Catalysis Letters最新文献

Metal-doped ZIF-67 (M-Z, M = Ni, Cu) was prepared by liquid phase precipitation method, and its microstructure, crystal structure, and specific surface area were determined by characterization methods such as SEM, TEM, FTIR, XRD, XPS, BET, etc. SEM and TEM images show that M-Z is a regular dodecahedron, maintaining the basic morphology of ZIF-67. FTIR and XRD confirm the existence of the crystal structure, and XPS reveals the elemental composition of M-Z, proving the successful doping of the metal. BET data shows that M-Z has an excellent specific surface area, providing favorable conditions for catalysis. The thermal decomposition kinetics and thermodynamics of M-Z on the catalytic decomposition of nitrocellulose at different heating rates (5, 10, 15, 20 K·min^− 1) were studied using DSC. According to the findings, Ni-Z exhibited the greatest catalytic activity on nitrocellulose, with the decomposition temperature advanced by 3.4 ℃ and the activation energy reduced by 12.93 kJ·mol^− 1.

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The primary sources of water contamination are wastes from industrial regions, including pesticide residues, paper, organic textile, and pharmaceuticals. Specifically, organic dyes released by industries have the capacity to be harmful, biorecalcitrant, indestructible, fade-resistant, and pose a significant risk to human health. At 60 °C, Ag/ZnO nanoparticles with various Ag concentrations were prepared. Several characterization methods, including scanning electron microscopy (SEM), UV–vis spectroscopy, and X-ray diffraction (XRD), have been utilized to investigate the Ag/Zn-2. The progress of methylene blue decolorization was examined via UV–vis spectroscopy. The Ag/Zn-2 photocatalysts had a surface area of 89.5 m²/g and a crystallinity of 90%.The catalytic performance for the methylene blue (MB) was assessed. Ag/Zn-2, one of the photocatalysts, had the greatest rate of MB dye degradation, reaching 97.1% in 105 min. After five cycles, the Ag/Zn-2 catalyst showed improved structural stability and durability but lost appoximately 3.8% of its efficiency. The pseudo-1st order kinetic model with a rate constant (k) of 0.03304 min⁻¹ described superoxide and hydroxyl radicals as the main active species in the degradation process. When silver is introduced as a dopant to the zinc oxide crystal structure, the band gap energy is significantly lower, allowing for the absorption of a wider variety of light wavelengths. Furthermore, the presence of Ag helps to prevent electron-hole recombination, which can reduce the photocatalytic efficacy.This study presents a novel way to improve the photocatalytic properties of a basic metal–semiconductor material made from Rumex abyssinicus Jacq root extract, making it a suitable option for environmental remediation.

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We employed the ONIOM model to investigate the role of alkali metals in the conversion of CO₂ and CH₄ into CH₃COOH on CuX-ZSM-5 (X = alkali metal). This hybrid model achieves high efficiency by dividing the computational system into layered regions, where key regions undergo high-accuracy quantum mechanical (QM) calculations, while the remaining regions are addressed with molecular mechanics (MM). The direct synthesis of CH₃COOH involves three sequential reaction steps: the heterolytic cleavage of the CH₄ bond, the formation of acetate from –CH₃ and –CO₂ species, and the subsequent desorption of CH₃COOH. Theoretical model reproduced the experimental kinetics trend for alkali metal doped CuX-ZSM-5 catalysts (K⁺ > Na⁺ > Li⁺ > H⁺). A synergistic effect of X-cations was observed, with its intensity increases as one moves down the group. The CuK-ZSM-5 and CuNa-ZSM-5 have the lowest energy barriers and maintain functionality for a specific period. The remarkable performance of the K⁺ containing catalyst in comparison to the other alkali metals cations, arises from an amalgamation of binding affinities and judiciously balanced metal size. When the alkali metal cations are too small, it coordinatively saturated and fail to activate CO₂ effectively. However, the desorption of CH₃COOH over CuX-ZSM-5 requires a significant amount of energy. This high energy demand leads to the saturation of the catalyst surface with –CH₃COO⁻ species over time, ultimately causing catalyst deactivation. It is critical to enhance the desorption process. The impressive selectivity of CuNa-ZSM-5 and CuK-ZSM-5 in the reaction is attributed to the blocking of active sites by Na and K-cations because of larger size, enabling only single C–H bond breakage. The CuNa-ZSM-5 and CuK-ZSM-5 catalysts exhibit exceptional atomic economy by generating no waste. All atoms from CO₂ and CH₄ are fully incorporated into valuable industrial products. Thus, these catalysts offer an economical, environmentally friendly, and practical approach for converting greenhouse gases into acetic acid with 100% atomic utilization.

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In industry, MoV catalysts are usually used for acrolein oxidation to acrylic acid. But this process is strongly exothermic reaction, high temperatures lead to Mo and V sublimation, and lost part activity. In this work, we prepared three kinds of morphologies Al₂O₃, i.e., Al₂O₃-flower (Al-F), Al₂O₃-irregular (Al-I), Al₂O₃-sheet (Al-S), and coupled them with MoV oxides, respectively, and obtain three kinds of catalysts, MoV-F, MoV-I and MoV-S. We found that the catalytic performance has the order of MoV-S > MoV-I > MoV-F, and MoV-S perform highest acrylic acid selectivity (85.6%). It is found that intercalated Al-S achieve better MoV oxides uniform dispersion, small MoV particles result in rich lattice oxygens, which contributed to its enhanced oxidation capability. Besides, Al-S obtains good thermal conductivity, and this facilitates reaction heat transfer and stability of the catalyst. This study provides new insights into the MoV catalyst for selective oxidation reaction with strong exothermic process.

A series of 1%Rh/γ-Al₂O₃ catalysts was prepared using different Rh-containing precursors (chloride, nitrate, and complex [Rh(NH₃)₅Cl]Cl₂). The catalysts prepared in this work were characterized by various physicochemical methods. Textural and acid–base properties, metal dispersion and metal charge state were characterized by nitrogen adsorption–desorption analysis, scanning electron microscopy with the energy dispersive X-ray analysis, diffuse-reflectance Fourier-transform infrared spectroscopy, transmission electron microscopy, CO chemisorption, X-ray photoelectron spectroscopy. The activity and selectivity of the catalysts were tested in the reaction of decalin ring opening under high pressures. The XPS study showed that rhodium in the surface layers of the samples is present in a metallic state. However, a small positive charge (δ+) is observed on the rhodium atoms due to the interaction of dispersed metal particles with the carrier. This effect is especially noticeable for the sample prepared using the Rh(NO₃)₃ precursor. According to the data, all studied catalysts allow one to obtain a similar set of reaction products, where C₁₀ alkylcyclohexanes predominate. The catalyst activity decreases in the NO₃⁻ > Cl⁻ > [Rh(NH₃)₅Cl]Cl₂ series, that is in the inverse correlation with the rhodium particle size 1.5 nm < 2.2 nm < 17.2 nm (determined by the CO chemisorption method) and 1.7 nm < 2.3 nm < 6.6 nm (determined by TEM). The catalyst synthesized on the basis of rhodium nitrate demonstrates a reaction selectivity close to 74% for the partial ring opening at the total decalin conversion of 67%. The highest activity and selectivity for this catalyst are possibly accounted for by the relatively small size of metal particles formed on the alumina support. Also, some changes in the activity and selectivity of the catalysts observed with variation of the major reaction parameters, such as temperature, pressure, space velocity and H₂/C₁₀ molar ratio were determined.

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Transition metals have a broad application prospect in sulfate radical-advanced oxidation process (SR-AOP) due to their advantages of high activation efficiency and no external energy input. However, transition metals present several challenges, including a cumbersome preparation process, low effective utilization of metal sites and leakage of metal ions. These limitations hinder the practical application of transition metals in sulfate radical-advanced oxidation process. In this study, ZIF67-Co₃O₄ catalyst was prepared using zeolite imidazolium framework derivatives as precursor. The performance of ZIF67-Co₃O₄ activated persulfate for the degradation of tetracycline (TC) and various factors affecting the degradation performance were investigated. The degradation reaction mechanism was also summarized. The experimental results showed that: The TC removal rate of ZIF67-Co₃O₄ + PMS system was 75.07% at 90 min, which possessed high removal efficiency. The ZIF67-Co₃O₄ catalyst exhibited high stability, it had a high catalytic activity after five recycling cycles. The active radicals generated by ZIF67-Co₃O₄ activated PMS degradation of TC pollutants were ·OH, SO₄⁻·, ¹O₂, and ·O₂⁻.

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The catalytic conversion of CH₄ by O₂ into syngas (known as partial oxidation of methane; POM) is a practical approach for depleting CH₄ concentration as well as achieving excellent H₂ yield with high H₂/CO ratio. The pentasil zeolite family having different SiO₂/Al₂O₃ ratios 10, 20, 25, and 30 (abbreviated as CBV10A, CBV20A, CP810E, and CBV3024E) is found to be an excellent carrier for Ni. These Ni-containing molecular sieves are investigated for POM and characterized by X-ray diffraction, Raman-infrared spectroscopy, thermogravimetry, temperature-programmed techniques, and transmission electron microscopy. 5Ni/CBV3024E catalyst has smaller number of active sites, 5Ni/CP810E contains unstable active site and mordenite-based Ni catalysts (5Ni/CBV10A and 5Ni/CBV20A) attain higher metal-support interaction. 5Ni/CBV20A outperforms others due to the presence of reducible NiO under moderate and strong interaction. It shows an initial 40% H₂ yield at 600 ^oC and 81% H₂ yield at 750 ^oC. The high-temperature POM reaction limits the H₂/CO ratio close to the stoichiometric value of POM (~ 2), indicating the direct pathways of POM reaction at high temperatures. The high POM activity with the option of a wide range of H₂/CO (4.12–2.26) using Ni-containing molecular sieve may gain industrial-level attention in the coming future.

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Lignocellulosic-based (LCB) bioethanol production is challenged by the presence of inhibitory compounds in pretreated LCB hydrolysates limiting productivity. The negative impact of these inhibitory compounds on LCB bioethanol production kinetics remain understudied. Hence, this study modelled the kinetics of bioethanol fermentation using nanoadsorbent-detoxified potato peel waste (PPW) hydrolysate. Four different fermentation processes under both separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) conditions, including A (SHF with non-detoxified hydrolysate), B (SSF with non-detoxified hydrolysate), C (SHF with detoxified hydrolysate), and D (SSF with detoxified hydrolysate) were evaluated for bioethanol productivity. Higher productivity of 1.23 and 1.16-fold increments were recorded for fermentation processes C and D. Thereafter, the experimental data for cell growth, bioethanol production and substrate utilisation were well-fitted by the logistic function, modified Gompertz, and Luedeking-Piret models respectively. Moreover, the obtained root-mean-square error (RMSE) and mean square error (MSE) were low, while the accuracy factor (AF), bias factor (BF), slope and regression coefficient (R²) were close to 1. The bioethanol production processes were largely growth-associated (α) as α values (g ethanol/g substrate) were higher than β values (g ethanol/g substrate/h). The models were effectively implemented, demonstrating their usefulness to elucidate bioethanol productivity kinetics for improved process design and the development of large-scale bioethanol production.

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Graphitic carbon nitride (g-C₃N₄) is a visible light catalyst with considerable potential, offering broad application prospects in fields such as pollutant decomposition. In this study, we systematically investigated the geometric, electronic, and optical properties of B-doped, P-doped, and B/P co-doped g-C₃N₄ using first-principles methods. We also examined the adsorption effects of g-C₃N₄ on emerging oxidants, periodate (PI) and Peroxymonosulfate (PMS). The results showed that B/P co-doping significantly narrowed the band gap of g-C₃N₄ to 0.39 eV, transforming it into a direct band gap structure. Additionally, the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) exhibit enhanced delocalization, particularly over the bridging N1 atoms, which improved carrier mobility. Compared to pristine g-C₃N₄, the optical absorption demonstrated a more favorable response to visible light. Notably, the B/P co-doping system significantly increased the adsorption capacity of g-C₃N₄ for PI and PMS, promoting the generation of reactive species such as singlet oxygen (¹O₂), sulfate radicals (SO·₄⁻), and hydroxyl radicals (·OH), providing a favorable pathway for the degradation of pollutants in water. In summary, B/P co-doping significantly enhances the photocatalytic performance of g-C₃N₄, establishing it as a highly efficient, eco-friendly, and cost-effective metal-free photocatalyst with great potential for advanced oxidation processes under visible light in wastewater treatment.

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Three-way catalyst (TWC) stands as the state-of-the-art technology for controlling emissions in natural gas vehicles, but its utilization can generate NH₃ by-product. This study proposed a novel strategy for reducing NH₃ emissions during three-way catalytic reaction process of Pd-based catalysts by adding Ru. Catalysts Pd/LA + Si, Pd/LA + Ru/CZLN, and Pd/LA + CZLN were fabricated through incipient wetness impregnation and mechanical ball-milling methods. Testing under simulated exhaust conditions showed that Pd/LA + Si produced high NH₃ levels, while Ru/CZLN addition significantly reduced NH₃ emissions from 330 to 20 ppm. Conversely, the addition of CZLN facilitated steam reforming and water–gas shift reactions, generating more H₂ for NO reduction, which led to an increase in NH₃ emissions. Experimental evidence confirmed that Ru/CZLN could effectively decompose NH₃, which was produced over Pd/LA, into N₂ and H₂, thereby significantly reducing NH₃ emissions. This study provides a promising approach for developing TWC with low NH₃ emissions for natural gas vehicles.

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