Until recently, it was believed that 50-ppm sulfur would be the
main diesel specification. However, strong signs indicate that
the European Community will drop sulfur specifications to 10
ppm. Equally important, other specifications, such as, PNA,
density and cetane may also change. New, proposed U.S.
legislation is focused on sulfur reductions. In December 2000,
the U.S. EPA published mandates for 15-ppm sulfur diesel by
2006. Some major oil companies have adapted the policy to produce clean burning,
so-called "green", fuels. Consequently, strong drivers do exist
for further product quality improvement.