Investigation of Molybdenum Iron Catalysts for Ethylene Production via Non‐Oxidative Coupling of Methane

ABSTRACT The reactivity of carbon‐supported MoFe catalysts with different Mo:Fe molar ratios has been studied for non‐oxidative methane coupling to valuable C 2 hydrocarbon products. The catalysts were characterized by x‐ray diffraction (XRD) after ex situ carburization, and a change in molybdenum phase from Mo 2 O 3 to Mo 2 C is observed. CO chemisorption suggests that Mo sites are blocked by Fe as the Fe loading increases. Energy dispersive x‐ray spectroscopy (EDS) mapping corroborates the formation of mixed Mo and Fe within the catalysts, and x‐ray photoelectron spectroscopy (XPS) analysis supports the presence of Fe on the surface. Opposite trends in turnover frequency calculated using site densities obtained from CO chemisorption versus scanning transmission electron microscopy (STEM) particle size analysis suggest that the addition of Fe alters the accessible Mo sites. The TOF of Mo/C and the bimetallic catalysts, Mo 27 Fe 1 /C and Mo 9 Fe 1 /C, decrease over time on stream. Overall, the bimetallic catalysts show similar or lower C 2 production rates than the monometallic catalyst and demonstrate > 85% ethylene selectivity for all catalysts. These results highlight that the intrinsic activity of these catalysts does not linearly increase with increasing iron content. Our results indicate that MoFe catalysts are active and selective for methane coupling to ethylene. Fe loading does not drastically impact performance and thus suggests that Mo sites alone influence the product formation.