4 - Multi-phase catalytic membrane reactors

Abstract

The present chapter deals with multi-phase catalytic membrane reactors where the reactants distributed in different fluid phases meet on catalytic sites located in the structure of a catalytic membrane. The aim of the chapter is to summarize the features of catalytic membrane reactors applied to gas - liquid and liquid – liquid systems in order to show the capabilities, advantages and limitations of this class of emerging multi-phase reactors. In multi-phase systems, the catalytic membrane is usually used as an interface between two fluid phases and allows strict control of the reactant mass transfer with enhancement of the overall heterogeneous kinetics. Moreover, the particular features of the catalyst structured as a membrane can improve the intrinsic kinetics and the catalyst’s effectiveness. This chapter, by discussing some relevant points of catalytic membranes applied to multi-phase systems, aims at being a simple starting point for researchers who would like to begin their investigation in this fascinating field. After an introduction devoted to a first general description of multi-phase reactor systems, the chapter illustrates several contact modalities between reactants distributed in two different phases and the catalytic membrane. The role of mass transfer phenomena and reaction kinetics in multi-phase catalytic membrane reactors is discussed on the basis of simple well-known chemical engineering principles and modelling examples. Typical materials for multi-phase membrane reactors are briefly listed. Finally, some typical applications (e.g., hydrogenation and oxidation reactions) are reported.