Comparative Study of Nickel-Silica Catalyst Architectures for CO2 Methanation: Insights into Structure-Performance Relationships

Abstract

An attractive alternative for CO₂ utilization is its conversion into methane via the CO₂ hydrogenation reaction. Catalysts with different structures represent promising materials for achieving higher CO₂ conversions and CH₄ selectivity. Four distinct nickel-silica catalysts were synthesized using different methods. High-resolution microscopy combined with EDS analysis confirmed the diverse structural features of the catalysts: a supported material (SUP), an encapsulated (embedded) structure (EMBD), a multi coreshell morphology (SPHERE), and a nanoring morphology (RING). All catalysts showed the formation of well-dispersed nickel particles, with diameters in the range of 2-3 nm.The embedded catalyst stood out due to its stronger metal-support interaction and encapsulated structure, which were attributed to its specific synthesis method. These characteristics contributed to its superior CH₄ selectivity (83.35%), higher CH₄ formation rate (8.4 mmolCH₄/gNi•min), and lower CO formation rate (1.8 mmolCO/gNi•min) during the CO₂ hydrogenation reaction at 300 °C, 1 atm, a CO₂:H₂ ratio of 1:4, and a GHSV of 120,000 mL•gcat⁻¹•min⁻¹. EMBD catalyst remained stable for 50 h, with 60% CO₂ conversion and methane selectivity of 97%. The higher catalytic performance of EMBD catalyst was attributed to the combination of the encapsulation effect and the presence of nickel phyllosilicates, which strengthen metal-support interactions, while also facilitating CO re-adsorption and conversion to methane.