【作者】 朱闻闻；

【导师】 侯震山；

【作者基本信息】 华东理工大学 ， 工业催化， 2014， 博士

【摘要】 本文制备了多种过渡金属纳米催化剂,将其应用于催化加氢反应并得到令人满意的结果。首先,合成了水油两亲性的功能化离子液体,阳离子为聚乙二醇功能化的烷基咪唑双阳离子,阴离子为氯离子。在水相中,通过两亲性的离子液体制备并稳定水溶性的Pd纳米颗粒。电子透射显微镜(TEM)显示了Pd纳米颗粒的直径为1.9±0.3nm。水相中[C12Im-PEG]Cl2的物理化学性质通过表面张力测试,电导率测试和动态光散射(DLS)得到表征。结果证实,随着[C12Im-PEG]Cl2水溶液的浓度增加发现存在临界胶束浓度,[C12Im-PEG]Cl2水溶液在临界胶束浓度之上时可以形成大量胶束,该胶束对Pd纳米颗粒的稳定起到至关重要的作用并可促进催化加氢活性。而且,[C12Im-PEG]Cl2也是一个Gemini表面活性剂,亲油性的底物和含催化剂的水相在反应的时候形成乳化现象。乳化作用可以减少水油两相之间的传质阻碍对活性的不利影响,并增加了底物与Pd纳米颗粒的接触机会,从而提高了反应速率。另外,离子液体中的咪唑阳离子对Pd纳米颗粒的表面具有一定的修饰作用,从而影响了其加氢活性。在温和的条件下,Pd纳米催化剂对不同底物的加氢反应显示了高效的催化活性。催化剂至少可以循环8次并提供完全转化的活性。由聚乙二醇功能化的烷基咪唑阳离子和三苯基膦三间磺酸根(P(C6H4-m-SO3-)3)组成的功能化离子液体在乙酸乙酯中具有温控相行为的特点([C12Im-PEG]1.5[tppt]),离子液体在室温下几乎不溶于乙酸乙酯,当升高温度(>35℃)之后完全溶于乙酸乙酯,降温(0℃)后从乙酸乙酯中析出。选用乙酸乙酯作为温控溶剂可以减少体系带来的毒性。该温控离子液体可以用来稳定过渡金属纳米颗粒得到温控相分离加氢催化剂。由于离子液体中阴阳离子的协同作用(阳离子部分提供温控效果,阴离子部分有效地稳定金属纳米颗粒),过渡金属纳米催化剂显示了显著地温控相分离现象和优良的催化活性和选择性,同时过渡金属纳米催化剂具有卓越的稳定性。在α,β-不饱和醛的加氢反应中,温控离子液体稳定的Pd和Rh纳米颗粒针对C=C双键的选择性加氢效果优于商业化的Pd/C和Rh/C催化剂。通过NMR表征,我们发现离子液体的阴离子(P(C6H4-m-SO3-)3)通过配位作用改变了纳米颗粒表面的电子性质,从而影响了加氢选择性。另外,聚乙二醇功能化的咪唑阳离子为纳米催化剂在乙酸乙酯中提供了温控相分离的特点,实现了“均相反应、多相分离”。该体系可以催化多种带不同官能团的底物的加氢反应。通过温控相分离,催化剂可以方便的与产物分离并回收。催化剂可以进行10次循环并没有任何活性降低。磺酸功能化的二氧化硅负载的Ru纳米催化剂(Ru/SiO2-SO3H)被用于一锅法转化纤维素制山梨醇。首先利用共价键将磺酸官能团嫁接到二氧化硅表面(SiO2-SO3H),然后将Ru纳米颗粒负载于SiO2-SO3H,制得的Ru/SiO2-SO3H是一个双功能催化剂,同时含有Br(?)nsted酸中心和金属中心。针对纤维素的氢解反应,Br(?)nsted酸用于催化水解纤维素制葡萄糖,Ru纳米颗粒用于催化加氢葡萄糖制山梨醇,从而实现一锅法转化纤维素制山梨醇。对比机械混合的SiO2-SO3H+SiO2-SO3H催化剂,双功能催化剂Ru/SiO2-SO3H可以得到更高的山梨醇产率,在150℃下反应10小时,山梨醇的产率达到61.2%。通过XPS和吡啶吸脱附红外的表征,在Ru/SiO2-SO3H上的磺酸官能团和Ru纳米颗粒之间存在相互作用。磺酸官能团和Ru纳米颗粒之间的相对位置对增加山梨醇的产率影响很大。由于磺酸官能团对Ru纳米颗粒的配位或中毒作用,山梨醇分子可能更容易从Ru的表面脱附,从而在某种程度上避免了进一步的副反应发生。另外,该催化剂可以重复使用五次仅有稍微的山梨醇产率下降。更多还原

【Abstract】 In this work, several transition-metal nanocatalysts have been prepared. They were applied in catalytic hydrogenation reactions and showed satisfactory results. The highly water-soluble palladium nanoparticles (NPs) were synthesized by using the amphiphilic poly(ethylene glycol)-functionalized dicationic imidazolium-based ionic liquid ([C12Im-PEG]Cl2) as a stabilizing agent. The aqueous dispersed palladium NPs in the range of1.9±0.3nm were observed by transmission electron microscopy (TEM). The physicochemical properties of [C12Im-PEG]Cl2in aqueous phase have been characterized by surface tension and Dynamic Light Scattering (DLS) measurements. It was demonstrated that the amphiphilic ionic liquid could form micelles above its critical micelle concentration (CMC) in aqueous solution and the micelles played a crucial role in stabilizing palladium NPs and thus promoted the catalytic hydrogenation. Furthermore, the dicationic ionic liquid can act also as a Gemini surfactant and generated emulsion between hydrophobic substrates and catalytic aqueous phase during the reaction. The aqueous dispersed palladium NPs showed efficient activity for the catalytic hydrogenation of various substrates under very mild conditions and the stabilizing Pd(0) nanoparticles (NPs) could be reused at least eight times with a complete conservation of activity.The use of transition metal nanoparticles/ionic liquid (IL) as a thermoregulated and recyclable catalytic system for hydrogenation has been investigated under mild condition. The functionalized ionic liquid was composed of poly(ethylene glycol)-functionalized alkylimidazolium as cation and tris-meta-sulfonato-phenylphosphine (P(C6H4-m-SO3-)3) as anion ([C12Im-PEG]1.5[tppt]). Simultaneously, ethyl acetate was chosen as the thermomorphic solvent to overcome the drawbacks like usage of toxic organic solvents in this contribution. Due to the cooperative effect regulated both cation and anion of ionic liquid, the nano-catalysts revealed distinguished temperature-dependent phase behavior and excellent catalytic properties, such as catalytic stability, activity and selectivity. For the hydrogenation of α,β-unsaturated aldehydes, palladium and rhodium nanopartciles stabilized by ionic liquid exhibited higher selectivity for the hydrogenation of the C=C bonds than the commercial catalyst (Pd/C and Rh/C). We believed that the anion of the ionic liquid, P(C6H4-m-SO3-)3, played a role in modification of the metal nanopaticles through the coordination capacity, changing the surrounding electronic characteristics of nanoparticles, while the poly(ethylene glycol)-functionalized alkylimidazolium cation provided the thermomorphic properties for the nano-catalysts in ethyl acetate. The present catalytic systems can be employed for the hydrogenation of a wide range of the substrates with different functional groups. The catalysts could be easily separated from products by phase separation and efficiently recycled ten times without significant changes in the catalytic activity.Sulfonic acid-functionalized silica-supported ruthenium catalyst (Ru/SiO2-SO3H) was employed for the hydrogenolysis of cellulose in a one-pot in neutral water medium. Ru/SiO2-SO3H was a bifunctional catalyst containing both Br(?)nsted acidic site and metal site (Ru). Compared with the mechanical mixture of silica-supported Br(?)nsted acid (SiO2-SO3H) and silica-supported Ru catalyst (Ru/SiO2), the bifunctional catalyst showed much higher yield to sorbitol, which can reach up to61.2%when the reaction was performed for10h at150℃. Through the characterizations of XPS and pyridine-adsorbed FT-IR, it was observed the existence of the interaction between sulfonic groups and Ru nanoparticles in Ru/SiO2-SO3H catalyst. The sulfonic acid groups and metal sites in the adjacent position were important for enhancing the yield of sorbitol. In addition, the present catalyst can be reused five times with only a slight decrease in yield of sorbitol in the consecutive recycles.更多还原