Study of Desorption of Asphaltene from Solid Surface by Use of Solvents and Chemicals
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A study of adsorption and desorption of asphaltene on a stainless steel surface was preformed. A quartz crystal microbalance (QCM) was used for the the study. Different solvents were tested for their ability to desorb asphaltenes. Of the solvents tested (THF, chloroform, pyridine, aniline, CS2, and quinoline), it was found that pyridine gave the highest desorption, with an average desorption of 69.3% (by weight). Of the tested solvents, CS2 was the least effective solvent, with an average desorption of 18.2%. The Hansen solubility parameter (HSP) consist of three partial solubility parameters, δD, δP, and δH. These parameters can be used to predict a solvents ability to dissolve a substance with known HSP . More similar HSP gives a lower solubility distance , Ra, between the solvent and substance, and better solubility properties. Based on this correlation, a model suggesting a linear relationship between Ra and a solvents ability to dissolve asphaltenes was proposed. It was found that higher Ra resulted in a lower desorption. A linear relationship was found when estimating the HSP for asphaltenes to of δD = 18.6 MPa1/2, δP = 6.6 MPa1/2, and δH = 3.9 MPa1/2. Whole asphaltenes was fractionated based on adsorption to CaCO3 , and the fraction that was irreversible adsorbed, fraction IAA, was found to have a higher ability to adsorb to stainless steel than whole asphaltenes. Desorption by pyridine and chloroform was also lower than for whole asphaltenes, with 9.6% and 13.5% less desorbed asphaltenes, respectively. The IAA also showed indications of adsorbing as multilayers as the change in dissipation was more than 1x10^-6. Whole asphaltenes adsorbed as rigid monolayers.