It's better to use common phrases in catalytic reactions such as LHSV or GHSV instead of concentration. The conversion and specific rate or TNF must be determined for the catalyst. It's clear that your catalyst has a maximum activity like other catalysts according to volcano principle.

Mohammad Reza Toosi Thank you again for the reply in my other questions. Can you tell me what is the volcano principle? Do you have any papers introducing that?

Thanks.

You can find more details in G. C. Bond's textbook about heterogeneous catalysis.

Mohammad Reza Toosi Thanks! I will do that.

Please note that in your case you must identify type of catalytic reaction as mass transfer limited or kinetic limited case. It generally depends to nature of zeolite channels and their size. Internal diameter of ZSM-5 is about 5 angstroms so what do you think about diffusion rate of methanol molecules?

A link for simple description about volcano principle https://en.m.wikipedia.org/wiki/Sabatier_principle

Mohammad Reza Toosi Thank you so much!

In summary, you have to consider two main factors: kinetic problems about the rate of diffusion and thermodynamic factors acting on the conversion and reaction yield.

Mohammad Reza Toosi OK, thanks.

You're welcome