Visbreaking of Oilsands Bitumen between 150 and 300 oC

• Author / Creator

  Yanez Jaramillo, Lina Maria

• Visbreaking is described as a mild thermal cracking, low conversion process, which industrially operates in the temperature range of 430 to 490 °C. Conversion is limited by the onset of coke formation. The main objective of visbreaking in conventional oil refineries is to reduce the viscosity of the fuel oil without causing oil instability. When visbreaking is applied to the upgrading of Canadian oil sands bitumen, the objective is to reduce the bitumen viscosity to facilitate pipeline transport. It was reported that bitumen viscosity could be decreased by two orders of magnitude by visbreaking in the temperature range 340 to 400 °C. These observations suggested that it might be possible to decrease bitumen viscosity without much cracking conversion, which provided justification for exploring even milder visbreaking conditions. The objective of this study was to determine and understand the changes in the properties of oil sands bitumen over time when the bitumen was exposed to temperatures in the range 150 to 300 °C for 1 to 8 hours. The study employed Cold Lake bitumen and it was found that the change in viscosity with time was not monotonous and was influenced by both temperature and reaction time. It was possible to reduce bitumen viscosity by two orders of magnitude over the temperature range 250 to 300 °C. A discontinuity in the viscosity behaviour was observed between 200 and 250 °C. At 200 °C and lower temperatures there was no improvement in viscosity. It was postulated that free radical addition reactions were responsible for the observed increase in viscosity. It is also worthwhile pointing out that hydrogen disproportionation was evident even at 150 °C.

• Subjects / Keywords

  • Visbreaking, viscosity, oil sands bitumen

• Graduation date

  Spring 2016

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3697083H

• 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.