Hydrogen production by methane decomposition over Cu-Ni-Al-LDH: Influence of Ni/Cu ratio and catalyst activation

Hydrogen from the decomposition of CH4 is an essential source of clean energy and contributes to a decarbonization process. In this work, Cu-Ni-Al-LDH were prepared by coprecipitation, evaluating the Ni/Cu ratio and the catalyst activation. The samples were characterized through N2-adsorption-desorption, XRD, H2-TPR, NH3-TPD, TPO and SEM. The catalytic activity was evaluated between 500 and 700 °C in a fixed bed reactor with online GC analysis. Reactions at 600 °C during 6 h were also carried, with samples previously reduced with H2 or activated with CH4. The characterization results show that the increase of copper caused a decrease in the specific area, enhanced the acidity, and decrease the reduction temperature of catalysts, due to the presence of Cu-Ni alloy phase. Activity results at variable temperature showed a strong deactivation by sintering for NiAl catalyst at 600 °C, differently of Cu-containing catalyst which presented a high thermal stability, independently of activation with H2 or with CH4. For reactions with a constant temperature of 600 °C and activated with CH4, the order of activity of the catalysts was Cu11 ≫ Cu22 > Cu33 ≫ NiAl, while deactivation was in the reverse order. The catalyst with the lowest Cu content (Ni/Cu = 5) activated with CH4 was the one that presented the best activity results. Deactivation of the catalyst without Cu occurs through sintering, whereas the Cu-Ni alloy was essential to increase the resistance to sintering in Cu-containing catalysts. Activation with methane proved to be a beneficial substitute to H2-reduction.