Reactive Column Sections

The corresponding wave patterns of the transformed concentration variable X for a reactive distillation column are shown in Fig. 5.8. Here, a single feed with pure reactant A is introduced in the middle of the column. As in the nonreactive binary case, the composition profiles consist of a single front in each column section,... 

In this section, we discussed for the vertical column (d) reactive management how the transition from application models to tools takes place. We focused on the process-side and explained, how apphcation models and tool models are related to each other. Finally, we discussed the relation of achieved results to the process/product model. 

The integration of the recycling reactor directly into the distillation column leads to the process configuration shown in Fig. 5.2, in which the reaction takes place within the column total reboiler. On top of the reboiler a fully non-RD section is installed. This process can be seen as a simple hybrid RD column with only one reactive tray. Comparing the curves in Fig. 5.4 and Fig. 5.6, the operational characteristics of the two processes, recycling system and distillation column with reactive reboiler, are identical at 93 = 00 and R = co. 

Fig. 5.9 shows the geometric representation of these balances in the McCabe-Thiele diagram. The distillate composition xP is located at the intersection of the condenser operating line and the operating line of the RD section. By specifying xP, the number of reactive trays can be estimated from the classical staircase construction. From the intersection of the operating line of the column section with that of the reboiler line, the bottom composition is determined. 

Comparing the performance of the three different RD processes considered, one can conclude that a non-RD section on top of reactive total reboiler seems to be the best configuration for both productivity and reliability of design. The minimum reflux ratio of this configuration can be estimated from (5.17) and (5.15). This R,ni value can be significantly reduced by installation of a pre-reactor 1). A fully RD column often suffers from splitting of the product in the upper column section owing to backward reaction. 

It is preferable if the reactions in RD columns are catalyzed by heterogeneous catalysts because they are easily kept in the reactor and they allow hybrid RD columns combining reactive and non-reactive sections. Fig. 5.25 illustrates a column randomly packed with supported ion exchangers in rings. Such a heterogeneous cat-... 

The three solution branch dominating the nonlinear behavior of the process can also be observed in a conventional process with a reactor-separator recycle as recently reported by Blagov et al. [12]. This flowsheet is analogous to a column with one reactive and one non-reactive column section with a single product stream, the multiplicity behavior of which has been studied Cerafimov and coworkers [49, 83]. In these papers it is shown that this type of output multiplicity is a generic phenomenon for reaction systems with competing irreversible reactions and a similar distribution of volatUities between reactants and products. 

Figure 2.6. Separation train for an homogeneons catalyst. Remark the dark sections of the columns represent reactive zones. System features chemical reaction A + B C D is inert component, (adapted from BessHng et al. (1997))...

The type II flowsheet differs fiom type I in that the two columns (the reactive distillation column and the stripper) are separated by a decanter. Thus, this flowsheet should interact less from steady-state and dynamic points of view. The composition profile in Figure 7.12 indicates that the reactive section generates the necessary acetates, followed by a rectifying... 

Distillate Di has a composition of methanol (28 mol% methanol) that is near the azeotrope at 4 bar. It is fed at a rate of 1122 kmol/h to the methanol recovery columns section. Table 8.2 gives information about important streams associated with the prereactor and reactive distillation column. 

In liquid chromatography, in contrast to gas chromatography [see Section 9.2(2)], derivatives are almost invariably prepared to enhance the response of a particular detector to the substance of analytical interest. For example, with compounds lacking an ultraviolet chromophore in the 254 nm region but having a reactive functional group, derivatisation provides a means of introducing into the molecule a chromophore suitable for its detection. Derivative preparation can be carried out either prior to the separation (pre-column derivatisation) or afterwards (post-column derivatisation). The most commonly used techniques are pre-column off-line and post-column on-line derivatisation. 

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