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Iron (Ⅵ) Chemistry: A Study On Green Oxidation For Organic Synthesis

Posted on:2006-01-29Degree:DoctorType:Dissertation
Country:ChinaCandidate:H SongFull Text:PDF
GTID:1101360155977286Subject:Oil and gas field development project
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The oxidation plays an important role in the industry of organic synthesis. The oxidative process is one of the main factors that cause the environmental pollution. The shortcomings of traditional oxidants, such as the oxides and compounds of Cr and Mn, are both lack of selectivity and rigorous control of the experimental conditions. Another drawback is that they are corrosive, and some are highly toxic to mankind and the environment. So for use of various green oxidants, such as oxygen, hydrogen peroxide etc, to replace the traditional oxidant becomes the key technique to realize friendly environment. The study on Fe(VI) compound is a new research field — Ferrate Chemistry. The research of Fe (VI) oxidant is one of the important branch of ferrate chemistry. Fe (VI) compounds are green, non-toxic, high selective and powerfully oxidizing agents. The oxidative ability is higher than that of KMnO4,O3 and Cl2, and could oxidize organic compounds such as alcohol, Organic compound containing nitrogen, even hydrocarbon etc. The oxidative behavior could be controlled by adjusting conditions such as temperature, pH, solvent, acid and catalyst. Fe is different from Cr and Mn. It is nontoxic, none pollutant chemical because its oxidation byproduct is iron rust, which has non harmful to human being and to the environment. Thus, it has bright developing prospect in oxidation and synthesis of organic substance. There are a lot of research reports about potassium ferrate (K2FeO4) used in water treatment and as the green battery material. But there are less attention focused on its application to organic synthesis. This dissertation investigated the Fe(VI) preparation method, solubility and stability in various kinds of media and decomposition kinetics in basic solution. The Fe (IV) preparation, stability and oxidation were also studied. As a model reaction by oxidizing benzyl alcohol to benzaldehyde, the activity control of K2FeO4 oxidant was systematically studied in water phase, organic phase and two phases. The reaction mechanisms that K2FeO4 oxidize organic substance in both water phase and organic phase were put forward. This work opened up a new way that can be followed for green synthesis of organic compounds by oxidation.This dissertation can be divided into three topics, which will be introduced as follows.1. Preparation and characterization of Fe(VI) compoundsAn improved method of hypochlorite oxidation (wet synthsis) was proposed. The highly pure K2FeO4 was prepared with potassium hydroxide, ferric nitride, chlorine in technical purity. The purity of K2FeO4 is in the ranges of 96% to 98.5%. The K2FeO4 was characterized by atom absorption spectrometry (AAS) X-ray diffraction (XRD), Fourier transform infrared spectrometry (FTIR) and scanning electron microscope (SEM). The results show that the Fe (VI) compound has molecular formula of K2FeO4 with a perfect crystallization.2. Solubility and stability of Fe(VI) compounds in various kinds of media(1) Solubility and stability of Fe(VI) compound in various kinds of mediaThe solubility of K2FeO4 in organic solvents such as hexane, cyclohexane, benzene, toluene, chloroform, etc. is far less than 105mol/L. The solubility of K2FeO4 in basic solution increases with decrease of temperature. The stability of K2FeO4 in air and organic solvents were studied, respectively. It was found that K2FeO4 is very stable both in air and in organic solvents. The effects of temperature, pH, Fe3+ and purity of K2FeO4 on stability of K2FeO4 in solution were researched. The stability of K2FeO4 reduces with rising of temperature, Fe3+concentration while the situation is reversible in increasing of K2FeO4 purity and pH. At first time, the stability was investigated when a certain amounts of sodium acetate, sodium oxalate or sodium phosphate were added into the aqueous solution, respectively. It was found that stability of K2FeO4 follows theincreasing order of sodium phosphate < sodium oxalate4 oxidant of 0.792g, temperature of 30°C and time of lh. At these conditions the yield of benzalhyde is 99.8%. The result is obviously superior to that of optimal reference data which benzaldehyde yield is 82.0% in 2h.In this dissertation, the innovative points are that (1) it was firstly found that the stability of K2Fe04 was remarkably increased with adding sodium acetate into aqueous solution. The richer the sodium acetate was, the stronger the stability of K2Fe04 was. (2) the application of oxidizing organic compounds by K2Fe04 was successfully extended from basic solution to organic phase. The problem which K2Fe04 couldn't dissolve in organic phase was solved by following three approaches. Firstly, a new method of adding acid to the organic solvent in the reaction of oxidizing organic compounds by K2Fe04 was put forward. Secondly, the reaction is catalyzed further more by adding ultrastable molecular sieve in addition of the acid. Thirdly, the SW-1 catalyst, which with green catalyst and excellent properties, was prepared on basis of the experiments. The yield with this catalyst is 99.8% within lh. The results are obviously superior to that of optimal reference data of 82.0% in 2h. The K2Fe04 oxidant even the added acids and SW-1, are green, and friendly environment. Therefore, the methods have high atom utilization ratio and economy. The work in this dissertation has general reference for the reaction of synthesizing organic compounds by K2Fe04 and can be applied to other fields. It approaches to green synthesis of organic substance by oxidizing.
Keywords/Search Tags:Green synthesis, organic oxidization, potassium ferrate, stability, benzaldehyde, benzyl alcohol
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