Increasing the life of a supported ruthenium catalyst in the hydrogenation of an olefinically unsaturated dinitrile

In a single-stage process for the reduction of olefinically unsaturated dinitriles to saturated diamines by contacting a supported ruthenium catalyst, olefinically unsaturated dinitrile, hydrogen, diluent, and ammonia as secondary amine suppressant, under effective hydrogenation conversion run conditions of contacting temperature in the range of about 100.degree. C. to 170.degree. C., and contacting pressure in the range of about 1500 to 2500 psia, the improvement which comprises increasing the run life of said supported ruthenium catalyst by initially contacting said supported ruthenium catalyst, olefinically unsaturated dinitrile, hydrogen, diluent, and ammonia at a low contacting pressures in the range of about 900 to 1300 psig for a start-up interval of 1 to about 160 hours at a start-up temperature in the range of about 100.degree. C. to 120.degree. C., and thereafter gradually increasing the operating pressure over an interval of about 24 to 48 hours to said run operating pressure, thereby increasing the run life of said supported ruthenium catalyst for said single-step reduction process.