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

Abstract

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.