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CO_2作为主要的温室气体,CO_2固定利用引起了广泛的关注,同时它还是一种丰富无毒的C1资源,将其作为原料合成高附加值的化学品,不仅可以缓解温室效应,而且还可以缓解能源危机,具有重要的经济和战略意义.在CO_2的资源化利用中,制备2-苯基丙酸意义重大.2-苯基丙酸是一种重要的医药中间体,可用于合成布洛芬、酮洛芬等用途广泛的药剂.因此,其制备方法引起了人们的广泛关注.在典型的合成2-苯基丙酸均相催化体系中,经常使用Co,Ni和Pd等过渡金属催化剂,虽然得到的目标产物产率较高,但催化剂成本高,且很难循环使用,从而限制了其实际使用.电催化法为2-苯基丙酸的合成提供了一条新的途径.本课题组利用手性钴配合物作为催化剂电羧化不对称合成了手性2-苯基丙酸,其产率和ee值分别为37%和83%.此外,我们还制备了Co负载的纳米Ag电极,以其为工作电极不对称羧化1-溴乙基苯与CO_2反应,得到目标产物2-苯基丙酸的产率为58%,ee值为73%.在前期工作的基础上,本文利用无负载的纳米银电极(Ag NPs)为工作电极,电催化1-溴乙基苯与CO_2羧化制备2-苯基丙酸.银纳米电极是利用水合肼还原Ag NO3溶液经抽滤、干燥、压片而成.为了研究Ag NPs催化CO_2与1-溴乙基苯反应,在一室型电解池中,以Ag NPs为阴极,镁电极为牺牲阳极,以CH_3CN-TEAI(0.1 mol/L)溶液为电解质溶液,底物浓度为0.1 mol/L,饱和CO_2的氛围下进行恒电流电解,经后处理,可得目标产物2-苯基丙酸.为了提高2-苯基丙酸的产率,我们探讨了工作电极、电解电量、电流密度以及反应温度等条件对反应的影响,从而得到优化条件为反应温度0℃、电解电量2.5F/mol、电流密度5 m A/cm2,此时2-苯基丙酸的产率可达98%.在优化条件下,我们还研究了一系列苯基卤代物,如溴化苄、溴苯、α-溴苯乙酸、2-溴代萘、二苯基溴甲烷和1-氯乙基苯的电羧化反应.反应后可以得到相应的羧酸,并取得较好的收率(67%-88%).结果表明,纳米银电极对催化该类反应具有很好催化活性和普适性.本文所采用的条件都比较温和,无需高温或高压.在最优条件下,所制纳米银电极可重复使用至少10次,且保持催化活性不变.经过X射线衍射和扫描电镜表征发现,重复使用后纳米银电极的组成和微结构都保持不变.因此,该纳米银电极具有制备方法简单、催化活性高,稳定性好等特点,具备一定的应用前景.
As a major greenhouse gas, CO_2 has attracted a lot of attention due to its fixed use of CO_2. At the same time, it is a rich and nontoxic C1 resource, which can be used as a raw material to synthesize high value-added chemicals, not only to mitigate the greenhouse effect but also to ease Energy crisis has important economic and strategic significance in the resource utilization of CO_2 preparation of 2-phenylpropionic acid is of great significance .2-phenylpropionic acid is an important pharmaceutical intermediates can be used for the synthesis of ibuprofen , Ketoprofen and other widely used agents.Therefore, its preparation method has aroused widespread concern.In the typical synthesis of 2-phenylpropionic acid homogeneous catalyst system, often using transition metal catalysts such as Co, Ni and Pd, Although the high yield of the target product obtained, but the catalyst cost is high, and difficult to recycle, thus limiting its practical use.Electrocatalysis for the synthesis of 2-phenylpropionic acid provides a new way. Chiral 2-phenylpropionic acid was synthesized by asymmetric electrocarboxylation using chiral cobalt complex as catalyst, and the yield and ee were 37% and 83%, respectively. In addition, we also prepared Co-supported nano Ag electrode , As its working electrode asymmetric carboxylation 1- Ethylbenzene was reacted with CO 2 to obtain the target product 2-phenylpropionic acid with a yield of 58% and an ee value of 73% .On the basis of the previous work, the non-supported silver NPs (Ag NPs) Electrodeposition of 1-bromoethylbenzene and CO_2 carboxylation to prepare 2-phenylpropionic acid.Ag nano-electrode is the use of hydrazine hydrate reduction AgNO3 solution by suction filtration, drying, and tabletting.In order to study Ag NPs catalytic CO_2 And 1-bromoethylbenzene. Ag NPs were used as the cathode and magnesium electrode as the sacrificial anode in a one-cell electrolysis cell. The concentration of CH_3CN-TEAI (0.1 mol / L) / L, saturated CO 2 under the atmosphere of constant current electrolysis, post-treatment, can be the target product 2-phenylpropionic acid.In order to improve the yield of 2-phenylpropionic acid, we discussed the working electrode, electrolysis capacity, current Density and reaction temperature conditions on the reaction conditions, resulting in the optimal conditions for the reaction temperature 0 ℃, electrolytic power 2.5F / mol, current density 5 m A / cm2, then the yield of 2-phenylpropionic acid up to 98 %. Under optimized conditions, we also studied a series of phenyl halides such as benzyl bromide, bromobenzene, α-bromophenylacetic acid, 2-bromonaphthalene, The results showed that the nano-silver electrode has the potential to catalyze this kind of reaction with the corresponding carboxylic acid and the better yield (67% -88%). Very good catalytic activity and universality.The conditions used in this paper are relatively mild, without high temperature or high pressure.Under the optimal conditions, the prepared silver nanoparticles electrode can be reused at least 10 times, and maintain the catalytic activity unchanged.After X Ray diffraction and scanning electron microscopy showed that the composition and the microstructure of the nano-silver electrode remained unchanged after repeated use, therefore, the nano silver electrode has the advantages of simple preparation method, high catalytic activity and good stability, and has certain application prospects .