核壳结构M1-M2@rmSiO2纳米材料可控合成及其催化甘油氢解反应

Uniform dispersion of Metal nanoparticles is very important guarantee for stability and high cycle life of catalyst. This project will undergo these procedures as follows. Firstly, through thermal decomposition method, M1-M2 (M1= Pd, Pt，Ru，M2=Cu, Fe, Co) alloy nanoparticle (M1-M2 NP) is prepared then modified with different surfactant. Secondly, adding silica source and co-structure directing agent matching with the previous surfactant, M1-M2@ radially oriented mesoporous silica with controllable shell were synthesized through aggregating and self-assembling of the organic/inorganic hybrid. Controllable shell of SiO2 prevents the aggregation of M1-M2 NP and improves the stability of core, which is benifical to the separation and recovery of catalyst. On the other hand , shell structure of silica with radially oriented mesoporous makes M1-M2 NP communicate outside environment with shorter transmission path, which is helpful for catalytic process of mass transferring. TEM, XPS, XRD, BET are used to characterize and analyze the morphology, structure, composition and other details of obtained M1-M2@rmSiO2. Further on, the influence of various factors on the structure of M1-M2@rmSiO2 such as, the proportion of M1-M2 NP solution, surfactant, co-structure directing agent , pH value, the aging temperature and time of sol-gel,especially on the shell thickness, mesopores size and porosity of M1-M2@rmSiO2, would be studied in detail. Meanwhile by the aid of the model of the catalytic hydrogenation of glycerin, the catalytic performance of prepared M1-M2@rmSiO2 is investigated. Finally, by the means of the implementation of project, core@shell structure nanocomposite M1-M2@rmSiO2 would be a new efficient catalyst for the transformation from glycerin to propylene glycol.

金属纳米颗粒的均匀分散和防止团聚是稳定催化性能和延长寿命的重要保证。项目拟以不同的表面活性剂对合金纳米颗粒（M1-M2 NP ）表面修饰后，引入硅源及和表活相匹配的共结构导向剂，通过有机-无机杂化体的自调整，制备出壳层可控的纳米合金颗粒@辐射介孔二氧化硅 (M1-M2@rmSiO2)复合材料。壳层可阻止M1-M2团聚，提高内核稳定性；同时壳层的辐射介孔结构使M1-M2具有更短的传输路径与外界相通，有利于催化反应的传质过程。应用TEM、XPS、XRD、BET等手段对M1-M2@rmSiO2形貌、结构、组成等进行检测和分析；研究M1-M2 量、表面活性剂、共结构导向剂、pH值、硅源量、溶胶陈化温度时间等因素对M1-M2@rmSiO2结构的影响，特别是对壳层厚度、孔径和孔隙率的影响。以甘油催化氢解为模型反应，研究M1-M2@rmSiO2催化性能，为筛选甘油高值转化的新型催化剂提供材料基础。

金属纳米颗粒的均匀分散和防止团聚是稳定催化性能和延长寿命的重要保证。项目通过设计、制备负载型单金属和合金纳米催化剂，防止活性组分的团聚，提高催化剂的稳定性；以甘油催化氢解为模型反应，研究纳米合金催化性能，为筛选甘油高值转化的新型催化剂提供材料基础。通过研究取得以下主要成果：（1）制备系列SiO2负载的Cu、Pt、Pd等单金属和双金属催化剂并对结构进行表征；Cu/SiO2、Pt/SiO2和Cu-Me/SiO2 (Me=Pt、Pd、Ag、Ni)双金属催化剂都形成分散性良好的纳米颗粒，Cu-Pd/SiO2 和Cu-Pt/SiO2催化甘油氢解反应中表现出良好的催化活性、选择性和回收循环利用性能。其中Cu-Pt/SiO2双金属催化剂氢解反应甘油转化率近100%， 1,2-丙二醇选择性超过95%。分析确定Pt改变了Cu/SiO2催化剂结构，促进了Cu2+的还原，抑制了纳米Cu氧化和团聚。XRD结果显示Cu-Pt/SiO2中形成Pt-Cu合金纳米颗粒，两者协同作用促进了甘油反应的脱水和加氢过程；Cu-Pt/SiO2回收直接循环，三次甘油转化率和1,2-丙二醇选择性均保持在90%以上。（2）根据甘油氢解反应机理、设计、制备PdCu-KF/γ-Al2O3纳米复合催化剂，在载体中加入KF，产生超强碱位点，有利于甘油氢解反应脱水步骤，提高甘油氢解反应催化活性。在相对温和条件下，甘油转化率接近100％，1,2-丙二醇选择性达98.3％，催化剂循环5次时甘油转化率达到90 %以上。其中固体碱组分对催化剂活性有非常重要的影响。（3）发现Pd-Ni(1:1)/ γ-Al2O3可高效还原环戊二烯为环戊烯，转化率和选择性都超过90%；Pd-Cu /γ-Al2O3对环戊烯的选择性氧化合成环戊酮催化效果好,转化率可达95 %, 环戊酮选择性88%。两种催化剂都易于回收和可多次重复利用，具有工业应用前景。（4）研究Pd-Co/G（G石墨烯）对Sonogashira偶联反应产率可以达到98%，PdCu/G对硼氢化钠还原芳硝基化合物收率可达到98 %以上。同时Pd-M/Al2O3对吡啶直接偶联合成联吡啶显示良好催化活性，具有重要工业应用价值。