Preparation of .beta.-isopropylnaphthalene

A continuous process for preparing .beta.-isopropylnaphthalene comprising

• (a) alkylating naphthalene with propylene by introducing these two compounds into a multiplicity of reaction zones at a temperature between about 150.degree. and 280.degree. C. and a pressure between about 5 and 30 atm in the absence of a normally liquid solvent and in the presence of a phosphoric acid catalyst supported on a SiO.sub.2, this introduction being effected in amounts to obtain a mol ratio of 1/5 to 1/20 mol of propylene to 1 mol of naphthalene in each reaction zone until 45 to 65% of the naphthalene are converted in the entire alkylating reaction to an isomeric mixture of .alpha.- and .beta.-isopropylnaphthalene, then
• (b) charging said isomeric mixture into an isomerization zone wherein said mixture is heated to a temperature between about 180.degree. and 280.degree. C. at an inert gas pressure of between about 5 and 30 atm and in contact with said phosphoric acid catalyst supported on SiO.sub.2 until no further .beta.-isopropylnaphthalene is formed,
• (c) whereupon the .beta.-isopropylnaphthalene is recovered from the isomerization zone at a purity of about 90 to 95%.