Chemical reaction kinetics is an essential analysis conducted on reaction rates and profiles to better understand the behavior of a chemical system with respect to some predefined conditions. These kinetic insights play an important role in informing and improving chemical reactor design as well as in refining and optimizing catalyst selection. In deriving useful kinetic information, the concept of ‘Rate-Determining Step (RDS)’ is ubiquitous in characterizing the step in the reaction mechanism that when perturbed, would have the most significant effect on the kinetics of the overall reaction. There are many ways to characterize a significant kinetic effect and consequently, there exists several different qualitative and qualitative approaches to identifying the RDS; some of which have significant limitations and shortcomings.

Out of all the different approaches of obtaining the RDS, Campbell’s degree of rate control shows to give the most reliable description of which steps would be the most kinetically relevant. Using a numerical finite difference approach, we can easily perform transient rate control analysis and obtain information on which steps are kinetically relevant and would, if accelerated, positively impact the overall net rate of reaction. In the example used, we were able to see that before reaching steady state, there was significant changes in the different step’s kinetic relevance (degrees of rate control) of which can be attributed to the changes in surface coverage. The transient degree of rate control tool can therefore be used to fine tune the process of identifying a selective catalyst or catalyst additive that would help improve the overall reaction kinetics as needed.