Examples of PI where reactions are combined with separation operations include

1. Reactive distillation. To avoid conversion of product into unwanted components or to drive equilibrium reactions forward, reactive distillation is used to distill out one of the products immediately as it is formed. A conventional equilibrium process consists of a reactor and a distillation column. One of the pro ducts is removed in the column, and the bottom is recycled (see Fig. 6.22). In reactive distillation the column is located on top of the reactor, obviating the need for a reboiler (see Fig. 6.23). Reaction of an organic chlorine compound with an aqueous caustic solution can be carried out in a reactive distillation column, which will combine functions such as dissolution of alkaline solution, reaction, separation of product from the reaction mixture, through evaporation into the gas phase.

2. Precipitative cum evaporative reactor. This design combines several functions such as reaction, solvent removal by evaporation from the reaction mixture, and separation of solid product by precipitation from the reaction mixture. This design eliminates byproduct formation and controls the crystal size distribution accurately.

3. Liquid liquid extraction reactor. This combines the functions of liquid liquid extraction and reaction. The process involves alkaline transfer to the reaction phase, reaction, and extraction of salt to the aqueous phase.

4. Reaction cum pervaporation. This technology can be used for dewatering of organics, which is the removal of organics from waste water in place of the conventional distillation operation. A membrane is the heart of the...