锰—铈复合氧化物催化剂表面氧的性质

氧化锰催化剂广泛用于一氧化碳常温氧化及汽车尾气的净化等,CeO_2是氧化物催化剂的优良助剂。非贵金属催化剂中添加CeO_2能提高催化剂的氧化活性已有很多报道,但有关Ce对氧化锰结构及表面氧脱附性能影响的研究尚不多见。本文运用XRD、DTA和TPD-MS等手段对共沉淀法制得的Mn-Ce复合氧化物进行了物相结构和脱氧活性研究。

The Properties of the Surface Oxygen on Manganese-Cerium Composite Oxide

In the paper, the manganese-cerium composite oxide catalysts were prepared by copreeipita-tion. The crystal structure of the catalysts and the desorptlon properties of surface oxygen on the catalysts were investigated by using the methods of TPD-MS and XRD. There are three peaks in the TPD-MS oxygen spectra of Mn2Oa and Mn2O3-CeO2 catalysts. The first two peaks are attributed to the absorbed oxygen and the last one is ascribed to the lattice oxygen, the desorption of which might take place according to the following reaction:The activation energy of desorption oxygen for Mn2O3 is. 115 kJ/mol(peak I ), 204 kJ/mol (peak I ), and for Mn2O3-CeO2 is; 43. 2 kJ/moKpeak I ), 178 kJ/moKpeak I ). Due to the presence of cerium, the amount of surface absorbed oxygen increase evidently, that can reach about 57 times. On the basis of the thermal analysis, the products formed of sample (Mn-O, Mn-Ce-O) at various temperatures were characterized by XRD. consequently thermal decomposition reaction may be shown as the following schemes: