RELATIONSHIPS BETWEEN DIESEL FUEL IGNITION QUALITY INDICATORS AND COMPOSITION

Relationships between fuel composition and four secondary measures of diesel fuel ignition quality have been established. Composition has be en defined in terms of the fractions of C-13 n.m.r. intensity attribut able to n-alkyl carbon (C(n)) and aromatic carbon (C(ar)). The indicat ors of diesel ignition quality are: a secondary engine test based on a n Institute of Petroleum standard (IP41); an index calculated using bo iling point and specific gravity data based on ASTM D976; a calculated index based on aniline point; and a diesel index (IP21) calculated fr om aniline point and specific gravity. It has been found that all four cetane quality indicators can be adequately described by a very simpl e property-composition relationship of the form, P = aC(n) + bC(ar) c, where P is the property in question and a, b and c are coefficients determined by multiple linear regression using a sample set deriving from a diverse range of petroleum and synthetic fuel sources. The ceta ne quality indicator based on ASTM D976 has been found to give a disti nctly pessimistic view of ignition quality for highly naphthenic diese l fuels, such as are produced via coal liquefaction.