GB1430025A - Preparation of dimethylnaphthalanes - Google Patents

Abstract

1430025 Dimethylnaphthalenes SUN RESEARCH & DEVELOPMENT CO and TEIJIN Ltd 8 June 1973 [9 June 1972 9 Aug 1972 (3)] 27340/73 Heading C5E Dimethylnaphthalenes are prepared by: (a) cyclizing 5-tolylpentane-2 or 5-phenylhexene-2 with an acidic catalyst to form dimethyltetralin; (b) contacting the reaction product of (a) in vapour form with a solid dehydrogenation catalyst at 300-500‹ C. and 0-5000 p.s.i.g. in the presence of H 2 to dehydrogenate the dimethyltetralin to a dimethylnaphthalene selected from the 1,4-, 1,5-, 1,6-, 1,7- and 1,8-isomers; (c) contacting the resulting vapour mixture of DMN and H 2 with a solid acid isomerization catalyst at 275-500‹ C. and 0-500 p.s.i.g. to form a mixture of DMNs including an isomer selected from 1,3-, 1,6-, 1,7-, 2,3-, 2,7- and 2,6- isomers; (d) separating H 2 from the reaction product of (o) and recycling the H 2 to step (a) or (b). Alternatively the H 2 may be separated before the isomerization step (c). The cyclization catalyst may be SiO 2 -Al 2 O 3 , SiO 2 -MgO, SiO 2 -Al 2 O 3 -ZrO 2 , acidic crystalline zeolites or solid phosphoric acid. The dehydrogenation catalyst may be Pt on non-acidic Al 2 O 3 . The isomerization catalyst may be selected from same materials as the cyclization step. 2,6-DMN may be prepared from 5-0-tolylpentene-2 via 1,5-dimethyl tetralin and 1,5-dimethylnaphthalene, the desired isomer being separated from the mixed isomerization product by selective crystallization, the other isomers being recycled to the isomerization.