Removal of thiophenic sulfur compounds from transportation fuels by adsorption using NaX and NaY zeolites

Abstract

An increasing demand in the production of ultra low sulfur fuels has driven refineries around the world to pay more attention to adsorption process for the removal of refractory sulfur compounds, which are known to be difficult to remove by the conventional hydrodesulfurization process (HDS). In this research, the adsorption of three thiophenic sulfur compounds, 3-methylthiophene (3-MT), benzothiophene (BT), and dibenzothiophene (DBT), on NaX and NaY zeolites were studied using batch liquid experiments. Decane and isooctane were used as model transportation fuels, representing diesel and gasoline, respectively. The effects of aromatic content and water content in zeolite on sulfur adsorption were examined. NaX had better adsorption ability for thiophenic sulfur compounds than NaY. BT and DBT were preferentially adsorbed on both zeolites compared with 3-MT in both single- and mixed-solute systems. In the presence of an aromatic compound, o-xylene, the adsorption of all three sulfur compounds decreased significantly. A similar trend was observed when the water content of the zeolite was increased. By increasing temperature, desorption of adsorbed sulfur compounds was successfully achieved. It was found that 3-MT, having weak interaction with zeolite surface, desorbed by the highest amount compared with BT and DBT.