甲烷无氧芳构化催化剂的X光电子能谱分析

The XPS Analysis on Different Roasting Temperature Catalyst in Methane Aromatization

通过对甲烷无氧芳构化反应不同焙烧温度催化剂进行X光电子能谱分析 ,发现 6 0 0℃焙烧温度 ,催化剂中Mo(3d5 )的结合能较 40 0℃和 70 0℃高 ,同时Mo的相对含量较高 .在活性评价中 ,6 0 0℃焙烧的催化剂活性最好 ,说明了高价钼氧化物是催化剂活性物种的初始形态 ;同时发现高温焙烧 (高于 6 0 0℃ )引起分子筛骨架脱铝 ,焙烧温度达 70 0℃时 ,骨架脱铝变得严重 ,引起催化剂酸性下降 ,导致催化剂活性下降 ,而Si元素在 70 0℃以下焙烧时相对稳定 ,分子筛基本骨架结构没有被破坏 .

Through the XPS analysis on different roasting temperature catalyst in methane aromatization under non-oxygen condition, we found that the catalyst roasting at 600 ℃ had higher combined energy and quantity than catalystroasting at 400 ℃ and 700 ℃, That is why catalyst roasting at 600 ℃ had higher activity in active-measuring experiments than the other two. It is also demonstrated that the main first-shape active components in catalyst are molybdenum oxide.Through Al element XPS analysis, we found that high temperature roasting could lead to part of Al run off from molecular sieve skeleton. This turned down the acidity of catalyst and made the activity of catalyst turned down. We also found below 700 ℃ the Si element was steady, the structure of molecular sieve skeleton hasn't been devoiced.