Research on Chemical Intermediates最新文献

A mild and robust synthetic strategy has been developed for the synthesis of 1,3-thiazolidin-4-one derivatives via a one-pot, three-component reaction of aromatic or heteroaromatic aldehydes, aromatic amines, and thioglycolic acid under solvent-free conditions at 110 °C. The reaction proceeds efficiently in the presence of iron oxide nanoparticles coated with hydroxyapatite (Fe₃O₄/HAP), serving as a heterogeneous solid-base nanocatalyst. This nanocatalyst produces good to excellent yields desired product and offers several practical advantages. Comprehensive characterization of the catalyst was performed using X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and field emission scanning electron microscopy. The new synthetic methodology has a shorter reaction time, a broad-substrate scope, and an eco-friendly and solvent-free approach. Due to its strong magnetic responsiveness, the catalyst can be conveniently recovered using an external magnetic field and reused for five successive cycles with negligible loss in activity.

Graphical abstract

A metal-free P-(g-C₃N₄/NCDs) photocatalytic composite was synthesized by modifying graphitic carbon nitride (g-C₃N₄) through a dual strategy of nitrogen-doped carbon quantum dots (NCDs) incorporation and protonation. Under light irradiation, the optimized catalyst achieved 99% degradation of methyl orange within 120 min, exhibiting a reaction rate 50 times higher than that of unmodified g-C₃N₄. Furthermore, the composite demonstrated excellent stability, maintaining high catalytic performance over five consecutive cycles. Characterization results revealed that the dual modification induced a stripping effect on the g-C₃N₄ material. This process optimized the electronic structure of the composite, effectively suppressing the recombination of photogenerated electron–hole pairs. Additionally, adjustment of the band gap structure enhanced the oxidizing capacity of the valence band, thereby improving the overall photocatalytic activity. The synergistic effect of superoxide (•O₂⁻) and hydroxyl (•OH) radicals in substantially boosting the oxidative capacity of P-(g-C₃N₄/NCDs) was unambiguously verified by radical trapping experiments and electron paramagnetic resonance (EPR) spectroscopy. This synergy facilitates the mineralization of organic dye molecules into small inorganic molecules (e.g., CO₂ and H₂O). This metal-free photocatalyst design strategy, focused on material structure optimization, circumvents secondary water pollution from metal leaching, suggesting promising potential for applications in green catalysis and related fields.

New bimetallic Pd–Mn catalysts supported on the carbon material Sibunit have been obtained and studied for the process of producing ethylene by acetylene hydrogenation. The composition, structure, morphology and electronic state of the active phase have been studied in detail depending on the temperature of treatment in hydrogen and the Pd/Mn ratio by XRD, XANES, EXAFS, TEM, XPS. It has been found that the active species are the nanoparticles of intermetallic tetragonal structure Pd₃Mn₂ that formed during the treatment of Pd–Mn/Sibunit in H₂ at 500 °C. Increasing the reduction temperature to 600–700 °C provides an increase in the proportion of the Pd₃Mn₂ phase due to more complete involvement of palladium in the interaction with manganese. Pd₃Mn₂ nanoparticles are less active but more selective than Pd nanoparticles due to changes in the geometry of active sites and their electronic state. It is shown that catalysts containing a twofold molar excess of Mn relative to Pd are characterized by the presence of more dispersed bimetallic particles than samples containing less manganese, due to which they are characterized by higher activity. Pd–Mn/Sibunit catalysts provide a high ethylene yield (up to 75%), which makes them promising materials for the process of acetylene hydrogenation to ethylene.

Graphical abstract

Methylene blue (MB) as a persistent dye poses serious environmental threats, requiring efficient removal methods. In this study, the TiO₂-graphene nanocomposites have been fabricated for MB decomposition under visible-light irradiation. Graphene oxide was synthesized via a modified Hummers method and subsequently incorporated into mixed-phase TiO₂ (44% anatase and 56% rutile) in varying amounts (5–75 wt. %) using a hydrothermal method. The introduction of this oxygen-functionalized reduced graphene oxide (RGO) into the TiO₂ matrix significantly enhanced the photocatalytic activity by increasing the adsorption surface area, reducing the band gap, and suppressing electron–hole recombination.

The nanocomposite with an optimal 50 wt. % RGO content demonstrated nearly complete MB degradation in less than 10 min, fitting a pseudo-first-order kinetic model with a high-rate constant. These results highlight the potential of TiO₂–RGO nanocomposites for effective and rapid dye removal, presenting a promising advance in environmental remediation technologies.

Liquid-phase selective oxidation of benzyl alcohol (BZA) by atmospheric O₂ is a sustainable route for the synthesis of benzaldehyde (BZL). Although noble metal catalysts showed excellent activity, the high cost and limited reserves of noble metals underscore the significance of developing efficient non-noble metal-based catalysts. Herein, cerium vanadate (CeVO₄) materials were synthesized by a simple coprecipitation method and employed as heterogeneous catalysts for the selective oxidation of BZA by O₂. Under the same reaction conditions, the CeVO₄ materials demonstrated superior activity to the pure V₂O₅ and CeO₂ samples, affording a high yield of BZL of 69% under a reaction temperature of 120 °C. For the CeVO₄ materials, the catalytic activity correlated well with the percentages of Ce³⁺ and V⁴⁺ species, depending on the preparation temperatures. Moreover, the catalysts could be reused at least five times without significant loss in activity.

Graphical abstract

In the NH₃ selective catalytic oxidation (NH₃-SCO) reaction, non-noble metal catalysts have attracted much attention due to their low cost and high N₂ selectivity at low temperatures. However, the significant decrease in N₂ selectivity at high temperatures remains a significant challenge. In this work, we treated TiO₂ support with sulfuric acid to balance redox performance and surface acidity, thereby improving the N₂ selectivity of Cu–Ce/TiO₂ catalyst. Compared to Cu–Ce/TiO₂ catalyst, (Cu–Ce/TiO₂)-S_0.05 catalyst (sulfuric acid added during Cu and Ce co-impregnation, where the molar ratio of S to Ti is 0.05) showed a 20.8% increase in N₂ selectivity at 400 °C. After treating TiO₂ with an excessive amount of sulfuric acid, its catalytic activity significantly decreased. This was attributed to the excessive sulfuric acid treatment resulting in the aggregation of Cu species, thereby decreasing the number of redox sites on the catalyst surface and severely disrupting the balance between redox and acid properties. In situ DRIFTS results showed that, in the NH₃-SCO reaction, Cu–Ce/TiO₂ and (Cu–Ce/TiO₂)-S_0.05 catalysts followed dual pathways involving internal selective catalytic reduction and amide (–NH) mechanisms. However, after sulfuric acid treatment, the number of acid sites on the catalyst surface increased significantly, and abundant NH₃ species on the surface could effectively reduce NO_x to N₂ and H₂O through the i-SCR mechanism.

A Fe/Cr/Cu catalyst pellet was developed for the high-temperature water–gas shift reaction (HT-WGSR) to enable efficient hydrogen production from syngas derived from waste plastic gasification. The Fe/Cr/Cu catalyst powder was synthesized via a co-precipitation method and subsequently formed into pellets through compression molding. HT-WGSR performance was evaluated at CO:H₂O feed ratios of 1:2–1:4 and operating temperatures of 300–400 °C under a gas hourly space velocity of 10,000 h⁻¹. The highest CO conversion (84–91%) was obtained at 350 °C with a CO:H₂O ratio of 1:2, while the maximum H₂ selectivity (0.44–0.90) was achieved at 350 °C with a CO:H₂O ratio of 1:3. These results highlight the Fe/Cr/Cu catalyst pellets as promising candidates for sustainable hydrogen production in HT-WGSR applications.

Compared to other reactive oxygen species, singlet oxygen (¹O₂) exhibits unique advantages, including high selectivity and strong oxidative capacity, for the targeted oxidation of pollutants. However, its production is often limited by the narrow spectral response and low intersystem crossing efficiency of conventional photocatalysts. In this study, we constructed a composite photocatalytic system based on metal–organic frameworks (MOFs) loaded with gold nanoparticles (Au NPs) to elucidate the enhancement mechanism by which singlet oxygen generation is enhanced through synergistic modulation of localized surface plasmon resonance (LSPR) and excitonic states. The introduction of Au NPs significantly enhanced the LSPR absorption of the material, effectively promoting the conversion of excitons from singlet-to-triplet states. This was achieved by lowering the energy barrier for singlet-to-triplet conversion (Δ_EST decreased from 0.172 eV to 0.162 eV), thereby accelerating the intersystem crossing process and improving ¹O₂ generation efficiency, consequently, the system enabled efficient removal of p-chlorophenol. This work proposes a novel “LSPR–exciton regulation–photothermal synergy” mechanism, offering new strategies for the rational design of high-activity photosensitizers and targeted pollutant oxidation.

In photocatalytic degradation of pollutants, hydrogen-related defects on the catalyst surface inhibit the generation of highly reactive superoxide radicals (·O₂⁻). Therefore, strategies to mitigate such defects are crucial for enhancing photocatalytic efficiency. To address this challenge, ZnWO₄/hydrothermal red phosphorus (ZnWO₄/HRP) S-scheme heterojunction photocatalysts were successfully prepared via a simple hydrothermal method, constructing a compact interfacial structure where rod-shaped ZnWO₄ uniformly attaches to the HRP surface. Photocatalytic performance tests revealed that the composites exhibited excellent catalytic activity for rhodamine B (RhB) degradation, with a rate constant of 0.21 min⁻¹ within 15 min-3.5 and 21 times higher than those of individual HRP and ZnWO₄, respectively. Moreover, due to the robust chemical structure and strong interfacial bonding between ZnWO₄ and HRP, the composite maintains high photocatalytic stability across multiple catalytic cycles. Mechanistic analysis demonstrates that the S-scheme heterojunction effectively suppresses the formation of hydrogen-related defects on the ZnWO₄ surface, significantly reducing surface defect state density. This inhibition enhances photogenerated carrier separation, accelerates charge transfer, and facilitates the efficient generation of ·O₂⁻. By adopting a heterojunction strategy to address hydrogen-related defects, the catalyst’s visible-light absorption capacity, photoelectric conversion efficiency, and radical generation efficiency was enhanced, while carrier recombination was suppressed. These findings provide new insights for designing high-efficiency heterojunction photocatalysts and highlight their promising potential in photocatalytic removal of organic pollutants.

Graphical abstract

This research focuses on the synthesis of NiO nanoparticles via a bio-fabrication method, where almond peel extract serves as both a stabilizing and capping agent. The effectiveness of these nanoparticles in the photocatalytic treatment of the organic pollutant was comprehensively evaluated, considering various influencing factors, including organic pollutant concentration, catalyst dosage, and pH. The structural, optical, morphological, and functional groups of the fabricated materials were examined by employing XRD, UV, SEM, and FTIR techniques. The fabricated nanoparticles exhibited an average crystallite size of 20.98 nm. The degradation potential of the fabricated materials was found to be decreased with increasing the initial pollutant concentration, while it improved with a higher catalyst dosage and increasing the solution pH during the photocatalysis. NiO nanoparticles demonstrated the greatest photocatalytic removal of brilliant green and amoxicillin after 120 min solar light exposure, reaching degradation efficiency of 79.13% and 43.05% for brilliant green and amoxicillin, respectively. The removal of amoxicillin follows pseudo-first-order kinetics with an R² value of 0.89882, while the breakdown of the brilliant green follows a first-order reaction with an R² value of 0.96426. This eco-friendly synthesis procedure reduces the environmental impact associated with the conventional chemical process by harnessing the renewable resources of almond peel, offering a sustainable combat against environmental degradation.