METHOD FOR PRODUCING FATTY ACID ESTER FROM FLATTENED OLEAGINOUS GRAINS

Abstract
The invention relates to a method for preparing fatty acid esters particularly used as bio-diesel fuel from whole oleaginous grains, characterised in that it comprises the following successive steps: preheating the whole non-husked grains; flattening the oleaginous grains; drying the flattened grains in order to obtain a water content and a volatile material content between 0.5 and 2.5%, and preferably between 1.5% and 2%; performing a transesterification by contacting the dried, flattened grains with an alcoholic medium in the presence of a catalyst; separating the liquid and solid phases resulting from the transesterification; neutralising the liquid phase from step d); and removing the alcohol and separating the glycerine from the fatty acid esters.
Description

This application claims the priority of the French application FR0756716 which is incorporated herein in its entirety.


The present invention concerns a novel method for preparing fatty acid esters which can notably be used as biodiesel, prepared from oilseeds.


Biodiesel is a fuel obtained from vegetable oil or animal fat that is converted using a chemical process called transesterification, in order to obtain Vegetable Oil Methyl Esters (VOMEs) when using methanol or Vegetable Oil Ethyl Esters (VOEEs) when using ethanol. Biodiesel competes with vegetable oils used in the crude state and with petrodiesel i.e. conventional fossil diesel. Biodiesel can be used alone in engines or mixed with petrodiesel.


In prior art methods to obtain VOME's or VOEEs, either the crushed seeds are subjected directly to the transesterification reaction, or the oil is first extracted from the seeds, this oil is semi-refined and then the transesterification step is conducted on the neutral semi-refined oil. However, these prior art methods are not completely satisfactory. In the first case, at industrial level, the seeds must be finely crushed to obtain the best yield possible, but the phase separation step is all the more difficult the finer the crushing. In the second case, extraction of the oil and prior treatment make industrial application of the process complex and costly.


Other preparation methods have been described more recently, notably by Khalil et al (US2005/0011112) and Haas et al (US2006/0155138). These techniques, instead of seeds, use “flakes” obtained from hulled seeds. These flakes are abundantly manufactured in the agricultural industry but their use for the manufacture of biodiesel has several drawbacks: first the flakes are more fragile than the whole seeds, which leads to the formation of fine matter which has to be filtered so that the oil can be used as biodiesel; secondly the VOME and VOEE yields are not as high owing to the absence of the seed shells; finally the formation of these flakes requires costly packaging units.


The subject-matter of the present invention is a method to prepare fatty acid esters from oilseeds with excellent yield and which, at the same time, overcomes the disadvantages of the processes described in the prior art.


The first subject of the present invention is a method to prepare fatty acid esters which can be used as biodiesel, prepared from whole oilseeds, characterized in that it comprises the following successive steps:

    • a. Preheating the whole non-hulled seeds;
    • b. Flattening the oilseeds with their husks;
    • c. Drying the flattened seeds so as to obtain a water and volatile matter content of between 0.5 and 2.5%, preferably between 1.5% and 2%;
    • d. Transesterification by contacting the flattened, dried seeds with an alcohol medium in the presence of a catalyst;
    • e. Separating the liquid and solid phases resulting from transesterification;
    • f. Neutralizing the liquid phase derived from step e); and
    • g. Removing the alcohol and separating the glycerine from the fatty acid esters.


By <<oilseeds>> is meant any plant seeds containing fat, preferably rich in triglycerides.


Therefore germ, pips, kernels, and nuts also come under this category. The oilseeds also contain proteins, fibres and minerals.


The seeds are preferably chosen from among plant seeds which can be cultivated. For example use may be of rapeseed, jatropha seed, groundnut, castor bean, sesame seed, sunflower seed, safflower seed, soybean, lupin seed, camelina seed, cotton seed. The preferred seeds are rapeseed, sunflower seed and jatropha seed. Further preferably the seeds are rapeseeds.


Additionally, it is also possible to use seeds chosen from among rapeseed, groundnut, castor bean, sesame, sunflower, safflower, soy, lupin, camelina, cotton.


In the method subject of the present invention, the seeds can be used with all or a large part of their husk. In the meaning of the present invention <<oilseeds>> designates the whole seed or the seed rid of part of its husk. For example, with regard to rapeseed, sunflower seed and jatropha seed, the seed is preferably used essentially whole i.e. with at last 80% of its husk. This forms an advantageous fibrous support which can avoid disintegration of the flattened seed when contacted with the alcohol medium during the transesterification step d).


However, if the husk is too voluminous compared with the fruit (for example macadamia nut, Brazil nut, andiroba nut, coconut, shea nut or cupuacu nut) it is preferable to rid the seed of part of its husk so as not to perturb the transesterification reaction. It may also be advantageous to conduct prior crushing of the seeds if they are of large size (e.g. for the macadamia, Brazil, andiroba nuts, coconut, shea or cupuacu nut).


According to step b) of the method subject of the present invention, the oilseeds are flattened. They are then generally in the form of a thin elongate sheet, flake or chip.


Before the flattening step, the seeds are preferably cleaned i.e. rid of their solid impurities such as stones, rags, sticks, metal particles, dust.


The thickness of the flattened seeds is preferably between 10 μm and 1 mm. According to one particularly preferred embodiment, the thickness of the flattened seeds lies between 0.1 and 0.3 mm, and further preferably the thickness of the flattened seeds is less than 0.2 mm notably for rapeseed.


Also, the size of the flattened seeds i.e. their length or width is preferably between 3 and 5 mm, notably for rapeseeds and other seeds of similar size, in which it is around 4 mm.







According to one particular embodiment the oilseeds can be preheated at a temperature of between 40° C. and 60° C., preferably 50° C. before carrying out the flattening step b) so as to increase their plasticity. However, the seeds are brought to this temperature just the time that is necessary to reach the desired plasticity. It is effectively preferable to avoid drying the seeds which causes their fractioning during the flattening. The seeds must not under any circumstance be baked or dried before they are flattened.


For this purpose, the oilseeds can preferably be heated at a temperature of between 50 and 55° C. for 5 to 60 min, preferably 30 minutes, before conducting the flattening step b), optionally under water vapour.


According to the present invention, flattening of the oil seeds is advantageously achieved using rollers which may be of any type, in particular smooth or fluted, preferably smooth. Their diameter may measure up to 80 cm. The distance between the rollers is preferably less than 0.2 mm, further preferably less than 0.1 mm.


The speed of the rollers is determined so as to avoid fractioning the seeds when they are being flattened. Preferably the diameter and speed of the rollers are identical to avoid phenomena of avulsion and hence fractioning of the seeds.


According to one particular embodiment, flattening of the oilseeds is achieved using smooth rollers preferably in a single pass.


The flattening step b) is an essential step in the method, since it allows a significantly higher yield to be obtained than without any flattening, i.e. a better transesterification yield and a better extraction yield of ethyl esters.


After the flattening step, the seeds must be dried as quickly as possible to stop enzymatic activity and thereby avoid degradation of their content matter. The drying step c) is therefore conducted immediately after the flattening step b) and no later than 24 hours after the flattening step b), preferably less than 2 hours after the flattening step b) and at best within one hour after flattening. Also, by means of the drying step, it is possible to store the flattened seeds before subjecting them to the transesterification step d). Drying of the flattened seeds is performed so as to obtain a water and volatile matter content of between 0.5 and 2.5%, preferably between 1.5% and 2%.


The water and volatile matter content of the dried seeds is assayed using the method NF V 03-909.


According to one particular embodiment, the drying step c) is performed at a temperature of between 50 and 100° C., preferably between 70° and 90° C.


After the drying step c), a transesterification step is conducted by contacting the flattened, dried seeds with an alcohol medium in the presence of a catalyst. The catalyst may be basic or acid, preferably basic.


The alcohol medium may comprise one or more alcohols chosen from among the C1-C6 alcohols such as methanol or ethanol, optionally in a mixture with one or more aliphatic hydrocarbons such as hexane. The alcohol medium is preferably ethanol containing a quantity of water of less than 5000 ppm, preferably 3000 ppm.


The basic catalyst is preferably anhydrous and homogeneous and can be chosen from among sodium hydroxide, potash, sodium or potassium carbonate or hydrogen carbonate, sodium or potassium carbonate, sodium or potassium methylate or ethanolate.


The acid catalyst may be sulphuric acid for example.


Before starting the transesterification step, it may be advantageous, under a discontinuous schedule, to place the flattened seeds previously in contact with the alcohol medium, so as to impregnate them with this alcohol medium and promote subsequent transesterification. Pre-impregnation can be conducted for a time of between 10 and 30 min., preferably 30 minutes, at a temperature of between 40 and 80° C., preferably 75° C. This step is to be omitted if the reaction takes place under a continuous schedule.


To optimize the yield of the transesterification reaction, the weight ratio of catalyst/flattened seeds is preferably between 0.5/100 and 2/100 and/or the weight ratio of alcohol/flattened seeds is preferably between 100/100 and 500/100.


If the method is conducted in discontinuous mode, the transesterification reaction is advantageously conducted at a temperature of between 45 and 55° C., preferably at around 50° C., for a time of 10 min to 2 hours, preferably between 20 and 40 min.


According to one particular embodiment, the contacting of the flattened seeds with the alcohol medium at the transesterification step d) is conducted under slow stirring or by sprinkling and percolation. It is preferably conducted by percolation of the alcohol medium containing the catalyst through the flattened seeds. In practice, percolation can be conducted by sprinkling a bed of flattened seeds, having a height of preferably around 80 cm.


After the transesterification step, the liquid and solid phases resulting from said transesterification are separated, preferably by draining. The liquid phase collected is high in fatty acid esters produced by the transesterification reaction.


It is preferably for the residual content of fat in the solid phase i.e. cake to be less than 1% by weight of the total dry matter.


To collect the remainder of the fatty acid esters present in the solid phase, it is possible to conduct the following additional steps:

    • h) alcohol extraction of said solid phase derived from step d);
    • i) collection of the solid phase;
    • j) filtration and grouping together of the liquid phases derived from the transesterification step e) and extraction step h).


The grouped liquid phases derived from step e) can be filtered, for example through a cloth having a pore size of between 10 to 50 μm, to remove all the fine particles.


The extraction step h) is preferably conducted by counter-current percolation with ethanol, with a weight ratio of alcohol/flattened seeds of between 100/100 and 200/100.


Also, the alcohol used at extraction step h) can be chosen from among the C1-C6 alcohols such as ethanol having a water content of less than 5000 ppm, preferably less than 3000 ppm.


The liquid phase derived from transesterification step e), optionally supplemented with the liquid phase derived from extraction step h), is then neutralized either using an acid if the reaction catalyst is basic, or with a base if the reaction catalyst is acid.


The acid is preferably chosen from among sulphuric acid, hydrochloric acid, phosphoric acid, citric acid or acetic acid.


The base may be sodium hydroxide for example.


The quantity of acid added to the liquid phase is determined so that the fatty acid content of the fatty acid ethyl esters remains less than 0.25% (equivalent to an acid number<0.5 mg KOH/g).


Neutralization of the liquid phase is performed in part so as not to increase the quantity of soaps therein.


According to one particular embodiment, the neutralization acid is added in a quantity leading to a pH close to 10, notably in a quantity of less than 0.04% of the total quantity of fatty acid esters present in said liquid phase.


After the neutralization step f), the alcohol is then removed from the liquid phase and the glycerine is separated from the fatty acid esters.


The alcohol is preferably removed by evaporation at a temperature of between 50 and 100° C. under a pressure of between 200 and 1000 mbars, preferably at around 80° C. under atmospheric pressure, until a residual alcohol content of less than 1%; is obtained.


The separation of the glycerine from the fatty acid esters is preferably carried out by centrifuging at a temperature of between 60 and 80° C. It may also be carried out by static decanting. The glycerine carries with it a large part of the impurities such as the catalyst, soaps, phosphoric derivatives or sodium sulphate.


The fatty acid esters are then advantageously washed with water, preferably at around 80° C. to fully remove the impurities, and then separated from the washing water notably by decanting or centrifuging, preferably at around 80° C., then dried preferably by evaporation at a temperature of between 90 and 100° C. under a pressure in the order of 200 mbars, until a residual water content of less than 500 ppm is obtained relative to the total dry matter. The fatty acid esters thus obtained can then be packaged under nitrogen after being cooled.


A second subject of the present invention is a method to prepare oilseed cakes intended for animal feed, using the solid phase derived from step e) or i) of the method to prepare fatty acid esters such as described previously, comprising the following steps:

    • 1) Removing the alcohol from said solid phase; and
    • 2) Adding the glycerine obtained at step g) of said method to prepare fatty acid esters.


The solid phase resulting from step 1) can also be supplemented with the washing waters described previously in the method to prepare fatty acid esters.


The solid phase derived from step e) or i) of said method to prepare fatty acid esters contains between 50 and 65% alcohol by weight. Removal of the alcohol from this solid phase can be achieved mechanically, notably by pressing or spinning, then thermally by entraining with water vapour until a residual water content of less than 500 ppm is obtained relative to the total dry matter.


The final oilseed cake obtained at step 2) can then be packaged in powder form or extruded.


The removed alcohol can be collected then dehydrated, for re-use in the method to prepare fatty acid esters.


The present invention and its advantages are illustrated by the following examples.


The abbreviations used in the examples are explained in the following table:















Parameters
Unit
Significance
Measurement method







RMC
weight %
Residual
Thermobalance




moisture content
RMC 95: determined at





95° C.





RMC105: determined at





105° C.


AN
mg
Acid number
NF EN 14 104 (T60-



KOH/g
(measurement of
702)




free fatty acid




content)


PN
meq
Peroxide number
NF T 60-220



02/kg
(measurement of




peroxide-




oxidized fat)


SFC
% dry
Fat content
V 03-908



matter
(Soxlhet




extraction with




hexane)


VMC
%
Water and
NF V 03-909




Volatile Matter




content (103° C.)


Hexane
% dry
Fat content
Same method as SFC


extracted
matter

except a single


FC


extraction









1) Preparation of Oilseeds Before Flattening

The objective of this first series of tests is to evidence the importance of the preheating step of the non-dried seed before it is flattened.


For this purpose, whole, non-dried rapeseed was obtained from agricultural farms in plastic bags and were treated by causing the oven preheating temperature to vary between 25, 35, 50 and 75° C. (temperature T) followed by conventional flattening and drying steps (90° C. for 12 hours). The flattened, dried seeds were finally contacted with anhydrous alcohol, which is passed by percolation through the bed of seeds and is collected downstream of the fixed bed, percolation taking place at a greater or lesser rate depending on the initial pre-treatment conditions of the seeds (preheating and flattening). During these tests, the quantity extracted fat and the percolation rate were measured.


More precisely, the operating mode comprises the following steps:

    • (1) preheating the whole, non-dried rapeseeds in an oven thermo-regulated at variable T° C. (25, 35, 50 and 75° C.) for 60 minutes;
    • (2) flattening the whole, preheated seeds;
    • (3) the flattened seeds are placed in a fixed bed reactor thermo-regulated at 25° C.;
    • (4) ethanol held at 25° C. is then added to a weight ratio of alcohol/seed of 1.9/1;
    • (5) the ethanol passing through the seed bed is collected downstream of the fixed bed in a glass recipient. The quantity of extracted fat and percolation time are measured.


The results of these tests are grouped together in Table 1.









TABLE 1





Influence of the preheating temperature on the


quantity of fat extracted from the flattened seeds and


on percolation rate.





















Preheating
25
35
50
75



temperature, ° C.



Preheating time, min.
60
60
60
60



% fat extracted after
32
31
31
30



percolation



Percolation rate m3h ×
12.7
14.6
17.5
16.5



m2







Alcohol impregnation temperature: 25° C., 15 minutes (alcohol/flake weight ratio = 1.9/1).






It is clearly apparent, in the light of the results in Table 1 that the best compromise between percolation rate and percentage of extracted fat is obtained at a seed preheating temperature of 50° C. As a matter of fact, at 50° C., all other conditions being equal, ethanol diffuses quicker in the flake with an oil extraction yield equivalent to that of the other seed preheating conditions. At industrial level, this allows high conversion rates to be achieved, since the extracted fat is rapidly converted into esters in the presence of a catalyst. On the basis of these results, the gain in productivity at this step, obtained by comparison with non-preheated seed (25° C.) can be estimated at +38% by calculation. Preheating of the seed at 70° C. before flattening does not bring any improvement in the productivity of the method since, for an almost equivalent extraction yield (around 30%) the percolation rate is very slightly reduced (versus preheating of the seeds at 50° C.).


At a temperature higher than 70° C. the seeds might dry before flattening, the consequence of which would be to make them harder, which would lead to the production of fine matter at the flattening step.


2) Preparation of Flattened, Dried Oilseeds

The preparation of flattened, dried seeds is a very important step in the method subject of the invention. It consists of:

    • flattening the seeds, to facilitate their drying, and extraction and conversion of the fats into esters,
    • drying the flattened seeds to remove the water from the seeds.


Three series of rapeseed were prepared and examined:


Seeds prepared according to method 1,


Seeds prepared according to method 2,


Seeds prepared according to method 3.


2.1) Flattened Rapeseeds Prepared According to Method 1

According to method 1, flattening of the rapeseeds is achieved under the following conditions:

    • using roller types: either smooth rollers or fluted rollers;
    • either on fresh seeds or on dried seeds.


When the seeds are flattened in fresh form they are dried 48 h after flattening.


The flattened seeds were characterized by measuring the following parameters:

    • fat content accessible by hexane extraction (Soxlhet)
    • RMC 105—Residual Moisture Content at 105° C.
    • AN, acid number in mg of KOH/g (NF T 60-204)
    • RMC (Residual Moisture Content at 105° C.) after drying at 80° C.
    • Bulk density, kg/L
    • Percolation rate, m3/h/m2


The conditions for these measurements and the operating conditions are grouped together in Tables 2a and 2b.









TABLE 2a







Influence of drying before and after flattening, and of flattening conditions



























RMC













after











drying



Roll



Rotation
Content of


at
Bulk
Percolation



spacing
Seed
Roll
Number of
speed of
accessible3
RMC
AN (mg
80° C.
density
rate


Ref
(mm)
quality
type
flutes/cm
the rolls
fat2
105
KOH/g)
(%)
(g/L)
(L/h/m2)4





















1
0.05
fresh
fluted
8
525 Front
43.42
9.48
2.86
2.92
410
10264.5







525 Back


1bis
0.05
dry1
fluted
8
525 Front
38.81
3.42
0.86










525 Back


2
0.05
fresh
fluted
6
525 Front
41.90
7.71
1.81
1.79
401
21239.7







525 Back


3
0.05
dry1
fluted
6
525 Front
42.15
3.76
1.12
1.67
463
2495.8







525 Back





1752.1


4
0.05
fresh
smooth

525 Front
40.08
7.67
3.49










525 Back


5
0.05
dry1
smooth

525 Front
37.30
2.93
0.72










525 Back


6
0.1
fresh
fluted
10 
500 Front
42.26
7.53
2.10
1.68
421
14520.7







500 Back







































RMC













after











drying



Roll



Rotation
Content of


at
Bulk
Percolation



spacing
Seed
Roll
Number of
speed of
accessible3
RMC
AN (mg
80° C.
density
rate


Ref
(mm)
quality
type
flutes/cm
the rolls
fat2
105
KOH/g)
(%)
(g/L)
(L/h/m2)4















Table 2b: Influence of drying before and after flattening, and of flattening conditions


















7
0.1
fresh
fluted
10
530 Front
45.48
7.42
3.04
1.76
420
4016.5







700 Back


8
0.1
fresh
fluted
10
525 Front
43.06
7.82
2.18
1.88
424
12396.7







525 Back


9
0.1
dry1
fluted
10
525 Front
41.78
4.05
1.03
1.36
473
1239.7







525 Back


10
0.1
fresh
fluted
8
500 Front
42.28
7.79
1.82
1.54
419
19198.3







525 Back


11
0.1
dry1
fluted
8
525 Front
39.32
3.97
0.91










525 Back


12
0.1
fresh
fluted
6
525 Front
38.65
7.59
1.71










525 Back


13
0.1
dry1
fluted
6
525 Front
39.20
3.07
0.74










525 Back


14
0.1
fresh
smooth

500 Front
31.54
7.51
2.58










500 Back


15
0.1
dry1
smooth

500 Front
39.62
3.24
0.91










500 Back







Table 2c: Influence of drying before and after flattening, and of flattening conditions (cont.)


















16
0.1
dry1
smooth

525 Front
34.33
3.33
0.91










525 Back


17
0.2
dry1
fluted
10
700 rpm
35.72
3.69
0.92









(65/45)


18
0.2
dry1
smooth

500 Front
41.19
3.32
0.90
1.98
535
3338.8







600 Back


19
0.2
dry1
smooth

700 rpm
37.02
3.48
0.88









1The dry seeds were dried at a temperature of between 80 and 100° C.:




2Total fat content of rape seeds TH = 47% dry matter (DM)




3Direct extraction with hexane for 10 hours (8 + 2 h) (Soxlhet method)




4Characteristics of column used: L = 295 mm, dint = 39.3 mm, Sc = 1.21.10−3 m2, Sinter size = no0, Tap size = 4 mm, bed height = about 40 mm, Characteristics of ethanol used: Alcohol content = 96.2°, dam b = 0.807, dpercolation = 28330.6 L/h/m2; Operating conditions: hbed = 4 cm T = ambient, trep s = 10 min.







Conclusions:





    • dry seeds ill withstand flattening, and percolation of ethanol is lower with these seeds on account of fines,

    • drying of the seeds prevents degradation of the fats. The acid number of the fats in the dry seeds is much lower than that of fresh seeds,

    • the fluted rolls cause more fines than smooth rollers,

    • the desired distance between the rolls is no more than 0.1 mm.





2.2) Rape Seeds Prepared According to Method 2

Flattening is conducted under the following conditions:


















Flattener
DAMMAN-CROES flattener



Rolls
Smooth, diameter 14 cm,




length 24 cm



Roll spacing
0.1 mm



Rotation speed
60 rpm










The total oil content of the seed is 50%. Calculation of crushing deficiency:






Deficiency
=


50
-

extracted





matter



50
+

(

50
-

extracted





matter


)














TABLE 3







Characteristics of the rapeseeds










References













1
2
3
4















Roll spacing
0.05
0.1
0.2
0.3


Packaging
Plastic
Plastic
Plastic
Plastic



bag
bag
bag
bag


Storage time after
2
2
2
2


flattening
months
months
months
months


Volatile matter
6.59
6.34
6.73
6.67


content VMC %


Fat extracted with
49.37
49.82
48.87
46.96


hexane % DM


Crushing deficiency,
1.24
0.36
2.21
5.73


% DM


Acidity mg KOH/g
3.33
2.98
2.80
2.30









Conclusions:

The flattened, non-dried seeds do not keep well. The acid number of the fat increases very significantly after 6 weeks storage (from 1 to 3.3 mg KOH/g). The finer the seeds are flattened, the greater the degradation of the fats. The content of extracted fats (with hexane) does not change with a roll spacing of 0.05 mm to 0.1 mm. It decreases on and after 0.2 mm and especially at 0.3 mm of spacing.


It is therefore absolutely necessary to dry the seeds after flattening. The roll spacing may range from 0.05 mm to 0.1 mm. Also, it appears that if the final oilseed cake is to have fat content of less than 2%, the thickness of the flattened seed must be less than 0.2 mm.


2.3) Rapeseed Prepared According to Method 3

2.3.1) Objective


The fat of the flattened moist seeds may deteriorate through enzymatic hydrolysis during storage time. Its acid number is increased. The objective of the work conducted in this section is to determine the suitable conditions for storage of the flattened rape seeds.


The rape seeds were flattened and treated immediately on site.


2.3.2) Test Protocol


2.3.2.1) Flattening


The rape seeds (6-7% water) were flattened under the following conditions without being pre-heated:


















Flattener
HENRY flattener



Power
2HP



Rolls
Smooth, diameter 14 cm,




length 24 cm



Roll spacing
0.1 mm



Rotation speed
60 rpm



Quantity of seeds treated per test:
20 kg



Seed flow rate
25 kg/h










2.3.2.2.) Drying


The flattened seeds are then dried in a Turbétuve drying oven either at 80° C. or at 90° C. to obtain a residual water content between 1 and 2%. The drying conditions are:


















Apparatus
CERCO SEMIP Turbetuve oven




type TE 75 T1 04



Power
6.35 W



Drying baskets
4 quarters with perforated




base



Quantity of flakes
4 × 5 kg



Bed height
30 cm



Air flow rate
Heat convection










The dry seeds are packaged in sealed plastic bags and stored at room temperature. The quality of the seeds was monitored by measuring:

    • Volatile Matter Content VMC (%)
    • Content of accessible fat (% DM), yield—Soxlhet extraction with hexane for 10 h
    • acid number of the extracted fat (mg KOH/g)—NFT 60-204
    • peroxide number
    • percolation


2.3.3.) Storage Results









TABLE 4







Influence of seed storage time on the quality of fats









Date

















D
D + 1
D + 3
D + 7
D + 10
D + 14
D + 21
D + 28
D + 35




















Non-dried seeds











Residual Moisture Content 95
6.5

6.5
6.5







(RMC 95), %


Accessible fats (SFC), % dry
49.0

48.9
48.9







matter (DM)


Acid Number (AN), mg KOH/g
0.8

3.5
17.0







Seeds dried at 80° C.


RMC 95, %
1.84
2.01
1.67
1.74
1.98
1.73
2.10
2.31
2.05


Accessible fat content (SFC),
48.5
47.8
47.7
45.8
46.6
48.4
47.5
44.6
47.2


% DM


AN, mg KOH/g
0.89
0.91
0.77
0.76
0.77
0.78
0.90
0.73
0.88


PN peroxide number meq O2/kg
1.43







1.70


Seeds dried at 90° C.


RMC 95, %
1.57
1.69
1.48
1.87
1.81
1.76
1.87
1.88
1.94


Accessible fat content (SFC),
48.9
48.2
49.6
46.5
45.8
48.6
48.4
48.1
48.8


% DM


AN, mg KOH/g
0.94
0.96
0.70
0.91
0.87
0.82
0.85
0.85
0.92


PN meq O2/kg
0.73







0.80









Water intake by the flakes is very slow during storage. The other parameters for the quality of the fats show practically no change after 35 days' storage.


The flattened, non-dried seeds see the acidity of their oil rise very rapidly: for example, after one week acidity may reach a value of 17 mg KOH/g. This acidity is equivalent to 10% of the oil hydrolyzed into free fatty acids. The free fatty acids thus fabricated will have a negative impact on the reaction in a basic medium: they will be saponified (consumption of NaOH catalyst). Therefore the ester yield will be lower the greater the extent of hydrolysis. On the other hand, the seeds dried immediately after their fabrication have an oil acidity that is stable over time.


We conclude that the flattened, dried rapeseeds may be stored at least 35 days in a sealed plastic bag.


In the light of the experiments performed, it is preferable to proceed with the preparation operations for the seeds in the following order:

    • Cleaning the impurities,
    • Pre-heating to increase plasticity (<60° C.), an addition of water vapour may be beneficial,
    • Flattening with smooth rolls, in a single pass,
    • Drying at a temperature ranging from 70 to 90° C. immediately after flattening.


3) Reaction Conditions and Treatment of the Products

3.1) Influence of Alcohol Impregnation Temperature of the Conditioned Seed


The objective of this series of tests is to evidence the importance of the alcohol impregnation step of the previously flattened and dried seeds, and in particular its incidence on the extracting and reacting property of ethanol with respect to oily fat. For this purpose, we caused the temperature of alcohol impregnation to vary between 25, 50 and 75° C. (temperature T).


From an experimental viewpoint, the operating mode comprises the following key steps:

    • (1) Flattening whole rapeseed with preheating at 50° C. for 60 minutes;
    • (2) Drying the flattened seed at 90° C. for 12 hours (residual moisture of the flake: 20)
    • (3) impregnation of the seeds in a thermo-regulated closed reactor equipped with mechanical stirring and a coolant, in the presence of anhydrous ethanol at temperature T for 15 minutes with a weight ratio of ethanol/flake of 1.9/1. At this point, the content of extracted fat is measured after 15 minutes. This content translates the extractive capacity of the alcohol under the test conditions and hence its subsequent reactivity in the presence of a catalyst in the transesterification reaction of the extracted oil.


In this type of <<in planta>> method, since the medium consists of a liquid phase and a solid phase, the reaction is chiefly governed by the diffusion of alcohol in the seed. Alcohol plays the twofold role of solvent for the fats and of reagent. Therefore, the more the yield of extracted fat is promoted the higher the yield of target esters. Under reaction conditions in the presence of a catalyst, the extracted fat is rapidly converted to esters. Indeed, extraction of the fats from the seeds by alcohol is an essential factor of the method. The test results are given in Table 5.









TABLE 5





Influence of alcohol impregnation temperature


on conditioned seeds




















Alcohol impregnation
25
50
75



temperature, ° C.



Impregnation time, min.
15
15
15



% extracted fat after 15
33
41
59



minutes







Conditions: Flake/Alcohol impregnation ratio: 1/1.9



Flake: preheating 50° C., flattening 0.05 mm, drying 2% moisture






It is clearly apparent, in the light of the results of Table 5, that the higher the alcohol impregnation temperature the higher the yield of fat extraction, hence its subsequent conversion into target esters.


This step can be used when operating in discontinuous mode to improve fat extraction and purity of the esters thus converted.


On the other hand, when operating in continuous mode, this step is not advisable since a precipitate has been observed at the head of the bed when the catalyst is added after an impregnation time of 30 min and even with an impregnation time of 5 min. This precipitate causes very rapid and very major decrease in percolation. At industrial level it cannot be contemplated to work with such low percolation rates as there is a risk of clogging the extractor.









TABLE 5bis







Influence of pre-impregnation on


percolation and on conversion under continuous mode


operation









Tests











1
2
3
















Impregnation time, min
5
30
0



Peroclation rate on
10
10




impregnation m3/hm2



Reaction time, min.
30
30
30



Percolation rate on reaction,
5
1
13



m3/hm2



Extraction yield, %
90
92
85



Ester purity, % ester
100
100
100







Conditions: Flattened seed thickness 0.35 mm, dried at 80° C., Temperature 50° C. NaOH/EtOH/seed ratio: 1.5%/2/1






Pre-impregnation has a positive effect on extraction (90-92%), on the other hand percolation rates are largely reduced when the catalyst is added. The flow rate then drops from 10 to 5 even to 1 m3/hm2 depending on pre-impregnation time.


The longer the pre-impregnation time, the greater the decrease in flow rate. This phenomenon can be accounted for as follows. In a neutral alcohol medium, sugars are soluble. The longer the extraction the more the quantity of soluble sugar increases. Sugars are no longer soluble in a basic medium on account of an aldol condensation reaction. A precipitate is then formed which concentrates at the head of the bed, and it is this precipitate which perturbs percolation.


Under discontinuous mode this reaction is also possible, with the difference that the precipitate thus formed is diluted in the entirety of the seeds and therefore has little impact on filtering.


3.2.) Reaction with EtONa as Catalyst


The objective of this series of tests is to validate the conditioning of the flattened, dried seeds before the reaction. We used EtONa as catalyst. The seeds were prepared according to method 2 described above:


drying at 60° C.,


flattening with two roll distances


storage in anhydrous ethanol


We reviewed the main operations of the method









TABLE 6







Influence of roll spacing









References










ET7
ET8













Pre-impregnation
24 h at Tambient
72 h at Tambient


Reaction


T° C.
50
50


Time, h
2
2


Ethanol, g
1400
1400


Water content ppm
450
450


Catalyst


99% EtONa, g
23.7
23.7


Ethanol, g
89.3
89.3


Flattened
1000
1000


rapeseed, g


Roll spacing, mm
0.05
0.10


Water, %
2.12
2.12


SFC Fat content1,
46.1
46.1


% DM


AN of the fat, mg
0.9
0.9


of KOH/g


Seed preparation
Method 2
Method 2


method
Flattener:
Flattener:


Seeds dried with
DAMMAN-CROES
DAMMAN-CROES


cooperative dryer
Roll type:
Roll type:


at 90-100° C.
Smooth
Smooth


before flattening
Spacing: 0.05 mm
Spacing: 0.10 mm



T 2nd drying:
T 2nd drying:



60° C.
60° C.



Drying time: 1 h
Drying time: 1 h


Ethanol/flake,
1.5
1.5


m/m


Treatment after
Filtering under
Filtering under


baking
nitrogen at 0.5 bar.
nitrogen at 0.5 bar.



3 extractions of
3 extractions of



the cake with
the cake with



absolute ethanol.
absolute ethanol.



(Ethanol/Solid =
(Ethanol/Solid =



1/1)
1/1)


Fat content in
4.1
8.1


end cake after


reaction, % DM:


among which:


Ethyl esters (EE) %
55.3
25.4


Monoglycerides
0.33
0.9


(MG) %


Diglycerides
1.86
1.9


(DG) %


Triglycerides
42.07
70.8


(TG) %


Treatment of
Evaporation of
Evaporation of


liquid phase
ethanol 80° C.,
ethanol 80° C.,



max. vacuum 100 mbars
max. vacuum 100 mbars



(R5)
(R5)



Decanting (15 min
Decanting (15 min



at 80° C.)
at 80° C.)



4 washings of
4 washings of



esters (80° C.)
esters (80° C.)



Drying (90° C.,
Drying (90° C.,



20 mbars, 30 min)
20 mbars, 30 min)


Crude glycerine, g
74
68.2


Final esters, g
424
392


Ethyl esters (EE) %
98.8
98.0


Monoglycerides
0.47
0.78


(MG) %


Diglycerides
0.2
0.31


(DG) %


Triglycerides
0
0


(TG) %






1Determined as per standard V03-908







The final esters represent around 40% of the starting seeds. They have very high purity.


A roll spacing of 0.05 mm allows a greater quantity of esters to be produced than a distance of 0.1 mm. The yield of the transesterification reaction is therefore better with a roll spacing of 0.05 mm than with a spacing of 0.1 mm.


3.3) Optimisation of Reaction Conditions with NaOH as catalyst


As catalyst EtONa gives better performance than sodium hydroxide (NaOH). On the other hand, sodium hydroxide is much less costly than EtONa. The objective of this series of tests is therefore to define optimal reaction conditions using NaOH as catalyst (lowest consumption of catalyst and ethanol) for conversion of the triglycerides into ethyl esters.


The chief parameters examined are:


weight ratio <<Catalyst/Seed>> and effect of pre-impregnation,


weight ratio <<Ethanol/Seed>>,


water content of the ethanol,


thickness of flakes.


Operating Mode:


The reaction was carried out in a double-jacketed reactor with gentle stirring. The operating mode is as follows:

    • adding all the ethanol to the reactor at ambient temperature under nitrogen,
    • adding all the catalyst to the reactor under moderate stirring,
    • raising the temperature of the reactor to 50° C.,
    • after 30 min, adding all the flattened seeds to the reactor under moderate stirring and maintaining the temperature at 50° C.,
    • taking a sample of the reaction mixture and filtering it to obtain a liquid phase (L0) and a solid phase (S0),
    • conducting L0 extraction with hexane (liquid-liquid), washing, drying and analysing the fat obtained using HPLC,
    • conducting S0 extraction with hexane (10 h in Soxlhet); drying the low fat cake in a crystallizing dish under a hood; washing, drying and analyzing the fat obtained using HPLC.


3.3.1) Influence of the Weight Ratio <<Catalyst/Seed>> and of Pre-Impregnation on the Reaction Under Discontinuous Operating Mode.














Table 7a: Influence of the <<Catalyst/Seed>> ratio and of pre-impregnation on triglyceride


conversion in discontinuous mode













Parameters
F1bis
F2
F3
F4
F5
F6





Pre-
No
No
No
Yes
Yes
Yes


impregnation


T, ° C.



50
50
50


Time, min.



30
30
30


Reaction


T, ° C.
50
50
50
50
50
50


Time, h
2 to 4
2 to 4
2 to 4
2 to 4
2 to 4
2 to 4


Ethanol, g
1500
1500
1500
1350
1350
1350


Water content
465
434
361
361
402
402


ppm


Catalyst


99% NaOH, g
15
17.5
17.5
17.5
17.5
17.5


Ethanol, g
0
0
0
150
150
150


Colza flake, g
1000
1000
1000
1000
1000
1000


Drying temp,
90
90
60
60
80
60


° C.


Water, %
1.78
1.78
1.87
0.96
0.96
0.96


Fat content1,
48.9
48.9
48.9
48.9
48.9
48.9


% DM


AN of fat, mg
0.9
0.9
0.9
0.9
0.9
0.9


KOH/g


Seed
Method 3
Method 3
Method 3
Method 3
Method 3
Method 3


preparation
Flattener:
Flattener:
Flattener:
Flattener:
Flattener:
Flattener:


method
HENRY
HENRY
HENRY
HENRY
HENRY
HENRY



Roll type:
Roll type:
Roll type:
Roll type:
Roll type:
Roll type:



Smooth
Smooth
Smooth
Smooth
Smooth
Smooth



Spacing: 0.1 mm
Spacing: 0.1 mm
Spacing:
Spacing:
Spacing:
Spacing:



Drying T:
Drying T:
0.05 mm
0.05 mm
0.05 mm
0.05 mm



90° C.
90° C.
Drying T:
Drying T:
Drying T:
Drying T:



Drying time:
Drying time:
60° C.
60° C.
80° C.
60° C.



4 h
4 h
Drying time:
Drying time:
Drying time:
Drying time:





8 h 30
8 h 30
5 h 15
8 h 30


Fat


concentration1


after L0


reaction, %


(m/m)


2 h

16.2
20.0
22.6
23.0
23.8


4 h
16.5
19.3
17.7
22.7
23.6
24.5


L0


triglycerides


(% fat)


2 h

0
0
0
0
0


4 h

0.84
0.61
0
0
0


S0


triglycerides


(% fat)


2 h

19.1
12.59
6.16
4.31
3.38


4 h
24.76
33.74

1.85
1.40
3.26


Theoretical


Triglyceride/


ester, %


2 h



2.25
1.78
1.35


4 h



0.80
0.62
1.32










Table 7b: Influence of the <<Catalyst/Seed>> ratio and of pre-impregnation on triglyceride


conversion in discontinuous mode (cont.)












Parameters
F7
F8
F9







Pre-impregnation
Yes
Yes
Yes



T, ° C.
50
50
50



Time, min.
30
30
30



Reaction



T, ° C.
50
60
60



Time, h
2 to 4
2 to 4
2 to 4



Ethanol, g
1350
1350
1350



Water content, ppm
440
400-450
400-450



Catalyst



99% NaOH, g
17.5
17.5
17.5



Ethanol, g
150
150
150



Rapeseed flake, g
1000
1000
1000



Water, %
0.91
0.91
4.46



Fat content1 % DM
48.9
48.9
48.9



AN of fat, mg
0.9
0.9
0.9



KOH/g



Seed preparation
Method 3
Method 3
Method 1



method
Flattener:
Flattener:
Flattener:




HENRY
HENRY
STOLZ




Roll type:
Roll type:
Roll type:




smooth
smooth
smooth




Spacing: 0.05 mm
Spacing: 0.05 mm
Spacing: 0.1 mm




Drying T:
Drying T:
Drying T:




80° C.
80° C.
80° C.




Drying time:
Drying time:
Drying time:




5 h 15
5 h 15
5 h 15



Fat concentration1



after L0 reaction,



% (m/m)



2 h
23.0
20.7
19.0



4 h
2.9
23.3
19.0



L0 Triglycerides



(% fat)



2 h
0
0
0.2



4 h
0
0
0.2



S0 Triglycerides



(% fat)



2 h
4.63
6.1
12.66



4 h
3.54
3.95
9.54



Triglyceride/Ester



theoretical %



2 h
2.25
2.95
4.6



4 h
1.48
1.65
3.51








1Determined as per standard V03-908.







Under discontinuous mode, pre-impregnation is preferable for good fat extraction and conversion. The impregnation time of 30 min can be reduced to increase the productivity of the installation. Under discontinuous mode, the <<Catalyst/ethanol/seed>> ratio can be set at <<17.5 g/1500 g/1000 g>>. We note that the quality of the flattened seeds has a major influence on fat extraction. The test conditions F4, F5, F6 are the best.


3.3.2) Influence of the <<Ethanol/Seed>> Weight Ratio in Discontinuous Mode














Table 8a: Influence of the <<Ethanol/Seed>> weight ratio











Parameters
F10
F11
F12
F13





Pre-impregnation
Yes
Yes
Yes
Yes


Reaction


T° C.
50
50
50
50


Time, h
2 to 4
2 to 4
2 to 4
2 to 4


Ethanol, g
1350
1350
1350
1350


Water content
441
418
443
451


ppm


Catalyst


99% NaOH, g
17.5
17.5
17.5
17.5


Ethanol, g
150
150
100
150


Rapeseed flake g
1000
1000
1000
1000


Water, %
1.77
1.64
1.95
1.23


Fat content1 % DM
48.9
48.9
48.9
48.9


AN of fat
0.9
0.9
0.9
0.9


mg KOH/h


Seed preparation
Method 3
Method 3
Method 3
Method 3b (two


method
Flattener: HENRY
Flattener: HENRY
Flattener: HENRY
flattenings)



Roll type:
Roll type:
Roll type:
Flattener: HENRY



smooth
smooth
smooth
Roll type:



Spacing: 0.1 mm
Spacing: 0.15 mm
Spacing: 0.05 mm
smooth



Drying T: 80° C.
Drying T: 80° C.
Drying T: 80° C.
Spacing:



Drying time:
Drying time
Drying time:
1st



5 h 15
5 h 15
5 h 15
flattening:






0.5 mm






2nd






flattening:






0.05 mm






DryingT: 80° C.






Drying time:






5 h 15


Ethanol/Rapeseed
1.5
1.5
1.5
1.5


flakes


Fat


concentration1


after L0


reaction, %


(m/m)


2 h
17
15.2
18.4
21.5


4 h
19
18.1
20.4
25.1


L0


Triglycerides, %


fat


2 h
0
0
0
0


4 h
0.04
0.06
0.08
0


S0 Triglycerides


% fat


2 h
36.17
65.1
33.8
1.1


4 h
25.2
65.0
21.9
0.8


Theort.TG/Ester


2 h
13.5
30.0
14.7
0.42


4 h
6.5
28.4
8.18
0.28










Table 8b: Influence of the <<Ethanol/Seed>> weight ratio in discontinuous mode (cont.)













Parameters
F14
F15
F16
F17
F18
F19





Pre-impregnation
Yes
Yes
Yes
Yes
Yes
Yes


Reaction


T, ° C.
50
50
50
50
50
50


Time, h
2 to 4
2 to 4
2 to 4
2 to 4
2 to 4
2 to 4


Ethanol, g
1115
1115
1115
1115
1115
1115


Water content
438
3397
3343
3517
3618
3516


ppm


Catalyst


99% NaOH, g
17.5
17.5
15.2
15.2
15.2
15.2


Ethanol, g
150
150
150
150
150
150


Colza flake, g
1000
1000
1000
1000
1000
1000


Water, %
1.05
1.17
1.26

1.17
1.22


Fat content1,
48.9
48.9
48.9
1.20
48.9
48.9


% DM


AN of fat, mg
0.9
0.9
0.9

0.9
0.9


KOH/g


Seed
Method 3b
Method 3b
Method 3b
Method 3b
Method 3b
Method 3b


preparation
(Two
(Two
(Two
(Two
(Two
(Two


method
flattenings)
flattenings)
flattenings)
flattenings)
flattenings)
flattenings)



Flattener:
Flattener:
Flattener:
Flattener:
Flattener:
Flattener:



HENRY
HENRY
HENRY
HENRY
HENRY
HENRY



Roll type:
Roll type:
Roll type:
Roll type:
Roll type:
Roll type:



Smooth
Smooth
Smooth
Smooth
Smooth
Smooth



Spacing:
Spacing:
Spacing:
Spacing:
Spacing:
Spacing:



1st
1st
1st
1st
1st
1st



flattening:
flattening:
flattening:
flattening:
flattening:
flattening:



0.5 mm
0.5 mm
0.5 mm
0.5 mm
0.4 mm
0.5 mm



2nd
2nd
2nd
2nd
2nd
2nd



flattening:
flattening:
flattening:
flattening:
flattening:
flattening:



0.05 mm
0.05 mm
0.05 mm
0.07 to
0.04 mm
0.04 mm



Drying T:
Drying T:
Drying T:
0.09 mm
Drying T:
Drying T:



80° C.
80° C.
80° C.
Drying T:
80° C.
80° C.



Drying time:
Drying time:
Drying time:
80° C.
Drying time:
Drying time:



5 h 15
5 h 15
5 h 15
Drying time:
5 h 15
5 h 15






5 h 15


Ethanol/
1.3
1.3
1.3
1.3
1.3
1.3


rapeseed


flakes


Fat


concentration1


after L0


reaction,


(m/m)


2 h
26.7
27.4
27.8
20.0
26.5
26.5


4 h
27.3
27.2
27.3

28.5
27.4


L0


triglycerides


% fat


2 h
0
0
0.1
0.04
0.2
0.1


4 h
0
0
0

0.2
0


S0


triglycerides


% fat


2 h
2.0
1.0
2.04
46.8
4.92
4.09


4 h
0.9
1.1
1.22

3.55
3.31


Theoretical


TG/Ester


2 h
0.83
0.37
0.85
21.6
2.32
2.00


4 h
0.37
0.46
0.51

1.39
1.61






1Determined as per standard V03-908







The <<Ethanol/Seeds>> ratio may lie between 1.3/1 under the stirred, discontinuous schedule of the reaction. For a continuous schedule and a fixed bed, this ratio must be adjusted.


3.3.3) Influence of Water Content in the Ethanol









TABLE 9







Influence of water content in the ethanol











Parameters
F14
F15







Date
27 Feb 06
28 Feb 06



Pre-impregnation
YES
YES



Reaction



Temperature ° C.
50
50



Time, h
2 to 4
2 to 4



Ethanol, g
1115
1115



Water content, ppm
438
3397



Catalyst



99% NaOH, g
17.5
17.5



Ethanol, g
150
150



Rapeseed flake, g
1000
1000



Water, %
1.05
1.17



Fat content, % DM
48.9
48.9



Acidity, mg KOH/g
0.9
0.9



Method
3B
3B




Roll spacing
Roll spacing




0.05 mm
0.05 mm




Drying 80° C.
Drying 80° C.



Ethanol/seed ratio
1.3
1.3



Fat concentration
27.3
27.2



in L0, %



L0 triglycerides
0
0



S0 triglycerides
0.88
1.1










The water content of the ethanol can be about 3000 ppm for the reaction.


3.4) Definition of Treatment Conditions for the Products after Reaction


3.4.1) Liquid-Solid Extraction after Reaction


Operating Mode:


Two tests were conducted under the same reaction conditions:

    • Impregnation of the flattened, dried seeds with ethanol at 50° C. for 30 min (Ethanol/Seed=115/100 weight ratio);
    • Transesterification at 50° C. for 1 h with the weight ratios <<NaOH/Ethanol/flattened dried seed=1.5/130/100>> (discontinuous mode—1 kg flattened dried seed);
    • Filtering of the reaction mixture through filter paper of 11-micron pore size under 0.5 bar N2.


The oilseed cakes derived from the first filtration underwent 4 co-current extractions with ethanol having different water contents.









TABLE 10







Influence of water content of the ethanol on


seed-cake extraction









Parameters
FET2
FET4












Pre-impregnation




T, ° C.
50
50


Time, min.
30
30


Reaction


Temperature ° C.
50
50


Time, h
1
1


Reaction ethanol, g
1150
1150


Water content, ppm
3464
3550


Catalyst


99% NaOH, g
15.2
15.2


Ethanol, g
150
150


Rapeseed flake, g
1000
1000


Flake size, mm
0.04
0.05


Water, %
2.11
1.75


Fat content1, % DM
48
48.7


AN of fat, mg KOH/g
0.9
0.8


Seed preparation
Method 3b (Two
Method 2


method
flattenings)
Flattener: DAMMAN-



Flattener: HENRY
CROES



Roll type: smooth
Roll type: smooth



Roll spacing:
Roll spacing 0.05 mm



1st flattening:
DryingT: 90° C.



0.4 mm
Drying time: (16 to



2nd flattening:
20 h)



0.04 mm



Drying T: 80° C.



Drying time: 5 h15


Ethanol/seed ratio
1.3
1.3


No of seed-cake
4
4


extractions


Stirring time, min
30
30


T, ° C.
50
50


Purity of extraction
97
99.7


ethanol, %


Final seed-cake


Volatile matter
60.0
58.5


content, %


Fat after reaction1,
5.9
4.7


% DM


of which:


Ethyl esters, %
0.64
94.1


Triglycerides, %
98.7
4.9






1Determined as per standard V03-908







The lower the water content of the ethanol, the better the seed-cake extraction. Absolute ethanol appears to be the best solvent for extraction with the flattened seeds.


3.4.2) Definition of the Treatment Conditions for the Liquid Phase


Operating Mode:


The liquid derived from transesterification was prepared under the following conditions:

    • Seed prepared according to method 3a (two flattenings: 1st roll distance: 0.4 mm, second distance: 0.04 mm)
    • Seed drying at 80° C. for 5 h15 for a volatile matter content of 1.30
    • Impregnation of the flattened dried seeds with ethanol at 50° C. for 30 min (Ethanol/Seed=115/100 weight ratio)
    • Transesterification at 50° C. for 2 h with weight ratios <<NaOH/Ethanol/flattened dried Seed=1.5/130/100>> (discontinuous schedule for 4 kg of flattened dried seeds)
    • Filtering the reaction mixture through filter paper of 11-micron pore size under 0.5 bar N2 to obtain the mother liquor, said L0.


The liquid phase (L0) was neutralized with a solution of sulphuric acid at different concentrations in 97% ethanol.


Table 11 shows that the esters obtained without neutralization have the lowest acid number. On the other hand, the quantity of collected esters is also the lowest. Partial neutralization allows more esters to be obtained. We can neutralize the liquid phase with a 10% sulphuric acid solution.














Table 11a: Preparation conditions for the liquid L0










Parameters
FET1







Pre-impregnation



T, ° C.
50



Time min.
30



Reaction



T, ° C.
50



Time, h
2



Reaction ethanol, g
4600



Water content, ppm
3345



Catalyst



99% NaOH, g
60.8



Ethanol, g
600



Rapeseed flake, g
4000



Flake size, mm
0.04



Water, %
1.35



Fat content1, % DM
48.9



Acid number of fat, mg
0.9



KOH/g



<<Ethanol/Seed>> ratio
1.3











Table 11b: Influence of the concentration of sulphuric acid on neutralization of the


liquid L0












Parameters
N2
N1bis
N2bis
N3
N4





NEUTRALIZATION
Rotavap
Rotavap (1)
Rotavap (1)
Rotavap (1)
Rotavap (1)


(50° C. for 20 min)


L0, g
501.5
250.0
250.0
250.0
250.0


pH
9.90 (20° C.)
Idem
Idem
Idem
Idem


Fat1, %
27.6
27.6
27.6
27.6
27.6


Equivalent basicity, mmol
1.23
1.23
1.23
1.23
1.23


Theoretical cone of H2SO4 %
2.5
0
2.5
5
10


Real cone of H2SO4, %
2.38
0
2.38
4.80
9.55


Equivalent acidity




Quantity of acid solution, g
2.54

1.27
0.63
0.32


initial pH
9.43

9.93

(9.32)


end pH
9.53

9.63
9.90
9.82


EVAPORATION
Rotavap
Rotavap
Rotavap
Rotavap
Rotavap


T, ° C.
80
80
80
80
80


Pressure, mbar
20 (1 h 30)
23 (20 min)
28 (30 min)
21 (30 min)
21 (30 min)


Collected ethanol, g
333.3
167.7
168.6
167.9
166.1


DECANTING
Flask
Centrifuging
Flask
Flask
Flask


T, ° C.
Ambient
Ambient
Ambient
Ambient
Ambient


Time, min
5
5 (4500 rpm)
5
5
5


Glycerine, g
28.5
13.3
11.9
16.2
15.9


RMC (95° C.) glycerine, %
4.04
20.11
8.44
8.22
3.64


Crude esters, g
132.3
66.1
66.7
66.2
67.6


RMC (95° C.) crude esters, %
1.56
1.68
0.44
1.50
2.34


WASHING
Flask
Centrifuging
Flask (3)
Flask (3)
Flask (3)


Ester weight for washing, g
124.8
58.0
60.7
60.2
61.6


T, ° C.
90
Ambient
Ambient
Ambient
Ambient


Stirring
Manual
Manual
Manual
Manual
Manual


Decanting, min
15
5 (4500 rpm)
Slow
Fast
Fast


Number of washings
4
3
6
6
4


Demineralized
about 25
about 11.6
about 12.2
about 12.0
about 12.3


water/washing, g


DRYING
Rotavap
Rotavap
Rotavap
Rotavap
Rotavap


T, ° C.
80
80
80
80
80


Pressure, mbar
26
20
27
26
20


Time, min
30
20
30-40
30
30-40


Final esters, g
121.8
55.6
59.3 (6)
59.5 (6)
60.7 (6)


Acid number, mg of KOH/g
0.48
0.27
0.48
0.45 (7)
0.46






1Determined as per standard V03-908







4) Analysis of the Esters on the Basis of European Criteria

Ethyl esters of rapeseed oil were produced from 20 kg of whole seeds. The implementation conditions for the method in discontinuous mode (closed reactor) are the following:


pre-heating temperature before flattening: 50° C.


flattening on roll flattener: roll spacing of 0.2 mm


drying temperature/time of the flattened seeds: 70° C./12 hours


residual moisture of the flattened seeds after drying: 1.9%


weight ratio alcohol/seeds/catalyst (NaOH): 160/100/1.7%


reaction phase temperature and time: 50° C./30 minutes


washing of seedcake with fresh ethanol: 3 times 100 g ethanol


Purification of ethyl esters:

    • vacuum distillation of ethanol (20 mbar) at 90° C. for 30 minutes
    • decanting and separation of the glycerine
    • washing the esters with 4 times 1500 g distilled water
    • vacuum drying of the ethyl esters (20 mbar) at 110° C. for 30 minutes


The weight of the collected ethyl esters is 7600 g, i.e. an ethyl ester yield of 82%.


The esters thus prepared are analyzed on the basis of the chief criteria of European standard NF EN 14214 applicable to methyl esters intended for fuel applications. The results obtained show that the ethyl esters produced have high purity (>97%) free of contaminants and other sub-products below standard limits (total glycerol, water, ethanol, phosphorus, free fatty acids, mono- di- and triglycerides). They also have a ketane number well above standard specifications (>51), all these results confirming that these ethyl esters can be used as fuels.









TABLE 12







Analysis of the composition of the esters


obtained from rapeseeds using the method of the invention

















Ethyl


Ester




esters


characteristics
Unit
Min
Max
Method
produced















Ester content
% (m/m)
96.5

EN 14103
97.7


Monoglyceride
% (m/m)

0.80
EN 14105
0.56


content


Diglyceride
% (m/m)

0.20
EN 14105
0.09


cobtent


Triglyceride
% (m/m)

0.20
EN 14105
0.11


content


Free glycerol
% (m/m)

0.02
EN 14105
<0.01






EN 14106


Total glycerol
% (m/m)

0.25
EN 14105
0.17


Mass density at
Kg/m3
860
900
EN ISO
870


15° C.



3675






EN ISO






12185


Viscosity at
mm2/s
3.50
5.00
EN ISO
4.73


40° C.



3104


Ketane number

51.0

EN ISO
55






10370


Water content
mg/kg

500
EN ISO
108






12937


Acid number
mg KOH/g

0.50
EN 14104
0.21


Iodine number
g iodine/

120
EN 14111
110.1



100 g


Methyl ester
% (m/m)

12.0
EN 14103
10.2


content of
Absolute


linolenic acid


Ethanol content
% (m/m)

0.2

<0.01


Phosphorus
mg/kg

10.0
EN 14107
<10


content








Claims
  • 1. Method to prepare fatty acid esters which can be used in particular as biodiesel, prepared from whole oilseeds, comprising the following successive steps: a. Pre-heating the whole, non-hulled seeds;b. Flattening the oilseeds with their hull;c. Drying the flattened seeds to obtain a water and volatile matter content of between 0.5 and 2.5%;d. Transesterification by contacting the flattened, dried seeds with an alcohol medium in the presence of a catalyst;e. Separation of the liquid and solid phases resulting from transesterification;f. Neutralizing the liquid phase derived from step e); andg. Removing the alcohol, and separation of the glycerine from the fatty acid esters.
  • 2. Method according to claim 1, wherein the thickness of the flattened seeds lies between 10 μm and 1 mm.
  • 3. Method according to claim 1, wherein the size of the flattened seeds is between 3 and 5 mm.
  • 4. Method according to claim 1, wherein the drying step c) is conducted immediately after the flattening step b), no later than 24 hours after flattening step b).
  • 5. Method according to claim 1, wherein the drying step c) is conducted at a temperature of between 50 and 100° C.
  • 6. Method according to claim 5, wherein the oilseeds are pre-heated to a temperature of between 50 and 55° C. for 5 to 20 min before conducting the flattening step b), optionally under water vapour.
  • 7. Method according to claim 1, wherein flattening of the oilseeds is conducted using rolls distanced less than 0.2 mm apart.
  • 8. Method according to claim 1, wherein flattening of the oilseeds is achieved using smooth rollers, preferably in a single pass.
  • 9. Method according to claim 1, wherein the alcohol medium of the transesterification step d) comprises one or more alcohols chosen from among the C1-C6 alcohols such as methanol or ethanol, optionally in a mixture with one or more aliphatic hydrocarbons.
  • 10. Method according to claim 9, wherein the alcohol medium is ethanol containing a quantity of water less than 5000 ppm.
  • 11. Method according to claim 1, wherein the catalyst at the transesterification step d) is a basic catalyst chosen from among sodium hydroxide, potash, sodium or potassium carbonate or hydrogen carbonate, sodium or potassium carbonate, sodium methylate or sodium or potassium ethanolate.
  • 12. Method according to claim 1, wherein, in discontinuous mode, the flattened seeds are contacted with the alcohol medium before conducting transesterification with the catalyst, wherein, in continuous mode, the flattened seeds are contacted directly with the catalytic solution for a time of 10 to 120 minutes at a temperature of between 40 and 60° C.
  • 13. Method according to claim 1, wherein the weight ratio of catalyst/flattened seeds at the transesterification step c) lies between 0.5/100 and 2/100, and the weight ratio of alcohol/flattened seeds at transesterification step d) lies between 100/100 and 500/100.
  • 14. Method according to claim 1, wherein, in discontinuous mode, the transesterification reaction is conducted at a temperature of between 45 and 55° C., for a time ranging from 10 min to 2 hours.
  • 15. Method according to claim 1, wherein the contacting of the flattened seeds with the alcohol medium at transesterification step d) is conducted under slow stirring or by sprinkling and percolation.
  • 16. Method according to claim 1, wherein in addition, the following steps are conducted: h. extraction of the alcohol from said solid phase derived from step e);i. optional collection of the solid phase;j. filtering and grouping together the liquid phases derived from step e) and h).
  • 17. Method according to claim 1, wherein the extraction step h) is conducted by percolation.
  • 18. Method according to claim 1, wherein the alcohol used at extraction step h) is chosen from among the C1-C6 alcohols.
  • 19. Method according to claim 18, wherein the alcohol is ethanol containing a quantity of water of less than 5000 ppm.
  • 20. Method according to claim 1, wherein the neutralization step f) is conducted using an acid chosen from among sulphuric acid, hydrochloric acid, phosphoric acid, citric acid or acetic acid.
  • 21. Method according to claim 20, wherein the acid at neutralization step f) is added in a quantity leading to a pH of about 10.
  • 22. Method according to claim 20, wherein the acid at neutralization step f) is added to the liquid phase derived from step e) or i) in a quantity of less than 0.04% of the total quantity of the fatty acid esters present in said liquid phase.
  • 23. Method according to claim 1, wherein step g) to remove the alcohol is conducted by evaporation at a temperature of between 50 and 100° C., under a pressure of between 200 and 1000 mbars, until a residual alcohol content of less than 1% is obtained.
  • 24. Method according to claim 1, wherein the separation of the glycerine from the fatty acid esters at step g) is conducted by centrifuging at a temperature of between 60 and 80° C.
  • 25. Method according to claim 1, wherein after step g), the fatty acid esters are washed in water, separated from the washing water notably be decanting or centrifuging, then dried at a temperature of between 90 and 100° C. under a pressure in the order of 200 mbars, until a residual water content of less than 500 ppm is obtained relative to the total dry matter.
  • 26. Method according to claim 1, wherein the seeds are chosen from among the seeds of rape, groundnut, jatropha, castor bean, sesame, olive, sunflower, safflower, soybean, lupin, camelina, cotton, bran, rice.
  • 27. Method to prepare oilseed cake intended for animal feed from the solid phase derived from step e) or i) of the method according to claim 1, wherein it comprises the following steps: 1) Removing the alcohol from said solid phase; and2) Adding the glycerine obtained at step g) of the method according to claim 1.
  • 28. Method to prepare oilseed cake according to claim 27, wherein the solid phase resulting from step 1) is also supplemented with the washing waters.
  • 29. Method to prepare oilseed cake according to claim 27 wherein the removal of the alcohol from said solid phase is conducted mechanically, notably by pressing or spinning, then thermally by entraining with water vapour until a residual water content of less than 500 ppm is obtained relative to the total dry matter.
Priority Claims (1)
Number Date Country Kind
0756716 Jul 2007 FR national
PCT Information
Filing Document Filing Date Country Kind 371c Date
PCT/EP08/59757 7/24/2008 WO 00 6/15/2010