The preparation of IPDA by aminating hydrogenation of IPN is known and has already been described many times.
In the simplest case (U.S. Pat. No. 3,352,913), IPN is reacted in the presence of hydrogen and of an excess of ammonia over a cobalt catalyst. First of all, IPN and ammonia eliminate water to form isophoronenitrile imine, IPNI, which is subsequently hydrogenated to IPDA.

When the reaction is conducted in this way, the yield of IPDA is determined to a crucial degree by the excess of ammonia. The maximum IPDA yields achieved are about 80%. The main by-product is what is called the amino alcohol, IPAA, which results from the direct hydrogenation of the IPN.

A significant rise in the IPDA yield is achieved when the formation of IPNI is accelerated by use of suitable imination catalysts. Suitable imination catalysts are, for example, acidic ion exchange resins (EP 042 119). In addition, it is also possible to use acidic metal oxides (EP 449 089), sulpho-containing organopolysiloxanes (EP 816 323), heteropolyacids (DE 44 26 472) and activated carbon (EP 061 137) as imination catalysts. As well as the reduction of the unwanted amino alcohol, other by-products are also distinctly suppressed, for example bicyclic compounds and those by-products which result from the elimination of HCN.
Particular reference is made to the problem of elimination of HCN from gamma-keto nitriles, such as IPN, in the literature (U.S. Pat. No. 3,352,913). Firstly, it is noted that HCN elimination reduces the yield of IPDA (EP 042 119, DE 44 26 472).
Secondly, it is pointed out that HCN acts as a catalyst poison and leads to deactivation of the hydrogenation catalyst (EP 394 967 A1, page 2 line 34 ff, page 3 line 44 ff). It is therefore advisable to conduct the imination step in such a way that a minimum amount of HCN is eliminated.
According to EP 913 387, selectivity can also be enhanced in the preparation of IPDA by using quaternary ammonium bases. Correspondingly modified catalysts, specifically in the case of use of a solvent, have a much longer service life than alkali-modified catalysts.
In addition, processes for preparing isophoronediamine are known from CN 104230721A, EP 2649042A and WO 2012126869A.
The underlying object was to find a process for preparing 3-aminomethyl-3,5,5-trimethylcyclohexylamine by hydrogenation of isophoronenitrile, wherein the yield and selectivity in the reductive amination of isophoronenitrile for preparation of isophoronediamine were to be improved.