Colloidal Interactions of Asphaltene With Inorganic Surfaces
14th March 2018, Wednesday, 04:00‐04:30 pm (25+5 mins), ChE Seminar hall
To investigate the asphaltene and inorganic substrate interactions, deposition and removal of asphaltene was studied on the basis of morphology change as obtained employing AFM. The glass slides (proxy material for silica) were cleaned through standard procedures, where roughness was observed to be ~ 0.3 nm. The clean glass slides were aged in pure solvent(s), and later with asphaltene and solvent(s) to observe interaction with the substrate. The solvents used were heptane, toluene, and a mixture of these two (also known as heptol), where heptane to toluene ratio was also altered. The aging was conducted over a specified time under pre-defined temperatures. The slides were dried in an oven and were characterised immediately using AFM. In the absence of asphaltene, the roughness of glass slides aged in heptane and toluene respectively was found to be ~ 0.8 nm. These values didn’t change significantly till a temperature of 70°C which defines no or scarce adsorption of solvents on clean glass slides. It was also observed that roughness was enhanced to ~ 121 nm in case of heptane and asphaltene mixture at concentration of 87.5 mg/l of asphaltene, determining a greater extent of deposition. This Untreated (asphaltene aged) glass slides when rinsed with heptane had a roughness reduction to ~ 45 nm. The concentrations were reduced to 15 mg/l where roughness of untreated and heptane rinsed aged substrate was ~ 80 nm and ~ 47 nm respectively.
Asphaltene removal studies too were carried out where both bulk and convective mass transfer were compared simultaneously. A parallel plate channel was fabricated to carry out removal of asphaltene by the impact of shear forces on glass slides. The roughness was found to have reduced as shear rates were increased from 6.94 x 10-2 Pa to 208.33 x 10-2 Pa attaining a value of ~ 6 - 8 nm at shear rates of 62.5 x 10-2 Pa and above, thereby defining removal of asphaltene from the surface. The alteration in wettability by deposition/removal of asphaltene was analyzed through contact angle measurements which showed substrates tending be hydrophobic under the presence of asphaltene on the surface.