Hydrogen Sulfide Removal from Biogas using Ion-Exchanged Nanostructured LTA Zeolite for Fueling Solid Oxide Fuel Cells

The aim of this work was investigating the hydrogen sulfide adsorption properties of synthetic and commercial zeolites. The nanostructured LTA zeolite was synthesized using appropriate amounts of sodium silicate solution, aluminum silicate powder and sodium hydroxide scales in ambient pressure and 40 ˚C and characterized by XRD, FT-IR and SEM analysis. The ion-exchange process was applied on as synthesized zeolite to improve its adsorption properties. 2 g of as synthesized zeolite was mixed with 0.1M of silver nitrate solution and stirred for 16 hours in ambient temperature. After that the milky solution was filtered and the obtained solid phase was washed with deionized water and then dried at 120 ˚C overnight. The hydrogen sulfide adsorption properties of these synthetic zeolites were compared to a commercial LTA zeolite using adsorption tests. H2S adsorption tests were carried out in a laboratory scale plant equipped with stainless still and Teflon pipes and a Pyrex reactor. A gas stream of 15 ppm H2S in nitrogen matrix was passed through the reactor which was filled with 20 mg of adsorbents with given flow rate and the outlet stream of the reactor was analyzed by a gas chromatograph equipped with a flame photometric detector for H2S detection. The breakthrough point was defined as a time that 1ppm of H2S was detected in the reactors outlet (the H2S tolerance limit for SOFCs) and the adsorption capacity of sorbents were measured at this point. The best adsorption capacity was for ion-exchanged zeolite followed by synthesized zeolite while the commercial zeolite showed the lowest capacity for H2S.