A study of the adsorption of thiophenic sulfur compounds using flow calorimetry

Selective adsorption of sulfur compounds from gasoline and diesel fuel has potential to produce ultra clean fuels for on-board fuel cell applications and also to meet the upcoming legislation for clean fuels. Removal of thiophenic sulfur compounds in a hexadecane solution using commercial zeolites, NaY, USY, HY and 13X, has been investigated by adsorption and flow calorimetry techniques. The S compounds chosen were thiophene (T), benzothiophene (BT), dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT). The adsorption studies were carried out in the liquid phase at 55 °C. Among the zeolites studied, NaY has the highest saturation sorption capacity for the sulfur compounds. The overall heat of adsorption of sulfur compounds in a hexadecane solution was measured at 30 °C using a flow microcalorimeter. A linear correlation between the heat of adsorption and the amount of S adsorbed was found for NaY. Competitive adsorption using a mixture of anthracene, DBT and quinoline indicates that NaY selectively adsorbs quinoline while anthracene and DBT have similar affinity to NaY. Liquid flow calorimetry combined with the analysis of the effluent from the calorimeter is a promising technique to aid the development of selective sorbents for S removal and other sorption processes since it provides information on the relative heats of adsorption, the sorption capacity and the breakthrough curves.