Study On Coupling Technology Of Extractive Distillation And Catalytic Distillation In Hydrolyzation Of Methyl Acetate

A new technology of methyl acetate (MeOAc) hydrolysis was studied in this paper, which was put forward on the basis of the catalytic distillation (CD) technology which has been successfully applied in the industrial hydrolyzation of MeOAc．The new technology was developed with combining extractive distillation tower and catalytic distillation tower to achieve coupling operation, so called "Coupling Technology of Extractive Distillation and Catalytic Distillation in Hydrolyzation of Methyl Acetate" (Short for Coupling Tech.)．It will realize the purpose to strengthen the process effect, simplify the flowsheet and improve the hydrolytic conversion of MeOAc．What is more, energy consumption and investment will be greatly saved．The process of Coupling Tech. was systematically studied in this paper by the experiments in laboratory and process simulations．Further more, a computer simulation of the technology flowsheet was finished in order to prepare for future application in industrial process．The main works are as follows:1．Three types of catalyst packing mode were investigated in detail including bales packing mode, alternate catalyst filling packing mode as well as its improvements and the newly developed tube packing mode．It is indicated that the "tube" packing mode is more efficient and more convenient for loading or unloading catalyst．2．Using azeotrope of MeOAc and methanol (Short for azeotrope) as feed, the experiments were carried out in a column of 35 mm diameter in which catalyst was packed in the "tube" mode．The experimental results demonstrate that the mole ratio of water to MeOAc (H2O/MeOAc) in the feed is the most important factor．The conversion of MeOAc (Conv.) increases remarkably as H2O/MeOAc increases．It is also indicated that the Conv. will be decreasing while increasing the space velocity (S), and that, the higher volume ratio of reflux to feed (L/F) will be helpful to the process of hydrolysis．Because of negative influence, the eligible L/F is proved to be less than 4．3．According to the changes of catalyst tube diameter and column setting, the experiments were carried out on three column structures．The results are as follows: feeding the azeotrope at the bottom of reaction zone is better than at the top for higher S; increasing the stripping section and the reaction zone will enhance the hydrolyzation process．4．The model of artificial neural network with modified back-propagated algorithm (BP) was applied to the process simulation of MeOAc hydrolysis．Based on a great quantity of experimental data, the simulation results are satisfactory．5．A mathematical model and its corresponding calculation method were established to simulate the hydrolyzation column．The calculated results of Conv. and the weight ratio of acetic acid to water (HAc/H2O) in the product of hydrolysis are in fair coincidence with the experimental data, proving that the simulation results are credible．6．The HYSYS emluator was applied to the flowsheeting simulations including the fixed-bed hydrolyzation technology, the CD technology and the Coupling Tech.．Based upon the least energy consumption, the suitable conditions for pilotscale experiment were put forward．That is, H2O/MeOAc is about 4.5, L/F about 3, so as to reach Conv. larger than 90% and HAc/H2O larger than 0.7．Concentrating the HAc by distillation together with electrodialysis, the energy consumption is less than the fixed-bed technology by about 20.7%．...