The reaction of naphthalene with benzyl chloride in cyclohexane at 80 C was carried out in a slurry batch reactor, over an MCM-41 aluminosilicate catalyst. The concentration of benzyl chloride and of the products, two benzylnaphthalene isomers (M) and a mixture of several dibenzyl derivatives (D), was determined as a function of time, in runs where the initial concentrations of both reactants were varied (C-BzCl(0) from 0.03 to 0.05 mol/l; C-NA(0) from 0.20 to 0.30 mol/l). Kinetic models were applied in order to interpret the measurements.