摘要
研究了MoPO/SiO2 催化剂对丙烷选择氧化制丙烯醛的催化性能 .MoO/SiO2 催化剂主要表现出对丙烷氧化脱氢的催化性能 ,在该催化剂中添加磷后 ,丙烷转化率和选择氧化产物丙烯醛的选择性明显提高 .催化剂的X射线衍射、拉曼光谱、程序升温还原、吡啶吸附红外光谱和程序升温脱附等表征结果表明 ,MoO/SiO2 催化剂主要含有MoO3 晶相 ,添加磷后 ,形成了表面多钼酸物种 ,磷以PO4四面体结构存在于表面 ,可能形成部分Mo—O—P键 ,从而抑制了MoO3 在MoPO/SiO2 上的形成 ,起到分隔活性中心的作用 .在MoO/SiO2 催化剂中添加磷后 ,催化剂的B酸和L酸酸性均增强 ,有利于丙烷在MoPO/SiO2 催化剂表面活性的提高 .由此可见 ,催化剂表面结构和酸性的变化可能是导致MoPO/SiO2
The selective oxidation of propane to acrolein over the MoPO/SiO 2 catalyst has been studied. MoO/SiO 2 exhibits only activity for the oxidative dehydrogenation of propane to propene. The propane conversion and acrolein selectivity are evidently increased by the addition of P to MoO/SiO 2. The catalysts were characterized by XRD, Raman spectroscopy, H 2 TPR, NH 3 TPD and FT IR spectroscopy. The XRD and Raman results show that crystalline MoO 3 is dominant on the silica supported molybdenum oxide catalyst, while polymolybdate species are present on P doped catalysts. Compared to the P-O-P stretching vibration at 905 cm -1 in PO/SiO 2, the P doped sample exhibits the Raman band of the asymmetric PO 4 stretching mode at 1?085 cm -1 . Therefore, Mo-O-P bonds are likely to be formed on the P doped catalyst, and the active sites are isolated by the phosphorus in MoPO/SiO 2, preventing the growth of crystallized MoO 3. These changes in structure and thus the improvement in reducibility of the MoPO/SiO 2 catalyst may be responsible for the increase in propane conversion and acrolein selectivity. Furthermore, the results of FT IR spectroscopy of pyridine adsorption and NH 3 TPD show that both Brnsted and Lewis acid sites on the surface of the P doped sample are stronger than those on MoO/SiO 2. These suggest that the addition of phosphorus modifies the surface structure and enhances the surface acidity of the supported catalyst, thus improving the behavior of the catalyst.
出处
《催化学报》
SCIE
CAS
CSCD
北大核心
2003年第10期769-774,共6页
基金
国家重点基础研究发展规划项目 (G19990 2 2 40 8)
关键词
丙烷
选择氧化
丙烯醛
氧化钼
氧化磷
负载型催化剂
二氧化硅
propane, selective oxidation, acrolein, molybdenum oxide, phosphorus oxide, supported catalyst, silica
