Catalytic membrane reactor

In the case of a catalytic membrane reactor (CMR), the membrane is (made) intrinsically catalytically active. This can be done by using the intrinsic catalytic properties of the zeolite or by making the membrane catalytically active. When an active phase is deposited on top of a membrane layer, this is also called a CMR because this becomes part of the composite membrane. In addition to the catalytic activity of the membrane, a catalyst bed can be present (PBCMR). The advantages of a CMR are as follows  

1) improved selectivity due to good control of contact time and thereby limiting the occurrence of unwanted consecutive reactions  

3) shift in chemical equilibrium conversion due to a reduced concentration level of faster diffusing components in the membrane and 

4) safer operation when the membrane is used as an interfacial contactor keeping certain reactants segregated and preventing the formation of flammable or explosive mixtures. 

In CMRs, no separate catalyst is used and reactions take place on the membrane. Zeolite membranes can be intrinsically catalytic due to the presence of catalytic sites (Bronsted acid sites, Lewis acid sites, metal ions in cationic positions, transition metal ions in zeolite lattice positions, extra-lattice transition metal compounds in channels and cavities of a zeolite, metal particles in zeolite cavities) and their high internal surface area. 

The intrinsic catalytic activity of zeolites, coupled with the possibility of tuning adsorptive properties, makes them good candidates for bringing about simultaneous reaction and separation. The catalytic membranes exhibit improved selectivity and resistance to deactivation compared with the same catalyst employed in a packed bed configuration [28]. 

In an FTMR configuration, the reactant mixture flows through the membrane, and thereafter they react with each other on the catalytically active sites. The zeolite membrane can be non-perm-selective but acts as a reaction site facilitating the access of reactants to the catalyst. 

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Catalytic A catalytic-membrane reactor is a combination heterogeneous catalyst and permselective membrane that promotes a reaction, allowing one component to permeate. Many of the reactions studied involve H9. Membranes are metal (Pd, Ag), nonporous metal oxides, and porous structures of ceran iic and glass. Falconer, Noble, and Speriy [in Noble and Stern (eds.), op. cit., pp. 669-709] review status and potential developments. 

Catalytic Membrane Reactors Membrane reactors combine reaction and separation in a single vessel. By removing one of the... 

Falconer, J.L., Noble, R.D., and Sperry, D.P. (1995) Catalytic Membrane Reactors, in Membrane Separations Techndogy Principles and Applications, Chapter 14 (eds R.D.Noble and S.A. Stern), Elsevier, Amsterdam, pp. 669-712. 

Whilst the basic process for generation and conversion of syngas is well established, production from biomass poses several challenges. These centre on the co-production of tars and hydrocarbons during the biomass gasification process, which is typically carried out at 800 °C. Recent advances in the production of more robust catalysts and catalytic membrane reactors should overcome many of these challenges. 

Characterization of a Zeoiite Membrane for Catalytic Membrane Reactor Application... 

One of the most studied applications of Catalytic Membrane Reactors (CMRs) is the dehydrogenation of alkanes. For this reaction, in conventional reactors and under classical conditions, the conversion is controlled by thermodynamics and high temperatures are required leading to a rapid catalyst deactivation and expensive operative costs In a CMR, the selective removal of hydrogen from the reaction zone through a permselective membrane will favour the conversion and then allow higher olefin yields when compared to conventional (nonmembrane) reactors [1-3]... 

In the isobutane dehydrogenation the catalytic membrane reactor allows a conversion which is twice the one observed in a conventional reactor operating under similar feed, catalyst and temperature conditions (and for which the performance corresponds to the one calculated from thermodynamics) [9]. 

Catalytic Membranes Falconer, Noble, and Sperry (Chap. 14— Catalytic Membrane Reactors in Noble and Stem, op. cit., p. 669-712) give a detailed review and an extensive bibhography. Additional information can be found in a work by Tsotsis et al. [ Catalytic Membrane Reactors, pp. 471-551, in Becker and Pereira (eds.), Computer-Aided Design of Catalysts, Dekker, 1993]. 

Tsuru, T., K. Yamaguchi, T. Yoshioka, and M. Asaeda, Methane steam reforming by microporous catalytic membrane reactors, AIChE., 50(11), 2794-2805, 2004. 

A catalytic membrane reactor (CMR) presents an alternate configuration where the membrane is both catalytically active and permselective. The reactant conver-... 

Figure 13.20 Methylcyclohexane conversion to toluene as a function of reactor temperature in a membrane and a nonmembrane reactor [45]. Reprinted with permission from J.K. Ali and D.W.T. Rippin, Comparing Mono and Bimetallic Noble Metal Catalysts in a Catalytic Membrane Reactor for Methyl-cyclohexane Dehydrogenation, Ind. Eng. Chem. Res. 34, 722. Copyright 1995, American Chemical Society and American Pharmaceutical Association...

Ozone decomposition in airplanes Selective catalytic reduction of NOx Arrays of corrugated plates Arrays of fibers Gauzes Ag Methanol -> formaldehyde Pt/Rh NO production from ammonia HCN production from methane Foams Catalytic membranes reactors... 

Catalytic membrane reactors are not yet commercial. In fact, this is not surprising. When catalysis is coupled with separation in one vessel, compared to separate pieces of equipment, degrees of freedom are lost. The MECR is in that respect more promising for the short term. Examples are the dehydrogenation of alkanes in order to shift the equilibrium and the methane steam reforming for hydrogen production (29,30). An enzyme-based example is the hydrolysis of fats described in the following. 

Falconer JL, Noble RD, Sperry DP. Catalytic membrane reactors. In Noble RD, Stem SA, eds. Membrane Separations Technology. Principles and Applications. Amsterdam Elsevier, 1995 669-712. 

Possible application areas of catalytic membrane reactors include ... 

An excellent review of all potential applications of catalytic membrane reactors studied so far can be found in the 2002 book by Sanchez Marcano and Tsotsis (66). 

Fuel Cell Technology Catalytic Membrane Reactors Materials Research Chemical Sensors Electrolytic Technology Machining Welding Monopropellant Fuels... 

Kurungot et al. [48] developed a novel membrane material and a catalytic membrane reactor for the partial oxidation of methane. The driver of the development was the fact that rates of reforming reactions are much higher compared with the low permeability of conventional palladium membranes [49], Silica was previously recognized as a low-cost alternative to palladium [50], Additionally, the conventional... 

Besides previously described examples of integrated membrane systems and much more reported in the literature, including applications in gas separation and the petrochemical industry [29], a special case of integrated or hybrid membrane systems, with a lot of interest in the logic of the sustainable growth, is represented by the catalytic membranes reactors (CMRs). 

The availability of new membrane processes such as membrane contactors and catalytic membrane reactors, the progresses in membrane-fouling control and the development of new membranes with well-controlled structures and properties, are recognized as key factors for the design of alternative production systems. 

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