Methane decomposition over Ni–Fe/Al2O3 catalysts for production of COx-free hydrogen and carbon nanofiber

Abstract

The catalytic behavior of iron promoted nickel catalysts supported on nanocrystalline gamma alumina was investigated for the simultaneous production of COx-free hydrogen and carbon nanofibers via methane thermocatalytic decomposition. The prepared catalysts exhibited mesoporous structure with high surface area from 89.2 to 74.8 m2g−1 depending on the iron content. X-ray diffraction (XRD) studies revealed the formation of NiFe2O4 species and Ni–Fe alloys in calcined and reduced catalysts, respectively. Temperature programmed reduction (TPR) analysis showed that the addition of iron to nickel catalyst decreased the degree of reducibility. The results also revealed that addition of iron to nickel catalyst improved the catalytic stability by enhancing the rate of carbon diffusion and preventing the formation of encapsulating carbon. Scanning electron microscopy (SEM) analysis of the spent catalysts with various reaction temperatures showed that generated carbon is in intertwined filaments form and confirmed that the diameter and length of carbon nanofibers decreased by increasing reaction temperature.