according to the present invention.

[0004] Summary of the invention

[0005] The present invention is directed to a method for treatment of a stream comprising tall oil pitch (TOP) for the production of at least a stream comprising sterols, said method comprising:

[0006] - performing a hydrolysis step in a reactor for breaking ester bonds in compounds of the tall oil pitch (TOP), for the production of a hydrolyzed tall oil pitch (TOP) stream;

[0007] - performing a separation step on the hydrolyzed tall oil pitch (TOP) stream after the hydrolysis step, as an intermediate treatment before the reactive distillation step, for removal of part of the water content from the hydrolyzed tall oil pitch (TOP) stream, wherein the separation step is performed at a lower pressure than the hydrolysis step;

[0008] - performing a reactive distillation step of the hydrolyzed tall oil pitch (TOP) stream in a column after the separation step; and

[0009] - producing a stream rich in sterols from the column.

[0010] There are other hydrolysis methods in the field of tall oil pitch processing. For instance, in FI118007 there is disclosed a method for separating sterols from a pitch product of a tall oil, wherein the method comprises mixing the pitch with water, homogenization and hydrolysis at 150- 300°C and under increased pressure to retain water in the liquid phase, recovering of a homogeneous mixture, separation and recovery of sterols. The method according to the present invention differs from the method according to FI118007 in at least that the separation step for water removal is performed at a lower pressure than the hydrolysis step, which is not the case in the method disclosed in FI118007. Performing the separation step for the water removal at lower pressure relative to hydrolysis conditions (i) avoids the use of expensive pressurized separator(s) as in FI118007, (ii) avoids problems related to formation av stable emulsions and (iii) provides water stream (flashed and condensed) which is suitable for direct re-use during hydrolysis whereas the water phase according to FI118007 contains substantial amount of free fatty- and rosin acids (3-7%) which are soluble in the water at these conditions thus implying additional separation step(s) before re-use.

[0011] Moreover, the method of FI118007 does not comprise a reactive distillation step such as the method according to the present invention. The use of steam distillation within this step is advantageous over the method disclosed in FI118007 as the conditions, steam presence, prevents the recombination of hydrolyzed TOP components as well as provides additional chance for any unreacted ester entity to be hydrolyzed to its individual parts (locally the water is in the large molar excess (steam) relative to any unreacted ester entity i.e. conditions favorable for hydrolysis). In contrast, the separation according to the method disclosed in FI118007 is performed on hydrolyzed TOP at high temperatures and low pressures i.e., conditions such as high reaction rates and product removal (water) that favor esterification reactions (recombination of hydrolyzed TOP components) instead. Thus, it can be said that the overall effect of separation means employed in accordance with the method of present invention is not only the effective separation but also the increased yield of valuable components previously lost as esters between sterols and / or other alcohols and fatty acids. In line with the above, the method according to the present invention provides an optimization of the removal of water first and then separation of fatty acids during the reactive distillation step. Moreover, the present invention provides a flash procedure as explained above.

[0012] Moreover, if there is an interest in measuring that ester bonds are broken according to the above, one may use saponification value, acid value and the difference thereof before and after the hydrolysis step. This may provide a value of the esterification value, i.e. the “de-esterification” according to the present invention.

[0013] Suitably, the method according to the present invention ensures a conversion level of at least 50%, preferably at least 60%, more preferably at least 70% of the esters contained in the mixture.

[0014] Specific embodiments of the invention

[0015] Below some specific embodiments of the present invention are provided and discussed further.

[0016] According to one embodiment, the temperature in the reactor for the hydrolysis step is held in a range of 230 - 290°C, preferably in a range of 260 - 290°C. This temperature is optimal to ensure a balance between conversion and degradation.

[0017] As mentioned above, according to the present invention, a separation step is performed on the hydrolyzed tall oil pitch (TOP) stream after the hydrolysis step, as an intermediate treatment before the reactive distillation step, for removal of part of the water content from the hydrolyzed tall oil pitch (TOP) stream. As may be understood from the above and below, the method according to the present invention is directed to removal a large part of the water content in the tall oil pitch (TOP), however still keeping a small part of water content, which is prohibiting re-combination of components comprising the original esters. Therefore, according to one embodiment, the separation step is performed in a flash column, preferably by lowering the pressure of the hydrolyzed tall oil pitch (TOP) stream, more preferably for removal of part of the water content from the hydrolyzed tall oil pitch (TOP) stream so that at least 1 wt.% water remains in the hydrolyzed tall oil pitch (TOP) stream.

[0018] Moreover, according to yet another embodiment, the method also comprises a separation step in the column for the production of stream rich in sterols in a comparatively lower part relative to the feed point of entry of the column and a stream rich in fuel compatible components in a comparatively upper part relative to the feed point of entry of the column. As an example, the expression “fuel compatible components” may relate to either a fatty acid rich fraction or fraction substantially containing components with molecular weight less than 350 g / mol. Furthermore, a stream rich in fuel compatible components may also be seen as a fraction comprising components having a comparable high fuel value when considering all components in the stream going into the column.

[0019] Regarding the expressions “...lower and upper parts relative to feed point of entry of the column...” it can be said that the specific design features are typical for those known in the art. For example, the design features incorporated “...lower part relative to feed point of entry of the column...” have typical functions such as ways to supply energy, providing large surface to decrease the diffusion path (more effective striping), etc. features known to promote the lighter components to be vaporized and allowed to move upwards thus ensuring bottom stream enriched in heavier components. In contrast, the design features also known in the art related to the “...upper part relative to the feed point of entry of the column...” are such that provide condensing, refluxing, etc. all features that aim to define the composition of fraction leaving the upper part of the column e.g. ensuring the presence of only minimum amounts of heavy components.

[0020] According to one specific embodiment, the reactive distillation step is a steam distillation step. The use of steam in this case has several functions and / or advantages such as not only preventing the recombination of constituents of the hydrolyzed esters but also increases the chance for additional hydrolysis of unreacted esters. The superheated steam is fed into the column in the comparatively lower part relative to the feed point of entry of the column under the so-called stripping section. Along the heigh within this section, the hydrolyzed TOP is continuously stripped of components with molecular weight less than 350 g / mol which advance upwards within the column. Furthermore, the material within this section is at temperatures comparable to the temperatures employed within the hydrolysis step and as already concentrated in sterols and their esters is meeting superheated steam (water) in large local excess, where both conditions i.e. , sufficient temperature and adequate concentrations promote additional ester hydrolysis. Thus, the steam provides an effective separation and transportation of fuel compatible components towards the upper part relative to the feed point of entry of the column where these can be collected but also provides a bottom stream at the comparatively lower part relative to the feed point of entry of the column rich in sterols and more specifically free sterols.

[0021] Moreover, according to yet another embodiment, the hydrolysis step is a non-catalytic hydrolysis step. This is also a difference of the method according to the present invention when being compared with several known hydrolysis methods.

[0022] Furthermore, according to yet another embodiment, the stream rich in sterols produced from the lower part relative to the feed point of entry of the column is further treated by a separation step in one or more of a thin film evaporator, a short path evaporator, or a combination of one or more thin film evaporators and one or more short path evaporators, preferably in a separation step in at least a short path evaporator, more preferably a first separation step in a thin film evaporator for removal of moisture for the production of a dry stream rich in sterols which is further treated in one or more short path evaporators.

[0023] Moreover, according to yet another embodiment, the stream rich in sterols produced from the lower part relative to the feed point of entry of the column is further treated at a temperature of below 260°C.

[0024] The present invention also provides a system arranged for treatment of a stream comprising tall oil pitch (TOP) for the production of at least a stream comprising sterols, said system comprising

[0025] - a hydrolysis unit;

[0026] - a separation unit; and

[0027] - a reactive distillation column, wherein the separation unit is positioned between the hydrolysis unit and the reactive distillation column and connected to the same.

[0028] According to the present invention, the system comprises a hydrolysis unit. The hydrolysis unit is any type of vessel able to provide and ensure the required temperature, pressure and reaction time throughout the hydrolysis. It should be understood that hydrolysis implies a contact between water and TOP streams going into the hydrolysis unit. Moreover, the greater the contact the greater chance for the ester bonds to be broken (hydrolyzed). Thus, effective mixing is provided by any standard processing means ensuring good contact between water and TOP. Typical examples for such process means but not limited to are static and / or dynamic mixers, other physical means such as baffles, trays, packings, etc. Furthermore, the means for providing effective mixing may be upstream the hydrolysis unit and / or are integral part of the unit design thus maintaining the good contact between water and TOP throughout the hydrolysis step.

[0029] According to the present invention, the system comprises a separation unit positioned between the hydrolysis unit and the reactive distillation column and connected to the same. Furthermore, according to one embodiment, the separation unit is a flash column.

[0030] According to yet another embodiment, the reactive distillation column is a steam distillation column. According to one embodiment, the reactive distillation step is a steam distillation step performed in a steam distillation column and wherein at least a part of the steam distillation column is held at a temperature of maximum 260°C, preferably said part of the steam distillation column being held at a temperature of maximum 260°C is positioned at a comparatively lower part relative to the feed point of entry of the steam distillation column.

[0031] Moreover, according to one embodiment, the system comprises at least one post-treatment unit which is connected to the reactive distillation column, wherein said at least one post-treatment unit is one or more of a thin film evaporator, a short path evaporator, or a combination of one or more thin film evaporators and one or more short path evaporators. According to one embodiment, the system comprises a thin-film evaporator connected to the reactive distillation column, for further separation of a stream rich in sterols produced from a lower part relative to the feed point of entry of the reactive distillation column, and wherein the system comprises at least one short path evaporator for further treatment of a stream rich in sterols obtained from the thin-film evaporator, preferably the system comprises at least two short path evaporators connected in series. To arrange a thin-film evaporator first may be of interest to ensure a really dry stream entering a short path evaporator unit.

[0032] According to one embodiment, the system comprises one or more condensers, at least one condenser being connected to the reactive distillation column for receiving at least part of a stream rich in fuel compatible components, said at least one condenser being arranged for recirculating water / steam content as liquid water to a water tank, preferably said at least one condenser is connected to a post-treatment unit for flowing a stream rich in water / steam content from the post-treatment unit to the condenser, said at least one condenser being arranged for recirculating water / steam content as liquid water to a water tank.

[0033] Furthermore, according to one embodiment, the system comprises a condenser connected to a separation unit positioned between the hydrolysis unit and the reactive distillation column, said separation unit preferably being a flash column, which separation unit produces a steam stream and a water depleted hydrolyzed TOP stream, said condenser arranged for recirculating water / steam content as liquid water to a water tank.

[0034] Moreover, according to yet another embodiment, the system comprises one condenser being connected to the reactive distillation column for receiving at least part of a stream rich in fuel compatible components, said at least one condenser also being connected to a post-treatment unit for flowing a stream rich in water / steam content from the post-treatment unit to the condenser and said at least one condenser also being connected to a separation unit positioned between the hydrolysis unit and the reactive distillation column, said separation unit preferably being a flash column, which separation unit produces a steam stream and a water depleted hydrolyzed TOP stream, said at least one condenser being arranged for recirculating water / steam content as liquid water to a water tank.

[0035] As should be understood from the above, the system according to the present invention may comprise one or multiple condensers. In the case of one single condenser, then this condenser is the one being connected to all units mentioned above as possible to be connected to condensers.

[0036] Moreover, according to yet another embodiment, the system comprises a steam generator unit connected to the reactive distillation column, for feeding steam to the reactive distillation column.

[0037] According to one specific embodiment, the reactive distillation column comprises at least two different zones relative to the column height separated by packing means, wherein one upper zone are arranged to feed a stream rich in fuel compatible components from an upper part relative to the feed point of entry of the reactive distillation column and wherein one lower zone is arranged to feed a stream rich in sterols from a lower part relative to the feed point of entry of the reactive distillation column, and wherein the stream rich in fuel compatible components and the stream rich in sterols are arranged to be kept separate from each other. In relation to the expression “stream rich in fuel compatible components”, this is mentioned above.

[0038] Moreover, the present invention also provides a sterol fraction obtainable from tall oil pitch, said sterol fraction comprising at least 70 wt.% sterols from the sum of campsterol, campestanol, beta-sitosterol and sitostanol, preferably said sterol fraction comprises at least 75 wt.% sterols from the sum of campsterol, campestanol, beta-sitosterol and sitostanol.

[0039] According to one embodiment, the sterol fraction is obtainable by a method according to the present invention, and as explained above.

[0040] According to yet another embodiment, the level of betulinol is maximum 1 wt.%, preferably the level of betulinol is maximum 0.5 wt.%, more preferably the level of betulinol is maximum 0.1 wt.%, wherein preferably the level of alpha-sitosterol is maximum 2 wt.%, more preferably the level of alpha-sitosterol is maximum 1 wt.%, most preferably the level of alphasitosterol is maximum 0.5 wt.%.

[0041] Moreover, according to yet another embodiment, the present invention provides a high purity sterol fraction obtainable from tall oil, said high purity sterol fraction comprising a further concentrated sterol fraction as provided above, and comprising at least 95 wt.% sterols from the sum of campsterol, campestanol, beta-sitosterol and sitostanol.

[0042] Detailed description of the drawings and example information

[0043] In figs. 1 -3 there are provided three different method embodiments according to the present invention.

[0044] As can be seen in fig. 1 , a stream of tall oil pitch (TOP) (1 ) is combined with water (2) to provide a combined TOP and water stream (3). This stream 3 is then provided to the hydrolysis reactor (4), from which a hydrolyzed tall oil pitch (TOP) stream is produced. This stream is then introduced to a separation step (5), in this case a flash column (5). Water (flashed and condensed) is separated off (6) and may be recycled to be used as water to be combined with TOP before the hydrolysis. The remaining hydrolyzed tall oil pitch (TOP) stream after separation is then introduced to a reactive steam distillation column (7). From this step (7) there is produced a sterol rich stream (10), a water stream (condensed steam) (8) which may be combined in the recirculation stream for water, and a stream with fuel compatible components (9). The stream rich in sterols (10) is suitably exposed to one or more post-treatment steps (11 ), including separation of water (evaporated and condensed (12)), which may be combined with the water recirculation loop, providing production of a crude wood sterols stream (13) and a stream or remaining TOP (14).

[0045] In fig. 2 there is shown one embodiment in line with the one shown in fig. 1 , however in this case the system also comprises a water tank (15). This water tank is intended to enable for different forms of production alternatives in terms of water addition in to the production line when a water stream (2) is combined with the TOP stream (1 ) to provide said one or more combined TOP and water streams (3).

[0046] In fig. 3 there is provided yet another embodiment of the present invention, similar to the one shown in figs. 1 and 2. In this case a steam generator (20) is used in a system according to the present invention, to provide superheated steam (30), which is used in the reactive steam distillation column (7).

[0047] In relation to the above alternatives, the following may be provided as an example. The tall oil pitch (TOP) (1 ) may contain sterols at different content levels, and the below should just be viewed as an example. In one possible stream of tall oil pitch (TOP) (1 ) the sterol content level is in a range of 10 - 12 wt.%, up to 1 .5 wt.% free sterols. Here it should be noted that the total amount of sterols can be higher depending on the CTO and TOP origin. Water (2) is then added to the CTO to provide a combined TOP and water stream (3). As a maximum up to 30 wt.% water relative to the TOP (1 ) is added. It should be noted that lower concentration levels of water is normally used, e.g. from steryl ester : water = 1 :2 mole up to 30 wt.% or around the same should be seen as a maximum to minimize the risk of a 2-phase system in the combined TOP and water stream (3).

[0048] The temperature in the hydrolysis reactor (4) is held at a range of 230 - 290°C, suitably in range of 260 - 290°C. For this step it is of interest to drive conversion without driving degradation of the sterols. Temperatures above 290°C may be problematic based on increased degradation. The pressure in the hydrolysis reactor depends on the temperature. At suitable temperatures, the pressure may be around 70-80 bars.

[0049] The separation step is performed in a flash column (5) and at a lower pressure than in the hydrolysis step.

[0050] Water (flashed and condensed) is separated off (6) and may be recycled to be used as water to be combined with TOP before the hydrolysis. The remaining hydrolyzed tall oil pitch (TOP) stream after separation is then introduced to a reactive steam distillation column (7) wherein at least a part of the distillation column (7), preferably a lower part thereof, is held at a temperature of maximum 260°C and negative pressure (vacuum pressure levels). From this step (7) there is produced a sterol rich stream (10), a water stream (condensed steam) (8) which may be combined in the recirculation stream for water, and a stream with fuel compatible components (9), said fuel compatible components stream (9) preferably having a total sterol content of maximum 0.1 wt.%. The stream rich in sterols (10), where suitably the sum of components with molecular weight < 350 g / mol is less than 0.5 wt.%, is suitably exposed to one or more post-treatment steps (11 ). One such step is separation of water (evaporated and condensed (12)), which may be combined with the water recirculation loop. The produced crude wood sterols stream (13) preferably has a total sterol content of at least 60 wt.%, more preferably at least 65 wt.%, and most preferably at least 70 wt.%.

Claims

Claims1 . A method for treatment of a stream comprising tall oil pitch (TOP) for the production of at least a stream comprising sterols, said method comprising:- performing a hydrolysis step in a reactor for breaking ester bonds in compounds of the tall oil pitch (TOP), for the production of a hydrolyzed tall oil pitch (TOP) stream;- performing a separation step on the hydrolyzed tall oil pitch (TOP) stream after the hydrolysis step, as an intermediate treatment before the reactive distillation step, for removal of part of the water content from the hydrolyzed tall oil pitch (TOP) stream, wherein the separation step is performed at a lower pressure than the hydrolysis step;- performing a reactive distillation step of the hydrolyzed tall oil pitch (TOP) stream in a column after the separation step; and- producing a stream rich in sterols from the column.

2. The method according to claim 1 , wherein a temperature in the reactor for the hydrolysis step is held in a range of 230 - 290°C, preferably in a range of 260 - 290°C.

3. The method according to claim 1 or 2, wherein the separation step is performed in a flash column, preferably by lowering the pressure of the hydrolyzed tall oil pitch (TOP) stream, more preferably for removal of part of the water content from the hydrolyzed tall oil pitch (TOP) stream so that at least 1 wt.% water is remained in the hydrolyzed tall oil pitch (TOP) stream.

4. The method according to any of claims 1-3, wherein the method also comprises a separation step in the column for the production of a stream rich in sterols in a comparatively lower part relative to the feed point of entry of the column and a stream rich in fuel compatible components in a comparatively upper part relative to the feed point of entry of the column.

5. The method according to any of claims 1-4, wherein the reactive distillation step is a steam distillation step.

6. The method according to any of claims 1-5, wherein the reactive distillation step is a steam distillation step performed in a steam distillation column and wherein at least a part of the steam distillation column is held at a temperature of maximum 260°C, preferably said part of the steam distillation column being held at a temperature of maximum 260°C is positioned at a comparatively lower part relative to the feed point of entry of the steam distillation column.

7. The method according to any of claims 1-6, wherein the hydrolysis step is a non-catalytic hydrolysis step.

8. The method according to any of claims 1-7, wherein the stream rich in sterols produced from the lower part relative to the feed point of entry of the column is further treated by a separation step in one or more of a thin film evaporator, a short path evaporator, or a combination of one or more thin film evaporators and one or more short path evaporators, preferably in a separation step in at least a short path evaporator, more preferably a first separation step in a thin film evaporator for removal of moisture for the production of a dry stream rich in sterols which is further treated in one or more short path evaporators.

9. The method according to any of claims 1-8, wherein the stream rich in sterols produced from the lower part relative to the feed point of entry of the column is further treated at a temperature of below 260°C.

10. A system arranged for treatment of a stream comprising tall oil pitch (TOP) for the production of at least a stream comprising sterols, said system comprising- a hydrolysis unit;- a separation unit; and- a reactive distillation column, wherein the separation unit is positioned between the hydrolysis unit and the reactive distillation column and connected to the same.

11. The system according to claim 10, wherein the reactive distillation column is a steam distillation column.

12. The system according to any of claims 10-11 , wherein the separation unit is a flash column.

13. The system according to any of claims 10-12, wherein the system comprises at least one post-treatment unit which is connected to the reactive distillation column, wherein said at least one post-treatment unit is one or more of a thin film evaporator, a short path evaporator, or a combination of one or more thin film evaporators and one or more short path evaporators.

14. The system according to any of claims 10-13, wherein the system comprises a thin-film evaporator connected to the reactive distillation column, for further separation of a stream rich in sterols produced from a lower part relative to the feed point of entry of the reactive distillation column, and wherein the system comprises at least one short path evaporator for further treatment of a stream rich in sterols obtained from the thin-film evaporator, preferably the system comprises at least two short path evaporators connected in series.

15. The system according to any of claims 10-14, wherein the system comprises one or more condensers, at least one condenser being connected to the reactive distillation column for receiving at least part of a stream rich in fuel compatible components, said at least one condenser being arranged for recirculating water / steam content as liquid water to a water tank, preferablysaid at least one condenser is connected to a post-treatment unit for flowing a stream rich in water / steam content from the post-treatment unit to the condenser, said at least one condenser being arranged for recirculating water / steam content as liquid water to a water tank.

16. The system according to any of claims 10-15, wherein the system comprises a condenser connected to a separation unit positioned between the hydrolysis unit and the reactive distillation column, said separation unit preferably being a flash column, which separation unit produces a steam stream and a water depleted hydrolyzed TOP stream, said condenser arranged for recirculating water / steam content as liquid water to a water tank.

17. The system according to any of claims 10-16, wherein the system comprises one condenser being connected to the reactive distillation column for receiving at least part of a stream rich in fuel compatible components, said at least one condenser also being connected to a post-treatment unit for flowing a stream rich in water / steam content from the post-treatment unit to the condenser and said at least one condenser also being connected to a separation unit positioned between the hydrolysis unit and the reactive distillation column, said separation unit preferably being a flash column, which separation unit produces a steam stream and a water depleted hydrolyzed TOP stream, said at least one condenser being arranged for recirculating water / steam content as liquid water to a water tank.

18. The system according to any of claims 10-17, wherein the system comprises a steam generator unit connected to the reactive distillation column, for feeding steam to the reactive distillation column.

19. The system according to any of claims 10-18, wherein the reactive distillation column comprises at least two different zones relative to the column height separated by packing means, wherein one upper zone are arranged to feed a stream rich in fuel compatible components from an upperpart relative to the feed point of entry of the reactive distillation column and wherein one lower zone is arranged to feed a stream rich in sterols from a lower part relative to the feed point of entry of the reactive distillation column, and wherein the stream rich in fuel compatible components and the stream rich in sterols are arranged to be kept separate from each other.

20. A sterol fraction obtainable from tall oil pitch, said sterol fraction comprising at least 70 wt.% sterols from the sum of campsterol, campestanol, beta-sitosterol and sitostanol, preferably said sterol fraction comprises at least 75 wt.% sterols from the sum of campsterol, campestanol, beta-sitosterol and sitostanol.21 . The sterol fraction according to claim 20, obtainable by a method according to any of claims 1-9.

22. The sterol fraction according to claim 20 or 21 , wherein the level of betulinol is maximum 1 wt.%, preferably the level of betulinol is maximum 0.5 wt.%, more preferably the level of betulinol is maximum 0.1 wt.%, wherein preferably the level of alpha-sitosterol is maximum 2 wt.%, more preferably the level of alpha-sitosterol is maximum 1 wt.%, most preferably the level of alpha-sitosterol is maximum 0.5 wt.%.

23. A high purity sterol fraction obtainable from tall oil, said high purity sterol fraction comprising a further concentrated sterol fraction according to any of claims 20-22, and at least 95 wt.% sterols from the sum of campsterol, campestanol, beta-sitosterol and sitostanol.

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