改性钯炭催化剂在维生素E关键中间体选择性加氢合成中的催化效果的研究

发布时间：2018-02-27 20:51

本文关键词： 氮掺杂碳材料钯炭催化剂维生素E 炔醇三甲基苯醌　出处：《浙江大学》2017年硕士论文　论文类型：学位论文

【摘要】：维生素E是人体必需但是不能自行合成的维生素之一,在调节人体的生育功能以及抗氧化功能上发挥着重要的作用,因而其成为维生素产业的三大支柱产品之一。在工业上,广泛采用以异植物醇与三甲基氢醌缩合的方法制备维生素E。在这一合成路径中,又可以分为苯环部分的合成和异植物链部分的合成。其中相关炔醇及三甲基苯醌的选择性加氢分别作为两部分的必经步骤,有着十分重要的地位。在炔醇的选择性加氢过程中,传统意义上的林德拉催化剂有着水溶液中无法循环套用和重金属(Pb)危害环境的缺陷。而在传统的三甲基苯醌的还原工艺中,使用化学还原剂还原的方法也有着过量试剂污染环境的缺陷。近年来,多相催化反应以其催化剂的可回收利用和低成本而在工业催化中具备十分显著的优势。其中碳基催化剂,尤其是氮掺杂碳材料,以其原料绿色成本低、独特的物理化学性质、高效的催化活性受到了极大的关注。关于炔醇的催化选择性加氢部分,本论文以生物质衍生物——氨基葡萄糖盐酸盐(GAH)和氧化锌作为原料,一锅法得到氮掺杂碳(CN)和氧化锌的复合载体。而后在其上浸渍负载钯纳米颗粒高温还原得到催化剂(PdZn/CN@ZnO)。在异植物醇关键中间体2-甲基-3-丁炔-2-醇(MBY)选择性加氢制备2-甲基-3-丁烯-2-醇的反应中,相比于PdZn/ZnO,PdZn/CN@ZnO催化剂的催化活性有了明显的提升(6倍),同时其选择性基本保持不变(92%)。进一步通过反应条件的优化和添加剂的使用,烯醇的收率能够达到95%。相关表征和理论计算揭示PdZn/CN@ZnO高选择性的原因是Zn原子对边角位Pd原子的替代效应,高活性的原因是材料的水溶液分散性提升以及PdZn和CN的相互作用。该催化剂显示了良好的循环套用性能(9次),在扩展其他工业底物的测试中也有着优异的表现。在三甲基苯醌的催化选择性加氢部分,本论文以工业废炭为原料,通过引入碳酸氢钾和草酸铵化学活化的方法,得到高比表面积的活化氮掺杂活性炭载体(ANAC),而后通过浸渍钯前驱体和甲酸还原法得到催化剂(Pd/ANAC)。当其应用于三甲基苯醌(TMBQ)的选择性加氢时,选择性大于99%,催化活性是未活化钯炭催化剂(Pd/AC)的将近3倍。进一步的反应测试能够得到该反应的反应动力学参数,反应相对于底物三甲基苯醌呈现一级动力学特征(即a=1),相对氢气压力的级数b=1.05,反应活化能为56kJ/mol,这些数据能够为三甲基苯醌的催化加氢工业生产提供指导意义。综上所示,本论文通过实现生物质原料和废弃物的转化,制备得到氮掺杂改性的钯炭催化剂,实现了炔醇和三甲基苯醌的高效选择性加氢,为维生素E的高效合成提供一定的借鉴意义。
[Abstract]:Vitamin E is one of the essential but not self-synthesized vitamins, which plays an important role in regulating the reproductive and antioxidant functions of the human body, so it has become one of the three pillars of the vitamin industry. Vitamin E is prepared by condensation of iso-phytol with trimethylhydroquinone. The selective hydrogenation of related alkynols and trimethylbenzoquinones is a necessary step of the two parts, and plays a very important role in the selective hydrogenation of alkynyl alcohols. In the traditional sense, Lindela catalyst has the defects that it is impossible to recycle in aqueous solution and heavy metal Pb) is harmful to the environment, but in the traditional reduction process of trimethylbenzoquinone, In recent years, heterogeneous catalytic reactions have a significant advantage in industrial catalysis due to their recoverability and low cost. In particular, nitrogen-doped carbon materials have attracted great attention for their low green cost, unique physical and chemical properties and high catalytic activity. In this paper, the biomass derivative, glucosamine hydrochloride (GAH) and zinc oxide, were used as raw materials. Nitrogen-doped carbon monoxide (CNN) and zinc oxide were prepared by one-pot method, and then impregnated with supported palladium nanoparticles for high temperature reduction to obtain catalyst PdZnR / CNCNZnO.Selective hydrogenation of 2-methyl-3-butyne-2-butyne-2-ol MBY was carried out in the key intermediate of isophytol. In the reaction of 2-methyl-3-butene-2-ol, Compared with PdZn / ZnO- / PdZn/ CN@ ZnO catalyst, the catalytic activity of PdZnR / CN@ ZnO catalyst has been significantly improved by 6 times, and its selectivity has remained basically unchanged. Further, through the optimization of reaction conditions and the use of additives, The yield of enol can reach 95%. The reason for the high selectivity of PdZn/CN@ZnO is the substitution effect of Zn atom on PD atom. The high activity is due to the dispersion of aqueous solution of the material and the interaction between PdZn and CN. The catalyst shows good cycling performance for 9 times and has excellent performance in the test of extending other industrial substrates. In the catalytic selective hydrogenation of trimethylbenzoquinone, In this paper, chemical activation of potassium bicarbonate and ammonium oxalate was carried out using industrial waste carbon as raw material. The activated nitrogen doped activated carbon carrier with high specific surface area, Anacron, was prepared by impregnating palladium precursor and formic acid reduction method to obtain catalyst PD / A NACN. When the catalyst was applied to the selective hydrogenation of trimethylbenzoquinone (TMBQ), The selectivity is greater than 990.The catalytic activity is nearly three times higher than that of the unactivated palladium / carbon catalyst PD / AC. The kinetic parameters of the reaction can be obtained by further reaction test. The reaction shows first-order kinetic characteristics in relation to the substrate trimethylbenzoquinone (i.e., a ~ 1 ~ (-1)), the order bn _ (1.05) relative to hydrogen pressure, and the activation energy of the reaction is 56 kJ / mol. These data can provide guidance for the commercial production of trimethylbenzoquinone in catalytic hydrogenation. In this paper, nitrogen-doped palladium and carbon catalysts were prepared through the conversion of biomass raw materials and wastes, and the selective hydrogenation of alkynyl alcohol and trimethylbenzoquinone was realized, which provided some reference for the high efficiency synthesis of vitamin E.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36;TQ466.5

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