BTX Kinetics

Chapter 1, we introduced the BTX system and posed the following question  

How do we maximize the amount of toluene produced from a feed of 0.5 moles of ethylene and 1.0 moles of benzene  

Now that we have a full understanding of AR theory, we are in a better position to answer this question. Let us determine the point of maximum toluene concentration, and provide the optimal reactor structure required to achieve the point. 

We have already generated the AR in for this system in Chapter 3, where the procedure shown involved repeated use of batch (PFR) reactions followed by partial mixing with fresh feed for a subsequent batch. This process is somewhat lengthy and impractical in practice. 

For the full three-dimensional BTX system, we find that the AR construction procedure is similar to that for Van de Vusse kinetics. Hence, we can summarize the key steps as follows  

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AR—from scratch— using the BTX kinetics from Chapter 2 in the form of a worked example. The descriptions of the worked example work best when it is framed as a simple game, involving batch experiments, which enforce two rules that are related to the AR. The game is given as follows ... 

Consider again the familiar BTX kinetics. The system of reactions and kinetics are supplied again for convenience as follows ... 

Figure 8. A schematic for the toxin binding sites on the voltage-gated Na channel. Toxin-free open and closed conformations are drawn at the left and center. Separate sites are depicted within the membrane for activators such as BTX, VTD (A), and brevetoxin (B) these are coupled to each other and to the a-peptide toxin site (a), which is kinetically linked to the -peptide toxin site (P see ref. 20). Near the outer opening of the pore is a site (G) for STX and TTX which is affected by binding at site A and which can modify inactivation gating.

When used as a co-substrate, benzoate addition enhanced BTX degradation kinetics and attenuated BTX breakthrough relative to acetate-amended or unamended control columns. 

As Haber and Weiss (1934) suggested, at lower H202 concentrations and fixed Fe2+ the oxidation reaction approaches second order however, when the ratio of H202 Fe2+ increases, the reaction kinetic approaches zero order and the reaction process depends on the competition between hydroxyl radicals and superoxide radicals. If an excess of hydrogen peroxide is present, then the reactions as shown in Equation (6.123) and Equation (6.124) for 2,4-dinitrotoluene are dominant. The amount of H202 was used up quickly in this study, indicating the importance of Equation (6.123). At concentrations of Fe2+ greater than 600 mg/L, the DRE of BTX reached a maximum value at approximately 82% for benzene and toluene and 73% for xylene. 

No drastic change occurred in tail sodium current. When tetramethrin was added to the BTX-treated axon, a large and prolonged tail current characteristic of the tetramethrin modified sodium channel developed. Thus tetramethrin binds to a site different from the binding site of BTX which is located inside of the channel. This result is compatible with the hypothesis that the pyrethroid molecules bind to the channel gating machinery via the membrane lipid phase thereby altering the kinetics of channel gating. 

In Section 1.2, we described how Sam, Alex, and Donald approached the BTX problem from an experimental perspective. How might our approach change if we are given mathematical expressions for the rates of reaction In the following sections, we wish to describe some common ideas and approaches in theoretically designing a network of reactors (the reactor network synthesis problem), and also describe a central challenge faced in reactor network synthesis, even when mathematical and optimization techniques are available. For example, suppose that kinetics is also available for the BTX reaction and assumed to follow the data in Table 1.4 ... 

Observe that this set of reactions is similar to the BTX system presented in Chapter 1, if ethylene and hydrogen are omitted. The kinetics of both reactions in Equation 5.1a is first-order irreversible, whereas Equation 5.1b is second-order irreversible. Thus, for component A,... 

Critical CSTRs Let us now investigate the existence of any critical CSTR points in the BTX system. The determination of critical CSTR points follows the proeedure given in Section 7.2.1.4 for Van de Vusse kinetics. We shall use the CSTR locus from the feed point in this analysis. 

Table 10. Some kinetic data obtained for BTX consumption at different denitrifying culture conditions.

Table 11. Kinetic data of BTX consumption at different concentrations of BTX mixtures at...

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