Research on Chemical Intermediates最新文献

This study depicts the application of fulvic acid (FA) as a biodegradable, reproducible, and efficient catalyst for the synthesis of tetrahydropyrimidine-5-carboxamides (4a–4j) via a one-pot three-component reaction of urea, aldehydes, and 3-oxo-N-(5-phenyl-1,3,4-thiadiazol-2-yl)butanamide, as well as the synthesis of benzo-chromeno-pyrimidin-amines (8a–8l) using a one-pot pseudo-five-component reaction of 1-naphthol, aldehydes, malononitrile and ammonium acetate at mild temperatures in aqueous medium. Green reaction environment, operational simplicity, low catalyst usage (0.02–0.04 g), superb yields (90–98%), short reaction times (15–33 min), presentation of novel derivatives to the literature, and the possibility of easy recovery of the catalyst from the reaction mixture for up to six runs without significant loss in catalytic activity are the salient aspects of the above synthetic routes.

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The efficient and comparative synthesis of bis-enol derivatives using WEPAPA and WEPPA bio-waste catalysts has been reported in the present study. The catalysts were considered to be economical, recyclable and sustainable. During optimum studies, the percentage yield of the product was above 85% in both the cases. However, in the case of WEPPA catalyst, there was a marginal decrease of 4% in the yield. The reaction was susceptible for the formation of a number of derivatives. The products obtained were removed from reaction mixture using simple filtration technique and did not require any column chromatographic techniques for purification. The products obtained were recrystallized using hot ethanol. The products were identified by the use of ¹H and ¹³C NMR spectroscopic techniques. Both the catalysts were recyclable up to four times maintaining their catalytic efficiency throughout the cycles.

InGaN is a promising photocatalytic material with excellent and tunable optical properties. However, the effect of modifying InGaN thin films with various modifier layers on photocatalytic CO₂ reduction remains underexplored. In this work, we systematically investigated the impact of g-C₃N₄, TiO₂, and their bilayer combination on the photocatalytic performance of InGaN photoanodes. The simultaneous loading of g-C₃N₄ and TiO₂ onto InGaN yielded the most significant enhancement. This configuration resulted in a CO₂-to-CO conversion rate of 4.725 µmol·mol⁻¹, which is 2.35 times higher than that of bare InGaN (2.006 µmol·mol⁻¹). Furthermore, the production of H₂ and hydrocarbons was also augmented. Electrochemical and spectroscopic analyses revealed that the bilayer structure synergistically combines the high light-harvesting capability of TiO₂ with the improved CO₂ reduction selectivity of g-C₃N₄, while also mitigating photocorrosion. This work demonstrates that constructing hybrid modifier layers is an effective strategy for boosting the activity and stability of InGaN-based photocatalysts for CO₂ reduction.

Hydrogen is considered a future fuel. However, mostly hydrogen is generated with other gases such as CO, CO₂, N_2, etc. Therefore, the separation of hydrogen from these gases is vital. Palladium-based membranes are commonly used for hydrogen separation. However, preparing a defect-free membrane on porous substrate is still a major challenge. This study highlights the development of appropriate intermediary layers to facilitate uniform palladium deposition on commercially available alumina substrates. CeO₂-YSZ intermediate layers are used on a porous alumina tube before depositing the palladium layer. YSZ and CeO₂ layers are deposited through the vacuum-assisted dip-coating method, and the palladium layer is deposited on the intermediate CeO₂-YSZ layers using the electroless pore plating (ELP-PP) method. The single solution of the Pd is used to prepare the membrane by optimizing the solution's N₂H₄ (0.1 M–0.5 M) concentration. SEM and EDS analyses are carried out to investigate the membrane surface morphology and pore size distribution, focusing on understanding the intermediate layer's effect. The permeation property of the membrane is tested at different temperatures (300–400 ℃) and pressure ranges (0.5–3.0 bar). The membrane testing is performed with pure hydrogen and hydrogen and nitrogen mixture of different compositions. At 400 °C, the membrane permeability was 3.3 × 10^–6 mol s⁻¹ m⁻² Pa⁻¹ at 1 bar, which is one of the highest reported values compared with the literature. The nitrogen is retained completely, ensuring the hydrogen's high purity.

Cubic nickel oxide (NiO) embedded with graphitic carbon nitride (g-C₃N₄) nanocomposite, NiO@g-C₃N₄, serves an effective photocatalyst to the degradation of synthetic blue food dye, Indigo Carmine (IC). The nanocomposite was prepared using a facile thermal polymerization technique followed by an annealing procedure. The as-synthesized nanocomposite’s structures and morphologies were characterized using different techniques. The efficiency of degradation and reaction kinetics were evaluated using UV–visible spectroscopy under sunlight exposure. The catalyst’s degradation rate for IC dye was approximately 99.34% achieved in 19 min under an optimal reaction conditions. The degradation rate was followed a pseudo-first order kinetics of rate constant, k₁ = 196.6 × 10^–3. Other factors such as catalyst dosage, pH of the medium and degradation in tap water were also performed where the efficiency of NiO@g-C₃N₄ have been significantly influenced during the photodegradation process. The impact of coexisting anions and cations on the photodegradation efficiency of NiO@C₃N₄ was additionally evaluated. Trapping agents are introduced to identify the reactive species, and results showed that the super oxide (O₂^.−) radicals are the main reactive species, whereas ^.OH, electrons, and h⁺ holes had a lesser impact on the degradation process. The degradation efficiency of the catalyst in tap water reaches up to 86%. The stability of the nanocomposite was examined through three consecutive catalytic cycles, demonstrating the robustness of the catalyst.

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.

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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.

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