Understanding the interaction between active sites and sorbents during the integrated carbon capture and utilization process

The distance between catalytic sites (Ni) and sorbents (CaO) on the performance of integrated CO2 capture and utilization (ICCU) process is crucial important because the sorbents demonstrate a dramatic volume increase during carbonation reaction (1st stage of ICCU) and sequentially cover the catalytic sites and retard the CO2 conversion (2nd stage of ICCU). Herein, we synthesized various Ni/CaO-based dual functional materials (DFMs) with different distances between active sites and sorbents to provide different volume spaces for the growth of CaCO3 during the carbonation reaction. It is found that both 1%NiCaO and 10%NiCaO synthesized by a one-pot method exhibited a low CO2 conversion (38% and 45%, respectively) and CH4 selectivity (58% and 69%, respectively) as the distance between catalytic sites and sorbents was so close that the Ni active sites were covered by the formed CaCO3 during carbonation reaction. With the increase of the distance by physical mixing method, the CO2 conversion and CH4 selectivity of 1%Ni/CeO2-CaO-phy were largely increased to 62% and 84%, respectively at 550 °C and atmospheric pressure when captured CO2 from 15% CO2/N2. This is attributed to the fact that the Ni active sites were still well dispersed on the surface of CeO2 nanorods instead of being covered by the newly formed CaCO3.