ADSORPTIVE DESULFURIZATION USING ACTIVATED CARBON

Abstract

Sulfur compounds represent one of the most prevalent impurities found in crude oil. New technologies are required to remove the sulfur from lower quality feed stocks to ensure that energy is available at a reasonable cost. New and more effective approaches and research is required for producing affordable ultra-low-sulfur transportation fuels, to comply with the new government sulfur regulations with maximum sulfur limit of 50 mg/1 as per Bharat IV norm. Deep desulfurization of gasoline is restricted largely by dibenzothiophene (DBT), which is the least reactive sulfur compound in gasoline. The aim of this thesis is to devise a novel desulfurization technique based on adsorption of DBT over commercial activated carbon (CAC) and alum impregnated commercial activated carbon (AMCAC). Characterization of adsorbets was carried out using standard procedures. Scanning electron microscope (SEM), energy dispersive x-ray (EDX), and fourier transform infrared spectroscopy (FTIR) studies were performed to understand the mechanism of oxidation of furkal. Presence of DBT on surface of adsorbents was confirmed by comparison of EDX and XRD of blank and DBT loaded adsorbents. The parameters studied are initial concentration (Co): 100-900 mg/1; adsorbent dosage (m): 2-22 g/1; time of adsorption (t): 15-735 min; and temperature (T): 10-50 °C. The individual and interactive effects of the above mentioned parameters have been studied using Central Composite Design. Pareto analysis of variance (ANOVA) of the results showed a high coefficient of determination value ( R2 was equal to 0.939 and 0.936 for CAC and AICAC, respectively). Fisher F-value of 16.50 for CAC and 15.92 for AICAC showed satisfactory prediction for second order regression model. Redlich-Peterson isotherm best represented the equilibrium adsorption data. The heat of adsorption and change in entropy for DBT adsorption onto CAC was found to be 9.74 KJ/mol and 85.91 KJ/mol K, respectively. The highest removal of DBT was obtained with Co= 100 mg/I, m= 20 g/l, t= 360 min and T= 30 °C. AICAC was found to give greater removal of sulfur than CAC.