Evolution of Asphaltene Structure during Hydroconversion Conditions

The evolution of asphaltenes has been studied under hydroconversion conditions with an ebullated bed on a Buzurgan (Middle Eastern) feedstock. A bench unit was used to produce effluents in residue conversion conditions in the range of 55−85 wt %. Under those conditions, asphaltene conversion was observed in the range of 62−89 wt %. Asphaltenes from the feedstock and unconverted asphaltenes were then characterized using size exclusion chromatography (to evaluate asphaltene size) and 13 C nuclear magnetic resonance (to evaluate the evolution of the average molecular structure parameters of asphaltenes). The work clearly shows that (i) the asphaltene unit size decreases when conversion increases and (ii) the aromaticity of asphaltenes increases due to dealkylation.