Structure and composition of n-pentane and n-heptane asphaltene from different properties crude

C5 and C7 asphaltene were separated from paraffin base Yumen atmospheric residue and naphthene base Merey atmospheric residue by n-pentane and n-heptane respectively using the method of SARA. The structure parameters and functional groups analyzed and characterized systematically by VPO, ¹H-NMR, FT-IR and elemental analysis, in order to comparative studied the differences in asphaltene structure of different residues and asphaltene obtained by different precipitants. The results showed that there was consistent in the functional groups of different asphaltenes basically, but there was some differences in the unit structure of different asphaltene. Yumen paraffinic asphaltenes had significantly higher molecular weight, smaller H_AU/C_A value and higher condensation degree than Merey naphthenic asphaltenes. With the increase of carbon chain of precipitants, the yield (the yield of n-heptane asphaltene was about 80% of n-pentane for the some feedstook) and the H/C of asphaltene decreased, the molecular weight of asphaltene increased. C₇ asphaltenes had higher aromatic carbon ratio ( f _A) and more structure units than C₅ asphaltene. More saturated structure existed in various asphaltenes and the saturate carbon fraction was about 0.5.