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研究了Fe_2O_3和Sb_2O_4及Sb/Fe比由1/9至9/1五种复合氧化物表面氧的TPD行为。Fe_2O_3在200～450℃间有少量氧脱出,Sb_2O_4在700℃以后出现脱氧峰,而Sb/Fe复合氧化物则出现所谓α和β脱氧峰。随Sb/Fe比增加α氧的脱附活化能也增高,Sb/Fe比为3/7、5/5和7/3时分别为33、36、51kcal/mol。Fe-Sb氧化物中α氧比β氧对烯烃氧化具有更高的活性。在50—275℃范围内NH_3在Fe-Sb氧化物上的吸附等温线符合Freundlich式,同时由NH_3的TPD可明显看出Fe-Sb氧化物具有不同强度的吸附中心,它们与所含表面氧有关,但表面氧对NH_3的氧化是很弱的。讨论了烯烃选择氧化反应与表面氧强度之间的联系。
The TPD behavior of oxygen on the surface of five composite oxides containing 1/9 to 9/1 of Fe 2 O 3, Sb 2 O 4 and Sb / Fe was studied. Fe_2O_3 has a small amount of oxygen at 200-450 ℃, Sb_2O_4 deoxidizes at 700 ℃, and Sb / Fe composite oxides show so-called α and β deoxidation peaks. As the Sb / Fe ratio increased, the activation energy of desorption of α-oxygen also increased. When the Sb / Fe ratios were 3/7, 5/5 and 7/3, they were 33, 36 and 51 kcal / mol, respectively. Α-Oxygen in Fe-Sb oxides has a higher activity for olefin oxidation than β-Oxygen. The adsorption isotherm of NH_3 on Fe-Sb oxide in the range of 50-275 ℃ accords with the Freundlich equation, and the TPD of NH_3 can clearly show that Fe-Sb oxides have different intensity of adsorption centers, However, surface oxygen oxidation of NH_3 is very weak. The relationship between the selective oxidation of olefins and the surface oxygen strength is discussed.