Removing NOx, CO and HC from automobile exhaust based on chemical looping combustion

Background To meet more stringent automobile exhaust emission standards without using platinum group metal three-way catalysts (TWCs), two nonprecious metal oxide oxygen carriers, Cu10/Al90 and Ni10/Al90, were investigated for the simultaneous and thorough removal of nitrogen oxides (NOx), carbon monoxide (CO) and hydrocarbons (HC) from automobile exhaust. Results In oxidation reactions of the reductive oxygen carriers with NO, the reductive oxygen carriers were converted to the oxidative oxygen carriers and NO was simultaneously reduced to N-2. Then, the oxidative oxygen carriers were regenerated to the reductive oxygen carriers with reducing gases, including CO, H-2 and HC. At the same time, CO was converted to CO2, H-2 was converted to H2O, and HC was converted to CO2 and H2O. The simultaneous removal of NOx, CO and HC could be achieved based on a chemical looping combustion mechanism. Compared with Ni10/Al90, Cu10/Al90 exhibited better performance for removing NO, CO and C3H6 from simulated automobile exhaust. However, the reductive Ni10/Al90 had an excellent steam reforming catalytic activity and was capable of converting residual C3H6 in the exhaust to harmless H-2 and CO2. Conclusion Based on these findings, a novel chemical looping combustion process is proposed, in which the first oxygen carrier-filling layer based on Cu10/Al90 removed NOx, CO and HC simultaneously, and the second oxygen carrier-filling layer based on Ni10/Al90 removed residual NO and C3H6. (c) 2019 Society of Chemical Industry