Catalysis Letters最新文献

To develop efficient catalysts for CO₂ hydrogenation to dimethyl ether, Cu–Al₂O₃–TiO₂–Ti₃C₂/HZSM-5 bifunctional catalysts were prepared by the surfactant PVP-assisted coprecipitation. The influence of Ti₃C₂ on Cu–Al₂O₃-based catalysts was investigated. The characterization results revealed that slight oxidation of the Ti₃C₂ surface generated highly dispersed TiO₂ nanoparticles that the doping of TiO₂‒Ti₃C₂ in the Cu‒Al₂O₃ catalyst increased the specific surface area of the catalyst and promoted the formation and growth of Cu nanoparticles, and that strong interactions occurred between TiO₂‒Ti₃C₂ and the Cu components. The number of oxygen vacancies at the interface between TiO₂‒Ti₃C₂ and Cu increased by 17%, and the electronic kinetic energy of Cu⁰ decreased by 0.1 eV, with the electron-rich oxygen vacancies transferring electrons to Cu²⁺ ions and maintaining more Cu species in lower oxidation states. Reactions were carried out at 260 °C and 3.0 MPa with a gaseous hourly space velocity (GHSV) of 1500 cm³‧g⁻¹‧h⁻¹ using Cu–Al₂O₃–TiO₂–Ti₃C₂/HZSM-5 with 5.0 wt% Ti₃C₂ as the hydrogenation catalyst, which provided a CO₂ conversion of 26.8% with 57.8% selectivity for DME.

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Decatungstate ((nBu₄N)₄W₁₀O₃₂, marked as DTs) and PMo_12-nV_n could be easily synthesized via polymerization in acidic aqueous solution. They can efficiently catalyze the oxidation of cyclohexane to afford cyclohexanone and cyclohexanol under visible light, affording about 30% conversion in the presence of additive HCl. This is the first example to show the influence of HCl on oxidizing capacity for DTs and PMo_12-nV_n. It was found that PMo_12-nV_n could induce the generation of chlorine radical in the presence of HCl, playing a significant role to realize the oxidation of cyclohexane.

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The presence of alkali metals in flue gas can lead to catalyst poisoning, which can significantly impact the de-NOx efficiency of the catalyst. There is a lack of specific studies on the influence of potassium (K) poisoning on the efficiency of γ-Fe₂O₃. In this study, the mechanism of K poisoning on the γ-Fe₂O₃ surface was studied based on DFT, and the influence of K on molecular adsorption and SCR reaction process was analyzed. The results show that the K₂O and KCl provide O, K, and Cl ions when deposited on the catalyst surface. The adsorption and dehydrogenation processes of NH3 were enhanced to varying degrees near the O and Cl iron sites, but the subsequent generation and decomposition of NH₂NO were inhibited. On the sites near K cations, the adsorption, dehydrogenation, and subsequent SCR reaction processes of NH₃ are hindered, and the adverse effects on the reaction are greater on the Fe sites closer to K. As well as the presence of K can to some extent promote the adsorption of NO and O₂.

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An extremely efficient green protocol for palladium acetate-catalysed ligand-free Suzuki–Miyaura cross-coupling reactions of aryl/heteroaryl bromides with aryl/substitute aryl boronic acids in neat ‘Water Extract of Leaf Ash of Neem’ (WELAN)’ was developed. This method offers a simple, mild, efficient and highly cost-effective alternative to the existing protocols since the reaction proceeds in natural feedstock WELAN at room temperature in air at very short reaction times (5–60 min) under ligand/external base/promoter/organic medium free conditions. Here WELAN has been found to be the effective base and reaction medium for this cross-coupling reaction with high turnover number (TON). This manuscript also theoretically depicts the probable mechanism of WELAN catalysed cross-coupling reaction.

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Based on the first-principles density-functional theory, formation energies, transition energy levels of M (M = Mo, W) doped α-BiNbO₄ systems are studied. The calculation results show that the donor defects form easily under Bi-rich condition. Of these, the W_int (W interstitial) and Mo_int (Mo interstitial) are the two main defects that lead to n-type conductivity. Then, the electronic structures of M-mono-doped and M/O_vac (O vacancy)-codoped α-BiNbO₄ were investigated. Our results show that the band gap of W_int/O_vac-codoped α-BiNbO₄ is reduced by 0.43 eV, and the conduction band minimum and valence band maximum are reduced by 0.20 and 0.23 eV, respectively, compared to pure α-BiNbO₄, with less driving force required for the redox reaction process and then an increased redox rate. The α-BiNbO₄ with W_int+O_vac defects with n-type conductivity has good photocatalytic activity in water splitting.

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In this research, microorganisms were used to produce Gd₂ZnMnO₆ NFs in a biological process instead of a chemical method as a nanocatalyst. Considering the capability of the microorganisms to synthesize nanofibrous (NFs) upon exposure to metal ions, microorganisms were employed to produce Gd₂ZnMnO₆ NFs through a biological process. The utilization of chemical modification to fabricate environmentally friendly heterogeneous nanocatalysts has proven to be highly appealing in the context of synthesizing 3-aryl-2-oxazolidinones using alkenes, carbon dioxide, and amines in an aqueous solution. The role of diverse variables in the creation of 3-aryl-2-oxazolidinones has been thoroughly investigated. Notably, Gd₂ZnMnO₆ NFs demonstrates remarkable efficiency in the production of 3-aryl-2-oxazolidinones due to its unique morphology. The morphology of Gd₂ZnMnO₆ NFs contributed to the creation of a desirable outer layer for the creation of 3-aryl-2-oxazolidinones. The findings demonstrated that the utilization of Gd₂ZnMnO₆ nanofibers positively impacts the effectiveness of the creation of 3-aryl-2-oxazolidinones. This can be attributed to the nanofibers' impressive mechanical and ionic internal characteristics, as well as their exceptional thermal sustainability and persistent colloidal sturdiness. Consequently, employing the host–guest method, the system could be regarded as an exemplary nanocatalyst. A diverse array of olefins was successfully transformed into desirable products, independent of the electronic nature of the substitutes. The involvement of heterogeneous mixtures did not impede the progression of the reaction. Moreover, the 3-aryl-2-oxazolidinones were easily distinguished from the Gd₂ZnMnO₆ nanofibers, and the medium exhibited the ability to undergo multiple cycles of usage without experiencing a notable decline in their catalytic activity and selectivity. This approach offers notable advantages, including a strong economic capability and the potential to withstand functional groups.

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Synthesis of biogenic Gd2ZnMnO6 nanofibrous for creation of 3-Aryl-2-oxazolidinones from alkenes, carbon dioxide, and aminesSynthesis of biogenic Gd2ZnMnO6 nanofibrous for creation of 3-Aryl-2-oxazolidinones from alkenes, carbon dioxide, and amines

Efficient catalysts for separating electron–hole pairs are crucial for improving the quantum yield and activity of photocatalysts. This study systematically investigates the properties and performance of monolayers of Janus SXSiN₂ (X = Cr, Mo, W) using the first-principles computational methods. The research findings suggest that biaxial strain can induce an indirect-to-direct bandgap transition in Janus SXSiN₂ and can also modulate the bandgap and band edge positions. Surface vacancy defects play a critical role in enhancing the charge carrier separation ability of Janus SXSiN₂, leading to remarkable photocatalytic performance. Moreover, the synergistic effect of biaxial strain and vacancy defects can significantly improve the catalytic performance for the HER. This study provides a theoretical foundation for further development of efficient two-dimensional Janus photocatalysts.

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Biaxial strain can modulate the bandgap and band edge positions. Surface vacancy defects play a critical role in enhancing the charge carrier separation ability. Janus SXSiN2 exhibits excellent photocatalytic performance for the HER reaction due to the synergistic effects of strain and vacancy defects.

Sugar compounds are an important part of biomass resources, and their catalytic conversion can prepare a series of platform compounds, such as lactic acid and polyols. One of the key steps is the isomerization of aldoses to ketoses. However, finding a simple method to efficiently convert aldoses to ketoses remains a great challenge. Herein, we report a core–shell structured catalyst, Pt/SiO₂@Mg(OH)₂, for the efficient conversion of xylose as well as the further conversion of xylose to xylulose. Xylose, a five-carbon sugar unit with the highest content in biomass, was used as the object of study to determine the optimal reaction conditions in the aqueous system by adjusting the loading amount of Mg(OH)₂, catalyst addition, reaction temperature, and reaction time: In the optimum aqueous conditions, the yield of xylulose was 23.61%. We also investigated the effect of solvent effects on the hydrothermal reaction and determined the optimal solvent ratio, the yield of xylulose reached 31.74% at H₂O:MeOH (8:2). We anticipate that this research result can provide a theoretical basis and reference for the industrialized production of subsequent sugar isomerization.

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