Experimental Study on High-Efficiency Cyclic CO2 Capture from Marine Exhaust by Transition-Metal-Modified CaO/Y2O3 Adsorbent

CaO-based adsorbent cycling carbon capture technology is an effective way to reduce CO2 emissions from marine exhaust gases. Metal-modified CaO-based adsorbents represent one of the important ways to improve the cyclic CO2 capture capacity. In order to obtain economical and efficient CaO-based adsorbents, transition metal (Cu, Fe, Co, Cr, Ni)-modified CaO/Y2O3 adsorbents were prepared using the sol-gel method. CO2 cyclic adsorption capacity tests were carried out in a fixed bed. The microstructure of the adsorbents was analyzed using XRD, SEM, and BET. The adsorption performance and cycle stability of the modified CaO/Y2O3 adsorbents were investigated in depth. The results show that the Fe-CaY adsorbent had the best adsorption performance. The initial adsorption capacity of Fe-CaY was 0.62 g/g at 650 degrees C, and the adsorption capacity was 0.59 g/g at the 25th cycle. Fe-CaY-doped samples with the largest pore size and specific surface area showed the best adsorption performance due to the contribution of macropores in the prevention of sintering. Fe doping can greatly improve the CO2 adsorption capacity and cycle stability of an adsorbent and also reduce the CaO-based adsorbent cycle temperature. In addition, the Fe-Ni-CaY adsorbent had the best adsorption performance among the bimetallic (Cu-Ni, Fe-Ni, Co-Ni, Cr-Ni)-modified CaO/Y2O3 adsorbents. However, compared with Fe-CaY, the adsorption capacity decreased. The reason for this might have been that the addition of Ni destroyed the rich pore structure between Fe-Ca-Y and the stability of the adsorbent particle structure, which led to the aggregation of CaO crystals and reduced the CO2 adsorption capacity. Therefore, the Fe-CaY developed in this study has excellent adsorption capacity and cyclic stability, which makes it a promising adsorbent for CO2 capture in marine exhaust gases.