小分子氨基酸合成介孔沸石的反应机理及其结构特性研究

Mesoporous zeolites combine the advantages of ordered mesoporous molecular sieves and traditional microporous zeolites, possessing high diffusivity, accessibility to large molecules, excellent catalytic activity and stability. They have been utilized as commercial fluid catalytic cracking catalysts, and have great potential for further industrial application. .We for the first time employed amino acid as mesoporogen and synthesized mesoporous LTA zeolite. The research results are published as “Amino Acid Mediated Mesopore Formation in LTA Zeolite” in J. Mater. Chem. A 2016, 4, 2305–2313 this year, as well as in PCT patent application “amino-acid-zeolite composite materials and their transformed hierarchical mesoporous zeolites, methods of production and application thereof”. Unlike other mesopore generating templates such as carbons, surfactants or polymers, the amino acid templates could be easily removed by washing with water, eliminating the energy-intensive calcination step. Amino acid templates are commercially available of low cost, and can be recovered from the washing solution. Thus this novel amino-acid-templated route to mesoporous zeolites exhibits several advantages including easy handling, being easy to scale up, and environmental friendliness. Further investigation on the scope of possible amino acid and zeolite type is of great importance..The project plans to further research on the applicable range of amino acids and zeolites, including 22 proteinogenic amino acids and 3-5 zwitterionic structural analogs of L-carnitine, as well as zeolite type Y and SAPO-34 besides the A-type zeolite. We hypothesized that zwitterionic organic molecule self-assembly is responsible for the mesopore formation in zeolites, and propose to use time-resolved characterization of solid product collected at different synthesis stages with spectral, pore arrangement, framework composition and structure, and morphology analysis. .Based on the pilot data of this study, we propose to further investigate the disordered intracrystalline > 10 nm mesopore formation mechanism caused by the obviously smaller amino acid molecules, especially on the critical role of hydrogen bonding and the effect of amino acid on the zeolite polymorph, composition and morphology. This study is expected to provide scientific bases towards better understanding to amino acid mediated mesopore formation pathway in zeolites, and help further expand this new methodology to a variety of small molecules and molecular sieves.

介孔沸石兼有扩散系数大、大分子可达，及传统微孔沸石活性高和稳定性好的双重优势，是理想的吸附和催化材料。我们近期采用小分子氨基酸模板剂成功获得了介孔A型沸石，对比现有的碳、表面活性剂或高分子模板法，具有成本低廉、模板剂可回收和节能环保的独特优势，但其具体反应机制和适用氨基酸结构特性及沸石骨架特征尚不清楚。本项目拟选取组成蛋白质的22种氨基酸和3至5种永久双性离子，及与A沸石有联系和区分的Y和SAPO-34沸石为研究对象，提出“两性离子分子自组装致介孔沸石”新假设，拟通过水热合成各阶段产物时间分辨表征，研究光谱、孔道、骨架成分结构和形貌变化规律，厘清氨基酸致介孔沸石的综合机理，解答氨基酸形成>10nm晶内无序介孔和造成沸石相图形貌变化缘由等科学问题。本研究将从分子层面上阐明氨基酸在介孔沸石形成过程中的作用机制，有望大幅拓展氨基酸致介孔沸石新方法的普适性和有效性，具有重要理论价值和工业应用前景。

介孔沸石兼有扩散系数大、大分子可达，及传统微孔沸石活性高和稳定性好的双重优势，是理想的吸附和催化材料。本项目前期采用小分子氨基酸模板剂成功获得了介孔A型沸石，对比现有的碳、表面活性剂或高分子模板法，具有成本低廉、模板剂可回收和节能环保的独特优势，但其具体反应机制和适用氨基酸结构特性及沸石骨架特征尚不清楚。本项目选取了组成蛋白质的22种氨基酸和3种永久双性离子，证明了氨基酸作为小分子致孔剂的普适性并掌握调控规律，验证了氨基酸的结构特性和物理化学参数调控层级多孔A型沸石孔径大小、孔容和形貌等的规律；并对氨基酸中不同官能团进行了逐一拆解，提出了稳定有机阴离子是非常有可能的致介孔基团的假设，发展了一类有机小分子致介孔剂（Organic Mesopore Generating Agents, OMeGAs），包括但不限于氧、氮、和碳负离子前驱体，或具有负离子片段的两性离子化合物；合成了具有工业应用价值的介孔A、Y和SAPO-34沸石结构，并进行了吸附、催化、以及生物医学等应用研究；通过水热合成各阶段产物时间分辨表征和综合性的原位表征技术，研究光谱、孔道、骨架成分结构和形貌变化规律，并结合计算化学，厘清了有机小分子致介孔剂OMeGA致介孔沸石的化学作用综合机理，揭示了有机小分子作用于沸石结晶的动力学机制，厘清了有机分子构象对无机结晶的显著影响。.本项目以有机分子调控无机多孔分子筛晶体为主要研究内容，涉及有机小分子作用机制和有机致介孔剂，项目的研究有助于厘清其功能复合和结构特性，特别是用于层级沸石合成的有机小分子致介孔剂OMeGA及其多尺度的功能交叉，包括设计合成、机理研究、回收性、和应用性。有机小分子致介孔剂OMeGA的提出揭示了有机小分子在沸石晶化过程中除了结构导向OSDA和沸石生长调节ZGM之外的另一种作用机制— 空位制造，突破了有机致介孔剂只能从介观模板表面活性剂和高分子聚合物中选择的限制，有效交叉融合了小分子作用机制和有机致介孔剂。.本项目的研究成果包括发表论文18篇，申请发明专利10项，学术交流9次。