Investigation of metal-exchanged mesoporous Y zeolites for the adsorptive desulfurization of liquid fuels

Removal of sulfur from transportation fuels using zeolites as sorbents is an attractive desulfurization method, because of its low energy and cost requirements. However, diffusion limitations within the micropore structure of zeolites can reduce their adsorption capacity, especially when refractory sulfur compounds are present in fuels. Moreover, the selective adsorption of sulfur compounds from a mixture of hydrocarbons can be very challenging. The objective of this study was to address the aforementioned challenges of adsorptive desulfurization of fuels using metal-exchanged mesoporous Y zeolites. Mesoporosity was introduced in the Y zeolites by two top-down methods (desilication and surfactant-assisted). Metals, Ce and Cu, were introduced via ion-exchange. The prepared metal-exchanged mesoporous zeolites were characterized and tested in terms of their sulfur adsorption capacity using a fixed-bed column and model fuels. The strength of adsorption was determined using isosteric heat of adsorption calculations. Our results demonstrated that mesoporous Y reduced diffusion limitations and were very effective sorbents for removing sulfur compounds with high kinetic diameter, such as dibenzothiophene (DBT). Metals highly increased the selectivity toward sulfur compounds. According to experimental results, the tendency of thiophenic molecules to adsorb on the zeolites increase in the order of thiophene (TP) < benzothiophene (BT) < DBT. The results of this study revealed that metal-exchanged mesoporous Y zeolites have the potential to display remarkable sulfur removal properties since the mesopores allow access to zeolite active sites while the metal cations improve the selectivity and/or capacity for sulfur compounds. (C) 2016 Elsevier B.V. All rights reserved.