Catalytic performances of various dealuminated mordenite catalysts for the isopropylation of naphthalene by isopropyl alcohol with decalin or cyclohexane as a solvent were investigated in a high-pressure fixed-bed flow reactor. It was found that dealumination of H-mordenite could substantially improve the catalytic conversion, selectivity and stability. The catalyst with steam treatment at 700 degreesC followed by acid leaching was revealed to exhibit high and comparatively stable conversion of ca. 37% with the high 2,6-/2,7-DIPN ratio of ca. 3. Reaction conditions, such as reaction temperature, pressure, space velocity and solvent, could significantly influence the catalytic performance, except for the 2,6-/2,7-DIPN ratio. The catalytic behavior is discussed in relation with catalyst porosity and acidity. (C) 2004 Elsevier B.V. All rights reserved.