Research On The Increase Of Microwave To Homogeneous Reaction Rate And Kinetic Model

Microwave heating method has the characteristics of accelerating reaction rate,changing the selectivity,increasing the yield in the chemical reaction,which cannot be replicated by other method.Therefore microwave heating method has attracted much attention in inorganic,organic,polymer,metal organic,material chemistry.Microwave irradiation heating technology is widely applied in a variety of fields,but the interaction mechanism of microwave and chemical reaction has not been elucidated,which seriously restricts the further application of microwave technology in the chemical industry.Chemical reaction kinetics research is a strong and comprehensive tool that could reveal the influence of microwave energy on chemical reactions,and the kinetic model established by the kinetic results is beneficial to the amplification process of the chemical industryIn the case of chemical reactions run in homogeneous solution,particularly organic reactions,the exact reason for the accelerated reaction rate of chemical reactions has always been controversial and remains unknown.Thermal effect has been accepted by a majority of researcher,but non-thermal effect still a research hotspot in the field of microwave chemistry In this paper,the effect of microwave radiation on the chemical reaction is quantitatively revealed by comparing the kinetic results of chemical reaction under conventional heating and microwave heating method.Comparing the activation energy of the reaction under the two heating methods,the microwave non-thermal effect is deeply studied,and the mechanism of microwave non-thermal effect is discussed and clarifiedDimensional analysis method has widely been used in different kinds of fields,which is an effective method to establish mathematical model in chemical engineering research.It can reasonably simplify complex practical problems and express it in the form of mathematical correlation.This method does not require advanced mathematical method,but it can obtain results that other methods can not complete.When expressing a process via a mathematical model,we need to follow the principle of dimensional consistency which dimensional analysis is based on.With research and analysis,the microwave irradiation heating process is generated between microwave and material,and the independent physical quantities that associated with this process are microwave power densityp,dielectric constant ε,viscosity,u,density p,reactant concentration CA and dipole moment η,irradiation frequency f.After analyzing the kinetics of the reaction,the difference between the reaction rate constant Δ(-rA)was used to quantify the acceleration effect of the non-thermal effect in the chemical reaction.A mathematical model capable of correlating Δ(-rA)with multiple physical quantities was designed via dimensionless dimensional analysis.Ultimately,the mean relative error(MRE),mean absolute error(MAE),and root mean square error(RMSE)were used to evaluate the performance of the model.The model form is as follows:Δ(-rA)=K(PCA2/μ)1/2(Pρ3η2/εμ5)α’(μf2/P)β’Statistical indicators reflect the relative gap between the estimated value of the model and the experimental value,showing that the mathematical model has a certain predictive ability,and indicating that the model has certain reliability.However,the error of partial data is relatively large,so the mathematical model needs to be improved to be more and more in line with the realities.(1)Azobisisobutyronitrile(AIBN)decomposition reactionThe activation energy of the AIBN decomposition reaction under the conventional heating method was 124.27 KJ·mol-1.The activation energy at 200 W,300 W,400 W and 500 W were 103.95 KJ·mol-1,110.47 KJ·mol-1,102.58 KJ·mol-1,96.76 KJ·mol-1,respectively.Compared with the conventional heating method,the activation energy was reduced by 20.32 KJ·mol-1,13.80 KJ·mol-1,21.69 KJ·mol-1 and 27.51 KJ·mol-1.The mathematical model was established by dimensional analysis and regression fitting was carried out on the experimental data.The results of the model parameters were as follows:K=6.44×10-249,α’=5.44,β’=6.67.The statistical indicators were:MRE=1.49,MAE=1.36×10-6,RMSE=2.31×10-6.(2)Azobisisobutyrazine hydrochloride(AIBA)decomposition reactionThe activation energy of the AIB A decomposition reaction under the conventional heating method was 139.42 KJ·mol-1.The activation energy at 200 W,300 W,400 W and 500 W were 104.82 KJ·mol-1,104.99 KJ·mol-1,98.59 KJ·mol-1,94.97 KJ·mol-1,respectively.Compared with conventional heating method,the activation energy had been reduced by 34.60 KJ·mol-1,34.43 KJ·mol-1,40.83 KJ·mol-1,and 44.45 KJ·mol-1.The mathematical model was established by dimensional analysis and regression fitting was carried out on the experimental data.The results of the model parameters were as follows:K=1.90×10-260,α’=6.23,β’=6.69 The statistical indicators were:MRE=0.58,MAE=3.67×10-6,RMSE=6.06×10-6(3)Quaternarization reaction of N-m ethyl diethanolamine(MDEA)and bromododecaneThe activation energy of the quaternarization reaction of MDEA and bromododecane under conventional heating method was 107.16 KJ·mol-1.The activation energy at 200 W,300 W,400 W and 500 W were 88.07 KJ·mol-1,87.94 KJ-mol-1,89.50 KJ-mol-1,88.06 KJ·mol-1,respectively.Compared to conventional heating method,the activation energy were reduced by 19.09 KJ·mol-1,19.22 KJ·mol-1,17.66 KJ·mol-1,and 19.10 KJ·mol-1,respectively.The mathematical model was established by dimensional analysis and regression fitting was carried out on the experimental data.The results of the model parameters were as follows K=2.34×10-24,α’=-0.10,β’=1.48.The statistical indicators were:MRE=1.85,MAE=2.30×10-6,RMSE=3.06×10-6.Because of microwave heating method,the activation energy of the organic reactions mentioned above were lower than that under traditional heating method.It means that Microwave irradiation can promote the reaction and change the reaction kinetics.Accordingly,non-thermal microwave effect existed in the system,besides the thermal effect.In this paper,the reaction mechanism of the non-thermal effect was studied,and the non-thermal effect can be envisaged to possess multifarious causes.For a homogeneous chemical reaction process,if the polarity increases when changing from the ground state to the transition state,the reactivity is increased by reducing the activation energy of the reaction which could promote the reaction The non-thermal effect result from the interactions between molecules and microwaves irradiation.If the polarity of the reaction molecules is greater than that of the solvent molecules,it will cause the orientation effect of the dipole molecules,and due to the phenomenon of dipole polarization in high-frequency electromagnetic fields,the molecules polarity will increase,which means that the non-thermal effect will be more pronounced.