Characterization of Asphaltenes from Brazilian Vacuum Residue Using Heptane−Toluene Mixtures

Abstract

Brazilian vacuum residue (VR) was separated into insoluble and soluble fractions using n-heptane−toluene mixtures (Heptol). Coking tests performed on the soluble fractions showed that asphaltenes vary in regard to the extent to which they form coke. VR asphaltenes were subfractioned into AS 0−10%, AS 10−20%, AS 20−30%, and AS 30−40% by stepwise extraction using Heptol. The AS 20−30% and AS 30−40% fractions had greater aromaticity and a higher proportion of quaternary aromatic carbons, as well as a larger unit size. These type II asphaltenes produced more coke than did type I asphaltenes, which consist of the AS 0−10% and AS 10−20% fractions.

Investigation of structural parameters and self-aggregation of Algerian asphaltenes in organic solvents

“…According to chemical structure, asphaltenes are aromatic polycyclic molecules surrounded and linked by aliphatic chains and heteroatoms (sulfur, nitrogen, oxygen) as well as traces of metal elements like nickel, iron, and vanadium. The chemical composition and structure of single asphaltene molecules can be assessed using different analytical techniques (Calemma et al 1995;Shirokoff et al 1997;Pekerar et al 1999;Bouhadda et al 2000;Buenrostro-Gonzalez et al 2002;Groenzin and Mullins 2000;Ancheyta et al 2002;Ibrahim et al 2003;Khan et al 2003;Avid et al 2004;Acevedo et al 2005;Siskin et al 2006). Elemental analysis, mass spectroscopy, and 1 H NMR can be used for determination of the average structural parameters such as the aromatic carbon ratio, the average number of alkyl side chains, and the degree of peripheral aromatic carbon substitution (Dereppe et al 1978;Dickinson 1980;Daaou et al 2008Daaou et al , 2009).…”

Separation of Asphaltene by Dimethyl Ether

“…H/C atomic ratio was determined by elemental analysis, hydrogen distribution was determined by nuclear magnetic resonance spectrometry ( 1 H-NMR) using a JEOL model Lambda 500 spectrometer 13) , and classified into aromatic hydrogen (Ha), benzylic hydrogen (Hα), hydrogens attached to methyl groups in long side chains (Hγ), and other aliphatic and naphthenic hydrogens (Hβ). Carbon aromaticity was determined by 13 C-NMR using an inverse gated decoupling system (NNE, pulse width of 4.85 μs, acquisition time of 0.967 s, pulse delay of 7 s). The resulting spectrum was the product of 7000 scans.…”

Upgrading of Heavy Oil by Hydrogenation through Partial Oxidation and Water-gas Shift Reaction in Supercritical Water

“…The average molecular structure of asphaltene was estimated according to the published methods 24), 25) using average molecular weight, elemental analysis, and hydrogen-type distribution. Figure 11 shows the average molecular structures of raw asphaltene, asphaltene obtained in SCW at 673 K, and asphaltene obtained in SCW H2 CO2 at 673 K. The structure consisted of monomers and dimers.…”