Modelling reactive distillation

5192 R. Taylor, R. Krishna / Chemical Engineering Science 55 (2000) 5183}5229Fig. 13. Structured catalyst-sandwiches. (a) Catalyst sandwiched between two corrugated wire gauze sheets. (b) The wire gauze sheets are joinedtogether and sewn on all four sides. (c) The sandwich elements arranged into a cubical collection. (d) The sandwich elements arranged in a roundcollection. Photographs of the structure, along with CFD simulations of the liquid #ow within the sandwiches can be viewed at: http://ctcr4.chem.uva.nl/strucsim.Fig. 14. (a) Catalytically active Raschig ring. Adapted from Sundmacher (1995). (b) Structured packings coated with catalyst. (c) Fluted catalystmonolith tubes.Furthermore, frequent criss-crossing leads to a signi"-cant improvement in mass transfer within the sandwichstructures (Higler et al., 1999a).Another alternative is to make the packing itself catalyticallyactive. This is the strategy adopted by Flato andHo!mann (1992) and Sundmacher and Ho!mann(1994a,b) wherein the Raschig ring-shaped packings aremade catalytically active; see Fig. 14(a). The catalyst ringscan be prepared by block polymerisation in the annularspace. Their activity is quite high, however, osmoticswelling processes can cause breakage by producing large