Study On The Synthesis Of N-Methylpiperazine From Diethanolamine And Methylamine

N-methylpiperazine is an important medical and chemical intermediate with broad application. The process route of synthesis of N-methylpiperazine from diethanolamine and methylamine is simple and has a wide prospect of industrialization application, and the raw material was cheap and readily available.In this thesis, conventional catalysts of catalytic amination of alcohols were compared and found that the activity of Cu-Al based catalyst was higher. A series of Cu-Al based catalysts were prepared by co-precipitation method and the activity evaluation was carried out in autoclave.The result showed that CuO-NiO/Al₂O₃ has the highest activity. The relations between catalytic activity and properties of catalysts were discussed. The influence of Cu/Al/Ni,variety of precipitator,precipitation patterns , preparation temperature and calcination temperature were investigated. Meanwhile, the catalysts were characterized by TPR,XRD,TG / DTA,BET and SEM. The obtained suitable preparation conditions were as follow: Cu/Al/Ni was 1:1:3.2, precipitator was NaOH, co-current precipitation, preparation temperature is 50℃and the calcination temperature lies around 500℃.Under these conditions the conversion of diethanolamine and the selectivity of N-methylpiperazine were 89.8% and 27.7% respectively. After pre-reduced by H₂ at high temperature, the catalyst showed higher catalytic activity: the conversion of diethanolamine and the yield of N-methylpiperazine were 99.7% and 28.2% respectively.The process conditions were also optimized and the better catalytic activity has been obtained under the reaction conditions : NH(CH₂CH₂OH)₂/CH₃NH₂=1/2, reaction temperature 225℃and reaction time 8h, Meanwhile, comparisons between the characterization results of unused and used catalysts showed that the deactivation reason of the catalysts was that some oligomeric compounds deposited on the catalyst surface and blocked active site.