Titanium Catalysts Supported on Silica. X-ray Absorption Investigation on Their Structures and Comparison of Their Catalytic Activities in Diels−Alder and Epoxidation Reactions
Titanium Catalysts Supported on Silica. X-ray Absorption Investigation on Their Structures and Comparison of Their Catalytic Activities in Diels−Alder and Epoxidation Reactions
复制标题
二氧化硅负载钛催化剂的 X 射线吸收研究及其在 Diels-Alder 和环氧化反应中的催化活性
DOI：
10.1021/jp961487u
复制
发表时间：
1996
期刊：
影响因子：
--
通讯作者：
M. C. Sánchez
中科院分区：
文献类型：
--
作者：
J. Fraile;Joaquín García;J. Mayoral;A. Proietti;M. C. Sánchez
通过X射线吸收光谱（XAS）研究了由不同助剂制备的不同硅钛负载型催化剂的催化活性与局部结构之间的相关性。用TiCl 4处理二氧化硅产生了Diels−桤木环加成和用TBHP环氧化环己烯的非常活性的催化剂，但在后一反应中的选择性不是很高。用Ti（OiPr）4处理二氧化硅得到的固体在环氧化反应中非常活跃，但在Diels−桤木中不活跃。通过用TiCl 2（OiPr）2处理二氧化硅获得的催化剂在两个反应中显示出中等催化活性，尽管它在环氧化中比在Diels−桤木中更好。XAS结果显示了Ti环境以及因此固体的催化活性如何取决于用作前体的Ti化合物。在Ti（OiPr）4的情况下，钛与四个氧键合，而当使用TiCl 4时，氯存在于第一配位球中。该催化剂是由...
The correlation between the catalytic activity and the local structure of different silica−titanium supported catalysts prepared from different promoters was studied by means of X-ray absorption spectroscopy (XAS). The treatment of silica with TiCl4 gives rise to a very active catalyst of Diels−Alder cycloaddition and epoxidation of cyclohexene with TBHP, but the selectivity in the latter reaction is not very high. The solid obtained by treatment of silica with Ti(OiPr)4 is very active in epoxidation but not in Diels−Alder. The catalyst obtained by treatment of silica with TiCl2(OiPr)2 displays an intermediate catalytic activity in both reactions, although it is better in epoxidation than in Diels−Alder. The XAS results show how the Ti environment, and hence the catalytic activity of the solid, depends on the Ti compound used as the precursor. Titanium is bonded to four oxygens in the case of Ti(OiPr)4, while chlorine is present in the first coordination sphere when TiCl4 is used. The catalyst prepared fr...