Weisz–Prater criterion

The Weisz–Prater criterion is a method used to estimate the influence of pore diffusion on reaction rates in heterogeneous catalytic reactions.

[1] If the criterion is satisfied, pore diffusion limitations are negligible.

{\displaystyle N_{W-P}={\dfrac {{\mathfrak {R}}R_{p}^{2}}{C_{s}D_{eff}}}\leq 3\beta }

is the reaction rate per volume of catalyst,

is the catalyst particle radius,

is the reactant concentration at the particle surface, and

Diffusion is usually in the Knudsen regime when average pore radius is less than 100 nm.

For a given effectiveness factor,

, and reaction order, n, the quantity

is defined by the equation:

for small values of beta this can be approximated using the binomial theorem:

with a reaction order

then pore diffusion limitations can be excluded.