Chemical characterization of heavy oils using HPLC/FI-MS. Analysis of a petroleum vacuum residue.

Abstract

An analyticalsystem, in which a combination of two-stage HPLC and field ionization-mass spectrometry (FI-MS) are used and the results being processed with a computer, was applied to obtaining information on main chemical components contained in vacuum residue derived from crude oil. In the present study, a high degree of analytical accuracy, more so than in case of coal tar or coal derived liquids, should be strived for, because vacuum residue contains more complex chemical components.The sample oil, vacuum residue derived from Arabian crude oil, was preseparated into 4 fractions by HPLC on silica gel columns, followed by further separation into totally 22 subfractions on cyano columns or ion-exchange resins.The data obtained from FI-MS analysis of all subfractions were presented in a tabular form with 14 columns by the computer so that members of any homologous series appear in the same column.The components in sample oils were classified into identifiable 75 compound classes. Based on these analytical data, the ratio of elements, number average molecular weight and aromaticity of the vacuum residue were calculated, which values being compared with measured values in order to evaluate the validity of the present analytical system.

Photochemical Desulfurization and Denitrogenation Process for Vacuum Gas Oil Using an Organic Two-Phase Extraction System

“…The desulfurization reactivity of individual sulfur-containing compounds in VGO was then studied in detail by means of FI-MS. Based on the molecular weight data thus obtained, the sulfur compounds in VGO were classified into seven compound fractions. This was done in accordance with the methods of Ueda et al . and Aoyagi et al , as follows: where sulfur compounds, having the same number of naphthenic and aromatic rings, are involved in each U value.…”

High-Resolution Field Desorption/Ionization Fourier Transform Ion Cyclotron Resonance Mass Analysis of Nonpolar Molecules

“…However, ion yield from FI/FD is considerably lower than from EI or CI, and sector analyzers require a high ion number to attain high mass resolution. Moreover, a sector mass analyzer requires a long scanning time (many seconds per decade in mass) to cover a wide mass range at high resolution, making it difficult to couple with dynamic sample introduction such as GC/FI-MS or FD-MS. As a result, FI/FD has typically been coupled with low-resolution mass analyzers to generate a molecular weight distribution , or to yield composition of fractionated petroleum samples (e.g., saturates and aromatic ring fractions by liquid chromatography separation). , Although FI has been coupled to GC/quadrupole MS for compositional analysis of diesels, , the method cannot access higher boiling point (650+ °F) petroleum molecules as a result of overlap of multiple elemental compositions at each nominal mass. Recently, FI has been coupled to GC high-resolution time-of-flight MS for detailed speciation of hydrocarbons .…”

A Review on Extraction and Identification of Crude Oil and Related Products Using Supercritical Fluid Technology

“…In the literature, several fractionation and isolation schemes based on different chemical class have been proposed − depending upon the type of crude oil available. Because of the complexity of crude oils, preliminary fractionation according to chemical class usually precedes identification of individual components.…”

“…Several different versions of the ABN method have been reported in the literature. 20,21 Recently, Rudzinski et al 22 used the ABN approach to isolate and characterize the components of a Maya crude oil vacuum residue into high polarity, acidic, and basic as well as saturate and aromatic, low polarity NSO, and medium polarity NSO compounds. These fractions were further characterized by liquid chromatography/atmospheric pressure chemical ionization/mass spectrometry (LC/APCI/MS).…”