Photo-oxidative behaviour of crude oils relative to sea pollution: Part I. Comparative study of various crude oils and model systems

The photo-oxidation of three crude oils from Algeria, the Middle East and Venezuela, respectively, is studied under conditions simulating natural ageing (λ > 300 nm, temperatures between 16 and 38°C) of oil films on the sea surface. The kinetic behaviour differs noticeably from one to another; this could be essentially due to the presence or absence of sulphur compounds. Powerful photosensitizers or photophysical stabilizers have no influence on the course of oxidation, whereas a radical trap (hindered amine) lowers the reaction rate noticeably. The study of model systems such as distillates or a synthetic mixture show the importance of polynuclear aromatics in photo-initiation and of alkyl branched aromatics in the radical propagation of oxidation chains.