Sn-Beta分子筛可控合成及催化生物质糖转化性能研究

Sn-Beta zeolite exhibits excellent catalytic performance in the conversion of carbohydrates to high-value added chemicals due to its large twelve-membered ring micropores in three dimensions and strong activation ability for oxygen-containing substituents. Sn-Beta zeolite synthesized by the classical hydrothermal method in fluoride media has few surface defects, high hydrophobicity and good stability. However, the hydrothermal method has the drawbacks of long crystallization time, low amount of Sn incorporation and poor repeatability. The project aims to study the crystallization mechanism of Sn-Beta zeolite and the factors controlling the crystallization rate. The project will further study the effects of the structure and surface properties of Sn-Beta on the activation of oxygen-containing substituents. The catalytic performance of Sn-Beta zeolite will be investigated in the isomerization of glucose and the retro-aldol reaction of glucose and fructose to alkyl lactate. Through the project, it is expected to establish the relationships between synthesis, structure and catalytic performance and develop a fast synthesis method of Sn-Beta zeolite with controllable properties and high catalytic performance for conversion of biomass derived carbohydrates. The research of the project will contribute to understanding deeply the synthetic chemistry of metal-containing silicate molecular sieves, which will establish the foundation for the industrial synthesis and application of metal-containing silicate molecular sieves.

Sn-Beta分子筛具有三维十二元环大孔结构和较强的对含氧取代基活化能力，在糖类化合物催化转化制高附加值化学品过程中表现出优异的催化性能。经典的含氟体系水热合成方法制备的Sn-Beta分子筛，表面缺陷少、疏水性高、稳定性好；但该法存在晶化时间长、Sn引入量低、重复性差等缺点。本项目拟研究Sn-Beta分子筛晶化机理与晶化速率的调控、Sn活性位类型和缺陷位的调控；Sn-Beta分子筛的结构、表面性质对含氧取代基的活化性能的影响及在催化葡萄糖转化为果糖、葡萄糖/果糖转化为乳酸酯中的催化性能，阐明Sn-Beta分子筛的合成方法-结构-催化性能之间的关系，建立性质可控、可高效催化生物质糖转化的Sn-Beta分子筛的快速合成方法。本项目的研究，将有助于加深对金属杂原子硅酸盐分子筛合成化学的认识，为该类分子筛的工业合成与应用打下基础。

Sn-Beta分子筛具有三维十二元环大孔结构和较强的活化含氧取代基的能力，广泛用作糖类及其衍生物催化转化制高附加值化学品过程的催化剂，性能优异。含氟体系水热合成的Sn-Beta分子筛，表面缺陷少、疏水性高、稳定性好；但该法存在晶化时间长、Sn引入量低、重复性差等缺点。本项目研究了晶种的数量和尺寸、晶化时间、水含量、Sn含量、硅源聚合度、模板剂和矿化剂用量、引入碱/碱土金属阳离子以及Sn络合剂等合成参数对Sn-Beta分子筛合成、性质和催化糖转化性能的影响，实现了Sn-Beta分子筛的晶化速率调控，建立了快速可控的合成方法，建立了Sn活性位的状态和缺陷位的调控方法，阐明了Sn-Beta分子筛合成方法-表面性质-催化性能之间的关系。研究发现，在晶种辅助下、在合成凝胶中引入碱/碱土金属阳离子、降低凝胶水含量均可以加快Sn-Beta分子筛晶化。增加凝胶中Sn含量可以提高骨架Sn数量，添加Sn络合剂能够提高Sn进入骨架位的比例，延长晶化时间提高分子筛结晶度，能够提高开放Sn位和闭合Sn位的比例。在合成凝胶中引入碱/碱土金属阳离子能够减少硅羟基缺陷位。增加凝胶中晶核数量，能够减小Sn-Beta分子筛晶粒尺寸，提高抗积碳能力；减少硅羟基缺陷位，有利于提高葡萄糖/木糖等单糖转化为乳酸甲酯的选择性；Si/Sn比在400-200范围内有利于提高乳酸甲酯的收率和生产效率。本项目的研究加深了对金属杂原子硅酸盐分子筛合成化学的认识，为该类分子筛的工业合成与应用打下了基础。