Evaluation of shaped V/HY zeolite catalysts in a continuous oxidative-adsorptive desulfurization of dibenzothiophene: Effects of kaolin and pseudo-boehmite as binders

Abstract

A continuous oxidative/adsorptive desulfurization process was developed in a fixed bed reactor filled with shaped catalysts to explore influences of different binders on textural properties acidity of catalysts and hence their performance in the desulfurization of model oil containing 1000 ppmw dibenzothiophene (DBT). The employed catalysts were vanadium/HY zeolite shaped in the cylindrical form with different amounts of kaolin (KL) and pseudo-boehmite (PB) as binders. In contact with binders, the properties of the zeolite alter and the interaction mechanism of the zeolite and binders remains to be studied. Obtained results revealed that binder incorporation had negative effects on the micropores of the zeolite, but in different degrees. PB with smaller sizes could penetrate and block the micropores leading to the significant decrease in the surface area. But KL with larger particle sizes decreased the micropore volume to a lesser extent. In addition, the mesopore volume of the catalysts improved significantly by binder incorporation due to the particle pilling. The zeolite structure was damaged by PB incorporation via removing tetrahedrally coordinated aluminium from the zeolite framework, and lead to increasing weak acidic sites. Whereas, bounding with KL decreased the acidic properties of the catalyst by partially neutralization. KL-bounded samples exhibited poor activity and stability, possibly due to the creating impenetrable outer layer, which hinders DBT diffusion. The most outstanding catalytic performance was obtained with 33 wt% of PB, which contained well-developed mesopore structure and more weak acidic sites, and 91.6 % (DBT) removal was attained at mild conditions using tert-butyl hydroperoxide oxidant.