C-14 POLYAROMATICS AS RADIO ISOTOPE TRACERS FOR GRAFTING ANALYSIS DURING HEAVY OIL PYROLYSIS

Labelled polyaromatics, such as C-14 chrysene and C-14 acenaphthylene, have been used as tracers during pyrolysis of a heavy oil residue. Pr ior to this approach the thermal behaviour of 1:1 mixtures of chrysene and Safaniya vacuum residue (VR) were examined using mass spectrometr y and ultraviolet (u.v.) analysis. Chrysene was found to be highly rea ctive, producing dimers and alkylated chrysene materials. From feedsto cks with C-14 chrysene and C-14 acenaphthylene as radio tracers, the d istribution of polyaromatics in the pyrolysed heavy oil fractions were determined. In this series, acenaphthylene was found to be more react ive than chrysene in grafting reactions on heavy oil components. The r adical quenching propensity of polyaromatic additives towards small ra dicals has been confirmed, supporting their anticoke effect when used at high concentration. Interestingly, the diluted polyaromatic tracers did not accumulate in the coke fractions. This result points to weak and reversible bonding reactions of the polyaromatic additives onto th e heavy oil components.