Question

I was wondering if using pure MEA (Monoethanolamine) or a MEA solution using water would be a better solution for scrubbing CO2

Based on this image, I would think the key reaction would be able to occur with both pure MEA and an MEA solution. However, in this reaction, it takes 2 amines to react with one molecule of CO2
. The other reaction involves water, so I don't think it would be able to take place with pure MEA. It seems to only use 1 amine to react with one molecule of CO2
, so theoretically it would would increase the CO2
:MEA ratio, but I don't know the magnitude of that reaction compared to the main one.

So, it seems that having an aqueous MEA solution might improve efficiency. But the issue with an aqueous solution is that when the MEA is heated to release the CO2, it is above the boiling point of water, so the water would have to be replenished. Therefore, I would like to use pure MEA.

Ultimately, my quesion is:

Is it reasonable to use MEA as a pure liquid rather than in an aqueous solution?

Answer 1

An aqueous MEA solution is more effective for CO2 scrubbing, as it allows for a 1:1 molar reaction with CO2, potentially doubling the capacity for CO2 capture compared to non-solvated MEA. While pure MEA can also capture CO2, it has practical disadvantages such as higher viscosity and handling issues.

Step-by-step explanation:

Using a MEA solution in water for CO2 scrubbing is typically more efficient than using pure MEA. In aqueous solutions, MEA forms a carbamate through a reaction with water and CO2 that uses a 1:1 mole ratio of MEA to CO2. This is a key consideration as it potentially doubles the capacity of MEA to capture CO2 compared to reactions where MEA is not solvated.

Furthermore, using MEA in its pure form may present challenges such as a higher viscosity, making it more difficult to handle and less efficient in terms of mass transfer. The boiling point issue you mentioned is indeed a drawback; however, in industrial settings, water is typically continuously replenished within the system, mitigating that concern. Considering all of this, it is reasonable to conclude that an aqueous MEA solution is preferable for CO2 scrubbing processes.