Various W and Mo co-doped titanium dioxide (TiO2) materials were obtained through the EISA (Evaporation-Induced Self-Assembly) method and then tested as photocatalysts in the degradation of 4-chlorophenol. The synthesized materials were characterized by thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), Raman spectroscopy (RS), N2 physisorption, UV-vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The results showed that the W-Mo-TiO2 catalysts have a high surface area of about 191 m2/g, and the presence of an anatase crystalline phase. The co-doped materials exhibited smaller crystallite sizes than those with one dopant, since the crystallinity is inhibited by the presence of both species. In addition, tungsten and molybdenum dopants are distributed and are incorporated into the anatase structure of TiO2, due to changes in red parameters and lattice expansion. Under our experimental conditions, the co-doped TiO2 catalyst presented 46% more 4-chlorophenol degradation than Degussa P25. The incorporation of two dopant cations in titania improved its photocatalytic performance, which was attributed to a cooperative effect by decreasing the recombination of photogenerated charges, high radiation absorption capacity, high surface areas, and low crystallinity. When TiO2 is co-doped with the same amount of both cations (1 wt.%), the highest degradation and mineralization (97% and 74%, respectively) is achieved. Quinones were the main intermediates in the 4-chlorophenol oxidation by W-Mo-TiO2 and 1,2,4-benzenetriol was incompletely degraded.
In this work, two series of trimetallic NiMoW sulfide catalysts supported on Al–Mg(x) and Ti–Mg(x) mixed oxides with different content of MgO (x = 5, 10, 15 and 20 wt.% of MgO) were synthesized. The mixed oxides and catalysts were characterized by X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, N2 physisorption and Diffuse reflectance spectroscopy (DRS UV–Vis); and evaluated during the hydrodesulfurization (HDS) of dibenzothiophene (DBT) reaction. The NiMoW/Al–Mg catalysts showed a higher dispersion of Ni, Mo and W species than NiMoW/Ti–Mg catalysts resulting in higher catalytic activities. Catalysts with 10 wt.% of MgO showed the highest catalytic activity for both series of catalysts. Most of the synthesized catalysts exhibited higher activities than NiMoWS/Al–Ti reference catalyst. The present comparison study clearly showed that NiMoW/Al–Mg and NiMoW/Ti–Mg catalyst with 10 wt.% of MgO might be a promising and effective catalyst for the HDS-DBT reaction.
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