Changes in the Structure of the High-Molecular-Weight Components of a High-Sulfur Vacuum Residue in the Initiated Cracking Process

The transformations undergone by the high-molecular-weight heteroatomic compounds (resins, asphaltenes) of the Novokuibyshevsk Refinery vacuum residue during thermal cracking at 500°C in the presence of additives such as calcium carbonate and calcium acetate were studied. The characteristic changes in the composition of the cracking products depending on the amount of the additive were demonstrated. Based on the data from 1H NMR spectroscopy, elemental analysis, and molecular weight measurements, the structural-group parameters of the resin and asphaltene molecules in the original vacuum residue and in the products of its cracking in the presence of different amounts of the additives were determined. The heterogeneous additives (≤0.5 wt %) afforded deeper degradation of resins and asphaltenes. The resin molecules underwent compaction due to destruction of the saturated rings and aliphatic moieties, followed by an increase in the content of oils in the liquid cracking products composition.