Organosulphur from petroleum sources

Significant amounts of organic sulphur compounds are not directly synthesized in the natural S-cycle and are introduced into the oceans by the discharge of petroleum and heavy fuel oils. Crude oils contain from 0.05 to 14% sulphur the great majority of which have been 0.1 and 3% (Meyer, 1977 Gransch and Postuma, 1973). 

S-containing petroleum compounds have been identified in marine molluscs (Lake and Hershner, 1977). In an investigation of seawater, sediment, and organisms near an oil spill after a collision, Warner (1975) found that the S-components of petroleum can be preferentially concentrated in the marine environment e.g., in the isopod Lygia sp. which had crawled over 

It is generally accepted that most sulphur compounds in petroleum are synthesized by secondary reactions with elemental sulphur as shown by Martin and Hodgson (1973, 1977) in laboratory experiments. Especially the high concentration of sulphur in crudes suggests it to be unlikely that petroleum-type S-compounds are formed from sedimentary oi anic sources most sulphur is probably provided by sulphate reduction and secondary reactions of the products (HzS and S) during early die enesis (Gransch and Postuma, 1973). 

In an attempt to simulate petroleum formation under mild conditions (T 150° C) De Roo and Hodgson (1978) reacted ethylbenzene and sulphur in the presence of oxygen and water and identified a number of S-compounds, among which substituted thiophenes seemed to be the major products (Fig. 7). Baker (1973), however, found only three poorly defined organosulphur compounds on reaction of Beaufort Sea sediments with elemental sulphur, when studying whether hydrocarbons could be generated from the humic material present in the area. 

A detailed analysis of individual sulphur compounds in oil is provided by Rail et al. (1972). In marine samples S-containing petroleum components such as benzothiophene, dibenzothiophene, naphthobenzothiophene, and their alkyl derivatives were obtained by Warner (1975) together with aromatic hydrocarbons. Alterations in the composition of S-compounds in crude oils exposed to the sea surface were analyzed by Utashiro and Hatsuo (1977). 

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