CO₂ methanation over LDH derived NiMgAl and NiMgAlFe oxides: Improving activity at lower temperatures via an ultrasound-assisted preparation

Within the idea to catalyze CO₂ methanation NiMgAl and NiMgAlFe oxides were synthesized by the layered double hydroxide route using co-precipitation and ultrasound-assisted co-precipitation. MgAl and MgAlFe oxides-supported Ni materials prepared by the impregnation method were used as references. Inductively-coupled plasma optical emission spectroscopy, X-ray diffraction, thermal decomposition, H₂-temperature programmed reduction, N₂ physisorption, and transmission electron microscopy were used to characterize the catalysts. NiMgAl prepared using ultrasound-assisted co-precipitation showed the best activity with no deactivation for 40 h under stream. This was attributed mainly to the lower particle size, the higher specific surface area and pore volume as well as the better dispersion of nickel active species at the surface of the concerned materials. In our case, the ultrasound method saves a lot of time during the synthesis process since the maturation phase lasts only 30 min instead of 18 h required for the traditional co-precipitation.