Influence of Acid/Base Treatment on Bitumen Viscosity Open Access
- Other title
- Type of item
- Degree grantor
University of Alberta
- Author or creator
González Nieves, Vanessa
- Supervisor and department
De Klerk, Arno (Chemical and Materials Engineering)
- Examining committee member and department
Elias, Anastasia (Chemical and Materials Engineering)
Nikrityuk, Petr (Chemical and Materials Engineering)
Luo, Jingli (Chemical and Materials Engineering)
Department of Chemical and Materials Engineering
- Date accepted
- Graduation date
Master of Science
- Degree level
Canadian oil sands derived bitumen is a form of petroleum that has a high density and viscosity. One of the potential causes of the high viscosity of the oil sands bitumen is acid-base interactions. The main purpose of this project was to determine the influence of acid treatment and base treatment as potential low temperature upgrading strategies on physical properties, chemical composition and morphology of bitumen.
The working hypothesis was that bitumen viscosity could be decreased by disrupting acid-base interactions. The study was performed by treating Cold Lake bitumen with aqueous solutions of hydrochloric acid (in the range 0.0003-0.3 M), lithium hydroxide (0.003 N) and ethanolamine (0.003 N). Time and temperature were controlled parameters and were kept constant. In most experiments three product phases were observed and separated: an organic phase, an emulsion phase and an aqueous phase. The analyses of treated bitumen included measurements of viscosity, density and refractive index; determination of asphaltenes content, mass balance, Fourier Transform Infrared (FT-IR) spectroscopic analysis, 1H Nuclear Magnetic Resonance (NMR) analysis and Atomic Force Microscopy analysis (AFM). The aqueous solutions were analyzed by Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) and pH analysis. Selected analyses were also performed on the emulsion phase.
Five variables in the experimental protocol were identified that had an influence on the viscosity of the treated bitumen: heating, oxidation, concentration, residual solvent (methylene chloride) and the presence of an emulsion. As part of the investigation the sample workup protocol for bitumen was revised to address the influence of these variables.
The results showed that the acid treatment and base treatment may disrupt some chemical interactions in the bitumen that also may affect physical properties such as the viscosity and density. The blank experiments (water treatment) indicated acid-base interactions may be relevant even at neutral pH. The viscosity (measured at 40 °C and corrected for residual solvent) of raw bitumen, LiOH treated bitumen and ethanolamine treated bitumen were 97.5, 15.0, and 26.4 Pa.s respectively. The extent of viscosity reduction was influenced in a similar way when a strong base (LiOH) was used compared to a strong acid (HCl), but base treatment was more prone to emulsion formation. The change of bitumen morphology after acid treatment without heating showed the disaggregation of clustered asphalthenes and other aggregating species, which correlated with the viscosity reduction. This investigation also suggested that bitumen viscosity was influenced more by acid-base interactions than hydrogen bonding.
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