Prediction of cetane number by group additivity and carbon-13 nuclear magnetic resonance

For pure compounds a simple group counting scheme is used to predict the cetane numbers of normal and branched paraffins and singly substituted alkylbenzenes. To extend the counting scheme to hydrocarbon mixtures, carbon-13 nuclear magnetic resonance (/sup 13/C NMR) is used. /sup 13/C NMR is sensitive to the local environment, up to three to four carbon atoms away, of each carbon atom. Intramolecular reactions that are important for ignition kinetics imply that molecular fragments of three or four carbon atoms must be considered. The authors show that group concentrations derived from /sup 13/C NMR spectra are useful in predicting the cetane number of hydrocarbon mixtures.