【作者】 张英帅；

【导师】 丁勇；

【作者基本信息】 兰州大学 ， 物理化学， 2010， 硕士

【摘要】 多金属氧酸盐是一类人们所熟知的无机化合物,近年来其在催化领域中的应用越来越多地受到人们的重视,因为多金属氧酸盐是一种催化活性好、选择性高、环境友好、兼具酸性和氧化性的双功能催化剂,这些特点使其可以很好地应用于氧化反应中。本论文的研究工作主要集中在以下几个方面：1.过氧钨酸盐[DDA]3[(OH)Si03{WO(02)2}3]选择性催化烯烃环氧化研究。报道了一种新的过氧钨酸盐[DDA]3[(OH)Si03{WO(02)2}3],体系以过氧化氢作为氧化剂,乙酸乙酯为溶剂研究了烯烃的环氧化反应。此催化剂具有控制相转移的特征,对催化烯烃的环氧化反应有高的转化率及选择性。催化剂[DDA]3[(OH)Si03{W0(02)2}3]自身不能溶解于乙酸乙酯,但是伴随着反应温度的升高以及催化剂与底物和过氧化氢的作用,催化剂慢慢溶解于溶剂,从而实现均相催化烯烃环氧化反应。反应结束后,由于过氧化氢的消耗,催化剂活性氧的转移催化剂结构发生变化,随着温度的降低催化剂从溶剂中沉淀出来。这个新的催化体系具有控制相转移的特征,能够均相的催化烯烃环氧化反应,而且也避开了毒性较大的含氯溶剂的使用。催化环己烯的环氧化反应,催化剂循环20次活性也没有明显的降低。采用ICP,IR,UV-vis,183W NMR and 29Si MAS NMR等谱学方法对新鲜及使用过的催化剂进行表征。2.缺位Keggin型硅钨酸盐催化醇选择氧化研究研究了二缺位的硅钨酸盐,K8[γ-SiW10O36]·13H20,以30%的过氧化氢作为氧化剂,水作为溶剂,选择性氧化醇。反应在水油双相体系中进行,在较温和的条件下获得了较高的收率和较好的选择性,而且催化剂也容易回收再利用。室温下催化环己醇氧化生成环己酮,反应重复5次后,催化剂活性没有明显的降低。3.取代Keggin型硅钨酸盐催化醇选择氧化研究合成了一系列二取代Keggin杂多酸。实验发现在催化环己醇氧化生成环己酮的氧化反应中,二取代的SiW10Al2活性最好。在温度为90℃,水作为溶剂,过氧化氢作为氧化剂的反应条件下,选择性催化氧化了一系列醇,获得了较好的催化效果和高选择性。我们认为铝引入杂多酸以后,影响了多酸阴离子的电荷分配,影响了其酸碱性,有利于催化氧化醇。更多还原

【Abstract】 Polyoxometalates are a kind of inorganic compounds which are well known by people. The compounds have been received more and more attention in the area of catalysis in recent years, because they are economical and environmentally friendly catalysts with high catalytic performance and selectivity. Their acidic and redox properties can be controlled at atomic or molecular levels. Therefore, polyoxometalates are capable of catalyzing oxidation reaction. The main progress and research results in the paper have been obtained as follows:1. Peroxotungstate [DDA]3[(OH)SiO3{WO(O2)2}3] as catalyst for epoxidation of alkenesThis paper reported a new peroxotungstate [DDA]3[(OH)SiO3{WO(O2)2}3] (Ⅰ), which was synthesized and used as reaction-controlled phase-transfer catalyst for epoxidation of alkenes with H2O2 as the oxidant and ethyl acetate as the solvent epoxidation systems. This system can be used for catalytic epoxidation of olefins and exhibits high conversion and selectivity. In an H2O/ethyl acetate biphasic system, catalyst I itself was not soluble in the ethyl acetate phase, but it dissolved slowly with the increase of reaction temperature and action of hydrogen peroxide and olefin, which subsequently led to homogeneous catalytic epoxidation of olefins. When the reaction stopped, the structure of catalysts had changed with the transfer of active oxygen of catalyst and consumption of hydrogen peroxide. With temperature dropping, catalyst I precipitated gradually. This new system not only catalyzed homogeneous epoxidation of alkenes with unique reaction-controlled phase-transfer catalyst character, but also avoided the using of toxic solvents. The catalyst could be easily recovered and reused after reaction, and the epoxidation of cyclohexene was recycled twenty times without activity loss. The fresh catalyst, used one were characterized by ICP, IR, UV-vis,183W NMR and 29Si MAS NMR.2. Substituted Keggin-polyoxometalate complexes as catalyst for the selective oxidation of alcohols.In this study, a series of dimetal-substituted Kiggin-type POMs were synthesized. The results indicated that dialuminum-substituted Keggin-polyoxometalate was more efficient than others for oxidation of alcohols to ketones. The high yields of ketones and good selectivity were obtained in oxidation of alcohols in water at 90℃. Compared with other dimetal-substituted POMs catalysts, aluminum was introduced into polyoxometalate that had the advantage of the selective oxidation of alcohols. This could be due to Al introduced into polyoxometalate that changes distribution of charges in different pattern and changes its redox in reaction system.3. Dilacunary silicotungstate as calalyst for the selective oxidation of alcohols with hydrogen peroxide in biphasic system.A dilacunary silicotungstate, K8 [γ-SiW10O36]·13H2O, catalyzed the selective oxidation of alcohols with 30% aqueous hydrogen peroxide. The reaction was carried out in an aqueous/oil biphasic system, which allowed easy recovery of catalyst under relative mild conditions. The high yields of ketones were obtained in oxidation of alcohols by the dilacunary silicotungstate and the catalyst was recycled five times without activity loss in the oxidation of cyclohexanol to cyclohexanone at room temperature.更多还原