GB692098A - Improvements in or relating to the purification of naphthalene - Google Patents

Abstract

Oxidizable impurities are removed from naphthalene by converting the naphthalene to the vapour phase, mixing with it the amount of air necessary to convert the oxidizable impurities to carbon dioxide and water and bringing the mixture into contact at elevated temperature with a fluidized oxidation catalyst consisting of an oxide of iron, copper, silicon, manganese, nickel, cobalt, chromium or cerium or of a mixture of two or more of these and preferably supported on a carrier. The particle size of the unsupported fluidized catalyst may lie within the range 40-120m and of the supported catalyst within the range 40-150m . The support may consist conveniently of activated g alumina. Iron oxide is the preferred catalyst and it may be mixed with an alkali, e.g. sodium carbonate. The temperature of the oxidation reaction is maintained at 350 DEG to 500 DEG C. by passing the mixture of air and naphthalene vapour upwardly through the catalyst bed at a linear velocity of 0.1 to 0.5 foot/second. The catalyst carried from the reaction chamber in the gas stream is separated while the naphthalene is still in the vapour phase, e.g. by passing the vapours through a cyclone, and then subjecting the vapours to fractional condensation for the recovery of the pure naphthalene. When the catalyst becomes fouled by the deposition of carbonaceous material, its activity can be restored by burning off the deposited material. In the examples impure naphthalene is purified by passing its vapour mixed with air through an iron oxide catalyst.