Electrolysis Of Potassium Ferrate Preparation, Characterization And Application In The Synthesis Of Aldehydes Oxidation Study

In this paper, the physical characteristics, preparing methods and the application of ferrates (Ⅵ) were summarized. The influence of various technological parameters on electrolytic preparation of Fe(Ⅵ) were studied and the structure of K₂FeO₄ were analyzed. Finally, the application of K₂FeO₄ on synthesizing aldehyde compounds were investigated.K₂FeO₄ is stable enough in dry environment and can be used as water treatment agent, disinfectant, selective oxidant, and so on. However, the application of K₂FeO₄ was restricted due to the poor yields of synthesizing methods. So the influence of the ratio of 14 mol·L-1 NaOH and 13.5 mol·L-1 KOH in electrolyte and other electrolytic conditions were studied in the second chapter of this dissertation. The anode dissolution behaviors of iron lattice in mixed solutions were also investigated by means of EIS and CV technique. At last, the morphology and structure of K₂FeO₄ were characterized by appling the techniques of SEM, XRD and IR. The experimental results are as follows: (1) A highest current efficiency over 90% can be obtained at 45 ?C, a current density of 5 mA·cm-2 in mixed electrolyte with the volume ratio of NaOH and KOH is 6: 4 electrolyzed 2.5 h. (2) In the passivation region, the surface oxide film of the iron electrode in mixed alkaline electrolyte has higher activity of electrochemical dissolution reaction. The oxide film can be easily oxidated to Fe(Ⅵ) with the electrode potential shifting positively. The kinetic characteristics can be described according to the transpassive dissolution mechanism. And it was also found that the EIS data can be explained qualitatively by this characteristic which validates the rationality of the reaction mechanism in a certain extent. (3) The morphology of K₂FeO₄ prepared in optimal electrolytic conditions is prism or gobbet. The characteristic absorption peak of Fe-O bond appeared at 810 cm-1 in the IR spectra and the product contains impurities, such as Fe2O3 and KOH.K₂FeO₄ has showed many advantages in the filed of selective oxidation of synthesizing organic compounds. However, the research in this aspect is still at an initial stage. So in the third chapter of this dissertation, the selective oxidation of benzylamine and benzylethanol using K₂FeO₄ as oxidant were investigated, which offer basic data to K₂FeO₄ oxidating aldehyde compounds. Results show that a highest yield of 70.1% of benzaldehyde was obtained at conditions of the original pH of the solvent is 7, temperature 5℃, reaction time 5 min, and the dosage of K₂FeO₄ is two times of theoretic reaction requirements. The yield of benzaldehyde increased by 28.5% when using cetylpyridinium bromide as catalyst and the dosage of the catalyst is 1/4 times of that of K₂FeO₄. In addition, the optimal yield of phenylacetaldehyde is 78.5 % at conditions of temperature 30℃, reaction time 7 min, the initial pH of the solvent is 11.5, and the dosage of K₂FeO₄ is 1.5 times of theoretic reaction required. The yield of phenylacetaldehyde reached 96.4% when the dosage of hexadecyl-trimethyl-ammonium bromide is 1/5 times of that of K₂FeO₄ added. K₂FeO₄ oxidate amine and alcohols have different optimal conditions due to the different reaction activity on reactant.