The Study On Photocatalytic Chlorination Of Aromatic Side Chians

Trichlorotoluene and 1,3-bis?trichloromethyl?benzene are important organic intermediates in pesticides,medicines,dyes and other fields,at the same time,the route of benzoyl chloride and isophthaloyl chloride synthesized by them as chlorinating agents has industrial advantages such as high atomic utilization rate,good product quality,and low cost.Therefore,the synthesis of high-quality and high-yield trichlorotoluene and1,3-bis?trichloromethyl?benzene is of great significance.In order to obtain high-quality and high-yield trichlorotoluene,the subject deeply studied the mechanism of toluene photochlorination,and optimized the process of photochlorination of toluene to produce trichlorotoluene through experiments.The better process conditions were obtained that the reaction temperature is 100°C,the solvent is benzyl trichloride;the light source is a 25 W blue light;the mass ratio of solvent to toluene is 1:1;the flow rate of chlorine is 200ml/min and the reaction time is 6 hours.Under this reaction condition,the yield of trichlorotoluene exceeds 98%,and the target product with a purity of more than 99%can be obtained by simple vacuum distillation.Benzoyl chloride was synthesized from the prepared high-purity trichlorotoluene,and the performance of trichlorotoluene as a chlorinating agent was verified.The reaction kinetics of 1,3-bis?trichloromethyl?benzene prepared by meta-xylene photochlorination was studied,and the relevant reaction kinetic parameters were obtained.Then,guided by the results of the kinetic studies,the process of photochlorination of m-xylene to 1,3-bis?trichloromethyl?benzene was optimized through experiments,and better reaction conditions were obtained that the solvent is benzyl trichloride,the light source is a 15 W blue light,the mass ratio of the solvent to m-xylene is 1:1,the chlorine flow rate is divided into two stages,the first stage is V₁=110 m L/min?the reaction time is about 15 hours?,and V₂=100 mL/min?about 9 hours of reaction?,the reaction temperature is divided into three stages,the first stage T₁=100°C?the reaction time is about 2.5 hours?,the second stage T₂=130°C?the reaction time is about 10 hours?,Finally T₃=125??about 11.5 hours of reaction?and the total reaction time is about 24 hours.Under this reaction condition,the target product yield can reach 95.1%.Finally,a preliminary exploration was made on the method of purifying 1,3-bis?trichloromethyl?benzene,and it was found that it was more efficient to purify the substance by recrystallization.And the high-purity 1,3-bis?trichloromethyl?benzene was subjected to acid chloride to verify its performance as a chlorinating agent.