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EP 1 678 114 B1
EUROPEAN PATENT SPECIFICATION
(12)
(45) Date of publication and mention
(51) Int Cl.:
C07C 51/43 (2006.01)
of the grant of the patent:
25.06.2014 Bulletin 2014/26
C07C 55/14 (2006.01)
(86) International application number:
PCT/US2004/033690
(21) Application number: 04794920.1
(87) International publication number:
(22) Date of filing: 14.10.2004
WO 2005/037762 (28.04.2005 Gazette 2005/17)
(54) CRYSTALLIZATION OF ADIPIC ACID FROM ITS SOLUTION IN AQUEOUS NITRIC ACID
KRISTALLISATION VON ADIPINSÄURE AUS DEREN LÖSUNG IN WÄSSRIGER SALPETERSÄURE
CRISTALLISATION D’ACIDE ADIPIQUE A PARTIR DE SA SOLUTION DANS DE L’ACIDE NITRIQUE
AQUEUX
(72) Inventor: SUTRADHAR, Bhagya, Chandra
(84) Designated Contracting States:
AT BE BG CH CY CZ DE DK EE ES FI FR GB GR
HU IE IT LI LU MC NL PL PT RO SE SI SK TR
Wilmington, DE 19808 (US)
(74) Representative: Cockerton, Bruce Roger et al
(30) Priority: 16.10.2003 US 687167
Carpmaels & Ransford LLP
One Southampton Row
London WC1B 5HA (GB)
(43) Date of publication of application:
12.07.2006 Bulletin 2006/28
(56) References cited:
(73) Proprietor: Invista Technologies S.à.r.l.
EP 1 678 114 B1
9000 St. Gallen (CH)
WO-A-01/07389
US-B1- 6 559 339
GB-A- 1 123 514
Note: Within nine months of the publication of the mention of the grant of the European patent in the European Patent
Bulletin, any person may give notice to the European Patent Office of opposition to that patent, in accordance with the
Implementing Regulations. Notice of opposition shall not be deemed to have been filed until the opposition fee has been
paid. (Art. 99(1) European Patent Convention).
Printed by Jouve, 75001 PARIS (FR)
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EP 1 678 114 B1
Description
FIELD OF THE INVENTION
[0001] The invention relates to crystallization of adipic
acid from its solution in aqueous nitric acid and especially
to the recovery of adipic acid from the product of oxidation
of cyclohexanol and cyclohexanone by aqueous nitric
acid
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BACKGROUND OF THE INVENTION
[0002] Adipic acid is commercially produced by the oxidation of cyclohexanol and cyclohexanone by concentrated nitric acid. Initial product recovery and purification
are accomplished through crystallization of the reaction
mixture followed by solid-liquid separation. Additional purification of adipic acid is accomplished through one or
more steps of aqueous recrystallization followed by solidliquid separation. The reaction of cyclohexanol and cyclohexanone with nitric acid produces adipic acid with
several byproducts, e.g. glutaric acid, succinic acid, of
varying concentrations. In order to produce adipic acid
of good quality, a major part of the purification needs to
be accomplished during the initial product recovery
through crystallization of the reaction mixture from the
nitric acid oxidation step.
[0003] For crystallization of adipic acid from the solution obtained from the oxidation of cyclohexanol and cyclohexanone by nitric acid, it has generally been observed that the higher the temperature of crystallization,
the purer the product of crystallization. However, the
mother liquor from crystallization at high temperature
contains a high concentration of adipic acid. In order to
prevent loss of adipic acid with the mother liquor of crystallization, most refining processes in commercial practice require that this crystallization be conducted at a low
temperature, typically below 60 degrees C. As a result,
the product obtained contains substantial impurity that
requires significant additional refining. It would, therefore, be beneficial to have a process to achieve the benefit of high temperature crystallization without excessive
product loss in the mother liquor.
[0004] GB 1,123,514 describes a method for the production of adipic acid wherein the reaction mixture is
worked up by conventional methods to deposit adipic acid in crystalfrom. The mother liquor from which the crystals have been separated may then be concentrated and
cooled to obtain a further amount of adipic acid.
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SUMMARY OF THE INVENTION
[0005] In the present invention, the crystallization is
conducted in a plurality of crystallization stages in decreasing order of operating temperature beginning with
a first crystallizer and ending with a final crystallizer. Each
crystallizer is operated in a continuous mode of operation. A feed solution is introduced in the first crystallizer
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and a product slurry is withdrawn from the final crystallizer. The temperature of the first crystallizer should be
such that it is significantly higher than the temperature
of the final crystallizer, yet a substantial concentration of
solid particles is achieved in the first crystallizer in order
to alleviate the detrimental effect of low solids concentration in the first stage crystallizer.
[0006] The present invention, therefore, is a process
for the crystallization of adipic acid from an adipic acidcontaining oxidation product produced by the nitric acid
oxidation of cyclohexanone and cyclohexanol, said oxidation product comprising adipic acid, glutaric acid, water
and nitric acid, said process comprising,
introducing into a first crystallizer said oxidation product,
said crystallizer providing a first crystallization temperature sufficient to produce a first crystallizer product comprising a first mother liquor and a first harvest of solid
adipic acid crystals;
introducing the first crystallizer product into a second
crystallizer providing a second crystallizer temperature
lower than said first temperature to produce a second
crystallizer product comprising a second mother liquor
and a second harvest of solid adipic acid crystals, said
second mother liquor having a lower concentration of adipic acid than said first mother liquor and said second
crystallizer product having a greater weight percent of
solid adipic acid crystals than said first crystallizer product; and
either
harvesting the solid adipic acid crystals from the second
crystallizer product if the concentration of adipic acid in
solution in the second mother liquor is less than or equal
to a pre-selected concentration in the range of 2 to 12
weight percent of the weight of the second mother liquor,
or,
if the concentration of adipic acid in solution in the second
mother liquor is higher than said pre-selected concentration in the range of 2 to 12 weight percent of the weight
of the second mother liquor, then
introducing the second crystallizer product into one additional crystallizer or a plurality of additional crystallizers
in series providing successively lower crystallization temperatures until a final crystallization product comprising
a final mother liquor and a final harvest of solid adipic
acid crystals is produced in which the concentration of
adipic acid in solution in the final mother liquor is less
than or equal to said pre-selected concentration in the
range of 2 to 12 weight percent of the weight of the final
mother liquor, and
harvesting the solid adipic acid crystals from the final
crystallization product;
wherein at least a part of cooling in the crystallizers is
accomplished by evaporating at a sub-atmospheric pressure a portion of water and nitric acid;
said process characterized in that the first crystallizer provides a first crystallization temperature low enough to
allow enough adipic acid in solution in the oxidation product to crystallize so that the concentration of solid adipic
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acid crystals in the first crystallizer is at least 10 weight
percent based on the combined weight of the mother
liquor and the crystals in the first crystallizer.
BRIEF DESCRIPTION OF THE DRAWING
[0007] The drawing consists of three figures. Figure 1
depicts a block diagram of a process embodying the
present invention involving only two stages in the crystallization process. Figure 2 depicts a block diagram of
one embodiment of the present invention in which at least
a portion of an adipic acid-containing oxidation product
is premixed with a first crystallizer product and then introduced into the first crystallizer. Figure 3 shows a block
diagram of another embodiment of the present invention
in which at least a portion of an adipic acid-containing
oxidation product is premixed with a second crystallizer
product and then introduced into the second crystallizer.
DETAILED DESCRIPTION OF THE INVENTION
[0008] Referring now to Figure 1, there is shown a
block diagram illustrating apparatus that embodies one
embodiment of the present invention involving only two
stages in the crystallization process, namely, a first crystallizer and a second crystallizer.
[0009] An adipic acid-containing oxidation product (12)
produced by the nitric acid oxidation of cyclohexanone
(K) and cyclohexanol (A) is continuously fed into a first
crystallizer (20). In the first crystallizer, the oxidation
product is cooled down to a first crystallization temperature. The cooling action causes crystallization of adipic
acid in solution in the oxidation product that is fed to the
first crystallizer to produce a first crystallizer product comprising a first mother liquor and a first harvest of solid
crystals. The first crystallization temperature should be
low enough to allow enough adipic acid in solution in the
oxidation product to crystallize so that the concentration
of solid crystals in the first crystallizer is at least about 10
weight percent based on the combined weight of the
mother liquor and the crystals in the first crystallizer. A
portion of the first crystallizer product (28) is continuously
withdrawn from the first crystallizer and fed to a second
crystallizer (30).
[0010] The first crystallizer product is further cooled
down in the second crystallizer to a second crystallization
temperature. Cooling action in the second crystallizer
causes crystallization of adipic acid in solution in the first
mother liquor associated with the first crystallizer product
that is fed to the second crystallizer to produce a second
crystallizer product comprising a second mother liquor
and a second harvest of solid crystals. The second crystallization temperature is selected in a way that the concentration of adipic acid in solution in the second mother
liquor is less than the concentration of adipic acid in solution in the first mother liquor and is less than or equal
to a pre-selected concentration in the range of about 2
to 12 weight percent of the weight of the second mother
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liquor. The concentration of solid crystals in the second
crystallizer product is, therefore, higher than the concentration of solid crystals in the first crystallizer product. A
portion of the second crystallizer product (34) is continuously withdrawn from the second crystallizer and is
processed through a solid-liquid separation unit (not
shown) to harvest the solid crystals.
[0011] If the concentration of adipic acid in solution in
the second mother liquor is higher than said pre-selected
concentration, the second crystallizer product stream
(34) can be fed to a final crystallizer or to a plurality of
additional crystallizers in series ending in a final crystallizer (not shown) and providing successively lower crystallization temperatures until a final crystallization product comprising a final mother liquor and a final harvest
of solid crystals is produced. The final crystallization temperature should be selected in a way that the concentration of adipic acid in solution in the final mother liquor is
less than the concentration of adipic acid in solution in
any preceding stage mother liquor and is less than or
equal to said pre-selected concentration in the range of
about 2 to 12 weight percent of the weight of the final
mother liquor. The concentration of solid crystals in the
final crystallizer product is, therefore, higher than the concentration of solid crystals in any preceding crystallizer
product. A portion of the final crystallizer product (not
shown) is continuously withdrawn from the final crystallizer and is processed through a solid-liquid separation
unit (not shown) to harvest the solid crystals.
[0012] Generally it is not advantageous to use more
than three stages of crystallization and in many cases
two stages of crystallization provides adequate benefit.
[0013] The oxidation mixture is generally hot and unsaturated, typically containing about 15 to 25% adipic
acid and typically at a temperature in the range of about
75 to 95 degrees C. Typically about 25 to 45% nitric acid,
about 5 to 15 wt% glutaric acid and about 2 to 10 wt%
succinic acid are present in the oxidation product. On the
basis of combined weight of water and nitric acid only,
the concentration of nitric acid should be in the range of
about 45 to 55 wt%.
[0014] The first crystallizer is an enclosed vessel in
which a constant volume of the first crystallizer product
should be maintained. It is equipped with an agitation
device (21) in order to keep a uniform suspension of solids in the mother liquor in the entire crystallizer. Optionally, a draft tube (not shown) can be installed inside the
crystallizer. Cooling is generally accomplished by evaporating at a sub-atmospheric pressure a portion the water
and nitric acid (i.e. the solvent) contained in the oxidation
product. A continuous flow of vapor (22) leaves the top
of the crystallizer.
[0015] The concentration of solids in the first crystallizer should be at least 10 wt% based on the total weight
of the first crystallizer product. A high solids concentration
is beneficial for crystallizer operation and for purity of final
product. The concentration of solids in the first crystallizer
can be increased by increasing the concentration of ad-
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ipic acid in the oxidation product fed to the first crystallizer, decreasing the first crystallizer temperature, introducing solid adipic acid crystals, e.g. from a second crystallizer product, operating the first crystallizer in a double
draw-off (DDO) mode. In the DDO mode of operation, a
stream of crystallizer content, called overflow, comprising preferentially small particles is withdrawn simultaneously with a stream of crystallizer content, called underflow; comprising particles of all sizes. This action increases concentration of solid particles in the crystallizer.
[0016] The first crystallizer can be a single vessel or
multiple vessels in parallel (not shown). A residence time
of about 15 to 150 minutes (based on the total flow rate
of the oxidation product fed to the first crystallizer) should
be allowed for the first crystallizer (for each vessel if multiple vessels in parallel are used). In order to prevent
flashing of any solvent, there should be adequate liquid
height above the location at which the oxidation product
is introduced in the crystallizer and there should be adequate mixing.
[0017] The second crystallizer is an enclosed vessel
in which a constant volume of the second crystallizer
product should be maintained. It is equipped with an agitation device (31) in order to keep a uniform suspension
of solids in the mother liquor in the entire crystallizer.
Optionally, a draft tube (not shown) can be installed inside
the crystallizer. Cooling is generally accomplished by
evaporating at a sub-atmospheric pressure a portion of
the water and nitric acid (i.e. solvent) contained in the
first crystallizer product. A continuous flow of vapor (32)
leaves the top of the crystallizer. A portion of the second
crystallizer product (34) is continuously withdrawn from
the second crystallizer.
[0018] The concentration of solids in the second crystallizer product is greater than the concentration of solids
in the first crystallizer product, i.e. greater than about 10
wt% based on the total weight of the second crystallizer
product. The second crystallizer temperature should be
in the range of about 30 to 60 degrees C. The concentration of adipic acid in the second mother liquor should
be in the range of about 2 to 12 wt%.
[0019] The second crystallizer can be a single vessel
or multiple vessels in parallel (not shown). A residence
time of about 15 to 150 minutes (based on the total flow
rate of the first crystallizer product fed to the second crystallizer) should be allowed for the second crystallizer (for
each vessel if multiple vessels in parallel are used). In
order to prevent flashing of any solvent, there should be
adequate liquid height above the location at which the
first crystallizer product is introduced in the crystallizer
and there should be adequate mixing.
[0020] The third or any subsequent stage crystallizer
can be designed and operated in a way similar to the
second crystallizer as described above. The preselected
concentration of dissolved adipic acid for the second or
any subsequent mother liquor is based on the value that
is acceptable for further processing, e.g., recycling the
mother liquor.
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[0021] Referring now to Figure 2, there is shown a
block diagram illustrating apparatus that embodies an
embodiment of the present invention in which at least a
portion of the adipic acid-containing oxidation product is
premixed with at least a portion of the first crystallizer
product and then introduced into the first crystallizer. In
this embodiment of the invention, the flow of adipic acidcontaining oxidation product (12) is split into two parts
(14) and (16). Stream (14) is directly fed into the first
crystallizer. Stream (16) is fed into a first feed pre-mixer
vessel (25) where it combines with a flow (24) of the first
crystallizer product. A first premixed feed (26) of the
above combined streams is withdrawn from the first premixer vessel and fed into the first crystallizer.
[0022] The first pre-mixer vessel can be a small, enclosed tank or a section of a pipe or an isolated zone
inside the crystallizer. It can be operated liquid full and
should be designed to accomplish intimate mixing of the
streams. It should be advantageous to combine the
streams in such a ratio that the liquor after mixing is slightly unsaturated. For example, 100g of oxidation product
containing about 20 wt% adipic acid, about 5 wt% glutaric
acid about 5 wt% succinic acid, about 35 wt% nitric acid
and about 35 wt% water at 92 degrees C and 100 g of
mother liquor obtained from first crystallizer product at
60 degrees C containing about 12 wt% adipic acid, about
5 wt% glutaric acid about 5 wt% succinic acid, about 39
wt% nitric acid and about 39 wt% water will produce a
significantly unsaturated liquor upon mixing intimately.
[0023] Together with an unsaturation in liquor, an adequate residence time should be provided so that at least
a portion of the fine particles of adipic acid might dissolve.
For example, for a mixture temperature of about 50 to 75
degrees C, a residence time of about 1 to 5 minutes
should be adequate. Optionally, heat can be provided in
order to accomplish dissolving of fine particles.
[0024] Referring now to Figure 3, there is shown a
block diagram illustrating apparatus that embodies another embodiment of the present invention in which at
least a portion of the adipic acid-containing oxidation
product is premixed with at least a portion of the second
crystallizer product and then introduced into the second
crystallizer. In this embodiment of the invention, the flow
of adipic acid-containing oxidation product (12) is split
into two parts (14) and (18). Stream (14) is directly fed
into the first crystallizer. Stream (18) is fed into a second
feed pre-mixer vessel (35) where it combines with a flow
(36) of the second crystallizer product. A second
premixed feed (38) of the above combined streams is
withdrawn from the second pre-mixer vessel and fed into
the second crystallizer.
[0025] The second pre-mixer vessel can be a small,
enclosed tank or a section of a pipe or an isolated zone
inside the crystallizer. It can be operated liquid full and
should be designed to accomplish intimate mixing of the
streams. It should be advantageous to combine the
streams in such a ratio that the liquor after mixing is slightly unsaturated. In addition, an adequate residence time
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should be provided so that at least a portion of the fine
particles of adipic acid might dissolve. For example, for
a mixture temperature of about 50 to 75 degrees C, a
residence time of about 1 to 5 minutes should be adequate. Optionally, heat can be provided in order to accomplish dissolving of fine particles.
[0026] It may be beneficial to have an arrangement in
which at least a portion of the adipic acid oxidation product is premixed with at least a portion of any crystallizer
product from a crystallizer subsequent to the second
crystallizer and then introduced into the same crystallizer.
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and
harvesting the solid adipic acid crystals from the final
crystallization product;
wherein at least a part of cooling in the crystallizers
is accomplished by evaporating at a sub-atmospheric pressure a portion of water and nitric acid;
said process characterized in that the first crystallizer provides a first crystallization temperature low
enough to allow enough adipic acid in solution in the
oxidation product to crystallize so that the concentration of solid adipic acid crystals in the first crystallizer is at least 10 weight percent based on the combined weight of the mother liquor and the crystals in
the first crystallizer.
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Claims
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1.
A process for the continuous crystallization of adipic
acid from an adipic acid-containing oxidation product
produced by the nitric acid oxidation of cyclohexanone and cyclohexanol, said oxidation product
comprising adipic acid, glutaric acid, water and nitric
acid, said process comprising,
introducing into a first crystallizer said oxidation product, said crystallizer providing a first crystallization
temperature sufficient to produce a first crystallizer
product comprising a first mother liquor and a first
harvest of solid adipic acid crystals;
introducing the first crystallizer product into a second
crystallizer providing a second crystallizer temperature lower than said first temperature to produce a
second crystallizer product comprising a second
mother liquor and a second harvest of solid adipic
acid crystals, said second mother liquor having a
lower concentration of adipic acid than said first
mother liquor and said second crystallizer product
having a greater weight percent of solid adipic acid
crystals than said first crystallizer product; and
either
harvesting the solid adipic acid crystals from the second crystallizer product if the concentration of adipic
acid in solution in the second mother liquor is less
than or equal to a pre-selected concentration in the
range of 2 to 12 weight percent of the weight of the
second mother liquor,
or,
if the concentration of adipic acid in solution in the
second mother liquor is higher than said pre-selected
concentration in the range of 2 to 12 weight percent
of the weight of the second mother liquor, then
introducing the second crystallizer product into one
additional crystallizer or a plurality of additional crystallizers in series providing successively lower crystallization temperatures until a final crystallization
product comprising a final mother liquor and a final
harvest of solid adipic acid crystals is produced in
which the concentration of adipic acid in solution in
the final mother liquor is less than or equal to said
pre-selected concentration in the range of 2 to 12
weight percent of the weight of the final mother liquor,
2.
The process of claim 1 further comprising
(d) withdrawing at least a portion of the first crystallizer product from the first crystallizer,
(e) combining at least a portion of the adipic acidcontaining oxidation product and the first crystallizer product from step (a) to produce a first
premixed feed slurry, and
(f) feeding the first premixed feed slurry to the
first crystallizer.
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3.
The process of claim 1 further comprising
(d) withdrawing at least a portion of the second
crystallizer product from the second crystallizer,
(e) combining at least a portion of the adipic acidcontaining oxidation product and the crystallizer
product from step (a) to produce a second
premixed feed slurry, and
(f) feeding the second premixed feed slurry to
the second crystallizer.
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Patentansprüche
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1.
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Verfahren zum kontinuierlichen Auskristallisieren
von Adipinsäure aus einem adipinsäurehaltigen Oxidationsprodukt, das durch Salpetersäureoxidation
von Cyclohexanon und Cyclohexanol erzeugt wird,
wobei das Oxidationsprodukt Adipinsäure, Glutarsäure, Wasser und Salpetersäure aufweist, wobei
das Verfahren umfasst:
Einbringen des Oxidationsprodukts in einen ersten Kristallisator, wobei der Kristallisator eine
erste Kristallisationstemperatur bereitstellt, die
ausreicht, um ein erstes Kristallisatorprodukt zu
erzeugen, das eine erste Mutterlauge und eine
erste Ernte von festen Adipinsäurekristallen aufweist;
Einbringen des ersten Kristallisatorprodukts in
einen zweiten Kristallisator, der eine zweite Kristallisationstemperatur bereitstellt, die niedriger
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ist als die erste Temperatur, um ein zweites Kristallisatorprodukt zu erzeugen, das eine zweite
Mutterlauge und eine zweite Ernte von festen
Adipinsäurekristallen aufweist, wobei die zweite
Mutterlauge eine niedrigere Adipinsäurekonzentration hat als die erste Mutterlauge und das
zweite Kristallisatorprodukt einen größeren Anteil in Gew.-% an festen Adipinsäurekristallen
aufweist als das erste Kristallisatorprodukt; und
entweder
Ernten der festen Adipinsäurekristalle aus dem
zweiten Kristallisatorprodukt, wenn die Adipinsäurekonzentration in Lösung in der zweiten
Mutterlauge kleiner oder gleich einer vorgewählten Konzentration im Bereich von 2 bis 12 Gew.% des Gewichts der zweiten Mutterlauge ist,
oder,
wenn die Adipinsäurekonzentration in Lösung
in der zweiten Mutterlauge höher ist als die vorgewählte Konzentration im Bereich von 2 bis 12
Gew.-% des Gewichts der zweiten Mutterlauge,
dann
Einbringen des zweiten Kristallisatorprodukts in
einen weiteren Kristallisator oder mehrere weitere, in Reihe geschaltete Kristallisatoren, die
schrittweise niedrigere Kristallisationstemperaturen bereitstellen, bis ein letztes Kristallisationsprodukt produziert wird, das eine letzte Mutterlauge und eine letzte Ernte von festen Adipinsäurekristallen aufweist und in dem die Konzentration von Adipinsäure in Lösung in der letzten Mutterlauge kleiner oder gleich der vorgewählten Konzentration im Bereich von 2 bis 12
Gew.-% des Gewichts der letzten Mutterlauge
ist, und
Ernten der festen Adipinsäurekristalle aus dem
letzten Kristallisationsprodukt;
wobei zumindest ein Teil der Kühlung in den
Kristallisatoren durch Verdampfen eines Teils
von Wasser und Salpetersäure bei einem subatmosphärischen Druck durchgeführt wird;
wobei das Verfahren dadurch gekennzeichnet
ist, dass der erste Kristallisator eine erste Kristallisationstemperatur bereitstellt, die ausreichend niedrig ist, um genügend Adipinsäure in
Lösung in dem Oxidationsprodukt kristallisieren
zu lassen, so dass die Konzentration von festen
Adipinsäurekristallen in dem ersten Kristallisator mindestens 10 Gew.-% beträgt, bezogen auf
das kombinierte Gewicht der Mutterlauge und
der Kristalle im ersten Kristallisator.
2.
pinsäurehaltigen Oxidationsprodukts und des
ersten Kristallisatorprodukts aus Schritt (a), um
eine erste vorgemischte Einsatzaufschlämmung herzustellen, und
(f) Eintragen der ersten vorgemischten Einsatzaufschlämmung in den ersten Kristallisator.
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3.
Verfahren nach Anspruch 1, das ferner umfasst:
(d) Entnahme zumindest eines Teils des zweiten Kristallisatorprodukts aus dem zweiten Kristallisator,
(e) Vereinigen zumindest eines Teil des adipinsäurehaltigen Oxidationsprodukts und des Kristallisatorprodukts aus Schritt (a), um eine zweite
vorgemischte Einsatzaufschlämmung herzustellen, und
(f) Eintragen der zweiten vorgemischten Einsatzaufschlämmung in den zweiten Kristallisator.
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Revendications
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Verfahren nach Anspruch 1, das ferner umfasst:
(d) Entnahme zumindest eines Teils des ersten
Kristallisatorprodukts aus dem ersten Kristallisator,
(e) Vereinigen zumindest eines Teils des adi-
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1.
Procédé pour la cristallisation continue d’acide adipique à partir d’un produit d’oxydation contenant de
l’acide adipique produit par l’oxydation, par acide nitrique, de cyclohexanone et de cyclohexanol, ledit
produit d’oxydation comprenant de l’acide adipique,
de l’acide glutarique, de l’eau et de l’acide nitrique,
ledit procédé comprenant,
l’introduction, dans un premier cristalliseur, dudit
produit d’oxydation, ledit cristalliseur fournissant une
première température de cristallisation suffisante
pour produire un produit du premier cristalliseur comprenant une première liqueur mère et une première
récolte de cristaux d’acide adipique solides;
l’introduction du produit du premier cristalliseur dans
un second cristalliseur fournissant une seconde température de cristallisation inférieure à ladite première
température pour produire un produit du second cristalliseur comprenant une seconde liqueur mère et
une seconde récolte de cristaux d’acide adipique solides, ladite seconde liqueur mère ayant une plus
faible concentration d’acide adipique que ladite première liqueur mère et ledit produit du second cristalliseur ayant un plus grand pourcentage en poids de
cristaux d’acide adipique solides que ledit produit du
premier cristalliseur; et
soit
la récolte des cristaux d’acide adipique solides à partir du produit du second cristalliseur si la concentration d’acide adipique en solution dans la seconde
liqueur mère est inférieure ou égale à une concentration présélectionnée dans la gamme de 2 à 12
pour cent en poids du poids de la seconde liqueur
mère,
soit,
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si la concentration d’acide adipique en solution dans
la seconde liqueur mère est supérieure à ladite concentration présélectionnée dans la gamme de 2 à
12 pour cent en pids du poids de la seconde liqueur
mère, alors
l’introduction du produit du second cristalliseur dans
un cristalliseur supplémentaire ou une pluralité de
cristalliseurs supplémentaires en série fournissant
des températures de cristallisation successivement
plus basses jusqu’à ce qu’un produit de cristallisation
final comprenant une liqueur mère finale et une récolte finale de cristaux d’acide adipique solides soit
produit, dans lequel la concentration d’acide adipique en solution dans la liqueur mère finale est inférieure ou égale à ladite concentration présélectionnée dans la gamme de 2 à 12 pour cent en poids du
poids de la liqueur mère finale, et
la récolte des cristaux d’acide adipique solides à partir du produit de cristallisation final;
dans lequel au moins une partie du refroidissement
dans les cristalliseurs est accomplie en évaporant à
une pression sous-atmosphérique une partie de
l’eau et de l’acide nitrique;
ledit procédé étant caractérisé en ce que le premier
cristalliseur fournit une première température de
cristallisation suffisamment basse pour permettre à
suffisamment d’acide adipique en solution dans le
produit d’oxydation de cristalliser de sorte que la concentration des cristaux d’acide adipique solides dans
le premier cristalliseur est d’au moins 10 pour cent
en poids par rapport au poids combiné de la liqueur
mère et des cristaux dans le premier cristalliseur.
2.
Procédé selon la revendication 1, comprenant en
outre
(d) le soutirage d’au moins une partie du produit
du premier cristalliseur à partir du premier cristalliseur;
(e) la combinaison d’au moins une partie du produit d’oxydation contenant de l’acide adipique
et du produit du premier cristalliseur de l’étape
(a) pour produire une première suspension d’alimentation prémélangée, et
(f) l’alimentation de la première suspension d’alimentation prémélangée dans le premier cristalliseur.
3.
Procédé selon la revendication 1, comprenant en
outre
(d) le soutirage d’au moins une partie du produit
du second cristalliseur à partir du second cristalliseur;
(e) la combinaison d’au moins une partie du produit d’oxydation contenant de l’acide adipique
et du produit du cristalliseur de l’étape (a) pour
produire une seconde suspension d’alimenta-
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tion prémélangée, et
(f) l’alimentation de la seconde suspension d’alimentation prémélangée dans le second cristalliseur.
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20
25
30
35
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45
50
55
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EP 1 678 114 B1
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EP 1 678 114 B1
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EP 1 678 114 B1
REFERENCES CITED IN THE DESCRIPTION
This list of references cited by the applicant is for the reader’s convenience only. It does not form part of the European
patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be
excluded and the EPO disclaims all liability in this regard.
Patent documents cited in the description
•
GB 1123514 A [0004]
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