A reliable characterization method giving a detailed hydrocarbon composition profile for transportation fuels is an important part of any process that optimizes fuel reformulation and engine design to reduce regulated emissions. This study describes the development of a modified gas chromatography field ionization mass spectrometry (GC-FIMS) method for detailed hydrocarbon type determination of diesel fuel. Diesel fuels were analyzed by GC-FIMS, and the calculated hydrocarbon type composition profile was compared with that determined by other standard techniques. Results for total saturates, total aromatics, monoaromatics, and polyaromatics contents correlated well. Selected ion chromatograms demonstrated the separation of isoparaffins and normal paraffins in typical diesel fuels. The GC-FIMS method produced results for isoparaffin, normal paraffin, and cycloparaffin contents that did not require sample pretreatment to separate saturates and aromatics fractions. Analysis of a gasoline sample showed excellent agreement between GC-FIMS and detailed hydrocarbon analysis or PIONA for total cycloparaffin content, and reasonable agreement for iso-and normal paraffin contents. The normal paraffin contents of selected diesel blends measured by GC-FIMS correlated well with that measured by other methods. Experiments with internal standardization verified the accuracy of the GC-FIMS method for selected hydrocarbon isomers.

A reliable and convenient characterization method that provides a detailed hydrocarbon composition profile for transportation fuels is an important part 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 Fuels 2001, 15 (1), 23-37) we described the development of a modified gas chromatography, field ionization mass spectrometry method for detailed hydrocarbon type characterization of diesel fuel. The method proved to be an invaluable technique for rapid analysis of diesel fuel. It was less timeconsuming and more informative than the existing mass spectrometry methods, from a characterization point of view, and it was user-friendly and did not require any major modification to an existing commercial instrument, from an instrumentation point of view. This method correlated well with the other methods for total aromatic and saturate groups, and the data for aromatic subgroups were verified against the data obtained from other mass spectrometric and nonmass spectrometric techniques. This paper describes a continuing effort to verify the new GC-FIMS method and produce correlations for the saturate groups. The purpose of this study was to validate GC-FIMS measurements of various saturate types using samples of physically separated fractions, enriched in the individual types by various LC methods described in the literature. In this study, the non-normal paraffinic portion of the saturate fraction of the selected diesel cut was separated into iso-and cycloparaffins. The normal paraffins were quantitatively removed by molecular sieve and additionally determined by high-resolution gas chromatography of the saturate fraction. The contents of iso-and cycloparaffins were calculated gravimetrically 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.

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