Sulphur compounds in mineral oils

The weight % of sulphur does not give an impression of the amount of sulphur compounds, that may be present. For example, with a sulphur content of 5% and an av. 

It is of great value to know which types of sulphur compounds are present in a crude oil, because the various types may behave quite differently in respect to the properties of the crude and of the products that can be obtained from it by physical or chemical methods. According to recent investigations, in lower molecular oil fractions sulphur appears mainly in the form of alkane-thiols, cyclohexane-thiols and thio-alkanes in higher molecular fractions cyclic sulphur compounds of the thiophen type predominate. 

In the case of statistical methods of analysis of sulphur-containing crude oil fractions one generally confines oneself to small corrections on the applied graphs or equations. These corrections, which have been estimated empirically, are valid only for small percentages of sulphur and do not take into account the nature of the sulphur compounds present in the fractions. 

In recent years the intensive study of sulphur compounds, sponsored by several oil companies43, has led to a collection of physical data on many of these compounds, which enables us to predict several properties of sulphur compounds not yet investigated44 45. 

Van Zijll Langhout developed graphs for compounds consisting of C, H and S, analogous to the graphical representation of C -H -O compounds of Van Krevelen46. These graphs, of which Fig. 63 is an example, are based on the ultimate analysis, and can be applied to identify pure sulphur compounds and to analyse simple mixtures 

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