Perovskite-like oxides La
2CuO
4 and LaSrCuO
4, prepared by the citrate combustion method, werestudied and used as catalysts for CO oxidation, NO decomposition, and NO + CO reduction.The adsorption and desorption behaviors of the gases on catalyst surfaces were well characterizedby mass spectrometric-temperature programmed desorption (MS-TPD) measurements. A largeNO desorption peak was observed on LaSrCuO
4, but only a small one was observed on La
2CuO
4,suggesting that the Sr addition or the existence of an oxygen vacancy is the necessary conditionfor NO adsorption. No CO desorption peak was observed on either LaSrCuO
4 or La
2CuO
4,suggesting that the adsorbed CO was totally oxidized to CO
2 before elution. The appearance ofN
2 desorption peak in the NO MS-TPD spectra of LaSrCuO
4 (
T = 400
C) indicated that NOdissociation occurs easily and the crucial step of NO decomposition is O
2 desorption. The activityof LaSrCuO
4 was low for NO decomposition (34.3%,
T = 850
C), but high for CO oxidation(99%,
T = 300
C) and for NO + CO reduction (98.7%,
T = 600
C), suggesting that the desorptionof oxygen, or the regeneration of active site, is difficult in NO decomposition but easy in COoxidation and NO + CO reduction, due to the existence of CO. Finally, the mechanism of NO +CO reduction was investigated according to the ratio
XNO/
XCO; the variation of the ratio
XNO/
XCO suggests that the NO + CO reduction has different mechanisms over different catalystsand at different temperatures.