Measurements of Asphaltenes in Vacuum Residues by Laser Desorption Ionization Mass Spectroscopy

摘要

Molecular weight distribution measurements of asphaltenes in five types of petroleum vacuum residues (VR) were performed by laser desorption ionization mass spectroscopy (LDI-MS).The mass spectrum was obtained by optimizing the contents of the solution and laser power. For Arabian Heavy-VR (AH-VR) asphaltene, its mass spectrum showed a large peak up to m/z 6000 with a bi-modal profile,that is, a small peak near m/z 400 and a large and broad peak near m/z 1500 for the others. Similar distribution profiles were obtained for those in another type of VR. The average molecular weight obtained by mass spectrum was always smaller than that obtained by vapor pressure osmometry or by gel permeation chromatography.