Multi State Steric Mass Action (MSSMA) Isotherm Ka and Kd Units

Hi There,

I have a question around the units used for simulation of the MSSMA in CADET-Process.

When simulating the MSSMA in cadet-process (using reference concentrations) are the rate constant values that I input into CADET those of the standard or modified coefficients (Table below from Diedrich et al,2017).

The cadet documentation appears to suggest these are the units of the modified rate constants.(Multi-State Steric Mass Action — CADET)

However when looking at the paper by Diedrich et al , 2017 the values for Ka and kd associated with the modified rate constant are very large( around 1x10^31) because of the conversion using CC’s. The values used in CADET-Process simulations are much smaller (around 1e-4 to 1e4) despite having large CCs which seems to suggest they are the standard coefficients?

Getting confused with this one so any help welcome!

Good Morning!

Without having looked deeper into this, I remembered that we actually have a case study example of that paper. Maybe having a look at that already clears up some things?

All the best,
Hannah

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As you showed, the values are large because of the reference concentrations. The specific k_a and k_d inputted to the sim are going to change depending on what the reference concentrations are. The conversion is not done automatically, so if you are trying to reproduce the results from the paper I would just use the same reference concentrations they did.

My personal preference is to do fitting and sampling sims using the untransformed k_{eq}, then in the simulation call set reference concs and the transformed k_a and k_d. This way I find it is much easier to interpret the parameter values, especially for readers when it is published.

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