Preparation of coloured pigments for surface coating from petroleum fractions

A petroleum fraction having a boiling range 200–250°C (kerosene), free from aromatic and n‐paraffin hydrocarbons was oxidised by bubbling air at 130–150°C, at normal pressure, in the presence of cobalt naphthenate as a catalyst. Optimum yield of oxynaphthenic acid was obtained after sixteen hours and thirty minutes oxidation at 140°C. Two layers were formed, the bottom product was a viscous liquid insoluble in petroleum ether and alcohols. Oxyacids, mainly hydroxy naphthenic acids, were obtained after treatment and purification of the viscous liquid.