CO2 purification using NaOH 3

[hadidster]

how hot does CO2 have to be to react with NaOH to form NaHCO3?

 

[m777182]

Kinetics is temperature dependat in any case but this type of gas liquid reaction is governed by diffusion control so that the overall transfer or reaction rate will depend on gas liquid interface.
m777182

 

[25362]

The formation of the bicarbonate is strongly dependent on the pH of the NaOH solution. At 25^oC, and pH=10.3, the carbonate and bicarbonate species are in the ratio of about 1:1.

At a pH=8.5 one can say that it is about 100% bicarbonate.

Below about pH=8 the carbonate disappears and the carbonic acid (from carbon dioxide solvation) group shows up. At pH=7 bicarbonate and carbonic acid are in a 75:25 ratio.

At pH=12 carbonate to bicarbonate are about 95:5. Please notice that CO₂ solubility in water increases with partial pressure and drops with increasing temperatures. See the CRC Handbook of Chemistry and Physics for solubility data.

 

[brainstorming]

Good example would be removal of acid gases in ethylene purification unit (one of ethylene units)
The solution used is 20% NaOH diluted into two levels (strong 10% and weak 4%) and they are circulated in individual sections in a column (packing or traying)
the important parameter is the pH os the solution which will deterimine the degree removal or complete reaction of CO2 (or H2S) into sodium carbonates (or sodium sulphates)
Also, the temperature is another factor as well.