Adsorption of Aromatics from Base Oil over Polymeric Resins. Equilibrium and kinetics.

Abstract

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% de 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 intraparticle diffusion, 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 3 stages with an adsorbent-to-oil ratio of 0.5 (g g-1) and a 1:1 dilution in nhexane could refine the studied base oil (initial aromatics content 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 as compared to the oil.