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Thin-Film Pyrolysis of Asphaltenes and Catalytic Gasification of Bitumen Coke
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- Author / Creator
- Karimi, Arash
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Thin film pyrolysis was used to thermally crack the pendant groups from asphaltene molecules. The cracked products were rapidly quenched to minimize further decomposition. The liquid products were condensed and collected, with over 91% material balance on the recovery of gas, liquid and coke product. Simulated distillation of the condensed liquid products showed a wide range of compounds with boiling points up to more than 700°C produced in various stages of the reaction. The liquid components boiling below 538°C comprised 15-20% of the initial asphaltenes, and contained a wide range of chemical structures including paraffins, olefins, naphthenes, aromatics, thiophenes and sulfides, and nitrogen-containing compounds, by mass spectrometry. The ring groups were substituted with a range of alkyl side chains. Asphaltenes from a range of different crude oils gave similar results. The recovery of the pendant groups was limited by the reaction conditions, because re-reaction of the heavy products generated more light fragments. The diverse pendant groups, with paraffins accounting for a small fraction of the total mass, are consistent with a high concentration of complex bridged structures in the asphaltene fraction.
The compounds K2CO3, KCl, Na2CO3, CaCO3, CaO, and MgO were tested as catalysts for steam gasification of coke from oil sands bitumen at atmospheric pressure and 600-800°C. K2CO3 and Na2CO3 were most effective, consistent with their high mobility within the coke phase. K2CO3 and Na2CO3 reduced the activation energy of the reaction to 1.2×10^5 J/mol and 1.3×10^5 J/mol, respectively, down from 2.1×10^5 J/mol for the uncatalyzed reaction. The reaction rates varied with the partial pressure of steam between 60 kPa and 85 kPa consistent with a Langmuir-Hinshelwood model. The initial rate of gasification increased with increasing the catalyst loading up to 2.4 (mol potassium) / kg. A portion of the catalyst penetrated into the coke, where it could not promote the reaction with steam. A successful prediction of the rates at higher conversions from the initial rate data with a shrinking core model ruled out the possibility of a shift in the reaction mechanism. -
- Graduation date
- Spring 2011
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- Type of Item
- Thesis
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- Degree
- Doctor of Philosophy
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- License
- This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.