Catalytic pyrolysis of Arab Heavy residue and effects on the chemistry of asphaltene

In an attempt to understand the changes in asphaltene structure during pyrolysis, hydrothermal reactions were performed on Arab Heavy atmospheric residue using FCC catalyst, ZSM-5 zeolite, hydrocracking catalyst (HC-1) and hydroprocessing (NiMo) catalyst in a bench-scale fixed bed reactor. The effect of four different catalysts on pyrolysis reactions showed that the cracking of residue is affected by catalyst type. All four catalysts used in this study are good for achieving hydrocracking selectivity and were found to be effective in conversion of large asphaltene molecules into smaller moieties. Detailed analyses of asphaltenes were carried out using IR, NMR and HP-GPC techniques. These analyses indicated that the mean molecular weight distribution of residue and asphaltenes decreased after pyrolysis reactions indicating the breaking up of larger molecules. The NMR showed the increase of aromatics carbon and aromatic proton contents in asphaltene obtained from all reactions except when using ZSM-5 catalyst. IR analysis showed that there were significant changes in the chemistry of asphaltenes after the pyrolysis of residue. The pyrolysis reactions were performed and the following reaction conditions were maintained; reaction time: 1 h, temperature 400 °C, feed amount (Arab Heavy residue): 10 g, catalyst amount: 5% of feed (0.5 g) and hydrogen gas pressure: 900–1300 psi. The compositional data generated by this work will enhance the understanding of asphaltene structure that will be of great value in improved refining practices, geochemical studies and in assessing performance properties of asphalt.