Efficient NO reduction by CO on Cu/Ce co-modified CaO in calcium looping CO2 capture process

Abstract

In the calcium looping CO2 capture process, using CO in the flue gas to reduce NO at a high molar ratio of CO to NO (e.g., above 10:1) can achieve efficient removal of NO. However, the lots of unreacted CO causes secondary pollution. In this study, a novel Cu/Ce co-modified CaO was proposed for cyclic CO2 capture and the catalytic NO reduction at a low CO:NO molar ratio (e.g., 2:1). The experimental findings indicate that Cu/Ce modification improves the performance of CaO in both catalytic NO reduction and carbonation. The Cu/Ce co-modified CaO contained the optimal Cu/Ce/Ca molar ratio of 1:5:100 possesses both NO removal and CO conversion efficiencies of above 99 %, along with CO2 removal efficiency exceeding 88%. Microscopic analysis determines that the electron transfer between Cu and Ce facilitates the conversion of lattice oxygen into surface oxygen, mitigating the competition between CO2 and CO for surface oxygen. Furthermore, density functional theory calculations demonstrate that CO/NO/CO2 exhibits non-competitive adsorption behavior on Cu/Ce co-modified CaO. Consequently, Cu/Ce-modified CaO possesses superior catalysis for efficient NO reduction by CO at low CO:NO molar ratio in calcium looping process.