Feasibility and multiplicity in reaction-distillation processes for systems with competing irreversible reactions

Several important technical reaction systems consist of competing irreversible reactions of the type A + B --> C and A + C --> D, in which C is the product and D is an undesired byproduct. To produce C from A and B, a conventional process using a reactor coupled with a distillation column to recycle unreacted educts can be used. An alternative is reactive distillation. In the present paper, a simple mathematical model for the conventional reaction + distillation process is developed (second-order reaction kinetics + infinity/infinity -analysis of the distillation column). This model is used to comprehensively investigate the feasibility and multiplicity of the process, a task which would be too time consuming using rigorous simulators. The entire range of different combinations of process variables which allow a desired selectivity (C/D) to be obtained is explored and it is shown for which combinations of input variables which types of multiple solutions (output) will occur. As all solutions are obtained analytically, it is possible to give a complete picture of the stationary system behavior including all transitions between the different types of solutions. An interpretation of the different kinds of multiplicity observed in the present process is given. The basic features of the solutions presented here should also hold for the reactive distillation process. (C) 2000 Elsevier Science Ltd. All rights reserved.