It is known from EP-A-0133938 that alumino-zeolite catalysts used in the hydroamination reaction deactivate quickly since these catalysts promote polymerization or oligomerization of the olefins used on the catalyst and subsequent carbonization of these polymeric or oligomeric residues on the catalysts. EP-A-0133938 teaches that deactivation of the catalysts can be reduced when ammonia, primary or secondary amines are reacted with olefins in the presence of borosilicate or borogermanate zeolite catalysts of the pentasil type, the amine obtained is separated off and the unreacted starting materials are recirculated. Furthermore, it is disclosed that deactivated catalysts can be regenerated by passing air or an air/nitrogen mixture over the catalyst at from 400 to 550° C.
WO-A-97/07088 discloses the hydroamination of olefins in the presence of boron-BETA-zeolite catalysts. This application mentions various factors which can influence the deactivation of catalysts. Thus, it is taught that monoolefins have a less pronounced tendency to polymerize than do diolefins or polyolefins. Higher temperatures are said to promote the polymerization and the cracking reaction of the olefins used. The activity of the catalysts can, according to the disclosure, be restored by regeneration in an oxygen-comprising gas at elevated temperatures.
The prior art teaches that the polymerization of the olefins used in the hydroamination reaction and the carbonization resulting therefrom can lead to deactivation of the catalysts used. Factors such as the type and nature of the catalyst, the reaction temperature, the type of olefin can influence the rate and the degree of deactivation. The activity is usually restored by regeneration of the catalysts by passing an oxygen-comprising gas over the catalyst at a temperature in the range from 400 to 550° C.
DE-A-10313853 teaches that the activity of calcined, zeolytic catalysts can be increased when the calcined catalyst is treated at temperatures in the range from 100 to 550° C. in an oxygen-comprising gas stream a maximum of 24 hours before commencement of the reaction. According to the disclosure, an increase in the activity occurs regardless of whether the catalyst is used for the first time in the hydroamination or whether a previously regenerated catalyst is used.
DE-A-102005051044 discloses that the hydroamination is generally carried out in an adiabatically operated reaction unit.
When starting up zeolytic catalysts, i.e. when the catalyst is first brought into contact with the feed mixture of olefin and ammonia or amine, a temperature increase is generally observed since the heat produced during start-up can be removed only with great difficulty in the case of industrial, adiabatically operated reactors. This temperature increase generally promotes the oligomerization of the olefins used. Since the oligomerization is generally an exothermic reaction, the heat liberated in this reaction additionally accelerates the temperature rise. The high temperatures occurring in the start-up process generally lead to damage to the catalyst caused by deposition of the olefin oligomers on the catalyst surface and in the pores or even to a change in the zeolite structure itself.