Microemulsion-derived, nanostructured CaO/CuO composites with controllable particle grain size to enhance cyclic CO2 capture performance for combined Ca/Cu looping process

Combined Ca/Cu looping process is a very most promising CO2 capture technology, in which chemical looping combustion provides the heat for calcining CaCO3 in calcium looping by employing CaO/CuO composites. However, such CaO/CuO composites demonstrated a fast decay in CO2 uptake capacity during cyclic operation. In order to solve this problem, nanostructured CaO/CuO composites was synthesized using a microemulsion method in this work. The synthetic parameters, including the mole ratio of water to surfactant and mole concentration of precursors, were investigated systematically for the microemulsion system. A fixed-bed reactor was used to assess the redox characteristics and CO2 capture performance. The results showed that the particle grain size of the nanostructured CaO/CuO composites can be controlled by the variation of the mole ratio of water to surfactant. With the increase in the mole ratio of water to surfactant from 9 to 23, the mean particle grain size of the CaO/CuO composites increased from 0.19 to 0.57 mu m. A high mole concentration of precursors also resulted in a much enhanced CO2 capture performance. Compared to the successive fast CO2 uptake decay for the reference CaO/CuO composites developed by a conventional co-precipitation method, the CaO/CuO composites fabricated by the microemulsion method demonstrated an increasing CO2 uptake in the initial cycles followed by a relatively slow decline in the subsequent cycles, exceeding uptake of the reference material by 104% after 19 cycles. The kinetic analysis showed that the CaO/CuO composites fabricated by the microemulsion method had much lower activation energy than the reference material.