Research On The Green Epoxidation Of Long Carbon-Chain Unsaturated Organic Compounds

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.