Study On Kinetics Of Toluene Sulfonation And Sulfonation Process In Rotating Packed Bed

The application of p-toluenesulfonic acid in the field of medicine and chemical industry is particularly extensive,and it can also be used as a catalyst for the synthesis of esters and an intermediate for the synthesis of some important organic compounds.It is mainly obtained by sulfonating toluene with concentrated sulfuric acid or SO₃.Among them,the liquid-phase SO₃sulfonation process has the characteristics of good atom economy,easy temperature control,high conversion rate,not easy to oversulfonate and coke,and it is also the mainstream process for producing p-toluenesulfonic acid at present.However,the SO₃sulfonation process is a fast exothermic reaction,and the traditional reactor has problems such as low yield and many side reactions caused by limited transfer.In this paper,taking advantage of the Hi Gee technology to enhance the rapid micromixing and heat distribution of the liquid-liquid reaction system,combined with the external circulation heat transfer,a new process for the synthesis of p-toluenesulfonic acid using SO₃sulfonation with external circulation heat transfer process in a rotating packed bed is proposed,so as to improve the selectivity and yield of p-toluenesulfonic acid.The main contents are as follows:1.The reaction mechanism of SO₃sulfonated toluene was revealed.Using DFT method to calculation,and it was confirmed that the mechanism of the sulfonation process is that the toluene is directly sulfonated by two molecules of SO₃to generate pyrosulfonic acid,and pyrosulfonic acid react with toluene to generate toluenesulfonic acid.2.The kinetic model of SO₃sulfonation reaction with toluene was established.In view of the fast and strong exothermic characteristics of this reaction,the kinetics of SO₃sulfonated toluene in the microreactor was studied.Through experimental and theoretical analysis,it was found that the reaction was a first-order reaction of toluene and a second-order reaction of SO₃,and the kinetic equation of the sulfonation reaction was obtained.3.The process research of SO₃sulfonation of toluene in the rotating packed bed was carried out.Using the Hi Gee external circulation sulfonation process,the liquid-phase SO₃diluted with dichloromethane was used as the sulfonating agent.The influence of sulfonation process parameters such as SO₃/toluene molar ratio,reaction temperature,SO₃concentration,feed flow rate,on the reaction effect in the sulfonation process of liquid-phase SO₃and toluene in a rotating packed bed was studied.the optimal process operating parameters were obtained.Under the optimal conditions,the selectivity of p-toluenesulfonic acid was 94.82%,and almost no sulfone was generated.