Abstract: The average molecular structural parameters and asphaltene aggregation state of typical Middle East residue and its hydrogenated oil at different conversion depths were determined by NMR (¹H-NMR) and optical microscopy, respectively, and the relationship between structure change and stability of residue during ebullated bed hydroconversion was investigated by combining group composition and instability parameters of the residue. The results showed that the average condensation degree of residue increased firstly and then decreased in the conversion range of 61.87% - 79.71%, which was related to the formation of sediment and its separation from the oil phase. After the residue was hydroconverted in ebullated bed, the aggregation degree of asphaltenes increased significantly, the cluster diameter of asphaltene increased with the increase of conversion rate, the maximum diameter could reach 58.97 μm. In the process of ebullated bed hydroconversion, the content of resins with the role to stabilize asphaltene in residue decreased obviously, while the content of saturated component, which was harmful to the stability of the asphaltenes, increased significantly.This would result in a continuous decrease in the stability of the residue.

Key words: ebullated bed, molecular structure, asphaltene aggregation, group composition, stability