The Kinetics of the catalytic oxidation of naphthalene

Abstract

The vapor phase catalytic air oxidation of naphthalene was studied over various catalysts and in the presence of a large excess of oxygen. Over a catalyst of fairly regular shape made by fusing vanadium pentoxide into pellets, the progress of the reaction with time was investigated. Overall first-order rate constants obtained ranged from 0.56 sec. −1 at 340°C. to 32.9 sec. −1 at 475°C., with an activation energy of 29 kg.-cal. Naphthoquinone, phthalic anhydride, and carbon dioxide were found to be formed from naphthalene in simultaneous reaction steps and in the approximate respective proportions of 0.4 to 0.4 to 0.2. Naphthoquinone underwent subsequent conversion to phthalic anhydride. This branching of the primary step was found to occur with various vanadium pentoxide catalysts, and the extent of branching was compared. For a fluidized vanadium pentoxide oxidation catalyst modified with a large content of potassium sulfate, a consecutive reaction mechanism was found to apply. In the fixed bed laboratory operation, mass transfer effects became significant only above 450°fC. Below this temperature, rates were controlled by chemical reaction.