A heterogeneous gas/solid catalytic process for the simultaneous isomerization and dechlorination of nonenes has been identified. Several catalyst systems, including a variety of solid acids, are effective for these reactions. The catalytic isomerization reaction increases the relative level of isomers with higher reactivity towards aromatic alkylation. The dechlorination reaction involves elimination of HCl. The process has been applied to the reactivation and recycle of recovered nonenes from the AlCl3-catalyzed alkylation of diphenylamine. The relative reactivites of the various proposed isomers towards alkylation of diphenylamine catalyzed by AlCl3, and a mechanism for their redistribution in the recovered alkylate after catalytic re-isomerization are proposed.