Process for the preparation of pure triethylenediamine (TEDA)

Details Process for the preparation of pure triethylenediamine (TEDA) Process for the preparation of pure triethylenediamine (TEDA)

2002-01-03

2003-04-22

Berch, Mark L. (Department: 1624)

Organic compounds -- part of the class 532-570 series

Organic compounds

Nitrogen attached directly or indirectly to the purine ring...

Reexamination Certificate

active

06552194

ABSTRACT:

The present invention relates to a process for the preparation of pure triethylenediamine (=TEDA=DABCO®=1,4-diazabicyclo[2.2.2]octane) and solutions thereof.
Triethylendiamine (TEDA), which is a solid under normal conditions, is an important catalyst for the production of polyurethane foams.
For this and other areas of application, a pure TEDA with the lowest possible odor and a pure-white color with the least possible discoloration, for example with the lowest possible APHA color number (DINISO 6271) which retains these properties even over extended storage times (of, for example, 6, 12 or more months) is desired.
Various processes are known for the preparation and purification of TEDA:
DT-A-24 42 929 relates to a process for the preparation of TEDA by elimination of glycol from N,N′-di(hydroxyethyl)piperazine in the presence of Al
2
O
3
as catalyst.
U.S. Pat. No. 3,297,701 discloses a process for the preparation of diazabicyclo[2.2.2]octanes by reaction of corresponding hydroxyethyl- or aminoethylpiperazines at elevated temperature in the presence of metal phosphates, for example calcium phosphate.
DE-A-36 34 258 describes a process for the preparation of diazabicyclo[2.2.2]octanes by reaction of corresponding hydroxyethyl- or aminoethylpiperazines in the presence of zirconium phosphates.
DE-A-1 745 627 relates to a process for the preparation of TEDA and piperazine by reaction of an ethylenediamine on an acidic silica/alumina catalyst at elevated temperature and isolation of the TEDA by distillation and/or crystallization.
DE-A-37 18 395 describes the preparation of TEDA by reaction of an acyclic hydroxyethylethylenepolyamine and/or cyclic hydroxyethylethylenepolyamine in the presence of a phosphorus-containing titanium dioxide or zirconium dioxide catalyst.
EP-A-111 928 describes the use of certain phosphate catalysts, for example mono- or pyrophosphates of magnesium, calcium, barium or aluminum, in organic condensation reactions, for example the conversion of N-(2-hydroxyethyl)piperazine into TEDA.
EP-A-382 055 discloses a process for the preparation of TEDA in which 1,2-diaminoethane and from 0 to 200 mol % of piperazine are reacted at elevated temperature on Al, B, Ga and/or Fe silicate zeolites.
EP-A-842 935 describes a process for the preparation of TEDA by conversion of an amine compound, such as monoethanolamine, into a product comprising TEDA and piperazine on a catalyst, followed by reaction of this product with an ethylating compound containing at least one N and/or O atom in the presence of a shape-selective zeolite catalyst.
U.S. Pat. No. 5,741,906 relates to the preparation of TEDA by reaction of an amine compound, such as monoethanolamine, on a zeolite catalyst of the pentasil type.
The known processes for the preparation of TEDA result in the formation of crude reaction products which, besides TEDA, also contain water, by-products, for example piperazine and high-molecular-weight polymers, and any solvent employed in the reaction. TEDA is usually separated off from these mixtures by batch or continuous distillation or rectification and is usually purified in a subsequent step by crystallization or recrystallization.
Owing to its properties [hygroscopic, heat-sensitive, boiling point (174° C. at atmospheric pressure) and melting point (158-160° C.) close to one another], TEDA can be handled with difficulty and only with corresponding technical effort without an impairment in the quality of the TEDA with respect to color, color stability (undesired increase in the color number, for example measured as the APHA color number, over the storage time), odor (undesired smell of cyclic saturated N-heterocyclic compounds having 5-membered rings or other cyclic saturated N-heterocyclic compounds having 6-membered rings and/or aromatic N-heterocyclic compounds having 5- or 6-membered rings) and purity taking place.
The TEDA obtained by the known processes after distillation or rectification and solutions prepared therefrom is/are usually unmarketable owing to the color (for example measured as APHA color number), color stability and/or odor, and only through one or more further purification step(s), such as technically complex crystallization or recrystallization, in some cases in a number of steps, is it possible to improve the TEDA quality.
There has therefore been no lack of attempts to find alternative processes for the preparation of TEDA in improved quality.
DT-A-26 11 069 relates to the isolation of TEDA in which propylene glycol is added to the crude TEDA, and the mixture is subsequently subjected to fractional distillation.
DE-A-28 49 993 discloses a process for the separation and isolation of TEDA in which water is added to the crude TEDA, and the mixture is subsequently distilled.
JP-A-49 048 609 claims a process for the purification of piperazine and/or TEDA by fractional distillation of a mixture comprising piperazine and/or TEDA, comprising the steps of dissolution of the piperazine and/or TEDA distillates in water or an organic solvent, it being possible for the solvent to be in liquid or gas form, and collection of the solutions of the distillates. According to the application, this process achieves the object of preventing blockages by solids in the distillation apparatus. The description, the diagrammatic representation of the distillation apparatus and the examples in this patent application teach that, to this end, the piperazine or the TEDA is firstly liquefied in a condenser at the top of the distillation column and only thereafter dissolved in the solvent.
This process has the disadvantage that it does not give TEDA in the desired quality.
The earlier German patent applications 19933850.7 of Jul. 23, 1999, and 19962455.0 of Dec. 22, 1999, relate to a process for the preparation of a solution of pure TEDA in which TEDA is evaporated, and the vapor-form TEDA is passed into a liquid solvent, and to a process for the preparation of pure TEDA in which TEDA is crystallized out of this solution.
It is an object of the present invention to find an improved, efficient and economical process for the preparation of pure triethylenediamine (TEDA) and solutions thereof which gives TEDA and TEDA solutions of improved quality with respect to color, color stability, odor and purity.
We have found that this object is achieved by a process for the preparation of a solution of pure triethylenediamine (TEDA) which comprises evaporating TEDA from a mixture comprising a solvent or diluent, where the solvent or diluent has a boiling point at atmospheric pressure (=1.01325 bar) in the range from 175 to 250° C., and passing the vapor-form TEDA into a liquid solvent.
Subsequent crystallization of the TEDA out of the resultant solution gives pure TEDA having the quality improved in accordance with the object.
The solvent in whose presence the TEDA is evaporated and the solvent into which the vapor-form TEDA is passed may be the same or alternatively different solvents.
The process according to the invention, in which the passing of the vapor-form TEDA into a liquid solvent is also referred to below as TEDA quenching, significantly reduces the formation of undesired by-products and decomposition products which result in a reduction in the quality of the TEDA.
The liquid physical state of the TEDA at the outlet of the evaporation apparatus, for example rectification or distillation apparatus, is avoided in accordance with the invention, with the liquefaction of the distillate that is usual in distillations not taking place. The vapor-form TEDA is instead passed directly into a liquid solvent.
The solvent or diluent present in the mixture from which the TEDA is evaporated preferably has a boiling point at atmospheric pressure in the range from 180 to 250° C., particularly in the range from 180 to 230° C., in particular in the range from 190 to 210° C.
Suitable solvents or diluents present in the mixture from which the TEDA is evaporated are, in particular, inert
polar aprotic solvents [for example

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