WO2005068440A1 - Amelioration du rendement en melamine des procedes de production de melamine par catalyse - Google Patents

Amelioration du rendement en melamine des procedes de production de melamine par catalyse Download PDF

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Publication number
WO2005068440A1
WO2005068440A1 PCT/EP2004/053498 EP2004053498W WO2005068440A1 WO 2005068440 A1 WO2005068440 A1 WO 2005068440A1 EP 2004053498 W EP2004053498 W EP 2004053498W WO 2005068440 A1 WO2005068440 A1 WO 2005068440A1
Authority
WO
WIPO (PCT)
Prior art keywords
reactor
melamine
filter
fluidized
catalyst
Prior art date
Application number
PCT/EP2004/053498
Other languages
English (en)
Inventor
Willi Ripperger
Original Assignee
Casale Chemicals S.A.
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
Priority claimed from EP04000931A external-priority patent/EP1566382B1/fr
Priority claimed from DE200410014770 external-priority patent/DE102004014770A1/de
Application filed by Casale Chemicals S.A. filed Critical Casale Chemicals S.A.
Priority to JP2006548194A priority Critical patent/JP2007517818A/ja
Priority to CN2004800230347A priority patent/CN1835932B/zh
Publication of WO2005068440A1 publication Critical patent/WO2005068440A1/fr

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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

  • the starting material for the production of melamine is mainly urea which decomposes first at temperatures > 350°C in accordance with reaction (1) into ammonia and isocyanic acid.
  • the formed isocyanic acid reacts further after equation (2) to melamine:
  • FIG 1 shows the principle of a catalytic low pressure process: Liquid urea (11) is converted to melamine in a fluidized-bed reactor (12) at 390 to 400°C.
  • fluidizing gas (14) either pure ammonia or the NH 3 /CO 2 -mixture formed during the reaction is used.
  • the process gas contains entrained catalyst fines which are not separated in the reactor cyclones.
  • the gas can be quenched with water as practiced in the DSM-process, line (15) in figure 1.
  • An aqueous suspension of melamine, higher molecular by-products , oxotriazines and catalyst dust is formed. From this suspension the melamine is obtained by re- solution, filtration of the insoluble compounds and recristallisation. Details to this process see Ullmann's Encyclopedia of Industrial Chemistry, Vol. A 16, page 176, (1990).
  • the melamine is desublimated by a gas-quench (18) and separated from the gas in the cyclone (19).
  • the nearly melamine-free gas from the cyclone (19) is cooled down by washing with li- quid urea in the washer (20) and recycled as cooling gas to the gas-quench (18) and as fluidizing gas to the reactor (12).
  • the surplus of the gas is treated in a separate off-gas unit
  • the present invention is directed to the low and medium pressure catalytic processes for producing melamine from urea wherein the melamine is pro- prised in a fluidized bed reactor and recovered from the process gas either by a water quench or by a gas quench.
  • Primary object of the present invention is to avoid the economical disadvantages of the above mentioned catalytic processes, especially of the DSM- and BASF- processes, by increasing the urea conversion, re-converting higher mo- lecular by-products to melamine and removing at the same time catalyst fines from the process gas.
  • the aforesaid and other objectives for this invention are surprisingly accomplished by the installation of a filter-reactor, which increases the conversion of the isocyanic acid according to equation (2), re-converts higher molecular by - products to melamine and which removes simultaneously the catalyst fines in the process gas.
  • the filter-reactor consists of one or more ring -reactors.
  • the individual ring-reactor consists of two concentric cylinders with perforated walls. The annular space between the two cylinders contains the catalyst.
  • Figure 2a shows schematically the structural principle of a ring-reactor as used as an element in a filter-reactor
  • figure 2b shows a top view of a filter- reactor (7) with four ring-reactors (2) inside.
  • the hot process gas from the fluidized bed reactor is directly fed at (1) to the filter-reactor (7) which may consist of one or more ring-reactors (2).
  • the process gas flows radial through the outer perforated wall (3) of the ring- reactors penetrates the catalyst bed (4) and leaves the ring-reactor through its inner wall which is perforated as well. From the central pipe or gas sampler (5) of the filter-reactor the gas flows to the melamine separation unit.
  • the individual ring-reactors are gastight fixed at the upper part (6) of the filter reactor and can be exchanged easily if necessary. To keep the reaction temperature in the filter reactor at the required level it is sufficient to insulate the outer walls of the filter-reactor because the conversion of the isocyanic acid to melamine according to equation (2) is an exothermic reaction.
  • filter-reactor (7) which is double-walled so that it can be heated by hot gases, for example.
  • Number and dimension of the individual ring-reactors within the filter-reactor are depending on the capacity and the conversion rate of the fluidized bed reactor and on the activity of the catalyst in the ring-reactor.
  • a length between 1000 and 4000 mm is recommended, although in special cases other dimensions may be optimal.
  • the outer diameter of the ring-reactor is chosen between 200 and 900 mm, the diameter of the inner cylinder should be in the range 150 to 300 mm. But here too other dimension can be used, for example, for process-technical reasons or physical conditions.
  • catalyst dust in the process gas is deposited only on the outer surface of the catalyst bed and can be easily removed by periodical back-flushing of the individual ring- reactors via valve (8) with hot ammonia, fluidizing gas or steam. Steam regeneration also removes organic deposits on the catalyst.
  • the catalyst dust can be discharged at the bottom of the filter-reactor.
  • the isocyanic acid still contained in the process gas, reacts to melamine according to equation (2). Melem and other higher condensed nitrogen com- pounds react on the catalyst with ammonia back to melamine, for example:
  • Suited catalyst for the filter-reactor are all catalysts used or known for the production of melamine, consisting of pure y - Al 2 0 3 , alumina - silicates with 10 to 90% SiO 2 , or pure SiO 2 .
  • catalysts which contains in a matrix of alumina silicate 20 to 80% molecular sieves with a mean pore size diameter above 6 Angstrom are all catalysts used or known for the production of melamine, consisting of pure y - Al 2 0 3 , alumina - silicates with 10 to 90% SiO 2 , or pure SiO 2 .
  • catalysts which contains in a matrix of alumina silicate 20 to 80% molecular sieves with a mean pore size diameter above 6 Angstrom are examples of alumina silicate 20 to 80% molecular sieves with a mean pore size diameter above 6 Angstrom.
  • the catalysts in the filter-reactor can have the same chemical composition as the catalyst in the main reactor. But it is also possible to use quite different catalysts with respect to chemical composition, acidity or surface area in the filter-reactor, because in the filter-reactor only the reaction of isocyanic acid to melamine and the re-conversion of the higher molecular nitrogen compounds to melamine must be catalysed.
  • the fluidized-bed main reactor contains a catalyst of pure alumina, it can be advantageous to use silica-alumina catalyst in the filter- reactor.
  • the filter-reactor can be operated at the same pressure as the fluidizing- bed main reactor or it can be run at a lower pressure.
  • Example 1 With the following examples and figure 3 a preferred embodiment of the process is described in more detail.
  • Example 1
  • urea is decomposed at 400°C and 3 bar.
  • the catalyst consists of pure Y - alumina.
  • As fluidizing gas the reaction gas obtained at the formation of melamine from urea is used, a mixture of about 70 vol.% ammonia and 30 vol.% carbon dioxide.
  • the gas coming from the fluidized-bed reactor is directly fed to the filter-reactor (2).
  • the filter- reactor contains four ring-reactors (3), (for example only) with an outer diameter of 600 mm each and a length of 4000 mm.
  • Temperature and pressure in the filter-reactor is the same as in the fluidized- bed reactor.
  • a cyclone (5) may be installed between the fluidized-bed reactor and the filter-reactor.
  • Table 1 shows the gas composition before and after entering the filter-reactor (without inert components).
  • the process gas After leaving the filter - reactor the process gas can be cooled down to generate high-pressure steam in the cooler (4).
  • the extent of the cooling is limited by the partial pressure of the melamine in the gas after the filter reactor.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Abstract

L'invention concerne un procédé permettant d'accroître le rendement en mélamine, et d'améliorer la séparation des poussières dans la production de mélamine à partir d'urée au moyen de processus catalytiques en lit fluidisé. Ce procédé consiste à transférer le gaz de traitement du réacteur à lit fluidisé qui contient, outre la mélamine, de l'acide isocyanique non converti, du melam, du melem ou d'autres composés à masse moléculaire élevée, dans un réacteur filtrant formé d'un ou de plusieurs réacteurs annulaires remplis de catalyseurs, dans lesquels l'acide isocyanique qui n'a pas encore été converti est converti en mélamine, et les composés à masse moléculaire élevée, en particulier le melam et le melem, sont également reconvertis en mélamine par réaction avec l'ammoniac contenu dans le gaz de traitement, et les fines de catalyseur encore présentes dans le gaz de traitement du réacteur à lit fluidisé sont éliminées.
PCT/EP2004/053498 2004-01-17 2004-12-15 Amelioration du rendement en melamine des procedes de production de melamine par catalyse WO2005068440A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
JP2006548194A JP2007517818A (ja) 2004-01-17 2004-12-15 メラミン収率を改善する触媒メラミン製造方法
CN2004800230347A CN1835932B (zh) 2004-01-17 2004-12-15 改进催化三聚氰胺生产工艺中的三聚氰胺产率

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
EP04000931.8 2004-01-17
EP04000931A EP1566382B1 (fr) 2004-01-17 2004-01-17 Procédé de refroidissement et crystallisation de mélamine a partir d'une fusion de mélamine ou de la phase gaseuse
DE102004014770.1 2004-03-26
DE200410014770 DE102004014770A1 (de) 2004-03-26 2004-03-26 Verbesserung der Melaminausbeute bei katalytischen Herstellungsverfahren durch Einsatz eines Filterreaktors

Publications (1)

Publication Number Publication Date
WO2005068440A1 true WO2005068440A1 (fr) 2005-07-28

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PCT/EP2004/053498 WO2005068440A1 (fr) 2004-01-17 2004-12-15 Amelioration du rendement en melamine des procedes de production de melamine par catalyse

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JP (1) JP2007517818A (fr)
WO (1) WO2005068440A1 (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN100388972C (zh) * 2006-05-16 2008-05-21 梁振玉 三聚氰胺生产用氧化铝催化剂的生产方法
EP2703390A1 (fr) * 2011-04-28 2014-03-05 Beijing Edgein Technology Co., Ltd. Système et procédé économes en énergie et peu coûteux pour produire de la mélamine par trempe gazeuse
WO2022184536A1 (fr) 2021-03-04 2022-09-09 Basf Se Procédé de préparation d'un produit de condensation de mélamine

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1995025098A1 (fr) * 1994-03-15 1995-09-21 Dsm N.V. Procede de separation des impuretes d'un melange de gaz de synthese a chaud lors de la preparation de melamine
WO1996020182A1 (fr) * 1994-12-23 1996-07-04 Agrolinz Melamin Gmbh Procede de production de melamine tres pure
WO2001007421A2 (fr) * 1999-07-27 2001-02-01 Agrolinz Melamin Gmbh Procede de preparation de melamine
WO2002022589A1 (fr) * 2000-09-13 2002-03-21 Casale Chemicals S.A. Procede de production de melamine a haute purete a partir d'uree

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1995025098A1 (fr) * 1994-03-15 1995-09-21 Dsm N.V. Procede de separation des impuretes d'un melange de gaz de synthese a chaud lors de la preparation de melamine
WO1996020182A1 (fr) * 1994-12-23 1996-07-04 Agrolinz Melamin Gmbh Procede de production de melamine tres pure
WO2001007421A2 (fr) * 1999-07-27 2001-02-01 Agrolinz Melamin Gmbh Procede de preparation de melamine
WO2002022589A1 (fr) * 2000-09-13 2002-03-21 Casale Chemicals S.A. Procede de production de melamine a haute purete a partir d'uree

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN100388972C (zh) * 2006-05-16 2008-05-21 梁振玉 三聚氰胺生产用氧化铝催化剂的生产方法
EP2703390A1 (fr) * 2011-04-28 2014-03-05 Beijing Edgein Technology Co., Ltd. Système et procédé économes en énergie et peu coûteux pour produire de la mélamine par trempe gazeuse
EP2703390A4 (fr) * 2011-04-28 2014-12-10 Beijing Edgein Technology Co Ltd Système et procédé économes en énergie et peu coûteux pour produire de la mélamine par trempe gazeuse
WO2022184536A1 (fr) 2021-03-04 2022-09-09 Basf Se Procédé de préparation d'un produit de condensation de mélamine

Also Published As

Publication number Publication date
JP2007517818A (ja) 2007-07-05

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