Desulfurization and kinetic study of diesel fuel by batch adsorption on activated carbon

The present research studied a batch adsorption desulfurization process for diesel fuel containing 580ppm sulfur, based on physical adsorption of refractory sulfur compounds on activated carbon (AC). The effects of time, temperature, diesel to AC ratio, AC particle size, mixing velocity, and initial sulfur concentration in commercial diesel fuel on the desulfurization efficiency were studied. The residual sulfur concentration in diesel fuel was decreased from 580 to 247ppm, corresponding to a desulfurization efficiency of 57%, at best conditions of 2.5 hours contact time, 50°C, 2ml diesel/gm AC, 0.8 mm AC particle size, and 1000 rpm mixing velocity. Different kinetic models were applied to fit the experimental data. The results showed that the pseudo-second order model has succeeded in predicting the equilibrium sorption capacity with correlation coefficient, R2=0.995. The experimental adsorption isotherms were correlated by Langmuir and Freundlich models. The results indicated that Freundlich isotherm exhibits the best fits for the adsorptive desulfurization of diesel fuel (R2= 0.989) as compared with the Langmuir model (R2=0.947). The adsorption intensity as estimated from the Freundlich isotherm is larger than one which is indicative of physical adsorption.