SELECTIVE DIALKYLATION OF NAPHTHALENE WITH HINDERED ALKYLATING-AGENTSOVER HM AND HY ZEOLITES UNDER LIQUID-PHASE CONDITIONS

Liquid-phase alkylation of naphthalene with cyclohexyl derivatives as alkylating agents has been studied over HM and HY zeolites. The reacti on can be carried out efficiently over HY zeolites, for which high con versions and good selectivities in 2,6- and 2,7-dicyclohexyl naphthale nes (DCN) are obtained after very short reaction times. The ratio 2,6- DCN/2,7-DCN is near to 1, as in the case of the isopropylation reactio n over the same catalysts. Such a result is in agreement with the valu es of critical diameters of 2,6- and 2,7-dicyclohexyl and diisopropyl naphthalenes, calculated by molecular mechanics. The 2,6-dicyclohexyl- naphthalene is a crystalline compound which is easily separated from t he reaction mixture by crystallization, which constitutes an interesti ng advantage of cyclohexylation in comparison with isopropylation.