(371c) Adsorption Mechanism of Ultra-Low Concentration H2s and THT in CH4 on Zeolites in the Presence of CO2

Commercially available natural gas contains certain ppm of sulfur compounds such as H₂S, THT, and TBM. 5-15 ppm of sulfur content in natural gas is acceptable as fuel, while less than 1 ppm of sulfur level is required for the applications of the fuel cell. Sulfur compounds play a critical role in natural gas reforming catalysts as well as WGSR catalysts. In addition, a trace amount of sulfur compounds highly deteriorate the lifetime of cyclic adsorptive processes. The removal of high-concentration H₂S with/without other impurities in natural gas has been studied intensively. On the other hand, although the adsorption mechanism at a trace concentration from a few ppm to ppb level is practically important, few studies are conducted.

In this study, the breakthrough experiments in the bed packed with zeolites 5A and 13X pellet are carried out using a ppb level detectable analyzer at 4 ppm of H₂S or THT balanced with CH₄. In addition, since natural gas also contains a certain level of CO₂,the breakthrough experiments using the ternary mixture including CO₂ are also conducted to elucidate the effects of another impurity on the removal of sulfur compounds from natural gas. The results reveal the influence of CO₂ on sulfur removal in the ultra-low concentration region and clearly show the different adsorption behavior between two adsorbates.