【作者】 陈旻；

【导师】 蒋平平；

【作者基本信息】 江南大学 ， 应用化学， 2010， 硕士

【摘要】 环氧化合物是一大类化学品生产的重要原料,所以环氧化反应的研究有着十分重要的意义。但是传统生产过程会产生大量的羧酸废水,引起严重的环境污染。上世纪90年代中逐步发展起来的绿色化学从原理和方法上给传统化工生产带来了显著的变化,是目前化工特别是精细化工研究的热点。本论文以绿色化学的基本原理和思路为指导,对植物油脂环氧化过程进行研究。论文首先对铼催化体系催化环氧化植物油脂的过程进行了研究,针对传统方法中需要用到羧酸的不足,采用甲基三氧化铼为催化剂替代传统方法需要用到羧酸,减小了对环境造成的污染并且环氧化选择性和转化率都在99%以上。此催化体系最大的特色是助剂对环氧化效果的影响,它在反应体系中主要起调节Lewis酸中心pH的作用。通过紫外-可见分光光度法(UV-Vis)对催化剂的研究,发现催化剂在催化环氧化过程中形成催化活性很高的催化中间体,然后催化中间体提供氧给双键,形成环氧键。论文第三部分考察了钨、锰催化体系的催化环氧化效果。首先合成出两种含钨催化剂,利用红外光谱、核磁共振手段对合成的含钨催化剂结构进行了表征。结果表明催化剂结构中有过氧钨酸结构存在,并且推测其为进行环氧化的有效结构。然后研究了单因素变化对钨催化体系催化环氧化植物油脂过程的影响,其中最关键的是pH的影响,环氧化过程的最重要的催化中间体在一定pH范围内浓度最大,将有助于环氧化效果的提高。双十八烷基过氧磷钨酸盐的催化环氧化效果是最佳,反应的选择性和转化率可以90%以上。提出了铼、钨等副族过渡金属化合物催化环氧化的前线轨道机理:反应的本质是过氧化官能团中的RUMO轨道σ*(O-O)与长碳链的不饱和有机化合物中的HOMO轨道π(C-C)的重叠。最后对锰催化体系催化油脂进行了研究,发现其环氧化的转化率较低:不到50%,所以此催化体系不适用于长碳链不饱和化合物的催化环氧化反应。论文的第四部分通过建立动力学的研究模型,研究了传统甲酸催化方法和铼、钨催化体系催化方法的动力学和热力学,反应的活化能的排序如下:过氧磷钨酸盐(51.15±0.28 kJ/mol) >甲酸(44.85±0.18 kJ/mol) >甲基三氧化铼(31.17±0.14 kJ/mol);棉籽油<大豆油<葵花油,脂肪酸甲酯<大豆油。与传统的甲酸法相比,新型催化方法具有以下优点:不使用羧酸,提高操作的安全性,不会产生酸性废水,很大程度上降低了对环境的污染;反应条件温和,反应速率快,催化效率高;反应副产物仅为水,环氧化反应选择性和转化率较高。同时为其它长链不饱和碳碳有机化合物环氧化反应提供了一种绿色环保、有效的合成方法。更多还原

【Abstract】 Epoxidation plays a significant role since epoxides are useful intermediates for the production of a range of chemicals. Traditionally, epoxidation processes have hazards associated with handling the peracids and serious pollution on an industrial scale. Since 90 years of the last century, significant changes have been brought to principles and methods of the traditional chemical industry by green chemistry. In this paper, epoxidation process of vegetable oils was researched on the basis of principles and ideas of green chemistry.Firstly, epoxidation process of vegetable oils catalyzed by methyltrioxorhenium was studied. Using methyltrioxorhenium as the catalyst instead of carboxylic acid can overcome shortcomings of the traditional method. And it could reduce the pollution on the environment. Besides, selectivity and conversion of the epoxidation was above 99%. The most prominent feature of this catalytic system is additive effect, which regulates the pH of Lewis acid. It was found that the catalytic intermediates with a high catalytic activity were formed in the epoxidation process through studies on the UV-Vis spectrum of the catalytic system. Then catalytic intermediates provide oxygen to the double bond to form epoxy bond.Chapter 3 shows the catalytic epoxidation results of tungsten, manganese metal-catalytic system. Two kinds of tungsten metal catalysts were synthesized and characterized using infrared spectroscopy, nuclear magnetic resonance methods. The results showed that there was peroxo tungstic acid structure in the catalyst structure, which is the effective structure for epoxidation. The effects of reaction parameters on the epoxidation of soybean oil were then discussed in detail. The impact of pH was most crucial, as concentration of the most important catalytic intermediates was highest. Effect of expoxidation catalyzed by [(C18H37)2N(CH3)2]3{PO4[WO(O2)2]4} was best: a selectivity of 91.64% and a conversion of 94.62% were achieved. Frontier orbital mechanism of epoxidation of these oils with vice-family transition metal compounds (tungsten, methyltrioxorhenium and so on) occurred through the interactions between the oils unsaturated sites HOMOπ(C-C) and the unoccupied peroxoσ*(O-O) orbital. Epoxidation of vegetable oils by manganese had been investigated in the end, results showed that conversion of manganese-catalyzed system in epoxidation is relatively low, so this catalytic system unsuitable for epoxidation of the long-chain unsaturated compounds.The kinetics and thermodynamics of the epoxidation of vegetable oils by traditional route (formic acid) and new routes (peroxophosphatotungstate, methyltrioxorhenium) with aqueous hydrogen peroxide were investigated in Chapter 4. The mathematical model that described the kinetics of epoxidation was developed. Kinetic and thermodynamics parameters were estimated by fitting experimental data using the linear fit method. The activation energy for the epoxidation reaction decreased in the following order: peroxophosphatotungstate > formic acid > methyltrioxorhenium; rapeseed oil < soybean oil < sunflower oil, fatty acid methyl ethers < soybean oil.Compared with traditional method, the new methods have advantages as follows: It is not only safe for operation but also reducing the discharge of acid waste water. The novel epoxidations are mild, quick and efficient reactions, and by-product of the reaction is only water. Selectivity and conversion of epoxidation are quite high. In addition to these, it also provides a green and efficient synthetic method of epoxidation for other long-chain unsaturated carbon-carbon organic compounds.更多还原