EP0807107A1 - Process for purifying melamine - Google Patents

Process for purifying melamine

Info

Publication number
EP0807107A1
EP0807107A1 EP96900304A EP96900304A EP0807107A1 EP 0807107 A1 EP0807107 A1 EP 0807107A1 EP 96900304 A EP96900304 A EP 96900304A EP 96900304 A EP96900304 A EP 96900304A EP 0807107 A1 EP0807107 A1 EP 0807107A1
Authority
EP
European Patent Office
Prior art keywords
melamine
pressure
bar
minutes
temperature
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Withdrawn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
EP96900304A
Other languages
German (de)
French (fr)
Inventor
Martin Müllner
Helmut Fingrhut
Lorenzo Canzi
Gerhard Coufal
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.)
Agrolinz Melamin GmbH
Original Assignee
Agrolinz Melamin GmbH
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 Agrolinz Melamin GmbH filed Critical Agrolinz Melamin GmbH
Publication of EP0807107A1 publication Critical patent/EP0807107A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D251/00—Heterocyclic compounds containing 1,3,5-triazine rings
    • C07D251/02—Heterocyclic compounds containing 1,3,5-triazine rings not condensed with other rings
    • C07D251/12—Heterocyclic compounds containing 1,3,5-triazine rings not condensed with other rings having three double bonds between ring members or between ring members and non-ring members
    • C07D251/26—Heterocyclic compounds containing 1,3,5-triazine rings not condensed with other rings having three double bonds between ring members or between ring members and non-ring members with only hetero atoms directly attached to ring carbon atoms
    • C07D251/40—Nitrogen atoms
    • C07D251/54—Three nitrogen atoms
    • C07D251/62—Purification of melamine
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D251/00—Heterocyclic compounds containing 1,3,5-triazine rings
    • C07D251/02—Heterocyclic compounds containing 1,3,5-triazine rings not condensed with other rings
    • C07D251/12—Heterocyclic compounds containing 1,3,5-triazine rings not condensed with other rings having three double bonds between ring members or between ring members and non-ring members
    • C07D251/26—Heterocyclic compounds containing 1,3,5-triazine rings not condensed with other rings having three double bonds between ring members or between ring members and non-ring members with only hetero atoms directly attached to ring carbon atoms
    • C07D251/40—Nitrogen atoms
    • C07D251/54—Three nitrogen atoms
    • C07D251/56—Preparation of melamine
    • C07D251/60—Preparation of melamine from urea or from carbon dioxide and ammonia

Definitions

  • a large number of processes for the production of me laminate are already known from the literature.
  • a preferred starting material is urea, which is converted to melamine, ammonia and CO2 either at high pressure and non-catalytically or at low pressure and using a catalyst. It is also known that these by-products, in particular high-pressure processes, produce various by-products or impurities, such as, for example, Meiern, Melam, Ammeiin, Ammelid or Ureidomelamin, which impair the purity of the melamine.
  • the melamine produced by a high-pressure process is worked up, for example, in accordance with US Pat. No. 3,1 16,294 (Montecatini) by separating the CO2 and NH exhaust gases from the liquid melamine, which is then treated in countercurrent with NH3 in order to remove dissolved CO2 collected in another reactor and left for a certain time.
  • the separation column and the second reactor are kept under the same temperature and pressure conditions as the urea reactor, namely at 250 to 500 ° C and a pressure of about 40 to 150 bar.
  • the melamine thus obtained is removed from the second reactor and rapidly cooled by quenching with water or by mixing with cold gases.
  • the purity of melamine obtained by this process is not sufficient for many applications, for example in the production of melamine-formaldehyde resins for surface coatings, since the Meier content in particular is too high.
  • impurities such as Meier and melam are insoluble or sparingly soluble in water and aqueous alkali solutions, so that when melamine is recrystallized, for example following the Montecatini workup, these compounds are difficult and with melamine losses from the cleansing melamine can be removed.
  • the present invention therefore relates to a process for the purification of melamine, which is characterized in that contaminated melamine is left for 5 minutes to 20 hours at an ammonia partial pressure of 150 to 400 bar in a temperature range of 280 to 430 ° C. whereupon it is first rapidly cooled to room temperature and then relaxed or simultaneously cooled and relaxed and pure melamine is obtained in powder form.
  • the process according to the invention is suitable for the purification of melamine, which is obtained in any process known from the prior art and in particular contains impurities such as Meier and melam.
  • the melamine to be purified in the case that it is in crystalline form or as a powder, is first heated to a temperature within the temperature range from 280 to 430 ° C., preferably to or above the melting point of melamine to 400 ° C., and at an ammonia partial pressure of over 1 50 bar for a certain time in this area.
  • the melamine to be purified is already in the form of a melt or a liquid phase, such as, for example, following a high-pressure reactor for melamine synthesis by reacting with urea, this warm-up phase can be omitted and the temperature of the melt is brought to the desired value within the temperature range defined above.
  • the temperature of the melamine to be purified can be kept constant during the dwell time of the melamine, but it can also be changed within the temperature range defined above. For example, the temperature can be reduced or increased continuously or stepwise within the limits of the temperature range.
  • the residence time can vary within a wide range. It depends mainly on the desired final level of impurities, as well as on the ammonia partial pressure and on economic factors, and is between 5 minutes and 20 hours, preferably between 10 minutes and 10 hours, particularly preferably between 30 minutes and 4 Hours. Longer residence times are also possible if desired.
  • the ammonia partial pressure can also vary within a wide range and is between 150 and 400 bar. An ammonia partial pressure of up to 360 bar is preferably set, particularly preferably up to 300 bar.
  • Melamine is obtained by the process according to the invention in crystalline form or as a powder and in particular has a significantly reduced content of Meier and Melam.
  • the process according to the invention can be carried out batchwise or continuously.
  • the method according to the invention can be coupled to any melamine process known from the prior art.
  • Aus ⁇ method of the invention with one of the known from the prior art high-pressure processes, such as in Ullmann's Encyclopedia of Industrial Chemistry, 5 tn Edition, Vol. A-16, pp 174-179 beschrie ⁇ ben, combined.
  • the process according to the invention is particularly preferably carried out following known work-up steps for the high-pressure processes. These workup steps include a) separating the NH3 / CO 2 gas mixture obtained in the reaction of urea from the liquid melamine, and b) reducing the CO2 dissolved in the melamine by introducing NH3.
  • workup steps are described, for example, in US Pat. No. 3,116,294.
  • the process according to the invention can thus connect directly to the reactor for the urea conversion or can be carried out following the workup steps described above, the workup being able to comprise both steps a) in combination with b) and only one of these steps.
  • the autoclave was then quickly heated to a temperature T by immersion in a heat transfer medium and allowed to remain at this temperature for t minutes. Thereafter, the autoclave was quickly cooled by immersing it in cold water and then relaxed. The melamine cleaned in this way was examined for the final content of impurities, in particular Meier.
  • the process parameters such as weight of melamine (EW), pressure p, time t, temperature T, initial content of Meiern (MEo), Melam (MAo), Ammeiin (ANo), Ammelid (ADo), and ureidomelamine (UMo), as well as the The final content of Meiern (ME), Melam (MA), Ureidomelamin (UM) and partly Ammeiin (AN) and Ammelid (AD) are shown in Table 1.

Abstract

A process for purifying melamine in which unpurified melamine is kept for from 5 minutes to 20 hours at a partial ammonia pressure of 150 to 400 bar within a temperature range from 280 to 430 °C, whereafter it is first rapidly cooled to room temperature and then the pressure is released, or it is cooled and the pressure is released simultaneously, pure melamine being obtained in powder form.

Description

Verfahren zur Reinigung von MelaminProcess for cleaning melamine
Aus der Literatur ist bereits eine Vielzahl von Verfahren zur Herstellung von Me¬ lamin bekannt. Ein bevorzugtes Ausgangsmaterial ist dabei Harnstoff, der entweder bei hohem Druck und nichtkatalytisch oder bei niedrigem Druck und unter Verwendung eines Katalysators zu Melamin, Ammoniak und CO2 umgesetzt wird. Es ist auch bekannt, daß bei diesen Verfahren, insbesondere bei den Hochdruckverfahren, verschiedene Nebenprodukte bzw. Verunreinigungen, wie beispielsweise Meiern, Melam, Ammeiin, Ammelid oder Ureidomelamin, entstehen, die die Reinheit des Melamins beeinträchtigen.A large number of processes for the production of me laminate are already known from the literature. A preferred starting material is urea, which is converted to melamine, ammonia and CO2 either at high pressure and non-catalytically or at low pressure and using a catalyst. It is also known that these by-products, in particular high-pressure processes, produce various by-products or impurities, such as, for example, Meiern, Melam, Ammeiin, Ammelid or Ureidomelamin, which impair the purity of the melamine.
Die Aufarbeitung des durch ein Hochdruckverfahren hergestellten Melamins er¬ folgt beispielsweise nach US 3,1 16,294 (Montecatini) durch Abtrennung der CO2- und NH -Abgase vom flüssigen Melamin, das anschließend, um noch gelöstes CO2 zu entfernen, im Gegenstrom mit NH3 behandelt, in einem weiteren Reaktor gesammelt und eine bestimmte Zeit darin verweilen gelassen wird. Die Trennkolonne und der zweite Reaktor werden dabei unter den gleichen Temperatur- und Druckbedingungen wie der Harnstoffreaktor, nämlich bei 250 bis 500°C und einem Druck von etwa 40 bis 150 bar, gehalten. Das so erhaltene Melamin wird aus dem zweiten Reaktor entnommen und durch Abschrecken mit Wasser oder durch Mischen mit kalten Gasen rasch abgekühlt. Die Reinheit von Melamin, das durch dieses Verfahren gewonnen wird, ist jedoch für viele Anwendungen, etwa bei der Herstellung von Melamin- Formaldehydharzen für Oberflächenbeschichtungen, nicht ausreichend, da insbesondere der Gehalt an Meiern zu hoch ist. Wie aus CH 345.894 bekannt ist, sind Verunreinigungen wie Meiern und Melam in Wasser und wäßrigen Alkalilösungen unlöslich bzw. schwer löslich, sodaß diese Verbindungen bei einer Umkristallisation von Melamin, beispielsweise im Anschluß an die Aufarbeitung gemäß Montecatini, nur schwer und mit Melaminverlusten aus dem zu reinigenden Melamin entfernt werden können.The melamine produced by a high-pressure process is worked up, for example, in accordance with US Pat. No. 3,1 16,294 (Montecatini) by separating the CO2 and NH exhaust gases from the liquid melamine, which is then treated in countercurrent with NH3 in order to remove dissolved CO2 collected in another reactor and left for a certain time. The separation column and the second reactor are kept under the same temperature and pressure conditions as the urea reactor, namely at 250 to 500 ° C and a pressure of about 40 to 150 bar. The melamine thus obtained is removed from the second reactor and rapidly cooled by quenching with water or by mixing with cold gases. However, the purity of melamine obtained by this process is not sufficient for many applications, for example in the production of melamine-formaldehyde resins for surface coatings, since the Meier content in particular is too high. As is known from CH 345.894, impurities such as Meier and melam are insoluble or sparingly soluble in water and aqueous alkali solutions, so that when melamine is recrystallized, for example following the Montecatini workup, these compounds are difficult and with melamine losses from the cleansing melamine can be removed.
Aufgabe der vorliegenden Erfindung war es demnach ein Verfahren zu finden, bei welchem der Gehalt an Verunreinigungen, insbesondere an den in Wasser oder in wäßrigen Alkalilösungen unlöslichen oder schwer löslichen Verunreinigungen, ohne Melaminverluste deutlich reduziert werden kann. Unerwarteterweise konnte diese Aufgabe durch ein Verfahren gelöst werden, bei welchem verunreinigtes Melamin eine gewisse Zeit bei einem Ammoniakpar¬ tialdruck von über 1 50 bar bei einer Temperatur von über 280°C verweilen ge¬ lassen und anschließend rasch abgekühlt wird .It was therefore an object of the present invention to find a process in which the content of impurities, in particular impurities which are insoluble or poorly soluble in water or in aqueous alkali solutions, can be significantly reduced without loss of melamine. This task was unexpectedly achieved by a process in which contaminated melamine was allowed to remain for a certain time at an ammonia partial pressure of over 150 bar at a temperature of over 280 ° C. and was then cooled rapidly.
Gegenstand der vorliegenden Erfindung ist daher ein Verfahren zur Reinigung von Melamin, das dadurch gekennzeichnet ist, daß verunreinigtes Melamin für 5 Minuten bis zu 20 Stunden bei einem Ammoniakpartialdruck von 1 50 bis 400 bar in einem Temperaturbereich von 280 bis 430°C verweilen gelassen wird, worauf zuerst rasch auf Raumtemperatur abgekühlt und anschließend entspannt oder gleichzeitig abgekühlt und entspannt wird und reines Melamin in Pulverform erhalten wird.The present invention therefore relates to a process for the purification of melamine, which is characterized in that contaminated melamine is left for 5 minutes to 20 hours at an ammonia partial pressure of 150 to 400 bar in a temperature range of 280 to 430 ° C. whereupon it is first rapidly cooled to room temperature and then relaxed or simultaneously cooled and relaxed and pure melamine is obtained in powder form.
Das erfindungsgemäße Verfahren eignet sich zur Reinigung von Melamin, das in einem beliebigen aus dem Stand der Technik bekannten Prozeß anfällt und insbesondere Verunreinigungen wie Meiern und Melam enthält. Das zu reinigende Melamin wird, im Falle, daß es in kristalliner Form oder als Pulver vorliegt, zuerst auf eine Temperatur innerhalb des Temperaturbereiches von 280 bis 430°C vorzugsweise auf oder über den Schmelzpunkt von Melamin bis 400°C, erwärmt und bei einem Ammoniakpartialdruck von über 1 50 bar für eine bestimmte Zeit in diesem Bereich verweilen gelassen. Liegt das zu reinigende Melamin bereits als Schmelze bzw. als Flüssigphase, wie beispielsweise im Anschluß an einen Hockdruckreaktor zur Melaminsynthese durch Harnstoffumsetzung vor, so kann diese Aufwärmphase entfallen, und die Temperatur der Schmelze wird auf den gewünschten Wert innerhalb des oben definierten Temperaturbereich gebracht.The process according to the invention is suitable for the purification of melamine, which is obtained in any process known from the prior art and in particular contains impurities such as Meier and melam. The melamine to be purified, in the case that it is in crystalline form or as a powder, is first heated to a temperature within the temperature range from 280 to 430 ° C., preferably to or above the melting point of melamine to 400 ° C., and at an ammonia partial pressure of over 1 50 bar for a certain time in this area. If the melamine to be purified is already in the form of a melt or a liquid phase, such as, for example, following a high-pressure reactor for melamine synthesis by reacting with urea, this warm-up phase can be omitted and the temperature of the melt is brought to the desired value within the temperature range defined above.
Die Temperatur des zu reinigenden Melamins kann während der Verweilzeit des Melamins konstant gehalten werden, sie kann jedoch auch innerhalb des oben definierten Temperaturbereiches verändert werden. So kann die Temperatur bei¬ spielsweise kontinuierlich oder stufenweise innerhalb der Grenzen des Tempera¬ turbereiches abgesenkt bzw. erhöht werden. Die Verweilzeit kann in einem wei¬ ten Bereich variieren. Sie hängt hauptsächlich vom gewünschten Endwert an Verunreinigungen, sowie vom Ammoniakpartialdruck und von wirtschaftlichen Faktoren ab und liegt zwischen 5 Minuten und 20 Stunden, bevorzugt zwischen 10 Minuten und 10 Stunden, besonders bevorzugt zwischen 30 Minuten bis 4 Stunden. Längere Verweilzeiten sind gewünschtenfalls auch möglich. Der Am¬ moniakpartialdruck kann ebenfalls in einem großen Bereich variieren und liegt zwischen 150 und 400 bar. Bevorzugt wird ein Ammoniakpartialdruck bis 360 bar, besonders bevorzugt bis 300 bar eingestellt. Es ist auch möglich den Druck während der Verweilzeit zu variieren. Weiters ist es möglich, andere unter den Reaktionsbedingungen inerte Gase, z. B. Stickstoff, zuzumischen. Nach Ende der Verweilzeit kann, je nach den technischen Gegebenheiten, zuerst abgekühlt und dann entspannt, oder gleichzeitig entspannt und abgekühlt werden. Das Abkühlen auf Raumtemperatur erfolgt beispielsweise durch Abschrecken mit ei¬ nem kalten flüssigen Medium, etwa mittels Wasser oder flüssigem Ammoniak oder durch Mischen mit kalten Gasen.The temperature of the melamine to be purified can be kept constant during the dwell time of the melamine, but it can also be changed within the temperature range defined above. For example, the temperature can be reduced or increased continuously or stepwise within the limits of the temperature range. The residence time can vary within a wide range. It depends mainly on the desired final level of impurities, as well as on the ammonia partial pressure and on economic factors, and is between 5 minutes and 20 hours, preferably between 10 minutes and 10 hours, particularly preferably between 30 minutes and 4 Hours. Longer residence times are also possible if desired. The ammonia partial pressure can also vary within a wide range and is between 150 and 400 bar. An ammonia partial pressure of up to 360 bar is preferably set, particularly preferably up to 300 bar. It is also possible to vary the pressure during the dwell time. Furthermore, it is possible to use other gases which are inert under the reaction conditions, e.g. B. nitrogen to mix. At the end of the dwell time, depending on the technical circumstances, you can first cool down and then relax, or you can relax and cool down at the same time. The cooling to room temperature takes place, for example, by quenching with a cold liquid medium, for example using water or liquid ammonia, or by mixing with cold gases.
Melamin wird durch das erfindungsgemäße Verfahren in kristalliner Form bzw. als Pulver erhalten und weist insbesondere einen deutlich reduzierten Gehalt an Meiern und Melam auf.Melamine is obtained by the process according to the invention in crystalline form or as a powder and in particular has a significantly reduced content of Meier and Melam.
Das erfindungsgemäße Verfahren kann sowohl diskontinuierlich als auch kontinuierlich durchgeführt werden.The process according to the invention can be carried out batchwise or continuously.
Das erfindungsgemäße Verfahren kann an jeden beliebigen, aus dem Stand der Technik bekannten Melaminprozeß gekoppelt werden. In einer bevorzugten Aus¬ führungsform wird das erfindungsgemäße Verfahren mit einem der aus dem Stand der Technik bekannten Hochdruckprozesse, wie etwa in Ullmann's Ency- clopedia of Industrial Chemistry, 5tn Edition, Vol. A-16, pp 174-179 beschrie¬ ben, kombiniert. Besonders bevorzugt wird das erfindungsgemäße Verfahren im Anschluß an bereits bekannte Aufarbeitungsschritte der Hochdruckverfahren durchgeführt. Diese Aufarbeitungsschritte beinhalten a) Abtrennen des bei der Umsetzung von Harnstoff erhaltenen NH3/Cθ2-Gas- gemisches vom flüssigen Melamin, sowie b) Reduktion des im Melamin gelösten CO2 durch Einbringen von NH3. Diese Aufarbeitungsschritte sind beispielsweise in US 3, 1 16,294 beschrieben. Das erfindungsgemäße Verfahren kann dabei somit direkt an den Reaktor für die Harnstoffumsetzung anschließen oder im Anschluß an die oben beschriebenen Aufarbeitungsschritte durchgeführt werden, wobei die Aufarbeitung sowohl die Schritte a) in Kombination mit b), als auch nur einen dieser Schritte umfassen kann. Beispiel 1 - 7The method according to the invention can be coupled to any melamine process known from the prior art. In a preferred execution form Aus¬ method of the invention with one of the known from the prior art high-pressure processes, such as in Ullmann's Encyclopedia of Industrial Chemistry, 5 tn Edition, Vol. A-16, pp 174-179 beschrie¬ ben, combined. The process according to the invention is particularly preferably carried out following known work-up steps for the high-pressure processes. These workup steps include a) separating the NH3 / CO 2 gas mixture obtained in the reaction of urea from the liquid melamine, and b) reducing the CO2 dissolved in the melamine by introducing NH3. These workup steps are described, for example, in US Pat. No. 3,116,294. The process according to the invention can thus connect directly to the reactor for the urea conversion or can be carried out following the workup steps described above, the workup being able to comprise both steps a) in combination with b) and only one of these steps. Example 1-7
In einen Miniautoklaven mit 10 ml Volumen wurde eine bestimmte Menge (EW) an Melamin mit einem definierten Anfangsgehalt an Verunreinigungen sowie die zur Aufrechterhaltung eines bestimmten Druckes p nötige Ammoniakmenge ein¬ gebracht.A certain amount (EW) of melamine with a defined initial content of impurities and the amount of ammonia required to maintain a certain pressure p were introduced into a mini-autoclave with a volume of 10 ml.
Anschließend wurde der Autoklav auf eine Temperatur T durch Eintauchen in ein Wärmeträgermedium rasch aufgeheizt und t Minuten bei dieser Temperatur verweilen gelassen. Danach wurde der Autoklav rasch durch Eintauchen in kaltes Wasser abgekühlt und dann entspannt. Das so gereinigte Melamin wurde auf den Endgehalt an Verunreinigungen, insbesondere an Meiern, untersucht. Die Verfahrensparameter, wie Einwaage an Melamin (EW), Druck p, Zeit t, Temperatur T, Anfangsgehalt an Meiern (MEo), Melam (MAo), Ammeiin (ANo), Ammelid (ADo), und Ureidomelamin (UMo), sowie der Endgehalt an Meiern (ME), Melam (MA), Ureidomelamin (UM) und teilweise an Ammeiin (AN) und Ammelid (AD) sind aus Tabelle 1 ersichtlich.The autoclave was then quickly heated to a temperature T by immersion in a heat transfer medium and allowed to remain at this temperature for t minutes. Thereafter, the autoclave was quickly cooled by immersing it in cold water and then relaxed. The melamine cleaned in this way was examined for the final content of impurities, in particular Meier. The process parameters, such as weight of melamine (EW), pressure p, time t, temperature T, initial content of Meiern (MEo), Melam (MAo), Ammeiin (ANo), Ammelid (ADo), and ureidomelamine (UMo), as well as the The final content of Meiern (ME), Melam (MA), Ureidomelamin (UM) and partly Ammeiin (AN) and Ammelid (AD) are shown in Table 1.
Bsp . EW p T t MEo ME MAo MA UMo UM ANo AN ADo ADE.g . EW p T t MEo ME MAo MA UMo UM ANo AN ADo AD
(mg) (bar) (°C) (min) ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm(mg) (bar) (° C) (min) ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm
1 268 350 290 10 5600 110018300320 10600170 -1 268 350 290 10 5600 110018300 320 10600170 -
2 268 350 290 100 5600 150 18300220 10600290 - - - -2 268 350 290 100 5600 150 18300 220 10600 290 - - - -
3 80 350 370 180 1300090 2200016003300 710 6700350 10001503 80 350 370 180 1300090 2200016003300 710 6700350 1000150
4 51 250 400 180 13000130 2200020003300 820 6700400 10001204 51 250 400 180 13000130 2200020003300 820 6700400 1000120
5 159 250 340 100801300040 2200012003300 410 6700290 1000505 159 250 340 100801300040 2200012003300 410 6700290 100050
6 176 250 310 960 1300040 22000930 3300 420 6700460 1000506 176 250 310 960 1300040 22000930 3300 420 6700460 100050
7 159 250 340 10 13000330 2200036003300 590 6700830 10001507 159 250 340 10 13000330 2200036003300 590 6700830 1000150
8 126 200 330 100 12000190 - -8 126 200 330 100 12000190 - -
9 115 200 400 60 16000980 - - -9 115 200 400 60 16000 980 - - -
10 113 200 370 100 1200045010 113 200 370 100 12000450
11 90 150 370 240 16000670 - - -11 90 150 370 240 16000670 - - -
12 84 150 340 1740 12000270 - - -12 84 150 340 1740 12000 270 - - -
13 67 150 350 180 12000890 - - -13 67 150 350 180 12000 890 - - -
nicht bestimmt not determined

Claims

Patentansprüche claims
I . Verfahren zur Reinigung von Melamin, dadurch gekennzeichnet, daß verun¬ reinigtes Melamin für 5 Minuten bis zu 20 Stunden bei einem Ammoniakpar¬ tialdruck von 150 bis 400 bar in einem Temperaturbereich von 280 bis 430°C verweilen gelassen wird, worauf zuerst rasch auf Raumtemperatur abgekühlt und anschließend entspannt oder gleichzeitig abgekühlt und entspannt wird und reines Melamin in Pulverform erhalten wird.I. Process for the purification of melamine, characterized in that contaminated melamine is left for 5 minutes to 20 hours at an ammonia partial pressure of 150 to 400 bar in a temperature range of 280 to 430 ° C, after which it is first cooled rapidly to room temperature and then relaxed or simultaneously cooled and relaxed and pure melamine is obtained in powder form.
2. Verfahren nach Anspruch 1 , dadurch gekennzeichnet, daß Melamin in einem Temperaturbereich zwischen den Schmelzpunkt von Melamin und 400°C ver¬ weilen gelassen wird.2. The method according to claim 1, characterized in that melamine is left in a temperature range between the melting point of melamine and 400 ° C.
3. Verfahren nach Anspruch 1 , dadurch gekennzeichnet, daß der Ammoniakpar¬ tialdruck von bis zu 360 bar eingestellt wird.3. The method according to claim 1, characterized in that the ammonia partial pressure of up to 360 bar is set.
4. Verfahren nach Anspruch 1 , dadurch gekennzeichnet, daß die Verweilzeit 10 Minuten bis zu 10 Stunden beträgt.4. The method according to claim 1, characterized in that the residence time is 10 minutes to 10 hours.
5. Verfahren nach Anspruch 1 , dadurch gekennzeichnet, daß das Verfahren an einen Prozeß zur Herstellung von Melamin angeschlossen wird.5. The method according to claim 1, characterized in that the method is connected to a process for the production of melamine.
6. Verfahren nach Anspruch 1 , dadurch gekennzeichnet, daß das Verfahren an einen Hochdruckprozeß zur Herstellung von Melamin aus Harnstoff ange¬ schlossen wird.6. The method according to claim 1, characterized in that the method is connected to a high-pressure process for the production of melamine from urea.
7. Verfahren nach Anspruch 1 , dadurch gekennzeichnet, daß das Verfahren im Anschluß an die Aufarbeitung eines Hochdruckverfahrens angeschlossen wird, wobei die Aufarbeitung die Schritte a) Abtrennen des bei der Umsetzung von Harnstoff erhaltenen NH3/Cθ2-Gas- gemisches vom flüssigen Melamin und/oder b) Reduktion des im Melamin gelösten CO2 durch Einbringen von NH3 umfaßt. 7. The method according to claim 1, characterized in that the method is connected subsequent to the working up of a high pressure process, the working up the steps a) separating the NH3 / CO 2 gas mixture obtained from the reaction of urea from the liquid melamine and / or b) reduction of the CO2 dissolved in the melamine by introducing NH3.
EP96900304A 1995-02-03 1996-01-08 Process for purifying melamine Withdrawn EP0807107A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
AT1869/55 1995-02-03
AT0018695A AT402296B (en) 1995-02-03 1995-02-03 METHOD FOR PURIFYING MELAMINE
PCT/EP1996/000045 WO1996023778A1 (en) 1995-02-03 1996-01-08 Process for purifying melamine

Publications (1)

Publication Number Publication Date
EP0807107A1 true EP0807107A1 (en) 1997-11-19

Family

ID=3483772

Family Applications (1)

Application Number Title Priority Date Filing Date
EP96900304A Withdrawn EP0807107A1 (en) 1995-02-03 1996-01-08 Process for purifying melamine

Country Status (12)

Country Link
EP (1) EP0807107A1 (en)
JP (1) JPH11506415A (en)
KR (1) KR19980701828A (en)
CN (1) CN1172480A (en)
AT (1) AT402296B (en)
BR (1) BR9607332A (en)
HR (1) HRP960044A2 (en)
IL (1) IL117016A0 (en)
NZ (1) NZ298425A (en)
PL (1) PL321596A1 (en)
TW (1) TW305838B (en)
WO (1) WO1996023778A1 (en)

Families Citing this family (20)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AT403579B (en) * 1995-12-07 1998-03-25 Agrolinz Melamin Gmbh METHOD FOR PRODUCING HIGH PURITY MELAMINE
NL1003105C2 (en) * 1996-05-14 1997-11-18 Dsm Nv Process for the preparation of melamine.
NL1003328C2 (en) * 1996-06-13 1997-12-17 Dsm Nv Process for preparing melamine.
NL1003709C2 (en) * 1996-07-30 1998-02-05 Dsm Nv Process for preparing melamine.
ES2197470T3 (en) 1997-05-21 2004-01-01 Dsm Ip Assets B.V. METHOD TO PREPARE MELAMINE.
NL1006095C2 (en) * 1997-05-21 1998-11-25 Dsm Nv Preparation of melamine from urea via a high pressure process
ID23012A (en) 1997-05-28 1999-12-30 Dsm Nv METHOD FOR MAKING MELAMINA
NL1006147C2 (en) * 1997-05-28 1998-12-01 Dsm Nv Pure melamine is formed from urea by spray cooling the melamine melt
KR20010013245A (en) * 1997-06-02 2001-02-26 윌리암 로엘프 드 보에르 Method for preparing melamine
DE69837432T2 (en) 1997-06-02 2007-12-13 Dsm Ip Assets B.V. CRYSTALLINE MELAMINE
NL1006192C2 (en) * 1997-06-02 1998-12-03 Dsm Nv Melamine is prepared from urea in a high pressure process
NL1008571C2 (en) * 1998-03-12 1999-07-28 Dsm Nv Crystalline melamine.
CN1160342C (en) * 1998-11-13 2004-08-04 阿格罗林茨蜜胺有限公司 Method for producing pure molamine
MXPA01006291A (en) * 1998-12-23 2002-04-17 Agrolinz Melamin Gmbh Method for purifying melamine.
NL1013217C2 (en) * 1999-10-05 2001-04-06 Dsm Nv Process for the preparation of melamine.
NL1013456C2 (en) * 1999-11-02 2001-05-03 Dsm Nv Crystalline melamine and its application in amino-formaldehyde resins.
IT1315255B1 (en) * 1999-11-16 2003-02-03 Eurotecnica Dev And Licensing MELAMINE PURIFICATION PROCESS.
US20030028020A1 (en) * 2001-07-27 2003-02-06 Gupta Ram B. Process for the synthesis of high purity melamine
PL209035B1 (en) 2001-11-16 2011-07-29 Ami Agrolinz Melamine Int Gmbh Method for producing melem-free melamine and quenching agents
DE102004018784A1 (en) 2004-04-14 2005-11-03 Ami-Agrolinz Melamine International Gmbh Process for the preparation of pure melamine

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3116294A (en) * 1963-12-31 Process- for preparing high-purity melamine from urea
GB800722A (en) * 1955-03-12 1958-09-03 Montedison Spa Improvements in the production of melamine from urea
DE1217964B (en) * 1961-07-13 1966-06-02 Allied Chem Process for the production of pure melamine
DE1695564A1 (en) * 1966-07-22 1971-05-06 Nissan Chemical Ind Ltd Process for the production of melamine of high purity
US3637686A (en) * 1969-02-10 1972-01-25 Nissan Chemical Ind Ltd Process for recovering purified melamine
DE2522233A1 (en) * 1975-05-20 1976-12-02 Bollmann L Kg Timber board stacking machine - is fitted with conveyor and supply fork equipped with timing and release controls
IT1270577B (en) * 1993-02-22 1997-05-06 Wladimiro Bizzotto HIGH PRESSURE MELAMINE REACTOR
FI96028C (en) * 1993-07-01 1996-04-25 Kemira Oy Process for making melamine

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9623778A1 *

Also Published As

Publication number Publication date
HRP960044A2 (en) 1997-12-31
IL117016A0 (en) 1996-06-18
PL321596A1 (en) 1997-12-08
WO1996023778A1 (en) 1996-08-08
CN1172480A (en) 1998-02-04
KR19980701828A (en) 1998-06-25
JPH11506415A (en) 1999-06-08
ATA18695A (en) 1996-08-15
BR9607332A (en) 1997-11-25
AT402296B (en) 1997-03-25
NZ298425A (en) 1999-04-29
TW305838B (en) 1997-05-21

Similar Documents

Publication Publication Date Title
EP0799212B1 (en) Process for producing high-purity melamine
AT402296B (en) METHOD FOR PURIFYING MELAMINE
AT403579B (en) METHOD FOR PRODUCING HIGH PURITY MELAMINE
EP0799213B1 (en) Melamine purifying process
EP0625142B1 (en) Process for producing pyrrolidone and n-alkyl pyrrolidones
EP1129080B1 (en) Method for producing pure melamine
EP1566382B1 (en) Process for the gentle cooling and crystallisation of melamin from a melamin melt or from the liquid phase
DE2022243C3 (en)
EP1140870B1 (en) Method for purifying melamine
EP1453814B1 (en) Method for purifying a melamine melt
DE2758769C2 (en) Process for the production of morpholine
EP1051409A1 (en) Method for cooling melamine
EP0158928A1 (en) Process for preparing pure 2,6-dichlorobenzonitrile
DE1770827B2 (en) Process for the production of cyanuric acid
DE2708388A1 (en) 4,4'-Dihydroxydiphenylsulphone prepn. of high purity - from phenol and sulphuric acid in presence of solvents
DE69915286T2 (en) METHOD FOR PRODUCING MELAMINE
DE3016336A1 (en) METHOD FOR PURIFYING ROHCAPROLACTAM
AT403475B (en) METHOD FOR PRODUCING CYANURIC ACID
DE2409920C3 (en) Process for the production of cyclopentadienes by thermal cleavage of dicyclopentadienes in the gas phase
EP1165525B1 (en) Method for producing solid melamine
EP1198460B1 (en) Method for producing solid melamine
AT256864B (en) Process for the production of urea
DE19503925A1 (en) Melamine cyanurate prodn.
DE1944754A1 (en) Purification of alpha-hydroxy-isobutyron- - itrile
DE1770667A1 (en) Chemical compound and process for its preparation

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

17P Request for examination filed

Effective date: 19970729

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): AT BE CH DE DK ES FR GB GR IE IT LI LU MC NL PT SE

RIN1 Information on inventor provided before grant (corrected)

Inventor name: COUFAL, GERHARD

Inventor name: CANZI, LORENZO

Inventor name: FINGRHUT, HELMUT

Inventor name: MUELLNER, MARTIN

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN

18D Application deemed to be withdrawn

Effective date: 20010801