(687a) Probing Metal-Organic Framework (MOF) Design for Adsorptive Sour Natural Gas Purification

Parent and amine-functionalized analogues of the metal-organic frameworks (MOFs) UiO-66(Zr), MIL-125(Ti), and MIL-101(Cr) were evaluated for their hydrogen sulfide (H₂S) adsorption efficacy and post-exposure acid gas stability. Adsorption experiments were conducted through fixed-bed adsorption breakthrough studies, utilizing multicomponent 1% H₂S/99% CH₄ and 1% H₂S/10% CO₂/89% CH₄ test gases as simplistic representative sour gas mixtures. Pelletized MIL-101(Cr) adsorbents were found to be unstable through diffraction and porosity measurements following H₂S exposure, while other materials retained their characteristic properties. Linker-based amine functionalities increased H₂S breakthrough times and saturation capacities from their parent MOF analogues. Competitive CO₂ adsorption effects were mitigated in mesoporous MIL-101(Cr) and MIL-101-NH₂(Cr), in comparison to microporous UiO-66(Zr) and MIL-125(Ti) frameworks. This result suggests the installation of H₂S binding sites in large pore MOFs could potentially enhance H₂S selectivity. In-situ FTIR measurements in 10% CO₂ and 5000 ppm H₂S environments illustrate framework hydroxyl and amine moieties serve as selective H₂S physisorption sites. Results from this study elucidate design strategies and stability considerations for engineering MOFs in sour gas purification applications.