Research on Chemical Intermediates最新文献

Catalysts are widely used in research and in industrial applications to enable or to accelerate chemical reactions. One application is monopropellant thrusters for space propulsion systems, which use hydrogen peroxide (H₂O₂) as liquid propellant. The decomposition of liquid hydrogen peroxide into water and oxygen gas, which then finally generates the thrust, can be achieved using noble metal catalysts like platinum and iridium. In this study, iridium–platinum alloys were deposited onto ceramic pellets by a controlled magnetron sputtering process with different parameters. Selected parameters result in coated layers featuring an atomic structure of closed- and/or open-shell microstructures. The catalytic performance of these coated pellets was evaluated in laboratory experiments. The reactivity of sputtered iridium–platinum layers for the decomposition of H₂O₂ was found to be significantly higher with respect to layers of pure iridium coatings. This can be explained by the better reactivity of iridium–platinum alloys, combined with the active control of the surface morphology and the microstructure of the alloy coatings.

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This article describes the amalgamated of polyboric acid (PBA) and Aminoethyl-3-Aminopropyltriethoxysilane (AEAPTES) by straightforward extrusion process to produce composite (PBA/AEAPTES). It showed basic nature due to amine functionalities on surface of PBA. The composite is applied for the fabrication of pyran derivatives. These reactions are noteworthy for their large product yields, environmental friendliness, quick reaction times, wide range of substrates and no need of hazardous solvents. Moreover, there is no discernible decrease in activity after four reuses of the catalyst and catalyst separated by simple filtration method without any extraction. The resultant composite is characterized by FT-IR, XRD and SEM analysis. In addition, the synthesized compounds characterized by FT-IR, ¹H, & ¹³C NMR analysis.

Here, we highlight an efficient and novel approach for the one-pot multicomponent synthesis of 2-amino-4,6-disubstituted-3-cyanopyridine derivatives through the cyclo-condensation of substituted aromatic aldehydes, ammonium acetate, malononitrile, and aryl ketones under neat conditions. The current protocol offers several key advantages, including short reaction times (approximately 0.55 hours), high yields (up to 96%), mild reaction conditions (80 °C), broad substrate scope, catalyst recyclability, and a simple isolation procedure. The reported method harnesses the catalytic potential of guanidine hydrochloride, serving as a highly effective organo-catalyst, which exhibits exceptional mildness and catalytic activity, facilitating the reaction with high yield. Furthermore, green chemistry metrics such as Eco-Scale (95), E-Factor (0.29), and Process Mass Intensity (1.60) were employed to evaluate the environmental impact of the process.

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New isatin-thiosemicarbazone (1–6) were obtained from various 5-methylisatin and various isothiocyanates with good yields and efficient methods. The structures of the synthesized compounds were clarified by FT-IR, ¹H-NMR, and ¹³C-NMR spectroscopic techniques and elemental analysis. The antioxidant activity properties of the compounds were investigated by 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging method and total reducing power determinations. In our total reducing power study, where we chose Trolox as the standard antioxidant, it was found that the reducing powers of compounds containing different substituent groups and positions were close to each other and lower than Trolox. In the study using butylated hydroxytoluene (BHT) as a reference antioxidant, DPPH antiradical scavenging capacities of the synthesized compounds were determined. The free radical scavenging effects of the synthesized compounds were compared with the IC₅₀ values obtained from the concentration equations and were found in the order BHT > 6 > 3 > 5 > 1 > 2 > 4. Structural and electronic properties of the compounds were examined by density functional theory (DFT) calculations and their relationship with the antioxidant properties of the compounds was discussed. DFT calculations played an important role in determining how the electronic properties of the synthesized compounds, especially in the presence of different substituents and in the ortho and meta positions, and accordingly the antioxidant properties of the compounds, changed. Experimental and theoretical results confirmed that methoxy-containing structures in the synthesized compounds exhibit higher antioxidant effects compared to halogen-containing structures, regardless of their position.

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In recent years, the environmental problems caused by microplastics (MPs) as novel pollutants have received widespread attention, and photocatalytic technology can degrade MPs into small molecule compounds such as aldehydes and ketones. Among the existing catalysts, graphitic phase carbon nitride (g-C₃N₄) shows great potential in degrading pollutants due to its unique properties. In this paper, the structure, preparation method, modification method, mechanism of degradation of MPs and influencing factors of g-C₃N₄ are systematically reviewed. It is summarized that ·OH, h⁺, and ·O₂⁻ are the main active species in the degradation of MPs by g-C₃N₄, and the external conditions such as pH, light intensity, and the morphology of MPs themselves can affect the degradation of MPs. However, g-C₃N₄ photocatalytic degradation of MPs is still only in the laboratory stage at this stage, and problems such as the degradation of MPs in actual water bodies have not been carried out, so how to solve the above problems is the focus of future research in the field of g-C₃N₄ photocatalytic degradation of MPs.

Hematite (α-Fe₂O₃), an n-type semiconducting material, is considered one of the most promising photoanodes for water splitting, yet exhibits unsatisfactory photoelectrochemical (PEC) activity stemming from poor conductivity and inferior charge carrier transport. Doping is an effective strategy to improve conductivity and enhance carrier transport in α-Fe₂O₃. However, there is a limit of the doping method, because some dopants will pin the Fermi level via defect complexes and aggregate carrier recombination, leading to positive shift of onset potential and depressed saturated photocurrent. Herein, a strategy based on shallow dopants locating at multiple energy levels is developed to surpass the restriction by introducing niobium (Nb) into the titanium-doped Fe₂O₃ (Ti-Fe₂O₃) through post-treatment. The resulting Nb/Ti-Fe₂O₃ composite film is confirmed to further increase the carrier concentration of Ti-Fe₂O₃ and exhibit a 625% increase in saturated water-splitting photocurrent without positively shifted photocurrent onset. This study paves a new way for further advancement of the PEC water splitting.

In this work, SAPO-11, SAPO-11-γ-Al₂O₃ and SAPO-11-ZSM-5-γ-Al₂O₃ molecular sieve supports were prepared by static hydrothermal synthesis, which SAPO-11-γ-Al₂O₃ and SAPO-11-ZSM-5-γ-Al₂O₃ supports were loaded with Co and Mo as active metal components. The hydroisomerization properties of n-hexadecane on SAPO-11, SAPO-11-γ-Al₂O₃ and SAPO-11-ZSM-5-γ-Al₂O₃ molecular sieves were investigated, as well as the effects of reaction temperature, reaction time, solid–liquid ratio and reaction pressure on the hydroisomerization properties. The results demonstrated that the SAPO-11 molecular sieves synthesized under the ratios of 1Al₂O₃:2P₂O₅:0.6TEOS:1.2DPA:55H₂O, crystallization time of 48 h, and crystallization temperature of 180 °C had high crystallinity and uniform size distribution, and the pore structure was more obvious. After loading metals onto the SAPO-11-γ-Al₂O₃ molecular sieves, the charged metals partially block the pores or pore openings of the molecular sieves, leading to a reduction in specific surface area and pore volume. As a result, some acidic sites become occupied by the metals, weakening the acidity. The results of the hydroisomerization experiments showed that the SAPO-11 molecular sieves achieved maximum isoparaffin selectivity and isoparaffin yield, reaching values of 31.26% and 28.32%, respectively, at 340 °C over a reaction time of 60 min. The selectivity and yield reached maximum of 51.02% and 43.76% at liquid–solid ratio up to 25:1. The selectivity and yield reached maximum values of 55.82% and 51.2% at an initial reaction pressure of 5 MPA. For the SAPO-11-γ-Al₂O₃ supports, the selectivity and yield the maximum values of 79.50% and 71.49% at a metal Co: Mo loading ratio of 1:3 was achieved. For the SAPO-11-ZSM-5-γ-Al₂O₃ supports, the selectivity and yield the maximum values of 55.44% and 54.05% were achieved with ZSM-5 loading of 30 wt%. These catalysts have the potential for a wide range of applications.

In an attempt to expand the utility of natural compounds in catalysis, a novel heterogeneous catalyst derived from Gum Arabic, a natural polysaccharide, was synthesized by its modification with chlorosulfuric acid and subsequent magnetization. Material characterization confirmed the successful modification and magnetization of GA. Hammet method also approved increase of acidity of gum upon functionalization with chlorosulfuric acid. According to Response Surface Methodology optimization, this catalyst exhibited high activity for the conversion of fructose to 5-hydroxymethylfurfural under mild conditions, achieving a 96% yield at 85 °C within 73 min using 30 wt% catalyst loading. The kinetic study indicated an activation energy of 89 kJ/mol. Thermodynamic parameters were determined, with enthalpy, entropy, and Gibbs free energy values of 86.11 kJ/mol, − 29.45 J/mol, and 96.65 kJ/mol, respectively. Furthermore, the catalyst displayed excellent recyclability, retaining over 87% activity for five consecutive cycles, and a heterogenous nature as confirmed by hot filtration test. This study demonstrates the potential of the as-prepared catalyst for sustainable 5-hydroxymethylfurfural production, highlighting its high activity, recyclability, and environmentally friendly nature.

Addressing the challenges posed by the high cost and limited efficiency of traditional Chinese medicine wastewater treatment, the development of a cost-effective and highly efficient catalyst for activating persulfate (PMS) to degrade organic pollutants holds significant practical importance. This research successfully synthesized a zinc-cobalt bimetallic catalyst supported on sepiolite (Zn-Co@SEP). The verification was performed using various characterization techniques, including Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), and X-ray Photoelectron Spectroscopy (XPS). XRD and SEM results both indicate that Zn-Co@SEP has excellent crystallinity, with active metal particles uniformly distributed on the surface of sepiolite nanofibers and consistent particle size. Additionally, the BET method determined the specific surface area of Zn-Co@SEP to be 5.533 m²/g. The introduction of sepiolite as a carrier provided additional active sites, facilitating the redox cycling of Co²⁺/Co³⁺ and Zn²⁺/Zn³⁺, which continuously generated reactive species. Zn-Co@SEP exhibited remarkable catalytic activity towards PMS, achieving a degradation efficiency of over 93% for TC (50 mg/L) within just 30 min in the Zn-Co@SEP/PMS system. The study systematically investigated the influence of Zn-Co@SEP dosage, PMS dosage, TC concentration, pH, and temperature on the degradation efficiency of the catalytic system. Notably, the Zn-Co@SEP/PMS system maintained high degradation rates for TC across a wide pH range (3–11) and demonstrated robust stability and recyclability, retaining a degradation rate of 89.56% after four cycles of reuse. Further experimental evidence from free radical quenching studies, electron paramagnetic resonance (EPR) experiments, and oxidative capacity potential (OCPT) results underscored the involvement of multiple radicals (¹O₂, SO₄⁻•, O₂⁻•, •OH) and electron transfer pathways in promoting TC degradation. In conclusion, this research contributes new insights into the synthesis of efficient PMS catalysts tailored for the degradation of antibiotic wastewater, addressing a critical need in environmental remediation.

The role of oxygen vacancies in enhancing photocatalytic activity has attracted increasing attention. In this work, ZnO nanorods with enriched surface oxygen vacancies were successfully synthesized via a facile hydrothermal process combined with calcination in the presence of urea, and the content of the oxygen vacancies could be tuned by adjusting the calcination temperature and time. The characterization results proved that the content of oxygen vacancies reached 45.47% with a calcination temperature and time of 500 °C and 4 h, respectively. Additionally, the increased oxygen vacancy content was conducive to not only narrowing the ZnO bandgap, but also accelerating the separation and transfer of photoproduced electron–hole pairs, thus enhancing the methylene blue (MB) removal. The maximum removal efficiency of MB reached 97.65% within 120 min under simulated sunlight irradiation, and the catalyst exhibited stable performance after five consecutive cycles. The degradation intermediates of MB determined by liquid chromatograph–mass spectrometer (LC–MS) were the aromatic and ring-opening products of demethylation, desulfurization and hydroxylation. The toxicities of these compounds decreased significantly based on the germination and growth of Vigna radiata. This study provides a controllable and simple strategy for the design of ZnO with abundant oxygen vacancies and high activity in a photocatalytic system under simulated sunlight.