Adsorptive removal of sulfur compounds from transportation fuels by using zeolitic adsorbents

In this study, the ion-exchanged zeolites were prepared by exchanging NaX and NaY zeolites with Ni²ᐩ and Cuᐩ cations using both LPIE and SSIE methods. These adsorbents were evaluated for their efficiency in removing 3-MT and BT in both binary and ternary systems of isooctane and benzene (or toluene) as model fuels. The results showed only 85% exchange in NaX and 68% exchange in NaY zeolites by LPIE technique. The optimum temperature for achieving a sufficient amount of metal loading by this technique on NaX and NaY was found to be 45°C and 135°C, respectively. In comparison with LPIE, the SSIE technique obtained 100% ion-exchange. In the static adsorption, the sulfur adsorption capacity increased in the order NiY (LPIE at 135°C) <NiX (LPIE at 45°C) <NiY (SSIE) for both sulfur compounds. Furthermore, the adsorption data of sulfur compounds in isooctane and benzene revealed that the removed rate and the overall sulfur uptake capacity of the adsorbents were significantly reduced when benzene was used, which can be attributed to the competitive π-complexation forming with the adsorbent between the aromatic (benzene) and sulfur compound. The equilibrium capacity under dynamic condition for 3-MT adsorption increased in the order of NaY < NiY < NiX < NaX <Cu(I)Y; while the selectivity for 3-MT over toluene exhibited the following trend NaY < NiY< NaX < NiX <Cu(I)Y. In addition, the pre-adsorbed water was found to have detrimental effect on the π-complexation bonding between adsorbent and sulfur compounds.