.2,6 - Dimethylpiperazine Preparation And Separation Processes

2,6-dimethylpiperazine is an important free chemicals and pharmaceutical intermediate.It can be used in the synthesis of pharmaceuticals,pesticides,dyestuffs, surfactants and etc.In the past,propene oxide,a-hydroxypropanitrile was used to produce 2,6-dimethylpiperazine with hydrogen and ammonia under high pressue condition.These methods have many shortcomings such as complex operation,pollution of the environment. This paper studied the synthesis of 2,6-dimethylpiperazine from diisopropanolamine by bimolecular cycloamination reaction with ammunion in the presence of hydrogenation catalysts,mainly Raney-Ni.The reaction conditions such as the amount of the catalyst,reaction temperature,reaction pressure and reaction time were researched to obtain the optimum conditions:the mass ratio between ammiona and raw material is 26.7:100 to 30:100;reaction temperature 170℃～190℃;the mass ratio between catalyst and raw material is 30:100;a reaction time of 6 to 8 hours;2.0～3.0 MPa initial hydrogen pressure. Under these conditions the yield of 2,6-dimethylpiperazine was about 85%.The separation of pure trans-2,6-dimethylpiperazine and cis-2,6-dimethylpiperazine with vacuum distillation was also invitigated in this work.trans-2,6-dimethylpiperazine and cis-2,6-dimethylpiperazine were then obtained in a purity of 99.2%and 95.7%respectively at the column length is 60 cm and column drive is 2.5 cm with steal ball packing.