The role of SO2 in the reduction of NO by CO on La2O2S

The decomposition of NO and the reduction of NO by CO on La2O2S were studied using temperature-programmed reaction technique coupled with fast mass spectrometry, powder X-ray diffraction and X-ray photoelectron spectroscopy. The role of SO2 plays in the reduction is explored. It is found that the decomposition of NO is a favorable reaction step for the reduction of NO by CO achieved through a sulfur-assisted path. The oxygen produced in the decomposition is removed by the sulfur in the oxysulfide as SO2, which in turn is reduced back to sulfur by CO on La2O2S. An external supply of sulfur, such as SO2, in the feed is needed to maintain the population of sulfur in the oxysulfide and thus make the reduction sustainable.