DETERMINATION OF THE MOLECULAR-WEIGHTS OF THE RATAWI VACUUM RESIDUE FRACTIONS - A COMPARISON OF MASS-SPECTROMETRIC AND VAPOR-PHASE OSMOMETRY TECHNIQUES

The molecular weight characteristics of Ratawai vacuum residue fractions are determined using mass spectrometric and vapour phase osmometry approaches. Mass spectrometry involves the controlled sublimation of a thin film of hydrocarbon, from a quartz probe tip, into the instrument. Number average molecular weights and rigorous upper bounds on the number average molecular weights are determined from the mass spectrometry data. The upper bounds are found to be smaller than the values determined by VPO. The mass spectrometry technique is the first step in a direct m.s.-m.s. procedure for evaluation of molecular components in heavy oils. © 1990.