Fundamentals of Membrane Reactors

This Part will be focused on the fundamentals and applications of membrane-assisted transformation processes, i.e. membrane reactors. Two separate chapters are dedicated to the fundamentals of membrane reactors using traditional chemical catalysts at high temperature (>200 °C) and catalysts of biological origin or biomi-metic at low temperature (<100 °C). 

IN0R6ANIC MEMBRANES SYNTHESIS AND APPLICATIONS 73. FUNDAMENTAL ASPECTS OF MEMBRANE REACTORS 73.1. Separative Membranes... 

Basile, A. (2013). Handbook of membrane reactors Fundamental materials science, design and optimisation. Cambridge Woodhead Pubhshing Limited. 

Abstract Pervaporation is a peculiar membrane separation process which is currently being considered for integration with a variety of reactions in promising new applications. Indeed, pervaporation membrane reactors have some specific uses in sustainable chemistry, which is an area currently growing in importance. The fundamentals of this type of membrane reactor are presented in this chapter, along with the advantages and limitations of different processes. A number of applications are reviewed with particular attention given to potential future developments. 

A particular case of the contact mode sketched in Fig. 4.3f is represented by the use of catalytic dense polymeric membranes working in cross-flow mode on the liquid feed side and in pervaporation mode through the membrane (Bengston et al, 2002). This particular class will be not discussed further, since Chapter 1 of Handbook of membrane reactors Volume 1 Fundamental materials science, design and optimisation is dedicated to polymeric membrane reactors.. 

Fundamentals of photocatalysis and some interesting information about membrane PRs regarding membrane materials and some operational issues can be found in Chapter 6—Photocatalytic Membrane Reactors Fundamentals, Membrane Materials and Operational Issues—by S. Mozia, A.W. Morawski, R. MoUnari, L. Palmisano, and V. Loddo, in Handbook of Membrane Reactors—Volume 2 Reactor Types and Industrial Applications, A. BasUe (ed.), Woodhead Publishing Limited, 2013, ISBN 978-0-85,709-415-5, pp. 236-295. 

Tan, X. and Li, K. (2013) Dense ceramic membranes for membrane reactors, in Handbook of Membrane Reactors, Volume I - Fundamental Materials Science, Design and Optimisation (ed A. Basile), Woodhead Publishing Limited, Cambridge, pp. 271-297. 

Fundamental or theoretical modeling is based on the formulation of transport models analyzing the transport phenomena occurring in the membrane module as well as within the membrane. An exhaustive analysis of such a complex behavior, however, is rather onerous and time consuming for practical purposes, since the resulting system of nonlinear partial differential equations can only be solved by means of numerical methods. Moreover, some of the interactions between the fluid and the membrane structure or related to the actual kinetics, in the case of membrane reactors, are not yet completely understood and, therefore, are very difficult to interpret by proper mathematical relationships. For these reasons, several simplified approaches have been proposed in the literature to describe the behavior of real membrane systems. 

Fundamental aspects of chemical membrane reactors (MRs) were introduced and discussed focusing on the peculiarity of MRs. Removal by membrane permeation is the novel term in the mass balance of these reactors. The permeation through the membrane is responsible for the improved performance of an MR in fact, higher (net) reaction rates, residence times, and hence improved conversions and selectivity versus the desired product are realized in these advanced systems. The permeation depends on the membranes and the related separation mechanism thus, some transport mechanisms were recalled in their principal aspects and no deep analysis of these mechanisms was proposed. 

---