A combination of DFT and kMC to solve two engineering problems in the production of vinyl acetate

Abstract

Vinyl acetate is one of the important chemical raw materials for the production of polyvinyl alcohol and polyvinyl acetate, and ethylene gas phase process is one of its mainstream production processes. In the industrial production of vinyl acetate, the kinetic equations needed for reactor design are usually obtained by experimental methods. In addition, it was found that the production of CO2 increased significantly at the last stage of the reaction. This abnormal phenomenon is often explored and solved through experiments. The use of experimental and simulation methods to verify and assist each other can better solve the problems in practical application. Based on the existing experimental research, we try to use the method based on the combination of density functional theory and kinetic Monte Carlo to obtain the reaction kinetic equation and explore the reasons for the significant increase of CO2 at the last stage of the reaction. By studying the effects of temperature, partial pressure of ethylene and oxygen on the formation rate of vinyl acetate and CO2, the kinetic equation of the main reaction is rVA=58.4exp(−8732RT)pC2H40.17pO20.15. The kinetic equation of the side reaction of CO2 formation is rCO2= 8.43 × 103exp(−28447RT)pC2H4−0.16pO20.61. In addition, it was found that the significant increase of CO2 at the last stage of the reaction was caused by the acceleration of the oxidation rate of acetic acid. Therefore, in the actual process design, it will be considered to reduce the feed amount of acetic acid at the last stage of the reaction, so as to reduce the formation of CO2. It is hoped that our research can provide some reference and guidance for the acquisition of reaction kinetic equations and the interpretation and solution of some abnormal phenomena in actual industrial production.