Separation ofn-Paraffins from Kerosene-Range Feedstock by Adsorption on Fixed-Bed Urea

Experimental breakthrough curves have been obtained for n-paraffins from kerosene-range feedstocks on fixed-bed urea. The feedstocks used were unified heavy kerosene, straight-run kerosene, and naphtha-kerosene blend with initial n-paraffin contents of 29.31, 31.87, and 34.71 wt%, respectively. The breakthrough curves were measured in the temperature range 283–303 K and the feed flow rates 0.8–2.5 cm3/min. The dynamic parameters for adsorption, such as the height of the mass transfer zone, the dynamic capacity, and the column efficiency, were determined from experimental breakthrough curves. The results from this study indicated that the n-paraffin molecules from unified heavy kerosene were more strongly adsorbed than those from straight-run kerosene or naphtha-kerosene blend, thereby revealing that n-paraffin adsorption on urea increased with the molecular length of the hydrocarbon. The values of the estimated apparent diffusion coefficients for n-paraffin from naphtha-kerosene blend ranged from 3.28 × 10−12 cm2/s at 283 K to 5.06 × 10−12 cm2/s at 303 K. The activated energy for diffusion was found to be 20.9 kcal/mol.