Catalytic studies toward synthesis of 2,6-dimethylnaphthalene from 1-(p -Tolyl)-2-methylbutane

In this work experiments have been performed in order to study the synthesis of 2,6-dimethylnaphthalene (DMN) via dehydrocyclizing 1-(p-tolyl)-2-methylbutane over Pt/SiO₂, V/Ca/Al₂O₃, and unimpregnated or potassium-impregnated Cr₂O₃/Al₂O₃ catalysts. The obtained liquid product mixture consisted of 1,6-cyclization products (dimethylnaphthalenes) and dealkylated 1,6-cyclization products (2-methylnaphthalene and naphthalene), 1,5-cyclization products (trimethylindanes and -indenes), and fragmentation products (mainly p-xylene and 3-(p-tolyl)-propylenes) and 1-(p-tolyl)-2-methylbutenes. Among 10 possible DMN isomers 1,5-, 1,6-, 2,6-, and 2,7-DMN were identified. Metal catalysts V/Ca/Al₂O₃ (5 wt % vanadium) and Pt/SiO₂ (1 wt % platinum) were slightly more active than unimpregnated commercial Cr₂O₃/Al₂O₃. After 1 h on-stream time the conversion of 1-(p-tolyl)-2-methylbutane was 96 mol % when the artificial contact time (1/weight-hourly space velocity (WHSV)) was 5.7 h at 783 K over unimpregnated Cr₂O₃/Al₂O₃. Potassium impregnation decreased the conversion into 84 mol % because of the decreased Brunauer−Emmett−Teller surface area (from 97 m²/g unimpregnated to 70 m²/g potassium-impregnated catalyst).