The utilization of exhausted fluid catalytic cracking (FCC) catalysts as raw materials for the zeolite synthesis was analyzed. Samples of the catalysts directly released from FCC units and the corresponding impact grinding pretreated samples were used. Mechanical treatment was observed to decrease catalyst crystallinity and particle size. The catalyst reactivity was analyzed in terms of conversion in zeolite and product properties. Hydrothermal synthesis experiments in NaOH medium were performed. Catalysts conversion in A and X type zeolites was obtained for treated and not treated samples. In particular, high conversion in NaX type were achieved using the more siliceous catalyst, whereas grinding activation produces a decrease of particle size and Al/Si ratio of the zeolites obtained. (c) 2006 Elsevier B.V. All rights reserved.