GB611213A - Method for purifying naphthalene - Google Patents

Abstract

Naphthalene is purified by centrifugally extracting the major part of the hydrocarbon oils occluded in the naphthalene crystals, washing the mass, preferably in the same centrifugal apparatus, with an auxiliary liquid or liquid mixture having a boiling point of not more than 190 DEG C. and the surface tension of which is lower than that of the occluded hydrocarbon oil to be removed, purifying the raw washed naphthalene by treatment with soda and sulphuric acid, and separating commercially pure naphthalene from the auxiliary liquid or liquid mixture by fractional distillation. The substitution may also be effected by filtering under vacuum, suction, or successive diffusions and a suitable liquid is an oil fraction from coal distillation boiling between 160 DEG and 190 DEG C. Solvents for naphthalene are generally used, but alcohols may also be used. When solvents are used, it is preferable to saturate initially with pure naphthalene in the cold. After use the washing liquid is regenerated by distillation to extract therefrom the dissolved hydrocarbons and is then recycled. In an example, crude naphthalene oil resulting from the distillation of coal tar is centrifuged and the product then washed in the centrifuge with commercial xylene having a boiling point of 140 DEG C. The washed naphthalene is then treated with soda and sulphuric acid and then fractionally distilled to remove the xylene.