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EP1427691A1 - Method for making adipic acid crystals and resulting crystals - Google Patents

Method for making adipic acid crystals and resulting crystals

Info

Publication number
EP1427691A1
EP1427691A1 EP02779638A EP02779638A EP1427691A1 EP 1427691 A1 EP1427691 A1 EP 1427691A1 EP 02779638 A EP02779638 A EP 02779638A EP 02779638 A EP02779638 A EP 02779638A EP 1427691 A1 EP1427691 A1 EP 1427691A1
Authority
EP
European Patent Office
Prior art keywords
crystals
adipic acid
ppm
atmosphere
water
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP02779638A
Other languages
German (de)
French (fr)
Inventor
Thierry Gisbert
Jean-Claude Masteau
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Rhodia Operations SAS
Original Assignee
Rhodia Polyamide Intermediates SAS
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Rhodia Polyamide Intermediates SAS filed Critical Rhodia Polyamide Intermediates SAS
Publication of EP1427691A1 publication Critical patent/EP1427691A1/en
Withdrawn legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
    • C07C51/42—Separation; Purification; Stabilisation; Use of additives
    • C07C51/43—Separation; Purification; Stabilisation; Use of additives by change of the physical state, e.g. crystallisation

Definitions

  • the present invention relates to a method for manufacturing adipic acid crystals, as well as the crystals obtained.
  • It relates more concretely to a process for the treatment of adipic acid crystals obtained at the outlet of crystallization in order to obtain crystals which can be stored with a minimum caking ability.
  • Adipic acid is a great intermediate product, especially in the field of polymers and more particularly polyamide and in the synthesis of polyurethanes. It is also used in many other applications as adjuvants in detergent compositions, for example.
  • Adipic acid is generally synthesized by oxidation with nitric acid of a cyclohexanone / cyciohexanol mixture in the presence of oxidation catalysts such as vanadium and copper.
  • the adipic acid is recovered and purified by successive crystallization operations. This crystallization is most often carried out in an aqueous medium.
  • adipic acid is notably separated from the other dicarboxylic acids formed such as glutaric acid, succinic acid.
  • the adipic acid crystals produced at the outlet of crystallization are generally oblong-shaped crystals which can have a very irregular surface.
  • crystals After washing and drying, these crystals are generally stored in large drums, bags or containers and possibly transported to the place of their use, for example installations for manufacturing polyamide or adipate salt of hexamethylene diamine.
  • One of the aims of the present invention is to propose a process allowing the production of adipic acid crystals having a minimum caking capacity when they are stored, to obtain good flowability during the loading or unloading of the containers or container containing them.
  • the invention firstly relates to adipic acid crystals obtained by crystallization or treatment in an aqueous medium which can be stored in containers or receptacles which are impermeable to external humidity for variable durations, without risk of caking, agglomeration. or collage of crystals.
  • the adipic acid crystals of the invention it is easy to empty the storage or transport containers. The implementation of adipic acid is therefore greatly facilitated.
  • the adipic acid crystals are characterized in that the content of exchangeable water in the crystals is less than or equal to 100 ppm, preferably less than 50 ppm.
  • the adipic acid crystals may also contain water called constituting water called constitutive which comes from the inclusion of an amount of crystallization solution during the formation or processing of the crystals.
  • This water is generally not exchangeable, that is to say that it does not migrate, without external action, to the surface of the granule.
  • Another characteristic of the crystals of the invention is the total concentration of water in the granule which must be greater than that in exchangeable water by at least 20 ppm. Preferably, this difference is between approximately 30 ppm and 2000 ppm, advantageously between 50 and 1000 ppm.
  • the amount of water exchangeable by weight of crystals is determined according to the method below:
  • a quantity of powder or crystals to be analyzed of approximately exactly 300 g is placed in a hermetically closed container and having a high seal against the external atmosphere.
  • the volume of the container is equal to 500 ml.
  • a moisture absorbing material constituted by Silicagel crystals (a weight of 2 g weighed approximately exactly) is also placed above or on the mass of powder or crystals to be analyzed. This absorbent material is placed in a watch glass in order to avoid any contact between the different materials.
  • the products to be analyzed and the absorbent material are kept in the hermetically closed container for a period of 24 hours under ambient conditions of temperature and pressure, that is to say under atmospheric pressure and at a temperature between 5 ° C and 25 °. C approx. After 24 hours, the absorbent material is weighed. The difference in weight is corrected by the difference in weight obtained for a blank test carried out in parallel, in which no powder or crystals to be analyzed had been introduced into the container and produced under the same conditions as above.
  • the difference in actual weight is assimilated to a recovery of the exchangeable water contained in the powder or the crystals to be analyzed by the absorbent material. It is expressed in ppm relative to the mass of powder or crystals introduced into the container.
  • the total water concentration in the crystals is determined according to the following analysis protocol:
  • the analyzes are carried out in a DSC7 cell from the company Perkin-Elmer with the following operating conditions:
  • Another object of the present invention is a process for the production of adipic acid crystals having the above characteristics.
  • This process consists in subjecting the adipic acid crystals obtained by crystallization to maturation.
  • This maturation consists in maintaining the crystals at a temperature between 10 ° C and 80 ° C in an atmosphere having an absolute humidity of less than 20 g / Nm 3 , for a period necessary to allow at least the majority of the exchangeable water contained in the crystals to be eliminated.
  • the duration of maturation is determined to obtain a concentration of exchangeable water in the crystals of less than 100 ppm, preferably less than 50 ppm, as indicated above.
  • the method implements means for maintaining the absolute humidity content of the atmosphere in which the crystals are placed at a value of less than 20 g per Nm 3 of gas, for example air.
  • the absolute humidity will advantageously be kept at a value of less than 10 g per Nm 3 of air.
  • Such means are, for example, means for absorbing moisture such as hygroscopic products such as silica gel or the use of a dry gas such as dry air which is periodically or constantly renewed.
  • the crystals can form a fixed bed through which the dry air flow passes or a fluidized bed if the speed of the air flow is sufficient to set the crystals in motion. It is also possible to carry out the stage of maturation of the crystals by placing them in non-leaktight packaging, that is to say allowing at least the moisture contained in the crystals to evaporate in the atmosphere surrounding the packaging or more advantageously allowing only the evaporation of moisture to the outside of the packaging and preventing moisture from entering said packaging.
  • the packages can be placed either in a closed enclosure having an atmosphere with a controlled absolute humidity content and low enough to allow the evaporation of the exchangeable water contained in the crystals, or in an open enclosure with renewal of the atmosphere so that it has an absolute humidity low enough to allow evaporation of the exchangeable water.
  • a closed enclosure having an atmosphere with a controlled absolute humidity content and low enough to allow the evaporation of the exchangeable water contained in the crystals, or in an open enclosure with renewal of the atmosphere so that it has an absolute humidity low enough to allow evaporation of the exchangeable water.
  • adipic acid crystals treated by the process of the invention are generally obtained by crystallization from an aqueous solution of adipic acid.
  • methods of making adipic acid generally include a step of purifying adipic acid which consists of crystallizing the acid from water. This crystallization can be carried out in a single step or in several successive crystallization steps.
  • the adipic acid recovered by filtration or centrifugation is in the form of crystals of more or less large dimensions and of irregular shape.
  • the distribution of crystal sizes can be very wide as well as narrow.
  • the crystals can also be subjected to one or more washes with water. Finally, the crystals are dried and then stored in containers or packaging for transport or food at the place of their use.
  • the adipic acid crystals are subjected after drying to the maturing step described above.
  • the dried crystals can be stored and subjected to the maturing stage before being packaged in the transport containers.
  • the maturing step can also be carried out during the transport of said crystals by using suitable containers, for example a sealed container with respect to external humidity but allowing the evaporation of exchangeable water or maintained in an atmosphere with absolute humidity. low.
  • the stage of maturation of the crystals is carried out before the packaging thereof for transport, this packaging being implemented in sealed containers to avoid the uptake of moisture.
  • the adipic acid crystals obtained by the process of the invention have excellent flowability and a very low clumping ability, the containers can thus be emptied without difficulty, facilitating the control of the feeding of the crystals. adipic acid in the various installations for the use thereof.
  • a storage test in a sealed container of the adipic acid described above and which has not undergone any maturation shows numerous agglomerations of crystals between them preventing easy withdrawal of the crystals from the storage container.
  • the product contained in the column is kept for about 15 hours in the column and then subjected to fluidization by dry air for a few minutes. After keeps this treated acid in a sealed storage container for several weeks, no agglomeration of crystals is observed.
  • the exchangeable water content according to the protocol described above is less than 10 ppm and a total water concentration of 920 ppm
  • Hygrometry sensors placed in the product make it possible to monitor the relative humidity content in the atmosphere of the product. After a few hours of storage, there is a balance between the absolute humidity outside and the absolute humidity inside the bag. Under these storage conditions, no agglomeration of crystals is observed.
  • the exchangeable water content of these crystals is less than 20 ppm and a total water concentration of 910 ppm
  • 20 T of adipic acid crystals with an average size of 320 ⁇ m and having an exchangeable water concentration of 120 ppm are bagged in a container with a bag which is not very permeable to the humidity of gases (less than 1 g / nv7d).
  • the top of the container (with an area of 20m 2 ) is swept by a dry gas (400 Nm 3 / h) for a period of 10 days. After stopping this treatment and closing the bag, the product does not clot and the container can be emptied easily (in less than an hour) after 2 months of transport.
  • the absolute humidity during transport was less than 10g / m3, and the exchangeable water content of the crystals at the outlet of the container was less than 10 ppm and a total water concentration of 890 ppm.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
  • Polyesters Or Polycarbonates (AREA)

Abstract

The invention concerns a method for making adipic acid crystals, and the resulting crystals. More specifically, the invention concerns a method for treating the resulting adipic acid crystals after crystallization to obtain crystals capable of being stored with minimum caking property. Said method comprises a maturing step to partially eliminate the water contained in said crystals.

Description

PROCEDE DE FABRICATION DE CRISTAUX D'ACIDE ADIPIQUE ET CRISTAUX PROCESS FOR PRODUCING ADIPIC ACID CRYSTALS AND CRYSTALS
AINSI OBTENUSTHUS OBTAINED
La présente invention concerne un procédé de fabrication de cristaux d'acide adipique, ainsi que les cristaux obtenus.The present invention relates to a method for manufacturing adipic acid crystals, as well as the crystals obtained.
Elle est relative plus concrètement à un procédé de traitement des cristaux d'acide adipique obtenus en sortie de cristallisation pour obtenir des cristaux pouvant être stockés avec une faculté de mottage minimale.It relates more concretely to a process for the treatment of adipic acid crystals obtained at the outlet of crystallization in order to obtain crystals which can be stored with a minimum caking ability.
L'acide adipique est un grand produit intermédiaire, notamment dans le domaine des polymères et plus particulièrement du polyamide et dans la synthèse des polyuréthanes. Il est également utilisé dans de nombreuses autres applications comme adjuvants dans des compositions détergentes, par exemple.Adipic acid is a great intermediate product, especially in the field of polymers and more particularly polyamide and in the synthesis of polyurethanes. It is also used in many other applications as adjuvants in detergent compositions, for example.
L'acide adipique est en général synthétisé par oxydation par l'acide nitrique d'un mélange cyclohexanone/cyciohexanol en présence de catalyseurs d'oxydation comme le vanadium et le cuivre.Adipic acid is generally synthesized by oxidation with nitric acid of a cyclohexanone / cyciohexanol mixture in the presence of oxidation catalysts such as vanadium and copper.
L'acide adipique est récupéré et purifié par des opérations successives de cristallisation. Cette cristallisation est, le plus souvent, réalisé en milieu aqueux.The adipic acid is recovered and purified by successive crystallization operations. This crystallization is most often carried out in an aqueous medium.
Au cours de ces opérations, l'acide adipique est notamment séparé des autres acides dicarboxyliques formés comme l'acide glutarique, l'acide succinique. Les cristaux d'acide adipique produits en sortie de cristallisation sont généralement des cristaux de forme oblongue pouvant présenter une surface très irrégulière.During these operations, adipic acid is notably separated from the other dicarboxylic acids formed such as glutaric acid, succinic acid. The adipic acid crystals produced at the outlet of crystallization are generally oblong-shaped crystals which can have a very irregular surface.
Après lavage et séchage, ces cristaux sont généralement stockés dans des fûts, sacs ou conteneurs de grandes dimensions et éventuellement transportés sur le lieu de leur utilisation, par exemple les installations de fabrication de polyamide ou de sel adipate d'hexaméthylène diamine.After washing and drying, these crystals are generally stored in large drums, bags or containers and possibly transported to the place of their use, for example installations for manufacturing polyamide or adipate salt of hexamethylene diamine.
Au cours de ce stockage et éventuellement transport, il se produit souvent un mottage, c'est-à-dire un collage de plusieurs cristaux entre eux. Ce phénomène est très pénalisant car il diminue fortement la coulabilité de l'acide adipique lors de Palimentafion des cristaux dans les installations, par exemple de fabrication de polyamides. Le brevet US 5 471 001 propose un procédé particulier de cristallisation de l'acide adipique avec utilisation d'ultra-sons. Les cristaux obtenus présentent une meilleure coulabilité et une faculté de "mottage" plus faible au cours du stockage et du transport.During this storage and possibly transport, there is often a clumping, that is to say a bonding of several crystals between them. This phenomenon is very disadvantageous because it greatly reduces the flowability of adipic acid during the feeding of crystals in installations, for example for the manufacture of polyamides. US Patent 5,471,001 proposes a particular method for crystallizing adipic acid with the use of ultrasound. The crystals obtained have better flowability and a lower "caking" ability during storage and transport.
Il a également été proposé dans la demande de brevet française 2795 721 , un procédé de traitement des cristaux pour modifier la surface de ceux-ci afin de diminuer l'aptitude au mottage.It has also been proposed in French patent application 2795 721, a method of treating crystals to modify the surface thereof in order to reduce the ability to caking.
Ces différents procédés requièrent la mise en œuvre d'étapes de traitement demandant des investissements importants et pouvant occasionner une perte de rendement en acide adipique. Un des buts de la présente invention est de proposer un procédé permettant la fabrication de cristaux d'acide adipique présentant une faculté de mottage minimale quand ils sont stockés, pour obtenir une bonne coulabilité lors du chargement ou du déchargement des conteneurs ou récipient les contenant. A cet effet, l'invention a pour premier objet des cristaux d'acide adipique obtenus par cristallisation ou traitement en milieu aqueux pouvant être stockés dans des conteneurs ou récipients étanches à l'humidité extérieure pendant des durées variables, sans risque de mottage, agglomération ou collage des cristaux. Avec les cristaux d'acide adipique de l'invention, il est facile de vider les conteneurs de stockage ou de transport. La mise en œuvre de l'acide adipique est de ce fait fortement facilitée.These different processes require the implementation of treatment steps requiring significant investment and which may cause a loss of yield of adipic acid. One of the aims of the present invention is to propose a process allowing the production of adipic acid crystals having a minimum caking capacity when they are stored, to obtain good flowability during the loading or unloading of the containers or container containing them. To this end, the invention firstly relates to adipic acid crystals obtained by crystallization or treatment in an aqueous medium which can be stored in containers or receptacles which are impermeable to external humidity for variable durations, without risk of caking, agglomeration. or collage of crystals. With the adipic acid crystals of the invention, it is easy to empty the storage or transport containers. The implementation of adipic acid is therefore greatly facilitated.
Selon l'invention, les cristaux d'acide adipique sont caractérisés en ce que la teneur en eau échangeable dans les cristaux est inférieure ou égale à 100 ppm, de préférence inférieure à 50 ppm.According to the invention, the adipic acid crystals are characterized in that the content of exchangeable water in the crystals is less than or equal to 100 ppm, preferably less than 50 ppm.
Par eau échangeable, il faut comprendre l'eau contenue dans les cristaux et qui migre à la surface de ceux-ci au cours du stockage. Les cristaux d'acide adipique peuvent également contenir de l'eau appelée incluse qui provient de l'inclusion d'une quantité de solution de cristallisation au cours de la formation ou du traitement des cristaux. Cette eau n'est généralement pas échangeable, c'est à dire qu'elle ne migre pas, sans action extérieure, à la surface du granulé. Une autre caractéristique des cristaux de l'invention est la concentration totale en eau du granulé qui doit être supérieure à celle en eau échangeable d'au moins 20 ppm. De préférence, cette différence est comprise entre environ 30 ppm et 2000 ppm, avantageusement entre 50 et 1000 ppm.By exchangeable water, it is necessary to understand the water contained in the crystals and which migrates on the surface of these during storage. The adipic acid crystals may also contain water called inclus which comes from the inclusion of an amount of crystallization solution during the formation or processing of the crystals. This water is generally not exchangeable, that is to say that it does not migrate, without external action, to the surface of the granule. Another characteristic of the crystals of the invention is the total concentration of water in the granule which must be greater than that in exchangeable water by at least 20 ppm. Preferably, this difference is between approximately 30 ppm and 2000 ppm, advantageously between 50 and 1000 ppm.
La quantité d'eau échangeable par poids de cristaux est déterminée selon la méthode ci-dessous :The amount of water exchangeable by weight of crystals is determined according to the method below:
Une quantité de poudre ou cristaux à analyser d'environ exactement 300 g est placée dans un contenant hermétiquement fermé et présentant une étanchéité élevée vis à vis de l'atmosphère extérieure. L.e volume du contenant est égal à 500 ml. Une matière absorbant l'humidité constituée par des cristaux de Silicagel ( un poids de 2 g pesé environ exactement) est également placée au-dessus ou sur la masse de poudre ou cristaux à analyser. Cette matière absorbante est disposée dans un verre de montre afin d'éviter tout contact entre les différentes matières. Les produits à analyser et la matière absorbante sont conservés dans le contenant hermétiquement fermé pendant une durée de 24 heures dans les conditions ambiantes de température et pression, c'est à dire sous pression atmosphérique et à une température comprise entre 5°C et 25°C environ. Après 24 heures, la matière absorbante est pesée. La différence de poids est corrigée par la différence de poids obtenue pour un essai à blanc réalisé en parallèle, dans lequel aucune poudre ou cristaux à analyser n'avait été introduit dans le contenant et réalisé dans les mêmes conditions que précédemment.A quantity of powder or crystals to be analyzed of approximately exactly 300 g is placed in a hermetically closed container and having a high seal against the external atmosphere. The volume of the container is equal to 500 ml. A moisture absorbing material constituted by Silicagel crystals (a weight of 2 g weighed approximately exactly) is also placed above or on the mass of powder or crystals to be analyzed. This absorbent material is placed in a watch glass in order to avoid any contact between the different materials. The products to be analyzed and the absorbent material are kept in the hermetically closed container for a period of 24 hours under ambient conditions of temperature and pressure, that is to say under atmospheric pressure and at a temperature between 5 ° C and 25 °. C approx. After 24 hours, the absorbent material is weighed. The difference in weight is corrected by the difference in weight obtained for a blank test carried out in parallel, in which no powder or crystals to be analyzed had been introduced into the container and produced under the same conditions as above.
La différence de poids réelle, c'est à dire après correction, est assimilée à une reprise de l'eau échangeable contenue dans la poudre ou les cristaux à analyser par la matière absorbante. Elle est exprimée en ppm par rapport à la masse de poudre ou cristaux introduite dans le contenant.The difference in actual weight, that is to say after correction, is assimilated to a recovery of the exchangeable water contained in the powder or the crystals to be analyzed by the absorbent material. It is expressed in ppm relative to the mass of powder or crystals introduced into the container.
La concentration totale en eau dans les cristaux est déterminée selon le protocole d'analyse suivant : Les analyses sont réalisées dans une cellule DSC7 de la société Perkin-Elmer avec les conditions opératoires suivantes :The total water concentration in the crystals is determined according to the following analysis protocol: The analyzes are carried out in a DSC7 cell from the company Perkin-Elmer with the following operating conditions:
• vitesse de montée en température : 5°C/min• temperature rise speed: 5 ° C / min
• porte échantillon : capsule d'aluminium sertie• sample holder: crimped aluminum capsule
• prise d'essai : environ exactement 20 mg • descente en température à -50°C suivie d'une montée à 25°C• test portion: approximately exactly 20 mg • temperature drop to -50 ° C followed by a rise to 25 ° C
Un pic endothermique consécutif à la remontée en température apparaît vers 0°C restituant la transition solide/liquide de l'eau contenu dans les cristaux. La différence d'enthalpie mesurée est traduite en une teneur en eau totale, la concentration en eau totale est exprimée en ppm par rapport à la masse de cristaux. Un autre objet de la présente invention est un procédé de fabrication de cristaux d'acide adipique présentant les caractéristiques ci-dessus.An endothermic peak following the rise in temperature appears at around 0 ° C. restoring the solid / liquid transition of the water contained in the crystals. The difference in enthalpy measured is translated into a total water content, the total water concentration is expressed in ppm relative to the mass of crystals. Another object of the present invention is a process for the production of adipic acid crystals having the above characteristics.
Ce procédé consiste à soumettre les cristaux d'acide adipique obtenus par cristallisation à une maturation. Cette maturation consiste à maintenir les cristaux à une température comprise entre 10°C et 80°C dans une atmosphère présentant une humidité absolue inférieure à 20 g/Nm3, pendant une durée nécessaire pour permettre à au moins la majorité de l'eau échangeable contenue dans les cristaux d'être éliminée. En d'autres termes, la durée de maturation est déterminée pour obtenir une concentration en eau échangeable dans les cristaux inférieure à 100 ppm, de préférence inférieure à 50 ppm, comme indiquée ci-dessus. Selon l'invention, le procédé met en œuvre des moyens pour maintenir la teneur de l'humidité absolue de l'atmosphère dans laquelle sont disposés les cristaux à une valeur inférieure à 20 g par Nm3 de gaz, par exemple d'air. L'humidité absolue sera avantageusement maintenue à une valeur inférieure à 10 g par Nm3 d'air. De tels moyens sont, par exemple, des moyens d'absorption de l'humidité tels que des produits hygroscopiques comme les silicagels ou l'utilisation d'un gaz sec comme de l'air sec qui est périodiquement ou constamment renouvelé.This process consists in subjecting the adipic acid crystals obtained by crystallization to maturation. This maturation consists in maintaining the crystals at a temperature between 10 ° C and 80 ° C in an atmosphere having an absolute humidity of less than 20 g / Nm 3 , for a period necessary to allow at least the majority of the exchangeable water contained in the crystals to be eliminated. In other words, the duration of maturation is determined to obtain a concentration of exchangeable water in the crystals of less than 100 ppm, preferably less than 50 ppm, as indicated above. According to the invention, the method implements means for maintaining the absolute humidity content of the atmosphere in which the crystals are placed at a value of less than 20 g per Nm 3 of gas, for example air. The absolute humidity will advantageously be kept at a value of less than 10 g per Nm 3 of air. Such means are, for example, means for absorbing moisture such as hygroscopic products such as silica gel or the use of a dry gas such as dry air which is periodically or constantly renewed.
A titre d'exempies de modes de réalisation de mise en œuvre de l'étape de maturation conforme à l'invention, on peut citer le stockage des cristaux dans une enceinte avec balayage du ciel de l'enceinte par un flux d'air sec ou envoi à travers la masse des cristaux d'un flux d'air sec. Dans ce dernier mode de réalisation, les cristaux peuvent former un lit fixe à travers lequel passe le flux d'air sec ou un lit fluidisé si la vitesse du flux d'air est suffisante pour mettre en mouvement les cristaux. II est également possible de réaliser l'étape de maturation des cristaux en les disposants dans des emballages non étanches, c'est à dire permettant au moins à l'humidité contenue dans les cristaux de s'évaporer dans l'atmosphère entourant les emballages ou plus avantageusement permettant uniquement l'évaporation de l'humidité vers l'extérieur de l'emballage et interdisant à l'humidité de pénétrer dans ledit emballage. Les emballages peuvent être disposés soit dans une enceinte fermée présentant une atmosphère à teneur en humidité absolue contrôlée et suffisamment faible pour permettre l'évaporation de l'eau échangeable contenue dans les cristaux, soit dans une enceinte ouverte avec renouvellement de l'atmosphère pour que celle-ci présente une humidité absolue suffisamment basse pour permettre l'évaporation de l'eau échangeable. Bien entendu, il est possible de combiner ces différents modes de réalisation sans pour cela sortir du cadre de l'invention.By way of example of embodiments of the maturation step in accordance with the invention, mention may be made of the storage of the crystals in a enclosure with sweeping of the sky of the enclosure by a flow of dry air or sending through the mass of the crystals a flow of dry air. In the latter embodiment, the crystals can form a fixed bed through which the dry air flow passes or a fluidized bed if the speed of the air flow is sufficient to set the crystals in motion. It is also possible to carry out the stage of maturation of the crystals by placing them in non-leaktight packaging, that is to say allowing at least the moisture contained in the crystals to evaporate in the atmosphere surrounding the packaging or more advantageously allowing only the evaporation of moisture to the outside of the packaging and preventing moisture from entering said packaging. The packages can be placed either in a closed enclosure having an atmosphere with a controlled absolute humidity content and low enough to allow the evaporation of the exchangeable water contained in the crystals, or in an open enclosure with renewal of the atmosphere so that it has an absolute humidity low enough to allow evaporation of the exchangeable water. Of course, it is possible to combine these different embodiments without departing from the scope of the invention.
En outre, la description de différents modes de réalisation de mise en œuvre de l'étape de maturation est donnée uniquement à titre illustratif et n'a aucun caractère limitatif. Les cristaux d'acide adipique traités par le procédé de l'invention sont généralement obtenus par cristallisation à partir d'une solution aqueuse d'acide adipique. En outre, les procédés de fabrication d'acide adipique comprennent généralement une étape de purification de l'acide adipique consistant à cristalliser l'acide dans de l'eau. Cette, cristallisation peut être réalisée en une seule étape ou plusieurs étapes successives de cristallisation.In addition, the description of various embodiments of implementation of the maturation step is given only by way of illustration and has no limiting nature. The adipic acid crystals treated by the process of the invention are generally obtained by crystallization from an aqueous solution of adipic acid. In addition, methods of making adipic acid generally include a step of purifying adipic acid which consists of crystallizing the acid from water. This crystallization can be carried out in a single step or in several successive crystallization steps.
L'acide adipique récupéré par filtrafion ou centrifugation est sous forme de cristaux de dimensions plus ou moins importantes et de forme irrégulière. La distribution des tailles de cristaux peut être très large comme étroite.The adipic acid recovered by filtration or centrifugation is in the form of crystals of more or less large dimensions and of irregular shape. The distribution of crystal sizes can be very wide as well as narrow.
Les cristaux peuvent également être soumis à un ou plusieurs lavages par de l'eau. Enfin, les cristaux sont séchés puis stockés dans des récipients ou des emballages en vue de leur transport ou alimentation sur le lieu de leur utilisation.The crystals can also be subjected to one or more washes with water. Finally, the crystals are dried and then stored in containers or packaging for transport or food at the place of their use.
Selon le procédé de l'invention, les cristaux d'acide adipique sont soumis après le séchage à l'étape de maturation décrite ci-dessus. Toutefois, les cristaux séchés peuvent être stockés et soumis à l'étape de maturation avant leur conditionnement dans les conteneurs de transport. L'étape de maturation peut également être réalisée pendant le transport desdits cristaux par utilisation de conteneurs convenables, par exemple conteneur étanche vis à vis de l'humidité extérieure mais permettant l'évaporation de l'eau échangeable ou maintient dans une atmosphère à humidité absolue faible. Selon un mode de réalisation préféré de l'invention, l'étape de maturation des cristaux est réalisée avant le conditionnement de ceux-ci pour le transport, ce conditionnement étant mis en œuvre dans des conteneurs étanches pour éviter la reprise d'humidité.According to the process of the invention, the adipic acid crystals are subjected after drying to the maturing step described above. However, the dried crystals can be stored and subjected to the maturing stage before being packaged in the transport containers. The maturing step can also be carried out during the transport of said crystals by using suitable containers, for example a sealed container with respect to external humidity but allowing the evaporation of exchangeable water or maintained in an atmosphere with absolute humidity. low. According to a preferred embodiment of the invention, the stage of maturation of the crystals is carried out before the packaging thereof for transport, this packaging being implemented in sealed containers to avoid the uptake of moisture.
De ce fait, les cristaux d'acide adipique obtenus par le procédé de l'invention présentent une excellente coulabilité et une très faible faculté de mottage, les conteneurs peuvent être ainsi vidés sans difficulté, facilitant le contrôle de l'alimentation des cristaux d'acide adipique dans les différentes installations d'utilisation de celui-ci..As a result, the adipic acid crystals obtained by the process of the invention have excellent flowability and a very low clumping ability, the containers can thus be emptied without difficulty, facilitating the control of the feeding of the crystals. adipic acid in the various installations for the use thereof.
Il est donc possible de stocker et transporter ces produits pendant des durées longues et dans des conditions d'atmosphère non contrôlées. L'invention sera mieux illustrée au vu des exemples ci-dessous donnés uniquement à titre :It is therefore possible to store and transport these products for long periods of time and in uncontrolled atmosphere conditions. The invention will be better illustrated in the light of the examples below given solely by way of:
Exemple 1Example 1
Dans un contenant de 6 litres, on introduit 4 kg d'acide adipique sous forme de cristaux de taille moyenne 450 μm avec une teneur en eau échangeable de 150 ppm déterminée selon le protocole décrit ci-dessus. Au-dessus du lit on dispose 5 g de desséchant (silicagel) dans un verre de montre. Le contenant est étanche. Après 24h de maturation à température ambiante (20-25°C), on observe que les différents lots traités ne mottent pas, c'est à dire qu'après stockage dans un contenant fermé pendant plusieurs semaines aucune agglomération de cristaux entre eux n'a été constatée. La teneur en eau échangeable des cristaux traités déterminée par le test décrit ci-dessus, est inférieure à 10 ppm et une concentration totale en eau de 900 ppm4 kg of adipic acid are introduced into a 6-liter container in the form of crystals of average size 450 μm with an exchangeable water content of 150 ppm determined according to the protocol described above. Above the bed, 5 g of desiccant (silica gel) are placed in a watch glass. The container is waterproof. After 24 hours of maturation at room temperature (20-25 ° C), it is observed that the different treated batches do not clot, that is to say that after storage in a closed container for several weeks, no agglomeration of crystals between them has been noted. The exchangeable water content of the treated crystals determined by the test described above is less than 10 ppm and a total water concentration of 900 ppm
Exemple 2 comparatifComparative Example 2
Un essai de stockage dans un contenant étanche de l'acide adipique décrit ci- dessus et n'ayant subi aucune maturation montrent de nombreuses agglomérations de cristaux entre eux empêchant un soutirage aisé des cristaux du conteneur de stockage.A storage test in a sealed container of the adipic acid described above and which has not undergone any maturation shows numerous agglomerations of crystals between them preventing easy withdrawal of the crystals from the storage container.
Exemple 3Example 3
Une quantité d'acide adipique de 1.4kg sous forme de cristaux de taille moyenne 330 μm avec une teneur en eau échangeable de 150 ppm déterminée selon le protocole décrit ci-dessus, est introduite dans une colonne en verre (diamètre 75 mm, hauteur 1m) close. Après stockage de quelques heures, les cristaux se sont agglomérés et il est impossible de vider la colonne par écoulement naturel des cristaux.A quantity of adipic acid of 1.4kg in the form of crystals of average size 330 μm with an exchangeable water content of 150 ppm determined according to the protocol described above, is introduced into a glass column (diameter 75 mm, height 1m ) close. After storage for a few hours, the crystals have agglomerated and it is impossible to empty the column by natural flow of the crystals.
Le produit contenu dans la colonne est maintenu pendant 15 heures environ dans la colonne puis soumis à une fluidisation par un air sec pendant quelques minutes. Après maintient de cet acide traité dans un récipient de stockage étanche pendant plusieurs semaines, aucune agglomération de cristaux n'est constatée. La teneur en eau échangeable selon le protocole décrit ci-dessus est inférieure à 10 ppm et une concentration totale en eau de 920 ppmThe product contained in the column is kept for about 15 hours in the column and then subjected to fluidization by dry air for a few minutes. After keeps this treated acid in a sealed storage container for several weeks, no agglomeration of crystals is observed. The exchangeable water content according to the protocol described above is less than 10 ppm and a total water concentration of 920 ppm
Exemple 4 500 kg de cristaux d'acide adipique de taille moyenne 420 μm et de teneur en eau échangeable de 130 ppm déterminée selon le protocole ci-dessus, sont ensachés dans un sac perméable (sac tressé), et laissés dans les conditions ambiantes de température (12-25°C) et de pression (l'hygrométrie relative extérieure varie selon la température de 40 à 50%) [Indiquer les valeurs en humidité absolue].Example 4,500 kg of adipic acid crystals of average size 420 μm and exchangeable water content of 130 ppm determined according to the above protocol, are bagged in a permeable bag (braided bag), and left under the ambient conditions of temperature (12-25 ° C) and pressure (the relative outdoor humidity varies according to the temperature from 40 to 50%) [Indicate the values in absolute humidity].
Des capteurs d'hygrométrie placés dans le produit permettent de suivre la teneur en humidité relative dans l'atmosphère du produit. Après quelques heures de stockage, on observe un équilibre entre l'humidité absolue extérieure et l'humidité absolue à l'intérieur du sac. Dans ces conditions de stockage, aucune agglomération de cristaux n'est constaté. La teneur en eau échangeable de ces cristaux est inférieure à 20 ppm et une concentration totale en eau de 910 ppmHygrometry sensors placed in the product make it possible to monitor the relative humidity content in the atmosphere of the product. After a few hours of storage, there is a balance between the absolute humidity outside and the absolute humidity inside the bag. Under these storage conditions, no agglomeration of crystals is observed. The exchangeable water content of these crystals is less than 20 ppm and a total water concentration of 910 ppm
Au contraire, le stockage dans des sacs étanches aux mêmes conditions de température et humidité conduit à une agglomération importante . L'analyse de la teneur en eau échangeable de ces cristaux montre que celle-ci n'a pas variéOn the contrary, storage in sealed bags at the same temperature and humidity conditions leads to significant agglomeration. Analysis of the exchangeable water content of these crystals shows that it has not varied
Exemple 5Example 5
Réalisation de la maturation et de l'élimination de l'eau échangeable (par balayage de gaz sec) d'un lot d'acide adipique de taille moyenne 320 μm et contenant initialement 120 ppm d'eau échangeable selon le protocole décrit dans ce brevet :Maturation and elimination of exchangeable water (by sweeping dry gas) of a batch of adipic acid of average size 320 μm and initially containing 120 ppm of exchangeable water according to the protocol described in this patent :
20 T de cristaux d'acide adipique de taille moyenne 320 μm et présentant une concentration en eau échangeable de 120 ppm sont ensachées dans un container présentant une sache peu perméable à l'humidité des gaz (inférieure à 1g/nv7j). Le haut du container (d'une surface de 20m2) est balayé par un gaz sec (400 Nm3/h) pendant une durée de 10 jours. Après arrêt de ce traitement et fermeture de la sache, le produit ne motte pas et le container peut être vidé facilement (en moins d'une heure) après 2 mois de transport. L'humidité absolue pendant le transport était inférieure à 10g/m3, et la teneur en eau échangeable des cristaux à la sortie du container inférieure à 10 ppm et une concentration totale en eau de 890 ppm. 20 T of adipic acid crystals with an average size of 320 μm and having an exchangeable water concentration of 120 ppm are bagged in a container with a bag which is not very permeable to the humidity of gases (less than 1 g / nv7d). The top of the container (with an area of 20m 2 ) is swept by a dry gas (400 Nm 3 / h) for a period of 10 days. After stopping this treatment and closing the bag, the product does not clot and the container can be emptied easily (in less than an hour) after 2 months of transport. The absolute humidity during transport was less than 10g / m3, and the exchangeable water content of the crystals at the outlet of the container was less than 10 ppm and a total water concentration of 890 ppm.

Claims

REVENDICATIONS
1. Cristaux d'acide adipique, caractérisés en ce que la concentration en eau échangeable est inférieure à 100 ppm, ladite concentration étant déterminée à partir de 300 g de cristaux d'acide adipique disposés dans une enceinte hermétique préalablement purgée par de l'air sec, avec 2 g d'une matière absorbant l'humidité, ladite enceinte étant maintenue à une température comprise entre 5°C et 25°C pendant 24 heures, la concentration en eau étant égale à la quantité d'eau absorbée par le la matière absorbante ramené à 1 g de cristaux et en ce que la concentration en eau totale est supérieure à celle en eau échangeable d'au moins 20 ppm.1. Adipic acid crystals, characterized in that the concentration of exchangeable water is less than 100 ppm, said concentration being determined from 300 g of adipic acid crystals placed in a hermetic enclosure previously purged with air dry, with 2 g of a moisture-absorbing material, said enclosure being maintained at a temperature between 5 ° C and 25 ° C for 24 hours, the water concentration being equal to the amount of water absorbed by the absorbent material reduced to 1 g of crystals and in that the total water concentration is greater than that in exchangeable water by at least 20 ppm.
2. Cristaux selon la revendication 1 , caractérisés en ce que la concentration en eau précité est inférieure à 50ppm.2. Crystals according to claim 1, characterized in that the aforementioned water concentration is less than 50 ppm.
3. Cristaux selon l'une des revendications 1 ou 2, caractérisés en ce que la différence entre la concentration totale en eau et celle en eau échangeable est comprise entre 30 ppm et 2000 ppm.3. Crystals according to one of claims 1 or 2, characterized in that the difference between the total concentration of water and that of exchangeable water is between 30 ppm and 2000 ppm.
4. Procédé de fabrication de cristaux d'acide adipique selon l'une des revendications précédentes, caractérisé en ce qu'il consiste à soumettre les cristaux d'acide adipique obtenus par cristallisation en milieu aqueux ou traités par une solution aqueuse, à une étape de maturation consistant à maintenir les cristaux à une température comprise entre 10°C et 80°C pendant une durée nécessaire pour obtenir une concentration en eau échangeable inférieure à 100 ppm en présence d'un moyen de maintien de la teneur en humidité absolue dans l'atmosphère autour des cristaux à une valeur inférieure à 20 g/Nm3.4. Method for manufacturing adipic acid crystals according to one of the preceding claims, characterized in that it consists in subjecting the adipic acid crystals obtained by crystallization in an aqueous medium or treated with an aqueous solution, to a step of maturation consisting in maintaining the crystals at a temperature between 10 ° C and 80 ° C for a time necessary to obtain a concentration of exchangeable water of less than 100 ppm in the presence of a means of maintaining the absolute moisture content in l atmosphere around the crystals below 20 g / Nm 3 .
5. Procédé selon la revendication 4 caractérisé en ce que 'il consiste à disposer les cristaux dans une enceinte avec un moyen pour abaisser ou maintenir la teneur en humidité absolue de l'atmosphère de l'enceinte à une valeur inférieure à 20 g/Nm3 pendant une durée suffisante pour obtenir une teneur en humidité absolue constante dans la dite atmosphère. 5. Method according to claim 4 characterized in that 'it consists in placing the crystals in an enclosure with a means for lowering or maintaining the absolute humidity content of the atmosphere of the enclosure to a value less than 20 g / Nm 3 for a sufficient time to obtain a constant absolute moisture content in said atmosphere.
6. Procédé selon la revendication 5, caractérisé en ce que le moyen de maintien ou abaissement de l'humidité absolue de l'atmosphère est un moyen de renouvellement en continu ou périodique de l'atmosphère entourant les cristaux par une atmosphère d'humidité absolue inférieure à 20 g/Nm3.6. Method according to claim 5, characterized in that the means for maintaining or lowering the absolute humidity of the atmosphere is a means of continuous or periodic renewal of the atmosphere surrounding the crystals by an atmosphere of absolute humidity less than 20 g / Nm 3 .
7. Procédé selon la revendication 6, caractérisé en ce que ce renouvellement est obtenu par un balayage avec un flux de gaz d'humidité absolue inférieure à 20 g/Nm3.7. Method according to claim 6, characterized in that this renewal is obtained by scanning with a flow of gas of absolute humidity less than 20 g / Nm 3 .
8. Procédé selon la revendication 6 ou 7, caractérisé en ce que le flux de gaz est alimenté à travers la masse des cristaux.8. Method according to claim 6 or 7, characterized in that the gas flow is supplied through the mass of the crystals.
9. Procédé selon l'une des revendications 6 à 8, caractérisé en ce que le gaz est de l'air sec.9. Method according to one of claims 6 to 8, characterized in that the gas is dry air.
10. Procédé selon l'une des revendications 4 à 9, caractérisé en ce que le moyen de maintien ou abaissement de l'humidité absolue de l'atmosphère comprend un dispositif d'absorption de ladite humidité disposé dans l'enceinte.10. Method according to one of claims 4 to 9, characterized in that the means for maintaining or lowering the absolute humidity of the atmosphere comprises a device for absorbing said humidity arranged in the enclosure.
11. Procédé selon la revendication 10, caractérisé en ce que le dispositif d'absorption comprend un composé absorbant l'humidité.11. Method according to claim 10, characterized in that the absorption device comprises a moisture absorbing compound.
12. Procédé selon l'une des revendications 4 à 11 , caractérisé en ce que le moyen d'abaissement ou de maintien de l'humidité comprend un moyen de renouvellement de l'atmosphère et un dispositif d'absorption de l'humidité.12. Method according to one of claims 4 to 11, characterized in that the means for lowering or maintaining humidity comprises a means for renewing the atmosphere and a device for absorbing moisture.
13. Procédé selon l'une des revendications 4 à 12, caractérisé en ce que l'enceinte contenant les cristaux comprend une enveloppe perméable de l'intérieur vers l'extérieur et imperméable de l'extérieur vers l'intérieur.13. Method according to one of claims 4 to 12, characterized in that the enclosure containing the crystals comprises a permeable envelope from the inside to the outside and impermeable from the outside to the inside.
14. Procédé selon l'une des revendications 4 à 13, caractérisé en ce que l'étape de maturation est mise en œuvre avant le conditionnement des cristaux d'acide adipique dans des containers étanches à l'humidité de l'air environnant pour le stockage ou le transport. 14. Method according to one of claims 4 to 13, characterized in that the maturation step is carried out before the conditioning of the adipic acid crystals in containers sealed against the humidity of the surrounding air for the storage or transportation.
EP02779638A 2001-09-18 2002-09-17 Method for making adipic acid crystals and resulting crystals Withdrawn EP1427691A1 (en)

Applications Claiming Priority (3)

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FR0112039A FR2829761B1 (en) 2001-09-18 2001-09-18 PROCESS FOR PRODUCING ADIPIC ACID CRYSTALS AND CRYSTALS OBTAINED THEREBY
FR0112039 2001-09-18
PCT/FR2002/003167 WO2003024912A1 (en) 2001-09-18 2002-09-17 Method for making adipic acid crystals and resulting crystals

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US6946571B2 (en) * 2003-09-30 2005-09-20 Invista North America S.A.R.L. Drying of adipic acid
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US5471001A (en) * 1994-12-15 1995-11-28 E. I. Du Pont De Nemours And Company Crystallization of adipic acid
FR2795721B1 (en) * 1999-06-29 2003-04-18 Rhone Poulenc Fibres PROCESS FOR THE MANUFACTURE OF ADIPIC ACID
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CN1296339C (en) 2007-01-24
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FR2829761B1 (en) 2004-02-20
KR20040044945A (en) 2004-05-31
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CN1555354A (en) 2004-12-15

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