20.3.4 Technical questions

1.  The flow sheet presented corresponds to production of butanol from propylene. If higher order alcohols are desired, how does the flow sheet get modified ?

Ans: An additional unit process entitled “Dimerization” will be part of the flow sheet. In such case, the cold liquid stream from the phase separator enters the dimerization reactor to convert lower order aldehydes to higher order aldehydes.

2.  Suppose we wish to produce both short chain and long chain aldehydes and do not wish to produce alcohols then how does the process topology change ?

Ans: When both short and long chain aldehydes are required, then we have to allow the cold liquid from the phase separator to enter the dimerization reactor partially only. Then the dimerization reactor product as well as the phase separator stream enter the decatalization unit to achieve catalyst recovery.

3. Can the hydroformylation reactor be used as a dimerization reactor as well ?

Ans: Yes, in this way, we can produce all desired products in a single reactor and we can avoid dimerization reactor. But the balance between cobalt and zinc catalysts will dictate the product composition palette.

4. Why high pressure is required in the hydroformylation reactor ?

Ans: Higher pressures enable the formation of a complex between Cobalt and the hydrocarbons participating in the reaction. If higher pressure is not existent, the cobalt complex can decompose and this does not favour higher conversions.

5. Can the series of distillation columns in the separator network be replaced with a complex distillation column ?

Ans: Yes, this is possible and this is recommended as the light end and heavy end products are not significant in make and the aldehyde products are the actual products that are desired. A complex distillation reduces the number of columns required, enables complex interaction between both vapour and liquid streams and facilitates drastic reduction in the cost.

 

References:

1. Dryden C. E., Outlines of Chemical Technology, East-West Press, 2008

2. Kirk R. E., Othmer D. F., Encyclopedia of Chemical Technology, John Wiley and Sons, 1999-2012