X-ray Photoelectron Spectroscopy Analysis of Hydrotreated Athabasca Asphaltenes

Abstract

C7 asphaltenes from Athabasca crude oil were hydrotreated using a commercial NiW/Al2O3 catalyst and analyzed using X-ray photoelectron spectroscopy. Results showed that the catalyst performed better in the removal of sulfur rather than nitrogen and that sulfur concentration is higher at the surface in comparison to the bulk structure. Moreover, the sample after reaction had a higher oxygen content in comparison to the untreated asphaltene, indicating poor hydrodeoxygenation performance of the catalyst in addition to a higher reactivity toward atmospheric oxygen at the surface of the asphaltene. The latter is proposed to arise once the layer of resin covering the asphaltene is partially converted during the hydrotreating process.

Asphaltenes: Separations, structural analysis and applications

“…Major nitrogen is aromatic in formation of pyrrole, pyridine and their derivatives. Content of pyrrolic nitrogen is usually more than that of pyridic nitrogen, and the saturated amine is negligible in asphaltenes [29] . As for sulfur in asphaltenes, thiophene (aromatic) is the most common form, followed by sulfide (saturated) structure; the oxidized sulfur is mostly sulfoxide.…”

“…The original acid and alkali of asphaltene is oxygen/sulfur and nitrogen functional groups, the typical acidic functional groups are phenols, carboxylic acids and naphthenic acids [56] , and basic sites usually contain heteroatoms (N, O, S) in/near aromatic ring or on alkyl chain [57] . The amount and kinds of hydroxyl and carboxyl groups of Athabasca petroleum asphaltene were calculated by high resolution 13 C, 19 F, and 29 Si NMR spectra [58] . There were 4 to 8 hydroxyl groups (including COOH) per molecule on average ( Fig.…”

“…XPS is committed to analysis the chemical states of carbon, oxygen, sulfur and nitrogen in asphaltenes [175] . Table 7 lists the binding energy for C 1 s , N 1 s , O 1 s , S 2 p 3/2 and their different chemical forms, respectively [29,175] .…”

“…With regard to oxygen, oxygen in coal-derived asphaltene was mainly in the form of C-O (C-OH and C-O-C), few in the C = O and COO-compounds. While asphaltenes from residue oils was more likely in the form of C = O and COO-groups [29] . Pyrrolic-nitrogen and pyridinic-nitrogen were the two main kinds also both in coalhttp://engine.scichina.com/doi/10.1016/j.jechem.2018.10.004 derived asphaltene and petroleum asphaltene.…”

“…XRD and NMR founded that, with the temperature increase, L α , d m , total http://engine.scichina.com/doi/10.1016/j.jechem.2018.10.004 carbon number and average alkyl chain length decreased, while f α and aromatic carbon number increased [190] . The heteroatom removal usually contains hydrodesulfurization (HDS) [29,191,192] , hydrodenitrogenation (HDN) [12,191,193] , and hydrodemetallization (HDM) [24,192] , which is not as easy as desirable since the nucleus system remained with and/or without heteroatoms. Singlelump model was more adequate than Langmuir-Hinshelwood (L-H) models for specific asphaltenes [193] .…”