The Studies On Kinetics And Thermodynamic Properties Of Isoamyl Benzoate

The process conditions of isoamyl benzoate,the kinetics of esterification and the solubility of benzoic acid in alcohol are studied in this paper.Isoamyl benzoate was produced by direct esterification with benzoic acid and isoamyl alcohol as raw materials and PTSA as catalyst.On the basis of orthogonal experiment,the effects of reaction temperature,amount of PTSA and acid alcohol ratio on the yield of isoamyl benzoate were studied.The results showed that the effect of factors is in the order as below:the reaction temperature>the amount of PTSA>the ratio of acid and alcohol.The optimal condition is shown when the reaction temperature is 110 ?,n(benzoic acid):n(isoamyl alcohol):n(PTSA)= 1:3:0.105,and the yield of isoamyl benzoate is 97.23%.On the basis of references,a five step carbon cations mechanism which is suitable for this reaction is proposed,and the mechanism is explained in detail.By introducing power function model and activity coefficient,the rate equation of the esterification reaction is established.The mole fraction of isoamyl benzoate at four temperatures of 353.15K,363.15K,373.15K and 383.15K was determined by experiments,and the default values of the rate equation were estimated by fitting MATLAB software algorithm.The heat capacity of benzoic acid and isoamyl benzoate(288.15-393.15)K were determined by adiabatic calorimeter,and the relationship between Cp and T was obtained with MATLAB.At the same time,the equilibrium constants of each reaction temperature were calculated from the experimental data.According to Van't Hoff equation,the standard enthalpy ?H0 of synthesis of isoamyl benzoate was calculated by linear fitting which proved that the reaction was exothermic.Meanwhile the changes of Gibbs free energy ?rGeo at various temperatures are calculated by using thermodynamic functions.In the temperature range of 288.15-336.15K,the solubility of benzoic acid in isobutanol,n-pentanol,isoamylol,2-pentanol,tert-Amyl alcohol and n-hexanol was measured by the dynamic method.The ?h model?the Modified Apelblat equation?NRTL and Wilson model were adopted to correlate the solubility data.The results showed that the overall relative average deviations of these four models are all less than 1.5%which fully illustrates that the thermodynamic model is very suitable for the two element solid-liquid system of benzoic acid and alcohol.The NRTL equation was used to calculate the ?disHo,?disSo??disGo of benzoic acid in the dissolution process.