PROCESS FOR THE PURIFICATION OF A FATTY ACID ALKYL
ESTER BY LIQUID/LIQUID EXTRACTION
Description
The present invention relates to a process for the
extraction of the residual monoglycerides which occur
in a fraction of fatty acid alkyl esters resulting from
transesterification which are used in particular to
10 manufacture biodiesel.
The term "fatty acid alkyl esters" (abbreviation FAAEs)
is understood to mean, within the meaning of the
invention, preferably the esters resulting from the
15 transesterification of C1 to C8 alcohols with C8 to C36
fatty acids. These FAAEs thus correspond to the
formula: R'CO-OR', where R'CO is an aliphatic acyl group
comprising from 8 to 36 carbon atoms and R' is a linear
or branched alkyl group comprising from 1 to 8 carbon
20 atoms.
Thus, fatty acid methyl esters (abbreviation FAMEs) are
obtained by transesterification of fatty acids of
vegetable or animal origin with methanol, generally in
25 the presence of a basic catalyst, such as NaOH. The
fatty acids originate mainly from vegetable oils, such
as rapeseed, sunflower, soybean, peanut, olive, sesame,
safflower, coconut, palm, castor or jatropha oil,
microalgae and the like. The fatty acids can< also
30 originate from animal sources, for example from waste
originating from the food processing industry, such as
abattoir waste, from animal fats, such as chicken,
beef, pig or fish fats, or from used frying oils.
35 Fatty acid methyl esters (abbreviation FAMEs). are the
major constituents of the biodiesel produced today. For
this reason, the present invention is described
generally in the continuation of the text and the
examples with reference to the purification of a
40 fraction of fatty acid methyl esters. Nevertheless, the
- 2 -
process of the invention is obviously not limited to
the purification of the fractions of fatty acid methyl
esters but applies to any fraction of fatty acid alkyl
esters as defined above, such as, for example, fatty
5 acid ethyl esters or the esters resulting from
transesterification of fatty acids with 2-ethylhexanol.
Standard EN 14214 (or Standard ASTM D6751) describes
the requirements relating to FAAEs (FAMEs) used as
10 biodiesel. One of the criteria is the cold filter
plugging point (CFPP) according to the standard EN 116
in Europe (or according to Standard ASTM Method D 2500
in the USA). This CFPP criterion corresponds to the
temperature of blockage of a cold filter in the
15 presence of FAAE. This temperature depends in part on
the content of residual saturated monoglycerides in the
FAAE s resulting from transesterification. In
particular, the content of residual monoglycerides in
the FAAEs has to be less than or equal to 0.8% by
20 weight with regard to the weight of the FAAEs,
according to Standard EN 14214. This content of
residual monoglycerides is measured according to
Standard EN 14105 in biodiesels.
25 The document US2007/0151146 describes a process for the
separation and then for the filtration, using adsorbent
compounds (such as granular glucose, boric acid or
diatomaceous earth), of the steryl glycosides from the
biodiesel. This process can sometimes entrain a small
30 portion of residual monoglycerides simultaneously with
the steryl glycosides. On the other hand, the process
described in this document does not make it possible to
selectively, efficiently and simply extract virtually
all the residual monoglycerides from FAAEs, in
35 particular FAAEs highly charged with monoglycerides,
that is to say comprising more than 2% by weight of
monoglycerides.
- 3 -
An aim of the present invention is thus to provide a
simple process for the selective extraction of residual
monoglycerides from FAAEs, in order to improve the lowtemperature
behaviour of FAAEs and to render them
5 usable as biodiesels (in accordance with Standard
EN 14214).
A subject-matter of the present invention is thus a
process for the selective extraction of monoglycerides
10 present in a fraction of fatty acid alkyl esters
(FAAEs), comprising at least one stage of liquid/liquid
extraction by means:
- of a polar solvent (PS) comprising a light alcohol,
15 that is to say a lower aliphatic alcohol having a
number of carbons within the range from 1 to 8,
preferably from 1 to 5, indeed even better still from 1
to 4;
20 - and optionally of a nonpolar solvent (NS) comprising
a solvent which is immiscible with the light alcohol.
The term "liquid/liquid extraction" is understood to
mean, within the meaning of the invention, an
25 extraction during which the solvent (s) used is (are)
liquid at the extraction temperature.
Advantageously, the light alcohol is chosen from
methanol, ethanol, isopropanol, n-propanol, butanol,
30 isobutanol, 2-ethylhexanol and their mixtures.
According to a preferred embodiment of the invention,
the light alcohol is methanol, which exhibits the
advantage of already being used during the
transesterification of the FAMEs. Advantageously, the
35 process of selective extraction of monoglycerides
according to the invention does not require the use of
a special adsorbent product and does not require a
subsequent filtration stage either.
- 4 -
The said polar solvent preferably comprises from 99.9
to 70% of light alcohol and from 0.1 to 30% of water,
preferably from 80 to 99% of light alcohol and from 1
to 20% of water and preferably from 85 to 95% of light
5 alcohol and from 5 to 15% of water. This is because the'
amount of monoglycerides extracted according to the
process of the invention increases when the degree of
hydration of the light alcohol increases (see the
examples below).
10
Advantageously, the said nonpolar solvent is chosen
from hexane, heptane, benzene, bicyclohexyl,
cyclohexane, decalin, decane, hexane (Texsolve C),
kerosene, methylcyclohexane, Texsolve S or S-66,
15 naphtha (Texsolve V), Skellite, tetradecane, Texsolve
(B, C, H I S, S-2, S-66, S-LO, V), supercritical C02,
pressurized propane, pressurized butane, natural
solvents, such as terpenes (limonene, a- and P-pinene,
and the like) and their mixtures; and is preferably
20 hexane. The use of a solvent which is immiscible with
the light alcohol makes it possible to more easily
separate the phase comprising the purified FAAEs from
the phase comprising the monoglycerides extracted with
the light alcohol.
25
The term "fraction of fatty acid alkyl esters (FAAEs)"
is understood to mean, within the meaning of the
invention, the combination formed by the fatty acid
alkyl esters resulting from transesterification and
30 their impurities which comprise in particular
monoglycerides (also known as monoacylglycerols).
Preferably, the fraction of FAAEs comprises at least
90% by weight of fatty acid methyl esters (FAMEs), with
35 respect to the weight of the said fraction.
The fatty acid alkyl esters used as starting material
in the process of the invention comprise at least one
ester chosen, for example, from methyl esters of
- 5 -
rapeseed, safflower, sunflower, nasturtium, mustard
seed, olive, walnut, hazelnut, avocado, grape seed,
sesame, soybean, maize, peanut, cottonseed, rice,
babassu, castor, palm, palm kernel, lupin, j atropha,
5 coconut, linseed, evening primrose, j o j oba, camelina or
algal oil, of tallow, such as beef or pork tallow, of
fish, of chicken fat, of pig fat, of milk fatty matter,
of shea butter, of biodiesel, of used cooking oil, of
used frying oil, of miscella, of derivatives of these
oils, in particular hydrogenated derivatives or
conjugated derivatives, of the fractions of these oils,
and their mixtures.
A fraction of fatty acid alkyl esters resulting from
transesterification generally comprises from 0.5 to 5%
by weight, more commonly from 0.8 to 3% by weight, of
monoglycerides, with respect to the total weight of the
said fraction, before the liquid/liquid extraction
stage of the process of the invention.
20 According to the process of the invention, the
monoglycerides are extracted into the phase comprising
the light alcohol (phase of the polar solvent).
According to a preferred embodiment of the process of
25 the invention, the polar solvent (PS) is introduced
countercurrent-wise to the fraction of FAAEs, resulting
in a heavy phase comprising the purified FAAEs being
obtained and in a light phase enriched in
monoglycerides being obtained.
30 This is because, when a nonpolar solvent, such as
hexane, is not used, it is the phase comprising the
light alcohol which has extracted the monoglycerides
which is lighter than the phase comprising the purified
FAAE s .
35 Preference is given to this embodiment, which uses only
the polar solvent for the extraction (without nonpolar
solvent) and which already exhibits an excellent
extraction performance, as demonstrated in the examples
below. Furthermore, the light alcohol, generally
- 6 -
methanol is already available on site to carry out the
transesterification. No attempt will thus be made to
introduce, in addition and especially, a hydrocarbon
which is not used up until then.
5
According to a second embodiment, the process of the
invention comprises the following stages:
1- mixing the FAAEs with the NS and the PSI stirring
the mixture obtained and then separating it by
10 settling until a heavy phase 1 (HP1) enriched in
monoglycerides is obtained and a light phase 1
(LP1) comprising the purified FAAEs is obtained.
In this second embodiment of the process of the
15 invention, the nonpolar solvent is lighter than the
polar solvent and it is the nonpolar solvent which
comprises the purified ester.
According to an alternative form of this second
embodiment, stage 1- is followed by the following
20 stages in the process of the invention:
2- mixing, stirring and then separating by settling
LP1 + PS -+ HP2 + LP2
3- mixing, stirring and then separating by settling
HP1 + HP2 + NS -+ HP3 + LP3
25 4- mixing, stirring and then separating by settling
HP3 + NS -+ HP4 + LP4, in which:
- HP4 is the heavy phase enriched in monoglycerides,
and
- the sum of the light phases LP2+LP3+LP4 comprises
30 the purified FAAEs, which preferably have a content
of monoglycerides of less than or equal to 0.8% by
weight, with regard to the weight of purified
FAAEs .
35 The process according to the invention can be carried
out without difficulty on the industrial scale,
batchwise or continuously, using one or more devices
chosen from mixers-settlers, mechanically stirred
mixers, static mixers, gravity settlers, centrifugal
- 7 -
decanters, coalescers, centrifugal liquid-liquid
extractors, liquid-liquid hydrocyclones, extractors
comprising separate stages, extractors comprising
stages which are not separate (differential
5 extractors), countercurrent columns, over one or more
consecutive stages, in particular gravity columns,
spray towers, packed columns, perforated plate columns,
stirred columns, pulse columns or rotating disc
columns, contacters and any other device used for
10 liquid extraction. These liquid/liquid extraction
devices are described in Parts J 2 764, J 2 765 and J 2
766 of the Techniques de llIngenieur [Technologies for
the Engineer].
Advantageously, the process of the invention, whatever
15 the embodiment described above, comprises at least two
extraction stages. Advantageously, the said process
comprises at least five extraction stages.
Preferably, the polar solvent/FAAEs ratio by weight is
20 within the range from 1/5 to 5/1, preferably from 1/4
to 4/1 and preferably from 1/4 to 1/1.
Another subject-matter of the present invention is a
fraction of fatty acid alkyl esters (FAAEs) of
25 vegetable or animal origin capable of being obtained
according to the process of the invention,
characterized in that its content of monoglycerides is
less than 0.6% by weight, preferably less than 0.5% by
weight, preferably less than 0.4% by weight, preferably
30 less than 0.3% by weight and preferably less than 0.25%
by weight, with regard to the weight of the fraction of
FAAE s .
A further subject-matter of the present invention is a
I
35 biodiesel comprising a purified fraction of FAAEs
having a content of monoglycerides of less than 0.6% by
weight, preferably less than 0.5% by weight, preferably
less than 0.4% by weight, preferably less than 0.3% by
weight and preferably less than 0.25% by weight, with
- 8 -
regard to the weight of the fraction of FAAEs; the said
fraction being obtained according to the process of the
invention.
A better understanding of the invention and its
5 advantages will be obtained on reading the examples
below, given purely by way of illustration and without
implied limitation.
Examples
10
Unless otherwise indicated, all the percentages are
given by weight.
The term "@" means "phase".
The following examples illustrate the liquid/liquid
15 extraction processes according to the invention for the
extraction of the monoglycerides (MGs) present in a
fraction of fatty acid methyl esters (FAMEs) not in
accordance with Standard EN 14214 as regards its
content of residual monoglycerides (monoglycerides
20 > 0.8%).
For this, a complying rapeseed methyl ester (CRME)
assaying, before doping, 0.4% of monoglycerides was
deliberately doped with monoglycerides. Several doping
levels were selected, in particular 1; 1.3 and 2.4%.
25 In examples 1 to 3, liquid-liquid extraction tests were
carried out in the presence of a mixture of polar (PS)
and nonpolar (NS) solvents, in this case hydrated
methanol and hexane, in Examples 1 and 2, according to
the following procedure:
30 1. 5 g of MG-doped CRME + 30 ml NS + 15 ml PS + heavy
@ 1 + light @ 1
2. Light @ 1 + 15 ml PS -+ heavy @ 2 + light @ 2
3. Heavy @ 1 + heavy @ 2 + 30 ml NS + heavy @ 3 +
light @ 3
b
35 4. Heavy @ 3 + 30 ml NS + heavy @ 4 + light @ 4
NS: nonpolar solvent (hexane)
PS: polar solvent (methanol/water at different water
contents) .
Concentration:
- 9 -
1. Heavy @ 4 + polar fraction
2. Light @ 2 + light @ 3 + light @ 4 -+ nonpolar
fraction
In examples 1 to 4, the solvent is removed for each
5 fraction or final phase by vacuum distillation on a
rotary evaporator, at 90°C and under a vacuum of
20 mbar. Thus, in the following Tables 1 to 9, the
"distributions by weight" are given as %, after
evaporation of the solvent. Likewise, the contents of
10 monoglycerides ( % ) are measured with respect to the
"dry weight" (once the solvent has been evaporated) of
the phase which comprises the purified FAMEs.
Example 1:
15 The analytical balance of the purified esters starting
from a fraction of methyl esters highly charged with
monoglycerides (2.4%) is described in detail in the
following Table 1.
- 10 -
Table 1
Comments :
5 The amount of material extracted into the light phase
decreases when the degree of hydration of the methanol
tends to fall.
For all that, the extraction selectivity for the
monoglycerides passes through a maximum as a function
10 of the water content of the polar solvent, for a
methanol/water ratio by weight within the range from
80/20 to 99/1.
The process according to the invention makes it
possible to reduce by a factor of 2.5 the monoglyceride
15 content of a fraction of methyl esters initially highly
charged.
Polar solvent ( %
methanol/% water)
Nonpolar solvent
Heavy polar phase
(methanol-rich)
distribution by weight, %
after evaporation of the
solvents
Light nonpolar phase
(hexane-rich) distribution
by weight, % after
evaporation of the
solvents
MonoG1yceri.de content ( % ) ,
starting material, %
MonoGlyceride content ( % ) ,
light phase, %
MonoGlyceride extraction
yield, light phase, %
Example 2:
Test
No. 5
80/20
Hexane
0.8
99.2
2.4
1.63
32.0
Test
No. 1
90/10
Hexane
1.5
98.5
2.4
0.95
60.7
Test
No. 2
99/1
Hexane
3.7
96.3
2.4
1.16
53.1
- 11 -
The analytical balance of the purified esters ,starting
from a fraction of methyl esters moderately charged
(1.3%) with monoglycerides is described in detail in
the following Table 2.
T a b l e 2
Comments :
The amount of material extracted into the light phase
decreases when the degree of hydration of the methanol
tends to fall.
For all that, the extraction selectivity for the
monoglycerides passes through a maximum as a function
of the water content of the polar solvent, for a +
methanol/water ratio within the range from 80/20 to
99/1.
The process according to the invention makes it
possible to reduce by a factor of 2 the monoglyceride
content of a highly charged methyl ester. Thus, a
Polar solvent ( %
methanol/% water)
Nonpolar solvent
Heavy polar phase
distribution by weight, %
after evaporation of the
solvents
Light nonpolar phase
distribution by weight, %
after evaporation of the
solvents
MonoGlyceride content ( % ) ,
starting material, %
MonoGlyceride content ( % ) ,
light phase, %
MonoGlyceride extraction
yield, light phase, %
Test
No. 6
80/20
Hexane
0.7
99.3
1.3
1-00
25.9
Test
No. 3
90/10
Hexane
1.4
98.6
1.3
0.65
52.2
Test
No. 4
99/1
Hexane
3.0
97.0
1.3
0.79
42.8
- 12 -
methyl ester not in accordance with the European
standard for biodiesel (monoglyceride > 0.8%) can be
purified by liquid-liquid extraction.
5 Example 3:
The analytical balance of the purified esters starting
from a fraction of FAMEs moderately charged with
monoglycerides (1.03%) is described in Table 3 below.
T a b l e 3
Comments :
- the selectivity of the process is confirmed since an
15 extraction yield for the monoglycerides of 66% is
obtained starting from a batch of ester moderately
charged with monoglycerides. The FAME resulting from
the light phase is then in accordance with the European
standard for biodiesel (monoglyceride content < 0.8%).
20 *
Example 4: Purification tests on a countercurrent
column
a) Extraction by a polar solvent, according to a
single-stage extraction, of the MGs from a fraction of
25 FAMEs which is moderately charged:
Polar solvent (% methanol/% water)
Nonpolar solvent
Heavy polar phase distribution by
weight, %
Light nonpolar phase distribution by
weight, %
MonoGlyceride content ( % ) , starting
material, %
MonoGlyceride content ( % ) , light
phase, %
MonoGlyceride extraction yield, light
phase, %
Test
No. 7
90/10
Hexane
0.8
99.2
1.03
0.35
66.2
- 13 -
Procedure: 20 g MG-doped CRME + 20 g PS + heavy @ 1 +
light 0 1
5 The analytical balance of the purified esters starting
from a fraction of FAMEs moderately charged with MG
(1.03%) is given in Table 4 below:
Test No. 8
Heavy @ 1
Light @ 1
T a b l e 4
Crude weight, g
21.0
19.0
(methanol-rich)
Comments:
In the absence of hexane, entrainment of the
monoglycerides by the methanol occurs. The methanol
15 becomes the light phase. t
In a single extraction and in the presence solely of
hydrated methanol (10/90), the MGs are extracted with a
yield of 40%, making it possible to bring the MG
content back to conforming levels (biodiesel), this
20 being achieved with a high yield of purified FAME
Dry weight, g
19.2
0.8
(after
evaporation of
the solvent)
Polar solvent ( % methanol/% water)
Nonpolar solvent
Heavy phase distribution by weight, %
Light phase (methanol-rich)
distribution by weight, % after
evaporation of the solvent
MonoGlyceride content ( % ) , starting
material, %
MonoGlyceride content ( % ) , heavy
phase, %
MonoGlyceride extraction yield, %
Test
No. 8
90/10
None
96.0%
4.0%
1.0
0.64
40.3
- 14 -
(96%). This test demonstrates the feasibility of the
process with a solvent/ester ratio which is realistic
industrially.
The methanol-rich phase, comprising the monoglycerides
5 but also methyl esters, can be easily recycled upstream
of the extraction process in the transesterification
unit, where the process for the conversion of the
monoglycerides will be repeated until complete
conversion is achieved, so that there is no loss of
10 material.
b) Single-stage extraction by a polar solvent of the
MGs from a fraction of esters which is weakly charged:
Procedure: 20 g CRME + 20 g PS + heavy @ 1 + light @ 1
15
The analytical balance of the purified esters starting
from a batch of esters which is weakly charged (0.67%
of MGs) is given in Table 5 below.
Test No. 9
Heavy @ 1
Light @ 1
20 Table 5
Crude weight, g
21.0
19.0
Comments :
The MGs are extracted with a yield of the order of 50%,
25 making it possible to bring the MG content back to very
Dry weight, g
19.2
0.8
Polar solvent (% methanol/% water)
Solvent/CRME ratio
Light phase distribution by weight, %
Heavy phase distribution by weight, %
MonoGlyceride content ( % ) , starting
material, %
MonoGlyceride content ( % ) , heavy
phase,, %
MonoG1yceri.de extraction yield, %
Test
No. 9
90/10
1/1
4.0%
96.0%
0.67
0.34
51.3
low levels (< 0.4%), this being achieved with a high
yield of purified ester (96%). This test demonstrates
the feasibility of the process with a solvent/ester
ratio which is realistic industrially.
5 c) Two-stage extraction of the MGs by a polar solvent
Procedure:
20 g currently conforming CRME + 20 g PS -+ heavy cD 1
+ light cD 1
Heavy cD 1 + 20 g PS + heavy cD 2 + light cD 2
Test No. 10 / Crude weight, g 1 Dry weight, g
I
Heavy cD 1
Light cD 1
(methanol-rich)
Light cD 2
The analytical balance of the purified esters starting
from a batch of esters which is weakly charged (0.67%
of MGs) by countercurrent two-stage extraction is shown
15 in Table 6.
20.9
19.1
(methanol-rich)
Heavy cD 2
T a b l e 6
19.2
0.8
20.6 0.9
20.3
20 Comments:
18.3
9*
Polar solvent ( % methanol/% water)
Solvent/CRME ratio
Light phase 1 distribution by weight, %
Light phase 2 distribution by weight, %
Heavy phase 2 distribution by weight, %
MonoGlyceride content ( % ) , starting
material, % I
MonoGlyceride content ( % ) , heavy phase,
%
MonoG1yceri.de extraction yield, %
Test
No. 10
90/10
1/1
4.0
4.3
91.7
0.67
0.21
71.3
- 16 -
Starting from an ester weakly charged with MGs, the
extraction of the glycerides is efficiently carried out
countercurrent-wise over two stages: MG extraction
yield > 71% and MG content of the purified esters of
5 0.2% approximately. The purified ester yield of the
process is greater than 90%, it being possible for the
fraction enriched in MGs to be recycled in the
transesterification. This test confirms the industrial
relevance of the process according to the invention.
10
d) Single-stage extraction of the MGs by a polar
solvent - Influence of the polar solvent/FAME ratio:
The objective is to evaluate the influence of the polar
solvent/ester ratio with the aim of reducing the
15 amounts of solvent involved. A solvent/ester ratio of
1/2 was tested.
Procedure: 20 g CRME + 10 g PS -+ heavy @ 1 + light @ 1
20
The analytical balance of the purified esters starting
from a batch of esters which is weakly charged (0.67%
of MGs) is shown in Table 7 below, which esters were
purified by countercurrent single-stage extraction with
25 a solvent/ester ratio of 1/2.
Test No. 11
Heavy cD 1
Light @ 1
Crude weight, g
21.2
8.8
Dry weight, g
19.5
0.5
T a b l e 7
Test
Polar solvent ( % methanol/% water)
Solvent/CRME ratio
Light phase distribution by weight, %
Heavy phase distribution by weight, %
MonoGlyceride content ( % ) , starting
No. 11
90/10
1 /2
2.4%
97.6%
0.67
material, %
MonoG1yceri.de content ( % ) , heavy
Comments :
5 In comparison with Test 9, a reduction by half in the
amount of solvent involved makes it possible to
maintain a high MG extraction yield of 40% and to
achieve a residual MG content in the purified esters of
approximately 0.4%, very slightly greater than Test 9
10 (0.34%) but far below the current specifications for
biodiesel. The overall yield of purified ester is
logically improved: 97.6% vs 96.0% in Test 9.
0.41
phase, %
MonoGlyceride extraction yield, %
e) Two-stage extraction of the MGs by a polar solvent
15 on a two-stage column - Influence of the solvent/ester
ratio
40.3
Procedure:
20 g currently conforming CRME + 10 g PS -+ heavy @ 1 +
20 light @ 1
Heavy @ 1 + 10 g PS + heavy @ 2 + light @ 2
Test No. 12 I Crude weight, g I Dry weight, g
Heavy @ 1
Light @ 1 (MeOH)
Light @ 2 (MeOH)
Heavy 2
21.1
8.9
10.1
21.0
19.7
0.3
0.5
19.2
The analytical balance of the purified esters starting
from a batch of esters which is weakly charged (0.67%
of MGs), countercurrent two-stage extraction with a
solvent/ester ratio of 1/2, is shown in Table 8.
5
T a b l e 8
Test
Polar solvent (% methanol/% water)
Solvent/CRME ratio
Light phase 1 distribution by weight, %
Light phase 2 distribution by weight, %
Heavy nonpolar phase 2 distribution by
No. 12
90/10
1 /2
1.5%
2.5%
96.0%
weight, %
MonoGlyceride content ( % ) , starting 0.67
material, %
MonoGlyceride content ( % ) , heavy phase,
Comments :
0.32
%
MonoGlyceride extraction yield, %
10 In comparison with Test 10, a reduction by half in the
amount of solvent involved makes it possible to
maintain a high extraction yield of 54% and to achieve
a residual monoglyceride content in the purified esters
of 0.3% approximately, very slightly greater than Test
15 10 (0.2%) but far below the current specifications for
54.1
biodiesel. The overall yield of purified ester is
logically improved: 96.0% vs 91.7% in Test 10.
Example 5: Multistage (five-stage) countercurrent
20 extraction by a polar solvent of the monoglycerides
from a methyl ester. 4
Procedure for simulation of an extraction on a
countercurrent -(five-stage) column:
40 g currently conforming (0.67%) CRME + 10 g PS +
25 heavy @ 1 + light @ 1
The polar solvent/FAME ratio by weight is equal to 1/4.
- 19 -
Five separating funnels are installed and are named Al,
A2, A3, A4 and A5.
1. The five funnels are charged with 40 g of ester and
10 g of hydrated methanol 10/90, are agitated well
5 and left to separate by settling. HI is the upper
phase of funnel No. 1 and B1 is the lower phase of
funnel No. 1, and so on for the other funnels.
2. B1 is withdrawn into a round-bottomed flask and
concentrated, HI is placed in a beaker and 10 g of
10 methanol are placed in funnel No. 1.
3. B2 is placed in funnel No. 1, H2 is placed in a
beaker and HI is placed in funnel No 2.
4. B3 is placed in funnel No. 2, H3 is placed in a
beaker and H2 is placed in funnel No. 3.
15 5. B4 is placed in funnel No. 3, H4 is placed in a
beaker and H3 is placed in funnel No. 4.
6. B5 is placed in funnel No. 4, H5 is placed in a
round-bottomed flask and concentrated, and H4 and
40 g of methyl ester are placed in funnel No. 5. All
20 the funnels are subsequently agitated and then left
to separate by settling.
Stages 2 to 6 form a first sequence representing the
1st extraction stage. Phases B1 and H5 are then weighed
and analysed (see Table 9, end sequence 1). The
25 continuation of the test consists in starting the
second sequence in the presence of the contents of the
funnels resulting from the preceding sequence and in
reinjecting fresh methanol and starting material ester,
respectively, into funnels 1 and 5. And so on, until
30 five complete sequences have been carried out. In fact,
the five sequences simulate the operation of the fivestage
column. The mass and analytical balances carried
out on the phases exiting at the end of each sequence
are represented in Table 9.
35 Figure 1 gives a diagrammatic representation of the
extraction on a countercurrent (five-stage) column.
The mass and analytical balance of the countercurrent
extraction over five stages is shown in Table 9 (the DW
percentages are given for the dry weight).
- 20 -
T a b l e 9
5 Comments:
- after a 1st extraction stage, the MG content rapidly
decreases ibelow 0.5%);
- the MG content rapidly reaches a plateau of 0.45%
from the second sequence since it barely changes
10 subsequently during the extraction;
- the overall yield of esters subsequent to the five
extraction stages is 97.2% and the overall MG
extraction yield is 34.6%.
Starting
material
End
sequence 1
End
sequence 2
End
sequence 3
End
sequence 4
End
sequence 5
15 The results of the tests of Examples 1 to 5 according
to the invention demonstrate the effectiveness+ of the
liquid-liquid extraction process in the presence of
hydrated methanol as extraction solvent.
% light
phase
(which was
rich in
MeOH)
(%DW)
-
0.7
0.4
0.4
0.8
0.5
% heavy
phase
(%DW)
10 0
99.3
99.6
99.6
99.2
99.5
Monoglyceride
content,
heavy
phase
(%DW)
0.67
0.49
0.45
0.45
0.45
0.44
Monoglyceride
extraction
yield ( % )
-
27.3
33.1
33.1
33.4
34.7

- 21 -
CLAIMS
1. Process for the selective extraction of
monoglycerides present in a fraction of fatty acid
5 alkyl esters (FAAEs), comprising at least one stage of
liguid/liquid extraction by means:
- of a polar solvent (PS) comprising a light
alcohol,
- and optionally of a nonpolar solvent (NS)
10 comprising a solvent which is immiscible with the light
alcohol.
2. Process according to Claim 1, in which the
light alcohol is chosen from methanol, ethanol,
isopropanol, n-propanol, butanol, isobutanol,
15 2-ethylhexanol and their mixtures.
3. Process according to Claim 1 or 2, in which the
said polar solvent comprises from 99.9 to 70% of light
alcohol and from 0.1 to 30% of water.
4. Process according to any one of Claims 1 to 3,
20 in which the nonpolar solvent is chosen from hexane,
heptane, benzene, bicyclohexyl, cyclohexane, decalin,
decane, hexane, kerosene, methylcyclohexane, Texsolve S
or S-66, naphtha, Skellite, tetradecane, Texsolve,
supercritical CO2, pressurized propane, pressurized
25 butane, natural solvents and their mixtures.
5. Process according to any one of Claims 1 to 4,
in which the FAAEs comprise at least one ester chosen
from esters of rapeseed, safflower, sunflower,
nasturtium, mustard seed, olive, sesame, soybean,
30 maize, peanut, walnut, hazelnut, avocado, grape seed,
cottonseed, rice, babassu, castor, palm, palm kernel,
lupin, jatropha, coconut, linseed, evening primrose,
jojoba, camelina or algal oil, of tallow, such as beef
or pork tallow, of chicken fat, of pig fat, of fish, of
35 milk fatty matter, of shea butter, of biodiesel, of
used cooking oil, of used frying oil, of miscella, of
derivatives of these oils, in particular hydrogenated
derivatives or conjugated derivatives, of the fractions
of these oils, and their mixtures.
- 23 -
weight, preferably less than 0.4% by weight, preferably
less than 0.3% by weight and preferably less than 0.25%
by weight, with regard to the weight of the fraction of
FAAEs.
5 16. Biodiesel comprising a purified fraction of
FAAEs having a content of monoglycerides of less than
0.6%, the said fraction being obtained according to the
process of any one of Claims 1 to 14.
• «
m
- 23 -
weight, preferably less than 0.4% by weight, preferably
l e s s than 0.3% by weight and preferably less than 0.25%
by weight, with regard to the weight of the fraction of
FAAEs.
5 16. Biodiesel comprising a purified fraction of
FAAEs having a content of monoglycerides of less than
0.6%, the said fraction being obtained according to the
process of any one of Claims 1 to 14.