Composition analysis of aromatics-rich extraction oil from FCC slurry

Abstract

The extracted oil of intermediate base FCC slurry is split into eight narrow fractions with a boiling point interval of 20°C by vacuum distillation. The aromatic composition and constitution of these narrow fractions were determined by measuring their density, carbon residue and kinematic viscosity as well as elemental analysis, 1H and 13C nuclear magnetic resonance (NMR) spectroscopy and comprehensive two-dimensional gas chromatography and time-of-flight mass spectrometry (GC×GC TOF MS). The results indicate that the density, carbon residue and kinematic viscosity of each narrow fraction increases with the increase of boiling point, in particular with a boiling point higher than 420°C. The aromatics consist of mainly tricyclic and tetracyclic aryl hydrocarbons in the narrow fractions with a boiling point lower than 440°C; the content of pentacyclic aromatics increases rapidly with the increase of boiling point over 440°C, though the pentacyclic aromatics are also present in the narrow fractions with a boiling point of 400–420°C. The aromatics in the FCC slurry are highly-condensed and contain a small amount of short-alkyl groups. The heteroatomic compounds in the narrow fractions include mainly sulfur- and oxygen-containing compounds, whereas the content of nitrogen- and halogen-containing compounds is very low.