PILs调控Pd基双金属纳米团簇催化剂的构筑及其蒽醌加氢反应性能研究

Pd-based bimetallic nanocluster catalysts with low cost but high activity to anthraquinone hydrogenation reaction will be synthesized, aiming to intensify the anthraquinone process for the production of hydrogen peroxide (H2O2). First, a series of ionic liquid monomers with the building block of imidazole, quaternary ammonium, phosphonium structure will be designed and synthesized to generate poly(ionic liquids) (PILs) through polymerization. The relationship between the stabilized monometallic nanoclusters (Pd, Ni, Ru, etc.) and the distinct functional groups of the PILs will be disclosed through experimental characterization and molecular modeling. To prepare the bimetallic nanoclusters(Ni-Pd，Ru-Pd，etc.), the multi-functionalized PILs will be constructed. Effects of different ionic liquid building blocks, the species of anion/cation groups and their spacial locations on the synergic growth of bimetallic nanoclusters, the valence state and coordination agents will be investigated. Then, mesoporous supports will be optimized to prepare bimetallic nanocluster catalysts with the eggshell structure, of which the catalytic performance will be assessed for anthraquinone hydrogenation reaction. The deactivation pathway and regeneration method of the nanocluster catalyst will be studied. The procedure to prepare high efficient Pd-based nanocluster catalyst will be explored. The kinetics of the catalytic reaction and the transfer properties in the slurry reactor will be studied, the scaleup models of hydrogen process will be constructed, to achieve the intensification techniques for the production of high concentration H2O2 via the anthraquinone process.

以双氧水(H2O2)蒽醌法生产过程强化为应用背景，以研制高效、低成本的蒽醌加氢反应催化剂为目标。首先，分子设计并合成具有不同结构单元的咪唑类、季铵类、季磷类等离子液体单体，通过聚合反应研制具有不同结构特征的聚离子液体模板用于引导合成单金属纳米团簇，分子模拟与实验研究相结合，揭示对Pd、Ni、Ru等单金属团簇具有稳定作用的聚离子液体基本结构单元特征；针对Ni-Pd、Ru-Pd等双金属团簇，构建多功能聚离子液体模板，研究不同结构单元、阴阳离子种类与分布等对双金属团簇协同生长、价态与配位结构的调控规律；进而，优选介孔载体，研制出具有蛋壳形结构的双金属纳米团簇催化剂并表征其蒽醌加氢催化活性，研究其失活路径与再生方法，获得高效Pd基双金属纳米团簇催化剂的制备方法；研究催化反应动力学和浆态床反应器内传递特性，研究加氢过程放大模型，获得高浓度H2O2蒽醌法生产过程的强化技术。

本项目以双氧水(H2O2)蒽醌法生产过程强化为应用背景，研制出低成本、高活性的离子液体-Pd基复合催化剂。首先，设计了不同种类富含巯基、羰基、氨基、磷酸、酰胺等基团的有机分子模板，研究不同基团组合形成的微结构域对Pd纳米团簇成核生长的诱导作用及其催化活性的影响作用，获得了多位点诱导金属纳米团簇成核与生长进而调节其催化特性的规律。采用高压釜浆态床反应器评价催化剂的蒽醌加氢反应活性；分别研究了前驱体种类、第二金属添加剂、载体改性对Pd基催化剂加氢活性的影响作用，获得了Ga增强Pd基催化剂加氢活性的规律，以及磷改性载体提升催化活性的方法。基于微结构域调控纳米金属团簇结构的认知，筛选出咪唑类阳离子、硫酸氢根离子、甲烷磺酸根离子等阴离子组成的离子液体，首次制备出高效催化蒽醌加氢反应的离子液体与Pd复合催化剂。采用优选的离子液体1-丁基-3-甲基咪唑硫酸氢盐（IL）与Pd低负载量（0.3wt%）的条件下，制备出的Pd-4%IL催化剂对蒽醌加氢反应（60 oC，0.30 MPa，反应时间15 min）具有稳定的加氢效率为7.7 g/L，选择性为99.9%，明显优于同样负载量的Pd/Al2O3催化剂(4.9 g/L和96.9%); H2O2时空收率1229 gH2O2 gPd-1 h-1，远高于文献报道值。DFT计算揭示出离子液体的加入显著提高了反应物2-乙基蒽醌的活化程度，降低蒽醌加氢主反应所需的能垒；并且能抑制过度加氢副反应的发生。进而，研究发现离子液体微环境能够调节Pd-Y双金属纳米催化剂的结构特征，研制出离子液体协同Pd-Y双金属催化剂，Pd@0.7%Y/IL催化蒽醌加氢反应的加氢效率可达9.8 g/L（与前述反应条件相同）。这种新型催化剂成本低、活性高，在双氧水的工业生产中具有很好的应用前景，有望为我国“低碳工业技术变革解决碳失衡”做出贡献。