Membrane reactor hollow fibre

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. 

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. 

In order to obtain a sufficiently large membrane area on an industrial scale, hollow fibre ultrafiltration modules are applied (similar types to those used for protein purification). Since the concentration of NAD(H) does not change in the steady state and there is no NAD(H) in the entrance or exit flow, it becomes clear that the actual concentration of pyruvate in the reactor is equal to the concentration in the feed. Since there is a non-zero concentration of pyruvate in the reactor (and in the exit flow), some pyruvate has to be added to the reactor continuously in order to keep the reaction going. The rate equations of both reactions are required to calculate the precise rate of pyruvate addition. 

Three types of membranes have been applied so far for MTBE degrading reactors 1) A ceramic cross-flow ultraflltration membrane with a molecular cut-off of 300 kDaltons and pore size 0.02 im [40] 2) an internal hollow fibre membrane [62] and 3) a porous polyethylene, 0.48 cm thick membrane with pore size of 18-28 xm [42,52,63,64]. Interestingly, it was reported by the authors who used this latter polyethylene membrane mentioned that there was no need to apply a pressure across the membrane for operation in their reactor. 

Kramer, G.F.H., S.Th. Bouwer, R.W. van Gemert, J.T.P. Derksen, and F.P. Cuperus, En-z)Tnatic PeroxycarboxyUc Acid Formation in a Hollow-Fibre Membrane Reactor Kinetics and Mass Transfer, Catalysis Today 22 537-547 (1994). 

In a comparable system, (R,S)-ibuprofen can be separated by a membrane reactor [132] (see Fig. 5.18). The technique comprises a stereospecific 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., (R)-ibuprofen is selectively hydrolyzed by proteases in a hollow-fibre 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-chloro-propionic acid. 

The second way to increase the membrane area per volume of reactor is adopting the hollow fibre configuration. For example, in the case of perovskite membranes, the membrane flux is generally quite low and the hollow fibre configuration is quite interesting. The main investigators of hollow fibre MRs are summarized in Table 3.3. 

Table 33 Major investigators on hollow fibre membrane reactors...

Kleinert et al. [26] studied, for example, POM in a hollow fibre MR. The perovskite membranes used by the authors were produced from Ba(Co,Fe,Zr)03 (BCFZ) powder via phase inversion spinning technique. A tube-in-tube configuration was used while the catalyst was packed in the shell side of the reactor. 

Kleinert, A., Feldhoff, A., Schiestel, T. and Caro, J. (2006) Novel hollow fibre membrane reactor for the partial oxidation of methane. Catalysis Today, 118,44-51. 

Tan, X. and Li, K. (2004) LSCF hollow fibre membranes for air separation and oxidative coupling reactions. Proceedings of the Sixth International Conference on Catalysis in Membrane Reactors, Lahnstein, Germany, 70. 

Kingsbury, B.F.K. (2010) A morphological study of ceramic hollow fibre membranes a perspective on multifunctional catalytic membrane reactors, Imperial College London PhD thesis. 

Caro, J., Wang, H.H., Tablet, C. et al. (2006) Evaluation of perovskites in hollow fibre and disk geometry in catalytic membrane reactors and in oxygen separators. Catalysis Today, 118 (1-2), 128-135. 

There are other published resolutions of 4-hydroxyphenylglycine, one of which involves the enzyme-catalysed hydrolysis of the ethyl ester (Scheme 6.9). Since the substrate is fully blocked at the amino and the carboxylate functions, it is scarcely soluble in water and must be dissolved in an organic solvent. The specific hydrolysis of the ester catalysed by an enzyme in an aqueous phase in contact with the organic solvent will yield a water-soluble carboxylic acid which transfers to the aqueous phase containing the enzyme. The conditions of the reaction therefore effect both hydrolysis of the ester and facile separation of the product. In fact, the enzyme is immobilized on a hydrophilic membrane at the interface between the two immiscible phases. The membrane reactor (Figure 6.2) comprises a large bundle of hollow fibres, each having an external diameter of about... 

Figure 62. Sdiematic drawing of a two-phase membrane reactor. The membrane reactor consists of a bundle of thin hollow fibres. The ends of the fibre bundle are sealed with resin so that the aqueous process stream can enter the lumina of the fibres without mixing with the organic stream which flows over their outer surfaces. The enzyme is immobilized in the spongy matrix of the fibres. As the substrate difiuses from the organic phase into this matrix, it is hydrolysed. The product is sduble in the aqueous process stream which carries it out of the reactor. (Reproduced by kind permission of Sepracor Ltd.)...

Most of the above problems can be overcome by using immobilized enzymes in other words, enzymes which are confined in a well-defined region of space by means of a selective membrane, or immobilized by, for example, absorption or entrapment within the polymeric matrix of a membrane. Enzymes are prohibited, due to their molecular size, from diffusing out or permeating through the membrane, while substrates and products can readily permeate the membrane. The enzymes retain their catalytic properties and can be repeatedly and continuously used. Traditional immobilization techniques are summarized in Rg. 1.1. They include adsorption on a surface, covalent binding to an insoluble support, co-polymerization with a proteic carrier, encapsulation in a membrane shell and confinement in a gel. A comparison between some different techniques is also reported in Table 1.2. Hollow fibre membranes are commonly used for membrane reactors... 

The analysis of a hybrid bioartificial membrane pancreas (HBMP) in which porcine islets of Langerhans were segregated in the shell side of a hollow fibre module, showed the importance of convective fluxes in determining reactor performance. A distributed parameter model, taking into account... 

Rahman M A, Garcfa-Garcfa F R, Irfan Hatim M D, Kingsbury B F K and Li K (2011), Development of a catalytic hollow fibre membrane micro-reactor for high purity H2 production,/ Membrane Sci, 368,116-123. 

Liu Y, Tan X and Li K (2006b), Non-oxidative methane coupling in the SrCeo.gsYbo.osOs.o (SCYb) hollow fibre membrane reactor , 7nd Eng Chem Res, 45,3782-3790. 

Tan X, Pang Z, Gu Z and Liu S (2007), Catalytic perovskite hollow fibre membrane reactors for methane oxidative coupling ,/ Afemhrane Sci,3Wl, 109-114. 

Wu Z, Wang B and Li K (2010), A novel dual-layer ceramic hollow fibre membrane reactor for methane conversion ,/ Membrane Sci, 352,63-70. 

Lee, K.-C. and Rittmann, B. E. 2000. A novel hollow-fibre membrane biofihn reactor for autohydrogenotrophic denitrification of drinking water. Water Science and Technology, 41,219-226. 

Lante A, Crapis A, Krastanov A, Spettoli P (2000), Biodegradation of phenols by laccase immobilised in a membrane reactor , Proc. Biochem., 36,51-58. Basheer S, Mogi K, Nakajima M (1995), Development of a novel hollow-fibre membrane reactor for the interesterification of triglycerides and fatty acids using modified lipase , Proc. Biochem., 30,531-536. 

Garcfa-Garcfa, F. R., Torrente-Murciano, L., Chadwick, D., Li, K. (2012). Hollow fibre membrane reactors for high H2 yields in the WGS reaction. Journal of Membrane Science, 405, 30-37. 

Lee and co-workers (Lee et al., 2007 Lee, Li, Noike, 2009) describe the continuous H2 production in a continuously stirred tank reactor coupled with a submerged hollow-fibre membrane unit. The presence of the membrane module integrated within the reaction volume allows reducing biomass washout at a high hydraulic retention time with a general improvement of the reactor performance in terms of H2 productivity and yield. 

The membrane slurry reactor typically consists of a housing containing hollow fibre membranes and heat exchanger tubes. By using membranes with a pore diameter of 0.5 im or smaller it is possible to use catalyst particles from about 1 pm without entrainment. The reactants and products are removed from the reactor via the hollow fibre membranes. Retaining the catalyst particles within the reactor has the following advantages ... 

Caro, J., Schiestel, T., Werth, S., et al. (2006). Perovskite Hollow Fibre Membranes in the Partial Oxidation of Methane to Synthesis Gas in a Membrane Reactor, Desalination, 199, pp. 415-417. 

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