19.2.3 Technical questions

1. What alternative reactor arrangement is possible if pure propylene feed is used ?

Ans:When pure propylene is used, then there is no propane for quenching. Therefore, the packed bed reactor shall be provided a cooling jacket which can control the temperature of the reactor.

2. Comment on the sequence of distillation columns separating propane, benzene and cumene in series ?

Ans:The distillation columns are so arranged so that lighter components are separated first followed by heavier components. Since no component is present which will decompose on long time heating, this arrangement is followed. If not, the component which can decompose upon long time heating will be separated first following by the lighter to heavier component sequence in the remaining components.

3. In what way propane quenching plays a role in the reactions ?

Ans: Propane quenching reduces polymerization of cumene and formation of polyalkyl benzenes.

4. How can one suppress polyalkylbenzene formation ?

Ans: By using high feed ratio of benzene to propylene and using propane as a diluent.

5.  Is further heat integration not possible ?

Ans: A further heat integration can be carried out using hot vapors in the distillation column to be as hot streams in the reboilers of various distillation columns.

6. In what way higher pressure in the product vapors from the reactor are beneficial for the deprpopanizer unit ?

Ans: The depropanizer unit requires condensation of propane vapors in the condenser. Propane's boiling point is less than 0°C at 1 atm pressure. Therefore, higher pressures to the extent of 25 atms will enhance propane boiling point to about 25 – 30°C for which cooling water can be used as the cooling media in the condenser. If not, refrigerant needs to be used and the refrigerant will require a refrigerating unit along with the process. This is much much expensive than using cooling water as the cooling media.