Hquid/liquid phase membrane reactors

The aim of the chapter is to summarize the general features of catalytic membrane reactors apphed to gas-liquid and hquid-liquid systems in order to show the capabilities, advantages and hmitations of this emerging class of multi-phase reactors. 

As can be observed, the main difference between conventional three-phase reactors and catalytic membrane reactors hes in the relative positions of the mass transfer resistances with respect to the catalytic phase. In a conventional porous catalyst the catalytic sites in the pores have only one way or path of access. The gaseous reactant will encounter the first two mass transfer resistances at the gas-liquid interface, where the solvation equilibrium of the species from one phase to the other wiU take place. The dissolved species will diffuse towards the surface of the catalytic pellet for quite a long path in the hquid phase and will meet an additional mass transfer resistance at the hquid-sohd catalyst interface. It then needs to diffuse and react in the porous structure of the catalyst as well as the other reactant already present in the liquid phase. In the case of a traditional three-phase reactor (Fig. 4.3a), the concentration of at least one of the reacting species is hmited by its solubility and diffusion in the other fluid phase with a long diffusion path and in some cases unknown interfadal area (e.g., bubbles with variable size depending on the type of the gas feeding and distribution device in slurry reactors, not uniform phase contact and distribution in trickle-bed reactors). 

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