Tubular ceramic membranes, reactor

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. 

Yin, X., Hong, L. and Liu, Z. (2008). Integrating Air Separation with Partial Oxidation of Methane A Novel Configuration of Asymmetric Tubular Ceramic Membrane Reactor, J. Membrane ScL, 311, pp. 89-97. 

The idea to limit polarization and fouling during tangential filtration of biological fluid by fluidizing small inert particles inside a tubular ceramic membrane had been presented at the end of the 1980s [25]. More recently, based on advances in the development of more stable membranes with increased permeance, the possibilities for integrating membranes into gas catalytic reactors to achieve a major increase in... 

Figure 8.11 Figure 2 from U.S. Patent Application 20030039601 A1 [26]. Longitudinal cross-sectional view of a reactor (72) for tubular ceramic membranes (80). 

Hussain, A., Seidel-Morgenstem, A. and Tsotsas, E., 2006. Heat and Mass Transfer in Tubular Ceramic Membranes for Membrane Reactors. International Journal of Heat and Mass Transfer, 49(13-14) 2239-2253. 

A catalytic membrane reactor having a tubular ceramic membrane for H2S decomposition was patented by Vizoso [76]. It was claimed that applying a membrane reactor between 400 and 7(X)°C, with the molybdenum sulphide catalyst deposited directly on the surface of the ceramic membrane, resulted in a 20% increase in the conversion of a 4% H2S stream, though few details were provided. 

Figure 9.8 Schematic of the tubular mixed conducting ceramic membrane reactor for POM.

After this chapter. Part 11 is dedicated to zeolite, ceramic and carbon membranes and catalysts used in membrane reactors. In Chapter 6 (Algieri, Comite and Capannelli) the remarkable properties of zeolite membranes are illustrated. Moreover, the key role of zeolite membrane reactors to improve the yield and the selectivity of reactions is particularly emphasised. Furthermore, the possibility of using zeolite membranes as micro-reactors and sensors is also discussed. Chapter 7 (Tan and Li) deals with dense ceramic membrane reactors, which are made from composite oxides usually having perovskite or fluorite structures with appreciable mixed ionic (oxygen ion and/or proton) and electronic conductivity. This chapter mainly describes the principles of various configurations (disc/flat-sheet, tubular and hollow fibre membranes) of dense ceramic membrane reactors and the... 

Shell-and-tube modules (Fig. 3b) seem to be more promising than flat-membrane ones, since they can develop up to 250 mVm [13]. Indeed, most of the recent literature on membrane reactors concerned tubular membranes. The lower the tube diameter, the higher the specific surface areas attainable. However attempts to manufacture hollow-fiber supported ceramic membranes were not completely satisfactory owing to the unacceptable brittleness of the obtained membranes from the practical application viewpoint [16-18]. 

The most important technique for perfusion culture methods is to separate the concentrated cells and conditioned medium from the suspended culture broth. As noted above, the separation methods chiefly used are filtration with tubular and flat membranes as well as ceramic macroporous filters. These membrane reactors can be employed for both anchorage-dependent and suspension growing cells. Static maintenance type systems are commercially available for disposable reactors, and small size unit reactors from 80 ml to 1 liter are used for continuous production of monoclonal antibodies with hybridoma cells. The maintainable cell densities are about 10 -10 cells/ ml which is essentially mouse ascites level. However, in these systems, the cell numbers cannot be counted directly because the cells adhere to membranes or hollow fibers. Therefore, the measurement of cell density must use indirect methods. Such indirect methods include the assaying of the quantities of glucose consumption and the accumulation of lactate. The parameters of scale-up have not yet been established for these static methods. 

A prototypic design for a tubular membrane reactor can be found in linde AG s patent appUcation shown in Fig. 8.9 [24]. This design uses a bundle of ceramic membrane tubes that are inside a pressure vessel. The tubes are closed at one end with the air fed to the tubes in the annulus between the ceramic tube, labeled 32,... 

Praxair has also filed patent applications on a syngas reactor incorporating tubular membranes, as shown in Fig. 8.11 [26]. Similar to the Unde AG design of Fig. 8.9, this design uses tubular membranes oriented with the axes of the tubes parallel to the axis of the cylindrical pressure vessel. High pressure syngas flows on the exterior of the ceramic membrane tubes, and low pressure air is fed into... 

With pervaporation membranes the water can be removed during the condensation reaction. In this case, a tubular microporous ceramic membrane supplied by ECN [124] was used. The separating layer of this membrane consists of a less than 0.5 mm film of microporous amorphous silica on the outside of a multilayer alumina support. The average pore size of this layer is 0.3-0.4 nm. After addition of the reactants, the reactor is heated to the desired temperature, the recyde of the mixture over the outside of the membrane tubes is started and a vacuum is apphed at the permeate side. In some cases a sweep gas can also be used. The pressure inside the reactor is a function of the partial vapor pressures and the reaction mixture is non-boiling. Although it can be anticipated that concentration polarization will play an important role in these systems, computational fluid dynamics calculations have shown that the membrane surface is effectively refreshed as a result of buoyancy effects [125]. 

There are three main types of dense ceramic membranes disk/flat sheet, tubular, and hollow fibers. The disk/flat sheet membranes are applied mostly in research work because they can be fabricated easily in laboratories with a small amount of membrane material. Comparatively, the hollow fiber membranes can provide the largest membrane area per volume but low mechanical strength, while the tubular membranes possess a satisfactory specific membrane area, high mechanical strength, and are easy to assemble in membrane reactors. Dense ceramic MRs can be constructed and operated in either packed bed MR or catalytic MR configurations. 

Dense ceramic membranes allow oxygen or hydrogen permeation in a dissociated or ionized form other than the conventional molecular diffusion, and thus exhibit extremely high selectivity (up to 100%). They can be incorporated into membrane reactors for a variety of oxidation and dehydrogenation reactions where the membrane functions as either a product extractor or a reactant distributor. Three configurations, that is, disc/flat-sheet, tubular and hollow fibre membranes have been applied in membrane reactors. They exhibit respective advantages/disadvantages in terms of the ease and cost of fabrication, the effective membrane area/volume ratio, and... 

Evaluate the ITM Syngas/ITM H2 processes using PDU data Conduct long-term stability tests of tubular membranes and seals at high pressure Demonstrate performance of pilot-scale membrane modules in PDU Complete membrane module design and select catalysts for the SEP Commission the ceramic Production Development Facility and fabricate SEP membranes Design and fabricate the SEP reactor... 

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