000			02437nab a2200181 4500
005			20260520000831.0
008			260224s2009 xxu
245	0	0	_aAdsorption of crude oil on surfaces using quartz crystal microbalance with dissipation (QCM-D) under flow conditions
260			_a _b _cmar./abr. 2009
270			_a2009-08-07 ; 2009-08-07
300			_a12 p. ; 1237-1248
520			_aResúmen del autor: Adsorption of crude oil on surfaces is successfully measured with a quartz crystal microbalance with dissipation (QCM-D) under flow conditions. The amounts and thicknesses of adsorbed films are determined with good accuracy using liquid loading corrections. Measurements are performed in solvents where the degree of asphaltene stability is high (toluene) and poor (n-alkanes and heptane/toluene mixtures). In toluene, Langmuir-type adsorption is recorded with saturation film thicknesses of 3-4 nm and limited desorption after rinsing. The size of adsorbing species is also determined at early times where adsorption is diffusion-controlled up to 3 wt % crude oil (or 835 ppm asphaltenes) in toluene. The primary asphaltene species that adsorb on the crystal surface are molecules with a diameter of 0.5-1.6 nm at 139-278 ppm asphaltenes and nanoaggregates with a diameter of 2.6-5.6 nm at 835 ppm asphaltenes in toluene. In n-alkanes (nC7, nC10, and nC12), saturation plateaus are not observed within the experimental time scale. Film thicknesses recorded after 3.5 h are all higher than those in toluene and increase with increasing n-alkane carbon number, mainly because of increasing polarity of aggregates. Atomic force microscopy (AFM) analyses reveal that the size of adsorbed aggregates decreases with n-alkane carbon number. Aging effects show that, with time, the adsorbed films become more rigid in toluene and more viscoelastic in n-alkanes. In heptane/toluene mixtures, a significant increase in the dissipation factor is observed close to the flocculation threshold. Adsorption on various surfaces from toluene shows a high affinity of asphaltenes to hydrophilic surfaces. On the other hand, asphaltenes are almost amorphous in n-alkanes. X-ray photoelectron spectroscopy (XPS) analyses of the adsorbed films confirm these observations
773	0		_tEnergy & fuels _g23
942			_cARTICULO
100	1		_aAbudu, Adewunmi _941734
100	1		_aGoual, Lamia _941735
999			_c170262 _d170262