木质素解聚中两相催化剂构建和反应机理研究

Considering the complex type of reactions, the low yield of monomers and the products are prone to repolymeriztion in the depolymerization of lignin,this project aims to fabricate functional assembly diphasic- composite catalysts with geometric，interfacial，and compositional anisotropy structure and bimetal-acid/ basic for hydrogen processing combined with esterification or/and alkylationdepolymerization of lignin to aromatic monomers. By using the methods of seeded emulsion polymerization and chemical deposit with reduction,the multifunctional biphasic catalysts with bimetal-base/acid, well-defined sizes and geometries will be prepared for tuning interface structure and enhancing the catalytic activity of hydrogen processing and alkylation and/or esterification.(2)With the aid of biphasic solvents provided hydrogen and phase transform and enhanced effects by electron transfer, this project will investigate the synergistic effect between the hydrogen processing and alkylation reactions happening in the compounds contained ester bonds and phenolic hydroxyl groups (dominated by bimetal active site)and the hydrogen processing and esterification reactions occurring in the compounds included ether bonds, carbonyl and methoxyl groups (dominated by base/acid site),and clarify the selectivity and paths of key products. Furthermore,this project will also study the reactions occurred in the solvents and the biphasic solvent interface to explore the regularity of the bimetal-base/acid active sites how to tune the selectivity of products. By these investigations, this project will provide scientific fundament and technical support for increasing the yield of aromatic monomers and suppressing the repolymerization of depolymerization products.

针对目前木质素解聚过程反应类型复杂，单体产物收率低，产物易发生重聚的问题，构建具有几何、界面和组成各向异性的双金属-酸(碱)结构功能集成的两相催化剂用于木质素氢处理-烷基化/酯化解聚制取芳香物单体的研究。(1)通过种子乳液聚合和化学沉积-还原法设计合成形貌尺寸可控的双金属-酸(碱)两相催化剂以调节其界面结构与提高氢处理-酯化/烷基化反应的催化活性。(2)借助溶剂供氢解聚和相转移特性与催化剂界面间电子转移的增强效应，阐明醚断裂和酚羟基氢处理-烷基化反应(双金属中心)及醚键、羰基和甲氧基等选择性氢处理-酯化反应(酸或碱中心)的协同效应和关键产物的生成与转化路径。(3)研究两溶剂及界面的反应，探索双金属和酸(碱)位对反应产物调节规律，为提高芳香物单体收率，抑制木质素解聚物重聚提供理论基础与技术支撑。

木质素作为自然界中唯一可再生的芳香物资源，具有巨大的开发利用价值。木质素催化解聚制备芳香物和液体燃料是木质素高效利用的途径。本项目旨在通过加强木质素醚键断裂和（酚）羟基脱除的能力，提高单体芳香物和烃类产物收率。针对木质素结构特点，合成了Pd/MgO-C和RuMoOx/C金属-酸/碱功能耦合的系列两相催化剂, 研究了木质素C-O、C-C键和木质素碎片（酚）羟基断裂制备芳香物或烃类燃料的催化技术。研究包括：(1) 催化剂的制备与反应性能评价。合成了金属-酸碱协同的Pd/MgO-C催化剂，考察了不同热处理温度C的修饰对Pd/MgO-C形貌、活性组分、酸碱性、断裂C-O醚键和调控产物的影响；不同制备方法对RuMoxOy/C活性组分、颗粒大小和断键-脱氧性能性能的影响。(2)催化剂结构性质与反应性能的内在关联。结合多种催化剂表征手段重点研究了C源热处理温度对催化剂表面酸碱性、活性位、Pd与载体的影响；Ru和MoOx不同担载顺序对活性位的形成及Ru与载体的作用。研究了催化剂表面金属Pd、Ru与C-O醚键氢解断裂及加氢间的构效关系；MoOx物种与（酚）羟基断裂性能的内在联系，认识了影响催化剂性能的本质。（3）催化剂性能优化和稳定性能。①研究了Pd/MgO-C解聚松木粉制备芳香物和RuMoOx/C催化木质素油HDO的升级及催化剂的稳定性和失活机制。实现松木粉转化为单体芳香物的收率为24.6%，其中2-甲氧基-4-丙基愈创木酚的选择性达77.2%；②木质素油有效地转化为烃类（56.93%）和环己类醇/醚（18.74%）。③Pd/MgO-C循环使用后活性降低，Pd的氧化和MgO的团聚是催化剂活性降低的主要原因；RuMoOx/C循环使用后活性略有下降，是MoOx的聚集或迁移所致，但Ru的活性相对稳定。经过本项目的实施，构建了Pd/MgO-C和Ru-MoOx/C催化木质素C-O、C-C和（酚）羟基选择性断裂制备芳香物和烃类燃料的催化体系，阐明了催化剂结构、表面性质与C-O、C-C键和（酚）羟基断裂性能的关系。Pd的氢解活性和催化剂酸碱脱水/水合作用是断裂C-O键的关键。Ru和MoOx的协同促进了（酚）羟基的脱除而提高了烃类燃料的品质。研究结果为生物质路线制备芳香物和烃类燃料技术提供了理论支撑。