Preparation of a dimethyltetralin by cyclizing an orthotolylpentene phenylhexene using an ultra-stable crystalline aluminosilicate molecular sieve y-zeolite

A method for preparing one or more dimethyltetralins from 5-(o-, m-, or p-tolyl)-pent-1- or -2-ene or 5-phenyl-hex-1- or -2-ene, comprising:

• (a) contacting a feedstock comprising 5-(o,m-, or p-tolyl)-pent-1- or 2-ene or 5-phenyl-hex-1- or -2-ene in liquid form with a solid cyclization catalyst comprising an acidic ultrastable, thermally stabilized or dealuminated crystalline aluminosilicate molecular sieve Y-zeolite that is substantially free of absorbed water, and at an elevated temperature and at a pressure that is sufficiently high to maintain the feedstock substantially in the liquid phase, to thereby cyclize the first feedstock to form a liquid product comprising one or more dimethyltetralins, wherein water is at a concentration in the first feedstock of from zero up to less than about 0.5 weight percent, based on the weight of the feedstock, wherein (1) when the feedstock comprises 5-(o-tolyl)-pent-1- or -2-ene, at least 80 weight percent of the dimethyltetralin product formed is comprised of 1,5-, 1,6-, 2,5- or 2,6-dimethyltetralin or a mixture thereof, (2) when the feedstock comprises 5-(m-tolyl)-pent-1- or -2-ene, at least 80 weight percent of the dimethyltetralin product formed is comprised of 1,5-, 1,6-, 1,7-, 1,8-, 2,5-, 2,6-, 2,7- or 2,8-dimethyltetralin or a mixture thereof, (3) when the feedstock comprises 5-(p-tolyl)-pent-1- or -2-ene, at least 80 weight percent of the dimethyltetralin product formed is comprised of 1,7-, 1,8-, 2,7- or 2,8-dimethyltetralin or a mixture thereof, or (4) when the feedstock comprises 5-phenyl-hex-1- or -2-ene, at least 80 weight percent of the dimethyltetralin product formed is comprised of 1,3-, 1,4-, 2,3-, 5,7-, 5,8- or 6,7-dimethyltetralin or a mixture thereof;
• (b) separating the resulting cyclization product mixture by distillation at reduced pressure into a lighter, lower boiling fraction that comprises the dimethyltetralin product and a heavier, higher boiling fraction boiling above the boiling point of the dimethyltetralin product, and withdrawing the resulting lighter fraction as distillation overhead;
• and
• (c) combining the resulting heavier fraction with a fresh supply of the tolyl-pentene(s) or phenyl-hexene(s) employed in step (a), cyclizing the resulting mixture under the cyclization conditions employed in step (a), and separating the resulting cyclization product mixture under the distillation conditions employed in step (b).