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Weisz-Prater Criterion : ウィキペディア英語版
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. If the criterion is satisfied, pore diffusion limitations are negligible. The criterion is

N_ = \dfrac is the reaction rate per volume of catalyst, R_p is the catalyst particle radius, C_s is the reactant concentration at the particle surface, and D_ is the effective diffusivity. Diffusion is usually in the Knudsen regime when average pore radius is less than 100 nm.

For a given effectiveness factor,\eta, and reaction order, n, the quantity \beta is defined by the equation:

\eta = \dfrac \int_^ ((1-r/R_p)^n ) r^2\ dr

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

\eta = 1-\dfrac

Assuming \eta \ge 0.95 with a 1st or zero order reaction gives values of \beta, 0.6 and 6 respectively. Therefore for many conditions, if N_ \le 0.3 then pore diffusion limitations can be excluded.
== References ==


抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)
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