Synthesis of MgAl₂O₄ by sol-gel method and investigation of catalytic performances in CO₂ methanation

CO₂ levels in the atmosphere are increasing as a result of human activities such as industrial activities, fossil fuel usage, and deforestation. The CO₂ methanation reaction, which converts CO₂ into methane, may play a crucial role in addressing this issue. Like most commercial syntheses, the CO₂ methanation process requires a catalyst. Spinel catalysts, particularly magnesium aluminate (MgAl₂O₄), have gained attention for their potential in CO₂ methanation. In this study, MgAl₂O₄ nanoparticles were synthesized using a sol–gel method with a molar ratio of Mg:Al = 1:2, and calcined at temperatures ranging from 700 to 900 °C. The structural properties of the nanoparticles were characterized using differential scanning calorimetry, thermogravimetric analysis, Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller analysis, X-ray diffraction, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, and transmission electron microscopy. The results showed that the particles had nearly spherical morphology, with agglomeration occurring at higher temperatures. The surface area decreased with increasing calcination temperature, from 188 m²/g at 700 °C to 94 m²/g at 900 °C. NiCo-MgAl₂O₄ catalysts were prepared by impregnation and characterized by CO₂ temperature-programmed desorption and hydrogen temperature-programmed reduction. Catalytic performance tests revealed that the NiCo-MgAl₂O₄ catalyst calcined at 800 °C achieved the highest CO₂ conversion (~85%) and methane selectivity. Spent catalyst analysis showed that carbon deposition negatively affected catalyst performance over time. This study emphasizes the role of strong basic sites in CO₂ activation and methane formation, suggesting future improvements in catalyst stability.