【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 催化性能提高的原因更多还原

【Abstract】 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 Brnsted 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.更多还原