Electrosynthesis And Its Mechanism Of Iron Methoxide

As a metal alkoxide, iron methoxide is an important intermediate for the electrochemical synthesis of ferrocene, which has a wide range of applications in medicine, aerospace and environmental protection and etc. Compared with the traditional chemical synthesis of ferrocene, the electrosynthesis has the advantages of simple process, high product purity and less waste, represents the development direction. Therefore, the study of electrosynthesis of iron methoxide has a guiding significance for the efficient electrosynthesis of ferrocene. However, the detailed kinetics and mechanism of cathodic and anodic reactions, and their dependence in the electrosynthesis of iron methoxide, are not clear. In this thesis, the three scientific issues were investigated. The thesis is divided into 3 parts:In the first part of the thesis, the electroreduction kinetics and mechanism of pure iron in a typical nonaqueous deoxygenation electrolyte ?NaBr methanol solutions? were studied in details by polarization curves and the electrochemical impedance spectroscopy ?EIS?, in a standard three-electrode system using iron as the working electrode, platinum mesh as the counter electrode, saturated calomel ?SCE? as the reference electrode. The results show that the reactant is methanol and the sodium ion functions only as a conductor. The product contains sodium methoxide and hydrogen is formed according to the Faraday's law. The electrode potential is the only state variable in the system, and its effect on the rate constant of methanol reduction follows to the Arrhenius phenomenological equation with an activation energy-26.2 kJ·mol-1; No diffusion but ohmic polarization was observed during the reduction of methanol.In the second part of the thesis, the electro-oxidation kinetics and mechanism of pure iron in NaBr methanol deoxidization solutions were investigated by polarization curves and EIS in a standard three-electrode system using iron as the working electrode, platinum mesh as the counter electrode, SCE as the reference electrode. The results show that the anodic oxidation of iron exhibits an electrode process ?the electrode potential is the only state variable? at low potentials, and the number of reaction electrons n ? 2, the product is mainly ferrous ions with the Faraday efficiency of more than 90%. The solution ohmic polarization is the main form of total polarization. With the continual dissolution of the anode, the process of cation diffusion resistance occurs.In the third part of the paper, the effect of current density, electrode distance and supporting electrolyte concerntration on the cell voltage was studied for the galvanostatic electrolysis of iron in a single-compartment cell with NaBr methanol deoxidization solutions. The relationship between the cathodic and the anodic reaction and the mechanism of electrosynthesis was examined as well. The results show that the cell voltage was increased with the increase of the current density or electrode distance, and the decrease of the supporting electrolyte concerntration. At low current densities, the initial reaction rate of the cathode is smaller than that of the anode, so it is the main influencing factor of the cell voltage. With the continuous electrolysis, the anode polarization was increased, while the cathodic polarization was reduced due to the diffusion of ferrous ions to the cathode surface. Whereas the increase by the former is higher than that decreased by the later, so the cell voltage was increased as a whole, indicating that the main influencing factor of cell voltage was converted from cathode reaction to anode reaction. The IR spectrum analysis showed that iron methoxide was produced. Combining the previous results, we speculate that the mechanism of iron methoxide synthesis may be as follows:Cathode reaction:2CH₃OH+2e^-?2CH₃O^-+H₂?Anode reaction:Fe ? Fe²⁺+2e^- Fe²⁺+2CH₃O^-? ?CH₃O?₂Fe+2Na⁺...