Thermal Analysis Coupled to Ultrahigh Resolution Mass Spectrometry with Collision Induced Dissociation for Complex Petroleum Samples: Heavy Oil Composition and Asphaltene Precipitation Effects

Abstract

Thermal desorption and pyrolysis of various heavy oils and asphaltenes (precipitated with different paraffinic solvents) were studied. For this purpose evolved gas analysis was realized by hyphenation of a thermobalance to ultrahigh-resolution mass spectrometry (FT-ICR MS). The chemical pattern was preserved by applying soft atmospheric pressure chemical ionization (APCI). Collision induced dissociation (CID) was performed for deeper structural insights. Viscous or solid petroleum samples and fractions can be easily measured by the setup. The SARA fractions (maltenes, C7-asphaltenes, aromatics, saturated, and resins), deployed for evaluation purposes, revealed a very complex molecular pattern, and fractionation drastically increased the number of assigned elemental compositions. Species from m/z 150 to m/z 700 and two main phases (desorption and pyrolysis), which transits at roughly 300–350 °C, are observed. Both phases overlap partially but can be separated by applying matrix factorization. The heavy oil...