Alkylation and transalkylation of alkylbenzenes in cymene production over zeolite catalysts

Gas-phase alkylation of toluene with isopropanol and its transalkylation with cumene were investigated at 200, 250, 275 and 300 °C with contact time ranging from 5 to 20 s. These reactions were carried out in a fluidized-bed reactor under atmospheric conditions over USY zeolite and a dual-zeolite based catalyst (DZ) comprising mordenite and ZSM-5. In toluene isopropylation, USY and the dual-zeolite based catalyst showed comparable cymene yield, but the maximum cymene yield over DZ catalyst was obtained at a much lower temperature. Cymene selectivity over USY catalyst increased with increasing feed mole ratio (toluene: isopropanol) from 1:1 to 3:1, while the highest toluene conversion was obtained at optimum equimolar ratio of toluene to isopropanol. The dual-zeolite based catalyst was found to possess the highest conversion in cumene–toluene transalkylation as well as a higher cymene selectivity compared with USY catalyst. Significant cymene yields were noticed in the alkylation of cumene with methanol over USY and the dual-zeolite based catalyst. The apparent activation energy of toluene isopropylation (E2) was found to be higher than the value for cymene isopropylation (E3).