Zeolites are materials that have large applications as an ionic exchange, adsorbent and catalysis. One of the most important zeolites that it has industrial applications especially as a catalyst is ZSM-5 . In this project , a comparative study of the reaction parameters involving the vapour phase isopropylation of benzene with isopropanol (IPA) over H-ZSM-5 and H 3 PO 4 -ZSM-5 catalysts is taken up to evaluate the performance of these two catalysts for the industrially important cumene synthesis. Evaluation of catalysts for isopropylation of benzene reaction using 2-propanol as alkylating agent was carried out in a continuous, down-flow, fixed-bed reactor at atmospheric pressure in the temperature range 423-673 K. The influence of SiO 2 /Al 2 O 3 ratio (60-170) of the zeolite, H 3 PO 4 content, reaction parameters such as reaction temperature, molar ratio of benzene and 2-propanol, and time on stream was studied. Maximum benzene conversion (12%) was noted at 523 K over 15%-H 3 PO 4 -ZSM-5. The reaction selectivity on 15%- H 3 PO 4 -ZSM-5-60 (SiO 2 /Al 2 O 3 = 60) is higher (100%) than that of the most active H-ZSM-5 catalyst (74%) at the same temperature