还原温度对超细K-Co-Mo合成低碳醇催化剂结构的影响  

Effect of Reduced Temperature on the Structure of Ultra-fine K-Co-Mo Catalyst Used in Mixed Alcohol Synthesis

作　　者：孙中海[1] 伏义路[1] 鲍骏[1] 

机构地区：[1]中国科学技术大学化学物理系,安徽合肥230026

出　　处：《分子催化》2004年第6期430-435,共6页Journal of Molecular Catalysis(China)

摘　　要：采用XRD及XPS技术研究了合成低碳醇反应中还原温度对还原态超细K-Co-Mo催化剂结构的影响.分别考察未还原及不同的还原温度下K、Co和Mo活性物种的价态以及相对含量的变化.结果表明:表面上Mo主要以+4和+6两种价态存在.随还原温度的升高,表面上Mo4+/Mo6+比增大,较高的Mo4+/Mo6+比有利于形成合成醇反应中活性位.Co也是以+2和金属态两种价态存在.还原温度低于500℃时,表面上Co2+的相对含量变化不大,但是在体相中可以检测到有金属Co形成,且随还原温度的升高而增多.当还原温度为550℃时,表面上的Co2+迅速减少,这种表面上的Co2+的迅速减少可能导致了合成醇活性的迅速降低.K+在还原温度低于500℃时相对含量没有明显变化,经550℃还原后,K+在表面明显富集.An ultra-fine K-Co-Mo catalyst at different reduction temperature used in mixed alcohols synthesis was characterized by XRD and XPS. The valence and relative content of the active species (K、 Co、 Mo) in this catalyst at different reduction temperature were investigated. The results indicate that the main valence of Mo is +4 and +6. The relative content of Mo^(4+) increases and the relative content of Mo^(6+) decreases when the reduction temperature is raised. The Co exists as Co^(2+) and metal. When the reduction temperature is less than 500 ℃, the relative content of Co^(2+) in the surface is almost constant; but at the inner of the catalyst, the metal Co is formed and becomes more when the reduction temperature is raised. When the reduction temperature is raised to 550 ℃, the content of Co^(2+) in the surface decreases remarkably. It is possible that this decrease of Co^(2+) in the surface leads to the decrease in mixed alcohols synthesis activity. When the reduction temperature is less than 500 ℃, the content of K^+ in the surface is almost the same too, but when the reduction temperature is raised to 550 ℃, the K^+ is enriched remarkably in the surface. The higher Mo^(4+)/ Mo^(6+) is favorable to engender active site in mixed alcohol synthesis, and Co^(2+) is a very important factor that can affect the activity of the mixed alcohols synthesis.

关 键 词：还原温度 超细K-Co-Mo催化剂 低碳醇合成 XPS 

分 类 号：O643.32[理学—物理化学]