| Butyl propionate is widely used in food and fine chemical industry,and has the aroma of apricot and peach,which is an important basic chemical raw material and food essence.At present,the Butyl propionate is mainly produced by the esterification of propionic acid and n-Butanol catalyzed by the concentrated sulfuric acid in industrial.And after separation process,the high-purity butyl propionate was obtained.There are many problems in this process,such as concentrated sulfuric acid will corrode the equipment and the process will pollute environment.And the water generated by esterification forms a variety of azeotropes with other components,which is difficult to separate.There is an urgent need to find high-quality catalysts and efficient synthesis technology.Candida antarctica lipase B（CALB）,as a biological enzyme,has the advantages of high efficiency catalysis and regeneration.It has a great application prospect in the catalytic transesterification reaction.Reactive distillation with side reactors,which not only integrates the high efficiency and economic advantages of reactive distillation process,but also takes into account the characteristics of not resistant to high temperature of biological enzyme catalyst,is favored by researchers.In this paper,the kinetics experiment of transesterification reaction was carried out with immobilized CALB—Novozym 435 as catalyst and ethyl propionate and n-Butanol as raw materials.Under the conditions of rotating speed of 480 rpm,initial ester alcohol ratio of 2:1,catalyst dosage of 10 wt.%（n-Butanol）and reaction temperature of 343.15 K,the reaction equilibrium was reached in about 105 min,and the conversion of n-Butanol at reaction equilibrium was about65.97%.The transesterification reaction between ethyl propionate and n-pentanol was used as a control to verify the accuracy of the experiment.And the catalyst still has more than 93.98%catalytic activity after 10 times of use.Based on the kinetic experiments,the fitting effects of IQH（Ideal Quasi Homogeneous）model,LHHW（Langmuir Hinshelwood Haugen Watson）model and enzyme catalytic reaction kinetic model based on King-Altman method on experimental data were investigated.The kinetic parameters were solved by 4-5order Runge-Kutta algorithm.LHHW model and the King-Altman enzyme catalytic model have better fitting effect,and the mean absolute scaled errors（MASE）are 7.00×10-7 and 1.20×10-7.The fitting results of transesterification reaction between ethyl propionate and n-pentanol showed that changing the sampling time and temperature range would not affect the fitting effect.Based on the fitting results,and the King-Altman enzyme catalytic model is difficult to input in Aspen Plus software,the LHHW model is used as the kinetic basis to simulate reactive distillation with side reactors.Through side line extraction,the liquid phase on the pedal of the distillation tower is connected to the side reactors for reaction,and then transported back to the tower for separation,which not only avoids the inactivation of the enzyme at high temperature,but also easy to loads the catalyst.In five side reactors,there are five trays between the side reactors.The optimum reaction conditions are as follows:in five side reactors,there are five trays between the side reactors,the lowest side reactor corresponds to the 38th tray,n-Butanol is fed on the fifth tray,ethyl propionate is fed from the fifth side reactor,the reflux ratio is 2,the ratio of distillate to feed is 0.6,and the ratio of feed ester to alcohol is 1:1.The yield of butyl propionate recovered from the tower kettle is 83.35%and the purity can reach 99.99%.And provided a reference for practical production... |
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