The catalytic transformation of methylcyclohexane (mcha), as representative of the reactions taking place during catalytic cracking, was carried out on a H-EU-1 zeolite under the following conditions: 623 K, atmospheric pressure, PN2/P-mcha ratio equal to 9, contact time (taken as the reciprocal of the weight hourly space velocity) between 0.016 and 0.3 h. Whatever the contact time and time-on-stream, cracking was the main reaction, like on other 10-MR zeolites, but significant amounts of isomers and aromatics were produced. Moreover, cracking led predominantly to branched products, in contradiction with the shape selectivity expected from the narrow pore openings of this 10-MR zeolite. All this could be explained by a very important catalytic contribution of the protonic sites located at the pore mouths. Additional experiments using bulky basic compounds (gamma-collidine) confirmed this hypothesis and allowed estimation of the selectivity of these acid sites. (c) 2008 Elsevier Inc. All rights reserved.