In order to understand how the modification of limestone by propionic acid affects the CO2 capture performance, limestone was modified with propionic acid in this study. A thermo-gravimetric analyzer and a dual fixed-bed reactor were employed to investigate the CO2 capture capacity of the modified limestone during cyclic calcination/carbonation reactions. The microstructure of the calcined modified limestone was examined by SEM and nitrogen physisorption tests. The results show that the modified limestone achieves faster carbonation rates and higher carbonation conversions than the untreated one during cyclic reactions. The carbonation conversion of the modified limestone is 0.31 after 100 cycles. 3.9 times as the carbonation conversion of the untreated one. The surface areas of the calcined modified limestone are higher than that of the calcined untreated one after the same cycles. For the calcined modified limestone, the pores distributed in 2-20 nm are more abundant than the untreated one, which contribute plenty of surface area for carbonation reactions. Therefore, the modified limestone can achieve higher carbonation conversions than the untreated one during cyclic reactions. (c) 2012 Elsevier B.V. All rights reserved.