Analysis of heavy ends of petroleum by probe microdistillationmass spectrometry

Abstract

Seven fractions of a 535-675(DEGREES)C distillate of Wilmington, California crude oil were subjected to qualitative and semi-quantitative analysis using probe microdistillation/mass spectrometry. Samples of the saturates, monoaromatics, and three gel permeation chromatographic subfractions of the monoaromatics, diaromatics, and a gel permeation chromatographic subfraction of the polar polyaromatics were introduced via a heated/cooled quartz direct probe and analyzed for their hydrocarbon components. Sample volatilization using linear and non-linear temperature programming facilitated the micromolecular distillations. The 70 eV analysis on the monaromatics GPC fraction 19 was correlated to those obtained from the same sample by 10 eV electron and field ionization. Intensities for ions detected were corrected for variations caused by pressure effects and were plotted versus temperature to produce experimental elimination curves. Non-linear regression analysis was performed on each ion's elimination curve to calculate the maximum intensity, the temperature at which the intensity reached this maximum, and the area beneath the curve. Mass measurements at high and medium resolution were used for the assignment of elemental compositions. Relative area percents for each ion representing only the hydrocarbon components were calculated for each fraction and were tabulated according to carbon number and Z series. ..