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Ethylene Glycol Synthesis

RD may also be a favorable alternative if complex reactions comprising consecutive and parallel reaction steps are considered. A prototypical reaction system for further study is the synthesis of ethylene glycol (EG) from ethylene oxide (EO) and water (W) according to h2o + c2h4o ^ c2h6o2 , c2h6o2 + c2h40 ^ C4H10O3 .

The first reaction leads to the desired product whereas di-ethylene (DEG) and higher order glycols are formed in consecutive reactions as undesired by-products. The reaction rate constants of the consecutive reactions are higher than that of the main reaction. Hence, an appropriate process has to be devised in order to achieve satisfactory conversion and selectivity.

A number of studies have been carried out to investigate RD as an alternative to the classical process comprising a reactor-separator-recycle [14, 16, 79]. According to our own investigations [24], which have also been confirmed by industrial studies [92], ethylene glycol synthesis by RD is not a viable economical alternative to a reactor-separator-recycle process with a tightly heat-integrated separation system. Nevertheless, the ethylene glycol process may be considered a model problem to facilitate the study of nonlinear dynamics in RD with complex reaction networks. Subsequently, we only consider the first two reaction steps thus resulting in a mixture of four components with volatilities decreasing in the sequence EO, W, EG, and DEG. The mixture does not form any non-reactive azeotrope.

As in the case of the esterification process presented before, we study first a one-stage column by singularity analysis to gain some physical insight and then continue with a numerical bifurcation study of an industrial size RD column.

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