A novel nickel catalyst supported on fly ash-derived zeolite ZK-14 for CO2 methanation via in situ reduction

Abstract

Coal-fired power generation not only emits substantial amounts of carbon dioxide (CO₂) but also produces the by-product fly ash, causing environmental pollution. Therefore, there is an urgent need for innovative technologies to repurpose waste fly ash and convert CO₂ into clean energy sources. In this study, fly ash was used as the raw material to synthesize Ni/zeolite ZK-14 catalysts via an alkali fusion-hydrothermal method and in situ reduction. Under the optimized conditions, the Ni/zeolite ZK-14 catalyst with 30 wt% Ni loading exhibited superior catalytic performance for CO₂-to-CH₄ directional conversion, with a CO₂ conversion of 54.6% and a CH₄ selectivity of 98.7% at 300 °C. The superior catalytic performance observed in CO₂ methanation can be primarily attributed to the presence of highly dispersed Ni nanoparticles (NPs), abundant weakly basic sites, and the oxygen vacancies on the catalyst. In addition, in situ DRIFTS analysis reveals the formation of HCOO* intermediates, suggesting that 30 wt% Ni/zeolite ZK-14 is a suitable catalyst for the CO₂ methanation reaction via the formate pathway. This study presents a viable strategy for developing fly ash-derived zeolite catalysts for low-temperature CO₂ methanation.