Binary Solvents with Ethanol for Effective Bitumen Displacement at Solvent/Mineral Interfaces

Abstract

Displacements of bitumen from silica surfaces were studied using various solvents and binary mixtures of ethanol. It was found that single-component solvents, including water, toluene, cyclohexane, and ethanol, were not able to completely remove bitumen on silica. However, adding 5% ethanol to toluene greatly enhanced its ability to displace bitumen from the silica surface. Surface vibrational spectra obtained by sum frequency generation vibrational spectroscopy showed that no trace of bitumen could be detected on silica after treatment with the 5% ethanol−toluene mixture. Similar effects were observed for cyclohexane with 10% ethanol. The results suggested that binary solutions with amphiphilic components, such as ethanol, are effective solvents for release of bitumen from the mineral surface. This expectation was confirmed by batch extraction experiments on Athabasca oil sands samples using cyclohexane−ethanol solutions. ■ INTRODUCTIONSurface chemistry of bitumen has been gaining a great deal of interest because there are large deposits in oil sands available for further development to supply the future energy needs. Natural bitumen is the remnants of degraded conventional oils and usually mixed with large proportions of sand. In the oil sands, each grain of sand is surrounded by a slick of bitumen, and the bitumen content may vary from 1 to 18 wt %. 1 In the Athabasca deposits, more than 90% of the bitumen can be recovered using hot-water extraction techniques, in which water at 40−50°C is added to the crushed oil sands, allowing the bitumen to reduce its viscosity and separate from the sand. 2 However, the water-based extraction process is energy-intensive because of the large volumes of water, generating greenhouse gas emissions. Additionally, the accumulation of wet tailings creates a serious problem of mine reclamation and eventual treatment of the water. A number of oil sands deposits occur in areas with limited water and with physical properties unsuited to the aqueous process, including Utah and Kazakhstan. 3 These issues associated with water-based extraction processes may potentially be resolved using a non-aqueous extraction process, which uses solvents to separate bitumen and eliminate or reduce water intake in the extraction process. Because bitumen dissolves in the solvent, non-aqueous extraction can be carried out at ambient temperature and significantly lowers the energy demand. 4 Currently, very little is known about the bitumen/ mineral and solvent/mineral interfaces, and an effective solvent for bitumen separation remains unidentified.Bitumen is a complex mixture of hundreds of different types of organic molecules, and its complexity has thus far defied complete analysis of molecular structure and composition. 5,6 Studies have suggested that bitumen is composed primarily of polyaromatic hydrocarbons with heteroatoms, such as oxygen, nitrogen, and sulfur. The average molecular weight has been reported to be about 540−800 g/mol. 1 Generally, the components of bitumen are classified into two gro...

Effective Interactions and Adsorption of Heterocyclic Aromatic Hydrocarbons in Kaolinite Organic Solutions Studied by 3D-RISM-KH Molecular Theory of Solvation

“…Selection of an optimal solvent for nonaqueous extraction is a challenging problem, as the hypothetical ideal solvent should be affordable, nontoxic (green), and easily recoverable, and should provide good bitumen desorption. To date, a number of different solvents and solvent mixtures have been tested for bitumen extraction. − Nikakhtari et al screened 13 different solvents and mixtures for bitumen desorption, solvent recovery, and residual fines in extracted bitumen, and found that cyclohexane and isoprene are the most promising among the studied solvents for commercial utilization. Both cyclohexane and toluene showed excellent bitumen recovery (94.4 and 96.3%) .…”

Surface Charge at the Bitumen/Water Interface Investigated by Phase-Sensitive Sum Frequency Generation Vibrational Spectroscopy: Effects of pH, Ions, and Surfactants

“…We overcame this difficulty by placing a bitumen film on the water surface, which caused minimal IR absorption and allowed the IR laser to access the buried interface. Previous SFG studies on bitumen showed that the vibrational peaks in the CH region consist of three peaks at 2850, 2870, and 2935 cm –1 , corresponding to the CH 2 symmetric stretch, CH 3 symmetrical stretch, and CH 3 Fermi resonance, respectively . However, the CH peaks did not provide much information on the bitumen surface.…”

“…Previous SFG studies on bitumen showed that the vibrational peaks in the CH region consist of three peaks at 2850, 2870, and 2935 cm −1 , corresponding to the CH 2 symmetric stretch, CH 3 symmetrical stretch, and CH 3 Fermi resonance, respectively. 15 However, the CH peaks did not provide much information on the bitumen surface. We found that vibrational peaks of water in the OH region are highly sensitive to the pH, ion, and surfactant concentrations, which provided a better understanding of the interaction between water and bitumen.…”

Plasma Treatment Effects on Molecular Structures at Dense and Porous Low-k SiCOH Film Surfaces and Buried Interfaces

“…The reflected SFG beam was guided through a monochromator, and a photomultiplier tube (Hamamatsu) was used to measure the intensity of the SFG beam while the infrared beam was scanned in the 2800–3100 cm –1 range. Descriptions of SFG theory and applications can be found elsewhere. − …”