Self Diffusivity of n-Dodecane and Benzothiophene in ZSM-5 Zeolites. Its Significance for A New Catalytic Light Diesel Desulfurization Process

MARÍA LUJÁN FERREIRA; SAAD AL BOGAMI; HUGO DE LASA

INTERNATIONAL JOURNAL OF CHEMICAL REACTOR ENGINEERING

BERKELEY ELECTRONIC PRESS

Año: 2016 vol. 14 p. 737 - 748

1542-6580

This study provides theoretical support to a recent promising ZSM5 catalyst used for the selective desulfurization of light diesel type compounds(Al-Bogami and de Lasa 2013; Al-Bogami, Moreira, and de Lasa 2013). With this end, Molecular Dynamics (MD) silicalite structure are developed to calculate self-diffusivities of n-Dodecane (n-C12) or Benzothiophene (BZT) in a silicalite structure. The simulations are performed al 573 K, 623 K, 573 K (and 723K) at a fixed loading of 1 molecule per unit cell to study the temperature effect on diffusivity coefficient. In addition, anumber of simulations which are developed to investigate molecule loadings (corresponding to 0.25, 0.5, 0.75 and 1 molecule per zeolite unit cell) at 723 K. MD simulations,show a self diffusivity of BZT one order of magnitude higher than that of n-Ct self diffusivity at all temperatures investigated. This is the case in spite of BZT having a critical molecular diameter of 5 A when compared to the 4.9 A diameter of n-C12. In addition, the self diffusivity coefficient is found to increase with temperature for both n-C12 and BZT. Furthermore, the results obtained show that the self diffusivity of n-C12 decreases as the load of n-C12 molecules per zeolite unit cell increases.On the other hand, it is observed that the self-diffusivity coefficient of BZT remains fairly constant and drops at a loading of 1 molecule per zeolite unit cell only. These coefficients show that differences in n-C12 and benzothiophene diffusivities favours desulfurization with selective benzothiophene adsorption and sulfur species removal as coke.