Catalytic membrane reactors operation

The pressure difference between the two membrane sides, namely the transmembrane pressure, determines the position of the gas-liquid interface along the membrane cross-section, since the phase-phase displacement will take place only in pores where the transmembrane pressure is greater than the breakthrough pressure. Therefore, in catalytic membrane reactors operating in contactor mode a strict control of the transmembrane pressure is very important. 

The overall effectiveness for a catalytic membrane reactor operating in the mode described in Fig. 4.3b can be defined as... 

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]. 

Figure 10.11a Conversion of cyclohexane dehydrogenation in a catalytic membrane reactor for high-space-timc operations [Sun and Khang, 1988]...

Some recent models have also appeared discussing the operation of three phase catalytic membrane reactors by Torres et al. [82]. The models which represent extension of prior models by Akyurtlu et al. [79] and Cini and Harold [80] are numerically analyzed and appear to simulate well the experimental results of the nitrobenzene hydrogenation reaction in a three phase catalytic membrane reactor. 

Three-phase catalytic membrane reactor systems, in our opinion, show significant promise, for near term application to hydrogenation reactions for fine chemicals synthesis. These reactions generally require mild operating conditions which will place less stringent requirements on the available and future commercial membranes. 

V.A. Papavassiliou, J.A. McHenry, E.W. Corcoran, H.W. Deckman and J.H. Meldon, High flux asymmetric catalytic membrane reactors. Optimization of operating conditions. Paper presented at the 1st International Workshop on Catalytic Membranes, September 1994, Lyon-Villeurbanne, France. 

The catalytic dehydrogenation of light alkanes is, potentially, an important process for the production of alkenes, which are valuable starting chemical materials for a variety of applications. This reaction is endothermic and is, therefore, performed at relatively high temperatures, to improve the yield to alkenes, which is limited, at lower temperatures, by the thermodynamic equilibrium. Operation at high temperatures, however, results in catalyst deactivation (thus, requiring frequent reactivation), and in the production of undesired by-products. For these reasons, this reaction has been from the beginning of the membrane reactor field the most obvious choice for the application of the catalytic membrane reactor concept, and one of the most commonly studied reaction systems. 

M- Kuba, Y. Fujii, S. Yamamatsu, Proceedings of the Italy-Japan Workshop on Catalytic Membrane Reactors and Integrated Membrane Operations, September 23-27, Getraro (GS) Italy, 1999, 88-51. 

Operations with multi-phase catalytic membrane reactors... 

In particular, Bottino et al. (2004) explored the performance of different catalytic membranes in the hydrogenation-isomerization of methylene-cyclohexane,in a temperature range between 288 and 343 K.The performance of the three-phase catalytic membrane reactor has been compared with that of a slurry reactor, resulting in a wider operating temperature range without mass transfer limitations. 

Aran, H. C., Klooster, H., Jani, J. M., WessUng, M., Lefferts, L., Lammertink, R. G. H. (2012). Influence of geometrical and operational parameters on the performance of porous catalytic membrane reactors. Chemical Engineering Journal, 207, 814—821. 

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