Characterization Of Molecular Structure In Residue Subfractions Via Selective Desulfurization

As raw materials, Gudao residue, Arabia light residue and Venezuela residue weredivided into saturates, aromatics, resins and asphaltenes through SARA method, singlecomponent proceeding selective desulfurization reaction by Raney nickel under mildexperimental condition respectively; C-S bond in non-hydrocarbon macromolecules ofresidue subfractions raptures, while maintaining other chemical bonds damages does notoccur at the same time. This moderate degradation method can lower molecular complexity,which retains other structural information in maximum limit meanwhile. On the basis ofchemical degradation method, the paper conducts detailed research through various physicalinstrument analysis methods, for instance, element analysis, determination of molecularweight, infrared spectrum, gas chromatography, simulated distillation, nuclear magneticresonance hydrogen spectrum, high resolution mass spectrometry and so on, in order tounderstand chemical structure of components deeply.The research shows that sulfide of residue saturates mainly exists in the form of sulfurethers, which ring sulfur ethers is priority to alkyl chain sulfur ethers among them. Sulfide ofresidue aromatics and resins mainly exists in the form of thiophene and sulfur ethers, whichthiophenes is given highest priority, ring sulfur ethers less, alkyl side chain sulfur ethersconnected to the aromatic ring least. In addition, with residue components becoming heavier,the content changes of ring sulfur ethers is the exact opposite of thiophenes; the formergradually reduces, yet, the latter increases. Alkyl chain sulfur ethers of residue solublecomponents is sulfide that carbon number of substituted group is less than five, which iscompounds containing-SCH3substituted group primarily.The results of negative-ion ESI FT-ICR MS show that molecular structure of Gudaoresidue aromatics and resins doesn’t exist sulfide bridge connecting aromatic fused ring. Aromatic rings of N1S1compounds in aromatics present cata-condensed form. With theincreasement of DBE, aromatic ring number add by degrees and the molecular structure ismore and more complex; in addition, the position of heteroatom in the molecular structure isalso different. Sulfur atoms appear in the form of thiophene ring, nitrogen atoms locate insideof aromatic ring structure in the form of pyrrole ring, oxygen atoms of N1O1compounds inaromatics are likely to exist in the form of furan ring. Among aromatic rings of N1S1compounds molecular structure in Gudao residue resins, peri-condensed forms are givenpriority to cata-condensed forms. Sulfur atoms are largely linked to outer fused aromaticrings through the thiophene ring aside, while sulfide that both sides of thiophene rings arejoined to aromatic ring is less. Nitrogen atoms are situated on the aromatic cyclic structure,presenting the layout of pyrrole rings connected to aromatic ring system outside. Molecularstructure of N1S2compounds appears underlinear arrangement. Both of sulfur atoms exist inthe form of thiophene ring; one is located in the internal molecular structure and the other issituated in the end position of molecular structure. Nitrogen atoms are mostly attached toaromatic ring structure in the form of pyrrole ring. In N1O1compounds of Gudao residueresins, oxygen atoms are likely to be the shape of hydroxyl rather than the shape of furan ring.Additionly, among N1O2compounds of Gudao residue resins, oxygen atom is highly possibleto be the form of carboxyl group, existing in the structure of carboxyl side chains connectedwith nitrogen-containin fused aromatic rings pyrrolo.