No abstract

Artificial mixtures of bitumen with three natural clay standards, dominated by illite, kaolinite, and chlorite, were reacted for several days and washed three times each with cyclohexane to remove bitumen from the clays. The main goal was to determine and better understand the effect of nonswelling clay minerals (illite, kaolinite, and chlorite) on nonaqueous solvent bitumen extraction. The experimental results showed that the total amount of residual cyclohexane insoluble organic carbon (CIOC) measured for clay−bitumen mixtures after nonaqueous solvent bitumen removal is a function of intrinsic resistance of high molecular weight (MW) organic compounds to cyclohexane extraction and the nature of nonswelling clays. The intrinsic resistance of high MW organic compounds to cyclohexane extraction accounted for 42−80% of the total CIOC content. The nonswelling clays retained from 20 to 58% of CIOC of the total CIOC content primarily on the external surfaces (basal planes and edges) of clay mineral particles in the form of patches rather than continuous coatings. Cation exchange capacity (CEC) and specific surface area (SSA) were reduced by the reaction with bitumen due to organic coatings on the clay mineral surfaces and/ or due to bridging of clay particles to aggregates. The results indicate that the SSA is the primary controlling parameter affecting the amount of CIOC retained on the nonswelling clays within the studied experimental conditions. Higher amounts of CIOC resist on clays which have larger SSAs. CEC and layer charge density (LCD) are contributing parameters possibly affecting the extractability of bitumen from studied clays. It seems that, with increasing CEC and LCD, the CIOC was bonded more strongly to the clay mineral surface; consequently, more CIOC resisted nonaqueous solvent bitumen removal. ■ INTRODUCTIONThe Alberta oil sands deposits represent the third largest resource of bitumen on the planet after Venezuela and Saudi Arabia. 1 Commercial recovery of bitumen from the Alberta oil sands is achieved by water-based extraction processes. Alternative nonaqueous solvent extraction processes have been investigated since the mid-1960s due to their potential advantages such as high bitumen recovery, elimination of sludge tailings ponds, and decrease in water consumption. 2 The Alberta oil sands are a mixture of coarse sand, fine clays, bitumen, and water. Quartz is the principal mineral of Alberta oil sands along with a small amount of clay minerals, carbonates, feldspars, and traces of TiO 2 minerals and pyrite. 3 Kaolinite, illite, chlorite, and interstratified illite−smectite have been reported as the main clay minerals of Alberta oil sands. 3 Variability in ore composition is known to affect bitumen recovery from the oil sands. It has been recognized that the presence of clay minerals may have negative consequences on bitumen extraction. 4,5 However, different types of clay minerals may have differing effects on the processability of oil sands ore during the extraction process, likely due to their d...

Two natural clay standards, dominated by montmorillonite (SWy-2) and Illite-smectite (ISCz-1), were mixed with bitumen and reacted for 8 days. The clay-bitumen mixtures were then washed three times each with cyclohexane to extract bitumen from the clays. The aim was to better understand the role of swelling clay minerals on nonaqueous solvent bitumen extraction. The experimental results showed that montmorillonite and Illite-smectite contained 4.6 to 8.2 wt % and 7.1 to 8.2 wt % of carbon after cyclohexane bitumen extraction, respectively. The residual organic material after cyclohexane bitumen extraction was retained on the outer and inner (interlayer space) surfaces of the swelling clay mineral particles in the form of patchy rather than continuous coating. Cation exchange capacity (CEC), specific surface area (SSA), and layer charge density (LCD) were all reduced by the reaction with bitumen due to organic coatings on the clay mineral surfaces and/or due to gluing of clay particles to aggregates. Comparison of the present study with our recent paper revealed that swelling and nonswelling clay minerals reacted differently with bitumen. These differences are reported and discussed in the present study. Overall, the results indicate that clays with larger SSAs retain more residual organic matter after nonaqueous solvent bitumen extraction within the studied experimental conditions. In the case of montmorillonite SWy-2, the amount of carbon after nonaqueous solvent bitumen extraction was heavily affected by different relative humidity (RH) conditions. The pretreatment of SWy-2 at higher RH conditions dramatically increased the amount of residual organic matter. This is likely related to the opening of the interlayer space (i.e., swelling) of montmorillonite upon exposure to higher RH and subsequent retention of a larger amount of organic material.