Paired Electrosynthesis Of Benzaldehyde And 2,2'-dichiorohydrogenazobenzene

With the rapid development of society,chemical industrial products have an impact on people's lives.However,in the process of preparing these products will inevitably produce some toxic and harmful substances;the environment governance has brought enormous challenges.In order to solve this problem,green chemistry has attracted widespread attention.As an indispensable part of green chemistry,organic electrochemistry was mainly based on electric energy.In the process of electrolysis,almost no toxic and harmful substances were produced,and the pollution to the environment was relatively small.Compared with the traditional chemical synthesis method,it has the characteristics of simple operation,high product purity,few by-products,environmental friendliness and higher economic efficiency.Benzaldehyde and 2,2'-dichlorohydrogenazobenzene are important fine chemical intermediates.Among them,benzaldehyde is widely used in medicine,dyes and spices.2,2'-dichlorohydrogenazobenzene is mainly used in the dye industry and is an important intermediate for the synthesis of yellow organic dyes.However,the traditional production processes of these two substances have a relatively large environmental pollution.Based on the literature review,it was found that both of these materials can be electrolyzed under alkaline conditions,and the reaction conditions are relatively similar.Therefore,benzaldehyde is prepared by using a green clean paired electrosynthesis technique,namely,anodic electrooxidation of benzyl alcohol.The cathode is electrically reduced to o-chloronitrobenzene to obtain 2,2'-dichlorohydrogenazobenzene,and two products with higher added value are simultaneously obtained in one electrolytic cell.The experimental contents are as follows:Firstly,the NiOOH electrode was prepared on the basis of literature review and the research of this group.The properties of the newly prepared electrode were investigated.The cyclic voltammetry curves of NiOOH electrode and foamed nickel electrode were compared under the same conditions.The NiOOH electrode has higher catalytic activity.Next,2,2'-dichlorohydrogenazobenzene was electrolyzed under alkaline conditions using an activated Pb electrode as a cathode and a self-made NiOOH electrode as an anode in an H-type diaphragm electrolytic cell.The effects of electrolysis conditions such as the amount of o-chloronitrobenzene added,electrolysis temperature,current intensity and solvent type on the cathode current efficiency were investigated by orthogonal experiment.The experimental results showed that the cathode current efficiency was low at 40.02%.Further investigation of the literature found that the addition of catalyst lead oxide can improve the catalytic efficiency,and the foamed nickel electrode was more prone to hydrogen evolution reaction than the Pb electrode.Therefore,the cathode electrode material was changed,the Pb electrode was replaced with a foamed nickel electrode,and lead oxide was added to the electrolyte,and the amount of o-chloronitrobenzene added,the amount of NaOH added,the reaction temperature,the current intensity,and the ethanol volume fraction on the cathode current efficiency were investigated by orthogonal experiments.The experimental results showed that the current efficiency of the cathode electrode material was higher than that of the Pb electrode,which was up to 87.71%.The optimum experimental conditions were 0.4 g of lead oxide and 0.6 g of o-chloronitrobenzene.The amount of NaOH added was 0.8 g,the reaction temperature was 60 °C,the current intensity was 0.12 A,and the volume fraction of ethanol was 15%.Third,by consulting the literature,the commonly used quantitative detection method for the cathodic electrolysis product o-chloroaniline or 2,2'-dichlorohydrogenazobenzene was high performance liquid chromatography.This method was simple and accurate,and the results were accurate and efficient.Therefore,in this experiment,a high performance liquid chromatography method for simultaneous determination of cathodic electrolysis products was established by changing the flow rate,column temperature,and detection wavelength and flow ratio.The optimal chromatographic conditions were: 245 nm was selected as the detection wavelength,and the flow was the phase was 70% methanol solution,the flow rate was 1.2 mL/min,and the column temperature was 30 °C.This condition is used for the electroreduction of the product of 2,2'-dichlorohydrogenazobenzene and by-products in the reaction of o-chloronitrobenzene.The analytical recovery of chloroaniline and the remaining raw material o-chloronitrobenzene was between 91.3%~109.9%,90.9%~103.0% and 92.3%~109.7%,respectively.Fourthly,the foamed nickel electrode was used as the working electrode,the NiOOH electrode was used as the auxiliary electrode,and the saturated calomel electrode was used as the reference electrode.The electrochemical behavior of o-chloronitrobenzene was investigated in 0.5 mol/L NaOH solution,and the scanning rates were investigated for the electrical reduction process.The experimental results show that the electrochemical reaction of o-chloronitrobenzene on the foamed nickel electrode is controlled by adsorption.A pairing experiment with anodized benzyl alcohol was carried out under the premise of maximum cathode current efficiency.In the H-type diaphragm electrolyzer,the self-made NiOOH electrode was used as the anode and the foamed nickel electrode was used as the cathode to optimize the electrolysis conditions of the cathode.The reaction temperature,NaOH addition amount and benzyl alcohol were investigated by orthogonal experiment and supplementary experiment.The effect of the amount added on the total current efficiency.The results showed that 0.4 g of lead oxide,0.6 g of o-chloronitrobenzene,0.8 g of NaOH and 15% by volume of ethanol were added to 40 mL of catholyte at the electrolysis current intensity of 0.12 A and the reaction temperature of 60 °C.And 40 mL of anolyte were added with 0.05 mol of benzyl alcohol and 2.5 g of NaOH respectively.The cathode current efficiency was 90.65%,the anode current efficiency was 72.11%,and the total current efficiency was over 162%.