Catalysis Letters最新文献

Transition metal-based Metal–Organic Frameworks (MOFs) (M-BDC (M – Ni, Cu, Zn)) are prepared by solvothermal method. The loading of MOF on the support material, rGO, is done through the simple ultrasonication technique. The MOF materials are characterized using powder X-ray diffraction, Fourier-transform infrared spectroscopy, Scanning electron microscopy, and Thermogravimetric analysis. The catalytic activity of the synthesized MOFs is tested towards the dehalogenation of aryl halides reaction. The reaction conditions are optimized, in which the Ni-BDC MOF shows high catalytic activity. Hence, Ni-BDC MOF is loaded with different weight percentages (10wt%, 20wt%, 30wt%, and 40wt%) of rGO. Subsequently, 10 wt% Ni-BDC MOF/rGO is found to be the best catalyst among the other weight percentages of rGO-loaded catalysts. Moreover, the catalyst is easily recoverable and can be used for many cycles without leaching of active species, structural changes, and loss in activity.

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In the present study, zeolite H-BEA catalyst has been modified by controlled desilication post modification route using first with cationic surfactant, (6-Bromohexyl)trimethylammonium Bromide (6-Br-TMA) designated as MBB catalyst and then the other with 6-Br-TMA and yeast, designated as MBBY catalyst. These newly synthesized catalytic materials have been characterized by several techniques such as, Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction, scanning electron microscopy, solid state NMR (²⁹Si, ²⁷Al, ¹H) N₂ sorption isotherm analysis, thermogravimetric analysis, ammonia temperature program desorption (NH₃-TPD) analysis, etc. These mesozeolites were found to exhibit enhanced physicochemical (BET surface area, surface acidity, pore volume, mesoporosity, etc.) characteristics as compared to their parent zeolite H-BEA. Catalytic assessement studies of the synthesized zeolites has been demonstrated via conducting experiments involving esterification of levulinic acid (LA) and n-hexanol. Parametric studies has been undertaken in order to get maximum LA conversion by varying several reaction parameters such as molar ratio (acid to n-hexanol), catalyst concentration, reaction time, etc. Further catalysts’ reusability studies has been carried out to assess their potential for reusability. The results indicated better catalytic performance of the zeolite H-BEA which is modified with the use of yeast (MBBY) as compared to microporous zeolite H-BEA and MBB catalyst which may be due to its enhanced surface area and surface acidity.

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This study focuses on the preparation of fatty acid ethyl esters (FAEE) in a solvent-free system using high-acid-value waste oil as the raw material. The research involves the addition of two enzymes with different substrate specificities, accompanied by ultrasonic assistance. The investigation explores the impact of enzyme addition (3–7 wt%), enzyme ratio (3:1–1:3), alcohol–oil ratio (5:1–25:1 mmol/g), reaction temperature (30–70 °C), reaction time (30–210 min), and ultrasonic power (0–150 W) on the experimental outcomes. Reaction conditions were optimized by analyzing regression models. The predicted optimal process parameters for FAEE conversion are as follows: enzyme addition of 5.46 wt%, enzyme ratio of 1:2.23, alcohol–oil ratio of 13.79:1 mmol/g, reaction temperature of 60 °C, reaction time of 160 min, and ultrasonic power of 120 W. Under these optimized conditions, three validation experiments were carried out to take the average value, and the conversion rate of FAEE was 93.57 ± 1.17%, which was in good agreement with the predicted value. These results showed that the synergistic effect of the two enzymes accelerated the migration of acyl groups, verified the advantages of the dual enzyme as a catalyst, and provided theoretical support for the preparation of biodiesel by the dual enzyme system.

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Graphitic carbon nitride (g-C₃N₄) is a polymer conjugated composed of carbon and nitrogen atoms in a graphite-like structure. Despite its structure, its catalytic potential is limited due to its small surface area, abundance of electron pairs, and low UV absorption. Recent research has focused on synthesizing nanocomposites from g-C₃N₄ and meso-metalloporphyrins, which exhibit synergistic properties for photocatalysis through π-π interactions. This study aims to synthesize zinc (ZnP) and palladium (PdP) meso-metalloporphyrins from cardanol, a major constituent of cashew nut shell liquid (CNSL), to create g-C₃N₄ nanocomposites. These systems were characterized using UV-vis, FT-IR, NMR, TGA, and SEM, and applied to reduce 4-nitrophenol (4-NP) in wastewater to the less toxic 4-aminophenol (4-AP). The synthesis of g-C₃N₄ with PdP and ZnP produced new nanocomposites, g-C₃N₄/PdP and g-C₃N₄/ZnP, with yields of 43% and 16%, respectively. These materials demonstrated significant success in the photocatalytic reduction of 4-NP, highlighting the potential of renewable catalysts and promoting cleaner chemical processes, thereby reducing environmental impact.

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The development of efficient catalyst for the epoxidation of alkenes is crucial in industrial application. Herein, bismuth molybdate samples with different surface properties (BMO-x, x = A, B, and C) were synthesized via a hydrothermal method and tested in cyclohexene epoxidation. The BMO-A catalyst exhibited superior catalytic activity, achieving a 67.3% cyclohexene conversion with 83.6% epoxide selectivity, outperforming the BMO-B (17.4% conversion, 40.2% selectivity) and BMO-C (27.0% conversion, 59.1% selectivity) catalysts. This enhanced activity is attributed to BMO-A’s higher percentage of surface exchangeable oxygen, high surface Mo/Bi ratio, and optimal surface wettability. The high epoxidation performance of the BMO-A catalyst was attributed to its larger percentage of surface exchangeable oxygen, high surface Mo/Bi ratio, and suitable surface wettability. Specifically, the BMO-A with more exchangeable oxygen facilitated the adsorption of H₂O₂ molecules, and subsequent reaction with cyclohexene to yield epoxy-cyclohexane. The hydrophilic surface of BMO-A further enhanced H₂O₂ enrichment at the reaction interface. This work provides a new strategy for preparing highly active catalyst for the epoxidation of alkenes.

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Fe₂O₃/ZnO fiber membranes, characterized by their high specific surface area and expanded UV–Vis absorption spectrum, were successfully synthesized through a process of electrospinning followed by calcination. The diameters of Fe₂O₃/ZnO fibers are approximately 150 nm, and the specific surface areas of Fe₂O₃/ZnO fiber membranes are around 29 m²/g. XRD, SEM, and XPS results confirm the formation of a heterojunction between ZnO and α-Fe₂O₃. Compared with pure ZnO fiber membrane, the UV–Vis absorptions of the Fe₂O₃/ZnO fiber membranes are extended, and transient photocurrent intensities are significantly increased from 0.65 mA/cm² to 0.86 mA/cm². Free radical capture experiments further reveal the generation of abundant •OH radicals, which play a crucial role in enhancing the photocatalytic performance of these Fe₂O₃/ZnO fiber membranes. Optimization studies have determined that the optimal molar ratio of Fe to Zn is 8 mol% in the Fe₂O₃/ZnO heterojunction, which corresponds to a 45% improvement in photocatalytic degradation efficiency for MB. Furthermore, the remarkable cycling stability of the Fe₂O₃/ZnO fiber membranes demonstrate their substantial potential for photocatalytic dye wastewater treatment.

Capturing and transforming diluted CO₂ into energy-rich fuels is a notable and increasingly interesting challenge in renewable energy research. This study successfully developed an enhanced form of silicon oxide with a unique exterior level and a SiO₂/anatase phase interface. A base complex of Pd (II) and Cu (II) was created using a simple synthetic method, along with 3-chloropropyltriethoxysilane loaded on dendritic fibrous nanosilica (Cu-IL/DFNS and Pd-IL/DFNS). The use of DFNS provided numerous hydroxyl groups for the stable loading of Cu-IL and Pd-IL through chemical bonding interaction. Moreover, Cu-IL and Pd-IL were able to control the appropriate strand dimensions and offer active adsorption locations of metal groups, aiding in the chemical absorption of carbon dioxide. The DFNS composite’s topography and mesoporous structure remained consistent upon Cu-IL and Pd-IL loading, indicating the maintained crystalline form. The use of light-driven biomass valorisation has become a leading field for CO₂ to CH₄ photoreduction due to its sustainable characteristics. Photocatalytic CO₂ reduction is a highly beneficial method to counteract the negative impacts of greenhouse gases and achieve carbon neutrality. The construction of active sites with specific designs that exhibit increased activity and selectivity for photoreduction is a significant challenge. The reduction of carbon dioxide is crucial in today’s era of petroleum refineries. The present paper showcases the initial application of a reusable nanocatalyst with outer magnetism for the efficient and specific light reduction of CO₂ to CH₄ under eco-friendly circumstances that employ earth-friendly reduction, ambient pressure, cool thermal condition, and sustainable dehydration reactants in a shorter duration. This method extends substantial advantages, incorporating substantial financial return and acceptance of functional groups. This investigation emphasizes the possibility of integrating 3D nanoparticle architecture with eco-friendly chemical processes to create highly efficient catalytic reactions for the targeted light reduction of CO₂ to CH₄.

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A hybrid catalyst based on Mo132 as a Keplerate type polyoxometalate and MimAm as an ionic liquid was used as an effective catalyst for selective epoxidation of different alkenes with H₂O₂ as a green and safe oxidant. The effects of various parameters such as catalyst, oxidant amounts, reaction time, and temperature were also studied in selective epoxidation of cyclooctene. Moreover, under the optimal reaction conditions, the epoxidation of different alkenes was performed with 54–100% yields. Interestingly, this catalyst complies with the benefits of easy preparation, recovery, recycle, high catalytic activity, simplified workup, and flexible composition.

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5-Hydroxymethylfurfural known as a biomass-derived pivotal platform chemical is an important alternative for petroleum-based chemicals. However, its large-scale production faces serious barriers and limitation in terms of 5-Hydroxymethylfurfural yield and production cost. In the present work, dual structure directing agent SAPO_34 molecular sieve was prepared by hydrothermal method and XRD, SEM, XRF, BET and pyridine FTIR spectroscopy techniques were employed to characterize the synthesized catalyst. The Lewis/Bronsted SAPO_34 molecular sieve performance was evaluated in the conversion of glucose into 5-Hydroxymethylfurfural in γ-Valerolactone/water solvent system. The effects of alkaline earth and alkali metal salts were also studied. Promising results were obtained which could optimize the 5-Hydroxymethylfurfural yield up to 92%. The ascending overall 5-Hydroxymethylfurfural selectivity trend suggests that the formation of 5-hydroxymethylfurfural is in dominant position at the expense of glucose until 5-HMF yield peak values are obtained. The introduction of metal salts to the reaction medium was beneficial to the reaction efficiency and it was shown that the cations rather than the anions play the main role in the promotion of the conversion. Furthermore, salts containing cations of smaller ionic radius and higher charge density demonstrating superior performance. The analysis of reaction kinetic revealed that glucose conversion activation energy decreased by 5.8 kJ/mole with the addition of MgCl₂ to the reaction medium. Finally, the tests to evaluate the catalyst’s recyclability were conducted both with and without the addition of salt.

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To effectively mitigate the global warming issue, it is crucial to develop advanced technologies that can significantly reduce carbon dioxide emissions. CO₂ hydrogenation for methanol synthesis is increasingly recognized as a promising chemical approach for the green-house gas utilization. In this study, we present a highly active, selective and stable Mo modified ZnCu-MOF and ZnCuAl-LDH composite catalysts, which achieves 18% CO₂ conversion and 70% methanol selectivity at 230 °C, 3.0 MPa at a space velocity of 3600 mL·g_cat⁻¹·h⁻¹. Furthermore, after 140 h of operation, the catalyst demonstrates superior durability. In-situ DRIFT results reveal that this CO₂ hydrogenation reaction over the ZnCu-MOF and ZnCuAl-LDH composite catalysts proceeds through key intermediate formate species, ultimately leading to the methanol formation. In contrast, the Mo-modified catalysts facilitate the CO insertion reaction (CO₂ → CO*, CO* + *CH_x → CH₃OH), thereby enhancing the methanol yield.

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