The Effect of Diffusion on the Hydrotreatment of n-C16: A Novel Method
to Calculate the Weisz-Prater Number
Abstract
Weisz-Prater number (NW-P) is often applied to assess the internal
diffusion effect in heterogeneous catalytic reactions. However, the
traditional calculation method with excessive empirical reference values
affects the accuracy remarkably. A series of Pt/HPMo/SBA-15 catalysts
with the pore size as a single variable were prepared to calculate the
NW-P with a developed model combining the diffusion-reaction kinetic
method. Utilizing dimensionless variables, internal effectiveness factor
(η) and Thiele modulus (Φ_n), and the apparent activities over
catalysts with different diffusion capacity, NW-P is obtained with
improved accuracy. For the diffusion effect on the hydrotreatment of
n-C16, according to the more precise NW-P, the pore size should be not
less than 10 nm to avoid the step-limitation of internal diffusion in
the premise of adequate acid sites. Using the novel method, a conclusion
is drawn that the formation of m-i-C16 is more susceptible to internal
diffusion than the consumption of n-C16.