Highly dispersed Cu-anchored nanoparticles based mordenite zeolite catalyst (Cu-MOR): Influence of the different preparation methods for direct methane oxidation (DMTM) to methanol

Methane is widely recognized as one of the most significant greenhouse gases released into the atmosphere by shale gas and natural gas, contributing to global warming. Developing innovative technology for converting methane into transferable, storable, and useable liquid fuels is essential for long-term sustainability and carbon neutrality. Direct methane oxidation (DMTM) is one of the most efficient and cost-effective methods for producing methanol. The purpose of this research was to develop a highly active Cu-loaded mordenite zeolites (Cu-MOR) catalyst by the hydrothermal and ion exchange processes. Different methods were employed for Cu incorporation via double solvent, physical mixing, wetness impregnation, and incipient wetness impregnation. The synthesized catalysts were characterized by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), N₂-adsorption analysis, Fourier Transform Infrared Spectroscopy (FTIR), and Methane Temperature Programmed Desorption (CH₄-TPD). The DMTM was performed, and it was found that the Cu-MOR (WI) catalyst that was prepared by wetness impregnation exhibited a higher methanol yield (26.5 μmol gcat⁻¹) compared to other catalysts as a result of the high metal dispersion and high methane adsorption. According to data from TEM and CH₄-TPD, this superior performance was strongly related to the particle sizes of copper and the synthesis methods used. Additionally, it was discovered that the longer the methane was in contact with the Cu-MOR (WI), the greater the amount of methanol that was produced (83.3 μmol gcat⁻¹). Based on the finding that the Cu-MOR (WI) catalyst is highly efficient for the DMTM, this study has the potential to significantly decrease methane emissions.