Membrane reactor pumping

Two types of continuous membrane reactors have been applied for oligomer- or polymer-bound homogeneous catalytic conversions and recycling of the catalysts. In the so-called dead-end-filtration reactor the catalyst is compartmentalized in the reactor and is retained by the horizontally situated nanofiltration membrane. Reactants are continuously pumped into the reactor, whereas products and unreacted materials cross the membrane for further processing [57]. 

Fig. 6. Allylic alkylation in a continuous flow membrane reactor using dendritic ligand 5c (flow rate 50mLh reactor volume 20 mL, Koch MPF-60 NF membrane, molecular weight cut-off = 400 Da slight increases are due to pump failures) (19b).

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.

The continuous high-pressure enzyme membrane reactor [30] is shown in Figure 9.2-4. The membrane with 35 mm diameter is placed between two sintered plates and fitted in the reactor. A certain amount of the catalyst (hydrated enzyme preparation) is put in the reactor which is electrically heated, with a heating jacket, to constant temperature. The substrates and the gas are pumped into the membrane reactor with the high-pressure pump. The products and unreacted reactants are collected in the separator. The catalyst remains in the reactor (behind the membrane). 

The unusual interaction of hydrogen with palladium-based membrane materials opens up the possibility of oxidative hydrogen pump for tritium recovery from breeder blankets. The feasibility for this potential commercial application hinges on the hot-fusion and cold-fusion technology under development [Saracco and Specchia, 1994]. At first, Yoshida et al. [1983] suggested membrane separation of this radioactive isotope of hydrogen followed by its oxidation to form water. Subsequently, Hsu and Bauxbaum [1986] and Drioli et al. [1990] successfully tested the concept of combining the separation and reaction steps into a membrane reactor operation. 

Figure 8.7 Schematic diagrams showing two electrocatalytic membrane reactor configurations (a) eicctrochemicai oxygen pumping and (b) solid oxide fuel cell operation.

Catalytic applications of solid electrolyte membrane reactors using electrochemical oxygen pumping (EOP)... 

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... 

FIC. 1. Lipase-catalyzed esterification for the production of sugar fatty acid esters in a stirred-tank membrane reactor. 1, pump 2, water bath 3, membrane reactor 4, condenser 5, permeate container 6, vacuum pump. 

Another class of dense inorganic membranes that have been used in membrane reactor applications are solid oxide type membranes. These materials (solid oxide electrolytes) are also finding widespread application in the area of fuel cells and as electrochemical oxygen pumps and sensors. Due to their importance they have received significant attention and their catalytic and electrochemical applications have been widely reviewed [94-98]. Solid materials are known which conduct a variety of cationic/anionic species [14,98]. For the purposes of the application of such materials in catalytic membrane reactor applications, however, only and conducting materials are of direct relevance. 

Zeolite membranes have been demonstrated for many applications. Applications such as separation membranes, membrane reactors, adsorption, and catalysis have been covered in several reviews. In this entry, we focus on new applications including sensors, low-dielectric constant (low-k) films, corrosion resistant coatings, hydrophilic coatings, heat pumps, and thermoelectrics. 

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). 

Figure 3.7. The PVMR system of Waldburger et al [3.8], Left, flow chart of the PVMR system. B container, F filter, H stopcock, K condenser, P pump, Rl membrane reactor, V valve. Right, schematic of the membrane reactor. With permission from John Wiley and Sons.

Figure 7.1 Experimental set-up of an enzyme membrane reactor.11 P peristal tic pump LC level controller.

Detector UV 270 following post-column reaction. The column effluent mixed with 2 M NaOH and 0.05% sodium hypochlorite solution pumped at 0.1 mL/min in a 400 x 0.5 mm hollow fiber membrane reactor at 40° and this mixture flowed through a 1400 x 0.3 mm knitted open tubular reactor at 50° to the detector. 

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