By Jorge Ancheyta
Designed for scientists operating for petroleum and catalyst businesses, this article re-examines the characterization and conversion of asphaltenes.
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Additional info for Asphaltenes : chemical transformation during hydroprocessing of heavy oils
Molecular weight of asphaltenes from the fixed-bed process decreased as conversion of residue was gradually increased; however, large aggregates could be present in the remaining asphaltenes. Dissociation of large aggregates of asphaltenes at lower conversion like that obtained in fixed-bed is less pronounced than in ebullated-bed. Chromatograms of asphaltenes from the feedstock (Buzurgan vacuum residue) with tetrahydrofuran (THF) as solvent showed a bimodal profile, which can be due to two types of aggregates: (1) highly associated asphaltenes with higher molecular weight and (2) less associated asphaltenes with lower molecular weight.
19, where radicals defined as R1 to R4 correspond to alkyl or aromatic bondings. Earlier studies carried out by Moschopedis and Speight (1976a, 1976b), George et al. (1979), and Rose and Francisco (1987) have identified oxygen in carboxylic, phenolic, and ketonic structures. The oxygen in asphaltenes may be present as acidic hydroxyl groups. This was confirmed by the poor interaction of phenol solution with asphaltenes. Asphaltenes can be separated into low- and high-molar weight asphaltenes if acetone extraction in Soxhlet is used.
Molecular weight of soluble fraction (maltenes) is around 700 to 1,600 g/ mol depending on the sample, whereas molecular weight of insoluble fraction (asphaltenes) is between 1,800 and 2,900 g/mol. The source of asphaltenes and maltenes was Heera and Jodhpur Indian vacuum residues. 13) where MWr, MWi, and MWs are the number average molecular weight of the residue, insolubles, and solubles, respectively. wi and ws are the weight fraction of insoluble and soluble fractions in vacuum residues, respectively.
Asphaltenes : chemical transformation during hydroprocessing of heavy oils by Jorge Ancheyta