Van de Vusse reaction

This reaction system is a kind of complex van de vusse reaction, a typical reaction process involving consecutive and parallel reactions. It is, therefore, sufficiently complex to illustrate the algorithm. Due to the limit to the space of the article, we only select temperature, concentration and back-mixing to be the object of research to illustrate the use of the algorithm. 

The reaction system involved in the case studied is a kind of relatively complex van de vusse reaction, nevertheless the reaction system in real manufacturing process may involve more reaction types and, therefore, is more complex than that one. One can, however, simulate the change of environmental indexes within a reactor by combining traditional reactor mathematical model with the PEI balance, and may also discover the effects of reaction conditions and engineering factors on environmental performance by PEI rate-law expression and/or combinations it with other reaction rate equations as well as other related equations in reactor mathematical models. 

Example 4 Here, we revisit the van de Vusse reaction of Example 1 with altered rate constants. The objective function again is the yield of intermediate species B. The rate vector is given by R X) = [-X X, — 2X, 2X, ... 

Figure 6.8 Construction of the attainable region for the van de Vusse reaction (a) PFR trajectory from C(0) = [1, 0] (solid line), with mixing line (dotted line) (b) CSTR trajectory from C(0) = (1, 0] (dashed line) (c) addition of bypass to CSTR (dotted line) (d) addition of PFR in series with CSTR (dot-dashed line).

Reactions The Van de Vusse reactions involve a parallel decomposition of a hypothetical species A to side-products B and D. Component B is an intermediate product (similar to toluene in the BTX system), which further decomposes to a final product C. 

Now that the AR has been determined, optimization of the system may be carried out if a suitable objective function is supplied. The Van de Vusse reaction involves the production of a number of products (B, C, and D). Since component B is assumed to be the desired product, it may be useful to understand the yield of component B achievable in the system,... 

Eor example, assume that the Van de Vusse reactions are available. What set of achievable concentrations might be obtained by a single PER from a feed Cf = [c f, Cgf] = [1, 0] mol/L In Figure 5.14(a), the PFR trajectory is generated from Cf and plotted in c -Cb space. Since mixing is not allowed (because physically there is no bypass stream conneeting the... 

Optimal Continuous Structure In Section 7.2.1, we examined the nature of the optimal continuous reactor structure for the three-dimensional Van de Vusse reaction scheme. Let us now investigate the associated optimal batch structure for the same problem. This exercise will demonstrate the role that DSRs, and by extension fed-batch reactors with varying a policies, play in the formation the AR boundary. 

Thus, solving the facet enumeration problem with A and b represents finding the extreme points of the stoichiometric subspace for the three-dimensional Van de Vusse reaction in extent space. 

The reaction for the system is assumed to follow the Van de Vusse reaction scheme. For simplicity, assume that we are only interested in components A and B in the system, so that the component rate expressions are given by... 

Here, component i may represent components A, B, C, or D in the Van de Vusse reaction. Since we have assumed that density is constant and that all three CSTRs are connected in series with no additional bypass or recycles, the feed volumetric flow rates to each CSTR are also constant. Hence, Qi = Q2 = Q3 = Q4 = 1 L/s. 

Figure 8.33 provides an example of construction resulting from the IDEAS formulation for the well-known two-dimensional Van de Vusse reaction. 

Problem Specification For convenience, the Van de Vusse reaction scheme is given in the following ... 

A technique developed by Professors Glasser and Hildebrandt allows one to find the optimum reaction system for certain types of rate laws. The WWW uses modified van de Vusse kinetics, that is,... 

Example 1. The isothermal van de Vusse (1964) reaction involves four species for which the objective is the maximization of the yield of intermediate species B, given a feed of pure A. The reaction network is given by... 

We now provide a small process example to illustrate the simultaneous synthesis of reactor and energy networks. Here, we consider a reaction mechanism in the van de Vusse form, though with kinetic expressions different from those used above. The integrated flowsheet corresponding to the synthesis problem is shown in Fig. 12. 

In this section, we reconsider the van de Vusse process to illustrate our synthesis approach. This example also shows the application of the unified reaction-separation-energy integration model. Comparisons are made between sequential and simultaneous modes of synthesis, and the applicability of the simplified model is verified. 

The concept of AR will be illustrated by means of an example developed originally by Glasser and Hildebrand (1987). The problem consists of finding the best reactor network that maximises the amount of B product formed by the following reaction scheme (van de Vusse) ... 

In the instances where selectivity is affected, this will be expressed in the ratio (Cc /Cb ), which will vary with the extent of the reaction, van de Vusse found that a satisfactory correlation between the variation of Cq and Cb was given by... 

Figure 7.30 Influence of diflnsion on the yield in a consecutive second-order gas/liquid reaction. [After J.G. van de Vusse, Chem. Eng. Sci., 21, 631, with permission of Pergamon Press, Ltd., London, England, (1966).]...

The discussion is again in terms of the group y = y/kiC fki, and Cg /C (Van de Vusse assumed the diffusivities to be equal). When y exceeds 2 (Le., when the reaction is very fast), gradients of B and R occur in the film when C /C, < y. Then an effect of mass transfer will be detected, not only on the rate of the global phenomenon, but also on the selectivity. When y < 0.5 and the... 

Figure 6.3.f-2 Type 3 reaction. Influence of CgJC i on selectivity (from Van de Vusse [16]). 

Van de Vusse [16, 17] also performed experiments on the chlorination of n-decane, a reaction system of the type considered here, in a semibatch reactor. In such a reactor the chlorine gas is bubbled continuously through a batch of n-decane. In some experiments the n-decane was pure, in others it was diluted with dichlorobenzene. In some experiments the batch was stirred, in others not. The experimental results could be explained in terms of the above considerations. In all experiments y > 1 (from 150 to 500), hence the rate of the process was limited by diffusion, but the selectivity was only affected when Cgo/C i < y. This condition was only fulfilled for the experiments in which n-decane (B) was diluted. For only these experiments were the selectivities in nonstirred conditions found to differ from those with stirring. 

For more complicated reaction networks, it is not always completely obvious how to apply the above concepts, as is seen from consideration of the example of van de Vusse [10] ... 

Many other examples of optimizing the chemical environment have been discussed in the literature. For example, van de Vusse and Voetter [14] have considered the parallel %cond-order reactions ... 

The differential equations for these reactions and analytical solutions wherever possible are included in Table 10.2. The semibatch mode of operation of the Van de Vusse scheme gives results similar to those of the recycle reactor. Thus higher yields and selectivities for product R can be realized than in a PFR or an MFR when 3[/4]q 2 ... 

This poses an interesting problem in that a PFR would favor R by the first reaction while a CSTR would suppress the undesired second reaction (Van de Vusse, 1964). As this problem can be resolved by using a recycle reactor (with its partial mixing), it was considered in Chapter 10. 

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