Abbreviations: MS, mass spectrometry; NMR, nuclear magnetic resonance; C/H, ratio of carbon to hydrogen;

f_A, fraction of aromatic carbon; C_T, total carbon number; C_A, aromatic carbon number;

C_S, saturated carbon number; R_T, total number of rings

FIGURE 1 Characterization flowchart of residue oils

The macroscopic properties such as distillation range, density, average molecular weight, etc. of the residue oils were obtained using the corresponding analytical instruments. The residue oil was separated into narrow fractions using supercritical fluid extraction and fractionation (SFEF) technology. Each narrow fraction was separated using Al₂O₃ column chromatography to obtain sub-fractions of saturates, aromatics, resins, and asphaltenes.²⁹ The saturates and aromatics were analyzed to get the ring numbers of naphthenes and aromatics. The resins and asphaltenes were analyzed using the element analyzer, analog distillation instrument, time-of-flight MS, NMR to get the average structure parameters according to the Brown-Ladner method.^30,31 Taking a feed oil of the delayed coking plant from PetroChina as an example, partial characterization results of the residue oil obtained by the aforementioned methods are shown in Table S1, Table S2, Table S3 and Figure S1 in the Supporting Information.