Applications of the degree of rate control (DRC) in catalysis research will be reviewed. It was initially designed as a tool for sensitivity analysis of microkinetic models to determine which elementary step(s) are the kinetic bottlenecks, i.e., the most rate controlling. It was later generalized such that it quantifies, in a thermodynamically consistent way, the sensitivities of the net reaction rate to a small change in the energy of each species in the reaction mechanism. Thus, the DRC for any elementary step’s transition state or for any adsorbed intermediate is defined such that it equals the fractional increase in the net rate that results from a tiny decrease in the energy of that species, keeping all other energies and entropies constant. When there is a single rate-determining step, the DRC for its transition state is unity. The applications of DRC analysis of catalytic reaction mechanisms will be reviewed. These include: (1) determining which species are most critical in affecting the desired rate or selectivity, (2) guiding changes in reaction conditions to achieve higher rates and selectivities, (3) an algorithm based on DRCs, developed by Dumesic’s group, which bypasses the need to solve the differential equations in a microkinetic model to calculate its rates, (4) a method for fast computational catalyst screening, which uses the energies of the few species with the highest DRCs for a reference catalyst as descriptors to estimate the rates on related materials, and to predict which are most active or selective. It can also be implemented without a microkinetic model if the degrees of rate control are already known from experiments.

Degree of rate control: A tool for analyzing microkinetic models and high-throughput computational screening of catalyst materials

253rd National Meeting (2017)

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