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Journal of Chemistry
Volume 2015, Article ID 580950, 8 pages
http://dx.doi.org/10.1155/2015/580950
Research Article

Structural Characterisation of Asphaltenes during Residue Hydrotreatment with Light Cycle Oil as an Additive

College of Chemical Engineering, Huaqiao University, Jimei 668, Xiamen, Fujian 361021, China

Received 23 January 2015; Accepted 5 March 2015

Academic Editor: Tomokazu Yoshimura

Copyright © 2015 Yong-Jun Liu and Zhi-Feng Li. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Several atmospheric residues (AR) of Kuwaiti crude, in the absence, or in the presence, of light cycle oil (LCO) as an aromatic additive, were hydrotreated in an experimental plant. Asphaltenes (precipitated from Kuwaiti AR, a hydrotreated AR, and a hydrotreated blend of AR and LCO) were characterised by chemical structure and changes during residue hydrotreatment. The average structural parameters of these asphaltenes, obtained from a combined method of element analysis, average molecular weight, X-ray diffraction, and NMR, demonstrate that, after hydrotreatment, the aromatic cores of the asphaltenes become more compact and smaller whereas the peripheral alkyl branches are decreased in number and shortened. The influence of LCO on residue hydrotreating is also studied in terms of structural changes in the asphaltenes. The findings imply that LCO added to AR during hydrotreating improves the degree of aromatic substitution, the total hydrogen/carbon atomic ratio per average molecule, the distance between aromatic sheets and aliphatic chains, and so forth, by modifying the colloidal nature and microstructure of asphaltene: this is beneficial for the further hydroprocessing of AR. Three hypothetical average molecules are proposed to represent the changes undergone by such asphaltenes during hydrotreatment as well as the effects of additive LCO.