Note: Descriptions are shown in the official language in which they were submitted.
WO 2021/058647 PROCESS FOR THE PRODUCTION OF STEROLS ANDKIMP24320' 76723
TOCOPHEROLS WITH RECOVERY OF BY-PRODUCTS
Field of invention
The presently claimed invention relates to a method of obtaining phytosterols
and/or
tocopherols from residues of a distillation of the esters of vegetable oils,
preferably from oil
distillation residues from a transesterification of vegetable oils and also to
a method of
purification of a sterol-containing phase, in particular sterol crystals.
Background of the invention
Phytosterols and their esters possess hypocholesterolaemic properties, La
these substances
are capable of lowering the cholesterol level in the blood. Accordingly, they
are used as food
additives, for example for the production of margarine, frying oils, sausages,
ice creams and
the like. The production of sterols and other unsaponifiable constituents,
such as tocopherols
for example, from distillates obtained in the deacidification of vegetable
oils has already been
variously described in the patent literature, cf. EP-A2 0 610 742 (Hoffmann-
LaRoche), GB-A1
2,145,079 (Nisshin Oil Mills Japan) and EP-Al 0 333 472 (Palm Oil Research and
Development
Board).
The main sources of phytosterols are residues from tall oil processing and
distillates from
vegetable oil refining. There are a several prior arts which disclose the
processes for
production of phytosterol based on these raw materials. Furthermore, fatty
acid methyl ester
(FME)as a source for obtaining phytosterols and tocopherols which consists of
distillation
residues from the vegetable oil methyl ester production for the field of use
of biodiesel
hereinafter "fatty acid methyl ester" as "FME"; in the art also known
sometimes named
"FAME") is rarely used Only few methods are known for obtaining phytosterols
and
tocopherols from FME.
While using distillation residues from the vegetable oil methyl ester
production, care should
be taken to ensure that the matrix of concomitant components and contaminants,
which can
have a disruptive effect on the process for obtaining sterols and tocopherols
with regard to
achievable yields and purities, is different from the one in steam
distillates. Besides the useful
products, the distillation residue contains for example phosphatides, coloring
components,
enriched long-chain FMEs and polymerization products from the distillation.
Thus, the
processing of the distillation residues needs to be done differently from the
processing of the
steam distillates.
Accordingly, several attempts have been made to produce phytosterol and/or
tocopherol by
various methods, but there still is a need to produce sterols in high yields
and high purity by
an economical process that would avoid high pressure reactions and, at the
same time, to
utilize residues from the distillation of transesterified oils more
economically.
EP 0 656 894 B1 (Henkel) describes a process for the production of sterols in
which a residue
from the distillation of methyl esters consisting essentially of glycerides,
sterols, sterol esters
and tocopherols is transesterified with methanol in the presence of alkaline
catalysts. After
neutralization of the catalyst, removal of the excess methanol by distillation
and, optionally,
removal of the catalyst by washing, the sterols are crystallized by lowering
the reaction
temperature from about 65 to 20 'C. The thus obtained crystals are washed with
methanol
and water. Unfortunately, the yield of sterols is unsatisfactory.
EP 2 635 592 B1 (Verbio) discloses a method for obtaining phytosterols and
tocopherols using
multi-phase separation systems to isolate the sterol and/or tocopherol.
EP1179535 B1 and EP1179536 B1 (both: BASF) disclose processes for the
production of sterols
using a two-step-transesterification to obtain sterols from vegetable oil
distillates.
Crystallization of the obtained sterols and washing with methanol and FME is
disclosed as
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subsequent process steps in dependent claims. Although in EP1179536 El "methyl
ester" is
disclosed as employed solvent in the examples, the "methyl ester" actually
used in the
examples and disclosed in the description is the FME from the
transesterifications of the
vegetable oil. EP1179535 B1 discloses in its examples the use of "FME"; in
[0036] and [0042]
EP1179535B1 also discloses that the crystals obtained in examples a) and b)
'are washed with
suitable solvents". However, which solvents those actually might be is not
disclosed.
EP1169335 B1 (BASF) discloses a process for the crystallization of sterols
from a specific
mixture of methanol and FME in certain ratios and washing of the obtained
crystals.
Objective of this disclosure is to provide sterols in high yields and "good
color quality". Key
is according to this disclosure the optimum amount and ratio of methanol
during
crystallization and thus the crystallization temperature which is said to lead
to the desired
improvement. The obtained crystals are then washed with FME, which step is
said to further
improve the color quality of the sterol crystals obtained. It is to be noted
that the "methyl
ester" disclosed by EFr1169335 B1 clearly is the "fatty acid ethyl ester", as
both
descriptions/terms are used inter-changingly as can be seen from e.g. [0008],
which mentions
twice the washing of the crystals but uses "methyl ester" at the first
occasion and "FME" on
the second occasion. Claim 1 in the binding German version thus correctly uses
the term
"FME" (whereas claim 1 in the English translation using incorrectly the term
"fatty acid
ester").
However, it is still a challenge to perform a process with improved yield of
sterol without the
use of toxicologically and ecologically unsafe solvents. Further, improving
the color of the
sterol with high purity also remains a challenge.
Summary of the Invention
It has surprisingly been found that the yield, color and purity of the
phytosterol is
significantly influenced by the process used for the downstream processing of
the vegetable
oil distillate and the solvent used for purification. Thus, the conditions of
the process and the
choice of solvent used for the purification process each play - independently -
a significant
role in improving the color of the phytosterol and reducing the amount of
impurities without
compromising on the yield of the final product.
Hence, in one aspect, the presently claimed invention relates generally to the
production of
phytosterols and more particularly to a process for the production of
phytosterols from
residues of the distillation of transesterified oils. In order to be able to
obtain sterols in pure
form, they have to be converted from the esterified to the free state.
Otherwise, they are very
difficult to separate from the components accompanying them. The conversion
into free
sterols may be carried out, for example, by hydrolysis, saponification or
transesterification.
The presently claimed invention is directed to the use of a
transesterification mechanisms.
In an aspect, the presently claimed invention relates to a method of obtaining
phytosterols
and/or tocopherols from residues of a distillation of the esters of vegetable
oils, preferably
from distillation residues from a transesterification of vegetable oils, in
particular from the
vegetable oil-based FME production for the biodiesel field of application,
wherein the
method comprises at least the steps of:
a) a first basic transesterification stage, wherein a reaction of partial
glycerides contained
in the distillation residues is carried out in the presence of a basic
catalyst and methanol,
whereby two phases are formed, wherein one phase comprises to a large extent
glycerin
and the second phase comprises the basic catalyst and unreacted methanol, and
FME,
with thereafter the further optional steps i), ii) and/or iii) of
i) optionally separating methanol
ii) optionally separating FME,
iii) optionally separating the basic catalyst,
b) separating the phase comprising glycerin,
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c) a second basic transesterification stage, wherein a reaction of sterol
esters is carried out,
d) after the second transesterification stage, adding water to a reaction
mixture to form a
multiphase system to crystallize sterols from this mixture,
preferably with the water being added in an amount ranging from 15% to 25%,
based
on the mass of a total batch in order to set a mass ratio of sterol: FMEs:
methanol: water
of substantially 1:2.5-3:2.2-2.5:0.8-12;
during and/or after the addition of water homogenizing the reaction mixture to
an
emulsion/suspension by mixing, whereby a multi-phase system is produced,
e) crystallizing the sterols from the multi-phase system comprising a
methyl ester phase,
an aqueous phase, and the sterols, to form sterol crystals, wherein the
crystallization is
affected by cooling down the mixture to a temperature of below the temperature
of the
second transesterification, in particular to a temperature in the range from 5
C to 35 C,
preferably in the range from 10 C to 30 C, and particularly preferred in the
range from
C to 25 C.;
15 t) separating the multi-phase system into a substantially
sterol (crystals)-containing
phase, a substantially glycerin-containing and a methanol-containing aqueous
phase,
and a tocopherol-containing FME phase,
optionally further crystallizing the remaining sterols from the liquid phase;
El optionally - but preferably being implemented - purifying
the sterol crystals from the
sterol-containing phase using a mixture or an azeotrope of a protic polar
solvent and
an aprotic polar solvent,
i) optionally further drying the sterols,
optionally further purifying the sterols by melt-drying to remove trace
amounts of
solvents within the sterols
k) optionally further subjecting the sterols to a particle-forming process to
obtain sterol
particles,
1) optionally purifying the tocopherol from the tocopherol-
containing phase;
m) optionally purifying the glycerin; and/or
n) optionally purifying the FME.
In an aspect of the presently claimed invention, a two-stage basic catalyzed
transesterification
of a FME distillation residue from the biodiesel production or other oil
transesterification
process, preferably from the biodiesel production, with an intermediate
separation of a
glycerin phase produced in the transesterification is accumulated for
completion of the
glyceride reaction is carried out in the second reaction stage without
methanol- or catalyst-
removal such removal by e.g. flashing, distillation or washing.
In yet another aspect of the presently claimed invention, the glycerin phase
produced after
the first transesterification stage can advantageously be fed directly to a
process, preferably
a distillation process, for obtaining glycerin of desired grade and purity,
such as being
suitable for use in cosmetics and/or pharmaceutical applications.
In another aspect, the presently claimed invention relates to a purification
process, wherein
the color of the final phytosterol product is significantly improved and/or,
preferably and,
the amount of phytosterol ester as an impurity is significantly reduced.
In yet another aspect, the presently claimed invention relates to a
significantly reduced
solvent content in the final phytosterol product.
Detailed description of the invention
Although the presently claimed invention will be described with respect to
particular
embodiments, this description is not to be construed in a limiting sense.
Before describing in detail exemplary embodiments of the presently claimed
invention,
definitions important for understanding the presently claimed invention are
given. As used
in this specification and in the appended claims, the singular forms of "a"
and "an" also
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include the respective plurals unless the context clearly dictates otherwise.
In the context of
the presently claimed invention, the terms "about" and "approximately" denote
an interval of
accuracy that a person skilled in the art will understand to still ensure the
technical effect of
the feature in question. The term typically indicates a deviation from the
indicated numerical
value of 120 %, preferably 15 %, more preferably 10 %, and even more
preferably 5 %. It
is to be understood that the term "comprising" is not limiting. For the
purposes of the
presently claimed invention the term "consisting of" is considered to be a
preferred
embodiment of the term "comprising of'. If hereinafter a group is defined to
comprise at least
a certain number of embodiments, this is meant to also encompass a group which
preferably
consists of these embodiments only.
In case the tern-is "first", "second", "third" or "(a)", "(b)", "(c)", "(d)",
"i", "ii" etc. relate to steps
of a method or use or assay there is no time or time interval coherence
between the steps, i.e.
the steps may be carried out simultaneously or there may be time intervals of
seconds,
minutes, hours, days, weeks, months or even years between such steps, unless
otherwise
indicated in the application as set forth herein above or below. Preferably,
however, the steps
are performed in the numerical or hierarchical order implied by it, i.e. at
first a, then b, then
c etc., first i), then ii), then iii) etc. It is to be under-stood that this
invention is not limited to
the particular methodology, protocols, reagents etc. described herein as these
may vary. It is
also to be understood that the terminology used herein is for the purpose of
describing
particular embodiments only and is not intended to limit the scope of the
presently claimed
invention that will be limited only by the appended claims. Unless defined
otherwise, all
technical and scientific terms used herein have the same meanings as commonly
understood
by one of ordinary skill in the art.
Unless otherwise indicated, the following definitions are set forth to
illustrate and define the
meaning and scope of the various terms used to describe the invention herein
and the
appended claims. These definitions should not be interpreted in the literal
sense as they are
not intended to be general definitions and are relevant only for this
application.
The term "final sterol product" signifies the phytosterol which is obtained
after the
purification steps.
The term "(oil) distillate" encompasses edible vegetable oil distillates
(VODs) which are even
preferred.
The term "(oil) distillation residue" encompasses transesterified oil
distillation residues
which are even preferred. Said transesterified oil distillation residues are
preferably fatty acid
alkyl ester distillation residues, more preferably fatty acid methyl ester
distillation residues
in particular from the production of biodiesel.
The term "partial glycerides" encompasses all combinations of mono-, di-
and/or
triglycerides. In case of oil distillates as starting material, there are only
or nearly only
triglycerides and no mono- and diglycerides, whereas, in case of typical oil
distillation
residues, there are mainly triglycerides and diglycerides and only a few
monoglycerides.
Meaning of the terms that are not defined herein are generally known to a
person skilled in
the art or in the literature.
It is also intended that of course the various embodiments and preferred
options of the
various process steps disclosed herein are to be combined within the actual
complete process,
so that for a specific performance of this overall process for one process
step the general
outline is selected, for another process step within this overall process the
preferred
embodiment and for the again another process step the most preferred option
etc.
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In an embodiment, the presently claimed invention relates to a method of
obtaining
phytosterols and/or tocopherols from residues of a distillation of the esters
of vegetable oils,
preferably from distillation residues from a transesterification of vegetable
oils, in particular
from the vegetable oil-based FME production, specifically for the biodiesel
field of
5 application, with the following embodiments 1 to 4 defining the general
invention, and the
further description below those embodiments disclosing further features and
more details of
the process steps, preferred options and alternatives still encompassed by the
present
invention:
Embodiment 1 of the present invention
Method of obtaining phytosterols and/or tocopherols from residues of a
distillation of the
esters of vegetable oils, preferably from distillation residues from a
transesterification of
vegetable oils, in particular from the vegetable oil-based FME (FAME)
production, more
preferably from the production of biodiesel, wherein the method comprises at
least the steps
of:
a) providing a starting material containing unsaponified matter which is a
residue
from the work-up of vegetable oils, such residue containing sterols and
usually
also tocopherols, wherein the starting material which contains at least 5,
preferably
at least 10, more preferably at least 15, even more preferably at least 20
weight %
of sterols,
b) optionally subjecting the starting material to a concentration step to
increase the
content of sterols compared to the initial content, preferably to a content of
at least
25, more preferably at least 30, even more preferably at least 40 and most
preferably to at least 50 wt.% of sterols in the concentrated residue, by
subjecting
the residue to a transesterification reaction using methanol as solvent and
reactant
and sodium methylate as catalyst, subsequently removing at least part of the
formed glycerine, optionally repeating once or twice said steps of
transesterification and said removal of glycerine, then optionally followed by
removal of at least part of the excessive methanol, and then optionally
removing
further at least part of the remaining glycerine, then followed by removing
the
methyl ester;
c) optionally subjecting the residue of step a) or the concentrated residue of
step b)
to a purification step using adsorbents such as clays, earths and oxides, to
improve
the color, lowering the content of soaps, and/or absorbing trace metals and/or
metal ions, preferably all of those improvements, such purification step being
performed at ambient or elevated temperature, preferably at elevated
temperature, of ambient temperature to about 100 degree Celsius, preferably 60
to
90 C, at suitable treatment duration in the range from 10 minutes to several
hours,
preferably 1 to 10 hours, more preferably 1 to 3 hours, even more preferable
about
2 hours at 75 to 90 C;
d) a first basic transesterification stage, wherein a reaction of partial
glycerides
contained in the distillation residues is carried out in the presence of a
basic
catalyst and methanol, whereby two phases are formed, wherein one phase
comprises to a large extent glycerin and the second phase comprises the basic
catalyst and unreacted methanol, and FME, with thereafter the further optional
steps i), ii) and/or iii) of
i) optionally separating and removing
methanol from the reaction mixture
obtained from the transesterification step;
optionally separating and removing FME from the reaction mixture
obtained from the previous step,
iii) optionally separating and removing the
bask catalyst from the reaction
mixture obtained from the previous step,
e) separating and removing at least partially the phase comprising glycerin
from the
reaction mixture obtained from the previous step,
0 a second basic transesterification stage, wherein a reaction of sterol
esters to free
sterols is carried out, and
i) optionally separating and removing methanol from the reaction mixture
obtained from the transesterification step;
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ii) optionally separating and removing FME from the reaction mixture obtained
from the previous step,
iii) optionally separating and removing the basic catalyst from the reaction
mixture obtained from the previous step,
iv) optionally separating and removing the phase comprising glycerin from the
reaction mixture obtained from the previous step,
g) after the second transesterification stage, adding water to a reaction
mixture to
form a multiphase system to crystallize sterols from this mixture, preferably
with
the water being added in an amount ranging from 15% to 25%, based on the mass
of a total batch in order to set a mass ratio of sterol: FMEs: methanol: water
of
substantially 1:2.5-3:22-2.5:0_8-1.2; during and/or after the addition of
water
homogenizing the reaction mixture to an emulsion/suspension by mixing,
whereby a multi-phase system is produced,
h) crystallizing the sterols from the multi-phase system comprising a methyl
ester
phase, an aqueous phase, and the sterols, to form sterol crystals, wherein the
crystallization is affected by cooling down the mixture to a temperature of
below
the temperature of the second transesterification, in particular to a
temperature in
the range from 5 C to 35 C, preferably in the range from 10 C to 30 C, and
particularly preferred in the range from 15 C to 25 C.;
i) separating the multi-phase system into a substantially sterol (crystals)-
containing
phase, a substantially glycerin-containing and a methanol-containing aqueous
phase, and a tocopherol-containing FME phase,
j) optionally further crystallizing the remaining sterols from the liquid
phase
following the same measures of step g) before, followed by separation of the
crystals following the same measures of step i) before;
k) optionally purifying the sterol crystals obtained in step h) and - if
performed - step
j), either in a separate process step or a combined process step, using a an
organic
solvent, solvent mixture of more than one organic solvents, or an azeotropic
solvent mixture of at least one protic polar solvent and an at least one
aprotic polar
solvent,
1) optionally further drying the sterols;
m) optionally further purifying the sterols by melt-drying to remove trace
amounts of
solvents within the sterol's solids;
n) optionally further subjecting the sterols to a particle-forming process to
obtain
sterol particles,
o) optionally purifying the tocopherol from the tocopherol-containing phase;
p) optionally purifying the glycerin; and/or
q) optionally purifying the FME.
Embodiment 2 of the present invention
A method of obtaining phytosterols and/or tocopherols from residues of a
distillation of
the esters of vegetable oils according to embodiment 1, wherein the method
consists of
the following steps:
a) providing a starting material containing unsaponified matter which is a
residue
from the work-up of vegetable oils, such residue containing sterols and
usually
also tocopherols, wherein the starting material which contains at least 5,
preferably
at least 10, more preferably at least 15, even more preferably at least 20
weight %
of sterols, wherein the residue preferably stems from the production of bio-
diesel
such as the work-up of rapeseed oil being transesterified and worked-up to
produce rapeseed methyl fatty acid ester (RME) and a distillation residue,
b) (step b) of embodiment 1 omitted);
c) (step c) of embodiment 1 being omitted);
d) a first bask transesterification stage, wherein a reaction of partial
glycerides
contained in the distillation residues is carried out in the presence of a
basic
catalyst and methanol, whereby two phases are formed, wherein one phase
comprises to a large extent glycerin and the second phase comprises the basic
catalyst and unreacted methanol, and FME, with thereafter the further optional
steps i), ii) and/or iii) of
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i) optionally separating methanol
ii) optionally separating FME,
iii) optionally separating the basic catalyst,
preferably being the steps i), ii) and iii) being omitted;
e) separating and removing the phase comprising glycerin at least partially,
0 a second basic transesterification stage, wherein
a reaction of sterol esters is carried
out,
g) after the second transesterification stage, adding water to a reaction
mixture to
form a multiphase system to crystallize sterols from this mixture, preferably
with
the water being added in an amount ranging from 15% to 25%, based on the mass
of a total batch in order to set a mass ratio of sterol: FMEs: methanol: water
of
substantially 1:2.5-3:2.2-2.5:0.8-1.2; during and/or after the addition of
water
homogenizing the reaction mixture to an emulsion/suspension by mixing,
whereby a multi-phase system is produced,
h) crystallizing the sterols from the multi-phase system comprising a methyl
ester
phase, an aqueous phase, and the sterols, to form sterol crystals, wherein the
crystallization is affected by cooling down the mixture to a temperature of
below
the temperature of the second transesterification, in particular to a
temperature in
the range from 5QC to 35 C, preferably in the range from 10 C to 30 C, and
particularly preferred in the range from 15 C to 25 C.;
i) separating the multi-phase system into a substantially sterol (crystals)-
containing
phase, a substantially glycerin-containing and a methanol-containing aqueous
phase, and a tocopherol-containing FME phase,
j) optionally further crystallizing the remaining sterols from the liquid
phase
obtained in step h) and/or step i);
k) purifying the sterol crystals obtained in step h) and - if performed - step
j), either
in a separate process step or a combined process step, using a an organic
solvent,
solvent mixture of more than one organic solvents, or an azeotropic solvent
mixture of at least one protic polar solvent and an at least one aprotic polar
solvent,
1) further drying the sterol crystals,
m) optionally further purifying the sterols by melt-drying to remove trace
amounts of
solvents within the sterols, preferably by stream stripping at a temperature
of 130
to 200, preferably 150 C- 170 C, for 1- 3 hours to remove the solvent,
preferably
performing this step,
n) optionally further subjecting the sterols to a particle-forming process to
obtain
sterol particles, preferably subjecting to prilling under liquid nitrogen,
this step
preferably being performed;
o) optionally purifying the tocopherol from the tocopherol-containing phase;
p) optionally purifying the glycerin; and
q) optionally purifying the FME.
Embodiment 3 of the present invention
The process according to embodiment 1 or 2, wherein the residues of a
distillation of the
esters of vegetable oils comprises a residue derived from an oil selected from
the group
consisting of soybean oil, sunflower oil, rapeseed oil, coconut oil, palm oil,
palm kernel oil,
and mixtures thereof.
Embodiment 4 of the present invention
The process according to embodiment 3, wherein the oil distillation residue
comprises a
residue derived from rapeseed oil such as high eruic acid rapeseed oil or
CANOLA oil.
Description of the individual process steps
In the following the further features and more details of the process steps,
preferred options
and alternatives as generally described above in embodiments 1 to 4 are
disclosed and
explained in in more detail in the following:
Step a) - Starting material
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The starting material for the presently claimed process may be obtained using
known
processes as outlined herein above using the known prior art processes.
The starting material thus is a residue from the work-up of vegetable oils,
such residue
containing sterols and usually also tocopherols. Such residue is obtained by
several
esterification and trartsesterifications, treatment with acid etc., all of
which is known in the
art. One such process is the known process to produce biodiesel, i.e. fatty
acid methyl ester.
In the following this residue resulting from such vegetable oil processing and
work-up
including that from the bio-diesel process is meant with the term "residue".
Such residue as a starting material for the present process contains
"unsaponified matter",
such unsaponified matter containing sterols and usually also tocopherols, with
the content
in the starting material being at least 5, preferably at least 10, more
preferably at least 15, even
more preferably at least 20 weight % of sterols, however usually at the lower
end with about
5 to 15wt% sterols.
Such residues may be obtained as outlined herein above, using the known prior
art processes.
Especially suitable residues are such from the work-up of vegetable oils
containing sterols
and usually also tocopherols. These residues are obtained by several
esterification and
transesterifications, treatment with acid etc., all of which is known in the
art. One such known
process is the process to produce biodiesel, i.e. fatty acid methyl ester.
Preferably, the oil distillation residue comprises a residue derived from an
oil selected from
the group consisting of soybean oil, sunflower oil, rapeseed oil, high erucic
acid rapeseed oil
(HEAR), low eruric acid rapeseed oil (CANOLA; CANadian Oil Low eruic Acid),
coconut
oil, palm oil, palm kernel oil, and mixtures thereof, more preferably, the oil
distillation
residue comprises a residue derived from soybean oil, sunflower oil, rapeseed
oil such as
HEAR or CANOLA, even more preferably, the oil distillation residue comprises a
residue
derived from sunflower oil, rapeseed oil, preferably HEAR.
These residues are preferably residues from coconut oil, from palm kernel oil,
from palm oil,
from soybean oil, from sunflower oil, from rapeseed oil such as from HEAR
and/or
CANOLA, more preferably from soybean oil, sunflower oil, rapeseed oil such as
HEAR, even
more preferably from sunflower oil and/or rapeseed oil, and especially HEAR,
with acid
values of 0 to 10, preferably from 0 to 6 and contain mixtures of di- and
triglycerides, FMEs,
sterol esters, wax esters and free sterols, preferably 1 to 7 % by weight
triglycerides, 3 to 15
% by weight diglycerides, 15 to 40 % by weight FMEs, 40 to 50 % by weight, in
particular 42
to 47 % by weight sterol esters, 3 to 4 % by weight wax esters and 3 to 15 %
by weight free
sterols and small quantities of monog,lycerides.
In another embodiment of the presently claimed invention, oil distillates are
used as raw
materials for the production of sterols. These distillates are preferably such
of coconut oil, of
palm kernel oil, of palm oil, of soybean oil, of sunflower oil, of rapeseed
oil such as from
HEAR and/or CANOLA, more preferably of soybean oil, sunflower oil, rapeseed
oil such as
from HEAR, even more preferably of sunflower oil and/or rapeseed oil from
HEAR,
containing 45 to 65 % by weight triglycerides and 35 to 55 % by weight sterol
esters summing
up to 100%.
Step b) - Concentration of residue
To improve the process of the present invention, such residue may be further
concentrated.
The residue as outlined before can be concentrated to a content of
"unsaponified matter" of
about more than 20 such as 35 to 60, preferably 40 to 55 and more preferably
45 to 50 weight
percent of unsaponified matter relative to the total weight of concentrated
residue
(hereinafter "concentrated residue").
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Such concentration can be achieved by submitting the residue as obtained to a
transesterification reaction using methanol as solvent and reactant and sodium
methylate as
catalyst. The aim is to convert remaining glycerides in the residue to methyl
esters. Following
that transesterification, the formed glycerin is to be removed by standard
means, e.g.
decanting. This process of transesterification with following glycerin removal
can be repeated
once or twice or more, but one repetition usually is enough and thus a
preferred embodiment.
Excess methanol is then to be removed, followed by optional further removal of
remaining
glycerin which can form again as separate phase during or after the removal of
methanol.
Then, the formed methyl ester can be removed, by e.g. distillation. This thus
also increases
the yield of the fatty acid methyl ester, i.e. biodiesel.
This process of concentration is an optional process step which can be
employed prior to the
"first transesterification" which then follows to convert the sterols present
in the
"unsaponified matter" in the residue or concentrated residue to purified
sterols which can
then be crystallized and further purified.
Step c) Initial purification step by adsorption
As a further optional process step the residue or - in case the optional step
of concentration
the residue is performed - concentrated residue can be subjected to the
purification using
adsorbents such as clays, earths and oxides. Suitable adsorbents are well-
known, e.g. the
Trisyl-grades (e.g. from the company Grace). This treatment allows for an
improvement of
the color, lowering the content of soaps, and/or absorbing trace metals and/or
metal ions,
preferably all of those improvements, by choosing suitable adsorbents. This
treatment may
be performed at ambient or elevated temperature. In view of the high viscosity
of the residue
or concentrated residue, treatment at elevated temperature is preferable.
Suitable
temperatures are ambient to about 100 degree Celsius, with temperatures of
around 60 to 90
C being preferred mainly to a good combination of viscosity and energy cost
needed.
Suitable treatment duration may be anything from 10 minutes to several hours,
e.g. even 5 to
10 hours. Duration mainly depends on the degree of removal desired and the
amount of
contaminants present in the residue or concentrated residue. Preferably
durations are about
1 to 10 hours, more preferably 1 to 5 hours, even more preferable 1 to 3 hour,
most preferably
about 2 hours at 75 to 90 C.
This process of initial purification by adsorption is an optional process step
which can be
employed prior to the "first transesterification" which then follows to
convert the sterols
present in the "unsaponified matter" in the residue or concentrated residue to
purified sterols
which can then be crystallized and further purified.
Step (d) - First transesterification
In an embodiment of the presently claimed invention, the first
transesterification stage is
carried out with a content of basic catalyst, preferably sodium methylate, but
for example
also sodium hydroxide (NaOH) or potassium hydroxide (KOH) could be used
instead or
together, in the range from 0.1 % to 0.3 %, preferably in the range from 0.18
% to 0.22 % and
with a methanol content in the range from 12 % to 18 %, preferably in the
range from 14 % to
16 % and the second transesterification stage with a content of catalyst in
the range from 0.5
% to 1 %, preferably in the range from 0.6% to 0.8%, and with a methanol
content in the range
from 20% to 38%, preferably in the range from 34% to 36%, wherein the added
quantity of
basic catalyst is standardized to an addition of sodium methylate and, if
appropriate, should
be adapted to the use of other basic catalysts. On the basis of these
necessary additions of
catalyst and methanol, which were very low with regard to known methods, to
the individual
transesterification stages, the method according to the presently claimed
invention can be
operated in a particularly cost-effective and recycling-friendly manner,
because for example
only small quantities of methanol must be supplied for methanol recovery.
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According to a further embodiment of the presently claimed invention, during
the first
transesterification stage, after mixing in of methanol and catalyst, glycerin
is added in an
amount in the range from 0.2% to 7.2%, preferably in the range from 0.5% to
6.0%, and
particularly preferably in the range from 1.0% to 5.5%, in each case based on
the mass of the
5 total batch. By this addition of glycerin to the total batch the later phase
separation is
improved, and contaminants are better discharged in an advantageous manner
into the
heavy glycerin phase.
In an embodiment of the presently claimed invention, the second
transesterification reaction
10 is carried out at a temperature range of 25 C to 150 C
depending on the pressure and time
conditions.
In an embodiment of the presently claimed invention, the first
transesterification stage is
carried out at a temperature in the range from room temperature (e.g. 25 C)
to 100 C,
preferably to 95, more preferably to 90 and even more preferably to 88 C,
preferably in the
range from 40 C to 75 C and particularly preferably in the range from 55 C
to 70 C, such
as at a temperature of 60 to 65 C, and furthermore in particular at normal
pressure. The
reaction may be performed depending on the temperature and pressure chosen
under reflux
or without reflux. When methanol is chosen which is the most favorable alcohol
to be
employed, this means that the reaction is performed at the boiling temperature
of methanol
or slightly below when operating at ambient pressure. By this a good
temperature control
can be implemented. This embodiment of the invention enables an energy-saving
and cost-
efficient performance of the method, because high heating costs are avoided
and the
respective transesterification reactions can be preferably carried out inter
alia at normal
pressure, so that expensive pressurized reactors and complex and expensive
generation and
maintenance of the temperatures and pressures, such as are necessary in the
prior art, can be
omitted. Thus, this embodiment is preferred over the following two embodiments
for this
process step.
However, of course, depending on the duration employed for the
transesterification.s, at
lower temperatures the duration of the reaction has to be prolonged compared
to high
temperatures, as otherwise no satisfying yields are obtainable. Hence, the net
benefit in terms
of energy saving depends on the complete outline of the process, the equipment
employed
and the temperature and duration of the reactions, as a simply reduction in
time leads to
higher reaction temperature (if the yield should stay the same) or lower
yields (if the duration
stays the same).
In an alternative embodiment of the presently claimed invention, the
transesterification
reaction of the partial glycerides is preferably carried out over a period of
5 to 20 minutes and
more particularly 8 to 15 minutes at a temperature of 110 to 160, more
preferably at 115 to
145 C. and more particularly at a temperature of 120 to 130 C at a pressure
of 2 to 10 bar.
Steps i), ii) and iii) of step d) are described in the following section.
Steps i), ii) and iii) of step d) and step e) - Separating the phase
containing glycerin, methanol,
FME and catalyst.
In an embodiment of the presently claimed invention, the glycerin phase may be
preferably
be removed without previous separation of FME, methanol and/or catalyst, more
preferably
the glycerin phase may be removed without previous separation of FME, methanol
and
catalyst.
In one embodiment the glycerin phase is removed from the reaction mixture of
the
transesterification reaction without prior removal of methanol, fatty acid
ester and catalyst.
In an embodiment of the presently claimed invention, the basic catalyst used
according to the
presently claimed invention can be used and recycled without any environmental
or food-
related problems, wherein in an advantageous manner, unlike for example in the
aforesaid
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U.S. Pat. No. 5,424,457, there should be no fear of heavy metal contamination
in the produced
products, in this case phytosterols and/or tocopherols.
In yet another embodiment of the presently claimed invention, the basic
catalyst is optionally
separated from the reaction mixture resulting from the first
transesterification process.
In yet another or economic reasons being preferred embodiment the reaction
mixture
resulting from the first transesterification reaction is submitted to the
following additional
process steps:
i) depletion of methanol by e.g. flashing and/or distillation,
ii) depletion of FME by e.g. flashing and/or distillation,
with the steps i) and ii) being performed either first step i) and then step
ii) or both
steps i) and ii) being performed together or with some overlap, i.e. that step
ii) starts
before step i) is finished, and
iii) removal of the catalyst by e.g. absorption on suitable absorbents such
as
suitable Trisyl-grades (e.g. from Grace) and the like, optionally by adding
suitable acids during or before adding the adsorbent.
In step 3) as part of the presently claimed invention, the glycerin phase,
preferably the
glycerin phase resulting from the reaction mixture after having performed the
further process
steps i), ii) and iii) of previous step d) and only then having separated the
glycerin-phase,
from the first transesterification stage can advantageously be fed directly to
a process for
obtaining glycerin of any desired grade and purity, such process preferably
being a multi-
stage distillation process using typically, known equipment and conditions.
Step (0 Second transesterification
In an embodiment of the presently claimed invention, the second
transesterification reaction
is carried out at a temperature range of 25 C to 150 C depending on the
pressure and time
conditions.
In an embodiment of the presently claimed invention, the second
transesterification stage is
carried out at a temperature in the range from room temperature (e.g. 25 C)
to 100 C,
preferably to 95 C, more preferably to 90 C and even more preferably to 88 C,
preferably in
the range from 40 C to 75 C and particularly preferably in the range from 55
C to 70 C,
such as e.g. 60 or 65 C, and furthermore in particular at normal pressure.
The reaction may
be performed depending on the temperature and pressure chosen under reflux or
without
reflux. When methanol is chosen - which is the most favorable alcohol to be
employed - this
means that the reaction is performed at the boiling temperature of methanol or
slightly below
when operating at ambient pressure. By this a good temperature control can be
implemented.
This embodiment of the invention enables an energy-saving and cost-efficient
performance
of the method, because high heating costs are avoided and the respective
transesterification
reactions can be - preferably - carried out inter alia at normal pressure, so
that expensive
pressurized reactors and complex and expensive generation and maintenance of
the
temperatures and pressures, such as are necessary in the prior art, can be
omitted. Hence this
embodiment is preferred over the other embodiments for the second
transesterification step
requiring other temperatures and pressures and thus durations.
Furthermore, the low reaction temperature during the first and/or the second
transesterification stage contributes to a reduction in the operating costs
relative to known
methods and thus also improves the economy of the method relative to
previously customary
methods. However, of course, depending on the duration employed for the
transesterifications, at lower temperatures the duration of the reaction has
to be prolonged
compared to high temperatures, as otherwise no satisfying yields are
obtainable. Hence, the
net benefit in terms of energy saving depends on the complete outline of the
process, the
equipment employed and the temperature and duration of the reactions, as a
simply
reduction in time leads to higher reaction temperature (if the yield should
stay the same) or
lower yields (if the duration stays the same).
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A further advantage of the transesterification which can be carried out
according to the
presently claimed invention without pressure also resides in the fact that
costly safety
measures, which are necessary in the event of the use of pressure vessels, can
be omitted,
when the method is applied, since all operations are carried out at normal or
atmospheric
pressure, and, due to the low reaction temperatures, in an energy-efficient
manner and
quickly. Especially performing the reaction at around the boiling temperature
of the
solvent/reactant employed for the transesterification (i.e. the alcohol such
as methanol,
ethanol etc.) permits a good temperature control, as excessive temperatures
can be avoided
as then the alcohol component will boil and thus cool down the reaction
mixture again to the
desired temperature. Hence, the obvious advantage of performing at ambient
pressure and
lower temperatures is the omittance of (more expensive) pressurized equipment
but with the
drawback of usually longer reaction times needed to obtain the same yield of
conversion.
In an alternative embodiment of the presently claimed invention, the second
transesterification reaction takes place over a period of about 2 to 10,
preferably over a period
of 4 to 10 hours and more particularly 5 to 8 hours at temperatures of 90 to
145 C. and more
particularly 120 to 130 C and under a pressure of 2 to 10 bar. The obvious
advantage of this
embodiment is the very high conversion to be achieved at relatively short
times.
Further optional steps following the transesterification are:
i) optionally separating and removing methanol from the reaction mixture
obtained from the transesterification step;
ii) optionally separating and removing FME from the reaction mixture
obtained
from the previous step,
iii) optionally separating and removing the basic catalyst from the
reaction mixture
obtained from the previous step, and/or
iv) separating and removing the phase comprising glycerin from the reaction
mixture obtained from the previous step.
The same rationales, measures etc., are applied as already described above in
the paragraph
on the first transesterification, to obtain the in principle same results
and/or achieve the
same advantages as described there and thus to further purify the mixture
prior to the next
process step.
Step (g) - Addition of water
In an embodiment of the presently claimed invention, when water is added in
step (g), it is
added in an amount in the range from 15% to 25%, preferably from 18% to 22%,
and
particularly preferably in the range from 19.5% to 20.5%, in each case based
on the mass of a
total batch, in order in particular to set a mass ratio of sterol: FMEs:
methanol: water of
substantially 1:2.5-3:2.2-2.5:0.8-1.2.
In an embodiment of the presently claimed invention, the steps of
optionally separating and removing methanol from the mixture obtained from the
step of
adding water;
optionally separating and removing FME from the mixture obtained from the
previous
step,
optionally separating and removing the basic catalyst from the mixture
obtained from the
previous step, and/ or
separating and removing the phase comprising glycerin from the mixture
obtained from the
previous step,
as described for the previous step 0 could be applied again after the end of
step g).
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The same rationales, measures etc. are applied as already described above for
such measures
within the paragraph on the first transesterification, to obtain the same
results as described
there and thus to further purify the mixture prior to the next process step.
The addition of water to the reaction mixture, which takes place after the
second
transesterification stage, makes it possible in a particularly simple manner
for substances
which would impede crystallization of the sterols to be removed in particular
from a sterol-
containing phase of the trartsesterified batch. Thus, by the addition of
water, glycerin present
in the reaction mixture, catalyst and contaminants are separated off from the
distillation
residue, wherein the said substances pass into the water phase. Furthermore,
the added water
largely extracts the methanol, which is still present in the reaction mixture,
so that the
solubility of the sterols in the methyl ester phase decreases considerably and
they crystallize
out or at least start to crystallize.
Furthermore, during the addition of water to the reaction mixture, it was
surprisingly
ascertained that when a specific water concentration is reached, a
spontaneous, very
complete crystallization out of the sterols can already be observed at the
reaction
temperature, wherein a 3-phase system, consisting of a FME phase, a water
phase and sterol
crystals forms simultaneously, wherein the respective density of the three
phases increases
in the aforesaid sequence. Thus it has been shown that in particular the
addition in the
aforesaid quantitative ratio of sterol: FMEs: methanol: water of substantially
1:2.5-3:2.2-
2.5:0.9-1.1 is particularly effective in order to achieve a clear separation
of the three phases,
whereby further processing of the reaction mixture is greatly simplified,
which in turn has
an extremely positive effect on the economy of the procedure, in particular
with regard to an
energy-saving and time-saving reaction of the starting products and obtaining
the desired
phytosterols and tocopherols.
Furthermore, it has proved advantageous to cool the homogenized emulsion or
suspension
to a temperature in the range from 50 C to 35 C., preferably in the range
from 100 C to 300
C. and particularly preferably in the range from 15 C. to 25 C., so that a
subsequent phase
separation is simplified considerably. Furthermore, the crystal structure of
the required
phytosterol crystals can be significantly improved by compliance with a
maturation period,
which in turn has a perceptible positive effect on improved filtration
properties of the crystals
and also yields of crystals. According to the invention the maturation period
is in particular
in the range from 1 hour to 48 hours, preferably in the range from 2 hours to
36 hours and
particularly preferably in the range from 4 hours to 12 hours.
Step (h) - Crystallization of the sterols
Successful crystallization typically requires a free sterol concentration of
at least 20 to 25%.
Sterol concentrations of > 40% can be achieved by the process according to the
presently
claimed invention. Should the concentration still be below a value which does
not allow
reasonable crystallization, it is increased by distilling off the fatty acid
esters produced in the
"transesterification of the sterol esters" process step. The procedure
involved corresponds to
the "fatty acid ester distillation" step. If the transesterification of the
sterol esters was carried
out under pressure and the metal soaps precipitated were removed by
adsorption, FME is
added as solvent. In this case, the quantity of FME is again 30 to 200% by
weight and
preferably 50 to 100% by weight, based on the amount of product used in the
transesterification of the sterol esters.
In an embodiment, the presently claimed invention relates to the purification
of the sterol
fractions which, apart from the lower alcohol, mainly contain methyl esters,
takes place in a
known manner, i.e. the hot mixtures (ca 50- 70 C.) are slowly cooled to form
the phytosterol
crystals, which are formed at a temperature of from 15 C to 50 C, preferably
20 C to 45 C,
more preferably 25 C to 35 C, even more preferably 20 C to 30 C, in a
crystallizer. If
necessary, alkaline catalyst from the transesterification present in the
mixture can be
neutralized beforehand, for example by addition of citric acid or other
suitable organic or
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inorganic acids that are also suitable or acceptable for the intended use of
the sterols later on;
preferably, such neutralization is omitted if the feed for the crystallization
allows for.
In an embodiment of the presently claimed invention, the lower alcohol is
selected from the
group consisting of methanol, ethanol and isopropyl alcohol. Preferably the
lower alcohol is
methanol. The alcohol may contain small amounts of water, but preferably is
essentially
water-free.
In an embodiment of the presently claimed invention, only those mixtures which
already
have a ratio by weight of sterol to methanol of 100:25 to 100:75 from their
production should
be used. Otherwise methanol has to be added or distilled off. Under these
conditions, the
crystallization begins at temperatures of 60 - 65 C, but could be also done
at higher
temperatures, if the crystallization is done at elevated pressures and/or if
the solvent mixture
employed has a high boiling point than the one disclosed as preferred herein.
In an embodiment of the presently claimed invention, the ratio of sterol:
methanol is in the
range of 1: 0.1 to 1: 5, preferably 1: 0.5 to 1:3, more preferably 1:0.5 to
1:2.5.
In an embodiment of the presently claimed invention, the sterol containing
phase, which
primarily contains sterol crystals, may subsequently be washed with methanol,
wherein the
quantity of methanol is in the range from 20% to 800 %, preferably in the
range from 125% to
600%, more preferably in the range from 200% to 400% in each case based on the
mass of the
sterol crystal phase.
In an embodiment of the presently claimed invention, the sterol containing
phase, which
primarily contains sterol crystals ,may subsequently be washed with methanol,
wherein the
quantity of methanol is in the range from 50% to 800%, preferably in the range
from 125% to
700%, more preferably in the range from 200% to 550% in each case based on the
mass of the
sterol crystal phase, wherein this methanol washing is optionally preceded by
a displacement
washing of the sterol crystals with methyl ester, in particular vegetable oil
methyl ester such
as, for instance, methyl ester of rapeseed oil and/or soya oil and/or
sunflower oil and/or
coconut oil and/or palm oil and/or cottonseed oil and/or corn germ oil, at a
proportion in
the range from 50% to 500%, preferably in the range from 75% to 400%, and
particularly
preferred in the range from 100% to 350%, in each case relative to the mass of
the sterol crystal
phase.
In an embodiment of the presently claimed invention, the phytosterol crystals
are formed at
a temperature of from 15 C to 50 C, preferably 20 C to 45 C, more preferably
25 C to35 C
even more preferably 20 C to 30 C, such as 20 C, 21 C, 22 C, 23 C, 24 C, 25
C, 26 C, 27
C, 28 C, 29 C, 30 C, 31 C, 32 C, 33 C, 34 C or 35 C.
In an embodiment of the presently claimed invention, the phytosterol crystals
are formed at
a temperature of from 15 C to 50 C, and more preferably at every temperature
in between
15 to 50 C.
In an embodiment of the presently claimed invention, in order to increase the
sterol yield,
part of the mother liquor is recycled, for example to the crystallization
process, after filtration
of the crystal suspension. The return stream is fed to the system together
with the fatty acid
esters in the "catalyst removal (II)" process step. Another way of recycling
the mother liquor
is to introduce it into the first (a) or second (c) transesterification step.
The recycle ratio of the mother liquor depends to a very large extent on the
starting material
and hence on the composition of the mother liquor. It may be in the range from
0.1 to 5Ø A
recycle ratio of 0.2 to 3.0 is preferably established.
Step (i) - Separation of phases
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In an embodiment of the presently claimed invention, the separation of the
phases is carried
out by means of a filter, a screen or a decanter centrifuge or the like
apparatus suitable for
separating liquid/solid (or solid-containing) phase-mixtures, wherein a filter
centrifuge or a
5 decanter is preferably used, with a filter centrifuge being more
preferred. By the use of a filter
or a decanter centrifuge in practice a filter cake can be obtained with a
significantly lower
residual moisture ("moisture" meaning the content of solvent(s) employed) than
would be
possible for example with differential pressure filtration or other filtration
techniques.
10 Furthermore, a 3-phase decanter is also very suitable for separating the
multi-phase system
consisting of a sterol-containing phase, a glycerin-containing and a methanol-
containing
phase and a tocopherol-containing phase, wherein the phase containing sterol
crystals or the
sterol crystals themselves form the heaviest phase and can be separated off or
pre-thickened
well by means of the 3-phase decanter, whilst simultaneously the FME phase and
the water
15 phase containing glycerin and methanol can be obtained separately.
In this case the separation of the sterol crystals by means of a
discontinuously operating filter
centrifuge also offers the possibility of carrying out cake washing
immediately after the
filtration.
Step (j) Optional crystallization of the Sterols
In an embodiment of the presently claimed invention, the free sterols obtained
from
crystallization (in step (h)) and phase separation in step i) may be further
(re-)crystallized to
obtain sterol crystals of higher purity, by re-dissolution in the same
solvent/solvent mixture
used for the first crystallization. Then, again, the obtained crystals have to
be separated as
disclosed before for step i).
Step (k) - Purification of the sterol
In an embodiment of the presently claimed invention, the separated sterol
crystals are
subjected to further purification.
In an embodiment of the presently claimed invention, the sterol crystals are
further purified
using a solvent or solvent system. The sterol crystals obtained in step h) and
- if performed -
step j), either in a separate process step or a combined process step - are
purified using an
organic solvent, a solvent mixture of more than one organic solvents and
optionally but not
preferred also containing water, or - more preferred - an azeotropic solvent
mixture of at
least one protic polar solvent and an at least one aprotic polar solvent.
In an embodiment of the presently claimed invention, the purification of the
sterol fraction
occurs in the presence of a solvent system which comprises at least one polar
aprotic solvent.
In an embodiment of the presently claimed invention, the step k) of the
purification of the
sterol fraction occurs in the presence of at least one polar aprotic solvent
which is ethyl
acetate, methyl ethyl ketone and methyl acetate, dichloromethane, N- methyl
pyrrolidone,
tetrahydrofuran, acetone, dimethylformamide, acetonitrile, dimethyl sulfoxide,
heptane
and/or hexane, with ethyl acetate, methyl ethyl ketone, methyl acetate,
acetone, heptane
and/or hexane being preferred, and with ethyl acetate, methyl ethyl ketone
and/or methyl
acetate being even more preferred, with methyl acetate being most preferred.
In an embodiment of the presently claimed invention, the purification of the
sterol fraction
occurs in the presence of at least one polar aprotic solvent which is ethyl
acetate, acetone,
methyl ethyl ketone and/or methyl acetate.
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In a particularly preferred embodiment, methyl acetate is used as the sole
polar aprotic
solvent.
In an embodiment of the presently claimed invention, the purification of the
sterol fraction
occurs in the presence of at least one polar aprotic solvent and at least one
polar protic solvent
which are mixed together and/or form an azeotrope in the solvent system.
In an embodiment of the presently claimed invention, the polar protic solvent
is water,
ethanol, methanol, isopropyl alcohol, butanol and/or acetic acid.
In an embodiment of the presently claimed invention, the polar protic solvent
is water,
ethanol, methanol and/or isopropyl alcohol.
In a particularly preferred embodiment methanol is used as the sole polar
protic solvent.
In an embodiment of the presently claimed invention, the polar aprotic solvent
is present in
the range of 25 to 75% by weight, based on the amount of phytosterol,
preferably in the range
of 30 % to 50 % by weight, based on the amount of phytosterol, and every value
in between
30 % to 50 %, based on the amount of phytosterol, with ethyl acetate, acetone,
methyl ethyl
ketone and/or methyl acetate being the preferred polar aprotic solvent (s),
and methyl acetate
being more preferred as the sole polar aprotic solvent.
In an embodiment of the presently claimed invention, the polar protic solvent
is present in
the range of 5 to 50 % by weight, based on the amount of phytosterol,
preferably in the range
of 10 to 30 % by weight, based on the amount of phytosterol, and every value
in between 10
% to 30 %, based on the amount of phytosterol, with methanol being the
preferred polar protic
solvent.
In an embodiment of the presently claimed invention, for measurement of the
Gardner color
number, the phytosterol is provided in the form of a 10% by weight solution in
pyridine,
In an embodiment of the presently claimed invention, the final sterol product
has a Gardner
color number of less than 4.0, when measured for a 10 wt.% of sterol in
pyridine.
In an embodiment of the presently claimed invention, the final sterol product
has a Gardner
color number of less than 3.0, preferably less than 2.0, more preferably less
than 1.5, when
measured for a 10 wt.% of the sterol in pyridine.
In an embodiment of the presently claimed invention, the solvent content in
the purified
phytosterol is less than100 ppm, preferably less than 50 ppm, more preferably
less than 20
ppm, and even more preferably less than 10 ppm such as 5 or 1 ppm, and every
value in
between 100 and 1 ppm, based on the total weight of the purified phytosterol.
In an embodiment of the presently claimed invention, the sterol ester content
in the purified
phytosterol is less than 10 % by weight, preferably less than 5 % by weight,
more preferably
less than 2 % by weight, even more preferably less than 1 % by weight, and
most preferably
less than 0.5 % by weight, such as 0.1, 0.05 % by weight and every value in
between 5 and
0.05 % by weight, based on the total weight of the purified phytosterol.
Step 1) - optional further drying the sterols
The washed sterol crystals can be dried using conventional dryers of all
kinds, to remove
remaining solvents. Application of reduced pressure helps to increase the
removal of solvent
traces. This step serves as drying or "pre-drying', depending on the method
employed and
the desired content of residual solvent in the final sterol product to be
obtained. The latter of
course mainly depends on the intended use of the sterols.
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Thus, in an embodiment the sterols obtained as sterol crystals may be further
dried by e.g.
stream stripping at a temperature of 130 to 200, preferably 150 'DC to 170 C,
for 1 to 3 hours,
to remove the solvent.
Step m) - optional further purifying the sterols by melt-drying to remove
trace amounts of
solvents within the sterols
Following the "conventional" drying of the previous step 1), the (pre-)dried
crystals can be
melted preferably under reduced pressure to remove solvent traces enclosed
within the
crystals. By this, the residual content of solvents can be lowered even more
so as to achieve
certain higher product qualities being usable also for critical applications,
e.g. direct
applications to human beings in nutritional or pharmaceutical products.
Step n) - optional subjecting the sterols to a particle-forming process to
obtain sterol particles
The melted sterols from previous step m) need to be solidified. That could be
done either by
simple cooling with stirring of any kind, e.g. in an extruder, a paddle dryer
and the like. Other
known methods for solidification of melts are prilling, in apparatuses such as
prillers
including jet-prillers, which can form droplets close to spherical shapes, or
simply in dripping
towers, in which molten material is dropped into colder air or gases, all such
methods to
finally obtained solid, particulate sterols, which are preferably in forms
that do not show
dusting but good flowability and preferably a high density, to obtain sterols
particulates with
easy handling properties.
Thus, in a further embodiment, the sterols obtained - and preferably (pre-
)dried - are
subjected to a particle forming process, such as prilling, preferably jet-
prilling, which is
preferably done under liquid nitrogen, to obtain solid, close to spherical,
low to non-dusting
sterol particles of very low organic solvent-content, which are suitable for
direct use
including oral intake by humans.
Step (o) - Tocopherol separation and purification
In an embodiment of the presently claimed invention a further stage of
obtaining tocopherols
from the tocopherol-containing phase the FME phase of the multi-phase system,
which
contains the tocopherol in dissolved form, is preferably subjected to a
distillation for
separation off of the methyl ester, whereby it is possible to concentrate the
tocopherol content
in the FME phase to over 10 wt.% based on the amount of FME, in order to
enable a simple
further preparation of the tocopherols in a known manner.
In an embodiment of the presently claimed invention, the tocopherol is
separated by known
processes.
In a further embodiment of the presently claimed invention, the tocopherol is
purified by
known methods.
Steps (p) and (q)
In an embodiment of the presently claimed invention, the steps (p) and (q)
could be
optionally performed by known process steps, to obtain the substances in pure
forms of the
desired purity.
Advantages
The presently claimed invention is associated with at least one of the
following advantages:
1. The method according to the presently claimed invention, which - as its
core -is a two-
stage basic-catalyzed transesterification with a glycerin phase precipitation
after the
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first transesterification stage and then sterol crystallization out of the
reaction mixture
with the addition of water, wherein interposed method steps such as
neutralization,
distillation off of reagents or solvents and washing out of catalyst are
preferably
omitted, and in which furthermore by means of a combination of methyl ester
displacement washing followed by washing of the sterol crystallizate filter
cake with
an azeotrope as disclosed in the specification whilst adhering to specific
aforesaid
process parameters, it is possible to obtain phytosterols and tocopherols from
distillation residues from a transesterification of vegetable oils, in
particular from the
vegetable oil-based FME production for the field of use of biodiesel with
levels of purity
and yield which have not been attained hitherto.
2. Furthermore the previously described method according to the presently
claimed
invention can be fully implemented in a plant for FAME (biodiesel) production
or as a
down-stream processing unit to such plant, wherein in an advantageous manner
the
substances which are usual in FAME plants can be used in an optimal manner as
reagents, which is why the method is particularly effective and economical
both from
the economical point of view and also from the logistical aspects.
3. The process is suitable for various starting mixtures and does not
involve the use of
toxicologically and ecologically unsafe solvents.
4. The better utilization of the distillation residues leads to an
economic, ecologically safe
process that is easy to carry out on an industrial scale.
5. The phytosterols are obtained with a Gardner color number of less than
4.
6. The phytosterols are obtained in a high yield with a very low content of
sterol ester (i.e.
less than 10%) by using the above described purification process.
7. The solvent content of the final product is low (less than 100ppm).
Examples
The presently claimed invention is illustrated in detail by non-restrictive
working examples
which follow. More particularly, the test methods specified hereinafter are
part of the general
disclosure of the application and are not restricted to the specific working
examples.
Examples 1 and 2 are as disclosed in EP 2 635 592B1
Example 1
3850 g of a residue from the distillation of rapeseed methyl ester ("RME") are
mixed
according to the presently claimed invention with 1782 g RME. The analysis of
the batch gives
contents of 21.73% sterol ester, 6.21% free sterols, 1.68% tocopherols, 9.8%
glycerides and
44.17% methyl ester.
The batch is temperature-controlled at 65 C. and in a first
transesterification stage 37.5 g Na
methylate (30% solution in methanol) and 818 g methanol are added and mixed
in. After 50
minutes settling time 301.2 g glycerin-containing bottom phase are drawn off.
The reaction
in the partial glycerides is over 95%.
For the second transesterification stage for conversion of the sterol esters
into free sterols
150.2 g Na methylate (30% solution in methanol) and 1865.6 g methanol are
added. The
reaction takes place at 65 C. over 90 minutes.
1126 g water are added to the batch whilst being stirred, and sterol crystals
formed. The
suspension is cooled to 20 C. whilst being stirred and then subjected to
maturation at this
temperature.
Then the suspension is filtered by means of a filter centrifuge, and the cake
formed is
subjected while still in the centrifuge to a first washing with 3.5 liters RME
distillate and a
second washing with 10.4 liters methanol. After drying of the filter cake
moistened with
methanol the result is 908 g of white sterol powder with a sterol content of
over 98%, which
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corresponds to a yield (based on the total sterol content of the distillation
residue) of over
82%.
The filtrate from the filtration of the suspension separates by itself into a
light phase
containing PMEs, sterols and tocopherols and into an aqueous phase containing
methanol
and catalyst. Sterols and tocopherols are also dissolved in the washing RIVE
phase, whilst no
tocopherols are detectable in the washing methanol phase.
In the combined FME phases there are 87% of the tocopherols originally
detected in the RME
distillation residue. After distillation of the methyl ester phases a residue
with a tocopherol
content of 11% can be obtained which is suitable for further working up of the
tocopherols.
Example 2
3119 g of a residue from the distillation of rapeseed methyl ester are mixed
according to the
presently claimed invention with 2324 g RME. The analysis of the batch gives
contents of
27.2% sterol ester, 5.17% free sterols, 1.12% tocopherols, 8.14% glycerides
and 42.74% FME.
The batch is temperature-controlled at 65 'C. and in a first
transesterification stage 36.3 g Na
methylate (30% solution in methanol) and 873.5 g methanol are added and mixed
in. After 50
minutes settling time 319.2 g glycerin-containing bottom phase is drawn off.
The reaction in
the partial glycerides is over 95%.
For the second transesterification stage for conversion of the sterol esters
into free sterols
145.1 g Na methylate (30% solution in methanol) and 1995.7 g methanol are
added. The
reaction takes place at 65 C. over 90 minutes.
1208 g water are added to the batch whilst being stirred, and sterol crystals
formed. The
suspension is cooled to 20 C. whilst being stirred and then subjected to
maturation at this
temperature.
Then the suspension is filtered by means of a filter centrifuge, and the cake
formed is
subjected while still in the centrifuge to a first washing with 2.4 liters RME
and a second
washing with 10.4 liters methanol. After drying of the filter cake moistened
with methanol
the result is 956 g of white sterol powder with a sterol content of over 98%,
which corresponds
to a yield (based on the total sterol content of the distillation residue) of
80% Example 3 -
Purification of the sterol crystals
Example 3:
The sterols crystals obtained by a process as described and disclosed in the
previous examples
(example 1 and 2) was submitted to the following purification step:
On completion of the crystallization, the crystals were filtered off, washed
free from FME
with pure methanol and further subjected to washings with the following
solvents.
- ethyl acetate and its azeotrope with methanol, or
- methyl ethyl ketone and its azeotrope with methanol, or
- methyl acetate and its azeotrope with methanol.
with subsequent pure methanol washing.
Further the crystals were melt- dried to constant weight and subjected to
particle forming by
prilling.
The results obtained were compared with the experiments where the crystals
were washed
with FME with subsequent pure methanol washing.
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The results obtained are summarized in Tables 1-3(laboratory scale) as well as
in Tables la-
3a (commercial scale, e.g. plant level). In each table, example Cl and T1
refer to the same
sterol batch originating from the same rapeseed methyl ester distillation
residue. The same
applies to C2 and T2, C3 and T3 as well as C4 and T4 (if applicable). Thus,
example Cl has to
5 be compared with example T1 and so on.
Table 1- Solvent used is azeotrope of ethyl acetate with methanol (laboratory
scale)
Expt. No. Solvent for washing
Colour Purity Yield
Cl 1 washing of FME + 3 washings of 21
98.8 73.7
methanol
C2 1 washing of FME + 3 washings of 2.4
96.8 65.6
methanol
C3 1 washing of FME + 3 washings of 4
98.4 58.1
methanol
C4 1 washing of FME + 3 washings of 1
99.6 72
methanol
Ti 2 washings of azeotrope of ethyl acetate 1_2
99.5 74.6
/methanol + 1 washing of methanol
T2 2 washings of azeotrope of ethyl acetate 1.2
98.4 72.6
/methanol + 1 washing of methanol
T3 2 washings of azeotrope of ethyl acetate 3
100 69.5
/methanol +1 washing of methanol
T4 2 washings of azeotrope of ethyl 0.6
99.7 72
acetate/methanol + 1 washing of
methanol
10 Table la- Solvent used is azeotrope of ethyl acetate with methanol
(commercial scale)
Expt. Solvent for washing
Color Purity Yield
No.
Cl 1 washing of FME + 3 washings of 2.7
n.d. 62.5
methanol
Ti 2 washings of azeotrope of ethyl 0.7
n.d. 61.2
acetate/methanol + 1 washing of
methanol
n.d. = not determined
Table 2- Solvent used is azeotrope of methyl ethyl ketone with methanol
(laboratory scale)
Expt. No. Solvent for washing
Colour Purity Yield
Cl 1 washing of FME + 3 washings of 3.6
99.2 54.4
methanol
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C2 1 washing of FME + 3 washings of 27
991. 62.0
methanol
C3 1 washing of FME + 3 washings of 4
98_4 58.1
methanol
T1 2 washings of azeotrope of methyl ethyl 1.9
99.3 70.3
ketone /methanol + 1 washing of
methanol
T2 2 washings of azeotrope of methyl ethyl 1.9
99.4 75.7
ketone /methanol + 1 washing of
methanol
T3 2 washings of awotrope of methyl ethyl 2_8
99_4 70.6
ketone /methanol + 1 washing of
methanol
Table 2a- Solvent used is azeotrope of methyl ethyl ketone with methanol
(commercial scale)
Expt. Solvent for washing
Color Purity Yield
No.
C1 1 washing of FME + 3 washings of 1.9
n.d. 59.2
methanol
T1 2 washings of azeotrope of methyl 1.2
n.d. 64.9
ethyl ketone/methanol + 1 washing of
methanol
n.d. = not determined
Table 3: Solvent used is azeotrope of methyl acetate with methanol (laboratory
scale)
Expt. No. Solvent for washing
Colour Purity Yield
C1 1 washing of FME + 3 washings of 4
98.4 58.4
methanol
C2 1 washing of FME + 3 washings of 2.7
99.1 62.6
methanol
C3 1 washing of FME + 3 washings of 3_6
99.1 62.6
methanol
C4 1 washing of FME + 3 washings of 3.0
100 75.1
methanol
T1 2 washing of azeotrope of methyl acetate 3.2
99.3 71.8
/methanol +1 washing of methanol
T2 2 washing of azeotrope of methyl acetate 1.2
99.1 74.7
/methanol + 1 washing of methanol
T3 2 washing of azeotrope of methyl acetate 1.6
99.1 74.7
/methanol + 1 washing of methanol
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1T4 3 washing of arpotrope of methyl 0.5
100 77
acetate/ methanol
Table 3a - Solvent used is azeotrope of methyl acetate with methanol
(commercial scale)
Expt. Solvent for washing
Color Purity Yield
No.
Cl 1 washing of FME + 3 washings of 2.2
n.d. 62.7
methanol
Ti 2 washings of azeotrope of methyl 1.0
n.d. 67.7
acetate/methanol + 1 washing of
methanol
n.d. = not determined
Conclusions:
According to Table 1 (laboratory scale), the color of the final sterol product
is remarkedly
better in case of Ti to T4 than in case of Cl to C4. In comparison to the
latter, the purity is at
least slightly better, whereas, the yield is at least the same or even better
for T1 to T4. As can
be taken from Table la (plant level), the color is strongly improved for Ti
compared to Cl,
whereas, the yield more or less stays the same.
According to Table 2 (laboratory scale), the color and especially the yield of
the final sterol
product is remarkedly better in case of Ti to T3 than in case of Cl to O. In
comparison to the
latter, the purity is slightly better for Ti to T3. As can be taken from Table
2a (plant level),
color and yield are improved for T1 compared to Cl.
According to Table 3 (laboratory scale), the yield and especially the color of
the final sterol
product is remarkedly better in case of T1 to T4 than in case of Cl to C4. In
comparison to the
latter, the purity is at least the same or even slightly better for T1 to T4.
As can be taken from
Table 3a (plant level), color and yield are improved for Ti compared to Cl.
It will be appreciated by those skilled in the art that changes could be made
to the
embodiments described above without departing from the broad inventive concept
thereof.
It is understood, therefore, that this invention is not limited to the
embodiments disclosed,
but it is intended to cover modifications within the spirit and scope of the
presently claimed
invention as defined by the appended claims.
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