酸性条件下钛硅分子筛的失活及重排补钛复活研究

对空心钛硅分子筛(HTS)在酸性条件下的催速失活及重排补钛复活过程进行了研究。采用X射线衍射光谱、X射线荧光光谱、电感耦合等离子发射光谱、傅里叶变换红外光谱、紫外-激光拉曼光谱、X射线光电子能谱、²⁹Si固体魔角旋转核磁共振、透射电镜等方法对新鲜剂、模拟催速失活样品及重排补钛复合样品进行表征后发现:催速失活过程中分子筛的骨架Si—O—Ti键水解,四配位钛转化为六配位非骨架钛并且流失,导致其催化性能显著降低;在重排补钛复活过程中,一部分钛插入到骨架空位中产生新的活性中心,使得催化剂性能恢复到接近新鲜剂的水平,用于催化氯丙烯氯醇化反应时,氯丙烯转化率达到99.1%,二氯丙醇选择性达到99.0%,二氯丙醇质量分数达到26.1%;另一部分引入的钛形成了锐钛矿物种。

DEACTIVATION OF TITANIUM SILICALLITE UNDER ACID CONDITION AND ITS REACTIVATION BY RECRYSTALLIZATION WITH THE EXISTENCE OF Ti SPECIES

The accelerated deactivation of hollow titanium silicalite (HTS) under acid conditions and its reactivation by recrystallization with the existence of Ti source was studied. The samples were characterized by XRD, XRF, ICP-OES, FT-IR, UV-Raman, XPS, 29Si MAS NMR and TEM. The results show that the framework Si—O—Ti bond is hydrolyzed during the deactivation process, and the 4-coordinated Ti is converted into to 6-coordinated Ti and lost, which lead to a significant decrease of its catalytic performance. During the rearrangement and replacement of titanium, a part of Ti is inserted into the framework vacant site and generates new active center, which makes the catalytic performance return to the level of the fresh HTS zeolite, and the conversion of allyl chloride, the selecltiviety and the mass fraction of dichloropropanol reach to 99.1%, 99.0% and 26.1%, respectively; the other part of introduced Ti is converted into anatase species.