V Loading Effect on V2O5/ZrO2 Catalysts for Oxidative Desulfurization

Ultrasound-Assisted Hydrothermal Synthesis of V2O5/Zr-SBA-15 Catalysts for Production of Ultralow Sulfur Fuel

This work reports the results of the ultrasound-assisted hydrothermal synthesis of two sets of V2O5 dispersed on SBA-15 and Zr doped SBA-15 catalysts used for the oxidation of dibenzothiophene (DBT) in a model diesel via the combination of oxidation, catalysis, and extraction technical route. These catalysts contained Lewis acidity as major and Brønsted acidity as minor. The amount of acidity varied with the content of vanadia and zirconium doping. It was found that DBT conversion is very sensitive to the Lewis acidity. DBT conversion increased by increasing the vanadium content and correlated well with the amount of surface Lewis acidity. Under the optimal experimental condition (Reaction temperature: 60 °C, reaction time 40 min, catalyst concentration: 1 g/L oil; H2O2/DBT mole ratio = 10), the 30% V2O5/SBA-15 and 30% V2O5/Zr-SBA-15 catalysts could convert more than 99% of DBT. Two reaction pathways of DBT oxidation involving vanadia surface structure, Lewis acidity, and peroxometallic complexes were proposed. When the vanadia loading V2O5 ≤ 10 wt%, the oxidative desulfurization (ODS) went through the Pathway I; in the catalysts with moderate vanadia content (V2O5 = 20–30 wt%), ODS proceeded via the Pathways II or/and the Pathway I.

Direct Ink Writing of Metal Oxide/H-ZSM-5 Catalysts for n-Hexane Cracking: A New Method of Additive Manufacturing with High Metal Oxide Loading

Previously, 3D printing of porous materials and metal oxides was limited to low loading metal loadings, as increasing the nitrate salt concentrations, which are used to generate the oxide component, gave rise to poor rheological properties beyond 10 wt %. In this study, we addressed this problem by directly printing insoluble oxides alongside H-ZSM-5 zeolite, which allowed for increased oxide loadings. Various metal oxides such as V₂O₅, ZrO₂, Cr₂O₃, and Ga₂O₃ were doped onto H-ZSM-5 through the additive manufacturing method. Characterization and correlation between the X-ray diffraction, NH₃-temperature-programmed desorption, O₂-temperature programmed oxidation, temperature-programmed reduction, scanning electron microscopy-energy dispersive spectroscopy, and in situ CO₂ DRIFTS experiments revealed that directly 3D printing metal oxides/H-ZSM-5 inks leads to significant modification in the surface properties and oxide bulk dispersion, thereby enhancing the composites' reducibility and giving rise to widely differing product distributions in n-hexane cracking reaction. The obtained metal oxide/zeolite structured materials were used as bifunctional structured catalysts for the selective formation of light olefins from hexane at 550-600 °C and GHSV = 9000 mL/g_catalst·h in a packed-bed reactor. Among the various compositions of metal oxides/H-ZSM-5 examined (i.e., 15 wt % Ga₂O₃, 15 wt % ZrO₂, 15 wt % V₂O₅, 15 wt % Cr₂O₃, or 5 wt % Cr/10 wt % ZrO₂/10 wt % V₂O₅/10 wt % Ga₂O₃ balanced with H-ZSM-5), the 15 wt % Cr/ZSM-5 monolith displayed the best n-hexane cracking performance, as it achieved 80-85% conversion of hexane with a 40% selectivity toward propylene, 30% selectivity toward ethylene, and 10% selectivity toward butene at 550 °C. The sample also showed zero benzene/toluene/xylene selectivity and no deactivation after 6 h. This study represents a proof-of-concept for tailoring customizable heterogeneous structured catalysts by directly 3D printing high loading of metal oxides/porous zeolite and is a breakthrough in material science.

Investigation of the effect of VOx/ZrO2 structure on the catalytic activity in cyclohexene epoxidation

The coexistence of a solid solution with polymeric vanadium species in the case of 5VZr-2 and with the formation of ZrV₂O₇ in the case of 5VZr-3, resulted in good catalytic performance, with up to 80% epoxide selectivity and 32% cyclohexene conversion.