Yield series reaction networks

In all cases studied, the membrane reactor offered a lower yield of formaldehyde than a plug flow reactor if all species were constrained to Knudsen diffusivities. Thus the conclusion reached by Agarwalla and Lund for a series reaction network appears to be true for series-parallel networks, too. That is, the membrane reactor will outperform a plug flow reactor only when the membrane offers enhanced permeability of the desired intermediate product. Therefore, the relative permeability of HCHO was varied to determine how much enhancement of permeability is needed. From Figure 2 it is evident that a large permselectivity is not needed, usually on the order of two to four times as permeable as the methane. An asymptotically approached upper limit of... 

We can begin by computing the selectivities and yields for the series network in the CSTR versus the PFR first. Consider the simplest series reaction network ... 

In this chapter, we develop some guidelines regarding choice of reactor and operating conditions for reaction networks of the types introduced in Chapter 5. These involve features of reversible, parallel, and series reactions. We first consider these features separately in turn, and then in some combinations. The necessary aspects of reaction kinetics for these systems are developed in Chapter 5, together with stoichiometric analysis and variables, such as yield and fractional yield or selectivity, describing product distribution. We continue to consider only ideal reactor models and homogeneous or pseudohomogeneous systems. 

Frequently, several reactions proceed simultaneously, and consequently selectivity and yield in networks of parallel and series reactions with respect to a certain desired target component D are essential quantities. 

In the previous chapter, we examined series and series-parallel kinetics. The extent of mixing can have an effect on the selectivity to the various products in such reaction networks. The selectivity is the percentage of the products that are any one of the products. To compute the yield we take the product of the conversion and the selectivity. Thus the yield is a fraction of a fraction. 

MTHF. In brief, lA is converted into 2-methylbutanediol by a series of hydrogenation reactions (Fig. 10.1), which upon dehydration forms 3-MTHF (Choi et al., 2015 Stein et al., 2013). Although the production of MTHF from LA and lA seems to be a direct conversion, a number of routes are possible. For instance, the conversion of lA to 3-MTHF could have as many as 19 different routes (Stein et al., 2013). The best possible competing conversion pathways could be depicted by mathematical models for the reaction network flux analysis considering critical criteria, such as yield, mass, and energy efficiency (Voll and Marquardt, 2012). 

There are a number of caveats. The predictions about the reaction pathway provide many essentials of the sequence of steps and types of interactions that exist among the measured species of the network, but do not provide all of the details of the chemical mechanism. Common chemical knowledge, not used yet on purpose, may supply more details. Furthermore, because not all species in the network were measured, we do not predict the entire pathway but only the part specifically involving the measured species. The fact that the calculation yields a reasonable pathway in the absence of full information is a strength of the analysis. Analyses currently under development are concerned with better estimates of the dependence of variation in one variable on variation in the others and detecting the presence of members of the network that are missing from the time series. 

We discussed some aspects of the responses of chemical systems, linear or nonlinear, to perturbations on several earlier occasions. The first was the responses of the chemical species in a reaction mechanism (a network) in a nonequilibrium stable stationary state to a pulse in concentration of one species. We referred to this approach as the pulse method (see chapter 5 for theory and chapter 6 for experiments). Second, we studied the time series of the responses of concentrations to repeated random perturbations, the formulation of correlation functions from such measurements, and the construction of the correlation metric (see chapter 7 for theory and chapter 8 for experiments). Third, in the investigation of oscillatory chemical reactions we showed that the responses of a chemical system in a stable stationary state close to a Hopf bifurcation are related to the category of the oscillatory reaction and to the role of the essential species in the system (see chapter 11 for theory and experiments). In each of these cases the responses yield important information about the reaction pathway and the reaction mechanism. 

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