Isolation And Identification Of Sulfur Compounds In Saturates And Aromatics From Residue

Lungu residue was separated into saturates, aromatics, resins and asphaltenes by SARA method. Saturates were separated into aliphatic hydrocarbons (ALP) and sulfur aliphatic hydrocarbons (S-ALP) by ligand exchange chromatography using silica gel impregnated with CuCl₂, and aromatics were separated into polycyclic aromatic sulfur heterocycles I (PASH₁), polycyclic aromatic sulfur heterocycles II (PASH₂) and polar sulfur Compounds (PSC) fractions by ligand exchange chromatography using silica gel impregnated with PdCl₂. The enrichment of sulfur compounds did not achieve the desired effect, so two-step ligand exchange chromatography was further proposed for the separation of sulfur compounds in aromatics. Aromatics were separated into thiophenes (A-1) and non-thiophenes (A-2) by two-step ligand exchange chromatography. A-1 fraction was further separated into P₁, P₂, P₃ fractions. The structure of the sulfur compounds was identified by gas chromatography-mass spectrometry(GC-MS) and fourier transform ion cyclotron resonance mass spectrometry(FT-ICR MS).The sulfur in saturates and aromatics were 40% of the total sulfur. For the ALP and S-ALP fractions, the sulfur content was 0.06w% and 2.17w% respectively. Total recovery of sulfur compounds amounted to 86.59%. For the PASH1, PASH₂ and PSC fractions, the sulfur content was 2.60w%, 4.18w% and 2.89w% respectively. Total recovery of sulfur compounds amounted to 68.91%, which increased to 77.39% after two-step ligand exchange chromatography.The results indicated that the molecular weight of sulfur compounds in saturates of Lungu residue ranged from 220 to 700 Da. The S₁ class species were in high relative abundance. The range of carbon numbers went from 18 to 48. It contained cycle-ring sulfides and alkyl diphenyl sulfides. The molecular weight of sulfur compounds in PASH₁ varied from 220 to 700 Da, The S₁, S₂, O₁S₁ and O₁S₂ sulfur-containing class species were identified by FT-ICR MS. The S₁ class species, which was the most abundant species in PASH₁, varied over a wide range of carbon number (18⁵0), containing alkyl benzothiophenes and dibenzothiophenes. In PASH2 fraction, the molecular weight of sulfur compounds ranged from 220 to 600 Da. The S₁, S₂, S₃, O₁S₁ and O₁S₂ sulfur-containing class species were identified by FT-ICR MS. The S₁ class species were the most abundant species in the sample. The range of carbon numbers went from 18 to 37. It contained alkyl dibenzothiophenes, naphtho[2,3-d]thiophenes, benzo homologues of Benzo[b]naphtho[2,3-d]thiophenes and Benzo-Bis-[1]benzothiophenes and so on.In PSC fraction, the molecular weight of sulfur compounds ranged from 220 to 660 Da. The S₁ class species were the most abundant species in the sample. The range of carbon numbers went from 15 to 40. It contained alkyl dibenzothiophenes, naphtho[2,3-d]thiophenes and so on.P₁ fraction mainly contained polycyclic aromatic hydrocarbons (PAH). P₂ fraction contained alkyl dibenzothiophenes and naphtho[2,3-d]thiophenes. P₃ fraction contained alkyl dibenzothiophenes, naphtho[2,3-d]thiophenes, Benzo[b]naphtho[2,3-d]thiophenes and Benzo-Bis-[1]benzothiophenes and so on. The results showed that two-step ligand exchange chromatography was an effective method to separate PASH from the PAH in aromatics.