The effect of alkylation route on ethyltoluene production over different structural types of zeolites

Ethyltoluenes (ET) synthesis via different alkylation routes; toluene with ethanol and ethylbenzene (EB) with methanol, was investigated over zeolites with three-dimensional (3D) pore system i.e. SSZ-33, TNU-9, ZSM-5, IM-5, and one-dimensional zeolite MOR in a fluidized-bed reactor in the temperature range 250–350 °C for reaction times of 5–20 s. Alkylation of toluene with ethanol provided higher yields and selectivities to ethyltoluenes over all zeolites. The maximum ET yield achieved for toluene ethylation was 13.7 wt.% using IM-5 and ZSM-5 whereas 12.5 wt.% was obtained in EB methylation over SSZ-33. SSZ-33 provided the highest ET-selectivity of ∼50% due to the combine effect of its 3D topology and 12-ring channels. In contrast to ET selectivity, p-ethyltoluene selectivity was almost the same, ∼26%, irrespective of the zeolite topology. Kinetic studies of toluene ethylation over the zeolites were conducted using power law coupled with time-on-stream deactivation model. A satisfactory correlation between experimental data and the model result was achieved. The activation energy of the various zeolites used for the alkylation of toluene to ET decreased in the order: IM-5 (58.2 kJ/mol) > SSZ-33 (39.7 kJ/mol) > TNU-9 (27.3 kJ/mol) > MOR (20.2 kJ/mol) > ZSM-5 (17.0 kJ/mol) which was explained by different acid strength and nature of the zeolites.