ABSTRACT
We believe highly useful information for the petroleum chemist on the composition of heavy petroleum fractions can be provided by the right combination of separation and spectroscopic methods. In our experience, chromatographic compound-class separation and nonfragmenting MS analysis of the fractions is usually the most revealing combination as discussed in Chapters 6 and 7. In those cases, when more detail on the nature of the aromatic and naphthenic ring systems and their alkyl substitution is desired, NMR can provide most of the answers. Additional methods are needed for certain specific problems, for example, the determination of polar functional groups or the elucidation of the way vanadium and nickel are bound to the molecules. This is where IR, UV, and x-ray spectroscopy can help. Nondistillable residues and alkane-insoluble petroleum fractions (asphaltenes) can be analyzed by NMR, IR, and x-ray spectroscopy which give average concentrations of certain structural parameters and functional groups. Considerable additional detail is accessible by the application of mild degradation methods such as selective oxidation and mild pyrolysis.
