SULFUR COMPOUND TYPE DISTRIBUTION IN NAPHTHA AND GAS OIL FRACTIONS OF KUWAITI CRUDE

ABSTRACT

The need for detailed information on the types of sulfur compounds present in various petroleum cuts has been well recognized by refiners and environmentalists worldwide. This need is growing in recent years in view of the current environmental regulations that limit the sulfur content of transportation fuels to very low levels. In the present work we have studied the distribution of different kinds of sulfur compounds present in light and middle distillates of Kuwait crude oil. A representative sample of Kuwait crude oil was fractionated into naphtha (15-160°C) and 10-15°C cuts in the gas oil boiling range (210-340°C) using an 80L capacity autodistillation unit “AUTODEST-800” according to ASTM 2892. The distribution of various types of sulfur compounds in each of these cuts was quantitatively estimated by capillary gas chromatography equipped with a sulfur chemiluminescence detector. Thiophene and its alkyl derivatives constituted about 60% of the total sulfur compounds in the naphtha fraction. The remaining 40% was composed of mercaptanes and alkyl sulfides. In the gas oil boiling range (210-340) two groups of sulfur compounds, namely, alkyl benzothiophenes and alkyl dibenzothiophenes were present. A major portion of the alkyl benzothiophenes was found in the fraction boiling in the narrow range 235-257°C. Among the alkyl dibenzothiophenes, the concentration of C, and C₂ DBTs decreased while that of higher alkyl DBTs (< C₃-DBTs) increased with increasing temperature. The C₁ and C₂ alkyl DBTs were highly concentrated in a fraction boiling between 280-325°C and these sulfur compounds were absent in the fraction boiling above 330°C. The industrial implications of these results are discussed.