2,6-Dialkylnaphthalene is prepared from a feedstock comprising naphthalene and an alkylating agent, by a process comprising the steps:(I) transalkylating isomers of dialkylnaphthalene and naphthalene to produce monoalkylnaphthalene and isomers of dialkylnaphthalene;(II) separating the product obtained in step (I) into naphthalene, monoalkylnaphthalene, dialkylnaphthalene and other components;(III) alkylating the monoalkylnaphthalene fraction from step (II) with an alkylating agent to produce dialkylnaphthalene; and(IV) separating 2,6-dialkylnaphthalene from the dialkylnaphthalene fraction in step (II),wherein at least step (I) or step (III) is conducted in the presence of a catalyst having a composition comprising a synthetic zeolite having an X-ray diffraction pattern with an interplanar d-spacing (.ANG.)______________________________________ 12.36 .+-. 0.4 11.03 .+-. 0.2 8.83 .+-. 0.14 6.18 .+-. 0.12 6.00 .+-. 0.10 4.06 .+-. 0.07 3.91 .+-. 0.07 3.42 .+-. 0.06. ______________________________________