NaBr-Enhanced CaO-Based Sorbents with a Macropore-Stabilized Microstructure for CO2 Capture

Calcium looping process (CaLP) is well-considered as a cost-effective scenario for trapping CO2 from flue gas. However, the CO2 capture capacity of natural CaO-based sorbents spoils rapidly over long-term cycles. In this work, NaBr was introduced to enhance the cyclic CO2 capture capacity of CaO sorbents. The NaBr-modified CaO showed an improved activity and durability for carbonation. After 100 cycles, the NaBr/CaO-10/100 maintained a capacity of 0.202 g CO2/g sorbent, which was about 185% higher than that of unmodified CaCO3 precursor. The mechanism of enhancement was analyzed by a simultaneous thermal analyzer (STA), in situ X-ray powder diffraction (in situ XRD) instrumentation, an inductively coupled plasma optical emission spectrometer (ICP-OES), a field emission scanning electron microscope coupled energy dispersive X-ray spectrometer (FSEM-EDS), and N-2 physical absorption analysis, and the results showed that the modified sorbent formed a well-linked macropore structure, which was relatively stable at high temperature reactions; additionally, NaBr incorporated inside the CaO crystal lattice promoted the durability of pore structures and cyclic CO2 capture capacity. NaBr is an effective promoter that has the ability of enhancing the cyclic CO2 capture capacity of CaO-based sorbents.