In this paper, a transient pseudo-homogeneous model was developed with the objective of describing the activity, product distribution and deactivation with time on stream for the methylcyclohexane transformation over H-USY at 350 degrees C. The reaction scheme details the reactant, cyclopentane ring isomers, alkenes, alkanes, aromatics and coke. The existence of adsorbed species is neglected, exception made for coke molecules that remain trapped inside the catalyst, being responsible by the catalyst deactivation. The effect of a model basic nitrogen molecule (quinoline) in the feed is also described by the model; both its roles as a poison and as coke precursor are accounted for. The fitting was done using data determined experimentally at 350 degrees C for 1/WHSV (weight hourly space velocity) values of 12 and 4 min, as a function of time on stream. The model fits extremely well the activity, deactivation and product distribution, coke included. (c) 2006 Elsevier B.V. All rights reserved.