Efficient and reusable ordered mesoporous WOx/SnO2 catalyst for oxidative desulfurization of dibenzothiophene

Robust interaction of ZnO and TiO2 nanoparticles with layered graphitic carbon nitride for enhanced photocatalytic oxidative desulfurization of fuel oil: mechanism, performance and stability

Sulfur compounds in fuel such as thiophene, benzothiophene and dibenzothiophene are the primary source of SO x emissions, leading to environmental pollution and acid rain. In this study, we synthesized a layered oxygen-doped graphitic carbon nitride (OCN) structure and integrated ZnO and TiO2 nanoparticles onto the OCN surface through a microwave-assisted sol-gel method. The X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) results confirmed a robust interaction between the ZnO and TiO2 nanoparticles and the oxygen-doped g-C3N4 (OCN) surface, as indicated by the formation of C-N-Ti and C-O-Ti bonds. This interaction notably improved the optoelectronic properties of the ZnO-TiO2/OCN composite, yielding increased visible light absorption, reduced charge recombination rate, and enhanced separation and transfer of photogenerated electron-hole pairs. The oxygen doping into the CN network could alter the band structure and expand the absorption range of visible light. The ZnO-TiO2/OCN photocatalyst demonstrated remarkable desulfurization capabilities, converting 99.19% of dibenzothiophene (DBT) to dibenzothiophene sulfone (DBT-O2) at 25 °C, and eliminating 92.13% of DBT from real-world fuel oil samples. We conducted in-depth analysis of the factors impacting the redox process of DBT, including the ZnO ratio, initial DBT concentration, catalyst dosage, stability, and O/S molar ratio. Radical trapping experiments established that ˙O2 -, ˙OH and h+ radicals significantly influence the reaction rate. The obtained results indicated that the ZnO-TiO2/OCN photocatalyst represents a promising tool for future fuel oil desulfurization applications.

Supported copper on a diamide-diacid-bridged PMO: an efficient hybrid catalyst for the cascade oxidation of benzyl alcohols/Knoevenagel condensation

In this study, a novel periodic mesoporous organosilica (PMO) containing diamide-diacid bridges was conveniently prepared using ethylenediaminetetraacetic dianhydride to support Cu(ii) species and affording supramolecular Cu@EDTAD-PMO nanoparticles efficiently. Fourier transform infrared (FT-IR) and energy dispersive X-ray (EDX) spectroscopy, thermogravimetric analysis (TGA), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Brunauer-Emmett-Teller (BET) analysis, and high-resolution transmission electron microscopy (HRTEM) results confirmed the successful synthesis of Cu@EDTAD-PMO. The stabilized Cu(ii) nanoparticles inside the mesochannels of the new PMO provided appropriate sites for selective oxidation of different benzyl alcohol derivatives to their corresponding benzaldehydes and subsequent Knoevenagel condensation with malononitrile. Therefore, Cu@EDTAD-PMO can be considered as a multifunctional heterogeneous catalyst, which is prepared easily through a green procedure and demonstrates appropriate stability with almost no leaching of the Cu(ii) nanoparticles into the reaction medium, and easy recovery through simple filtration. The recycled Cu@EDTAD-PMO was reused up to five times without significant loss of its catalytic activity. The stability, recoverability, and reusability of the designed heterogeneous catalyst were also studied under various reaction conditions.