Summary

The potential applications of reactive distillation have been discussed extensively in the literature but it appears that ETBE synthesis has not been considered specifically. Studies of MTBE synthesis via reactive distillation and the inherent similarities between the MTBE and ETBE systems suggest that reactive distillation could be used to improve the reactant conversion and reduce the capital cost of ETBE synthesis equipment. However, ETBE production has not been investigated sufficiently to determine if there are specific design or operating requirements that make the synthesis unique. Practical and effective design methods for reactive distillation are required and further experimentation on reactive packings is warranted.

The thermodynamics and kinetics of the ETBE synthesis reaction have been studied sufficiently to provide satisfactory expressions for the equilibrium constant, rate constant and to develop a detailed model of the reaction. The information that is now available is in good order and suitable to be implemented within simulation models for reactors or reactive distillation.

There are examples in the literature of both steady state and dynamic models of reactive distillation, for several systems including MTBE synthesis. The majority of models utilise the equilibrium stage approach and the validity of the technique has been confirmed via comparisons of simulation results and experimental data. Rate-based modelling has also been attempted but the results indicate that the additional model complexity and the increased requirement for parametric data (e.g. mass transfer coefficients) are not justified by the superior realism which the approach engenders.

The subject of multiple steady states in reactive distillation has been widely covered in the literature and parallel investigations of ideal binary distillation and azeotropic distillation have significant implications for continuing research in this area. However, despite the recent attention, comprehensive and consistent explanations for all types of multiplicity have proved elusive. Clearly, further work is required to adequately explain and predict multiplicities for industrial purposes (e.g. the design, operation and control of reactive distillation columns).

Reports of experimental work on MTBE synthesis via reactive distillation have been restricted to bench-top equipment and there appears to have been no work on ETBE synthesis. Experimental studies are also required to validate the experimental evidence of multiple steady states in reactive distillation. The control of reactive distillation processes has been essentially ignored in the literature and the implications for operability and controllability of combining unit operations (i.e. reactor and separator) appears not to have been considered to date.

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