Evaluating the Impact of Preparation Method on the Performance of Metal-Oxide Catalyst 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 adsorbent or catalysts for sulfur compound removal have generally focused upon hydrogen sulfide (H2S); however, few studies have assessed the removal of organic sulfur compounds like 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 mercaptans from natural gases; specifically, filtration-based and evaporative 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 adsorption performance was assessed 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 compounds adsorption performance compared to catalysts prepared through filtration method, primarily due to enhanced retention of active metal species and improved surface accessibility. As confirmed from the characterization, all these improvements result from the fact that the evaporation method enhances the interaction between the metals and oxygen (FTIR); increases the amount of oxides formed as well as improves their distribution (XRD); provides access to more available metal surfaces (XPS/EDS); and creates pore structures and morphologies that are more open and accessible (SEM/BET). Among the catalysts studied, the Mn and Cu catalysts prepared by evaporation achieved the highest breakthrough times 1410 minutes and 1350 minutes, respectively, exceeding the performance of a commercial benchmark catalyst with breakthrough time of 1200 minutes under identical conditions. These findings demonstrate that the evaporation method enables more effective utilization of metal-oxygen active sites and significantly enhances sulfur adsorption capacity. 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 catalyst for industrial natural gas desulfurization, particularly for the removal of organic sulfur compounds from natural gas.