Membrane reactor multi-tubular

Another class of processes where it is advantageous to keep the reactants separated from each other, except within the catalyst pores, is oxidation of light gaseous hydrocarbons (e.g., ethene, propene, butene). Conventionally these processes are carried out in multi-tubular fixed-bed reactors (see, for example, Fig. 20). Flammability considerations usually restrict the feed mixture composition. By adopting the concept of a multi-tubular cooled catalytic membrane reactor (with inclusion of heat pipes ), with reactants kept separate, we should be able to avoid any flammability constraints. 

The two most common membrane geometries are the flat plate and the tube. Single flat plate membranes are usually used in laboratory scale investigations due to their ease of fabrication. Tubular membranes are more and more popular due to their much larger ratio of the membrane surface area to the equipment volume than flat plate membranes [4]. OITM reactor configurations with multi-planar or multi-tubular structures are required for commercial use. 

FIGURE 6.25 Scheme of the multi-tubular membrane reactor. (Taken from Figure 1 of M.E. Adrover, A. Anzola, S. Schbib, M. Pedernera, D. Borio, Catal. Today 156 (2010) 223.)... 

O. lyoha, R. Enick, R. Killmeyer, B. Howard, B. Morreale, M. Ciocco, WaU-catalyzed water-gas shift reaction in multi-tubular Pd and 80 wt%Pd-20 wt%Cu membrane reactors at 1173 K,... 

A packed bed membrane reactor is an assembly of usually uniformly sized catalytic particles, which are randomly arranged and firmly held in position within a vessel or tube. A permeable membrane (generally tubular) is immersed within the particles or represents the tube wall of the fixed bed. The PBMR could look, for example, like a tube-in-shell or a multi-tubular reactor. Zooming in on the reaction zone the different phenomena occurring in the reactor can be described as follows ... 

Espro et al. reported the oxidation of propane to the corresponding oxygenated products (n-propanol, isopropanol, propionic aldehyde and acetone) mediated by the Fe " -H202 Fenton system in a distributor/ contactor-type membrane reactor, under mild conditions. A composite Nafion/PEEKWC (a modified polyetheretherketone) catalytic membrane separates the gas (propane/helium) and liquid (Fe -H202) phases. The flat and hollow fibre multi-tubular membrane reactor configurations were compared, being the best performances achieved with the hollow fibre multi-tubular configuration. 

In conclusion, it was proved that the CFD model could be applied to a shell-and-tube membrane reactor. All of the methods developed and the results obtained are expected to be easily extended to the design and analysis of more complicated reactors such as multi-tubular membrane... 

Cross-sectional view of the multi-tubular palladium membrane reactor. 

Table 13.5 Experimental conditions and results for the cyclohexane dehydrogenation using the multi-tubular palladium membrane reactor...

Figure 13.19 shows a comparison between the experimental (plots) and simulated (lines) results for Cases 21-23 in Table 13.5, where both conversion and hydrogen permeation rate can be found to be in good agreement. This indicates that the CFD model developed here is valid for analysing the multi-tubular membrane reactor designed in this text. 

Mimura,K.,N.Yoshida,T.Sato andN.Itoh CFD analysis and design of multi-tubular membrane reactor for dehydrogenation of cyclohexane ,/ Jpn. Petrol. Inst.,Si, 283-291 (2010b). 

Akyurtlu etal. (1988) carried out a theoretical investigation on multi-phase porous tubular catalytic membrane with the liquid phase on the external side and the gas phase in the membrane tube lumen. They showed the importance of the Tliiele modulus on the reactor performance and that thin-walled catalyst tubes have larger effectiveness factors. 

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