Hydrogen production via CH4 pyrolysis: Regeneration of ex hydrotalcite oxide catalysts

Pure hydrogen was obtained by catalytic methane decomposition over thermally stable nickel-based catalysts prepared from hydrotalcite-like precursors. Two different Ni–Mg–Al catalyst compositions were tested in the catalytic pyrolysis reaction of methane. The catalytic results were compared with those of a catalyst prepared by conventional impregnation of Ni–Mg phases on an alumina support. The high thermal stability of these catalysts was demonstrated in several reaction–regeneration cycles. The regeneration processes were performed with CO2 and O2 as regenerating agents. Using either CO2 or O2 gas, hydrogen production after regeneration increased with regard to the fresh catalyst. Upon catalyst regeneration, larger amounts of hydrogen were obtained on catalysts regenerated with CO2 than with O2. The high thermal stability of the Ni particles of the catalysts from hydrotalcite-like precursors was improved in the presence of Mg. This high Ni-stability is a key factor for increasing hydrogen production after consecutive reaction–regeneration cycles.