Continuous CO2 capture and methanation over Ni–Ca/Al2O3 dual functional materials

Abstract

Although Ni–Ca-based dual functional materials (DFMs) have been examined for CO₂ capture and reduction with H₂ (CCR) for the synthesis of CH₄, their performance has generally been investigated using single reactors in an oxygen-free environment. In addition, continuous CCR operations have scarcely been investigated. In this study, continuous CCR for the production of CH₄ was investigated using a double reactor system over Al₂O₃-supported Ni–Ca DFMs in the presence of O₂. We found that a high Ca loading (Ni(10)–Ca(30)/Al₂O₃, 10 wt% Ni, and 30 wt% CaO) was necessary for reaction efficiency under isothermal conditions at 450 °C. The optimized DFM exhibited an excellent performance (46% CO₂ conversion, 45% CH₄ yield, and 97% CH₄ selectivity, respectively) and good stability over 24 h. The structure and CCR activity of Ni(10)–Ca(30)/Al₂O₃ were studied using X-ray diffraction (XRD), scanning transmission electron microscopy (STEM), energy-dispersive X-ray spectrometry (EDS), temperature-programmed desorption (TPD), and temperature-programmed surface reaction (TPSR) techniques.