The hydrotreatment of n-C16 over Pt/HPMo/SBA-15 and the investigation of diffusion effect using a novel W-P criterion

A series of Pt/HPMo/SBA-15 catalysts with the pore size as a single variable were prepared to elucidate the internal diffusion effect on the hydrotreatment of n-C16. A novel model was developed to calculate the Weisz-Prater number (N_W-P) because the traditional model relies on excessive empirical reference values and affects the accuracy remarkably. The utilization of the internal effectiveness factor, Thiele modulus, and the apparent activities over catalysts with different diffusion capacity gave rise to N_W-P with improved accuracy, which can also be extended to other heterogeneous catalytic systems with macromolecules as reactants. Combining the novel model with the diffusion–reaction kinetic method, a conclusion has been drawn that the formation of m-i-C16 is more susceptible to internal diffusion than the consumption of n-C16. Besides, 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.