亚胺功能化多孔金属海藻酸盐气溶胶的结构设计及性能评价

As a naturally organic polymer, alginates have attracted much attention because they are cheap, nontoxic and easy to shape. However, as the restriction of alginate’ structure，the loaded amount of metal in its structure is small. Designing novel alginate carriers with good molecular and pore structure could improve the loaded amount of metal, as well increase the number of active sites. In this project, the sodium alginate was modified by kinds of organic amine ligands to obtain the imine functionalized sodium alginate, and a series of imine functionalized porous metal-crosslinked alginates aerogel with different structure and metal were developed by crosslinking and CO2 supercritical drying. The inner structure, outside morphology, physical and chemical properties were well characterized by many analyze techniques. The influence of different kinds of organic amino ligands and the changing of reaction conditions on inner structure and metals loaded amount were both investigated. Their catalytic performances were tested in the hydroxylation of phenol with H2O2 as an oxygen source. In this system, the influences of experimental factors were investigated by the hydroxylation of phenol. In addition, the practical applications of the system were evaluated by the catalytic stability and reusability of the catalysts. It is expected to provide important fundamental data for the practical application.

天然有机聚合物海藻酸钠以其价廉、无毒和可任意成型等优点成为催化剂载体的良好选择，而由于海藻酸钠结构的限制，其交联金属的量有限，难以满足使用要求。因此设计具有良好分子结构和孔结构的新型海藻酸钠载体可提高金属担载量，有望显著增加催化剂的活性位点数量，改进催化剂性能。本项目拟采取结构设计的方法，利用不同有机胺配体对海藻酸钠中羟基进行修饰，得到亚胺功能化海藻酸钠，再通过交联配位反应和超临界CO2干燥的方法，制备具有良好孔结构和高催化活性的亚胺功能化多孔金属海藻酸盐气溶胶。研究不同有机胺配体对海藻酸钠进行修饰的实验条件，探索不同亚胺功能化多孔金属海藻酸盐气溶胶的分子结构，阐明不同有机胺配体对海藻酸盐气溶胶金属担载量和内部结构的影响。以苯酚羟基化反应为模型，建立不同亚胺功能化多孔金属海藻酸盐气溶胶催化剂的分子结构与催化性能的关系，为苯酚羟基化反应新型高效环保催化剂的研发提供科学依据。

天然有机聚合物海藻酸钠以其良好的金属交联能力和可任意成型等优点成为催化剂载体的良好选择，但是由于海藻酸钠结构的限制，四个片段才能交联一个金属离子，导致其交联金属的量有限，难以满足催化工业使用要求。本项目采取结构设计的方法，利用有机胺配体对海藻酸钠中的双羟基进行修饰，先通过氧化使其转变成双醛基（海藻酸二醛）；再进一步亚胺化，使海藻酸二醛转变成为双亚胺基官能团。亚胺化后的海藻酸钠结构中，存在两种金属的交联形式：1.未被亚胺化的结构片段继续以4个为单元交联一个金属离子；2.被亚胺化的片段，两个就可以交联一个金属离子。研究结果表明：亚胺化后的海藻酸钠的金属担载量比没有亚胺化的海藻酸钠提高了1.3倍，证实本研究方案可有效提高制备的催化材料的活性位点的数量。以苯酚羟基化反应为模型，考察了制备的亚胺功能化多孔金属海藻酸盐的催化性能。研究发现：氧化度对海藻酸钠结构的影响最关键，氧化反应在将双羟基氧化成双醛基的同时，也会导致海藻酸钠链的断裂，从而导致海藻酸钠分子量的下降。不同氧化度的海藻酸二醛在进一步亚胺化后，结构中的亚胺基官能团数目不同，直接影响与金属反应后，金属的担载量。氧化度越高，金属的担载量越高，催化性能越好。研究了有机胺配体对海藻酸钠进行修饰的实验条件，阐明有机胺配体对海藻酸盐气溶胶金属担载量和内部结构的影响。建立亚胺功能化多孔金属海藻酸盐气溶胶催化剂的分子结构与催化性能的关系，为苯酚羟基化反应新型高效环保催化剂的研发提供科学依据。