Study On Ultrasonic/Hydrodynamic Cavitation Field Enhancing The Toluene-water Alkylation Reaction To Produce Ethylbenzene

In response to the fact that the domestic market for toluene is relatively saturated while the ethylbenzene/styrene is in short supply,and in order to optimize the existing ethylbenzene synthesis technique which has complicated process,high reaction temperature and pressure,as well as poor stability of the catalyst,this paper comes up with a new method of producing ethylbenzene by using the cavitation filed to enhance the toluene alkylation reaction.It provides a new idea of ethylbenzene synthesis technique and also lays a foundation for the industrialization of this method.The research contents and results are as follows:This paper,taking toluene-water as the research system on the basis of ultrasonic cavitation principle and combining the analysis of cavitation products,deduces the reaction process and verifies the related results.In this paper one-factor experiments are made to show the effects on the product distribution by adding different amount of toluene,ethanol and H₂O_2.The results of the experiments also prove the correctness of the deduction of the mechanism.Then,the optimized process conditions of producing ethylbenzene by toluene alkylation are determined through response surface methodology and one-factor experiments,that is,when the adding amount of toluene 20%and of ethanol 12.5%,with ultrasonic power at 850 W,ultrasonic time for 90 min and pH at 6,the optimized yield of ethylbenzene is 34%.By optimizing the Venturi Tube model,the effective cavitation distance is increased from12.22 mm to 134.53 mm.In the simulation of the ultrasonic cavitation field,it is found that the ascending period of the ultrasonic horn is the generation stage of the ultrasonic cavitation,during which the cavitation field exists in the low pressure zone because the ultrasonic horn is moving,and the pressure is 0.03 MPa,and there is a vertical upward velocity of 0.6 m/s right below the ultrasonic horn;on the other hand,the collapse of the cavitation occurs during the descending period of the ultrasonic horn,and at the moment there is a high pressure and high speed zone under the ultrasonic horn,with pressure up to 1.55 MPa and speed up to 0.6 m/s,and direction going down.Regarding to the calculation of dissociation energy and the transition state search,it is inferred according to the calculation of dissociation energy of the deduced experiment-related reaction equation that the energy required to dissociate·H from toluene is the highest,that is 517.4 k J/mol,which means the hydrogen on the methyl group of toluene is not easily dissociated.This shows the methyl group on toluene is active and easily dissociated.By transition states search and activation energy calculation of the related reactions,it is known that the activation energy required by ethylbenzene which is generated from benzyl radical and methyl is 208.8 k J/mol,and the activation energy for the generation of ethylcyclohexane from ethylbenzene and·H is 598.3 k J/mol,which indicates that this reaction is the most difficult.