【作者】 梁曦；

【导师】 刘昌俊；

【作者基本信息】 天津大学 ， 化学工艺， 2010， 博士

【摘要】 利用可再生资源和催化剂是绿色化学十二原则的重要组成部分。葡萄糖氧化制葡萄糖酸的反应是符合绿色化学原则的典型反应之一。葡萄糖酸(盐)是化工、食品、医药、轻工业等领域的产品中重要的中间体,具有很广阔的应用前景。目前应用于葡萄糖氧化反应的催化剂主要有负载型的贵金属和双金属催化剂,以及非负载型金催化剂。当前的研究表明,葡萄糖氧化是一个结构敏感性反应,因此,催化剂的制备,特别是还原方法对催化剂活性组分形貌和粒径分布的影响,会直接影响其催化性能。本文利用辉光放电等离子体制备负载型钯催化剂及合成纳米金属溶胶,并将其应用于葡萄糖氧化反应中。利用氩气辉光放电等离子体在室温下成功还原了Pd/γ-Al2O3催化剂,通过与常规H2高温还原的催化剂对比,等离子还原制备的Pd催化剂具有更小的金属Pd的平均粒径、更高的分散度以及更强的金属载体间相互作用。等离子体还原催化剂因活性金属Pd粒径较小而容易在葡萄糖氧化反应中因氧中毒而失活,因而其催化反应的活性较低。通过在Ar保护下焙烧,等离子体还原催化剂中Pd颗粒尺寸有所增大,获得了比常规H2还原催化剂更好的催化活性。且等离子体还原催化剂中较强的金属载体间相互作用,使催化剂活性金属Pd在具有强螯合性的液相反应介质中更稳定,有效地避免了因活性组分流失而造成的不可逆失活。另外,通过实际测量,对等离子体制备方法进行了详细的能量消耗和经济花费的评估,结果表明等离子体技术确实是一种节能、经济的催化剂制备方法。辉光放电等离子体方法同样可以制备出以有序介孔二氧化硅为载体的Pd/SBA-15催化剂。研究表明,等离子体还原不会破坏SBA-15长程有序的六方结构。Pd/SBA-15催化剂因SBA-15载体具有的特殊结构特性(较大的比表面积和孔体积、较小的孔径分布),在应用于葡萄糖氧化反应中时,显示出了比传统二氧化硅载体负载催化剂Pd/SiO2更好的催化活性。通过直接还原HAuCl4水溶液,辉光放电等离子体在室温下5 min内成功合成了纳米金溶胶。整个制备过程一步完成,非常简单,不需添加任何还原剂、稳定剂。研究发现,通过简单地改变HAuCl4水溶液的初始浓度,可以有效地控制合成的水相金纳米颗粒的尺寸。这种金纳米溶胶在葡萄糖氧化反应中也展现了良好的催化活性和选择性。同时,等离子体制备纳米金属溶胶的方法被延伸到其它金属,成功合成了纳米钯溶胶。更多还原

【Abstract】 The use of catalyst and renewable resources has been considered to be part of the twelve principles of green chemistry. Oxidation of glucose to gluconic acid is a typical example of these green chemistry principles. Gluconic acid, used as an intermediate in the chemical, food, pharmaceutical, and light industries, is a promising product for various applications. Nowadays, gold colloids as well as supported noble-metal and bimetal catalysts are employed in glucose oxidation, which is a structure-sensitive reaction. Therefore, different preparation conditions, especially the reduction methods, could result in variation in particle morphology and size, and then impact on the catalytic behaviors. In this dissertation, supported palladium catalysts and metal colloids prepared by glow discharge plasma were used in glucose oxidation.The Pd/γ-Al2O3 was successfully reduced by argon glow discharge plasma at ambient temperature. Comparing with conventional catalyst reduced by hydrogen at elevated temperature, the plasma reduced Pd/Al2O3 had the characters of smaller diameter, higher dispersion of Pd nanoparticles, and stronger interaction between metal and support. Because of the smaller size of Pd nanoparticles, the plasma reduced catalyst was easier to be deactivated by oxygen poisoning, which led to a lower conversion rate. However, after being calcined under Ar flow, the plasma reduced catalyst exhibited a larger particle size and possessed a higher activity than the hydrogen reduced catalyst. It was noteworthy that the stronger metal-support interaction induced by plasma reduction enhanced the stability of active metal loaded on the support. This effect avoided the irreversible deactivation caused by Pd leaching into chelate medium. Furthermore, the energy consumption and economy evaluation were conducted, which confirmed that the plasma reduction route was an energy efficient and economically effective approach for metal catalyst preparation.The glow discharge plasma was also employed to synthesize Pd catalyst loaded on ordered mesoporous silica support SBA-15. The long-range order hexagonal structure was well maintained during the plasma reduction. As a catalyst in glucose oxidation, Pd/SBA-15 showed much better catalytic activity than Pd/SiO2, because of the unique structure properties, such as the high surface area, large pore volume, and narrow distribution of pore diameter. Gold colloids were successfully synthesized at room temperature using glow discharge plasma within only 5 min. There was only one step in this simple method without any addition of reducing agent or stabilizer. The size of colloidal Au nanoparticles could be effectively tuned in the nanometer range by easily adjusting the initial concentration of aqueous HAuCl4 solution. The as-synthesized Au colloids exhibited good catalytic activity for glucose oxidation. Moreover, initial results indicated that this new synthesis method could be easily extended to the preparation of Pd colloids.更多还原