Abstract: By selecting characteristic structural model compounds of asphaltenes containing heteroatoms, thermal conversion of hydrocarbons aromatic containing five-membered heterocycles were investigated to gain a deeper understanding of the behavior of asphaltenes in the presence of hydrogen and dispersed catalyst. The results indicate that the presence of different sulfur-, nitrogen-, and oxygen-containing five-membered heterocycles promotes the cracking of continental-type asphaltenes. Under the experimental conditions where fluorene exhibited a light fraction yield of 0, the cracking rate of the tricyclic compounds dibenzothiophene, carbazole, and dibenzofuran reached 16.97%, 40.98%, and 20.44%, respectively, while those of the tetracyclic compounds benzonaphthothiophene, benzocarbazole, and benzofluorenone reached 51.10%, 52.91%, and 24.12%, respectively.An increase in the number of rings on both sides of the heterocycle facilitate their cracking. When the five-membered heterocycle is located within a biphenyl-type molecule, reactions involving the heteroatom can transform the biphenyl continental-type molecule into an archipelagic-type molecule, thereby enabling cracking. The cracking rate of this type of model compound reaches more than 70 %. This pathway promotes the cracking of continental-type asphaltene molecules with such structures. When asphaltene molecules contain five-membered heterocycle, and the heterocycle is peri-condensed with adjacent aromatic rings and situated between them, the presence of heteroatoms facilitates the catalytic thermal conversion of such continental-type asphaltene molecules in the presence of hydrogen.

Key words: continental asphaltene, catalytic thermal conversion in the presence of hydrogen, dispersed catalyst, five-membered heterocycles, cracking