A Dimensionless Quasi-kinetic Model Study Of Microwave Chemical Reactions

Microwave radiation technology has unique advantages,such as fast reaction rate,less side reaction and energy saving,and has been widely concerned in the field of organic synthesis,and its application in industrialization is bound to be a trend.However,microwave technology has not been applied to the actual production process of quaternary ammonium salt.In industry,traditional heating is generally used to synthesize quaternary ammonium salt,which has a long reaction time,limiting its large-scale industrial production.At present,there is a lack of reaction kinetics model to guide the improvement and industrial scale-up of microwave quaternary ammonium reaction process,which makes it difficult to carry out process scale-up and industrial design.Therefore,the focus of this study is to establish a common quaternary ammonium reaction kinetics model,to provide scientific basis for the industrial application of microwave,accelerate the process of microwave industrialization.Scientific and reasonable design of microwave reaction device and process,so that microwave synthesis reaction under the condition of continuous continuous action.The effect of microwave on quaternary ammonium reaction was studied in boiling state,in order to ensure the consistency of temperature and the continuous effect of microwave under the two different heating methods of traditional heating and microwave heating,to study the quaternary ammonium reaction of microwave,and to provide theoretical support for the mechanism of microwave accelerating the reaction rate.In this paper,the microwave assisted synthesis of tetradecyl methyl dihydroxyethyl ammonium bromide with N-methyl diethanolamine and tetradecane bromide as raw materials,using different polar solvents:n-amyl alcohol,n-butanol,isobutanol,n-propanol as reaction solvents formed homogeneous system.The reaction was carried out at the boiling point of the mixed system and a series of dynamic data were obtained.The important influencing factors of microwave quaternization reaction were analyzed as follows:reaction temperature（t）,reactant concentration（C_A）,stirring speed（n）,density（ρ）,thermal conductivity（λ）,microwave frequency（f）,power density（P）and loss Angle tangent（tanδ）.The reaction kinetic model was determined by dimensional analysis as follows:（-r_A）=K×（nC_A）（（ρλT）/（P₂n₃））^α（f/n）^β（tanδ）^γThe model parameters were obtained as follows:K=8.80×10^-10,α=-0.257,β=-0.235,γ=-11.694 through nonlinear fitting of customized functions in Matlab.The estimated value of the model is in good agreement with the experimental value,and the correlation of the model is high.It can be seen that,within the error range,the model can predict the reaction process and product yield to a certain extent,so as to optimize the process parameters and improve the production of tetradecyl methyl dihydroxyethyl ammonium bromide.In order to investigate whether other quaternary ammonium reactions are suitable for the established dimensionless kinetic model of microwave chemical reaction,the synthesis kinetics of decyl methyl dihydroxyethyl ammonium bromide（DMDAB）and cetyl methyl dihydroxyethyl ammonium bromide（CMDAB）under microwave reaction was studied at boiling point temperature.Based on the experimental data of MICROWAVE synthesis of DMDAB and CMDAB,nonlinear fitting of Matlab custom function is obtained as follows:DMDAB microwave synthesis reaction kinetics model parameters:K=9.70×10^-9,α=-0.343,β=-297,γ=-7.562.The kinetic model parameters of CMDAB were as follows::K=6.70×10^-10,α=-0.453,β=-0.494,γ=-11.564.By comparing the estimated value with the experimental value,it is concluded that the estimated value of the model is in good agreement with the experimental value,and the correlation of the model is high.It is suitable for microwave synthesis of DMDAB and CMDAB in the same type of quaternary ammonium reaction.Within the error range,the established microwave reaction kinetics model of quaternary ammonium can predict the process of quaternary ammonium reaction and product yield to a certain extent,which is expected to guide the improvement of microwave assisted quaternary ammonium reaction,provide scientific basis for the industrial application of microwave,and accelerate the process of microwave industrialization.In order to promote the popularization and application of microwave synthesis technology in quaternary ammonium,under the premise of ensuring the consistency of temperature between traditional heating and microwave heating,N-decane methyl dihydroxyethyl ammonium bromide（DMDAB）,tetradecyl methyl dihydroxyethyl ammonium bromide（TMDAB）and cetylmethyl dihydroxyethyl ammonium bromide（CMDAB）were synthesized by traditional heating method at boiling point temperature.The yield and reaction rate constant of the product were compared between traditional heating and microwave heating.At the same temperature,the conversion rate of the reaction was significantly improved when microwave heating was applied.It can be seen that the application of microwave synthesis technology in quaternary ammonium reaction can shorten the reaction time and increase economic benefits.Further deepen the understanding of quaternary ammonium synthesis,and the development prospect of microwave-assisted synthesis in quaternary ammonium surfactant synthesis.