Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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DIRECT EXTRACTION AND/OR PURIFICATION OF HIGH PURITY MALTOL AND
ESSENTIAL OILS BY SUBLIMATION PROCESS
FIELD OF THE INVENTION
The present invention relates to a process for direct extraction and/or
purification of high purity maltol and essential oils by sublimation starting
from a source
material containing maltol.
BACKGROUND OF THE INVENTION
Several methods for the extraction, purification and synthesis of maltol are
known in the art. For instance, it is known to extract maltol from a resin by
pyrolysis of the
wood during distillation process. However, the amount of maltol extracted from
the source
material using any conventional method is very poor. Hence application of
these processes
for the extraction of maltol in a larger scale such as industrial scale is
impossible.
Russian patent No. 2,047,608 teaches a maltol extraction process by
sublimation of the residue which is obtained by a carbonic acid extraction of
AbieS Sibirica
branches. More particularly, the sublimation process is carried out with an
entrainer gas.
However, this process requires the use of silica gel in the preparation of the
source material
that is to be used. The presence of this silica gel seems to be essential for
the e~cacy of the
process.
Russian patent No. 2, 063,420 also discloses an extraction process for maltol
using a source material. This extraction process comprises a distillation and
crystallization
steps, where the maltol is transferred to an aqueous phase for further
crystallization. It is
mentioned that the total yield of the process lies upon the outcome of the
transfer step of the
maltol in the aqueous phase. Hence, this step plays a critical role in this
process.
It has now been found a new process for extracting high purity maltol from
a source material by strictly sublimating and condensing the source material.
Furthermore,
the new process does not require the use of silica gel.
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SUNINIARY OF THE INVENTION
Thus, the object of the present invention is to provide a process for direct
extraction of high purity maltol and essential oils by sublimation from a
source material
containing same.
The process according to the invention comprises the following steps:
a) preparing a source material containing maltol and essential oils by
al) milling a coarse maltol issued from an aqueous or solvent extraction of
branches,
barks and/or needles of a coniferous tree;
a2) drying and/or milling the branches, barks and/or needles of a coniferous
tree; or
a3) recuperating a coarse maltol issued from a solvent extraction of branches,
barks
and/or needles of a coniferous tree, the solvent extraction being in the form
of a resin,
concrete or absolute;
b) sublimating the source material of step a) to obtain a sublimate;
c) recovering and separating maltol and essential oils, by condensing
sublimate from step
b);
d) purifying the crystals obtained from condensation by a treatment with
activated carbon
or simply by rinsing with a solvent.
In the case where the source material is obtained from an extraction procedure
(aqueous or organic), the sublimation process, according to the present
invention, may be
used for purification of the maltol.
This invention will be better understood upon reading the following non
restrictive detailed description of it.
DESCRIPTION OF THE DRAWINGS
Fig. 1 is a block diagram representing the sublimation process carried out
under vacuum condition.
Fig. 2 is a block diagram representing the sublimation process carried out
with an entrainer non-reactive gas.
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DETAILED DESCRIPTION OF THE INVENTION
In the process according to the invention, the starting material in the form
of
finely grounded powder is obtained by milling coarse maltol or by drying
and/or milling
branches, barks and/or needles of a coniferous tree.
The grounded powder obtained therefrom is fed into a stirred and fluidized
bed sublimation reactor 1, via a hopper, a distillation tube having, for
instance, the shape
of a screw or some like. The reactor is provided with:
a) a source of heat, which may be: an electrical heating jacket, a vapour
jacket, a hot oil
bath or other known heating means capable of heating the inside content to up
to 130~C;
b) an agitator, composed of a motor with a reduction gear comprising of at
least two stirring
blades;
c) a distribution grid at the bottom of the reactor, with an appropriate mesh
for fines
retention; and
d) a couple of thermocouples, for measuring temperature at the bottom and the
top of the
reactor.
This reactor is adapted, with minor modifications, for use either in entrainer
gas sublimation and/or in vacuum sublimation. In order to satisfy vacuum
sublimation it
must be able to withstand vacuum pressures which vary preferably from absolute
vacuum
to absolute pressure less than 500 mmHg.
Sublimation of maltol may be carried out under at least one of the following
conditions: vacuum and/or entrainer non-reactive gas. The sublimate resulting
from the
sublimation step is transported to a condenser for the recovering of maltol
and essential oils
in the solid and liquid state respectively.
Recovery of maltol from sublimate may be done by either direct or indirect
cooling depending on the conditions under which the sublimate was formed. More
precisely, direct cooling consists in the condensation of maltol and is
provide by a shower
spray of a cooling agent on the vapour. Hence, the vapour comes in direct and
intimate
contact with the fine liquid spray. The cold water condenses the maltol
contained in the
vapour and then the solubilized maltol is collected in a tank.
Indirect cooling is provided by condensing maltol from vapour by using a
frozen surface. When the vapour comes in contact with the cold surface, the
maltol
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contained therein will condense on the surface. Thus, a scraper is needed to
recover the
maltol.
The recovered maltol crystals obtained from condensation may be further
purified by an activated carbon process or simply by rinsing with a solvent.
The solvent
is preferably one selected from the group consisting of methanol, ethanol,
isopropanol,
acetone, ethyl ether, petroleum ether, hexane and cyclohexane.
The following description is a detailed explanation of the preferred modes for
carrying out the sublimation step b) of the process.
l) EXTRACTION OF MALTOL AND ESSENTIAL OILS UNDER VACUUM
CONDITION
In this embodiment, the extraction is started with a sublimation step b),
which
is done under vacuum condition, as shown in fig. 1. The process is preferably
carried out
at a pressure less than 300 mmHg and at a temperature below 140~C. The outcome
of this
sublimation step has a direct effect on the final yield of the extraction.
The subsequent condensation step e) under vacuum condition is preferably
done by indirect cooling. A particular embodiment of indirect cooling requires
a scraper
to scrap the condensed maltol which was generated on the cooling surface of
the condenser.
The condensation step can also be realized by direct cooling. A particular
embodiment of the direct cooling is shown in Fig. l, in which a shower of
water is provided
by a Venturi (3) which generates the vacuum in the system, or by a scrubber
(3) if the
vacuum is performed by a vacuum pump (5).
The cold water first condense maltol from the vapour and then the solubilized
maltol is collected in a tank (4). The mixture (solubilized essential oil and
maltol) is
separated in two phases: an aqueous phase and an organic phase. The aqueous
phase is
recycled back to the Venturi (3) through pump (6) after being cooled by cooler
(7). The
cooled aqueous phase is used to create the vacuum in the Venturi (3) or to
create the shower
spray of the scrubber. When aqueous solution attains the optimal concentration
of maltol
it can be purified by an activated carbon process or crystallized for further
purification. The
effectiveness of the condensation step will determine the purity of the final
product.
Essential oils are recovered from the organic phase by decantation.
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2) EXTRACTION OF MALTOL AND ESSENTIAL OILS BY ENTRAINER NON-
REACTIVE C"~AS
In this embodiment, shown in figure 2, the extraction step is carried out with
an entrainer non-reactive gas. The entrainer gas (8), must be an inert gas,
which is
preferably selected from a group consisting of air, nitrogen, C02 and mixture
of same.
Depending on the moisture content of the gas, it should be dried appropriately
by a
dehumidifier (9). Before entering the sublimation reactor, the gas must be
preheated by a
heater {10). Heat transfer to the solids is difficult to accomplish and it may
be improved
by a good fluidisation regime and continuous agitation.
The ratio of the entrainer gas in relation to the sublimate will control the
sublimation rate. Too little entrainer will result in a rate that is too low.
On the contrary,
too much entrainer gas will result in a high rate of sublimate production
which in turn will
render condensation of same difficult. Flow rate depends on the cross
sectional area of the
fluidized bed and may be set up between 0.00l to 0.20 lt/min x cm2. The rate
of the
agitation must be controlled to obtain the desired fluidisation regime and to
prevent any cake
or channelling formation. In the same way, the effectiveness of this
sublimation step will
determine the total yield of the final products.
The maltol and essential oils are recovered by transporting the sublimate from
the sublimer ( I ) to the condenser (2), by the entrainer gas, via, for
instance, a jacketed
pipeline. Temperature in line is preferably kept at least at the same
temperature than that
of the sublimer to avoid cold spots where maltol could condense. Condensation
of maltol
and essential oils is preferably done by direct cooling by spraying a cooling
agent (liquid
or gas) to the vapour coming from the sublimer.
Direct cooling by a cool liquid agent, brings the vapours into direct and
intimate contact with a fine liquid spray, namely, a cooling agent which
simultaneously
cools the gas and causes the condensation of maltol and essential oils. In
carrying out the
process, the quantity of liquid used must be sufficient to condense the maltol
contained in
the entrainer gas, but not enough to saturate the gas. The cooling agents that
can be used
are water, methanol, ethanol, isopropyl alcohol, acetone or dichloromethane.
The product
obtained is like a fine powder. Direct cooling by a cool gas agent needs a non
reactive gas
to quench the vapours; the product obtained is snowlike.
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Indirect cooling by using a frozen surface could also be used for the
condensation step but a scraper is needed to recover the product.
The product obtained from direct cooling is easier to handle than the one
deriving from the indirect cooling process.
Temperature for the condenser and the cooling agent must be kept between
25~C and 65~C in order to condense maltol selectively. Lower temperatures
favour
condensation of essentials oils but reduces the purity of maltol. It is
desirable that the walls
of condenser are a few degrees higher than that of the cooling agent to
prevent condensation
or accumulation thereon. The condensation step will determine the purity of
the final
products.
Essential oils are recovered in a cold trap (11), at the exit of the
condenser.
Liquid nitrogen, dry-ice in acetone or any other proper freezing system could
be
successfully used in the trap. The entrainer gas at the exit of the cold trap
is recycled via
a compressor ( 12), to be cooled in a cooler (7) for use in a next batch
reactor. Maltol is
being recovered through the bottom of the condenser.
3) EXTRACTION OF MALTOL AND ESSENTIAL OILS BY VACUUM AND
ENTRAINER GAS
In this embodiment, the extraction step is done under vacuum and entrainer
gas conditions simultaneously. The process is preferably carried out at an
absolute pressure
less than 500 mmHg and at a temperature below 140~C.
The starting material finely grounded, is fed to a stirred sublimation
reactor.
Vacuum is generated by a Venturi or by a pump and a pre-heated non reactive
gas is used
as entrainer gas. Flow rate must be adapted to obtain an absolute pressure of
less than 500
mmHg. Maltol and essential oils are transported from the sublimer to the
condenser via a
hot pipeline, such as a jacketed pipeline.
The subsequent condensation step could be done by one of the direct or
indirect cooling methods previously described:
In a particular embodiment of indirect cooling a frozen surface is used to
condense the vapours and a scraper is used to recover the product.
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In another embodiment, direct cooling is performed with a shower of water
provided by a Venturi which also generates the vacuum or by a scrubber if the
vacuum is
performed by a pump. In this case, maltol is condensed and solubilized by
water for further
purification.
By these methods (vacuum and/or gas entrainer sublimation) preferably more
than 75 ~~ of the maltol contained in the vegetal material can be recuperated
with a high
degree of purity which is close to 100.
EXAMPLE 1
As one example of the vacuum sublimation, 1338 gr of finely grounded and
dry powder of balsam fir needles (Abies balsamea L. , 3. 5 % moisture content
and 1.28 9&
maltol content, collected in Eastern Quebec, Canada) were place in a sublimer
heated by
direct vapour in the jacket. The sublimer was heated to 120~C and the system
was
maintained at a vacuum of 20 - 50 mmHg. At the exit of the condenser a cold
trap of dry-
ice in acetone was conditioned in order to trap essential oils. As a result,
20 gr of essential
oil and 20 gr of water were retained. After one hour of reaction time, white
crystals of
maltol appeared in the condenser (which is a glass coil refrigerated by water
at 25~C).
Two hours later, sublimation was stopped and crystals of maltol were
recuperated by rising
the condenser and lines with hot water. The yield of the maltol recuperated
was found to
be 75 k (12.84 gr). The yield of essential oils recuperated was found to be
47R (20 gr).
EXAMPLE 2
As one example of the gas entrainer sublimation, 878 gr of finely grounded
and dried powder of balsam fir needles (Abies balsamea L. , 3. 5 ~ moisture
content and
1.28 ~ maltol content collected in Eastern Quebec, Canada) were placed in a
sublimer
heated by a vapour jacket at a temperature not less than 120~C. Nitrogen was
used as
entrainer gas preheated also at l20~C by a heat exchanger. The flow rate used
was 0.007
It / min x cm2 and the sublimation was carried out for 7 hours. The entrainer
gas with the
maltol vapours were bubbled in a water trap and essentials oils in an dry-ice
in acetone trap.
After the reaction was stopped, lines were washed and all maltol solutions
were recuperated
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for analysis. The yield of the maltol recuperated was found to be 52% (5.92
gr). The yield
of essential oils recuperated was found to be 30% (8.5 gr).
EXAMPLE 3
As one example of the vacuum and gas entrainer sublimation, 1350 gr of
finely grounded and dry powder of balsam fir needles (Abies balsamea L. , 4.5
% moisture
content and 1.2(9) % maltol content collected in Eastern Quebec, Canada) were
place in a
sublimer heated by direct vapour in the jacket. The sublimer was heated to
l30~C and
vacuum in the system was generated by a shower of water provided by a Venturi.
Nitrogen
was used as entrainer gas at the bottom of the sublimer and the final vacuum
obtained was
50 - 100 mmHg. The shower of water (vacuum) condenses maltol from the vapour.
The
condensed maltol is in the solubilized maltol form and is collected in a tank.
After six
hours of reaction time sublimation was stopped and aqueous solution was
analysed for
maltol content. The yield of the maltol recuperated was found to be 70 % ( 12.
5 gr. )
EXAMPLE (4)
This is an example of vacuum sublimation used as a purification method.
15.02 gr of coarse maltol obtained from an aqueous extraction process ( l 1.18
% moisture
content) were placed in a sublimation reactor and heated to 120~C. The system
was
maintained at a vacuum of 20 - 50 mmHg. After three hours of reaction time,
sublimation
was stopped and crystals of maltol were scrapped from the coil. The yield of
the purified
maltol (99.5 %) was found to be 98.5 % ( 13.1 gr).
