Study On Structure Of Sulfur And The Properties Of Original Asphaltenes And Secondary Asphaltenes Residues

As we all know, asphaltenes are very complex mixture and the heaviest and the most polar fraction in crude oil and in residues, which also contains a lot of heteroatom, such as sulfur,nitrogen and oxygen and so on. At present, researchers have little known the relationship between sulfur structure and the polarity and the association of the asphaltenes from the thermal reaction of crude oil or residues. In order to studying the relationship between sulfur structure and the properties of asphaltenes, The original n-heptane asphaltenes and the maltenes were separated from Middle East atmospheric residue(in which the content of asphaltenes were low), or from Sha Qing vacuum residues(in which the content of asphaltenes were high).The XANES spectra of original asphaltenes and secondary asphaltenes by X-ray absorption near edge structure spectroscopy. And the spectra had been normalized and taken off the background by Athena software. And we had employed second and fourth derivatives spectra to improve the resolution of spectra. Using the least square fit and correction factors calculates the content and the structure of sulfur in asphaltenes. The results showed that the forms of sulfur are the same in original and secondary asphaltenes, including thiophene, sulfoxide, sulfone and sulfate.In order to study the relationship between the content, the structure of sulfur and the polarity of asphaltenes, we had studied the polarity of original asphaltenes and secondary asphaltenes. And we used the mean dipole moment characterized the polarity of asphaltenes, the acquisition of the mean dipole moment need three parameters: the mean molecular weight, Dielectric constants and refractive index. And then, we find the relationship between the content, the structure of sulfur and the polarity of secondary asphaltenes. The results showed that there was no clear relative between the content of sulfur and the polarity of asphaltenes. The relationship between the structure of sulfur and the polarity were complex, because they also depended on the properties of crude oil and residues.In order to study the relationship between the content, the structure of sulfur and the association of asphaltenes, we had studied the association of original asphaltenes and secondary asphaltenes. The association of asphaltenes had already been characterized by 1H-NMRspectrometry. And then, we find the relationship between the content, the structure of sulfur and the association of secondary asphaltenes. The results showed that there was no clear relative between the content of sulfur and the association of asphaltenes, there was also no clear relative between the structure of sulfur and the association of asphaltenes.