lsomerisation of Methylnaphthalenes over Acidic Chalcide Catalysts

Central Fuel Research Institute, Dhanbad, Bihar

Manuscript received 24 April 1978, revised 31 March 1980, accepted 31 March 1980

The catalytic vapour phase isomerisation of 1-methylnaphthalene to 2-methylnaphthalene and vice-versa was studied in the temperature range 420-620˚ and at varying liquid hourly space velocities on alumina-silica, alumina-chromia and alumina-boria of several molar compositions in flow systems using both fixed and fluidised bed conditions. The isomeric distribution of the products, as determined by a combination of  spectroscopic and chromatographic methods, was found to be in conformity with the reported equilibrium values. Disproportionation, a competing paralled reaction during the isomerisation of methylbenzenes, did not occur in the case of methylnaphthalenes although some dealkylation to naphthalene was observed at higher reaction temperatures, especially under fixed-bed conditions. The isomerisation of 1-methylnaphthalene apparently obeyed first order rate law with an energy of activation of about 26 k cal/ mol, the value being close to those obtained with the xylenes. On the strength of the experimental evidence obtained, a mechanism involving the 1,2 shift of the methyl group through the formation of a localised complex intermediate has been postulated.