IMRCFs

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]...

Besides total conversion, other reaction performance index may benefit from optimizing the catalyst distribution and location. Examples are product purity on the feed or p>ermeate side and product molar Row rate on the feed or permeate side. Yeung et al. [1994] have also investigated these aspects and provided comparisons among IMRCF, FBR and catalytic membrane reactor (CMR) in Figure 9.8. It is apparent that the various reaction performance indices call for different optimal catalyst distributions. 

Figure 9.7 Effect of location of Dirac delta catalyst activity distribution on toul conversion as a function of dimensionless residence time for (a) IMRCF (b) CMR and (c) FBR [Yeung etal., 1994]...

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... 

Compare the conversion profiles of a conventional PFR with those of an IMRCF. What generalizations can you make ... 

Figure4-13 Membrane reactors. (PhotoCourtesy of CoorsCeramics,Golden. Colorado.) (a) Photo of ceramic reactors, (b) cross section of IMRCF. (c) cross section of CRM. (d) schematic of IMRCF for mole balance.

In Fig. 5.18 IMRCF (s=l) corresponds to the PBMR with catalyst pellets with a non-uniform catalyst distribution, while CMR ( =1) is the CMR with the catalyst placed non-uniformly on the membrane surface in contact with the catalytic reactor feed. IMRCF (a(s)=I) and CMR (a( )=I) correspond to the PBMR and CMR with uniform catalyst distributions. The conventional packed-bed reactor (FBR in Figure 5.18) exhibits conversions, which are below the equilibrium conversion, and for large residence times are lower than those exhibited by the CMR and the PBMR. The highest conversions are obtained with the non-uniform activity (Dirac delta case) profiles. This result was explained on the basis that the access of the reactants to the active catalytic sites was not limited by diffusion. When the catalyst is uniformly distributed the PBMR exhibits better performances than the CMR. It is interesting to note that at low residence times the packed-bed reactor conversion is higher than that of the PBMR with a uniformly distributed catalyst this is because in this case for the PBMR the reactants are only partially in contact with the catalyst due to diffusional limitations. 

Use the same equations for the IMRCF in POLYMATH to generate the desired plot. 

Figure 23 Comparison of conversion for different reactor configurations [CMR, IMRCF (PBMR) and FBR (PFR)J uniform catalyst distribution [a(s) = l or a( )=l] and delta-function catalyst distribution ( 8=1 or...

The catalyst distribution inside the PBMR is the critical parameter in enhancing MR performance. The utilisation of catalyst s active phase during the reaction in accordance with the membrane separation of desired components will affect positively. For example, to have well-mixed fluid phases no interphase mass transfer or diffusional resistance during the reaction and separation should occur (Yeung et al, 1994). In the PBMR the active catalyst pellets are distributed inside the membrane module on the feed side as in the conventional FBR. In the CMR the active catalyst particles and sites are located within the membrane. Morbidelli et al. (2001) have reported a non-uniform catalyst distribution and its optimal bed location in the PBMR or an inert membrane reactor with a catalyst on the feed side (IMRCF) and in the CMR. In the case of a non-uniform catalyst distribution, that is. 

IMRCF inert membrane reactor with a catalyst on the feed side... 

---