Synthesis of reaction-separation systems

The synthesis of reaction-separation systems. The recycling of material is an essential feature of most chemical processes. The use of excess reactants, diluents, or heat carriers in the reactor design has a significant effect on the flowsheet recycle structure. Sometimes... 

Finally, we consider a preliminary approach for the optimal synthesis of reactor-separation systems. Here, we formulate a combined reaction-separation model by postulating a species-dependent residence time distribution. The optimization of this distribution function leads to a separation profile as a function of time along the reactor. The costs for maintaining a separation profile are handled through a separation index, which models the intensity of separation,... 

SYNTHESIS OF REACTION AND SEPARATION SYSTEMS FOR BATCH PROCESSES... 

Balakrishna, S. and L. T. Biegler. A Unified Approach for the Simultaneous Synthesis of Reaction, Energy and Separation Systems. Ind Eng Chem Res 32 1372-1382 (1993). 

In the following, a number of integrated reaction-separation systems wiU be discussed, with emphasis on the application of polymeric membranes. As a result, the systems discussed will be Hmited to relatively low temperatures, typically below 120°C. In Section 13.2, appHcations of membranes in chemical synthesis will be described. Subsequently, in Section 13.3 various examples of membrane bioreactors will be discussed. 

This chapter discusses the application of MINLP methods in the synthesis of reactor networks with complex reactions and in the synthesis of reactor-separator-recycle systems. 

Section 10.2 describes the MINLP approach of Kokossis and Floudas (1990) for the synthesis of isothermal reactor networks that may exhibit complex reaction mechanisms. Section 10.3 discusses the synthesis of reactor-separator-recycle systems through a mixed-integer nonlinear optimization approach proposed by Kokossis and Floudas (1991). The problem representations are presented and shown to include a very rich set of alternatives, and the mathematical models are presented for two illustrative examples. Further reading material in these topics can be found in the suggested references, while the work of Kokossis and Floudas (1994) presents a mixed-integer optimization approach for nonisothermal reactor networks. 

S. Balakrishna and L. T. Biegler. A unified approach for the simultaneous synthesis of reaction, energy and separation systems. Ind. Eng. Chem. Res., 3 1372,1993. 

The economic potential may be used to optimize the flowsheet with respect to the material balance. After Level 4 the mass-balance envelope is closed by completing the synthesis of reaction and separation systems. The economic potential EP4 becomes ... 

As one last example of the separations system synthesis method, a process was being developed to produce the chemical diethoxymethane (DEM), the ethanol acetal of formaldehyde. The raw materials are paraformaldehyde and ethanol, and the reaction by-produces water. Diethoxymethane, ethanol, and water form a homogeneous ternary azeotrope that is readily removed from the reaction mass (the paraformaldehyde being relatively nonvolatile). The species allocation... 

During the second stage, an irreversible ion exchange reaction with a solid-phase separation occurs (condensation method synthesis of a dispersed system). Therefore, it is possible to influence the granulometric composition of the antiagglomerator suspension by varying the reaction conditions of the calcium stearate and calcium chloride interaction. 

The same catalytic system used for the synthesis of monocarbamates can also be used for the synthesis of ureas, once aniline is substituted for ethanol and dioxane is used as solvent [188], but the efficiency of the reaction is lower. Under the best experimental conditions (PhN02 (10 mmol), PhNHa (11 mmol), molar ratios PhN02/Pt = 100, SnCLi/Pt = 10, EtjN/SnCU = 1.8, 140 °C, 60 Kg/cm CO, in dioxane (20 ml) for 4 h) a 65 % yield of diphenylurea was obtained. As in the case of the synthesis of dicarbamates, separate values for the conversion and the selectivity were not reported. Note that the catalytic ratio in these experiments is 100, whereas the one in the synthesis of carbamates was 200, although the temperature was also higher in that case (180 C). As for the synthesis of monocarbamates, FeCb (37 % yield) and AICI3 (27 % yield benzene was used as solvent) could also be used as promoters in place of SnCU, but showed lower activity. Despite the large excess of the basic aniline, the presence of EtsN was still essential for the reaction to proceed. Upon decreasing its amount, a drop in yield was observed. 

Pharmaceutical appUcations of the polymeric membranes refer to the obtaining of pure and ultrapme water for pharmaceutical usage, treating the used water for pharmaceutical usage, membrane reactors for the synthesis of medicine, separation of enantiomers, controlled release systems of the pharmaceutical substances which are active in the organisms, molecifiarly printed membranes for the chromatographic separations, and separation of the reaction products from medicine synthesis. 

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