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Ni-Al mixed metal oxides have been successfully prepared by high shear mixer (HSM) and coprecipitation (CP) methods for low temperature CO methanation. In this work, Ni-Al (HSM-CP) catalyst presented small Ni crystallite size and high surface area, which all contribute to the methanation reaction at low temperature conditions. The obtained Ni-Al (HSM-CP) sample exhibited a mass of defective oxygen, thereby accelerating the dissociation of CO and ultimately increasing the activity of the catalyst. Ni-Al (HSM-CP) catalyst offered the best activity with CO conversion=100 % and CH4 selectivity=93 % at 300 ℃, and the CH4 selectivity can reach 81.8 % at 200 °C. In situ Fourier transform infrared spectroscopy (FTIR) and density functional theory (DFT) show that CHO and COH intermediates with lower activation energy barriers are produced during the reaction, and hydrogen-assisted carbon-oxygen bond scission is more favorable.

Low-temperature performance of non-noble metal Ni-based catalysts in CO2 methanation still faces great challenges. A series of NiMnAl-LDO (layered double oxides) catalysts with different processing conditions were prepared using the high-shear mixer-assisted method. The FH-C (80 °C) catalyst exhibited high activity in low-temperature CO2 methanation, and CO2 conversion and CH4 selectivity reached 85% and 97% at 200 °C. Characterization results show that the strong shear force of the high-shear mixer can improve the dispersion of the catalyst and reduce the particle size of the catalyst. The high-shear mixer treatment increases the CO2 chemisorption and the number of strongly basic sites on the catalyst. The main reason for the low-temperature activity of the catalyst is that the high-shear mixer increases the number of oxygen vacancies in the catalyst. In situ infrared probes into the surface species and intermediate products of the catalyst, confirming that formate is an intermediate product of the CO2 methanation reaction. Density functional theory calculations demonstrated that increasing the content of oxygen vacancies is beneficial for increasing the CO2 adsorption capacity of the catalyst and reducing the reaction energy barrier of CO2 → COOH*.

Ni/Al2O3 spherical catalysts were prepared by high shear mixer (HSM)-assisted coprecipitation (CP) and spray drying (SD) method for carbon monoxide (CO) and carbon dioxide (CO2) methanation. The effect of HSM technology on low-temperature methanation performance was studied. Ni/Al2O3 (HSM-CP-SD) catalysts provide excellent performance such as CO conversion of 100% and CH4 selectivity of 90% at 300 °C; the CO2 conversion was 86.2% and CH4 selectivity was 95.3% at 350 °C. Even at 200 °C, the catalyst prepared by HSM still offers a CO conversion of 90% and CH4 selectivity of 82%, whereas the Ni/Al2O3 (CP-SD) has no activity. The high performance was attributed to the small Ni nanoparticles and high dispersion. The Ni/Al2O3 (HSM-CP-SD) catalysts exhibit micro-spherical morphology with a big pore size of 3.46 nm, stronger metal-support interactions, and CO adsorption capacity. The catalyst prepared by HSM shows potential application for CO/CO2 methanation, and HSM technology can optimize other heterogeneous catalytic reactions.