If the imine formation is conducted in a flow tube, residence
times of 4- 10 s can be chosen to suppress secondary reactions
such as the polymerization of ethylenimine. The imine selectivity
then increases to 80- 85% (based on ethanolamine). Processes
for ethylenimine manufacture based on this route have been
developed by BASF and Hoechst.
In a process from Dow, ethylenimine is synthesized by reacting
1,2-dichloroethane with NH, in the presence of CaO at about 100 "C: