TS-1分子筛改性及其在环己酮氨氧化反应中的催化性能研究

Compared with the conventional process for the production of cyclohexanone oxime, the ammoximation of cyclohexanone to produce cyclohexanone oxime over TS-1 is considered to be an effective, "green" process. However, because the catalytic activity of TS-1 is significantly limited by the mass transfer inside TS-1 crystals, TS-1 having only nano-sized crystals shows the high catalytic activity, resulting in high energy costs due to the difficulties associated with the filtration of TS-1 crystals from its synthesis mixture as well as with the separation of TS-1 as the catalyst from the reaction medium during the ammoximation. The proposed project aims at elucidating the origins that result in the mass-transfer limitations inside TS-1 crystals during the catalytic ammoximation of cyclohexanone. Consequently, a simple but effective post-treatment method will be developed to improve the mass-transfer limitations inside TS-1 crystals. The post-treated TS-1 catalyst could possess the improved mass-transfer properties, implying that TS-1 with larger crystal sizes could have the enhanced catalytic activity in the ammoximation. This could significantly reduce energy costs, due to the easy filtration of large TS-1 crystals from the synthesis mixture as well as to the easy separation of TS-1 as the catalyst from the reaction medium during the ammoximation. The ultimate goal of the proposed project is to provide some guidelines for the design, preparation, and use of TS-1 catalysts on an industrial scale.

与传统生产环己酮肟工艺相比，TS-1分子筛催化环己酮氨氧化制环己酮肟具有生产高效且环境友好的显著优点。但TS-1催化剂因受晶内传质限制，只有纳米尺寸的TS-1晶体才显示出高催化活性，然而，纳米TS-1合成过程中易造成分子筛晶体与合成液难分离，而且在反应过程中使得催化剂与反应液难分离，从而造成高能耗。本项目旨在阐明TS-1分子筛在环己酮氨氧化反应中受传质限制的原因，通过简单而有效的后处理技术来改性TS-1催化剂的传质性能。经改性的较大晶粒TS-1催化剂在环己酮氨氧化反应中不仅具有高催化活性，而且可达到合成TS-1过程中分子筛晶体与合成液易分离以及反应过程中TS-1催化剂与反应液易分离的目标，从而降低分离能耗，为TS-1工业催化剂的设计、制备及使用条件提供指导。

钛硅分子筛（TS-1）是一类由钛原子取代部分硅原子且具有MFI型结构的杂原子微孔沸石分子筛，它在与过氧化氢溶液组成体系的有机催化氧化反应中表现出优异的催化性能。然而，TS-1在工业应用过程中却存在小晶粒TS-1难分离、大晶粒受晶内传质限制和生产成本高等问题。.基于此，我们制备了不同晶体尺寸的TS-1分子筛，采用紫外高温技术对其进行改性并用于环己酮氨氧化反应中，阐明了导致TS-1受传质限制的原因。此外，合成了Ti-TUD-1介孔材料，并将其应用于环己酮氨氧化反应中。.对照课题任务书要求的目标，我们完成了下列指标：.1)阐明了导致TS-1受传质限制的原因：在TS-1催化环己酮氨氧化反应中，反应物分子NH3和H2O2及生成的中间体NH2OH（羟胺）与TS-1晶内存在的Si-OH基团中的OH可形成作用力较强的氢键，严重限制这些分子在TS-1孔道内的扩散；.2)采用紫外高温处理技术消除了所合成TS-1分子筛晶体的Si-OH基团，改性后的TS-1分子筛在环己酮氨氧化反应中的催化活性较改性前有了明显提高；可望解决目前工业上使用TS-1微晶所带来的技术难题，即在TS-1合成过程中造成分子筛晶体与合成液难分离和反应过程中催化剂与反应液难分离的技术问题；.3)成功制备了介孔材料Ti-TUD-1，其在环己酮氨氧化反应中表现出了较好的催化性能。.本项目的相关研究成果在第二届欧亚分子筛会议、2015沸石与微孔晶体国际研讨会、第十八届国际分子筛会议、第九届环境催化国际会议、第六届国际氧化物材料研讨会和2018沸石与微孔晶体国际研讨会上进行了学术交流；项目负责人应邀在第六届国际氧化物材料研讨会上做大会报告。申请中国发明专利3件；在国际学术期刊上发表研究论文8篇；相关深入研究论文正在整理和投递中。.项目达到了预期研究目标和预期成果要求。