ABSTRACT
Abstract A process for the production of 3-dimethylaminopropylamine (DMAPA) in high (>99%) purity from N,N-dimethylaminopropionitrile (DMAPN) utilizing a low pressure slurry hydrogenation process is described. The basic process comprises contacting the nitrile with hydrogen at low pressure in the presence of a sponge nickel catalyst under conditions sufficient to effect the conversion of the nitrile to the primary amine product. The improvement in the process resides in a combination of carrying out the hydrogenation process at very low pressure in the presence of an optimum amount of caustic and sponge nickel catalyst in order to give an improved selectivity of greater than 99.9 % of DMAPN to DMAPA. This process can be readily adapted to the established Solutia low pressure hydrogenation process, which employs a continuous gas lift slurry reactor. In this process, a decanter is used to perform the bulk catalyst separation, and entrained catalyst and fines in the decanter effluent are removed by hydroclones. Complete removal of catalyst from the crude amine can be obtained with this system with minimal maintenance and high reliability. This system has a variety of advantages over other competing technologies including high selectivity, low catalyst usage, low capital cost, high reliability, established sources of catalyst, and no need to completely recharge catalyst to reactor. Solutia has been practicing this technology for over 30 years for the production of hexamethylenediamine, and considers it the best technology available to convert nitriles to primary amines. Introduction
The most common and least expensive catalyst for producing primary amines from nitriles is sponge nickel. The generalized reaction, carried out in the presence of sponge nickel catalyst, is the following:
R-C≡N + 2H2 → R-CH2-NH2
Solutia has been producing hexamethylenediamine via low pressure slurry hydrogenation of adiponitrile since 1973. This process can also been adapted for the production of other amines such as DMAPA. The catalyst employed for
this process is a promoted sponge nickel catalyst, and the reaction is carried out in a continuous gas lift reactor as shown in Figure 1.
