A transalkylation process for reacting carbon number nine aromatics with toluene to form carbon number eight aromatics such as para-xylene is herein disclosed. The process is based on the discovery that deactivating contaminants present in typical hydrocarbon feeds, such as chlorides, can be removed with an alumina guard bed prior to contacting with a transalkylation catalyst. Effective transalkylation catalysts have a solid-acid component such as mordenite, and a metal component such as rhenium. The invention is embodied in a process, a catalyst system, and an apparatus. The invention provides for longer catalyst cycle life when processing aromatics under commercial transalkylation conditions.