MODIFICATIONS INDUCED BY VISBREAKING ON COMPOSITION AND STRUCTURE OF ATMOSPHERIC RESIDUES

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Abstract
The atmospheric residues, the corresponding visbroken residues and the related asphaltenes have been characterized by elemental analysis, liquid and gel permeation chromatography (LC, GPC), nuclear magnetic resonance (NMR) and pyrolysis/gas chromatography/mass spectrometry ( Py/GC/MS) before and after the thermal process. The results show that visbreaking (VB) increases the aromaticity (Car) of the residues and decreases their resins/ asphaltenes ratio. A relationship between δCar and resins/as-phaltenes ratio has been found. The cracking of aliphatic chains which takes place during the thermal process produces asphalthenes with lower molecular weight and more condensed aromatic structures. The rise up to 60% of the ratio of aromatic to paraffinic carbon (Car/Cp ( greatly affects the solubility of VB asphaltenes in a oily medium.