Membrane reactors formulation

Again, the simple isothermal 1-D plug-flow reactor model provides a good basis for quantitative descriptions. This model allows to explore the potential of using series connections of several membrane reactor segments. The corresponding mass balance for a component i and a segment k can be formulated as follows ... 

In chapter 2, some basic ideas about steam reforming in conventional and membrane reactors are worked out. In this chapter the operation of conventional steam-reformers is compared with possible membrane steam-reformers. In this chapter also a techno-economic evaluation of a membrane reactor compared with the conventional process is provided. The boundary conditions imposed by process technology and the techno-economic evaluation result in the formulation of requirements for the development of the membranes, i.e. selectivity, flux, tube length, operating pressure, etc. 

In chapter 8 a new project has been formulated for the use of membrane reactors for the thermal dehydrogenation of H2S. Compared to the conventional Claus process, the application of a membrane reactor in the thermal H2S might have some large advantages. 

A model of a biphasic enzyme membrane reactor for the hydrolysis of triglycerides has been formulated according to the bond graph method of network thermodynamics, and the kinetics, the permeabilities of fatty acids and glycerides, the rates of inhibition of the immobilized enzyme, and the concentration of enzyme in a reaction zone are studied. 

Pal, P., Dutta, S. and Bhattacharya, P. (2002). Multi-enzyme immobUization in eco-friendly emulsion liquid membrane reactor—A new approach to membrane formulation. Sep. Purif. Technol., 27, 145-54. 

With reference to the book content, the authors divided it into 11 chapters. The book starts with an overview on membrane selective membranes integrated in the chemical reaction environment. The thermodynamics and kinetics of membrane reactors are also formulated and assessed for different membrane reactor architectures. 

These three parameters (or other equivalent dimensionless groups) must appear in whatever formulation of this type of problem (the esterification reaction in PVRs), possibly together with other parameters which take into account other aspects such as additional phenomena (for example concentration polarization of the membrane), the presence of products in the initial mixture, the concentration of the catalyst and more complex constitutive equations. The dimensionless parameters have a more general validity than the individual dimensional parameters that appear grouped into them and characterize more univocally the behaviour of the system. The adoption of the parameter 5, the ratio of the characteristic rate of permeation to the characteristic rate of reaction, can be extended to any PVR and in general also to any membrane reactor. With this approach the comparison between different studies on PVRs is more direct and meaningful. On the other hand, the less acceptable, though often employed, dimensional parameter A/V, is comprised in the definition of 5. 

In 1994, Serralheiro and coworkers deseribed the a-chymotrypsin catalyzed synthesis of A-acetyl-L-phenylalanine-L-leucinamide in a reverse micellar membrane reactor operated in a batch mode [65]. The reverse micelles were formulated with TTAB, heptane, and hexanol. An ultrafUtration ceramic membrane was used to retain the enzyme and separate the peptide. The reactor was operated for four days without any loss of enzyme activity and the yield of the produced dipeptide was around 80%. 

In fixed-bed reactors the P/V ratio is higher than 1.0 because the catalyst has to endure the highly oxidizing C4/O2 gas mixture (typically 1.8-2.0% butane in air). An important point is that a VPO formulation designed to work in a fixed-bed reactor may not be optimal for other operating conditions. In studies mimicking the behavior of the catalyst in a membrane reactor, Mota et al. showed that the surface was rapidly reduced, but that it could be restored by re-oxidation after 2 h. 

Abstract Mathematical modeling is widely used for the design and control of industrial processes and, in particular, membrane processes the approach is based on the formulation of transport models to analyze the transport phenomena occurring in the membrane module as well as within the membrane. However, analysis of such complex behaviors is rather onerous and time consuming for practical purposes and some of the interactions between the fluid and the membrane structure or related to the actual kinetics, in the case of membrane reactors, are not yet completely understood. For these reasons, several simplified approaches have been proposed in the Uterature to describe the behavior of real membrane systems. 

The rising need for new separation processes for the biotechnology industry and the increasing attention towards development of new industrial eruyme processes demonstrate a potential for the use of liquid membranes (LMs). This technique is particularly appropriate for multiple enzyme / cofactor systems since any number of enzymes as well as other molecules can be coencapsulated. This paper focuses on the application of LMs for enzyme encapsulation. The formulation and properties of LMs are first introduced for those unfamiliar with the technique. Special attention is paid to carrier-facilitated transport of amino acids in LMs, since this is a central feature involved in the operation of many LM encapsulated enzyme bioreactor systems. Current work in this laboratory with a tyrosinase/ ascorbate system for isolation of reactive intermediate oxidation products related to L-DOPA is discussed. A brief review of previous LM enzyme systems and reactor configurations is included for reference. 

Today, membranes perform critical separations in the production, purification and formulation of biotechnology products. Specific functions include sterilize filtration (both upstream and downstream of the reactor), virus removal (both upstream and stream), perfusion, medium exchange, harvest, and purification. 

Figure 8.50 Liquid membrane capsule. The diameter of the capsule is 150 to 1000 /im. The diameter of encapsulated micro droplets is 1 to 5 /im. The encapsulated active phase can contain a catalyst, such as an enzyme the LMC then function as reactors . The reactants diffuse into the catalyst-active phase, and the products diffuse out. The encapsulated phase can also be a reagent. LMC encapsulating a reagent-active phase can be formulated to function as traps. Here the species to be removed diffuses from the solution being treated through encapsulating phase to the reagent-active phase. The reagent converts the material to a non-permeable species which cannot diffuse back through the encapsulating phase and becomes trapped [262].

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