Adsorption Of Aromatics From Base Oil Over Polymeric Resins: Equilibrium And Kinetics

Adsorption of aromatic molecules from base oil over an acid resin (Amberlyst 15W) was studied, with a focus on reducing the aromatic content to that of a white mineral oil. It was found that the adsorption capacity of the resin was low, At saturation in the best condition, the adsorption capacity corresponded to 10% acid capacity. The effects of dilution, temperature, and adsorption time were studied. In the absence of,a diluting solvent, the isotherm was unfavorable and the adsorption rate was low, with a pseudo-first-order constant of about 0.1 h(-1). Dilution of the oil with n-hexane had beneficial effects on the adsorption capacity, the adsorption rate, and the yield of refined oil. The 1:1 (vol/vol) dilution was found to be optimal. Kinetic data were better explained by a model of dominant intrapartide diffusion, with the adsorbate load being proportional to the square of the adsorption time. Dilution with n-hexane was thought to decrease the viscosity with a proportional increase of the diffusivity and a decrease of the chemical affinity of the oil matrix. Estimations of the oil purity and refined oil yield after a series of equilibrium stages indicated that three stages with an adsorbent/oil ratio of 0.5 (g g(-1)) and a 1:1 dilution in n-hexane could refine the studied base oil (initial aromatic content of 0.136 mmol g(-1)) to a white mineral oil of food grade, with a yield of about 60%. Removal of the solvent was considered easy given the high volatility of n-hexane compared to that of the oil.