I have a question about whether a particular situation qualifies as a rate limiting step. I have a catalyst that under normal conditions gets poisoned when products accumulate on the catalyst surface. I interpret that as the product desorption as being a rate limiting step, but is that true?

I also thought that that a rate limiting step means that the rate of the reaction equals the rate of that step, but in reality what I see is that the initial rate in the case where the product sticks and when you can desorb the product is the same, but just that you get an abrupt halt in reactivity once the catalyst is full of product. Conversely, by tweaking the conditions where i can cause the product to desorb it just will keep that initial rate up for 10,000 times longer.

Does that still mean that product desorption is a RLS or is there a better way to describe this poisoning event?




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