Natural kaolin-derived ruthenium-supported nanoporous geopolymer: a sustainable catalyst for CO2 methanation

Abstract

To address the serious concern of excessive CO₂ emissions, the conversion of environmental CO₂ into methane via a CO₂ methanation reaction is promising. Methane can be used not only as a fuel but also as a hydrogen carrier. In this study, a geopolymer synthesized using natural kaolin (GNK) is explored as a support. This geopolymer support was used to disperse ruthenium (Ru) nanoparticles through a single-step hydrazine reduction method. The catalyst was characterized using various surface and bulk techniques. Furthermore, the catalytic performance of the ruthenium-supported geopolymer (Ru/GNK) for the CO₂ methanation process was explored with different Ru loadings (%) and at different flow rates. Catalyst stability was also investigated for 20 h by a time-on-stream isothermal experiment. The spent catalyst was characterized by O₂-temperature programmed oxidation (O₂-TPO) and X-ray photoelectron spectroscopy (XPS). Overall, the catalyst proved to be cost-effective and free from pretreatment requirements, in addition to exhibiting superior activity, high selectivity, and good stability.