Chemzyme membrane reactor

Grafting a modified cinchona alkaloid to hexagonal mesoporous molecular sieve SBA-15 afforded catalyst (27) with excellent activity. 1-Phenyl-1-propene was converted to the corresponding diol in 98% yield (98% ee), while trans-stilbene yielded the desired product in 97% yield (99% ee) [92]. Other examples in this field are the utilization of microencapsulated osmium tetroxide by Kobayashi [93] and the application of continuous dihydroxylation mns in chemzyme membrane reactors described by Woltinger [94]. 

In analogy to the enzyme membrane reactors (EMRs) [8], a chemzyme membrane reactor (CMR) is used to retain a polymer-enlarged chemical catalyst of this kind. Tremendous progress could be made in the recycling of polymer-enlarged catalysts (Fig. 3.1.3) by employing different types of catalysts for both the enan-tioselective C-C bond formation and redox reactions. 

While a number of dendritic catalysts have been described, catalyst recyclization in most cases is an unsolved problem. Diaminopropyl-type dendrimers bearing Pd-phosphine complexes have been retained by ultra- or nanofiltration membranes, and the constructs have been used as catalysts for allylic substitution in a continuously operating chemzyme membrane reactor (CMR) (Brinkmann, 1999). Retention rates were found to be higher than 99.9%, resulting in a sixfold increase in the total turnover number (TTN) for the Pd catalyst. 

Table 18.3 Reactions and their performance data in a chemzyme membrane reactor (CMR).

D. Reichert, A. Kuhnle, H.-P. Krimmer and K. Drauz, Julia-Colonna asymmetric epoxidation in a continuously operated chemzyme membrane reactor, Synlett 2002, (5), 707-710. 

The enzyme membrane reactor (EMR) is an established mode for running continuous biocatalytic processes, ranging from laboratory units of 3 mL volume via pilot-scale units (0.5-500 L) to full-scale industrial units of several cubic meters volume and production capacities of hundreds of tons per year (Woltinger, 2001 Bommarius, 1996). The analogous chemzyme membrane reactor (CMR) concept, discussed in Chapter 18, Section 18.4.5, is based on the same principles as the EMR but is far less developed yet. 

Researchers at Degussa AG focused on an alternative means towards commercial application of the Julia-Colonna epoxidation [41]. Successful development was based on design of a continuous process in a chemzyme membrane reactor (CMR reactor). In this the epoxide and unconverted chalcone and oxidation reagent pass through the membrane whereas the polymer-enlarged organocatalyst is retained in the reactor by means of a nanofiltration membrane. The equipment used for this type of continuous epoxidation reaction is shown in Scheme 14.5 [41]. The chemzyme membrane reactor is based on the same continuous process concept as the efficient enzyme membrane reactor, which is already used for enzymatic a-amino acid resolution on an industrial scale at a production level of hundreds of tons per year [42]. 

The chemzyme membrane reactor is based on the same continuous process concept as the efficient enzyme membrane reactor, which has already been applied for enzymatic a-amino acid resolution on industrial scale at a production level of hundreds of tons per year (Drauz and Waldmann 2002 Wandrey and I iaschcl 1979 Wandrey et al. 1981 Groger and Drauz 2004). 

The principle of the enzyme membrane reactor technology (developed in a collaboration between Degussa AG and Professor Wandrey s group at the Research Institute Jiilich, and in operation since 1980), and thus the principle of the Chemzyme membrane reactor, is depicted in Figure 1. 

Taking advantage of the enormous differences in molecular weight (and hydro-dynamic volume) between the catalyst (an enzyme) and the substrates or the products, it is possible to confine the catalyst in a membrane reactor while the reagents and products can be selectively extracted from the reaction mixture without modifying the catalytic active intermediate. Remarkably, the Chemzyme membrane reactor concept allows a productivity per gram of catalyst which could be higher than in the case of enzymes because the polymers can be multifunctionalized with several active centers [1]. 

Figure 1 Principle of the enzyme reactor (left) and the Chemzyme membrane reactor (right). 7.5.2...

Figures Conversion and enantiomeric excess overtime in the reduction of tetralone with borane in a continuously operated Chemzyme membrane reactor.

Membrane and membrane reactors have not been used in the industrial practice but find some application as modern separation technique [26] or in laboratory work about the application of chemzymes [27] or for enzymatic syntheses [28],... 

Continuous application of chemzymes in a membrane reactor asymmetric transfer of hydrogenation of acetophenone. Adv Synth Catal 343(6-7) 711-720. 

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