Isopropylation of naphthalene with isopropanol (IPA) proceeds at 200 degreesC over the large pore zeolites HY, H beta, H-Mordenite and REY in the presence of N-2. Over HP, conversion is more in N-2 than when cyclohexane is used as solvent or in absence of N-2. Conversions and selectivities to diisopropyl naphthalenes fall in the sequence H beta > REY > HM > HY, but 2,6: 2,7 ratio is greatest with HM. With H beta, conversion is maximum at 200 degreesC, and increasing the IPA : naphthalene ratio leads to deactivation of the catalyst.