Catalysis Letters最新文献

In this study, CuZnAl layered double hydroxide (LDH) adsorbents were synthesized via a facile co-precipitation method and evaluated for the removal of methyl orange (MO), a model anionic azo dye. Comprehensive characterization using XRD, FTIR, BET, and SEM confirmed the successful formation of phase-pure carbonate-type LDHs with ordered layer stacking, mesoporous texture, and plate-like morphology. Among the samples tested, CuZnAl exhibited the highest BET surface area (45 m² g⁻¹) and the largest total pore volume (0.432 cm³ g⁻¹), facilitating superior adsorption performance. Batch experiments revealed that all adsorbents achieved maximum removal at acidic pH, with CuZnAl reaching ≈ 100% MO removal at pH 3. Adsorption kinetics followed the pseudo-second-order model (R² > 0.99), indicating that chemisorption and interlayer ion exchange were the dominant mechanisms. The Langmuir isotherm model provided excellent fits (R² > 0.96), with the highest maximum monolayer adsorption capacity (qₘ) observed for CuZnAl (392.2 mg g⁻¹), followed by CuAl (293.3 mg g⁻¹) and ZnAl (235.3 mg g⁻¹). Reusability studies demonstrated robust cycling performance for CuZnAl, which retained ≈ 95% of its initial removal capacity after five cycles, whereas ZnAl suffered the greatest decline.

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Ammonia Selective Catalytic Reduction (NH₃-SCR) is highly effective for nitrogen oxide (NO_x) removal, yet its low-temperature activity remains a key limitation for broader applications. We developed an innovative series of microporous N, O-codoped carbon catalysts (NOAC-x) that facilitate the fast SCR reaction. Results demonstrate that the synergy between catalyst micropore structure and surface functional groups governs denitrification performance: Low-temperature calcination induces pore blockage by nitrogen-containing groups (pyridinic N), reducing specific surface area and weakening NH₃/NO adsorption capacity.Moderate calcinatio promotes partial decomposition of nitrogen groups, optimizing the micropore structure while preserving active sites such as carboxyl groups and pyridinic N, thereby significantly enhancing catalytic activity.High-temperature calcinatio triggers pore collapse and decomposition of active groups, degrading performance.NOAC-600 achieved 95% NO_x conversion at 120 °C and exhibited merely a 2% activity decline during a 108-hour stability test. This work provides theoretical guidance for designing microporous N, O-dual-doped carbon-based catalysts and underscores the critical importance of micropore structure and surface chemistry optimization in low-temperature SCR technology.

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A commercially available nitrogen/phosphino-functionalized triethoxysilane was grafted onto the surface of silica-coated magnetic nanoparticles (MNPs, Fe₃O₄@SiO₂) via etherification, affording a series of nitrogen/phosphino-functionalized MNPs (Fe₃O₄@SiO₂-N/P). Subsequent reaction with chloroplatinic acid yielded a series of platinum(II)-anchored functionalized MNPs (Fe₃O₄@SiO₂-N/P-H₂PtCl₆). When these complexes were tested in the hydrosilylation of olefins, the phosphine-modified MNP-chelated platinum catalyst (Fe₃O₄@SiO₂-P2-H₂PtCl₆) was identified as the optimal catalyst. It efficiently promoted the hydrosilylation of olefins under mild conditions, accommodating a broad range of olefins and silanes to afford the corresponding products in moderate to excellent yields and regioselectivity. Moreover, the catalyst could be easily recovered via an external magnetic field and reused for at least nine cycles without significant loss of catalytic activity.

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Bismuth molybdate (Bi₂MoO₆), as one of bismuth-based semiconductors, has aroused great interest in photocatalysis due to its layered structure, tailored morphologies, appropriate band gap, visible-light absorption. Nevertheless, the performance of Bi₂MoO₆ significantly depends on the synthesis approaches that control the phase purity, crystallinity and photocatalytic activity. This work focuses on a detailed investigation about the effects of hydrothermal and solvothermal synthesis approaches on phase evolution, structural features and photocatalytic performance of Bi-based molybdates for the degradation of organic pollutants when subjected to visible light irradiation. The prepared phases were verified by X-ray powder diffraction (XRD) in which hydrothermal process produced α-Bi₂Mo₃O₁₂, whereas solvothermal process resulted in γ-Bi₂MoO₆. When compared with α-Bi₂Mo₃O₁₂, the performance of γ-Bi₂MoO₆ showed improved crystallinity, a medium bandgap (~ 2.3–2.8 eV) and excellent photocatalytic activity with a > 95% degradation of MB within 120 min. The higher performance was ascribed to the enhanced charge separation, extended absorption and definite layered structure. The optimal performance of γ-Bi₂MoO₆ obtained from the solvothermal process demonstrated its potential in visible light-driven water treatment. Therefore, these results collectively reveal that effect of the synthesis process can determine the phase composition and photocatalytic efficiency towards organic pollutants.

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The performance of γ-Bi2MoO6 obtained from the solvothermal process demonstrated its potential in visible light-driven water treatment.

This study synthesized α-diimine nickel catalysts featuring two and three hydroxyl groups (Cat1 and Cat2), along with their corresponding supported catalysts (S-Cat1 and S-Cat2). These catalysts demonstrated high activity in ethylene polymerization, reaching up to 7 × 10⁶ g/molNi·h, yielding polyethylenes with tunable molecular weights (174–553 kg/mol), branching degrees (38–140/1000 C) and higher elongation at break (up to 1230%). The catalyst bearing three hydroxyl groups and its supported catalyst exhibited slightly higher than that of the catalyst with two hydroxyl groups and its supported catalyst respectively, while also producing polymers with relatively higher molecular weights and slightly lower branching degrees. Compared to the homogeneous catalyst, the supported catalysts maintained high activity and thermal stability, yielding polyethylene with higher molecular weight, controllable morphology, high tensile strength (17.9 MPa/22.5 MPa) and moderate elongation at break (870%/660%).

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The development of a selective catalyst for hydroprocessing of phenol production by-products (hydroquinone and catechol) is an important task for increasing the yield of the target product. In this study, the use of in situ generated catalysts based on molybdenum and tungsten compounds (MoP, WP, MoO_x, and WO_x) was proposed for this goal. The performance of the catalysts was investigated in the hydroprocessing of each individual substrate (hydroquinone and catechol), as well as their mixture. It was shown that MoP and WP catalysts were more selective in the partial HDO of hydroquinone and catechol into phenol compared to their oxides; as a result, the selectivity for phenol was higher. The highest selectivity for phenol was 83% and 95% over MoP and WP, respectively. The hydroprocessing of a mixture of phenol, hydroquinone, and catechol (the molar ratio of phenol/hydroquinone/catechol = 7/2/1) was also explored using in situ formed MoP, WP, MoO_x, and WOx catalysts. The phenol content in the product mixture after the reaction changed in the following order: WP (88%) > MoP (75%) > WO_x (55%) > > MoO_x (26%). All catalysts studied were characterized using XRD, XPS, TEM, and EDX methods. Thus, in situ formed MoP and WP can be considered as the suitable catalysts for the selective HDO of hydroquinone and catechol towards phenol. Moreover, the possibility of reusing catalysts MoP and WP during five runs without significant loss of activity was shown.

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In this study, the deactivation behavior of three granular catalysts—Co/Ag, Co/Ag-B, and Co/Ag-Zn—was investigated in the Fischer–Tropsch synthesis process. Silver was introduced as a primary promoter to enhance cobalt reducibility and facilitate hydrogen spillover. Characterization results from XRD, TPR, FESEM, and EDS analyses revealed that Ag incorporation led to a moderate reduction in cobalt oxide reduction temperature and improved reduction behavior compared to undoped catalysts. However, the promotion effect of Ag alone was limited. The presence of boron significantly improved cobalt dispersion, decreased crystallite size, and reduced the rate of deactivation. In contrast, the addition of Zn resulted in the formation of more stable oxide phases and more difficult reducibility, leading to a noticeable decline in catalytic activity. The Co/Ag-B catalyst, benefiting from the synergistic effect of Ag and B, exhibited the highest structural stability and the lowest deactivation rate. These findings highlight the critical role of rational promoter design in developing next-generation stable cobalt-based catalysts for Fischer–Tropsch synthesis.

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The electropolymerization method was explored for 5,10,15,20-tetrakis(4-nitrophenyl)porphyrin (TNPP) and its nickel(II) complex, (Ni-TNPP), by electroreduction. The resulting films on glassy carbon electrodes (GCE) were investigated for their properties and potential as electrocatalysts for the hydrogen evolution reaction (HER). The active surface area of Ni-TNPP-GCE is 6.8 times higher than that of TNPP-GCE. Notably, Ni-TNPP-GCE exhibited an overpotential of 340 mV with a Tafel slope of 95 mV/dec, a R_CT value of 1.612 Ω, and a R_s value of 42.23 Ω. Therefore, in a neutral PBS solution, the electrocatalyst Ni-TNPP-GCE exhibits better electrocatalytic activity than TNPP-GCE. This approach offers a promising pathway for low-cost, efficient hydrogen production and highlights potential alternatives to noble metals in catalysis.

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Achieving cost-effective hydrogenation of 3-hydroxypyridine to 3-hydroxypiperidine is still a challenge issue. Herein, a non-noble metal core–shell structured catalyst Ni_8.0-Co_2.0@SiO₂-5.0–0.10 has been prepared for the hydrogenation of 3-hydroxypyridine with a yield of 95.0%. In this study, a membrane dispersion reactor was used to prepare the core of the catalyst, followed by a hydrolysis process to construct the SiO₂ shell. This semi-continuous method enables the efficient production of core–shell catalysts, not only overcoming the low efficiency of traditional preparation methods but also enhancing catalytic performance. Characterization results indicate that the metal cores synthesized using the membrane dispersion reactor exhibit smaller particle sizes, while the SiO₂ shell effectively prevents agglomeration of the core nanoparticles. This ensures that the catalyst simultaneously achieves a minimum particle size of 9.17 nm and a maximum specific surface area of 110.31 m²/g.

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By using membrane dispersion reactor, a large number of non-noble metal nanoparticles can be prepared quickly, and then coated with a SiO2 shell exhibits remarkable hydrogenation activity, resulting in a 97.5% selectivity and 95% yield of 3-hydroxypiperidine.