Study On Continuous Preparation Of N-methyl-1,3-propanediamine

N-methyl-1,3-propylenediamine（MAPA）is a series of derivatives of 1,3-propylenediamine,is widely used in pesticides,medicine and dyes and other fields,such as the preparation of deworming drugs for the treatment of hookworm disease and ascariasis;It can be used to prepare Alfzosin hydrochloride for the treatment of prostate-related diseases.It can be used as a CO₂absorbent,which can be used to absorb and treat the CO₂produced by coal-fired power plants,thus greatly reducing greenhouse gas emissions.However,at present,the preparation of N-methyl-1,3-propylene diamine in China is mostly carried out by high-pressure reactor for intermittent production,which has low production efficiency,poor safety,large quality fluctuation and small scale,and is difficult to meet the growing market demand.Therefore,the study of N-methyl-1,3-propylene diamine continuous process has important practical value and theoretical significance,but also for the future continuous large-scale production to lay the foundation.In this paper,on the basis of summarizing and analyzing the previous literature,the continuous process of N-methyl-1,3-propylene diamine was studied.The main work and results are as follows:（1）The first step is the condensation addition reaction of acrylonitrile and monomethylamine,and the continuous preparation of 3-methylaminopropionitrile by catalytic condensation in a fixed-bed reactor,and the process conditions are screened.The optimized DWT 2 catalyst was optimized at the molar ratio of monomethylamine to acrylonitrile of1.10:1.00,reaction pressure of 3.0-5.0 MPa,reaction temperature of 25℃,and total volume space velocity of:Under the reaction conditions of 0.75-1.50h^-1,the conversion of acrylonitrile was more than 99.90%,and the selectivity of 3-methylaminopropionitrile was more than 99%（2）The second step is the catalytic hydrogenation of 3-methylaminopropionitrile,and the continuous hydrogenation of 3-methylaminopropionitrile in a fixed-bed reactor is used to prepare N-methyl-1,3-propylenediamine.The optimized TW 4 catalyst was prepared at temperature 35-80℃,pressure 1.5-6.0 MPa,space velocity 0.2-2.2h^-1,molar ratio of hydronitrile 6:1,co-catalyst Na OH,co-catalyst dosage:Under the reaction condition of 1.0%,the conversion rate of 3-methylaminopropionitrile is above 99.5%,and the selectivity of N-methyl-1,3-propylene diamine is above 99%.（3）Two sets of continuous process devices were set up according to the process route.Under the optimized process conditions,N-methyl-1,3-propylene diamine was prepared continuously.At the same time,the other two derivatives of 1,3-propylene diamine were respectively prepared:N,N-dimethyl-1,3-propylenediamine and N-（2-hydroxyethyl）-1,3-propylenediamine were prepared continuously.The first set of continuous process equipment is to use two fixed-bed reactors in series to continuously prepare 1,3-propylene diamine derivatives.During continuous 48 hours of preparation,the conversion of acrylonitrile is more than 99.5%,and the selectivity of N-methyl-1,3-propylene diamine and N,N-dimethyl-1,3-propylene diamine is more than 99%.The selectivity of N-（2-hydroxyethyl）-1,3-propylenediamine was 98-99%;The second set of continuous process equipment uses a microchannel reactor and a fixed-bed reactor to continuously prepare 1,3-propylene diamine derivatives.During continuous 48 hours of preparation,the conversion of acrylonitrile is more than 99.5%,and the selectivity of N-methyl-1,3-propylene diamine is96-97%.The selectivity of N,N-dimethyl-1,3-propylenediamine was 97-98%and that of N-（2-hydroxyethyl）-1,3-propylenediamine was 98-99%.