Benzene ethylation has been investigated over fresh ZSM-5 based catalyst in a riser simulator that mimics the operation of a fluidized-bed reactor. Experimental runs for the kinetic study were carried out at four different temperatures (300, 325, 350 and 400 degrees C) for reaction times of 3, 5, 7, 10, 13, and 15 s. Benzene to ethanol (B/E) mole ratio was varied from 1:1 to 3:1. Benzene conversion, ethylbenzene yield and diethylbenzene yield were found to increase with reaction temperature and time for the different temperatures. The maximum benzene conversion of 16.95% in which the main products were ethylbenzene, diethylbenzene and other hydrocarbon as by-products was obtained over the fresh catalyst at 400 degrees C. The experimental results were modeled using quasi-steady-state approximation with catalyst deactivation function based on two different models. Kinetic parameters for benzene ethylation and ethylation of ethylbenzene with ethanol were estimated by non-linear regression analysis. The apparent activation energy of benzene ethylation (E-1) was found to be higher than the value for ethylbenzene ethylation (E-2). In addition, the effect of feed ratio (B/E) on the activation energies and products distribution was also investigated in this study. (C) 2009 Elsevier B. V. All rights reserved.