Effect of Fe-loading in iron-based catalysts for the CH₄ decomposition to H₂ and nanocarbons

The catalytic CH₄ decomposition (CMD) over Fe-based catalyst is an economical and environmentally friendly way to produce Co_x-free H₂ and carbon nanotubes (CNTs). The Fe-loading was varied to study its influence on the catalytic performance. The highest H₂ yield (82.25%) was obtained with a 12% Fe content where the activity of the catalyst did not decrease for 3 h on-stream. A higher Fe content causes the Fe dispersion to decrease, resulting in a reduced available surface area of active sites. Different techniques were used to characterise the fresh and spent catalysts i.e., ICP-AES, XRD, H₂-TPR, SEM, TEM, and Raman spectroscopy. Plotting kinetic results as a function of 1/T, defines two different conversion ranges, being reaction rate controlled at low temperature and diffusion rate controlled at high temperature. For the reaction rate controlled regime, the Arrhenius equation provides an activation energy of 101.26 kJ/mol (E_a) and a pre-exponential factor of 393 kmol/s (A).