Packed bed membrane reactors PBMRs

Most research reports involve an inert, selective membrane that encloses a PB of catalyst particles, a packed-bed membrane reactor (PBMR). It must be noted that the catalyst bed can also be fluidized or fixed, but types other than PBs are rarely found in literature. The following are the advantages of this type of reactor ... 

For a packed-bed membrane reactor (PBMR) the membrane is permselective and removes the product as it is formed, forcing the reaction to the right. In this case, the membrane is not active and a conventional catalyst is used. Tavolaro et al. [45] demonstrated this concept in their work on CO2 hydrogenation to methanol using a LTA zeolite membrane. The tubular membrane was packed with bimetallic Cu/ZnO where CO2 and H2 react to form EtOH and H2O. These condensable products were removed by LTA membrane which increased the reaction yield when compared to a conventional packed bed reactor operating under the same conditions [45]. 

Figure 5.1 Distributed dosing in inert packed-bed membrane reactors (PBMR) with dead-end configuration fora reaction A r- B -> P.

In this chapter a specific type of membrane reactor, the so-called distributor was analyzed theoretically. In contrast to conventional tubular fixed-bed reactors (FBR), where all reactants are introduced together at the reactor inlet (cofeed mode), packed-bed membrane reactors (PBMR) allow dosing of one or several reactants via membranes over the reactor wall along the axial coordinate (distributed-feed mode). 

Different types of membrane reactors for hydrogen production have been proposed in the literature. Most of the previous work has been performed in packed bed membrane reactors (PBMRs) however, there is an increasing interest in novel configurations such as fluidized bed membrane reactors (FBMRs) and membrane micro-reactors (MMRs), especially because better heat management and decreased mass transfer limitations can be obtained in these novel reactor configurations. 

Oxidative coupling of methane using a catalytic-membrane reactor (CMR), catalyst packed-bed reactor (PBR), and catalyst packed-bed membrane reactor (PBMR), have been also compared. The authors conclude that the catalytic activity of PBR and PBMR (using Na-WMn/Si02) were lower than that observed for CMR (with a yield of 34.7%). 

By far the most commonly referred to reactor is the packed bed membrane reactor (PBMR), in which the reaction function is provided by a packed bed of catalysts in contact with the membrane. The membrane itself is not catalytic or at least not intentionally so, but is used to add or remove certain species from the reactor. If the membrane is highly perm-selective, this configuration appears ideal for situations where two complementary reactions take place on either side of the membrane - the product of the reaction on one side acting as a reactant on the other side, while the endothermicity of one reaction is compensated by the exothermicity of the other. When the catalysts at work are present in a fluidized mode, the reactor is then called a fluidized bed membrane reactor (FBMR). 

In this case two different reactor configurations are usually distinguished the packed-bed membrane reactor (PBMR), and the fluidized-bed membrane reactor FBMR). 

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