Study On Feasibility For Reactive Distillation Using Graphical Method

Reactive distillation (RD) is a process combining reaction and separation in a single apparatus, which presents numerous advantages-improved efficiency, low energy consumption and capital investment. However, the complex interaction between reaction and separation in the same device makes the design and control of the process much more difficult than it is for conventional reactors or distillation processes. Therefore, it is significant to develop a design methodology to clearly describe the feasibility in RD.The residue curve mapping (RCM) technique has traditionally been considered as a powerful tool for preliminary design of RD processes. For its application, this method just requires a minimal set of information concerning the physicochemical properties of the system and the result can be considered as an initial value for the fourth step of the design procedure. In this article, the RCM design strategy of RD process is proposed and the ternary and quaternary cases of acetic esters are studied. The detailed research contents of this thesis are as follows:(1) The concepts of reaction space、transformed composition variables、singular point and reactive azeotrope are introduced. On this basis the design feasibility equation of rRCM and reactive extractive curve maps (rExCM) technique is derived, and the corresponding feasibility-based rules are analyzed. Subsequently, the RCM design strategy of RD feasibility analysis and synergistic mechanism between reaction and separation is put forward.(2) The esterfication reaction kinetics of sec-butyl acetate is studied with the catalyst CT800 to provide kinetic foundation for RD graphical design process. Under the elimination of the internal and external diffusion effects, the effects of temperature, proportion of raw material and catalyst concentration on the reaction are investigated. A pseudo-homogenous model is established. The relationship between the reaction rate constant and the temperature is obtained, and the activation energy of the forward reaction and the reverse reaction are determined. The reaction equilibrium constants are also estimated.(3) Based on the proposed RCM design strategy, combining a set of information concerning the physicochemical properties, the RD column design is researched in the systems of methyl acetate hydrolysis and sec-butyl acetate synthesis to validate the reliability of the method. The strategy is to determine the process feasibility and separation limit, meanwhile the fundamental structure of RD is obtained, and the Damkohler number is applied to analyse the synergistic mechanism between reaction and separation.