Structural-group composition and properties of heavy oil asphaltenes modified with sulfuric acid

Details of the change of structural-group composition of heavy oil asphaltenes modified with sulfuric acid and oleum depending on the process conditions have been determined. The effect of the amount and concentration of sulfuric acid, exposure time, and elevated pressure has been evaluated. The formation of sulfo-, sulfono-, phenolic hydroxyl, carboxylic, and carbonyl functional groups has been detected in Fourier transform infrared (FTIR) spectra for the obtained sulfonated asphaltenes. Spectral coefficients have been calculated for asphaltenes and products of their sulfonation according to the main absorption bands in FT-IR spectra. Analysis of spectral coefficients has indicated the relationship of the fraction of newly formed functional groups in sulfonated asphaltenes and process conditions of sulfuric acid modification. The obtained sulfonated asphaltenes have been analyzed as sulfocationites with the evaluation of sorption capacity. It has been shown that the successive modification of heavy oil asphaltenes with sulfuric acid and oleum gives sulfocationite with the static exchange capacity of 3.39 meq/g. The relationship of spectral coefficients and sorption characteristics of sulfonated asphaltenes has been determined.