| Abstract: | The effects of diffusional water removal and heat transfer on the polymerization of ε-caprolactam were investigated by solving the systems of differential mass and energy balance equations using a finite difference method. Two types of contacting scheme between inert gas and reaction mass have been chosen for study. One is a hollow sphere system and the other is a wetted-wall type hollow cylinder system. The reaction system was designed to be in equilibrium with respect to monomer conversion. The interfacial area per unit volume and the diffusional depth have profound effects on the water content and the temperature of the reaction mass, and consequently on the molecular weight of the polymer produced. Larger interfacial area per unit volume and smaller diffusional depth lead to a higher rate of water removal and heat transfer. In case of larger interfacial area per unit volume, the higher interfacial temperature gives rise to higher molecular weight polymer. For the interfacial area per unit volume of 26.67 m2/m3, the number average chain length reaches as high as 277 and the polydispersity as high as 2.06 when the interfacial temperature is 270°C. The heat transfer greatly affects the content of cyclic dimer in the product so that the hollow cylinder type reactor is preferred, because it is easier to control the temperature of the later portion of the reactor. |
