One-step synthesis of CaO/CuO composite pellets for enhanced CO2 capture performance in a combined Ca/Cu looping process via a facile gel-casting technique

Abstract

The combined Ca/Cu looping process is a promising CO2 capture technology, in which the exothermic reduction of CuO with reducing gas (e.g., CH4, H2, or CO) is used in situ to supply the heat required to calcine CaCO3 via CaO/CuO composites. Although possessing excellent redox characteristics, CaO/CuO composites suffer from severe deactivation in their CO2 capture performance during cyclic operation. Besides, developing CaO/CuO composite pellets is essential for the practical applications of the combined Ca/Cu looping process. Thus in this work, we proposed a facile gel-casting technique to achieve a one-step synthesis of CaO/CuO composite pellets with enhanced CO2 capture performance. The results show that CaO/CuO composite pellets with homogeneous elemental distribution and a molar ratio of Ca to Cu of one can be obtained by adjusting the immersion time (∼24 – 48 h) and the molar ratio of Ca to Cu (∼2) in the mixed precursor solution during the material synthesis process. The CaO/CuO composite pellets had an initial CO2 uptake capacity of 0.16 gCO2/gmaterial and a final CO2 uptake capacity of 0.10 gCO2/gmaterial after ten repeated cycles. With the addition of glucose as the pore-forming material, sintering was reduced and the modified CaO/CuO composite pellets showed a much improved CO2 capture performance. With the optimal addition amount of glucose (i.e., a mass ratio of glucose to sodium alginate of two), the best-performing modified CaO/CuO composite pellets had a final CO2 uptake capacity of 0.14 gCO2/gmaterial after ten repeated cycles, exceeding that of the unmodified counterpart by 40%. Furthermore, the mechanism of structural improvement of CaO/CuO composite pellets by adding glucose was elucidated.