Christine Mendoza-Frohn

Process for preparing diphenylamines and catalysts usable for this purpose

The preparation of optionally substituted diphenylamine by reaction of optionally substituted aniline with optionally substituted cyclohexanone using a supported Rh catalyst containing rhodium or a combination of rhodium with another platinum metal from the group of palladium, platinum, ruthenium or iridium and which can additionally contain chromium, manganese, alkali metal and a sulphur compound is described. The catalyst of the invention is prepared from halide-free starting materials. The Rh catalyst is distinguished by a low dependence of the initial selectivity, the selectivity in the run-in state and the running-in time on the conditions of the reductive pretreatment and requires only short running-in times to the optimum state.