Membrane reactors catalytic crystals

Interest in combining reaction and separation is growing. Thus industrial examples exist of reactive distillation and reactive crystallization. In this respect catalytic membranes [I] and membrane reactors come to the fore and are worldwide studied. 

An innovative potential application of membrane technology in catalysis and in catalytic membrane reactors is the possibility to produce catalytic crystals with a weU-defined size, size distribution, and shape by membrane crystallization (Fig. 27.9) (Di Profio et al., 2003, 2005). This innovative technology makes use of the evaporative mass transfer of volatile solvents through microporous hydrophobic membranes in order to concentrate feed solutions above their samration limit, thus attaining a supersaturated environment where crystals may nucleate and grow. In addition, the presence of a polymeric membrane increases the probability of nucleation with respect to other locations in the system (heterogeneous nucleation). 

Membranes of LaOCl can be manufactured from aqueous solutions of lanthanum chloride. After an adequate sintering step, LaOCl crystallizes at 400°C and is very stable up to 800°C, giving pore sizes as small as 1.5 nm [24], These membranes are used as catalytic reactors. 

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