| 2,5-dichlorophenol is an important chemical raw material.It can be applied to medicines,pesticides,etc.It is an important intermediate and has a huge market demand.Electrochemical synthesis has received extensive attention from researchers due to its mild reaction conditions,simple process flow,no additional addition of redox reagents,strong reaction control,and environmental friendliness.The anode material is the core part of the organic electro-oxidation reaction,and it is a key factor influencing the electrolysis.The titanium-based Sn-Ir oxide electrode has the advantages of good conductivity,high electrocatalytic activity,low cost,and availability,and has a wide range of applications in electrocatalytic oxidation of organic compounds.This first studied the effects of different current densities,different solvent compositions and ratios,different electrolysis temperatures,and different separators on the electrochemical synthesis of 2,5-dichlorophenol,and the optimal electrolytic conditions are sought.Secondly,a titanium-based Sn-Ir oxide electrode was prepared by brushing thermal decomposition method.The electrode was doped with Tb,Pr,Gd,Eu,and Ce.The electrode was characterized by EDS,SEM and XRD,and accelerated life test was used.The electrode performance was studied by means of cyclic voltammetry,polarization curves,and AC impedance.The effect of the electrode in the electrooxidation of 1,4-dichlorobenzene to prepare 2,5-dichlorophenol was investigated by galvanostatic electrolysis.Get the following research results:?1?When platinum is used as the anode,the optimum conditions for the preparation of 2,5-dichlorophenol by electrooxidation of 1,4-dichlorobenzene are:1,4-dichlorobenzene as raw material,in trifluoroacetic acid:triethylamine=1:1?volume ratio?,a polypropylene separator was used,the current density was 7.5 mA·cm-2,and the reaction temperature was 20°C.Based on these conditions,the primary conversion rate was 46%and the current efficiency was 39%.?2?The prepared Sn-Ir oxide electrode coatings can all cover the titanium substrate surface,but cracks and black holes appear on the surface.As the content of Sn in the electrode coating decreases,the content of Ir increases,and cracks on the surface of the electrode increase.The surface of the electrode doped with rare earth metals such as Tb,Pr,Gd,Eu,and Ce has more fine particles and the electrode coating is more dense.With the increase of Ir content,the life of the electrode increases.After the modification of rare earth,the accelerated life is improved up to 112.5h(current density 10 A·cm-2).The titanium-based Sn-Ir oxide electrode with Sn:Ir of 80:20 has excellent stability and good electrocatalytic activity.The rare earth metals doped electrodes such as Tb,Pr,Gd,Eu,and Ce have better stability and electrocatalytic activity.?3?Compared with platinum electrodes,commercial chlorine-evolving electrodes?AC11-02?,and oxygen-evolving electrodes?AO09?electrodes,titanium-based Sn-Ir oxide electrodes have superior electrocatalytic activity and are more suitable for electrolytic preparation of 2,5-dichlorophenol.In the experiment of electrosynthesis,the yield can reach 40%,the selectivity can reach 85%,and the conversion rate of 1,4-dichlorobenzene can reach 47%.?4?The Sn-Ir oxide electrodes doped by doping with rare earth metals such as Tb,Pr,Gd,Eu,and Ce have excellent electrocatalytic activity,and 0.5%Gd-doped tin-bismuth oxide electrodes are used in electrolysis.The preparation of 2,5-dichlorophenol has a better effect in the experiment,with a yield of up to 44%,a selectivity of 88%,and a conversion rate of 50%. |
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