A process for converting mixtures of C.sub.6 to C.sub.30 n-paraffin and n-paraffin by-products to substantially pure n-paraffin which comprises catalytically hydrogenating the mixture at a temperature of from about 600.degree. to 750.degree.F. in the presence of a Group VIII metal on alumina catalyst, and from about 10 to 5,000 parts per million of nitrogen present as ammonia or an organonitrogen compound. The catalyst can additionally contain a Group VIB or VIIB metal.