Evaluating the Impact of Preparation Method on the Performance of Metal-Oxide Adsorbents/Catalysts for Ethyl Mercaptan Removal from Natural Gas

The presence of toxic, corrosive, and environmentally harmful sulfur compounds within natural gas streams necessitates their removal to ensure compliance with fuel quality standards and regulations. Previous studies into MMOs (mixed metal-oxides) as adsorbents or catalysts for sulfur compound removal have generally focused on hydrogen sulfide (H2S); however, few studies have assessed the removal of organic sulfur compounds such as ethyl mercaptans. The purpose of this research is to investigate the effects of various preparation routes on the performance of supported metal-oxide catalysts that remove ethyl mercaptans from natural gas; specifically, filtration-based and evaporation-based catalyst synthesis methods were investigated. A set of different catalysts—Mn, Cu, Zn, Ni, and a composite (Mn-Cu-Zn-Ni)—were prepared using filtration or evaporation solvent removal in this research and characterized by BET, FTIR, XRD, SEM, EDS, and XPS, and their sulfur-removal performance was evaluated through fixed-bed breakthrough experiments under representative operating conditions (25 °C, 200 psi, 36 mL/min). The results demonstrate that catalysts prepared via evaporation consistently exhibit greater sulfur adsorption performance compared to catalysts prepared through filtration, which is consistent with improved surface oxide exposure. Structural characterization further showed that evaporation-assisted preparation promoted improved surface oxide development, greater surface heterogeneity, and more accessible surface morphologies. Among the investigated catalysts, evaporation-prepared Mn and Cu catalysts achieved the highest breakthrough times of approximately 1410 min and 1350 min, respectively, exceeding the commercial benchmark catalyst (1200 min) under identical operating conditions. These findings demonstrate that the evaporation method enables more effective utilization of surface metal-oxide active sites involved in sulfur adsorption and surface redox interactions. Overall, this work establishes evaporation as a superior and scalable preparation strategy for metal oxide catalysts and provides important structure-performance insights for the design of cost-effective catalysts for industrial natural gas desulfurization, particularly for the removal of organic sulfur compounds such as ethyl mercaptan from natural gas.