Selective alkylation of benzene with isopropyl alcohol over H3PO4-ZSM-5 catalyst

A comparative study of the reaction parameters involving the vapour phase isopropylation of benzene with isopropyl alcohol (IPA) over H-ZSM-5 and P-ZSM-5 catalysts was conducted to evaluate the performance of these two catalysts for the industrially important cumene synthesis. Evaluation of catalysts for isopropylation of benzene reaction using isopropyl alcohol 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 SiO2/Al2O3 ratio (60-170) of the zeolite, P content, reaction parameters such as reaction temperature, molar ratio of benzene and isopropyl alcohol, space velocity, and time on stream was studied. Maximum conversion of benzene (12%) was observed at 523 K over 11.0 wt.% P-ZSM-5 (TOS = 3 h). The reaction selectivity on 11.0 wt.% P-ZSM-5-60 (SiO2/Al2O3 = 60) was higher ( > 97%; TOS = 6 h) than that of the most active H-ZSM-5 catalyst (74%) at the same temperature. Cumene selectivity over 11.0 wt.% P-ZSM-5-60 was found to stay over 70% with increase in time on stream (up to 16 h) when the feed used contained an IPA/benzene molar ratio 1:8.