The transformation of a mixture of methylcyclohexane and a small amount of phenol, as representative of the transformation of a mixture of biomass-derived oxygenates and Fluid Catalytic Cracking (FCC) feedstock was studied at 350 and 450 degrees C over a USHY zeolite. At 350 degrees C, the addition of phenol increases the deactivation of the zeolite catalyst, which is due to phenol adsorption on both Bronsted and Lewis acid sites, in addition to the formation of coke from methylcyclohexane. Whatever the contact time and the phenol amount, this deactivation is always partial, which suggests that a substantial portion of the active sites of the HY zeolite is not affected by deactivation. Finally, the increase of the reaction temperature (to 450 degrees C) allows limiting the effect of phenol addition on the zeolite activity and stability. (C) 2008 Elsevier B.V. All rights reserved.