Structure Representation of Asphaltene GPC Fractions Derived from Kuwaiti Residual Oils

Abstract

Two asphaltenes obtained from a residual oil before and after hydrotreatment were subjected to preparative GPC. Selected GPC fractions were analyzed by NMR and XRD to derive structural parameters to investigate whether there is a relationship between the molecular size of the asphaltene fraction and its structural features. Under the GPC experimental conditions (∼5 wt % THF solution), some eluting species are aggregates rather than monomeric molecules. Nevertheless, a correlation between the molecular size of the GPC fraction and its structure was found. The higher the molecular weight (MW), the more aromatic and condensed is the fraction. Moreover, the asphaltene fractions with the highest MW of both residues, before and after hydrotreating, show very similar structural features. This fact suggests that during hydrotreatment the low MW asphaltenes are converted to distillates, whereas the higher MW fractions (>6000 Da) stay unaltered and can cause severe coking in the downstream processes because of the highly refractory asphaltenes, which are still present. Structure presentations derived from NMR and XRD data demonstrate that the higher MW fractions (≈5250 Da) of both residues consist of clusters of 4-5 aromatic rings, which are interlinked by aliphatic chains of 9-11 carbon atoms.

Application of microbial enhanced oil recovery technology in water‐based bitumen extraction from weathered oil sands

“…As the heaviest and least reactive compounds, asphaltenes exhibit complex bridged structures of naphthenic and aromatics comprising heteroatoms of sulfur and nitrogen. [61][62][63][64] The strain of P. aeruginosa has been reported to degrade nalkanes and polycyclic aromatic hydrocarbons (PAHs). [65][66][67][68] It was proposed that the n-alkanes was degraded via a terminal oxidation pathway, while the degradation of PAHs with three or four aromatic rings was through monooxygenation or dioxygenation of the carbon at certain position of the PAHs molecules.…”

A Review of Kinetic Modeling Methodologies for Complex Processes

“…Over time, these methods have been improved by adding additional analytical techniques, such as 13 C NMR (Ali et al, 1990(Ali et al, , 2006Altgelt and Boduszynski, 1994;Cantor, 1978;Dickinson, 1980;Knight, 1967;Petrakis and Allen, 1987;Sato, 1997;Sato et al, 1998;Suzuki et al, 1982;Takegami et al, 1980), Size Exclusion Chromatography (SEC) (Al-Zaid et al, 1998;Gauthier et al, 2008), infrared spectroscopy (Montgomery and Boyd, 1959;Qian et al, 1984), functional groups analysis (Faulon, 1994) or pyrolysis analysis (Artok et al, 1999;Faulon et al, 1990;Kowalewski et al, 1996), which allows for more molecular input for the mixture and reduces the number of assumptions.…”

Molecular reconstruction of heavy petroleum residue fractions

“…Many authors have chosen to represent petroleum fractions (and especially asphaltenes) by an average model molecule in 2D (Hirsch and Altgelt, 1970;Speight, 1999;Takegami et al, 1980;Suzuki et al, 1982;Ali et al, 1990Ali et al, , 2006Sato, 1997;Artok et al, 1999;Gauthier et al, 2008) or 3D (Faulon et al, 1990). These average model molecules are generally constructed to be consistent with the information on the various chemical functions in the mixture, provided via e.g.…”

“…Further details on the SR method can be found elsewhere (Hudebine et al, 2002;Hudebine, 2003;Hudebine and Verstraete, 2004 To apply the SR step to residue fractions, a set of distributions of structural attributes needs to be chosen and a reconstruction scheme, which describes the sampling order of the different distributions, needs to be specified. The choice of the structural attributes and their distributions has been guided by knowledge of the chemical nature of these heavy products (Takegami et al, 1980;Suzuki et al, 1982;Murgich et al, 1987;Ali et al, 1990Ali et al, , 2006Trauth, 1993;Altgelt and Boduszynski, 1994;Miyabayashi et al, 1995;Artok et al, 1999;Mullins and Sheu, 1999;Speight, 1999;Groenzin and Mullins, 2000), but care has been taken to minimize the number of attributes.…”