Optimization single reactions

Single-reaction-step processes have been studied. However, higher selectivity is possible by optimizing catalyst composition and reaction conditions for each of these two steps (40,41). This more efficient utilization of raw material has led to two separate oxidation stages in all commercial faciUties. A two-step continuous process without isolation of the intermediate acrolein was first described by the Toyo Soda Company (42). A mixture of propylene, air, and steam is converted to acrolein in the first reactor. The effluent from the first reactor is then passed directiy to the second reactor where the acrolein is oxidized to acryUc acid. The products are absorbed in water to give about 30—60% aqueous acryUc acid in about 80—85% yield based on propylene. 

In a similar transformation using 4-hydroxycoumarin (2-781) as the 1,3-dicar-bonyl compound the cycloadduct 2-794 was obtained also in good yield. In order to demonstrate the general applicability of this process, a small library using substituted pyruvate was prepared without optimizing the reaction conditions for the single transformations. a-Ketonitrile can also be used, though with a much lower yield. 

Vayenas, C. G. and S. Pavlou. 1987a. Optimal catalyst distribution and generalized effectiveness factors in pellets single reactions with arbitrary kinetics. Chem. Eng. Sci. 42(11) 2633-2645. 

The two requirements, small reactor size and maximization of desired product, may run counter to each other. In such a situation an economic analysis will yield the best compromise. In general, however, product distribution controls consequently, this chapter concerns primarily optimization with respect to product distribution, a factor which plays no role in single reactions. 

We noted earlier that chemical engineers are seldom concerned with single-reaction systems because they can always be optimized simply by heating to increase the rate or by finding a suitable catalyst [You don t need to hire a chemical engineer to solve the problems in Chapter 3]. Essentially aU important processes involve multiple reactions where the problem is not to increase the rate but to create a reactor configuration that will maximize the production of desired products while rninirnizing the production of undesired ones. 

Detailed knowledge of the reaction mechanisms and pathways of the reforming system can lead to optimization of reaction conditions, and catalyst design. Unfortunately, very meager information is available on the kinetics of liquid hydrocarbon reforming. Literature is limited mostly to kinetic studies of SR of single paraffinic components. 

R. Aris. Studies in optimization - IV The optimum conditions for a single reaction. Chem. Eng. Sci., 13 197, 1960d. 

As Table 10 illustrates, using this approach the authors were able to rapidly optimize the reaction conditions, obtaining the target 82 in 91% yield when employing 2 eq. of fenchone (80) and n-BuLi 74. In all cases only a single diastereomer was observed and the authors found that conducting the reaction at 0 °C resulted in a mere 3% reduction in yield. Furthermore, the reaction conditions were found to be suitable for a range of aliphatic/aromatic ketones and brominated compounds. 

The Disjoint Character of the Optimal Temperature Policy with a Single Reaction... 

In this chapter we pass from the discrete to the continuous deterministic process, and the difference equations derived for the stages now become differential equations. It is scarcely surprising to find many features of the discrete process are retained by the continuous process in particular we know from the work of Denbigh (1944), and will prove here afresh, that the optimal temperature policy is disjoint in the case of a single reaction. However, this simplicity is lost when more than one reaction is taking place and we shall do well to examine the simple consecutive system A B C with some care, as it opens up the principal features of the general case. 

OPTIMAL TEMPERATURE POLICY WITH A SINGLE REACTION... 

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