Method for producing TETA by means of EDDN

#This application is a national stage application (under 35 U.S.C. §371) of PCT/EP2008/052413, filed Feb. 28, 2008, which claims benefit of European application 07103295.7, filed Mar. 1, 2007.

#The invention relates to a process for preparing triethylenetetramine (TETA) by hydrogenation of ethylenediaminediacetonitrile (EDDN) over a catalyst, wherein EDDN is prepared by reaction of ethylenediamine (EDA) with formaldehyde and hydrocyanic acid (HCN). If appropriate, EDDN can also be present as constituent of an amino nitrile mixture which additionally comprises ethylenediaminemonoacetonitrile (EDMN). Diethylenetriaminemonoacetonitrile (DETMN) or diethylenetriaminediacetonitrile (DETDN) can additionally be comprised in the amino nitrile mixture as a result of recirculation of diethylenetriamine (DETA) obtained, if appropriate, in the hydrogenation. Hydrogenation of these further amino nitriles additionally gives tetraethylenepentamine (TEPA).

#It is generally known that aliphatic nitriles, which may optionally be additionally substituted by further functional groups, can be hydrogenated in the presence of catalysts to form the corresponding amines. As indicated below, such hydrogenation processes are also known for various amino nitriles for the purpose of preparing some amines. However, up to now it has not been disclosed anywhere that TETA can also be prepared from the amino nitrile EDDN or, if appropriate, from an amino nitrile mixture comprising EDDN and EDMN by direct hydrogenation of the amino nitrile. However, the previously known processes for preparing TETA are, as indicated below, associated with disadvantages.

#General Method for the Synthesis of Formaldehyde Cyanohydrin (FACH)

#Variant a)

#6000 g (60 mol) of formaldehyde (30%) are placed in a 6 l reaction vessel provided with a propeller stirrer and a pH of 5.5 is set by means of sodium hydroxide solution (1 mol/l). 1661 g (61.2 mol) of hydrocyanic acid are metered in gaseous form via a heated U-tube which is located below the stirrer over a period of 2.5 hours, with the reaction temperature being maintained at 30° C. and the pH being maintained at 5.5. After a further stirring time of 30 minutes, the pH is set to 2.5 by means of sulfuric acid (50% strength). The respective content is determined by means of Liebig titration.