A. series of the MoO3/-gamma-Al2O3 samples is prepared by mechanically mixing MoO3 with gamma-Al2O3 powder. The solid state dispersion of the MoO3 in to the porous gamma-Al2O3 is studied by SEM, XRD, XPS, TG/DTA, and positron annihilation spectroscopy. The positron annihilation lifetime spectra of the MoO3/-gamma-Al2O3 are measured as a function of the mass ratio of MoO3 heating temperature, heating time and in a way that the MoO3 is loaded gradually, separately. The experimental results show the process of the thermal dispersion of the MoO3 into the gamma-Al2O3 support. It is shown that the MoO3 disperses into the outer surface first, and then into the secondary pores and the micro pores. The gradual Loading can make MoO3 effectively dispersed into gamma-Al2O3. Grinding can also affecte the thermal dispersion process.
A series of the MoO3/γ-Al2O3 samples is prepared by mechanically mixing MoO3 with γ-Al2O3 powder. The solid state dispersion of the MoO3 in to the porous γ-Al2O3 is studied by SEM, XRD, XPS, TG/DTA, and positron annihilation spectroscopy. The positron annihilation lifetime spectra of the MoO3/γ-Al2O3 are measured as a function of the mass ratio of MoO3, heating temperature, heating time and in a way that the MoO3 is loaded gradually, separately. The experimental results show the process of the thermal dispersion of the MoO3 into the γ-Al2O3 support. It is shown that the MoO3 disperses into the outer surface first, and then into the secondary pores and the micro pores. The gradual Loading can make MoO3 effectively dispersed into γ-Al2O3. Grinding can also affecte the thermal dispersion process.
以浸渍法将不同浓度的钼酸铵水溶液加载于多孔γ-Al2O3,中,再经不同温度烘烤后制得Mo/γ-Al2O3样品.用热分析、XPS以及正电子湮没谱学对样品进行测试.实验表明浸渍法可使Mo均匀地分散在样品表面,当烘烤温度达到350.C后,Mo主要以取代氧化铝表面羟基中氢的方式与载体γ-Al2O3,发生相互作用,并以化学吸附的方式将钼离子固定于γ-Al2O3二次孔中.
用浸渍法制备了一系列不同担载量的负载型镍催化剂,并经不同温度下烘烤1小时后得到Ni/γ-Al2O3样品.分别用热分析(DTA/TG)、正电子湮没谱学等方法来表征镍在多孔氧化铝(γ-Al2O3)表面的分散特性.实验表明,在浸渍法制得的样品中,镍均匀分散于载体表面,在烘烤温度达到320℃时获得活性;在更高的烘烤温度下镍会向体内中扩散,使有效活性减少.
用浸渍法和干混法制备了一系列不同担载量、经不同烘烤温度及不同时间烘烤后的多孔氧化铝上担载氧化钨的样品(WO3/γ-Al2O3)，分别用正电子湮没谱学、X射线衍射(XRD)、热分析(TG/DTA)、光电子能谱(XPS)、扫描电子显微镜(SEM)等方法来表征W在γ-Al2O3表面的分散过程。实验揭示了W离子在多孔γ-Al2O3中的微观扩散机理。结果表明，在干混法样品中只有微量W能分散，其中碾磨对分散起着重要的作用；而在浸渍法样品中，W离子先进入二次孔表面的活性中心，高于10%后以单层分散于非活性表面上，最大单层分散量为18.5%(以WO3质量分数计)，400℃以上的烘烤才能使W与载体发生相互作用，1h的烘烤已足够使钨离子分散。
