Nonequilibrium dynamic modeling of a simple batch reactive distillation

The irreversible model developed in this work was applied to calculate reactive residue curve maps (RRCMs) for a simple batch reactive distiller. This rigorous nonlinear modelling can describe the design and operation issues for a reactive distillation (RD) process better than equilibrium models because the interaction between mass transfer and chemical reaction is substantially complex. Methyl tert-butyl ether (MTBE) is the classic reference compound in the reactive distillation literature and thus was chosen for the case study in the present work. The irreversible model represented by differential–algebraic equations (DAE) was solved by the Runge–Kutta method for stiffness problems. Interesting phenomena are demonstrated with a case study for production of MTBE by a simple batch RD of the non-ideal mixture isobutene/methanol/methyl tert-butyl ether. The resulting complex nonlinear dynamics led to important results such as the phenomenon of dynamic azeotropy and multiplicity of steady states. The Damköhler number and operational parameters such as the interfacial area and vapor withdrawal flow rate can manipulate the topology of RRCMs. Relative to the equilibrium model, new distillation regions, new binary and ternary azeotropic points and new distillation boundaries (separatrices) were observed. The thermodynamic equilibrium model was demonstrated to be a limiting case of the proposed modeling which can be obtained by increasing the interfacial area or through decreasing the vapor withdrawal rate in the nonequilibrium model. The results obtained are useful for improving the design and the evaluation of batch RD columns.