TiO2 nanomaterials with platelet or nanosheet morphologies can offer improved properties for photocatalytic applications, but established methods to produce them typically require structure-directing agents since anatase-phase TiO2 does not have a layered structure. In the present work, the preparation of TiO2 nanosheets by the chemical oxidation of TiS2 nanosheets is demonstrated. Electrochemical exfoliation of bulk TiS2 into TiS2 nanosheets, followed by the hydrothermal treatment at 180 °C for 14 h is performed. The results show that polycrystalline TiO2 nanosheets with the anatase structure are formed, and that the nanosheet morphology can still be maintained after the hydrothermal treatment. The TiO2 nanosheets show good photocatalytic activity for the degradation of methylene blue, but the performance is negatively affected by the residual carbon black that was needed in the TiS2 electrode to enable electrochemical exfoliation. These results show that conversion of TiS2 nanosheets to TiO2 nanosheets is a promising synthetic strategy but highlights how the interfacial properties of the obtained materials could be affected by ancillary components in the preparation method.

Activation of persulfate (PS) by ultraviolet light or transition metal catalysts has been extensively studied. However, little is known about the activation of PS by iron oxychloride (FeOCl) in the presence of visible light irradiation. Herein, the catalytic activity of FeOCl was developed for oxidative degradation of rhodamine B (RhB) with the FeOCl/PS/Vis process. The characterization of FeOCl for reaction kinetics, degradation mechanism, and catalyst stability was investigated. It is found that the redox cycle of iron species and photoinduced electrons formed on the FeOCl catalyst surface can effectively activate PS, to generate radicals. Based on quenching experiments and electron paramagnetic resonance, the photogenerated holes (h+) and sulfate radicals (SO4−•) are the predominant reactive oxidants for RhB decolorization, while superoxide radicals (•O2−) and hydroxyl radicals (•OH) are also involved. Moreover, FeOCl shows good catalytic performance in a wide range of pH values (pH = 3–10) and excellent reusability and stability, as well.

Novel cerium-loaded MnTiOx/attapulgite (Ce/MnTiOx/ATP) and cerium-doped MnTiOx/attapulgite (Ce–MnTiOx/ATP) catalysts for low-temperature selective catalytic reduction of nitrogen oxides (NOx) with ammonia (NH3-SCR) were synthesized by co-precipitation methods. The results of catalytic activity testing for the as-prepared Ce–MnTiOx/ATP and Ce/MnTiOx/ATP indicated that the Ce–MnTiOx/ATP catalyst exhibited better catalytic performance with over 80% NOx conversion within a wide temperature window between 170 and 350°, and the highest NOx conversion attained for the Ce–MnTiOx/ATP catalyst was 97.5%. A series of characterization illustrated that the Ce–MnTiOx/ATP catalyst exhibited a higher specific surface area, oxygen vacancy, redox ability, and acid site as compared to that of the Ce/MnTiOx/ATP catalyst. The performance tests showed that the Ce–MnTiOx/ATP catalyst exhibited not only better SO2 & H2O resistance but also higher N2 selectivity and good stability. Therefore, the Ce–MnTiOx/ATP catalyst was testified to be a promising catalyst for NH3-SCR.

The changes in hydrodesulfurization activity, selectivity, dispersion, sulfidation, and extent of promotion of Co(Ni)Mo catalysts were investigated when the alumina support surface is modified by grafting 4 wt% silica. Adding SiO2 eliminates the most reactive hydroxyl groups on the alumina surface (IR band at 3775 cm−1) decreasing the possibility of generating tetrahedral Mo species difficult to sulfide in favor of octahedral ones capable of contributing to the sulfided active phase. The catalysts were evaluated in the hydrodesulfurization of 4,6-dimethyldibenzothiophene. Incorporating SiO2 to alumina increases the hydrogenation rate constant and therefore the global hydrodesulfurization rate of 4,6-dimethyldibenzothiophene and enhances the promotion of Mo by Co (or Ni). The global sulfidation of Ni is not affected by the addition of silica but the sulfidation of cobalt is significantly improved. The extent of promotion of the NiMo/Al2O3 and NiMo/SiO2/Al2O3 catalysts was greater than the one achieved in their Co-promoted counterparts.

Ni2P/ZnS and Ni2P/CdS core/shell composites were synthesized using a simple two-step route at a low temperature. We used X-ray powder diffraction, scanning electron microscopy, energy dispersive spectroscopy, and so on to characterize their composition, structure, and morphology. The characterized results show that Ni2P/ZnS and Ni2P/CdS core/shell composites consist of Ni2P microsphere core and ZnS (or CdS) nanostructure shell, and CdS nanorods and ZnS nanoparticles are deposited on the surface of Ni2P microspheres, respectively. Then choosing methylene blue (MB) as a typical organic dye, the photocatalytic degradation activities of Ni2P/ZnS and Ni2P/CdS are investigated, which exhibit a good photocatalytic activity. When the concentration of MB solution is 1 × 10−5 mol/L and the mass of the added photocatalyst is 0.05 g, it is found that two composites have enhanced photocatalytic degradation ratios (89 and 78%) compared to that of Ni2P microsphere (65%), which might be due to the effective separation of photogenerated electron-hole pairs.

Combining density functional theory calculations and temperature programmed desorption (TPD) experiments, the adsorption behavior of various sulfur containing compounds, including C2H5SH, CH3SCH3, tetrahydrothiophene, thiophene, benzothiophene, dibenzothiophene, and their derivatives on the coordinately unsaturated sites of Mo27Sx model nanoparticles, are studied systematically. Sulfur molecules with aromaticity prefer flat adsorption than perpendicular adsorption. The adsorption of nonaromatic molecules is stronger than the perpendicular adsorption of aromatic molecules, but weaker than the flat adsorption of them. With gradual hydrogenation (HYD), the binding affinity in the perpendicular adsorption modes increases, while in flat adsorption modes it increases first, then decreases. Significant steric effects on the adsorption of dimethyldibenzothiophene were revealed in perpendicular adsorption modes. The steric effect, besides weakening adsorption, could also activate the S–C bonds through a compensation effect. Finally, by comparing the theoretical adsorption energies with the TPD results, we suggest that HYD and direct-desulfurization path may happen simultaneously, but on different active sites.

Molybdenum sulfide hydrotreating catalysts promoted with nickel over tridimensional mesoporous silica (KIT-6 post synthesis modified with alumina) were prepared with three different chelating agents. Citric acid and EDTA (ethylenediaminetetraacetic acid) were used as typical chelates and the new suggestion, polyacrylic acid as a polymeric agent. The catalysts were synthesized by the incipient wetness impregnation method, and two different activation methods were applied to determine the correlation between the chelating agent and activation conditions. The beneficial use of chelating agents was evaluated in their performance on HDS (hydrodesulfurization) of DBT (dibenzothiophene). To determine the properties of catalysts, nitrogen physisorption, X-ray diffraction, HRTEM (high-resolution transmission electron microscopy), and TGA (thermogravimetric analysis) were used. The beneficial effect of chelating Ni during impregnation to avoid NiSx formation and thus promoting NiMoS arrangement was clearly observed in the catalytic HDS performance, and the TGA analysis of Ni-chelate complexes also confirms this theory. The catalyst with the best performance in the HDS reaction of DBT was the synthesized with citric acid and a slow rate temperature sulfidation.

ZnAl–Zr(X) hydrotalcite-like materials were synthesized by co-precipitation using a Zn/Al molar ratio of 2 and Zr/Al(X) molar ratios of 0.0, 0.10, and 0.25. The effect of the activation temperature on the catalytic performance of these materials was analyzed, revealing that at relatively low temperature (200 °C), the collapse of the material structure is diminished, leading to FAME yields varying from 68 to 82%. This remarkable catalytic activity is related to the formation of hydrotalcite, zincite, and hydrozincite which in turn lead to the generation of Brönsted basic sites and Lewis acid–basic pairs. Incorporation of Zr+4 into the brucite-like structure of hydrotalcites enhances the basicity of ZnAl–Zr(X) catalysts, which correlates well with the increase in catalytic activity observed for these catalysts. The stability of the ZnAl–Zr(0.25) catalyst was further studied, showing insignificant deactivation after five subsequent reaction cycles. A simplified reaction scheme was proposed for the transesterification reaction over these materials.

Highly porous alumina-based oxides, γ-Al2O3, SiO2–Al2O3, and TiO2–Al2O3 were synthesized by a modified sol–gel method. Polivinylpyrrolidone was used as the pore expanding agent, whereas cetyltrimethylammonium bromide was used as the template in the presence of alkoxide inorganic precursors. Both as-synthesized and calcined solids were used as catalysts for esterification of glycerol with acetic acid (EG). The XRD and SEM-EDS measurements demonstrated that the Si-containing solids are amorphous while those containing Ti are semicrystalline with the latter composed of TiO2 rutile, TiO2 anatase, and γ-Al2O3 phases. All solids possessed ordered porous structures comprising of micro- and mesoporosity, with interconnectivity between these pores of different length scales. The high acidity of γ-Al2O3 and TiO2–Al2O3 materials resulted in good catalytic performances in the EG. Porosity of the solids plays a secondary role in determining the catalytic activity. Under the same conditions, the as-synthesized solids exhibited slightly lower catalytic performances compared to that of the calcined ones.

The acidity of SBA-15 was tuned with the incorporation of Al+3, Ti+4, and –PrSO3H groups through sol–gel, employing molar ratios of Si/M = 10 (M = Al, Ti) and Si/S = 10. This results in mesoporous materials with the typical hexagonal structure of SBA-15, large surface areas, and great pore diameter. The incorporation of Al+3 and Ti+4 mainly leads to catalysts with both Brönsted and Lewis acid sites. The addition of sulfonic groups to these samples enhanced their surface acidity, creating preferentially Brönsted acid sites. Among the evaluated catalysts, the SBA-15-SO3H showed the highest catalytic activity, which was related to the high concentration of Lewis acid sites, and a remarkable resistance to deactivation, probably due to its low hydrophilicity. A first order kinetic equation fits well the experimental data and an activation energy of 31.5 kJ/mol similar to other reports for this reaction was calculated for the SBA-15-SO3H catalyst.

To study the effects of the support morphology on the hydrodesulfurization (HDS) activity of NiMoS catalysts, ordered mesoporous SiO2 (KIT-6) and nonporous nanospheres of SiO2 were used as supports. Metal species (Ni and Mo) were incorporated through a sequential impregnation technique. The aqueous solution of nickel nitrate was introduced first on the supports, followed by the solution of ammonium molybdate. Subsequently, a sulfidation treatment was carried out in gaseous H2S/H2 atmosphere. The NiMo/Al2O3 commercial catalyst was used as reference. The materials obtained were characterized by N2 physisorption, X-ray diffraction (XRD), and high-resolution transmission electron microscopy (HRTEM) and evaluated in the HDS catalytic reaction of dibenzothiophene in a batch reactor. The results indicate that the textural properties of KIT-6 were the key factors to obtain disperse NiMoS stacks, and a better metal sulfidation, which lead to a higher catalytic activity of the NiMo/KIT-6 catalyst (twice as active) compared to the NiMo/Nanosilica catalyst. In addition, the activity of the NiMo/KIT-6 catalyst was also superior to that obtained for the commercial catalyst.