Methods of producing composite zeolite catalysts for heavy reformate conversion into xylenes

A method of forming composite zeolite catalyst particles includes combining a silicon source, an aqueous organic structure directing agent having a polyquaternary ammonium compound, water and an aluminum source to form a catalyst gel. The method also includes heating the catalyst gel to form the composite zeolite catalyst particle having an intergrowth region with a mixture of both Mordenite crystals and ZSM-5 crystals. An associated method of making xylene includes feeding heavy reformate to a reactor, the reactor containing the composite zeolite catalyst particles, and producing xylene by simultaneously performing dealkylation and transalkylation of the heavy reformate in the reactor, where each composite zeolite catalyst particle is able to catalyze both the dealkylation and transalkylation reactions.