Reaction-operator strategy

FIGURE lA Example of a reaction-operator strategy carried out by changing two snbstrates. 

When more than one reactant is involved, the relative yields of reaction products will depend on a greater number of variables. Then it is not usually possible to deduce the best operating strategy by simple inspection of the reaction scheme. Under these circumstances, it is worthwhile developing a formalised procedure for choosing the best reactor and operating conditions. Reaction selectivity is discussed in more detail below. 

The major conclusions from the above-described studies are consistent in the asymmetric mode of operation the reaction zones of the exothermic and endothermic reactions inherently repel each other, leading either to an extreme maximum temperature or to poor performance. A noncontinuous heat supply and production during every other semicycle cause obviously strong fluctuations of operation. Moreover, reasonable states of operation are attainable only with an excess of gas during the exothermic semicycle. This contradicts the condition of equal heat capacities for optimal heat recovery (see Section 1.2.1.1). For example, the heat loss in the case displayed in Fig. 1.9 is equal to the heat demand of the endothermic reaction. Different strategies have been assessed with regard to their potential to reduce hotspots during the exothermic semicycle and to improve thermal efficiency. 

Figure 11.6 Optimum operation strategy for a parallel reaction A unreacted A is recycled.

Other work (Malik et al., 2004) has focused on the various factors (which are suspected to limit the coal biodesulfurization process rate) on bacterial oxidation of ferrous iron. An attempt has been made to find whether this reaction is inhibited due to the presence of solid particles and/or the release of inorganic components from solids during coal biodesulfurization. The data showed that silicon was responsible for retarding the central step of iron oxidation during coal biodesulfurization. Consequently, operational strategies, which tend to minimize the concentration of toxic inorganic components in the leachate, would be a better option than conventional batch process for enhanced biodesulfurization. 

NO2 SCR compositions, superior NOx conversion performance was achieved with the layered architecture. The schematic shown in Fig. 11.17 explains the concept while Fig. 11.18 provides typical data for several monolith samples. The catalyst design and operating strategy was to exploit differences in the intrinsic activity and selectivity of the two catalysts through coupled reaction and diffusion. At low temperature the top layer should behave in the limit as simply as a diffusion barrier, whereas at high temperature the top layer should be sufficiently active so as to confine most of the conversion in that layer. This was of definite benefit because at low temperature, the Fe layer was much less active than the underlying Cu layer which was selective for N2, while at high temperature reaction occurred in the more selective Fe top layer. 

This chapter reviews the possibilities that the application of a membrane in a catalytic reactor can improve the selectivity of a catalytic oxidation process to achieve a more compact system or to otherwise increase competitiveness. Classification differentiates between those reactors using dense membranes and those using porous membranes. Dense membranes provide high selectivity towards oxygen or hydrogen and the selective separation of one of these compounds under the reaction conditions is the key element in membrane reactors using such membranes. Porous membranes may have many different operation strategies and the contribution to the reaction can be based on a variety of approaches reactant distribution, controlled contact of reactants or improved flow. Difficulties for the application of membrane reactors in industrial operation are also discussed. 

Most processes are catalyzed where catalysts for the reaction are known. The strategy will be to choose the catalyst, if one is to be used, and the ideal characteristics and operating conditions needed for the reaction system. Decisions must be made in terms of reactor... 

Moderate means using materials under less hazardous conditions, also called attenuation. Moderation of conditions can be accomplished by strategies which are either physical (lower temperatures, dilution) or chemical (development of a reaction chemistry which operates at less severe conditions). 

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