The invention provides a synthetic preparation method of 3, 3 '-diaminodipropylamine (DPTA), which is efficient, safe, low in cost and easy to industrially amplify. The method is realized through two-step reaction: firstly, preparing 18-22%
ammonia water in a water phase
system under the conditions that the temperature is controlled to be 40-50 DEG C and the pressure is less than or equal to 0.3 MPa, then dropwise adding
acrylonitrile into the
ammonia water for reaction under the conditions that the temperature is 60-65 DEG C and the pressure is less than or equal to 0.5 MPa to generate a high-purity DPTAm intermediate, and carrying out rectification
dehydration to obtain a dehydrated synthetic liquid containing more than or equal to 95 wt% of DPTAm; then in a
hydrogenation reaction, isopropanol is used as a
solvent,
Raney nickel is used as a catalyst, KOH or NaOH is used as an auxiliary agent, under the guarantee of
nitrogen and
hydrogen replacement, the DPTAm dehydrated substance is dropwise added at a
constant speed for
catalytic hydrogenation under the conditions of 80-85 DEG C and 2.2-2.6 MPa, and after the reaction is completed,
desolvation, light component removal and rectification purification are performed to obtain the target product DPTA. According to the method, high-selectivity synthesis of DPTAm is achieved, generation of by-products is remarkably reduced,
ammonia gas consumption and
recovery cost are reduced, meanwhile, the
hydrogenation process is optimized, the conversion rate and yield are improved, the DPTA content is larger than or equal to 96%, and the total yield is larger than or equal to 95%. The
Raney nickel catalyst can be repeatedly used for more than 50 batches, has stable activity, greatly reduces the production cost, and is suitable for large-scale industrial application.