Silicalite-Supported Ni Catalysts for Efficient CO₂ Conversion into CH₄

The catalytic conversion of CO₂ into methane (CH₄) offers a sustainable solution to the worsening global warming scenario, especially for controlling CO₂ levels. This study reports silicalite-1 supported Ni catalysts with different loadings for CO₂ conversion to CH₄, prepared via wet impregnation. The X-ray diffraction pattern revealed an increase in crystallite size at higher Ni loadings, which was further supported by N₂ sorption, where the specific surface area and microporosity of the catalysts were decreased. There was a slight shift in the reducibility of the catalysts, potentially indicating the impact of loading on dispersion and spatial distribution. The catalyst performance was evaluated over a range of temperatures at 5 bar and a GHSV of 20,000 mL g_cat^-1 h^-1. Surprisingly, the Ni(5)@Silicalite-1 exhibited higher CO₂ conversion efficiency across the range of temperatures compared to Ni(10)@Silicalite-1. The NiO(5)@Silicalite-1 demonstrated a maximum CO₂ conversion of 88% at 450 °C, which was approximately 14% higher than that of the catalyst with a 10 wt.% loading. Notably, the CH₄ selectivity pattern was quite identical across the catalysts, underscoring that the reaction pathways were unaffected by the loadings. The higher performance of NiO(5)@Silicalite-1 could be ascribed to smaller NiO crystallites and improved textural properties.