Research on Chemical Intermediates最新文献

In this study, the aerobic oxidation of alkylbenzenes and alcohols in the presence of a novel kind of NiO/Al₂O₃ nanocatalyst was investigated. The NiO/Al₂O₃ nanocatalyst was synthesized by the co-precipitation procedure and it was characterized by various techniques, including XRD, FE-SEM, EDS, BET, and TGA. In the presence of the NiO/Al₂O₃ nanocatalyst, the selective aerobic oxidation of various alkylbenzenes to the corresponding ketones was carried out in water under reflux conditions. Moreover, the selective aerobic oxidation of alcohols to the corresponding aldehydes and ketones was efficiently performed under similar conditions. In both reactions, the results showed that the catalyst was recyclable for up to six consecutive runs through simple filtration.

Mesoporous silica with hierarchical macroporous architecture (MMS) was prepared by applying templating synthesis techniques and used as an advanced support of manganese-oxide catalysts. Two types of pores, i.e., mesopores and macropores, were constructed by using organic surfactant and colloidal crystal of spherical poly(methyl methacrylate) (PMMA) particles as templates, respectively. Structural stability of MMS and formation of manganese oxides on MMS were confirmed through the various characterization techniques after loading of precursor on MMS and calcination in the air. Efficient adsorption performance of rhodamine B (RhB) in water was also observed in MMS having two types of pores, which was superior to that on porous silica with only one type of pores, either mesopores or macropores. Based on the functions of advantageous structure of MMS, manganese oxides supported on MMS showed good catalytic performance in the oxidative degradation of RhB in water by using ammonium peroxodisulfate. The combined porous structure of MMS has potential in the design of composite catalyst for water purification.

A facile and effective method for the green synthesis of 2-amino-4H-benzo[h]chromene derivatives via the multicomponent reaction in the presence of magnetic mesoporous silica nanoparticles containing ZrO₂/CuO nanocomposite (M-MSN@ZrO₂/CuO) as an efficient and reusable nanocatalyst is presented. Prepared Lewis acidic nanocatalyst was characterized using various techniques such as field emission scanning electron microscope, X-ray diffraction, energy-dispersive x-ray spectroscopy, vibrating sample magnetometry, elemental mapping and Fourier transform infrared spectroscopy. Obtained catalyst was used for the green synthesis of some 2-amino-4H-benzo [h] chromene derivatives under green conditions (water as solvent and room temperature) by yield of 85–97% after short reaction times. The structure of the obtained products was confirmed using spectroscopic methods.

Graphical abstract

Novel, green, and reusable heteropoly acid-supported aluminum-exchanged Indian clay catalytic materials have been prepared and utilized for producing several tetrasubstituted imidazoles by reacting various substituted aromatic aldehydes with a primary amine, benzil, and ammonium formate in an ethanol medium. It was found that a heteropoly acid-supported aluminum-exchanged Indian clay catalyst (PWA/Al³⁺-ExIC) showed better activity compared to other catalysts tested. The reaction parameters were optimized for the product, 1,2,4,5-tetraphenyl-1H-imidazole, and the catalyst’s physicochemical properties were analyzed using XRD, SEM, TGA, BET surface area, and FTIR. The optimized reaction parameter conditions were selection of the nitrogen source, catalyst, amount of the catalyst, solvent, and time. Several substituted imidazoles were prepared in 68 to 93% yield. Additionally, the acidity of Al³⁺-ExIC and its supported clays were explored by the DRIFTS method using pyridine as a probe molecule. A reaction pathway for the substituted imidazoles was provided. The substituted imidazoles were characterized by their proton NMR spectra, FTIR, and melting points. After the reaction, the heterogeneous solid acid catalyst, PWA/Al³⁺-ExIC, can be easily retrieved. The catalyst was found to lose activity gradually in the reusability test.

In this paper, the effects of silica-alumina ratio and copper loading on the performance of Cu-SSZ-13 molecular sieve catalysts in selective catalytic reduction (SCR) reaction were investigated. The differences in NO_x conversion, N₂ selectivity, NH₃ adsorption performance, and reaction mechanism were systematically analyzed by preparing Cu-SSZ-13 catalysts with different silica-to-aluminum ratios (9, 20, and 30) and copper loadings (0.1 mol/L and 0.075 mol/L). It was found that catalysts with lower silica-to-aluminum ratio (e.g., SAR9-Cu0.1) had more Brønsted acid sites (B-acid sites), which could provide more active sites for Cu ion exchange and NH₃ adsorption, and thus exhibited higher SCR catalytic activity and N₂ selectivity. The increase in Cu loading also helps to increase the number of active sites of the catalyst, which further enhances the NO_x conversion efficiency of the catalyst. The adsorption characteristics of NH₃ on the catalyst surface, the formation and conversion process of nitrate species, and the mechanism of the effect of different Si/Al ratios and copper loadings on the catalyst performance were revealed by means of the characterization of NH₃-TPD, NH₃-TPO,XPS,XRD,BET,Pyridine infrared and in situ DRIFTS. The results show that the bridged nitrate has good thermal stability at high temperature and exhibits high activity in the reaction with NH₃. This study provides a theoretical basis for optimizing the design of Cu-SSZ-13 catalyst and its practical application in diesel exhaust treatment.

Graphic abstract

Coating Manganese oxide (MnO_x) onto solid substrates is one of the most effective approaches for addressing the inherent agglomeration tendency of powdered MnO_x in practical applications. In this study, we deposited MnO_x onto activated carbon (AC) and improved the catalytic performance for formaldehyde (HCHO) removal by introducing metal platinum (Pt). When evaluated as catalysts in the HCHO catalytic reaction at ambient temperature, the obtained 0.05 wt% Pt-MnO_x/AC catalyst possessed remarkable catalytic and adsorption activity and stability. It could achieve 98%HCHO removal by degrading 1.01 ppm HCHO to 0.02 ppm (0.024 mg/m³) within 2 h in static test at ambient temperature. Further structure-performance investigations revealed the crucial role of metal Pt, which not only improved the oxygen activation capacity but also increased the contents of adsorbed oxygen species and enriched oxygen vacancies; therefore, key intermediates, including performic acid, formate, and CO, can be easily converted. More importantly, the deactivated catalyst regained its full activity after 6 h of air exposure, which was attributed to the rapid regeneration of surface hydroxyl groups through atmospheric O₂ and the oxidation of accumulated intermediates. This study reveals the HCHO catalytic mechanism over Pt-MnO_x/AC and provides valuable insights into the design of high-activity, relatively low-cost environmental catalysts.

Graphical abstract

Owing to their distinctive and tunable physicochemical properties, zinc oxide (ZnO) nanoparticles (NPs) have attracted significant attention in cancer therapy as well as photocatalytic applications. The novelty in this work was to use a green approach using pomegranate peel extract to synthesize pure ZnO NPs, Al-doped ZnO NPs, and Al-ZnO/rGO NCs to improve their photocatalytic and anticancer performance. The synthesized materials were characterized in detail by XRD, SEM, EDX, XPS, FTIR, PL, and DLS. XRD results confirmed the high crystallinity of ZnO and indicated increased crystallite size from 17.60 nm to 21.51 nm by doping and rGO incorporation. The SEM image of ZnO NPs showed spherical shapes with uniform distribution on the surface of rGO. EDX verified the existence of Zn, O, Al, and C in the nanocomposites without observable impurities, whereas XPS revealed the elemental composition and oxidation states. FTIR also supported the presence of functional groups, and UV–Vis results showed a decrease in the bandgap energy from 3.34 eV to 3.25 eV due to doping as well as rGO integration. Based on the PL data, it was supposed that better charge separation and improved photocatalytic reaction and biomedical application potential were discerned from these composites. DLS results showed that the zeta potential of pure ZnO NPs, Al-doped ZnO NPs, and Al-ZnO/rGO NCs were − 16.3 ± 8.30 mV, − 20.2 ± 6.86 mV, and 21.0 ± 14.10 mV, respectively. In a photocatalytic experiment, Al-ZnO/rGO nanocomposite showed enhanced degradation efficiency (82.49%) for Brilliant Blue R dye compared to pure ZnO (59.70%). Cytotoxicity evaluations against colorectal cancer (HCT116) cells showed markedly superior anticancer efficacy of Al-ZnO/rGO nanocomposites after both 24 and 48 h, higher than that of pure ZnO and Al-doped ZnO nanoparticles. The findings highlight the combined effect of aluminum doping and reduced graphene oxide incorporation to enhance the photocatalytic and anticancer efficacy of zinc oxide-based nanomaterials.

Vanadium complexes are efficacious catalysts for the oxidation of diverse organic substrates. Immobilizing these complexes on solid supports enhances their chemical and thermal stability, improves catalytic efficiency, and facilitates easy separation from the reaction mixture, thereby minimizing contamination of the final product. A novel vanadium complex of substituted benzimidazole, 2(2'-quinolylbenzimodazole) immobilized on a partially chloromethylated polystyrene cross linked with divinyl benzene copolymer support was synthesized successfully. The supported catalyst was characterized by elemental analyses, TGA, conductivity and magnetic susceptibility measurements, FT-IR and Diffused Reflectance and Electron Spin Resonance spectral analysis. The proposed catalyst revealed positive outcomes in the oxidation reactions of Phenol, p-Nitrophenol, p-Cresol, Benzyl alcohol and p-Chlorobenzyl alcohol in water under ambient reaction conditions with H₂O₂ as an oxidant. The catalyst under ideal concentration and ambient reaction conditions exhibited excellent activity towards the green oxidation of Phenol with 99% conversion with 96% selectivity toward catechol at 60 °C. Similarly, p-nitrophenol exhibited a 95% conversion with 86% selectivity toward p-nitrocatechol. Additionally, the oxidation of p-cresol resulted in a 99% conversion and 92% selectivity toward p-hydroxybenzaldehyde. The catalyst also displayed excellent recyclability and facile separation, underscoring its potential for sustainable oxidation processes. It could be recycled for five turns retaining the catalytic activity of 92 to 94% with negligible leaching of only 0.25% of the embedded metal. The results suggested immobilized vanadium complex as an environmentally benign catalytic system to oxidize phenolic compounds in water.

In this study, a straightforward and eco-friendly approach was developed for the synthesis of biocompatible compounds that include manganese and tannic acid covalently linked with β-cyclodextrin (Mn/TA-βCD and MnTA/βCD). Additionally, a MnO₂/TA-βCD composite was prepared for comparison. FT-IR, UV–vis, TGA, and Fluorescence techniques were used to characterize the prepared samples. TGA analysis demonstrated that MnTA/βCD had better thermal stability than Mn/TA-βCD. An interaction between β-cyclodextrin and tannic acid was confirmed by the fluorescence spectrum. The introduction of tannic acid into the β-cyclodextrin further improved the in vitro antioxidant potential. According to the pyrogallol autoxidation, MnTA/βCD exhibited the highest SOD-like activity (93%), and MnO₂/TA-βCD demonstrated superior efficacy in scavenging hydrogen peroxide (94%). In addition, MTT assay studies confirmed the non-cytotoxic nature of the compounds.

The performance of graphitic carbon nitride (g-C₃N₄)-based cobalt (Co) catalysts (Co-g-C₃N₄, Co@g-C₃N₄) for the hydroesterification of diisobutylene (DIB) was evaluated. In this study, graphite carbon nitride (g-C₃N₄) was synthesized by that thermal decomposition of urea, melamine and thiourea in a muffle furnace. The results showed that the optimal reaction conditions were CO pressure 8.0 MPa, reaction temperature 150 °C and reaction time 10 h. When Co₂(CO)₈-g-C₃N₄ in situ catalyst was used, the conversion of DIB was 94.6% and the selectivity to methyl isononanoate was 90.0%. Similarly, in order to solve the problem of poor reusability of the catalyst, Co(OAc)₂@g-C₃N₄ catalyst system prepared by impregnation method was studied. Under the same reaction conditions for 12 h, only 72.0% conversion of DIB and 89.6% selectivity to methyl isononanoate were obtained, but the catalytic performance was obviously improved compared with in situ catalyst. The catalysts were characterized by scanning electron microscope (SEM), Fourier transform infrared spectrometer (FT-IR), N₂ adsorption–desorption isotherm and so on. In addition, the two catalyst systems are suitable for the hydroesterification reaction of various terminal olefins, and exhibit excellent recovery performance and thermal stability.

Graphical abstract