The linkage of aromatic ring structures in vacuum residues was important for the refining process. The Fourier transform ion cyclotron resonance mass spectrometry(FT-ICR MS) combined with collision-induced dissociatio...The linkage of aromatic ring structures in vacuum residues was important for the refining process. The Fourier transform ion cyclotron resonance mass spectrometry(FT-ICR MS) combined with collision-induced dissociation(CID) is a powerful method to characterize the molecular structure of petroleum fractions. In this work, model compounds with different aromatic ring structures were measured by CID FT-ICR MS. The cracking of the parent ions and the generated fragment ions were able to distinguish different linkage of the model compounds. Then, vacuum residues were separated into saturates, aromatics, resins and asphaltenes fractions(SARA), and each fraction was characterized by CID technology. According to the experimental results, the aromatic rings in saturates and aromatics fractions were mainly of the island-type structures, while the aromatic rings in resins and asphaltenes fractions had a significant amount of archipelago-type structures.展开更多
Using heptane, toluene, and tetrahydrofuran （THF） as eluant, asphaltenes were fractionated into five fractions based on their polarity and solubility. The molecular composition of polar heteroatom species in both as...Using heptane, toluene, and tetrahydrofuran （THF） as eluant, asphaltenes were fractionated into five fractions based on their polarity and solubility. The molecular composition of polar heteroatom species in both asphaltene and its fractions were ana- lyzed by negative-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry （ESI FT-ICR MS）. The application of UV-vis spectrometer in characterizing asphaltene composition and measuring asphaltene concentration was discussed. About 11.9 wt% asphaltene components adsorbed permanently on silica gel in the extrography column after exces- sive elution with various solvents. In negative FT-ICR MS, the mass spectra show that acidic and neutral nitrogen-containing compounds such as N1 and NIS1 mainly existe in the first three less polar fractions, while oxygen-containing compounds such as 02, O2S, O2S2, 03, and 04 show high relative abundance in more polar fractions. These results suggest oxygen-containing compounds have stronger adsorption ability with silica gel. It was observed that the double bond equivalence （DBE） distribu- tion of N1 class species in the fractions shifted to higher values while the carbon number shifted to smaller numbers as polarity of fractions increased. This indicates that acidic and neutral Nl compounds with longer carbon chain and less aromaticity have less polarity compared with those with shorter carbon chain and stronger aromaticity. UV-vis absorbance indicats that fractions containing the most aromatic and most polar asphaltene have better absorbance at long wavelength, while the fractions that consist of least aromatic and least polar asphatlenes show high absorbance at short wavelength.展开更多
基金supported by the Major State Basic Research Development Program of China (973 Program, No. 2012CB224801)
文摘The linkage of aromatic ring structures in vacuum residues was important for the refining process. The Fourier transform ion cyclotron resonance mass spectrometry(FT-ICR MS) combined with collision-induced dissociation(CID) is a powerful method to characterize the molecular structure of petroleum fractions. In this work, model compounds with different aromatic ring structures were measured by CID FT-ICR MS. The cracking of the parent ions and the generated fragment ions were able to distinguish different linkage of the model compounds. Then, vacuum residues were separated into saturates, aromatics, resins and asphaltenes fractions(SARA), and each fraction was characterized by CID technology. According to the experimental results, the aromatic rings in saturates and aromatics fractions were mainly of the island-type structures, while the aromatic rings in resins and asphaltenes fractions had a significant amount of archipelago-type structures.
文摘Using heptane, toluene, and tetrahydrofuran （THF） as eluant, asphaltenes were fractionated into five fractions based on their polarity and solubility. The molecular composition of polar heteroatom species in both asphaltene and its fractions were ana- lyzed by negative-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry （ESI FT-ICR MS）. The application of UV-vis spectrometer in characterizing asphaltene composition and measuring asphaltene concentration was discussed. About 11.9 wt% asphaltene components adsorbed permanently on silica gel in the extrography column after exces- sive elution with various solvents. In negative FT-ICR MS, the mass spectra show that acidic and neutral nitrogen-containing compounds such as N1 and NIS1 mainly existe in the first three less polar fractions, while oxygen-containing compounds such as 02, O2S, O2S2, 03, and 04 show high relative abundance in more polar fractions. These results suggest oxygen-containing compounds have stronger adsorption ability with silica gel. It was observed that the double bond equivalence （DBE） distribu- tion of N1 class species in the fractions shifted to higher values while the carbon number shifted to smaller numbers as polarity of fractions increased. This indicates that acidic and neutral Nl compounds with longer carbon chain and less aromaticity have less polarity compared with those with shorter carbon chain and stronger aromaticity. UV-vis absorbance indicats that fractions containing the most aromatic and most polar asphaltene have better absorbance at long wavelength, while the fractions that consist of least aromatic and least polar asphatlenes show high absorbance at short wavelength.
