ХАРАКТЕРИСТИКА ТЕРМИЧЕСКОЙ УСТОЙЧИВОСТИ МАСЕЛ ПРИРОДНЫХ БИТУМОВ И НЕФТЕЙ

The relevance of the research is caused by the fact that  thermal destruction is one of the most common processes of refining oil residues, heavy oils, and natural bitumens. Thermal and thermocatalytic processes of conversion of the above mentioned hydrocarbon feedstocks are accompanied by formation of supplementary distillate fractions («secondary» oils) during thermal degradation of resin-asphaltene substances of initial objects. Transformation of oils of the initial object and «secondary» oils occurs simultaneously at temperatures corresponding to the thermal disruption of «weak» and «strong» bonds in their constituent compounds. When choosing the optimum modes of thermal and thermocatalytic processing of heavy oil feedstock, the results of assessment of thermal stability of its components should be taken into account. One of the methods for studying the thermal stability of sedimentary organic matter is the Rock-Eval pyrolysis. Information about the potential of this method for analysis of oils is very limited. However, the information on their thermal stability and characteristic temperatures of destruction of their constituents could be obtained from the pyrogram of oils. The analysis of the pyrogram will also provide information on the difference in these parameters for oils isolated from crude oils and natural bitumens, sampled in various oil provinces and significantly differing in their component composition. The main aim of the research is a comparative analysis of thermal stability of oils isolated from natural bitumens and crude oils differing in the total content of resin-asphaltene substances, products of their laboratory biodegradation and conversion in supercritical water using the Rock-Eval method. Objects: oils isolated from 18 samples of crude oils and natural bitumens, products of their laboratory biodegradation and conversion in supercritical water. Methods: elemental analysis, NMR 1Н-spectroscopy, Rock-Eval pyrolytic analysis. Results. It is shown that the information on thermal stability of oils isolated from crude oils and natural bitumens sampled in various oil provinces and differing in their component composition could be obtained via Rock-Eval pyrolysis. The presence of three peaks characteristic for oils is evident from the pyrograms. They are observed within different temperature ranges. Hence, S1 peak (isotherm 180 °C) corresponds to the process of the gasoline fraction (initial boiling point (IBP)…180 °C) evaporation. The S2a peak (180…350 °С) corresponds to overlapping of evaporation of intermediate fractions of oils and rupture of «weak» C–S, C–O bonds in the structural fragments of their compounds. The S2b peak (350…550 °С) corresponds to overlapping of evaporation of high-boiling fractions of oils and rupture of «strong» C–O, C–C bonds in their structural fragments. The samples under study differ by more than one order of magnitude (from 0,32 to 3,91) in the ratio of the yields in volatile products at 350…550 and 180…350 °C (S2b/S2a) and in the ratio of the yields in the gasoline fraction of oils – S1 and S2b+S2a (0,044 to 0,518). The samples of oils under study also differ in the temperature of maximum rate of release of hydrocarbons in the course of pyrolysis in the range of S2b peak (from 445 to 466 °C). This difference is more significant in the range of the S2a peak (from 292 to 350 °C).