Process for producing N,N'-disubstituted paraphenylene diamine mixtures by sequential reductive alkylation

In the process for preparing a mixture of two or more different N,N'-disubstituted paraphenylenediamines by the reductive alkylation of a nitrogen-containing compound selected from 4-nitrodiphenylamine, 4-aminodiphenylamine, paranitroaniline and phenylene diamine with two or more ketones selected from ##STR2## wherein x is an integer of from 2 to 9 and R.sub.1 and R.sub.2 are alkyl of 1 to 8 carbon atoms, with the proviso that the total number of carbon atoms in R.sub.1 and R.sub.2 together is nine or less, in the presence of hydrogen and a catalyst, the improvement which comprises charging one ketone and a molar excess of the nitrogen-containing compound to a reaction zione and causing them to react, under hydrogen pressure, until the one ketone is essentially completely consumed, charging a second, different, ketone to the reaction zone in an amount in a molar excess over the amount of unreacted nitrogen-containing compound, causing the second ketone and the remaining nitrogen-containing compound to react, under hydrogen pressure, until the remaining nitrogen-containing compound is essentially completely consumed, separating the mixture of N,N'-disubstituted paraphenylenediamines from the mixture of volatile by-products and unreacted second ketone and recovering the unreacted second ketone by distillation.