Mechanism And Prediction Model Of Microwave Induced Relative Volatility Change

Microwave has been widely employed in accelerating chemical reactions,intensifying purifications and seperations,as well as fabricating nano materials,due to its selective heating characteristics.Recently,the phenomenon of microwave induced relative volatility change（MIRVC）inspired the innovation of novel separation techniques.Therefore,the present study derived the theoretical model for describing MIRVC and then designed experiments to confirm the mocel accuracy,aiming to guide the development of novel microwave induced seperation techniques.In terms of theoretical analysis,a model was established to describe the phenomenon of microwave induced“microscopic hot spots”,revealing the mechanism of MIRVC.By introducing this model into the thermodynamic analysis,the present study derived a dimensionless number Z_MW to evaluate the influence of various parameters on MIRVC,including the microwave absorbing ability and the thermodynamic properties of materials as well as the microwave power.The Z_MWnumber can help build a quantitative model for predicting MIRVC.In order to validate the accuracy of the above models,the experimental studies were designed as follows.First,a fluorescent nano-thermometer was designed for probing the“microscopic hot spots”.Carbon particles with adjustable microwave absorbing properties and uniform sizeswere synthesized and then coated by microwave-transparent and thermally stable Europium/Terbium bimetallic organic complexes（ETB）.Based on the temperature-dependent fluorescence of ETB,a quantitative correlation was built between temperature and the characteristic peaks in the fluorescence spectra,which can be used to measure local temperature at microscopic scale.Next,the mechanism of MIRVC was validated by using the fluorescent nano-thermometer.The temperatures of solid particles and bulk liquid were measured via the temperature-dependent fluorescence of ETB and fiber optic,respectively.The temperature difference between the particles and bulk liquid directly confirmed the mechanism of“microscopic hot spots”.Besides,the fluorescence experiments agreed with the model predictions that the microwave induced temperature gradient can be enlarged by increasing the microwave intensity as well as the dielectric loss and the size of solid particles.Conversely,the increase in the thermal conductivity and the dielectric loss of the liquid solvents lowers the temperature gradient.Finally,the model parameters of MIRVC predicting model were determined by fitting experimental data obtained from vapor liquid equilibrium of binary systems under microwave irradiation.After obtaining the dielectric and thermodynamic properties of binary solutions,the vapor-liquid equilibrium data under microwave irradiation were predicted,and the error range between the model prediction and experimental values was within 6%.The present study then predicted the influence of microwave irradiation on the kinetics of esterification reactions,which agreed well with the experimental results,confirming the applicability of the MIRVC predicting model.