CO2 and H2S Adsorption on γ-Al2O3-Supported Lanthanum Oxide

The use of high temperatures (>873 K) for desulfurization of syngas has the potential to significantly increase the efficiency of gasification processes. Rare earth oxides are effective adsorbents at high temperatures but expensive. In this work, lanthanum oxide at low weight loadings (2.5-7.5 wt %) is supported on gamma-Al2O3 to more efficiently use lanthanum oxide for hot gas desulfurization. The adsorbents are characterized with CO2 adsorption and tested in a fixed-bed reactor for H2S capture at 873 K over multiple cycles. The interaction between lanthanum oxide and the support varied with loading, and regeneration with humidified argon is better than with dilute oxygen. Although the capacity per gram of lanthanum is higher for supported lanthanum oxide, these adsorbents are not selective for the adsorption of H2S in the presence of CO2, CO, and CH4 likely as a result of site competition with CO2 and H2O.