Reaction and Product Separation

Reactive distillation is the name given to the process where the chemical reaction and product separation are carried out simultaneously in one unit. Carrying out the reaction, with separation and purification of the product by distillation, gives the following advantages ... 

In the ideal biphasic hydrogenation process, the substrate will be more soluble or partially soluble in the immobilization solvent and the hydrogenation product will be insoluble as this facilitates both reaction and product separation. Mixing problems are sometimes encountered with biphasic processes and much work has been conducted to elucidate exactly where catalysis takes place (see Chapter 2). Clearly, if the substrates are soluble in the catalyst support phase, then mixing is not an issue. The hydrogenation of benzene to cyclohexane in tetrafluoroborate ionic liquids exploits the differing solubilities of the substrate and product. The solubility of benzene and cyclohexane has been measured in... 

Hall et alP discuss the use of cross-corrugated membrane modules, illustrated in Figure 20.24, as offering the potential for developing multi-functional units for performing both reactions and product separation in one miniaturised module. The use of microporous... 

Gavalas, G. R., C. Megiris and S. W. Nam. 1989. A novel composite inorganic membrane for combined catalytic reaction and product separation. Chem. Eng. Sci. 44(9) 1825L-35. 

Whereas the unit operation concept of chemical engineering asks for a clear separation of educt preparation. chemical reaction and product separation in different units, it is obvious that better conversion and selectivity might be achieved if educts arc added at the required amount and intermediates or products arc withdrawn from the place of reaction immediately Two general alternatives arc presently under discussion to achieve this goal, membrane methods and sorptive methods The basic difference is that membrane... 

M. Onda, L. Lvov, K. Ariga, T. Kunitake, Sequential Reaction and Product Separation on Molecular Films of Glucoamylase and Glucose Oxidase Assembled on an Ultrafilter , J. Ferment. Bioeng., 82, 502 (1996)... 

The conversion could be enhanced for the forward reaction if the reverse reaction involving ethene and 2-butene is minimized. Further, since 2-butene desorption is a controlling factor due to its strong sorptive properties, 2-butene removal, in particular, will allow improved rate of reaction and product separation with the use of a sorbent such as y-Al203. The effect of the PSR operation (cycle time = 40 sec) on the reactor performance was tested through simulations and by conducting experiments. Step inputs in inlet feed composition containing propene with helium carrier were conducted with clean sorbent beds and constant total gas flow rates. The results, compared with theoretical predictions, are shown in Fig. 9. Because ethene has... 

Fig-1 Sim ultaneous reaction and product separation (two liquid phases). 

Figure 1 Simultaneous (a) and successive (b) reaction and product separation.

If a development engineer has to design an industrial column purely on the basis of miniplant experiments, he has to maintain not only the separation performance but also the ratio of separation performance/reactor performance so that main and secondary reactions proceed to a comparable extent in the industrial-scale reaction column. One way in which this can be achieved is in terms of construction by separating reaction and product separation from one another both in miniplant tests and on an industrial scale. This is possible, for example, when the reaction is carried out in the presence of a heterogeneous catalyst in the downcoming stream or with side reactors at the column. An alternative is to use structured packing with well-defined paths for the liquid flow. This problem has not yet been solved, the main reason being the lack of reference columns on an industrial scale. As we see it, the way forward is either ... 

The selective oxygenation of methane and light alkanes (Ci-Cj) by the Fe(II)/H202 Fenton system was performed in the three-phase catalytic membrane reactor, enabling simultaneous reaction and product separation. Frusteri et al. reported that Nafion-based catalytic membranes catalyze the selective oxidation of... 

Combining OCM reaction and product separation in a simulated countercurrent moving bed chromatographic reactor where a series of high-temperature catalytic reactors operating at low conversion and low-temperature separation columns with adsorbent are interconnected [39-41]. Yields of C2 hydrocarbons up to 50% can be reached under optimal conditions. However, such reactor operation is very complicated and the different temperature levels for the reactor and separation units are costly. Therefore, at present it has low chance to be applied in industry. 

Using knowledge bases of the type mentioned in Section 4.2 these systems propose economic alternatives for chemical processes. The. systems start with basic information about the chemical reaction system, available raw materials and data about the desired products and their quality. Based on these data they allow development of a complete process including raw material preparation, chemical reaction and product separation. ... 

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