The Synthesis Of Anisaldehyde By Indirect Electrochemical Oxidation Using Mn(Ⅲ)/Mn(Ⅱ) As Redox Mediator

The indirect electrochemical oxidation of anethole to anisaldehyde with Mn(Ⅲ)/Mn(Ⅱ) as redox mediator system was studied in this thesis.The electrolytic technical conditions of electrochemical oxidation of Mn(Ⅱ) to Mn(Ⅲ),the kinetics of electrode process of Mn(Ⅲ)/Mn(Ⅱ) and chemical oxidation steps of anisaldehyde were investigated separately in order to determine operating conditions providing a high electrolytic yield and current efficiency of Mn(Ⅱ), and a high yield of anisaldehyde.The electrochemical oxidation experiments of Mn(Ⅱ) were performed in a non-membrane electrolytic cell. The pure lead with its moderately-priced and easy to be obtained,higher overpotential for oxygen evolution and quite good performance was attempted to be use as cathode and anode separately, also the technology of the electrochemical oxidation of Mn(Ⅱ) to Mn(Ⅲ) was optimized.The continuous current electrochemical oxidation was carried in 100ml electrolyte solution containing 5.5 mol/L H2SO4+0.15 mol/L MnSO4.When using the current density of 50 mA/cm2 with the area ratio of cathode to anode 1:6 at the temperature of 40℃for 2h, the electrolytic yield of Mn(III) reaches as high as 95.6%, also the current efficient of 64.1% is obtained. After the regeneration cycle use of the redox mediator for 10 times the electrolytic yield of Mn(II) can still reaches 89.0%.The kinetics of electrode process of Mn(III)/Mn(II) in sulfuric acid were investigated with conventional electrochemical ways.The electrochemical behavior of Mn(III)/Mn(II) in sulfuric acid on lead and platinum electrode was reviewed with cyclic voltammogram and linear sweep polarization separately. The results of experiments show that the medium of electron transfer was Pb(Ⅱ) on the electrode surface, Pb(Ⅱ) was oxidated to PbO2 first, then Mn(Ⅱ) was oxidated by PbO2 to Mn(Ⅲ), but not Mn(Ⅱ) completed the charge exchange with electrode directly on the lead electrode; however, Mn(Ⅱ) completed the charge exchange directly on the platinum electrode, the electrode reaction is quasi reversible controlled by mixing process of diffusion and charge-tranfer.The chemical oxidation process of Mn(Ⅲ) oxidating anethole to anisaldehyde was carried out by reviewing the effects of factors on the yield of anisaldehyde through orthogonal tests.The optimized result is the synthesis operation in 6.3mol/L sulfuric acid solution in which ratio between Mn(Ⅲ) and anethole is 1:1 at the temperature of 30℃in the presence of benzene.Under the optimum conditions,the yield of reaction reaches 89.9%.