I need help with interpreting the kinetics of a scientific paper: https://www.researchgate.net/publication/284014208_Kinetic_modelling_of_methanol_conversion_to_light_olefins_process_over_Silicoaluminophosphate_SAPO-34_Catalyst

I am trying to reproduce the reactions in table 1 using a pfr in hysys. However, I am at a loss how to interpret the kinetics data given in table 3. The units given are in (mol gCatalyst−1 atm−1 h−1) which do not make much sense to me. I thought a 2nd order rate constant should have units of atm-1 h-1. Hence, I am unsure how to input the rate kinetics data.

Any help would be greatly appreciated.

Thank you!

  • 1
    $\begingroup$ I can't help with your question, but putting a paper out there like this might violate the distribution rights reserved by Elsevier. $\endgroup$
    – Eric S
    Jan 21, 2017 at 19:57
  • $\begingroup$ Yeah, this isn't an open-access article, as seen by the fact that you need to purchase it to read it from sciencedirect. $\endgroup$
    – Wasabi
    Jan 21, 2017 at 22:15
  • $\begingroup$ Ok, I have edited the link to an open-access source from researchgate. :) $\endgroup$ Jan 22, 2017 at 2:29

2 Answers 2


The 'mol gCatalyst^-1' (or "per gmol catalyst") comes from the phenomenon (in this case) of the rate constant being a function of the catalyst they're using. That is, the rate constant of the given reaction is affected by the mass of catalyst present. In undergraduate-level CME reactor design courses, this typically comes up when designing packed bed reactors (http://umich.edu/~elements/asyLearn/bits/pbr/index.htm).

Because it's raised to the -1 power here, it suggests that the rate law is some form of a typical second-order rate law multiplied by the catalyst mass raised to the 1 power. See the link for how this would relate to a PBR (PFR with catalyst).

Without looking too deeply into the article, it looks like they're using a bed of catalyst particles, but instead of specifying a bulk density, they specify the particle size and the particle surface area per mass catalyst (which can easily be used to determine the catalyst concentration of the particles by using conc=[mass catalyst/SA]*[SA of sphere/Volume of sphere]), but I'm not sure whether or not they used that directly in their modeling or modified it to get some sort of bulk density value.


My guess is (mol catalyst)^-1^-1(hr)^-1

"(mol catalyst)^-1" meaning : per gram-mol (which is just a regular mole, not to be confused with a pound mole) of catalyst material.


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