Diesel fuel analysis by GC-FIMS: Normal paraffins, isoparaffins, and cycloparaffins

A reliable and convenient characterization method that provides a detailed hydrocarbon composition profile for transportation fuels is an important pa rt of process optimization directed at reducing regulated emissions. In our previous study (Briker, Y.; Ring, Z.; Iacchelli, A.; McLean, N.; Rahimi P. M.; Fairbridge, C.; Malhotra, R.; Coggiola, M. A.; Young, S. E. Energy Fue ls 2001, 15 (1), 23-37) we described the development of a modified gas chro matography, field ionization mass spectrometry method for detailed hydrocar bon type characterization of diesel fuel. The method proved to be an invalu able technique for rapid analysis of diesel fuel. It was less time-consumin g and more informative than the existing mass spectrometry methods, from a characterization point of view, and it was user-friendly and did not requir e any major modification to an existing commercial instrument, from an inst rumentation point of view. This method correlated well with the other metho ds for total aromatic and saturate groups, and the data fur aromatic subgro ups were verified against the data obtained from other mass spectrometric a nd nonmass spectrometric techniques. This paper describes a continuing effo rt to verify the new GC-FIMS method and produce correlations for the satura te;groups, The purpose of this study was to validate GC-FIMS measurements o f various saturate types using samples of physically separated fractions, e nriched in the individual types by various LC methods described in the lite rature. In this study, the non-normal paraffinic portion of the saturate fr action of the selected diesel cut was separated into iso- and cycloparaffin s. The normal paraffins were quantitatively removed by molecular sieve and additionally determined by high-resolution gas chromatography of the satura te fraction. The contents of iso- and cycloparaffins were calculated gravim etrically in each separated fraction and also analyzed by mass spectrometry methods. The results obtained for the saturate types by different methods were all in good agreement, which demonstrates the applicability of the GC- FIMS method for saturates analysis.