Stabilizer-coated combined Ca/Cu pellets with controllable particle sizes for the Ca/Cu chemical loop

•A two-step synthesis approach was proposed for synthesizing stabilizer-coated combined Ca/Cu pellets.•The application of a stabilizer layer effectively enhanced the cyclic CO2 sorption stability of the combined Ca/Cu pellets.•Y2O3 was more effective than MgO and Al2O3 in enhancing the cyclic CO2 sorption performance of combined Ca/Cu pellets. The fabrication of high-performance combined Ca/Cu pellets is crucial for advancing the Ca/Cu chemical loop, wherein the reduction of CuO facilitates the required heat for CaCO3 decomposition. However, the CO2 sorption performance of combined Ca/Cu pellets experiences a swift deterioration, presenting a notable obstacle. Herein we reported a two-step synthesis approach to prepare stabilizer-coated combined Ca/Cu pellets with controllable particle sizes. To begin, combined Ca/Cu pellets were prepared, which had varying particle size ranges (ranging from 120 to 390 μm, 230 to 480 μm, 330 to 670 μm, and 600 to 980 μm). In the first cycle, the particle sizes of these pellets decreased, leading to an increase in their CO2 sorption capacity from 0.169 to 0.208 gCO2/gsorbent. Nevertheless, all combined Ca/Cu pellets exhibited a decrease in their ability to absorb CO2 during ten cycles, leading to a reduction of around 35 % in their initial CO2 sorption performance. Afterward, diverse stabilizer layers (Al2O3, MgO, or Y2O3, with a corresponding mass ratio of 7.5 wt%, respectively) were applied to the combined Ca/Cu pellets. The combined Ca/Cu pellets coated with Y2O3 exhibited superior performance in capturing CO2 compared to the counterparts coated with Al2O3 or MgO. After 30 cycles, Y2O3-coated combined Ca/Cu pellets, containing ∼ 12.5 wt% Y2O3, exhibited a CO2 sorption capacity of 0.145 gCO2/gsorbent, retaining 45.0 % of its initial CO2 sorption performance.