Membrane reactors hollow

Compared to batch processes, continuous processes often show a higher space-time yield. Reaction conditions may be kept within certain limits more easily. For easier scale-up of some enzyme-catalyzed reactions, the Enzyme Membrane Reactor (EMR) has been developed. The principle is shown in Fig. 7-26 A. The difference in size between a biocatalyst and the reactants enables continuous homogeneous catalysis to be achieved while retaining the catalyst in the vessel. For this purpose, commercially available ultrafiltration membranes are used. When continuously operated, the EMR behaves as a continuous stirred tank reactor (CSTR) with complete backmixing. For large-scale membrane reactors, hollow-fiber membranes or stacked flat membranes are used 129. To prevent concentration polarization on the membrane, the reaction mixture is circulated along the membrane surface by a low-shear recirculation pump (Fig. 7-26 B). 

In this case study, an enzymatic hydrolysis reaction, the racemic ibuprofen ester, i.e. (R)-and (S)-ibuprofen esters in equimolar mixture, undergoes a kinetic resolution in a biphasic enzymatic membrane reactor (EMR). In kinetic resolution, the two enantiomers react at different rates lipase originated from Candida rugosa shows a greater stereopreference towards the (S)-enantiomer. The membrane module consisted of multiple bundles of polymeric hydrophilic hollow fibre. The membrane separated the two immiscible phases, i.e. organic in the shell side and aqueous in the lumen. Racemic substrate in the organic phase reacted with immobilised enzyme on the membrane where the hydrolysis reaction took place, and the product (S)-ibuprofen acid was extracted into the aqueous phase. 

Hollow-fiber membrane reactor Hydrolysis of sunflower oil Lipase from Rhizopus sp. 122... 

The production process for (S)-phenylalanine as an intermediate in aspartame perpetuates the principle of reracemization of the nondesired enantiomer (Figure 4.5) in a hollow fiber/ liquid membrane reactor. Asymmetric hydrolysis of the racemic phenylalanine isopropylester at pH 7.5 leads to enantiopure phenylalanine applying subtilisin Carlsberg. The unconverted enantiomer is continuously extracted via a supported liquid membrane [31] that is immobilized in a microporous membrane into an aqueous solution of pH 3.5. The desired hydrolysis product is charged at high pH and cannot, therefore, be extracted into the acidic solution [32]. 

Ricks, E.E., Estrada-Vades, M.C., McLean, T.L. and Iacobucci, G.A. (1992) Highly enantioselective hydrolysis of (/ ,Sl-phenylalanine isopropyl ester by subtilisin Carlsberg. Continuous synthesis of (Sl-phenylalanine in a hollow fibre/liquid membrane reactor. Biotechnology Progress, 8, 197-203. 

Enzyme membrane reactor for production of diltiazem intermediate. A solution of the racemic ester in organic solvent enters the port at the bottom of the reactor and flows past the strands of microporous, hollow-fiber membrane that contain an enzyme. The enzyme catalyzes hydrolysis of one enantiomer of the ester that undergoes decarboxylation to 4-methoxyphenylacetaldehyde (which in turn forms a water-soluble bisulfite complex that remains in the aqueous phase). The other enantiomer of the ester remains in the aqueous stream that leaves the reactor via the port at the top. Courtesy of Sepracor, Inc. 

In a comparable system, (I ,S)-ibuprofen can be separated by a membrane reactor [83], see Fig. 13.10. The technique comprises a stereo-specific hydrolysis by an enzyme. Subsequently, the enantiomeric ester is extracted into the organic phase on the other side of the membrane. In the system developed by Sepracor Inc., (i )-ibuprofen is selectively hydrolyzed by proteases in a hollow-fiber unit and the (S)-ibuprofen ester can be isolated at 100% yield. This configuration also applies for enantioseparation of other acids such as naproxen and 2-chloropropionic acid. 

Malcata, F.X. and Hill Jr., C.G. (1995) Indnstrial ntihzation of a hollow-fiber membrane reactor for the controlled lipolysis of bntterfat. Enzyme EngineeringXII, edited by M.-D. Legoy and D. N.Thomas. Annals of the New York Academy of Science, Vol. 750, 401-407. 

Matsumae, H., Fumi, M., Shibatani, T. and Tosa. T. (1994) Prodnction of optically-active 3-phenylglycidyl acid ester by the lipase from Serratia marcescens on a hollow-fiber membrane reactor. Journal ofEermentation and Bioengineering, 78(1), 59-64. 

Membrane reactors, using semi-permeable membranes, usually of sheet or hollow fiber type... 

HOLLOW-FIBER MEMBRANES. A hollow-fiher membrane is a capillary having an inside diameter of - inn and an outside diameter < I mm and whose wall functions as a semipermeahlc membrane. The fibers can he employed singly or grouped into a bundle which may contain tens of thousands of fibers and up to several million libers as in reverse osmosis (Fig. 11. In most eases, hollow fibers are used as cylindrical membranes that permit selective exchange of materials across (heir walls. However, they can also he used as containers to effect the controlled release of a specific material, or as reactors to chemically modify a permeate as il diffuses through a chemically activated hollow-liher wall. e g., loaded with immobilized enzyme. 

Lipases (E.C. 3.1.1.3.) catalyze the hydrolysis of lipids at an oil/water interface. In a membrane reactor, the enzymes were immobilized both on the side of the water phase of a hydrophobic membrane as well as on the side of the organic phase of a hydrophilic membrane. In both cases, no other means for stabilization of the emulsion at the membrane were required. The synthesis reaction to n-butyl oleate was achieved with lipase from Mucor miehei, which had been immobilized at the wall of a hollow fiber module. The degree of conversion reached 88%, but the substrate butanol decomposed the membrane before the enzyme was deactivated. 

Chiral amines, here (R)-l-aminotetralin, were obtained from racemic amine and pyruvate in a 39 mL hollow-fiber membrane reactor with (SJ-cotransaminases (ft>TA) (Shin, 2001). The substrates were recirculated until the e.e. value exceeded 95%. Simulations suggested residence times should be short to minimize product inhibition. 

Figure 13.19 A hollow fiber membrane reactor. Nutrients (S) diffuse to the microbial cells on the shell side of the reactor and undergo reaction to form products (P) such as monoclonal antibodies [31]. Reprinted from J. Membr. Sci. 39, K. Schneider, W. Holz, R. Wollbeck and S. Ripperger, Membranes and Modules for Transmembrane Distillation,...

An elegant solution has been proposed based on a membrane reactor consisting of a module with hollow cellulose libers [see Fig. 11 (31)]. The enzyme is placed at the inner side of the libers, to which the fat is fed. Water passes at the... 

HOLLOW-FIBER MEMBRANE REACTOR FOR THE LIPASE CATALYZED HYDROLYSIS SYNTHESIS OF DILTIAZEM... 

Figure 9. Optical resolution of 3-phenylglycidic acid methyl ester (MPGM) by lipase and separation of the optically active product, (-)-MPGM, from unnecessary acid using Hollow-Fiber membrane reactor...

In a multiphase membrane reactor, the conversion of benzylpenicillin to 6-aminopenidllinic acid is performed. The type of microstructured reactor used is a fermentation reactor which contains the enzyme penicillin acylase immobilized on the wall of a hollow-fiber tube. The hollow-fiber tube extracts 6-aminopenicillinic acid at the same time selectively. Benzylpenicillin is converted at the outer wall of the hollow fiber into the desired product, which passes into the sweep stream inside the fiber where it can be purified, e.g. by ion exchange. The non-converted benzylpenicillin is recycled back through the reactor [84],... 

Wang, h., Tablet, C., Schiestel, T., Werth, S. and Caro, J. (2006) Partial oxidation of methane to syngas in perovskite hollow fiber membrane reactor. Catalysis Communications, 7, 907-912. 

The basic hydrodynamic equations are the Navier-Stokes equations [51]. These equations are listed in their general form in Appendix C. The combination of these equations, for example, with Darcy s law, the fluid flow in crossflow filtration in tubular or capillary membranes can be described [52]. In most cases of enzyme or microbial membrane reactors where enzymes are immobilized within the membrane matrix or in a thin layer at the matrix/shell interface or the live cells are inoculated into the shell, a cake layer is not formed on the membrane surface. The concentration-polarization layer can exist but this layer does not alter the value of the convective velocity. Several studies have modeled the convective-flow profiles in a hollow-fiber and/or flat-sheet membranes [11, 35, 44, 53-56]. Bruining [44] gives a general description of flows and pressures for enzyme membrane reactor. Three main modes... 

The first published information on the industrial application of a hybrid system with a HF contactor for production of the drug dilthiazem intermediate was reported by Lopez and Matson [23]. An enzymatic resolution of dilthiazem chiral intermediate is realized in an extractive enzymatic membrane reactor. The enzyme is entrapped in the macroporous sponge part of the hydrophilic hollow-fiber membrane made of a... 

Asymmetric Microporous Nonporous, skinned on microporous substrate Flat-sheet, tubular, hollow fiber Flat-sheet, tubular, hollow fiber Phase-inversion casting or spinning Phase-inversion casting or spinning Microfiltration, ultrafiltration, membrane reactors Reverse osmosis, gas separation, pervaporation, perstraction, membrane reactors... 

Venkatadri R, Irvine RL. Cultivation of Phanerochaete chrysosporium and production of lignin peroxidase in novel biofilm reactor systems hollow fiber reactor and silicone membrane reactor. Water Res 1993 27 591-596. 

Different membrane shapes are used, such as plates, foils, spirals, hollow fibers, tubes, and even monilithic multichannel elements have been mentioned in the context of membrane reactors. In the following section, a general survey will be given indicating the main characteristics of the different types of inorganic membranes used in CMRs. More details can be found elsewhere [13-15]. 

Another favorable aspect of stirred batch reactors is the fact that they are compatible with most forms of a biocatalyst. The biocatalyst may be soluble, immobilized, or a whole-cell preparation in the latter case a bioconversion might be performed in the same vessel used to culture the organism. Recovery of the biocatalyst is sometimes possible, typically when the enzyme is immobilized or confined within a semi-permeable membrane. The latter configuration is often referred to as a membrane reactor. An example is the hollow fiber reactor where enzymes or whole cells are partitioned within permeable fibers that allow the passage of substrates and products but retain the catalyst. A hollow-fiber reactor can be operated in conjunction with the stirred tank and operated in batch or... 

There have been numerous studies exploring the concept of membrane reactors. Many of them, however, are related to biotechnological applications where enzymes are used as catalysts in such reactions as saccharification of celluloses and hydrolysis of proteins at relatively low temperatures. Some applications such as production of monoclonal antibodies in a hollow fiber membrane bioreactor have just begun to be commercialized. 

Membranes that arc catalytically active or impregnated with catalyst do not suffer from any potential catalyst loss or attrition as much as other membrane reactor configurations. This and the above advantage have the implication that the former requires a lower catalyst concentration per unit volume than the latter. It should be mentioned that the catalyst concentration per unit volume can be further increased by selecting a high "packing density" (surface area per unit volume) membrane element such as a honeycomb monolith or hollow fiber shape. 

There is some indication that a high "packing density" membrane shape may result in a greater conversion than, for example, membrane tubes. In a study of using an a-alumina hollow fiber (1.6 mm in diameter) coated with an y-alumina membrane as a membrane reactor for dehydrogenation of cyclohexane, Okubo et al. [1991] found that a given... 

Single tubular membrane reactors are often used in experimental and feasibility studies. Its justification for use in production environments can sometimes be made in small volume applications. As mentioned in Chapters 4 and 5, inorganic composite membranes consist of multiple layers. The inner most layer in a tubular composite membrane reactor does not necessarily possess the finest pores. For example, a two>layered tubular ceramic membrane reactor used for enzymatic reactions has an inner layer containing pores larger than those in the outer layer [Lillo, 1986]. The pores of the inner layer are immobilized with enzymes. Under the influence of an applied pressure difference across the membrane matrix, a solution entering the hollow central core of the tube Hows into the inner layer where the solution reacts with the enzyme. The product which is smaller than the enzyme passes through the permselective outer layer membrane which retains the enzyme. Thus the product is removed from the reaction mixture. 

As mentioned earlier, one of the membrane element shapes with the highest packing density is hollow fibers. Typically several fibers are bundled to provide higher strength. In a packed-bed membrane reactor of this type, catalyst particles arc packed around the bundles. 

Itoh et al. [1984] modeled a 1.5-m long packed-bed membrane reactor for catalytic decomposition of HI. The reactor consists of a large number of microporous hollow fiber... 

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