Acetic Acid Production Plant. Cativa Process

[Pilargalizia]

Hello, I am a final-year Chemical Engineering student, and I am currently working on my thesis about an acetic acid production plant based on the Cativa process.

I am having some issues when trying to simulate the process, since I do not know how to properly define the dissolved solid catalyst in UniSim so that, in the flash separator, all of the liquid catalyst leaves through the bottom stream while the acetic acid leaves through the top stream.

Could anyone help me with this, or does anyone have this process simulated in UniSim, Aspen HYSYS, or any other process simulation software?

[email protected]

 

[Alan]

Welcome! Glad to have a fellow process simulation enthusiast here. The Cativa process can be tricky to model, especially getting the catalyst behavior right in UniSim. Have you tried defining the catalyst as a non-conventional component or looking into the electrolyte models available in the software?

 

[Pilargalizia]

Hi! Thank you for your reply.


I am using the NRTL thermodynamic package. I modeled the ruthenium-promoted iridium catalyst as a hypothetical component. Although the catalyst itself is a solid, it is dissolved in acetic acid under the process conditions, so I need to represent it as part of the liquid phase.


My main difficulty is determining which physical properties should be assigned to this hypothetical component, since I have not been able to find enough information in the literature.


So far, I have tried using a normal boiling point of approximately 700 °C, together with viscosity and density values similar to those of acetic acid, considering that the catalyst is present at a very low concentration and is dissolved in it. However, I am not sure whether this is an appropriate modeling approach.


Do you have any recommendations regarding which properties should be specified, or a better way to represent the dissolved catalyst in UniSim?