Methane direct conversion to olefins, aromatics, and hydrogen over silica entrapped bimetallic MeFe-SiO2 (Me = Co, Ni, Pd, Pt) catalysts

Here, MeFe-SiO2 (Me = Co, Ni, Pd, Pt) catalysts with bimetallic sites entrapped in a highly crystalline SiO2 structure were synthesized and used for the conversion of methane to olefins, aromatics, and hydrogen (MTOAH) at 1020 degrees C. The MeFe-SiO2 catalysts showed polymorphic forms of cristobalite, quartz, and tridymite after re-action. Among the bimetallic catalysts, 0.5Pt1.0Fe-SiO2 exhibited the highest methane conversion (10.0%) with high hydrocarbon selectivity (79.9%) at 1020 degrees C. In C2 (ethane, ethylene, acetylene) conversion with hydrogen co-feeding at 1020 degrees C, acetylene was identified as a major coke precursor. MTOAH with different gas hourly space velocities (GHSV) showed that the 0.5Pt1.0Fe-SiO2 catalyst exhibited higher methane conversion and aromatics selectivity than the 1.0Fe-SiO2 catalyst. Density functional theory calculations showed that the Pt-Fe3C surface is energetically favorable for methane activation and inhibits graphitic coke deposition by C2 dehydrogenation. Consequently, a modification of the entrapped Fe sites by Pt addition improved the methane conversion and hydrocarbon selectivity of the catalyst.

Automated summary

In this study, MeFe-SiO2 (Me = Co, Ni, Pd, Pt) catalysts with bimetallic sites entrapped in a highly crystalline SiO2 structure were successfully synthesized and used for the conversion of methane to olefins, aromatics, and hydrogen (MTOAH) at 1020 degrees C. The presence of Pt in 0.5Pt1.0Fe-SiO2 catalyst enhanced methane conversion and hydrocarbon selectivity by inhibiting coke deposition. Density functional theory calculations confirmed the energetically favorable role of Pt-Fe3C surface in methane activation.