Ti-MWW分子筛钛活性中心结构调控及其在乙烯氧化水合制乙二醇反应中的应用

与传统乙二醇生产工艺相比，钛硅分子筛催化乙烯和过氧化氢一步法氧化水合制乙二醇具有工艺流程短且反应条件温和的显著优点，但低的催化性能导致过氧化氢有效利用率低。钛活性中心结构是影响钛硅分子筛催化性能的关键因素，因此研究钛活性中心结构调控对于设计高效的乙烯氧化水合催化剂具有重要意义。本项目基于代表性钛硅分子筛Ti-MWW分子筛的晶化特点，在其合成体系中引入烷基修饰的含钛化合物并调控其浓度，获得烷基修饰的骨架钛物种。经焙烧将烷基转变为羟基后可以获得Ti(OSi)3OH活性中心，从而有效调控钛活性中心结构。本项目的实施，旨在构建高性能的钛活性中心，实现过氧化氢的高效活化和活性氧的有效传递，并阐明钛活性中心结构与催化性能之间的关系，同时为杂原子分子筛的活性中心结构调控提供一种新思路。

Compared with the conventional process for the production of ethylene glycol, one-pot synthesis of ethylene glycol by oxidative hydration of ethylene with hydrogen peroxide over titanosilicate catalysts possesses several merits such as short processing and mild operating conditions but the utilization of hydrogen peroxide is rather low due to the low catalytic performance of titanosilicates, which has been considered as the main disadvantage. As the structure of titanium active sites is a critical factor for the catalytic performance of titanosilicates, the study on the adjustment of the structure of titanium active sites is of great significance for the design of a highly efficient catalyst for ethylene oxidative hydration. Based on the crystallization characteristics of the representative Ti-MWW titanosilicate, the framework Ti species modified with alkyl groups are generated by introducing alkyl-titanium compounds in the synthetic gel. After calcination, the alkyl groups will be transformed into hydroxyl groups. Consequently, the structure of titanium active sites can be accurately controlled by adjusting the density of Ti(OSi)3OH species in the zeolite framework. The proposed project aims at constructing high-performance titanium active sites, realizing the efficient activation of hydrogen peroxide and the effective transfer of reactive oxygen, and elucidating the relationship between the structure of titanium active sites and the catalytic performance of titanosilicates, meanwhile it will provide a new route for adjusting the structure of active sites in the heteroatomic zeolites.