Synthesis of 1,4-diaminocyclohexane in supercritical ammonia

The amination of 1,4-cyclohexanediol in supercritical ammonia has been studied in a continuous fixed-bed reactor at 135 bar. An unsupported cobalt catalyst stabilized by 5 wt% Fe afforded the main reaction products 4-aminocyclohexanol and 1,4-diaminocyclohexane with a cumulative selectivity of 97% at 76% conversion. Excess of ammonia and short contact time favored the desired reactions. At low and high conversions the amination selectivity decreased due to the formation of dimers and oligomers and degradation products. Recycling of the unreacted diol and amino alcohol intermediate can provide an alternative economic process for the synthesis of 1,4-diaminocyclohexane. (C) 1999 Academic Press.