Study On The Synthesis Of Quinolinic Acid By Electrochemical Oxidation Of Quinoline

Quinolinc acid, a significant pesticide, pharmaceutical pigment and dyeintermediate, can be used to synthesis of p-fluoroethoxybenzene, moxifloxacin,imidazolinone herbicides and quinoline antibiotics. With high efficiency and lowtoxicity, imidazolinone herbicides synthesized by quinolinic acid tend to replacetraditional product and is highly valued in the world. Currently methods for preparingquinolinic acid include traditional chemical oxidation and direct electrochemicaloxidation. Compared with the traditional chemical oxidation, direct electrochemicaloxidation is characterized by high yield and high purity of the target product, lowcast, reduced waste, etc. and it is favored by many scholars. In this paper, quinolineis used as raw material in the electrochemical synthesis of quinolinic acid. The mainresearch contents are the quantitative analysis of synthesis reaction liquid, research onelectrocatalytic performance of the cathode material and selection, optimization ofprocess conditions, which have certain theoretical significance and a good industrialapplication prospect.In the electrochemical synthesis process of quinolinic acid, the reaction solutionwere mixtures of quinolinic acid, the intermediate product oxalic acid, unreactedquinoline, sulfuric acid and water. The analysis is not yet reported. In this paper, highperformance liquid chromatography was used to determine the quinolinic acid andquinoline in the reaction liquid at the same time, and it is a new method forquantitative analysis.The anode is the catalyst and a reaction field for electro-catalytic reaction.According to the properties of the electro-synthesis process of quinolinic acid, thecatalytic activity of Ti/PbO2、Pb/PbO2、Ti/IrO2、smooth Pt anodes in oxidizingquinoline process were investigated by steady-state polarization curve. It was foundthat the Ti/PbO2anode exhibited better electro-catalytic activity and corrosionresistance, and can be applied in the electro-synthesis of quinolinic acid. The kinetic parameters and apparent activation energy in oxidizing quinoline process weredetermined.In this study, using Nafion427perfluorinated sulfonic cation-exchangemembrane as membrane, Ti/PbO2as anode and Pb as cathode, the technologyconditions for synthesizing quinolinic acid were optimized in the plate and frameelectrolyzer. Under the conditions of catholyte sulfuric acid concentration20%,flow-rate8L·min-1and distance between anode and cathode5mm, by usingorthogonal design and mono-factor experiment, the optimum technological conditionswere as found that the electrical charge was1.1times of theoretical value, currentdensity was239A·m-2, solution temperature was60℃, anolyte sulfuric acidconcentration was60%and total concentration of quinoline was6%by batch feedingmethod. Under the optimum technological conditions, the results of four times repeatexperiments show that the current efficiency is above69%and the yield of quinolinicacid is above76%. In addition, effects of different factors on the post treatmentprocess were investigated by using mono-factor experiment. Under the optimumprocess conditions, the total yield of quinolinic acid was71.2%with the purity of98.2%.