摘要
采用氧化态Mo/γ Al2 O3 与NH3 的程序升温反应 (TPR)制备了不同Mo担载量的氮化态Mo/γ Al2 O3 催化剂 ,用XRD和EXAFS方法分别研究了样品在氮化前后的体相结构及Mo原子局域配位结构 .结果表明 ,在氮化前样品的MoK边径向结构函数与非负载MoO3 类似 ,样品中Mo以高分散的MoO3 形式存在 ;氮化后样品的径向结构函数与非负载的γ Mo2 N基本相同 ,只是峰强度有所降低 ,表明样品中Mo主要以分散度较高的γ Mo2 N形式存在 ,并且随担载量降低 ,γ Mo2 N的分散度更高 .
Nitrided Mo/Al 2O 3 catalysts were prepared by temperature programmed reaction between NH 3 and MoO 3/Al 2O 3. XRD and EXAFS mothods were used for the structural characterization. The results of XRD show that the molybdate in the supported samples exists as dispersed MoO 3 and γ Mo 2N before and after nitriding, respectively. The small coordination numbers of Mo N shells indicate that the γ Mo 2N in the supported samples possesses high dispersion, the lower loading of Mo, the higher dispersion of γ Mo 2N on alumina. From the view of coordination distance, it is found that with the increase of dispersion of γ Mo 2N, the Mo N distance is a little shortened, which may have resulted from the nano shortening phenomenum. γ Mo 2N phase in the supported samples has high dispersion.
基金
国家自然科学基金资助项目 ( 2 9873 0 4 4)
关键词
催化剂
制备
结构表征
EXAFS
Mo 2N/Al 2O 3 catalysts
preparation
structural characterization
EXAFS
