Inert membrane reactors

The ultimate design of an inert membrane reactor would consist of well chosen crack free zeolite film membranes. The difficulties in this case are even more deterrent for industrial scale reactors since only a small number of holes or cracks would ruin the potential advantages of the design. 

Figure 9.6 Total conversion for inert membrane reactor with catalyst on the feed side (IMRCF), catalytic membrane reactor (CMR) and conventional fixed-bed reactor (FBR) with uniform and Dirac delta catalyst activity distributions as a function of the dimensionless residence time [Yeung et al., 1994]...

The choice of the above three modes of catalyst placement relative to the membrane can significantly affect the reactor performance. From the analysis of catalytically active and passive (inert) membrane reactors [Sun and Khang, 1988], it appears that the critical parameter determining the choice is the reaction residence time. At low residence times, the difference between a catalytically active and a catalytically passive membrane is not significant. However, as the reaction residence time becomes high, the catalytically active membrane shows a higher reaction conversion. 

Figure 10.4 shows the methane conversion as a function of the normalized reactor length according to the model [Ocrtel et al., 1987]. The packed-bed inert membrane reactor (solid line) is superior to a conventional reactor (dashed line) without the Pd tubes. The advantage can be 36% higher than that in the conventional reactor for a Pd thickness of 50 Jim. 

Applying an isothermal and plug>flow membrane reactor (on both sides of the membrane) to the above reactions, Itoh and Xu [1991] concluded that (1) the packed-bed inert membrane reactor gives conversions higher than the equilibrium limits and also performs better than a conventional plug-flow reactor without the use of a permselective membrane and (2) the co-current and counter-current flow configurations give essentially the same conversion. 

Itoh and Govind [1989b] further analyzed an isothermal packed-bed inert membrane reactor but under a counter-current flow configuration. Under the conditions studied, the authors found that the counter-current flow configuration provides a much greater conversion than the co-current flow mode. 

Two of the main types of catalytic membrane reactors are shown in Fti, me 4-12, The reactor in the middle is called an inert membrane reactor ivi/ i catalyst pellets on the feed side (IMRCF). Here the membrane is inert 8i..1 serves as a batrier to the reactants and some of the products. The reactor on ih bottom is a catalytic membrane reactor (CMR). The catalyst is deposiid directly on the membrane and only specific reaction products are able to e it the permeate side. For example, in the reversible reaction... 

The different types of membrane reactor configurations can also be classified according to the relative placement of the two most important elements of this technology the membrane and the catalyst. Three main configurations can be considered (Figure 25.13) the catalyst is physically separated from the membrane the catalyst is dispersed in the membrane or the membrane is inherently catalytic. The first configuration is often called the inert membrane reactor (IMR), in contrast to the two other ones, which are catalytic membrane reactors (CMRs).5o... 

Inert membrane reactors (IMRs) Catalytic membrane reactors (CMRs)... 

Farrusseng D, Julbe A, and Guizard C. Evaluation of porous ceramic membranes as O2 distributors for the partial oxidation of alkanes in inert membrane reactors. Sep Purif Technol 2001 25 137-149. 

A.B. Bindjouli, Z. Dehouche, B. Bernauer and J. Lieto, Numerical simulation of catalytic inert membrane reactor. Computers Chem. Eng., 18 (Suppl.) (1994) 5337-5341. 

Ramos, R. Pina, M.P. Menendez, M. Santamaria, J. Patience, G.S. Oxidative dehydrogenation of propane to propene simulation of a commercial inert membrane reactor immersed in a fluidized bed. Can. J. Chem. Eng. 2002, 79, 902-912. 

Packed Bed Membrane Reactor (Inert Membrane Reactor, Inert Membrane Reactor with Catalyst on Feed side)... 

An interesting point regarding OCM is that the membrane material itself may act as a total oxidation catalyst, thus unintentionally turning the PBMR into a PBCMR. Lu et pre-treated their dense membrane with an OCM catalyst to prevent contact between hydrocarbons and the membrane oxide material. Coronas et al. carried out experiments to estimate the contribution from the membrane and used it to modify their model of OCM in a porous membrane. They found that the predicted advantage of the membrane reactor was decreased if the catalytic activity of the membrane was taken into account, and suggested the development of inert membrane reactor materials, and more active OCM catalysts, as possible remedies. 

Figure 9.1 (a) Tubular inert membrane reactor with the catalyst packed in the lumen side, (b) Tubular inert membrane reactor with the catalyst packed in the shell side. 

Q Hybrid of fixed-bed reactor (PFR) and selective inert membrane reactor (IMR-P) in series... 

An operational variation reminiscent of combined MT and TM reactors is the use of a plug-flow, fixed-bed reactor followed in series by a packed inert membrane reactor, as shown in Figure 24.If (Wu and Liu, 1992). 

Table 5.1 Structural properties of typical membrane materials for Inert membrane reactor applications...

Mallada, R., Pedemera, M., Menendez, N. and Santamaria, J., 2000. Synthesis of Maleic Anhydride in an Inert Membrane Reactor. Effect of Reactor Configuration. Industrial Engineering Chemistry Research, 39(3) 620-625. 

Oxidative Dehydrogenation of Propane in an Inert Membrane Reactor. Catalysis Today, 56(1-3) 239-245. 

Simulation of an Inert Membrane Reactor for the Oxidative Dehydrogenation... 

Yang, H.-S., Chou, C.-T. (2008). Non-isothermal simulation of cyclohexane dehydrogenation in an inert membrane reactor with catalytic pellets in the feed-side chamber. Journal of the Chinese Institute of Chemical Engineers, 39, 227—235. 

Figure 1.2 Exploitable features of membrane reactors, (a) Enhancing the conversion of a reversible reaction in a packed-bed inert membrane reactor, (b) Enhancing the conversion of a reversible reaction in a catalytic membrane reactor, (c) Preventing slip in a reaction requiring stoichiometric feeds, (d) Enhancing the rate of a multiphase reaction, (e) Energetic, thermodynamic, or kinetic coupling of two reactions run on opposite sides of a membrane, (f) Hybrid of fixed-bed reactor (PER) and selective inert membrane reactor (IMR-P) in series. 79...

Ge, S., Liu, C., Wang, L.J. (2001). Oxidative Dehydrogenation of Butane Using Inert Membrane Reactor with a Non-Uniform Permeation Pattern, Chem. Eng. J., 84, pp. 497-502. 

Inert membrane reactor The membrane does not participate directly in the reaction IMR... 

In catalytic membrane reactors (CMRs), the reactions take place directly on the membrane and the membrane functions as both a catalyst and a separator/distributor.This requires that the membrane material has intrinsic catalytic activity or that it is modified by the addition of active components. Some of the commonly utilized inorganic (such as metal oxide and zeolite) and metal membranes are intrinsically catalytically active. In other cases, the catalysts can be integrated with the membrane into a single body by being coated on the membrane surface or deposited inside the membrane porous structure. In case the membrane does not participate in the reaction directly, but is used to add or remove certain species from the reactor, this is called an inert membrane reactor (IMR). 

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