Mechanistic insights into the ultra-deep desulfurization of liquid fuel on date-seed derived hierarchical porous carbon

Abstract

This study described the synthesis of activated carbon and its application in the removal of DBT and DMDBT from isooctane using both experimental and DFT calculations. The effect of synthesis conditions (pyrolysis temperature, precursor-activator ratio and ramping rate) on the properties of activated carbon were also presented. Activated carbon (AC) of high surface area and porosity was synthesized from an agricultural waste material (date seeds) using Zn-acetate as an activator. Thorough study of the characteristic activity and selectivity of this adsorbent in the removal of organosulfur compounds; dibenzothiophene (DBT) and dimethyldibenzothiophene (DMDBT) at room temperature were carried out. DFT simulations predicted the selectivity of AC towards DMDBT promoted by the charge donation and the positive inductive (+ I) effects of the methyl groups resulting in strong van der Waals interactions and theoretical adsorption energy of – 12.3 kcal/mol. It was observed that surface area, porosity, and surface chemistry of the adsorbent highly depends on the process parameters. The adsorbent pyrolyzed at 1000 °C and 10 °C/min performs better and shows exceptional capability to remove DBT and DMDBT (200 ppmw-S) in model fuel to almost sulfur-free fuel at minimum adsorbent weight (200 mg). However, the precursor-activator ratios at optimum pyrolysis temperature and ramping rate had little effect on the adsorbents’ performance. DMDBT was found to preferentially adsorb on the adsorbents with increasing pore size and volume than DBT. The kinetics and isotherms studies confirmed that the obtained data fitted more to pseudo-second order and Langmuir model.