Selective catalytic oxidation of sulfides to sulfoxides or sulfones over amorphous Nb2O5/AC catalysts in aqueous phase at room temperature

PhSe(O)OH/Al(NO3)3-Catalyzed selectivity controllable oxidation of sulphide owing to the synergistic effect of Se, Al3+ and nitrate

Catalyzed by PhSe(O)OH/Al(NO3)3, selective oxidation of sulphides to produce sulfoxides or sulphones could be achieved under mild conditions. The synergistic effect of Se, Al3+ and nitrate is the key factor for the reaction.

Constructing anatase TiO2/Amorphous Nb2O5 heterostructures to enhance photocatalytic degradation of acetaminophen and nitrogen oxide

TiO₂ nanostructures have been one of the most explored metal oxides photocatalysts to apply for environmental remediation. However, its wide band gap results in the underutilization of sunlight for degradation of pollutants. In order to overcome this handicap, the synthesis of TiO₂-based composite has brought extraordinary materials. In this study, we design and prepare TiO₂/Nb₂O₅ heterostructures with different molar ratios by using peroxotitanium and peroxoniobium complex as precursors in aqueous solution. The TiO₂ exists in the form of anatase while Nb₂O₅ is amorphous in the composite, leading to a special crystalline TiO₂/amorphous Nb₂O₅ heterostructures. In particular, Nb element is also doped and Ti³⁺ ions are formed in the TiO₂ lattice, leading to a reduced band gap. The unique TiO₂/0.25Nb₂O₅ (Ti:Nb = 2:1) heterostructures can effectively suppress the recombination of photogenerated electrons and holes, and facilitate the charge transfer, resulting in the optimum photocatalytic performance. The nitrogen oxide removal efficiency by TiO₂/0.25Nb₂O₅ is 77.23% in visible light, which is 3.8-folds and 7.0-folds higher than pure TiO₂ and Nb₂O_5. Photocatalytic degradation of acetaminophen by TiO₂/0.25Nb₂O₅ is 90.6% in visible light, which is approximately 2.5-folds higher than pure TiO₂ and Nb₂O₅.

Degradation of odorous sulfide compounds by different oxidation processes in drinking water: Performance, reaction kinetics and mechanism

Swampy/septic odor caused by various sulfides is one of the most frequently encountered odor problems in drinking water. However, even though it is much more offensive, few studies have specifically focused on swampy/septic odor compared to the extensively studied musty/earthy problems. In this work, four sulfide odorants, diamyl sulfide (DAS), dipropyl sulfide (DPS), dimethyl disulfide (DMDS) and diethyl disulfide (DEDS), were selected to evaluate the treatment performance of different oxidation processes in drinking water. The results demonstrated that DMDS, DEDS, DPS and DAS could be oxidized effectively by KMnO_4, NaClO and ClO₂. The oxidation processes could be well described by the second-order kinetic model, in which k values of selected sulfides followed the order DMDS≈DEDS ≪ DPS≈DAS. As for the three oxidants, the order of reactivity was KMnO₄ ≪ ClO₂ < NaClO, which was also verified in raw water. The results of oxidation treatability, reaction kinetics and mechanisms confirmed that the characteristics of the central sulfur atom rather than the side chain is the decisive factor in controlling the oxidation rate and transformation pathway of sulfides. The transformation products and pathways were significantly different for the three oxidants. Sulfones (DPSO, DASO) were always formed by cycloaddition reactions during KMnO₄ oxidation, yet recombination reactions proceeded during ClO₂ oxidation and formed more products, such as MADS, DADS and EADS. Density functional theory (DFT) calculations confirmed that the differences in transformation pathways were caused by the variations in the activity of the oxidants and sulfides. Finally, NaClO was certified as the most effective oxidant for controlling sulfide odorants in drinking water treatment.

Arylation of indoles using cyclohexanones dually-catalyzed by niobic acid and palladium-on-carbons

3-Arylindoles were easily constructed from indoles and cyclohexanone derivatives using a combination of catalytic niobic acid-on-carbon (Nb₂O₅/C) and palladium-on-carbon (Pd/C) under heating conditions without any oxidants. The Lewis acidic Nb₂O₅/C promoted the nucleophilic addition of indoles to the cyclohexanones, and the subsequent dehydration and Pd/C-catalyzed dehydrogenation produced the 3-arylindoles. The additive 2,3-dimethyl-1,3-butadiene worked as a hydrogen acceptor to facilitate the dehydrogenation step.

Unraveling the role of the lacunar Na7PW11O39 catalyst in the oxidation of terpene alcohols with hydrogen peroxide at room temperature

The Na₇PW₁₁O₃₉ lacunar salt was the most active among Keggin lacunar salts (Na₈SiW₁₁O₃₉ and Na₇PMo₁₁O₃₉), a saturated salt (Na₇PW₁₂O₄₀) and heteropolyacid catalysts.