Zr-Modified Ni/CaO Dual Function Materials (DFMs) for Direct Methanation in an Integrated CO₂ Capture and Utilization Process

An integrated CO2 capture and direct methanation (ICCM) system has recently gained significant attention as a promising process to produce value-added chemicals. Compared to conventional CO2 capture and utilization, ICCM is a simplified process that directly converts captured CO2 without purification at lower thermal inputs. One of the primary limitations is the deactivation of the sorbent and the embedded catalysts after several thermal cycles. In this study, we formulated thermally stable macroporous structured Ni/CaO dual function materials (DFMs) by incorporating a Zr stabilizer. The textural properties, porosity, CO2 capture performance, and catalytic activity of Zr-modified Ni/CaO (Ni/CaZr) were assessed. In situ DRIFTS was used to investigate the possible intermediates and reactions during the ICCM. It was found that CH4 is produced from the formate and methoxy intermediates route on the CaO surface and the CO intermediate route on the Ni surface. Ni/CaZr had improved thermal stability with the best CO2 capture capacity (13-14 mmol of CO2/g), CH4 productivity (13-14 mmol of CH4/g), CO2 sorption, and desorption kinetics at 500 degrees C. The benefit of adding Zr for ICCM enhanced the macroporous structures, which enhanced the CO2 mass transport and prevented the sintering of Ni and CaO.