Article pubs.acs.org/EF
Influence of Nonswelling Clay Minerals (Illite, Kaolinite, and Chlorite) on Nonaqueous Solvent Extraction of Bitumen Marek Osacky,*,†,‡ Mirjavad Geramian,† Douglas G. Ivey,† Qi Liu,† and Thomas H. Etsell† †
Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta T6G 2V4, Canada Department of Geology of Mineral Deposits, Comenius University, Mlynska Dolina, Bratislava 84215, Slovakia
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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.
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INTRODUCTION The 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 TiO2 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 different structures (1:1 vs 2:1 type of layers, swelling vs nonswelling character), crystal chemistry and surface properties (cation exchange capacity, layer charge and specific surface area). Currently, it is technologically impossible to isolate individual types of clay minerals from the oil sands to investigate their structure, crystal chemistry, and surface properties in order to better understand their effect on bitumen extraction. Moreover, due to the complexity (mixture of bitumen, water, and solids) and highly heterogeneous nature of the Alberta oil sands © XXXX American Chemical Society
(mineral and chemical composition and surface properties), it is difficult to determine the effect of individual clay minerals on bitumen recovery when testing the whole ore sample. To overcome these problems, a set of experiments was performed in the present study using natural standards of clays dominated by nonswelling clay minerals (kaolinite, illite, and chlorite). These are known to be the major types of clay minerals present in the Alberta oil sands. The main goal of the present study was to determine and better understand the effect of individual nonswelling clay minerals (kaolinite, illite, and chlorite) on nonaqueous solvent bitumen extraction.
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MATERIALS AND METHODS
Materials. Three nonswelling clays, KGa-2 (kaolinite, Georgia), IMt-1 (illite, Montana), and CCa-2 (chlorite, California) obtained from the Clay Mineral Repository of the Clay Minerals Society, and bitumen isolated from Alberta oil sands were used in this study. The bitumen was extracted from a high grade, low fines, good processing oil sands ore provided by Syncrude Canada Ltd. The
