Chlorine and sulfur are the main contaminants present in crude oil.
The presence of Cl and S is undesirable once they contribute to the
complexity of the refining process and may be transferred to
intermediates and petroleum products. In addition, Cl and S may
cause poisoning of catalytic converters and corrosion of internal parts of
combustion engines. In fuels, sulfur is responsible for the emission of
SOx and particulate matter, which endanger public health and
contribute to acid rain