新型金属氧化物负载纳米贵金属催化剂的制备、结构及其催化加氢性能研究

发布时间：2019-04-28 16:19

【摘要】：四价氧化物纳米材料是一种新型的无机功能材料,由于其自身独特的物化性能而被广泛的用作催化剂载体或者直接作为催化剂使用,广泛应用于氧化、光催化、催化加氢等各个催化领域当中。其中具有代表性的氧化物纳米材料,例如：二氧化钛、二氧化铈、二氧化锆等。催化加氢反应作为催化科学研究领域当中的核心问题之一,是催化反应当中的基础反应,在实际中应用非常普遍广泛。葡萄糖加氢制得山梨醇是工业上主要制备山梨醇的方法,山梨醇是一种应用很广泛的精细化工产品和工业原料。山梨醇具有无气味、有甜味、无毒性、保湿性、乳化性等优异的性能,是一种非常重要的高附加值的精细化工产品。山梨醇及其产物普遍应用在化妆品、食品添加剂、烟草、化工、制药等行业当中。α,p-不饱和醛酮因其结构特殊而具有非常高的生化活性,其加氢产物种类繁多,在现代化工领域中占据极其重要的位置。其中肉桂醛和柠檬醛都是α,p-不饱和醛酮的代表。肉桂醛和柠檬醛大部分加氢产物广泛应用于香精、香料、医药等领域,因而研究其催化加氢反应对生产生活、科学理论研究都具有非常重要的现实意义。本文中分别以单金属氧化物和双金属氧化物为载体,以Ru、Pt金属为活性组分得到了负载型催化剂,并研究其在各反应当中的催化加氢性能。详细内容如下：(1)制备Ru/TiO2催化剂和其催化性能评价。用硼氢化钠作为沉淀剂,以四氯化钛作为原料制备出二氧化钛载体。合成出了高比表面的纳米材料,其比表面高达215.8m2 g-1。再将硼氢化钠作为还原剂,制备出高分散的负载型钌催化剂Ru/TiO2,其中钌的负载量为3%wt,并将其应用到葡萄糖的催化加氢反应当中,与传统载体负载的催化剂相比催化性能结果明显提高。(2)制备高比表面、高分散的负载型Pt/CeO2-ZrO2催化剂。采用成核／晶化隔离法与热动力学可控的水热法相结合的新的合成方法,以硼氢化钠为沉淀剂,不需要经过高温煅烧,直接一步合成了所需的四价双金属复合氧化物。并采用液相还原的方法,进一步制备高分散的负载型铂催化剂Pt/CeO2-ZrO2,其中铂的负载量为5%wt,并评价其对肉桂醛的加氢性能。其催化活性明显高于单载体负载的Pt/CeO2或Pt/ZrO2。通过改变铈锆的比例,制备不同载体的Pt/CeO2-ZrO2催化剂,载体中的CeO2-ZrO2与铂存强相互作用,金属分散性提高,同时催化剂表面的酸性位的数量及酸强度和pt0的富电子性也明显提高,在肉桂醛催化加氢反应中显示出更高的活性和对C=O键的选择性。
[Abstract]:Tetravalent oxide nanomaterials are new inorganic functional materials. Because of their unique physical and chemical properties, tetravalent oxide nanomaterials are widely used as catalyst carriers or directly used as catalysts, and are widely used in oxidation and photocatalysis. Catalytic hydrogenation and other catalytic fields. Representative oxide nanomaterials, such as titanium dioxide, cerium dioxide, zirconia and so on. Catalytic hydrogenation, as one of the core issues in the field of catalytic science, is the basic reaction in catalytic reaction, and it is widely used in practice. The preparation of sorbitol from glucose hydrogenation is the main method to prepare sorbitol in industry. Sorbitol is a widely used fine chemical product and industrial raw material. Sorbitol has excellent properties, such as odorless, sweet, non-toxic, hygroscopic, emulsifying and so on. It is a very important fine chemical product with high added value. Sorbitol and its products are widely used in cosmetics, food additives, tobacco, chemical industry, pharmaceutical and other industries. 伪, p-unsaturated aldehydes and ketones have very high biochemical activity because of their special structure. It occupies a very important position in the field of modern chemical industry. Cinnamaldehyde and citral are the representatives of 伪, p-unsaturated aldehydes and ketones. Most of the hydrogenation products of cinnamaldehyde and citral are widely used in the fields of essence, spice, medicine and so on. Therefore, the study of catalytic hydrogenation of cinnamaldehyde and citral has very important practical significance for production and life, scientific and theoretical research. In this paper, the supported catalysts were prepared by using single metal oxide and bimetallic oxide as support and Ru,Pt metal as active component, respectively, and their catalytic hydrogenation performance in each reaction was studied. The main contents are as follows: (1) preparation of Ru/TiO2 catalyst and evaluation of its catalytic performance. Titanium dioxide carrier was prepared by using sodium borohydride as precipitator and titanium tetrachloride as raw material. Nano-materials with high specific surface area have been synthesized. The specific surface area is as high as 215.8m2 g _ 1. Then, sodium borohydride was used as reducing agent to prepare highly dispersed supported ruthenium catalyst Ru/TiO2, in which the amount of ruthenium supported was 3% wt, and it was applied to the catalytic hydrogenation of glucose. Compared with the catalyst supported on the traditional support, the catalytic performance of the catalyst was improved obviously. (2) the supported Pt/CeO2-ZrO2 catalyst with high specific surface area and high dispersion was prepared. A new synthesis method combining nucleation / crystallization isolation method with thermodynamic controllable hydrothermal method was adopted. The tetravalent bimetallic composite oxide was synthesized directly in one step using sodium borohydride as precipitant and without the need of high temperature calcination. The highly dispersed supported platinum catalyst Pt/CeO2-ZrO2, was further prepared by liquid phase reduction, in which the platinum loading was 5% w / t, and the hydrogenation performance of the catalyst to cinnamaldehyde was evaluated. Its catalytic activity is obviously higher than that of Pt/CeO2 or Pt/ZrO2. supported on single carrier. Pt/CeO2-ZrO2 catalysts with different supports were prepared by changing the ratio of cerium to zirconium. CeO2-ZrO2 in the support interacted with platinum and the metal dispersion was improved. At the same time, the number of acidic sites on the surface of the catalyst and the strength of acid and the electron-rich property of pt0 were also improved obviously. The catalytic hydrogenation of cinnamaldehyde showed higher activity and selectivity for C _ (O) bond.
【学位授予单位】：北京化工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：O643.36

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