Composition of petroleum heavy ends. 2. Characterization of compound types in petroleum >675 °C residues

The characterization of polar compound types in petroleum residues of b.p. >675 °C are described. The fractions of acids, bases, and neutral nitrogen compounds prepared by the method described in Part 1 (Fuel 1981, 60, 14) were further separated and analysed. Major compound types identified in the acid fraction are carboxylic acids, phenols, pyrrolic nitrogen compounds, and amides. Quantitative estimates of the compound types were made by two infrared methods. Major compound types identified in the bases were pyridine benzologs, amides, and pyrrolic nitrogen compounds; types found in the neutral nitrogen fraction were amides and pyrrolic nitrogen compounds. The average molecular weight of the >675 °C residues was estimated to be 900 after being determined by four different methods.