Reactive chromatography

This microreactor was heated to the desired reaction temperature and dioxan was pumped through the reactor. If a pulse of 1,4-butandiol is injected into the flowing dioxan, the diol forms tetrahydrofuran and water on the acidic polymer particles inside the channels of the rod. Water is adsorbed strongly tetrahydrofuran leaves the reactor first, followed by water. Fig. 8.21 gives a calculated chromatogram based on sorption data. 

The production of water-free tetrahydrofuran is possible using this method 28], but this is only a model reaction. No one will produce a bulk chemical like tetrahydrofuran in a microreactor. But products with higher value have similar reaction behavior, for example the esterification of end-terminated long-chain hydroxycar-bon acids. An inner ester forms by cyclization leading to macrocydic compounds, which can be used in the flavor and fragrance industry. 

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Ellman s reagent has been used not only for the determination of sulfhydryls in proteins and other molecules, but also as a precolumn derivatization reagent for the separation of thiol compounds by HPLC (Kuwata et al., 1982), in the study of thiol-dependent enzymes (Masamune etal., 1989 Tsukamoto and Wakil, 1988 Alvear et al., 1989), and to create sulfhydryl-reactive chromatography supports for the coupling of affinity ligands (Jayabaskaran etal., 1987). Another important use of the compound... 

The outline of this chapter is as follows First, some basic wave phenomena for separation, as well as integrated reaction separation processes, are illustrated. Afterwards, a simple mathematical model is introduced, which applies to a large class of separation as well as integrated reaction separation processes. In the limit of reaction equilibrium the model represents a system of quasilinear first-order partial differential equations. For the prediction of wave solutions of such systems an almost complete theory exists [33, 34, 38], which is summarized in a second step. Subsequently, application of this theory to different integrated reaction separation processes is illustrated. The emphasis is placed on reactive distillation and reactive chromatography, but applications to other reaction separation processes are also... 

In contrast to this, in (reactive) chromatography usually mass or molar concentrations are used. Then, j and r are the corresponding rates of change of these quantities, and a and / are the ratios of the volumetric hold-ups and the volumetric flow rates in both phases. N is equal to Ns, the number of solutes. For the details, we refer to Ref. [11]. 

Finally, it should be noted that the above treatment is only valid for constant flow rates. For processes without solvent (e.g., reactive distillation processes), this assumption is only valid for equimolar reactions. For equimolar reactions the definition of transformed concentration variables introduced by Ung and Doherty [41] reduces to the definition in Eq. (6). For processes with solvent, (e.g., reactive chromatographic processes), the assumption of constant flow rates is also valid in good approximation, if the concentration of the solvent is high compared to the other reacting species. This is also true if one of the reactants is used simultaneously as a solvent, as in many applications of reactive chromatography (see e.g. Refs. [1, 28]). 

In this section the methods developed in the previous section will be applied to analyze the dynamic behavior of integrated reaction separation processes. Emphasis is placed on reactive distillation and reactive chromatography. Finally, possible applications to other integrated reaction separation processes including membrane reactors and sorption-enhanced reaction processes will be briefly discussed. More details about reactive distillation processes were provided in Ref. [39]. For chromatographic reactors the reader should refer to Chapter 6 of this book, for sorption-enhanced reaction processes to Chapter 7, and for membrane reactors to Chapter 12. 

As in reactive distillation and reactive chromatography, many sorption-enhanced reaction processes are controlled by phase equilibrium in addition to reaction equilibrium. The situation is different for membrane reactors, where phase equilibrium between the phases adjacent to the membrane is often trivial and the process is... 

F. Lode, M. Houmard, C. Migliorini, et ah, Continuous reactive chromatography. Chem. Engng. 

Reactive chromatography belongs to the category of reactor-separator processes, and it is especially attractive as alternative to reactive distillation if the components involved are nonvolatile or heat-sensitive, as are often encountered in biotechnology. 

The principle of reactive chromatography can be easily explained using a simple reversible reaction of type A o B + C. Looking at a single chromatographic column filled with a stationary phase which serves as a selective adsorbent and as a heterogeneous catalyst, the development of a pulse of A injected into the continuous eluent stream is shown in Fig. 6.1. 

The feasibility of combining chemical reaction and adsorption separation in a single unit has been discussed in this chapter. In particular, two units allowing continuous operation have been considered, namely annular reactive chromatography and simulated moving-bed reactors. 

Recently developed improved SMB processes, e.g. VariCol (Ludemann-Hombourger et al., 2000b), PowerFeed (Zhang et al., 2003) and ModiCon (Schramm et al., 2003), can also be used in reactive chromatography. Application of the VariCol... 

Strohlein, G., Assuncao, Y, Dube, N., Bardow, A., Mazzotti, M., and Morbidelli, M. (2006) Esterification of acrylic add wilh methanol by reactive chromatography experiments and simulation. Chem. Eng. Sci., 61, 5296-5306. 

Thermodynamic effects. Many performance limitations are related to a thermodynamic equilibrium, which is the case for numerous reversible reactions. Existing solutions consist in coupling the reaction with a separation system (reactive distillation, reactive chromatography, etc.) and can even be coupled to geometric structuring [11]. 

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