Magnetic membrane reactor

Figure 9.2-4. High-pressure continuous stirred tank membrane reactor S, substrates 1, reactor 2, separator 3, magnetic stirrer P, high pressure pump TIR, temperature regulator and indicator PI, pressure indicator.

Various types of photocatalytic membrane reactors in which the catalyst was used in different modes have been built with the purpose to have an easy separation of the catalyst from the reaction environment a photocatalyst in suspension in magnetically or mechanically agitated slurries confined by means of a membrane, fixed bed, catalyst deposited or entrapped on an inert support or in a membrane, and so on. 

The continuous enzyme membrane reactor (CMR). (1) Temperature-controlled water-bath (2) Feed tanig (3) Stirrer motor for feed tank (4) Feed pump (5) Feed inlet line to the reaction vessel (6) Reaction vessel (7) Magnetic stirring table (8) Prefilter (9) Recycle pum (10) Flowmeter (11) Membrane inlet pressure gauge (12) Hollow fiber membrane cartridge (13) Membrane outlet pressure gaug (1 Pressure adjusbneut valve (15) Retentate recycle line (16) Air bath environment (17) Pemieate (product) line (18) Permeate collection vessel (19) Electronic balance... 

A simplified form of a membrane reactor which does not require any special equipment may be obtained by using an enzyme solution enclosed in dialysis tubing like a tea bag (Fig. 3.7). This simple technique termed membrane-enclosed enzymatic catalysis (MEEC) seems to be applicable to most types of enzymes except lipases [447 149]. It consists of a dialysis bag containing the enzyme solution, mounted on a gently rotating magnetic stirring bar. 

Unilamellar vesicles have been used as a reactor for the synthesis of nanos-meter-scale magnetic particles (13,14). By adding alkaline solution to vesicles containing intravesicular solutions of Fe2+ and Fe3+, the Fe /Fe resulted in the formation of membrane-bound discrete particles of different ion oxide particles. These results together with the particle formation in microemulsion are not only of interest in colloid chemistry but also have significance in mineralization in biosystems, such as magnetotactic bacteria, where particles are formed within enclosed organic compartments. 

Reactions were carried out in the 140 ml reaction vessel. ( )-menthol and 200 mg of the enzyme peparation were placed in the reactor and the reactor connected to the system. The whole system was flushed with CO2 after which pressure and temperature were adjusted to 100 bar and 50°C. Water activity was set to the desired value by adding portions of water via the HPLC valve. The reaction was started by the addition of 1 ml of isopropenyl acetate once again via the HPLC valve. Final substrate concentrations were 20 mM menthol and 54 mM isopropenyl acetate. Stirring of the enzyme reactor was accomplished by a magnetic stirrer. In addition the reaction medium was pumped in a circle using a gear pump. The enzyme was retained in the enzyme reactor by a nylon membrane. Samples were taken via the HPLC-valve with a 500 pi sample loop, the content of which was expanded into hexane, and analyzed on a HP 5890 Series II gas chromatograph. 

Various designs of the stirred-flow reactor are possible. Carski and Sparks (1985) developed a relatively simple stirred-flow reactor constructed from a plastic syringe and membrane filter holder (Fig. 2-8). The volume of the reactor is adjustable to allow one to add and maintain a known amount of solution to a known amount of solid phase. Mixing is accomplished by a magnetic stirrer. 

In addition to the use of immobilized enzymes on suitable supports, which results in decreased costs in routine analyses, the solid forms of these biocatalysts provide a number of additional advantages, the most immediate of which are (1) simplification of the FI manifold required (use of an additional channel with a point of merging with the sample stream or an additional valve for simultaneous sample-enzyme injection is thus avoided) and (2) increased sensitivity as a result of the lower dilution of the sample on mixing with the enzyme solution. This latter advantage is even more apparent when several enzymatic steps involving different biocatalysts are required to obtain a measurable product. A serial arrangement of as many reactors as steps to be developed is very useful for this purpose. Immuno-reactors with either membranes or magnetic particles as the solid phase for the bovmd antibodies can also be used. 

The CMABR (2.4 L) is schematically shown in Fig. 9.22. Complete mixing of the feed is ensured by the recirculation of the feed mixture by a magnetic pump, while the influent was supphed from the reactor bottom by a peristaltic pump. The effluent is discharged from the top of the reactor. Air was supphed from the top of the reactor into the lumen side of the carbon tubes. A part of the air permeated through the carbon membrane tube to the shell side and reacted with the biofilm The rest was emitted from the bottom of the reactor. The reactor was maintained at 32°C by heating and also kept dark. The reactor was operated according to the operational scheme given in Table 9.4. 

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