摘要
制备了一系列Ｖ、Ａｇ、Ｎｉ原子比不同的三元氧化物，应用ＴＰＤ－ＭＳ技术研究了样品表面氧的性质，并测定了甲苯选择性氧化生成苯甲醛的催化活性．实验结果表明，样品表面存在有多种吸附的氧物种．在脱附温度＜９００℃：当Ｎｉ含量对Ａｇ（或Ｖ）的原子比为０．２５或０．５０时，仅在低温处出现有表面的Ｏ－和Ｏ２－两种氧物种的脱附峰；当Ｎｉ含量对Ａｇ（或Ｖ）的原子比增高到＞０．７５时，除有表面的Ｏ－和Ｏ２－两种氧物种的脱氧峰外，还有由于样品中的物相转变所生成的有晶格氧（Ｏ２－）参与脱附的脱氧峰．随着Ｖ－Ａｇ中Ｎｉ含量的改变，脱氧峰的脱附活化能Ｅｄ值也发生变化，３＃样品（Ｖ：Ａｇ：Ｎｉ＝１：１：０．７５）的Ｅｄ值最低，生成苯甲醛的选择性也最高．因此，样品的Ｅｄ值与生成苯甲醛的选择性之间存在着顺变关系．
A series of V-Ag-Ni trioxides with various atomic ratios of V, Ag and Ni were prepared.The catalytic activities for the selective oxidation of toluene to benzaldehyde were obtained, and the natures of oxygen species on the surfaces of these samples were studies by using temperature programmed desorption-mass spectrography(TPD-MS). The results showed that the oxygen species of multiple adsorption existed on the sample surface. And in the range of desorption temperature <900℃: for the samples in which the content of nickel versus Ag (or V) with atomic ratio equaled 0.25(or 0.50), the desorption peaks of the SPecies of surface O- and O2- appeared near the lower temperatures; for the samples in which the atomic ratio of nickel versus Ag (or V) was increased to a value of 0.75, not only the desorption peaks of O- and O2- species on surfaces of samples occurred, but also the O2- spedes of lattice appeared due to the phase transformations in the samples. As the content of Ni in V-Ag oxide was changed. the activation energy of oxygen desorption (Ed)also changed. The Ed value of 3# sample (V: Ag : Ni = 1: 1: 0.75) is the lowest, the selectivity of benzaldehyde in toluene oxidation is the highest. Thus, a parallel relation between the Ed value and the selectivity for benzaldehyde existed in these V-Ag-Ni oxides.
出处
《无机化学学报》
SCIE
CAS
CSCD
北大核心
1994年第2期194-198,共5页
Chinese Journal of Inorganic Chemistry
基金
中国科学院基金
南京大学现代分析中心测试基金
关键词
钒-银-镍
氧化物
选择性氧化
甲苯
V-Ag-Ni oxide selective oxidation of toluene natures of oxygen species of surface
