Characterization of Heavy Crude Oils, Their Fractions, and Hydrovisbroken Products by the Asphaltene Solubility Fraction Method

Abstract

An improved method for the separation of asphaltene solubility fractions is presented and has been proven useful for the characterization of heavy crude oils and their fractions. Mixtures of heptane, dichloromethane, and methanol are used to obtain four different and well-defined asphaltene fractions with increasing solubility parameter. A good correlation (0.95) is found between the solubility fraction method and the gravimetric asphaltenes for virgin materials. For processed samples, the correlation depends upon the type of conversion process chosen [fluidized catalytic cracking, thermal cracking, or hydroprocessing]. The characterization of asphaltenes by the asphaltene solubility fraction method for a heavy oil feed and its visbroken products indicated that the low solubility parameter asphaltenes are processed first (“easy-to-react”) and then the higher solubility parameter counterparts (“hard-to-process”). Preparative separations and characterization of Mexican vacuum residue asphaltenes and a thermally cracked residue were carried out using an automatic solvent extractor (ASE) apparatus and the same set of solvents as the solubility fraction method. The results indicated that the H/C ratio of the extracted asphaltene fractions decreased and the aromaticity increased with the solubility parameter of the solvent. However, small differences in the distributions of asphaltene fractions were observed and were attributed to the larger precipitant/sample ratio used in the asphaltene solubility fraction method (>50:1) compared to the ASE preparative separation (20:1).

Fractionation and Characterization of Petroleum Asphaltene: Focus on Metalopetroleomics

“…Meaningfully, it can be automated and be used online [119]. This new solvent system was improved by Ovalles et al [72], making the on-column methodology more robust and repeatable. They used mixtures of heptane, DCM, and methanol in an attempt to make changes in solubility parameters quantifiable and gradual.…”

“…Rogel et al [72] separated Mexican vacuum residue asphaltenes and a thermally cracked residue using an automatic solvent extractor (ASE) apparatus. The characterization results showed the H/C ratio decreasing and aromaticity increasing with the solubility parameter of the solvent and the most polar asphaltene fractions having the highest concentrations of vanadium and nickel.…”

Characterization of Asphaltene Fractions: Distribution, Chemical Characteristics, and Solubility Behavior

“…Figure 1 shows a summary of the scheme used for the fractionation. 12 Solubility Profile. Solubility profile analyses were carried out in all the fractions using the following procedure: solutions of the samples in methylene chloride were prepared and injected in a column packed with an inert material using n-heptane as the mobile phase.…”

Characterisation of subfractions of asphaltenes extracted from an oil sand using NMR, DEPT and MALDI-TOF

“…Many previous reports have discussed the trends amongst subfractions when using similar binary solvent systems, for example aromaticity was found to monotonically increase across subfractions with decreasing solubility and H/C ratio (Buch et al, 2003;Buenrostro-Gonzalez et al, 2002;Jacobs and Filby, 1983;Kaminski et al, 2000;Ovalles et al, 2012;Petrova et al, 2013;Tojima et al, 1998;Trejo et al, 2004;Yang and Eser, 1999). However effort to compare the subfractions in terms of their structural differences and use this approach to further probe the fractionation/precipitation mechanisms are scarce.…”

“…As a complex mixture, the polydispersity of asphaltenes has greatly hampered the progress of its characterisation studies. A great deal of work has been conducted on fractionation of asphaltenes in the past (Andersen et al, 1997;Andreatta et al, 2005;Buch et al, 2003;Buenrostro-Gonzalez et al, 2002;Dickie and Yen, 1967;Groenzin et al, 2003;Jacobs and Filby, 1983;Kaminski et al, 2000;Nalwaya et al, 1999;Ovalles et al, 2012;Petrova et al, 2013;Tojima et al, 1998;Trejo et al, 2004;Wiehe and Liang, 1996;Yang and Eser, 1999). In the literature, binary solvent systems are commonly used to fractionate asphaltenes.…”