Tailoring Ni-based poly-metallic catalysts for enhanced CO2 methanation through a Simplex-Centroid Mixture Design (SCMD)

Abstract

The study explored the development and optimization of Ni-based polymetallic catalysts for CO₂ methanation using a systematic Simplex-Centroid Mixture Design (SCMD). This approach aimed to maximize catalytic performance while ensuring stability and catalytic effectiveness. The research began by selecting optimal Ni loading on alumina (γ-Al₂O₃) support, revealing a 10 wt% Ni content yielded the highest CO₂ conversion. Various promoters, including Ce, La, Fe, Co, and Mg, were then evaluated to enhance catalytic efficiency, with Ce emerging as the most effective. Ce addition significantly improved CO₂ conversion and CH₄ selectivity, and among the optimized formulations, AlNi_9.2Ce_8.3 achieved 78 % CO₂ conversion and 99 % CH₄ selectivity at 350 °C. Incorporating Y₂O₃ into the γ-Al₂O₃ support provided further advancements in catalyst performance, particularly in improving the catalyst's thermal stability, thereby reducing sintering and enhancing overall durability. However, the amount of Y₂O₃ was crucial; while optimal Y₂O₃ content (5 wt%) stabilized active sites and enhanced metal dispersion, excessive Y₂O₃ could obstruct catalytic sites (> 15 wt%), negatively affecting performance. Characterization analyses, including X-ray diffraction (XRD), Raman spectroscopy, and H₂ temperature-programmed reduction (H₂-TPR), showed 5–10 wt% Y₂O₃ addition increased oxygen vacancy formation, increased catalyst reducibility, reduced Ni particle sintering, and inhibited coke deposition and spinel (NiAl₂O₄) formation. The SCMD-enabled catalyst design successfully balanced Ni, Ce, and Al₂O₃ contents to deliver efficient CO₂ methanation. The tailored Ni-based catalysts thus demonstrated improved resistance to degradation mechanisms and greater catalytic efficiency, positioning them as promising candidates for sustainable CO₂ conversion and CH₄ production.