Structural changes of asphaltene in hydrogen donor visbreaking of Venezuelan vacuum residue

Hydrogen donor visbreaking and conventional visbreaking of Venezuelan vacuum residue were studied at 425 ℃ for different reaction time in an autoclave. Changes of average molecular weight, elemental analysis, hydrogen type distribution and average structural parameter of the asphaltenes separated from the feed residues of the two processes and their visbroken residuals were investigated. The results showed that in comparison with conventional visbreaking at the same reaction time, average molecular weight and S/C atomic ratio of hydrogen donor visbroken residuals were lower, however, the H/C atomic ratio and total active hydrogen were higher. The hydrogen donor could reduce the aromatic carbon rate of asphaltenes and increase the naphthenic carbon rate and the ratio of naphthenic ring number to aromatic ring number so as to delay the phase separation and coke formation.