Search

Low-cost biosourced hybrid microporous adsorbents with improved affinity towards carbon dioxyde (CO2) were prepared through the incorporation of various amounts of glucosylated dendrimer into bentonite- and montmorillonite-rich composite materials. Characterization by nitrogen adsorption-desorption isotherms, surface specific and pore size analyses (BET and BJH), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) revealed changes in the interlayer spacing and textural structure of the materials. Thermal programmed desorption measurements (TPD) showed significant improvements of the retention capacity of CO2 (CRC) and water (WRC). This was explained in terms of enhancement of both surface basicity and hydrophilic character due to the incorporation of terminal polyhydroxyl groups. The CRC was found to vary according to the previous saturation time with CO2 and the carrier gas throughput. CO2 was totally released upon temperature not exceeding 80 °C or even at room temperature upon strong carrier gas stream, thus providing evidence that CO2 capture involves almost exclusively physical interaction with the OH groups of the dendrimer. This result opens promising prospects for the reversible capture of carbon dioxide with easy release without thermal regeneration, more particularly when extending this concept to biosourced dendrimers. [ABSTRACT FROM AUTHOR]

After oil sands separations, settling of clays from aqueous tailings can be promoted by additives such as Ca2+ salts. However, if the liberated water is then recycled, these same additives in the water interfere with bitumen recovery in the separator. Therefore, we have tested CO2-triggered switchable additives to see whether they can switch back and forth between a form that is suitable for the separation stage and a form that promotes tailings ponds settling. CO2-triggered switchable additives can reversibly change water chemistry merely by introduction and removal of CO2, a benign trigger. Here, the effects of CO2-mediated switchable additives on colloidal interactions found in model oil sands were studied by chemical force spectrometry. Self-assembled monolayers of 12-phenyldodecanethiol and 12-mercaptododecanoic acid were used to chemically modify gold-coated atomic force microscope tips. These were subsequently used to study the adhesion force between the modified tips and the minerals silica and mica. The adhesion between the tips and the mineral substrates was studied in aqueous solutions of varying pH and divalent cation concentration and in the presence of cationic switchable additives of varying surfactant potency, both in the presence and in the absence of CO2. In the presence of CO2, the best additive promotes attractive forces, while in the absence of CO2, the forces are repulsive. These results are discussed in the context of the mechanism of colloidal interactions in an oil sands system. [ABSTRACT FROM AUTHOR]

Sequestration of CO2 in hydrate form within deep oceanic sediments, to simultaneously replace methane trapped in submarine hydrate, has been considered as an efficient method for CO2 reduction. Consequently, research efforts are underway to deeply understand the properties of CH4 and CO2 hydrates. In this work, CH4 + CO2 double hydrate crystals were grown from aqueous solution in a capillary high-pressure optical cell. The quantitative relationships between Raman intensity and dissolved gas (i.e., CH4 and CO2) concentration in water and in hydrate were established. The partition coefficients of CH4 and CO2 between the hydrate and aqueous phases were measured at 5 constant temperatures from 275.15 to 293.15 K. The equilibrium concentrations of dissolved CH4 and CO2 decrease with decreasing temperatures, indicating more dissolved CH4 and CO2 will be transferred from the aqueous to the hydrate phase at lower temperature. With decreasing temperature, the molality of CO2 in hydrate increases and the molality of CH4 in 51262 cavities decreases, while the sum of the molality of CH4 in 5126² cavities and molality of CO2 in hydrate keeps constant, indicating that CO2 molecules can replace more methane molecules under lower temperature only by occupying the 5126² cavities. [ABSTRACT FROM AUTHOR]

Separation of bitumen from oil sands is far more efficient with an organic solvent than with the conventional hot water (Clark) process, but the removal of the organic solvent from the bitumen requires distillation. Distillation is problematic because of the energy cost and the need for a volatile solvent (which is therefore likely to be flammable and smog-forming). A switchable hydrophilicity solvent (SHS) is a solvent that is water-miscible in the presence of an atmosphere of CO2 but separates from water when CO2 is absent. Extraction of bitumen from low-grade high-fines oil sands using a SHS (CyNMe2) is efficient, removing 94%-97% of the bitumen. The resulting solids (sand and clay) are dry, free-flowing, and contaminated with only 0.4 wt % of bitumen and as little as 102 ppm of the solvent. No distillation step was required to recover the solvent from the bitumen. Instead, carbonated water extraction removed the solvent from the oil. Losses of the CyNMe2 solvent were, for the best method, 0.06 grams of solvent per gram of bitumen recovered. The method recovers more oil than the Clark process, produces cleaner solids, works with low-grade high-fines oil sands, and requires neither distillation nor a volatile solvent. [ABSTRACT FROM AUTHOR]