NiFe/Al2O3/Fe-frame catalyst for COx-free hydrogen evolution from catalytic decomposition of methane: Performance and kinetics

Catalytic decomposition of methane is more economic and greener than steam reforming of methane in meeting the small to medium scale demand on the high purity hydrogen. A novel iron knitting gauze supported NiFe/Al2O3/Fe-frame catalyst was prepared by ball milling and washcoating method with longer catalyst service time and slower pressure drop buildup. The hydrogen production rate as high as 9.48 mmol⋅g−1⋅min−1 and the catalyst life of 600 min are achieved. Moreover, the activation energy for deactivation is as high as 208.5 kJ⋅mol−1. It is interesting that carbon products, mainly carbon nanotubes, preferentially deposit and accumulate on the leeward side of the gauze catalyst, and its graphitization degree decreases from the R (IG/ID) = 4.1 to 0.7 in the initial 50 min which agrees with the bulk diffusion mechanism. The porosity of the NiFe/Al2O3/Fe-frame decreases from 0.971 to 0.00159 in 24 h due to the growth of carbon. Furthermore, the apparent activation energy of methane decomposition varies with the packing modes of catalysts, and it is 77.2, 101.3 and 86.8 kJ⋅mol−1 for a filling, tiling and monolithic type packing, respectively. The pressure drops of a monolithic packing bed builds up much slower than a filled packing bed, but it is similar to a tiling type one. The NiFe/Al2O3/Fe-frame has been found to be an efficient and productive catalyst for the evolution of high-purity hydrogen from the catalytic decomposition of methane.