Preparation of medicinal white oils and medicinal paraffins

A process for the preparation of a medicinal white oil or medicinal paraffin from a petroleum fraction containing aromatics and nitrogen, oxygen and sulfur compounds comprising:

• treating, in a first stage, a petroleum fraction containing aromatics and nitrogen, oxygen and sulfur compounds with an acid selected from the group consisting of sulfuric acid and oleum, and
• hydrogenating, in a second step, over a nickel-containing catalyst under from 50 to 200 bar and at from 160 to 330.degree. C., a space velocity of from 0.1 to 2.0 kg of oil per liter of catalyst per hour and a gas/oil ratio of from 0.1 to 1.0 m.sup.3 /kg to form a medicinal white oil or medicinal paraffin,
• wherein the nickel catalyst, initially present in the oxide form, is first reduced at from 350 to 530.degree. C. with hydrogen or a hydrogen-containing gas, then passivated, without exceeding 450.degree. C., and again activated at above 150.degree. C. with hydrogen, before hydrogenating to said medicinal white oil or medicinal paraffin.