Introduction
Until the
late 1960’s and early 1970, diesel fuel supplied in North America was usually
classified as “above average” quality. These
fuels were produced by a “straight-run” distillation process with little or no
refinery-cracked components in the distillate stream.
Subsequently, due to shrinking availability of
high quality crude oils, the overall diesel fuel quality world- wide has shown
decreasing tendencies. Since crude oil
reserves are being consumed at an ever-increasing rate, a continued downward trend seems
inevitable.
For oil refiners, extra processing and blending is a practical, though not always easy, option for improving some fuel properties; however, it entails compromises. For example, ignition quality can be improved by including more paraffin's, but this inclusion negatively impacts the required low-temperature operability properties. Another possibility is adding aromatics to increase the fuel’s calorific value, but aromatics generally burn poorly and tend to cause smoking. Due to these and other types of diametrical trade-offs, the scope of distillate processing and fuels blending at the refinery is often very limited. Therefore, fuel additives are rapidly becoming the only alternative for obtaining the superior quality necessary in fuel termed as “Premium Diesel Fuel”.