Identification of acidic species extracted from heavy crude oil by fourier transform ion cyclotron resonance mass spectrometry

Acidic species were extracted from heavy crude oil by alcohol-alkali solution and ion exchange resin. The acidic species in the obtained extracts and extracted crude oil were characterized by negative-ion ESI FT-ICR MS. The analytical results indicated that some class species, O₂, O₁, N₁, N₁O₁, N₁O₂, N₁S₁ and O₂S₁ etc., were identified in the negative-ion spectrum, in which O₂, O₁ and N₁ class showed much higher abundance than others. Compared to O₁ and N₁ class, O₂ class could be extracted from heavy crude oil by using the two methods more efficiently, which means that a great majority of O₂ class can be extracted; meanwhile, almost half of O₁ and N₁ class still remained in residual phase. Detailed analysis demonstrated that alcohol-alkali method was effective for extracting O₂, O₁ and N₁ class with lower molecular weight; ion exchange method, however, was helpful to extract higher molecular weight O₁ and N₁ class and showed almost equal extraction selectivity to all kind of O₂ class.