One and two-dimensional NMR methods for elucidating structural characteristics of aromatic fractions from petroleum and synthetic fuels

A range of one-dimensional and two-dimensional NMR methods have been used to elucidate the structural characteristics of a set of monoaromatic fractions separated from petroleum, coal, and shale-derived distillate fuels. Gated spin-echo (GASPE) spectral intensities yield a variety of chemically comprehensible average structure parameters. These include the number of carbon atoms per molecule, the number of side chains per molecule, the number of carbon atoms per side chain, the number of side chain branches per molecule, and the number of side chain rings per molecule. Additional structural characterization has been sought through more detailed spectral interpretation. The assignment of NMR resonances has been facilitated by the use of selective heteronuclear correlation (SHECOR) spectra, coupled and decoupled heteronuclear correlation 2D NMR spectra, the heteronuclear relayed coherence transfer (RELAY) 2D NMR method, and homonuclear correlation (COSY) 2D NMR spectra. Wherever possible, spectral assignments have been supported by a range of NMR information including CH/sub n/ type (n = 0-3), /sup 1/H chemical shift, /sup 13/C chemical shift, /sup 1/H-/sup 13/C resonance connectivity, /sup 1/H-/sup 1/H resonance connectivity, and /sup 1/H multiplicity. As a result, the average numbers of ..cap alpha..-, ..beta..-, and ..gamma..-CH/sub 3/ groups per molecule have been calculated. Also, a range of specific structures has been identified, including methyl, ethyl, propyl, butyl, tetralin ring, indan ring, and 1-methylindan ring side chains. Overall, the information collected is sufficient to identify structural similarities and differences for the samples investigated. 52 references, 10 figures, 3 tables.