Development of modified zeolite for adsorption of mixed sulfur compounds in natural gas by combination of ion exchange and impregnation

Abstract

The economic and environmental benefits of natural gas in energy applications are widely known; consequently, the usage of natural gas has increased steadily with increasing environmental regulations in recent years. However, the widespread utilization of natural gas has been limited by regulations that require sulfur compounds to be added to natural gas for leak detection. Even traces of sulfur compounds can permanently poison the catalysts used for natural gas; hence, sulfur compounds should be removed for various natural gas applications. In this study, NaY-zeolites were modified by combining Cu ion-exchange and Na2O or CuO impregnation for adsorptive desulfurization. Adsorption experiments were conducted on gas mixtures containing ppm-level tetrahydrothiophene (THT) and tert-butyl mercaptan (TBM) in CH4 to compare the desulfurization performance of pristine and modified Y-type zeolites. The analysis results show that both Na2O and CuO caused changes in the acid sites and binding energies of metal atoms in the Cu ion-exchanged Y-zeolite. Na2O promoted the adsorption of TBM, while CuO inhibited it. Among the tested samples, the Cu ion-exchanged Y-zeolite containing Na2O showed the most efficient adsorption performance with a 3.97 wt% uptake for TBM, which is 30% higher than that of the Cu ion-exchanged Y-zeolite. The Cu ion-exchanged Y-zeolite containing CuO showed the lowest adsorption ability with a 2.21 wt% uptake for TBM.