The title reaction has been studied on Y, MOR, ZSM-5 and partially dealuminated Y zeolites under standard conditions. The reaction turned out to be rather complex, involving many parallel and/or successive steps. In particular, the reactant can undergo dealkylation, isomerisation and disproportionation in various relative ratios, depending on the nature of the catalyst and on the reaction conditions. Some correlations have been found between the yield to the various reactions and surface acidity and structural characteristics of the catalyst. These correlations allowed to propose a mechanism for the three main reactions and to draw a general scheme of the overall process.