Organically-Modified Clay Minerals in Oil Sands: Characterization and Effect of Hydrothermal Treatment

• Author / Creator

  Chen, Qiang

• The intimate association between bitumen components and clay minerals is an important feature of oil sands fine solids. These organically-modified clay minerals cause serious problems in Canadian oil sands production: hindering bitumen extraction, stabilizing water-in-bitumen emulsions, fouling upgrading equipment, and contributing to the formation of indefinitely-stable mature fine tailings suspensions. In the present work, the irreversible adsorption of asphaltenes from toluene solutions onto kaolinite was studied as a model system for the unextractable adsorption of bitumen components on clay mineral. Native clay minerals obtained from Athabasca bitumen froth, with and without a hydrothermal treatment (at 300–420°C), were examined by several techniques including quantitative nanomechanical mapping atomic force microscopy (QNM-AFM) and X-ray photoelectron spectroscopy (XPS). The effect of the hydrothermal treatment on the organically-modified clay minerals and the consequent changes in their emulsification and filtration behaviors were investigated. The adsorption of asphaltenes on kaolinite was confirmed to be a largely irreversible process, based on the observation that circa 80% of asphaltenes remained adsorbed on kaolinite even after thorough toluene washing. The irreversibility of asphaltene adsorption is consistent with the presence of unextractable organic matter by toluene in oil sands fine solids reported in the literature. Thermal dehydroxylation enhanced the adsorption capacity of kaolinite for asphaltenes. The XPS-determined percent surface coverage was 18% and 41% on the untreated and dehydroxylated kaolinite, respectively, corresponding to a maximum adsorption density of 3 and 7 mg/m2. The incomplete surface coverage even at the highest adsorption density indicated the patchy characteristics of adsorbed asphaltenes on both kaolinite substrates. Analogously, patches of organic matter were also observed on the native clay minerals in oil sands, as indicated by the inhomogeneous spatial distribution of adhesion force on the surfaces of platy particles (determined by QNM-AFM). The surface coverage and mean domain thickness of the organic coating on the clay basal faces were estimated to be 17±6% and 1.4 nm, respectively. In addition to this patchy organic coating, there were organic materials trapped in the oil-mineral aggregates. These trapped organics were found to be softer (more deformable) than the asphaltene fraction of oil sands bitumen. Hydrothermal treatment at 390°C increased the surface carbon concentration of the fine solids in bitumen froth from 36 to 47 atom% (determined by XPS), but reduced their total organic carbon content from 15 to 10 wt% (determined by bulk elemental analysis). The hydrothermally-treated fine solids became more uniformly hydrophobic and more active in stabilizing emulsions. The volume of the produced emulsions was found to increase linearly and monotonically with the proportion of a specific sub-fraction of the fine solid particles with a critical surface tension of 27–30 mN/m (determined by the film flotation method), likely because of their intermediate hydrophobicity and thus relatively stronger emulsifying capacity. The filterability of the bitumen froth fine solids was enhanced after the hydrothermal treatment, as shown by both room-temperature filtration and in-situ hot filtration (at ~200°C) tests. Based on this observation, a conceptual bitumen froth cleaning approach is proposed, which combines the hydrothermal treatment of bitumen froth, water separation by venting, and solids removal by in-situ hot filtration. The small-scale laboratory tests using 500-mL Parr reactors and 0.5-μm pore size stainless steel filters showed that this procedure was able to reduce the fine solids content from 8 wt% in the original bitumen froth to 0.08 wt% in the bitumen product.

• Subjects / Keywords

  • Bitumen froth
  • Hydrothermal treatment
  • Filtration
  • Emulsions
  • Clay minerals

• Graduation date

  Fall 2017

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R32R3PB0Z

• 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.