Research on Chemical Intermediates最新文献

A magnetic nanocatalyst, Fe₃O₄@SiO₂@GLYMO@Melamine nanoparticles immobilized with zinc, was synthesized (Fe₃O₄@SiO₂@GLYMO@Mel-Zn^II). The structure of the catalyst was characterized and confirmed using various analytical techniques, including FT-IR, FE-SEM, EDX, and VSM. The catalytic efficiency of Fe₃O₄@SiO₂@GLYMO@Mel-Zn^II was demonstrated in the one-pot, three-component synthesis of a range of hexahydro-1H-xanthene-1,8(2H)-dione and 12-aryl/heteroaryl-8,9,10,12-tetrahydrobenzo[a]xanthen-11-one derivatives under solvent-free conditions at 100 °C. This method offers several key advantages, such as high product yields, short reaction times, simple work-up, catalyst reusability, environmentally benign conditions, the elimination of solvents, and the non-toxic nature of zinc as a metal center. Remarkably, the catalyst retained its activity over five consecutive cycles.

This study employs density functional theory (DFT) calculations to investigate the reaction mechanism of methanol steam reforming (MSR) on pristine and palladium-doped copper (111) surfaces. The results demonstrate that Pd doping significantly reduces energy barriers for key steps in the MSR reaction, thereby enhancing overall reaction kinetics. Electronic structure analysis reveals that Pd doping broadens the d-band density of states of Cu and shifts it closer to the Fermi level, which likely contributes to improved catalytic activity. Notably, water dissociation, a critical step in the MSR process, exhibits a lower energy barrier on the palladium-doped catalyst. The adsorption and dissociation of key intermediates, including CH₃OH, CH₃O, HCHO, and HCOO, were also examined. The findings highlight the role of water in facilitating methanol dissociation and hydrogen gas production. Overall, this study suggests that Pd-doped Cu catalysts are promising candidates for efficient and selective methanol steam reforming.

One of the main goals of nanotechnology is the development of visible-light-active, sustainable, and non-toxic nanostructured photocatalysts; this emphasizes the necessity of eco-friendly synthesis techniques. This study presents a simple and low-temperature biosynthesis route for producing Cu₂O nanoparticles (NPs) from leaf extract and mangrove species (Avicennia marina). The biosynthesized Cu₂O nanocatalyst, optimized at an extract content of 0.5 g·100 mL⁻¹, displayed a band gap energy of 2.1 eV and an average particle size of approximately 40 nm. In this process, 3-pyridinemethanol was photocatalytically oxidized using the Cu₂O nanocatalyst to produce vitamin B₃ (nicotinic acid), achieving an impressive 99% yield. Under visible light irradiation, Cu₂O generates electron–hole pairs that drive redox reactions. The presence of alcohol-based hole scavengers minimizes charge carrier recombination, thereby enhancing photocatalytic efficiency. This approach offers a green, energy-efficient alternative for vitamin synthesis, aligning with the principles of sustainable chemistry. The results demonstrate the potential of biologically derived nanomaterials for eco-friendly organic synthesis and open avenues for future research into sustainable production of value-added compounds.

N-cyclohexylcyclohexanimine (N-CCA), a by-product of cyclohexylamine (CHA) oxidation to cyclohexanone oxime (CHO), was used as the starting reactant for the efficient conversion to CHO under an oxygen atmosphere, utilizing the constructed surface hydroxyl-rich Ti-based catalysts. Of these, the 20% TiO₂/Hβ catalyst exhibited unique catalytic activity and stability, achieving 45.9% N-CCA conversion and 82.1% CHO selectivity, with the content of high-boiling by-products not exceeding 1.0%. The superior catalytic performance, as evidenced by characterization results, stems primarily from: (i) the combination of TiO₂ and Hβ, which promotes the formation of a high specific surface area with fine TiO₂ nanoparticles and high-density Ti^δ+ active sites, which facilitate the adsorption and activation of N-CCA; (ii) the construction of rich hydroxyl groups, which enhances the Brønsted acid sites, thereby improving the generation of active oxygen species; (iii) the intercrystalline embedding of TiO₂ and Hβ, which forms Ti–O–Si bonds, effectively inhibiting Ti leaching and ensuring excellent catalyst stability. The conversion of N-CCA, the main by-product of CHA oxidation, to the desired CHO using an efficient and robust 20% TiO₂/Hβ catalyst represents an attractive pathway.

In this research, the preparation of new benzochromene derivatives was synthesized in a three-component reaction using 1-naphthol and 2-naphthol, methylsulfonylacetonitrile and malononitrile, and aldehyde derivatives in the presence of triethylamine as catalyst, 2-hydroxyethylammonium formate as ionic liquid catalyst, and Fe₃O₄@SiO₂@[O-(CH₂)₂-NH₂][HCO₂H] as nanocatalyst. The advantages of this protocol include high yields, green chemistry, short reaction times, and catalyst recycling.

In the present work, Cu_0.72Co_2.28O₄–CuO/HMS nanocomposite was efficiently synthesized by a novel, facile, simple and eco-friendly impregnation method followed by calcination at 550 °C. The Fourier transform infrared spectroscopy and X-ray diffraction results established the formation of the nanocomposite Cu_0.72Co_2.28O₄–CuO/HMS. The catalytic reduction of 4-NP to 4-AP in the presence of excess NaBH₄ as a reducing agent in aqueous media, was selected as a reaction model to evaluate the catalytic activity of Cu_0.72Co_2.28O₄–CuO/HMS nanocomposite in the ambient. The Cu_0.72Co_2.28O₄–CuO/HMS material exhibited robust catalytic activity in 4-NP reduction with a rate constant of (2.04 times {10}^{-2}{text{ s}}^{-1}). A 4-NP conversion percentage which is of 100% was achieved within 90 s on the nanocomposite. The kinetic analysis confirmed the Langmuir–Hinshelwood model for the Cu_0.72Co_2.28O₄–CuO/HMS material catalyzed 4-NP reduction.

The SAPO-34 molecular sieves were synthesized via a hydrothermal method using tetraethylammonium hydroxide and triethylamine as dual templates, with myristyl sulfobetaine (SB3-14) as a crystal growth inhibitor. The synthesized samples were systematically characterized by XRD, SEM, ICP, N₂ adsorption–desorption, NH₃-TPD, pyridine-adsorption IR, and FT-IR techniques to analyze their composition, acidity, and structural properties. Results demonstrated that increasing the molar ratio of SB3-14 to Al₂O₃ from 0.01 to 0.04 caused significant variations in morphology, chemical composition, and acidic characteristics of the samples. When the molar ratio of SB3-14 to Al₂O₃ was 0.02, the synthesized sample NS-0.02 exhibited the smallest crystal size, the largest specific surface area, and moderately reduced acidity. The catalytic performance was evaluated in the MTO reaction. The NS-0.02 sample exhibited superior catalytic performance with 94.5% selectivity to light olefins and a catalytic lifetime of 600 min.

The development of methodologies that are both sustainable and efficient remains one of the most important goals in contemporary chemical synthesis. This study focuses on the synthesis of 2-amino-7-hydroxy-4-aryl-4H-chromene-3-carbonitrile derivatives, which are biologically and pharmaceutically significant compounds, using a green and highly efficient approach. The reaction takes place in the absence of solvents, employing a magnetically separable Fe₃O₄@SiO₂@CeO₂ nanocatalyst, which is more ecological. This method has a number of advantages, including high yields of the desired products, fast reaction time, and easy separation and reuse of the catalysts. In addition to these benefits, the method tolerates an extensive scope of substrates, allowing condensation of various benzaldehydes, malononitrile and resorcinol derivatives in one reaction vessel. The outcome demonstrates the efficiency of magnetically separable nanocatalyst in performing organic reactions under environmentally friendly conditions, thus fostering the development of green chemistry.

Graphical Abstract

With the increasing environmental impact of organic dyes in water, a novel zinc-based metal–organic framework (MOF), [Zn(bdc)(bpb)]_n (referred to as 1), was presented in this study, and its photocatalytic degradation performance of organic dyes was investigated. The MOF exhibits excellent photocatalytic activity for the degradation of rhodamine B (Rh B) and methyl orange (MO) under visible light, achieving degradation efficiencies of 94.3% and 96.3% within 45 min, respectively. Additionally, MOF 1 demonstrated remarkable reusability, maintaining high degradation efficiency (> 82%) after three cycles. Mechanistic studies revealed the synergistic role of superoxide radicals, hydroxyl radicals, and photogenerated holes in the photocatalytic process. These findings highlight the potential of 1 as an efficient and sustainable photocatalyst for wastewater treatment.

The potential of TiO₂-modified bentonite as a cost-effective support for nickel-based catalysts in the dry reforming of methane (DRM) is highlighted. The comparison of a nickel catalyst supported on natural bentonite and one prepared on TiO₂-modified bentonite revealed a significantly different behavior between the two catalysts under diluted and concentrated DRM reaction conditions. The unmodified bentonite catalyst, 15Ni/Na-Bent, exhibits high activity under diluted conditions (20CH₄:20CO₂:60He) but deactivates quickly under concentrated DRM conditions (40CH₄:40CO₂:20He). On the other hand, 15Ni/TiO₂-Bent is less active at diluted conditions but demonstrates superior stability and activity in concentrated conditions. In situ XPS analysis of the O 1s, Al 2p, Si 2p, and Ti 2p regions of the calcined, reduced, and post-DRM samples revealed that TiO₂ stabilizes the clay structure and prevents nickel reoxidation. The formation of TiO_2-x species after reduction creates oxygen vacancies that trap oxidizing species in the reaction medium, thus limiting nickel reoxidation and reducing carbon deposition on the surface. Moreover, these TiO_2-x species migrate to the nickel surface, forming a thin protective layer that partially encapsulates the nickel, improving metal–support interactions and providing resistance against sintering and reoxidation. In addition to XPS spectroscopy, which provided insights into the nature of the metal–support interactions in the 15Ni/Na-Bent and 15Ni/TiO₂-Bent catalysts, the materials were also characterized using XRF, XRD, SEM, BET, TPR-H₂, and Raman spectroscopy. These techniques offered complementary structural, textural, and morphological information, leading to a more comprehensive understanding of the catalysts’ physicochemical properties.