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Thermal Cracking Reactions of Model Compounds of Asphaltenes Open Access


Other title
thermal cracking
chemical structure
model compounds
Type of item
Degree grantor
University of Alberta
Author or creator
Alshareef, Ali Haider
Supervisor and department
Gray, Murray R. (Chemical and Materials Engineering)
Examining committee member and department
Elliott, Janet A.W. (Chemical and Materials Engineering)
Savage, Philip E. (Chemical Engineering, University of Michigan)
Gray, Murray R. (Chemical and Materials Engineering)
Stryker, Jeffrey M. (Chemistry)
Semagina, Natalia (Chemical and Materials Engineering)
Department of Chemical and Materials Engineering

Date accepted
Graduation date
Doctor of Philosophy
Degree level
Resolution of reaction pathways to coke formation during the upgrading of heavy resources, such as the vacuum residue fraction of bitumen, is hampered by the extreme complexity of these materials. Alternatively, probing the molecular–level reactions and cracking kinetics of model compounds that incorporate structures known to be present in the asphaltenes was shown to provide more quantitative information. The objective of this research is to investigate the thermal cracking and coking reactions in the condensed liquid phase of especially synthesized model compounds of asphaltenes. The model compounds used in this study are of three distinct chemical structures: archipelago structures made of three aromatic systems linked by two ethano bridges, alkylpyrene compounds with different side–chain lengths, and cholestane–benzoquinoline compounds substituted with different aromatic groups. All of the compounds have high molecular weights, within a range of 530–770 g/mol, to ensure they remain in the liquid phase at the reaction conditions. The pure compounds and binary mixtures of them were thermally cracked using thermogravimetric analysis to obtain cracking kinetics and coke yields. Microreactor experiments on selective samples provided the conversion of parents, and nature and selectivity of products. Analysis using a number of chromatographic and spectroscopic techniques showed that initial fragments from the model compounds add to other fragments and to the parent via alkyl–alkyl and alkyl–aryl addition reactions to build larger archipelago structures. In addition to the labile bonds that were expected to crack, strong bonds such as alkyl–pyrene bonds also cracked, likely facilitated by unimolecular rearrangement processes. The archipelago compounds formed much more addition products, and subsequently more coke, than the other two families of compounds or their phenyl analogs. Within each family, minor structural changes were found to greatly influence the coke yield, with the reactivity of the parent and its initially formed products, as well as the intermolecular associations, as observed with polarized light microscopy, as the main controlling factors. The activation energy of the cracking reactions, on the other hand, fell within a narrow range for each family of compounds suggesting that similar bonds dominate cracking.
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
Citation for previous publication
Alshareef, A. H.; Azyat, K.;Tykwinski, R. R.; and Gray, M. R.
, A. H.; Scherer, A.; Tan, X.; Azyat, K.; Stryker, J. M.; Tykwinski, R. R.; and Gray, M. R.

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