Reaction Kinetics, Mechanisms and Catalysis最新文献

This study investigates methods for optimizing diesel fuel production through hydrotreating mixtures of straight-run gas oil (SRGO), cooking gasoil, and light cycle oil (LCO). Experiments were conducted in a micropilot fixed-bed reactor using two catalysts: an industrial Co-Mo/γAl₂O₃ catalyst and a laboratory-prepared Co-Mo/γ-Al₂O₃ catalyst. The operating conditions included temperatures of 340 °C, 360 °C, and 380 °C; a pressure of 75 bar, liquid hourly space velocities (LHSV) of 1 h⁻¹ and 1.5 h⁻¹, and an H₂/feedstock ratio of 500 Ncm³/cm³. The hydrotreated products were thoroughly analyzed for key properties, including density, degree of desulfurization, hydrogenation of polycyclic aromatic hydrocarbons (PAHs) and total aromatics, diesel index, lubricity, and pour point. The objective was to produce diesel fuels that meet the specifications of the European EN 590 standard.

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Mo-doped mesoporous tin phosphate (Mo–SnP) was synthesized via a hydrothermal method and evaluated for its catalytic activity and recyclability in the liquid-phase alkylation of toluene with benzyl chloride. XRD, FT-IR, TEM, and N₂ physisorption characterizations confirmed the uniform incorporation of Mo species into the tin phosphate framework without forming segregated phases. NH₃-TPD and DRIFT analyses revealed that Mo doping modulated acidity by reducing strong acid site strength and introducing Lewis acid sites. The optimized 0.2Mo-SnP catalyst demonstrated high activity (119.2 mmol g⁻¹ h⁻¹) in the alkylation of toluene with benzyl chloride, notably maintaining undiminished activity over three cycles, in contrast to undoped SnP, which exhibited over 50% conversion decline within three cycles. TG-DSC and N₂ physisorption studies demonstrated that Mo doping mitigated strong adsorption of reaction products, preventing pore blockage during regeneration and preserving structural integrity.

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In the present study, high-purity and uniform Au₁₄₄-(SCH₂Ph)₆₀ nanoclusters with a size of 1.8 nm were synthesized. TiO₂ and Ce^δ+ modified TiO₂ were prepared by different methods. Au₁₄₄-(SCH₂Ph)₆₀ nanoclusters were then dispersed on Ce^δ+ modified TiO₂ supports to investigate the photocatalytic degradation of methylene blue (MB) under sunlight irradiation. The photocatalytic performance results showed that after 60 min, the degradation efficiency of MB over pure TiO₂ was 68.4%. Slight improvements were observed for (CeO₂)_0.03/TiO₂ and (CeO₂)_0.03-TiO₂, with degradation efficiencies reaching 69.8% and 70.2%, respectively. However, when the Au₁₄₄ cluster were loaded onto these supports, the degradation efficiencies were significantly enhanced to 73.3%, 81.2%, and 90.2% for Au₁₄₄/TiO₂, Au₁₄₄/ (CeO₂)_0.03/TiO₂ and Au₁₄₄/ (CeO₂)_0.03-TiO₂,. The catalysts were thoroughly characterized using X-ray powder diffraction (XRD), Matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS), Ultraviolet (UV) Raman spectroscopy, and UV–vis absorption spectroscopy. Systematic characterizations revealed that the incorporation of trace amounts of Ce^δ⁺ into the TiO₂ lattice red-shifted the absorption edge of TiO₂ into the visible portion of the solar spectrum and increased the number of oxygen vacancies. These modifications not only stabilized the Au₁₄₄-(SCH₂Ph)₆₀ nanoclusters on the support but also contributed to the enhanced photocatalytic activity for MB degradation under sunlight irradiation. Notably, compared to forming gold nanoparticles on TiO₂ and (CeO₂)_0.03/TiO₂, the Au₁₄₄ clusters exhibited superior structural stability in the Au₁₄₄/ (CeO₂)_0.03-TiO₂ catalyst, which was maintained even after storage in air at room temperature for 1 year.

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The green synthesized EDTA@ SiO₂/CeO₂/Fe₃O₄ nanocomposites (NCs) by the Echinops L. plant was characterized using several techniques, including SEM, EDS, FTIR, XRD, and UV–vis. The heterogeneous photocatalyst EDTA@ SiO₂/CeO₂/Fe₃O₄ NCs (dose: 0.1 g, pH_pzc = 4.4) enhanced the efficiency (99.5%) and adsorption capacity (995 mg g⁻¹) of Eriochrom black-T (EBT) dye degradation from aqueous solution under visible light radiation (tungsten, 100 W). In comparing the estimated correlation coefficient (R²) and reduced Chi-square (χ²) values using nonlinear isothermal models, the same value of (R² = 0.9998) was calculated for the Langmuir, Freundlich, and Temkin models. In contrast, the equilibrium was most accurately described by the Freundlich model, which had the smallest (χ² = 30.049) value. The non-linear kinetic models for evaluating EBT degradation showed that the Elovich and pseudo-second order (PSO) models matched the experimental data with the highest R² value and the lowest χ² value. Additionally, the Elovich model confirmed PSO results for showing the significant role of chemical adsorption in the rate-determined step. The studied thermodynamic parameters of the EBT degradation confirmed the exothermic process with ∆H° = − 0.796 kJ mol⁻¹ K⁻¹ and negative values of ∆G° for the spontaneous degradation process at (303–318 K). The effects of scavenger agents in EBT photodegradation on NCs revealed the significant role of photogenerated free radicals as: OH^• >  > e⁻ > O₂^−• > h⁺. The reusability of NCs indicated good results after the fourth time of EBT removal (99.23, 96.66, 94.35, 95.12, and 94.35%) at 40 min for initial pH = 1. Finally, antimicrobial activity was studied for the Echinops L. plant and EDTA@SiO₂/CeO₂/Fe₃O₄ NCs at different concentrations.

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Schematic for the impact of light-generated free radicals on the EBT degradation using green-synthesized photocatalyst EDTA@SiO2/CeO2/Fe3O4 NCs at different pH levels under visible light.

Silica nanoparticulate (w-SiO₂)- and hydroxyapatite nanorod (HAP)-supported metallic Ag catalysts were prepared by the precipitation and subsequent wet chemical reduction method. Metallic Ag nanoparticulates with average particle sizes ranging from 4.8 to 9.3 nm formed and well anchored at the nanosized support surfaces. The particle sizes of metallic Ag nanoparticulates at neutral w-SiO₂ surfaces were smaller than those at basic HAP surfaces. Small-sized metallic Ag nanoparticulates of Ag_0.1−2.0/w-SiO₂ catalysts exhibited higher catalytic activities towards p-aminophenol in direct hydrogenation of p-nitrophenol with gaseous hydrogen (H₂) than the large-sized ones of Ag_0.1−2.0/HAP catalysts. The reaction activation energy on Ag_2.0/w-SiO₂ catalyst was less than that on Ag_2.0/HAP catalyst, which discloses that small-sized metallic Ag nanoparticulates could conduct p-nitrophenol hydrogenation by overcoming a lower reaction energy barrier at mild reaction temperatures of 110–170 °C.

In this study, photocatalytic oxidation was applied to remove methyl orange (MO) dye from an aqueous solution. The effects of various parameters, including material concentration, H₂O₂ concentration, pH value and the initial dye concentration were investigated. A novel manganese nitroprusside (MnNP) catalyst was synthesized using the precipitation method and characterized through XRD, SEM, RDs, Raman, FTIR and BET techniques. The MnNP exhibiting an orthorhombic structure has a band gap energy of 2.54 eV and a surface area of 8.9 m²g⁻¹. The results revealed that the removal of MO elimination increased with higher concentrations of H₂O₂ and greater catalyst doses. The optimum conditions determined at room temperature were as follows: dye concentration of 10 mg/L, MnNP concentration of 0.5 g L⁻¹, H₂O₂ concentration of 0.238 mM, and pH of 2 achieving a removal efficiency of 100% after 20 min of reaction. The results indicate that MnNP is a highly effective visible-light-driven photocatalyst for the degradation of MO under sunlight irradiation.

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This study evaluates the photocatalytic and adsorptive performance of hydrotalcite (HT), titanium dioxide (TiO₂), and HT–TiO₂ composites for the degradation of methylene blue in aqueous solution. HT exhibited the highest adsorption capacity, followed by HT–TiO₂ composites, with TiO₂ showing the lowest performance. Adsorption followed the Langmuir isotherm model, indicating a homogeneous surface. Under UV irradiation, photocatalytic efficiency improved for all materials, with HT–TiO₂ composites showing superior performance. The addition of hydrogen peroxide further enhanced degradation, particularly in combination with UV light. The results suggest that combining photocatalysis and oxidation processes effectively degrades methylene blue, with HT–TiO₂ composites showing strong potential for environmental applications. This synergistic effect is attributed to the enhanced generation of reactive oxygen species (ROS), such as hydroxyl radicals (·OH), when UV irradiation activates the photocatalyst and simultaneously decomposes hydrogen peroxide. These ROS accelerate the breakdown of methylene blue molecules, resulting in higher degradation rates and shorter treatment times compared to individual processes.

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To illuminate the hydrothermal aging mechanism of Cu-SSZ-13 catalysts, catalytic performances and physicochemical properties of selective catalytic reduction (SCR) samples at different aging temperatures (600 ~ 900 °C) and water vapor contents (WVC, 5 ~ 20 V%) were investigated via catalyst sample testing device and micro characterization tests. The impacting laws of inlet conditions on SCR reaction progress and axial reactor performance were revealed by one-dimensional reactor models. The results show that both the increasing aging temperature and the decreasing WVC induced the collapse of molecular sieve structure and the decrease of CHA diffraction peak values. The Cu²⁺ inside molecular sieve diffused to catalyst surface and aggregated to form Cu^xO species that blocked the pore channels. The decreases in specific surface area and pore volume, as well as the increase in pore size, weakened the catalytic and adsorption capabilities. The active site amount and storage capacity of NH₃ also decreased, which increased the transient catalytic response speed and the corresponding side reaction rate. Thus the NO conversion rate was significantly reduced. Overall, the effects of aging temperature on catalytic performance and physicochemical property were significant than that of aging atmosphere. Additionally, with the increasing axial position, the increase slope of conversion rates of NO_x and NH₃ reduced at both fast and standard SCR progress because the lowered NH₃ concentration in the second half decreased the adsorption rate in catalyst surface. The increasing ammonia/nitrogen ratio (ANR) and the decreasing space velocity (SV) also strengthened the SCR catalytic efficiency. The NO₂/NO_x range during 40 ~ 60% further promoted the catalytic progress due to the dominant role of fast SCR reactions on the catalyst surface. Interestingly, the aging sample B exhibited stronger catalytic and adsorption activities than fresh sample (at the temperature of 600 °C and WVC of 10 V%). It meant that moderate degree of hydrothermal aging could unblock partial molecular sieve pores and optimize physicochemical parameters. The research results can provide theoretical guidance for developing high-efficiency and long-life cycle catalysts with strong resistance to hydrothermal aging.

Active phase constitution directly affects catalytic performance. As a support, niobia (Nb₂O₅) provides high specific surface area and acidity, apart from being vastly available in Brazil. Hemicellulose-derived furfural can be hydrogenated in metallic sites producing furfuryl alcohol, which might react in acid sites forming industrially value-added products. Thus, this work studies the cascade reactions of furfural conversion with different bifunctional niobia-supported metal catalysts. Catalysts Ni, Cu, Pd and Ru/Nb₂O₅ were synthesized using wet impregnation, and base metals were reduced under H₂ flow, while noble metals were reduced by formaldehyde. Batch reaction conditions were 5 MPa of H₂, 423 K, and solvent 2-propanol. Characterization tests include N₂ physisorption, EDS, XRD, TPR, TPD-NH₃ and XPS. Difurfuryl ether was formed in all reactions, especially with Ni. Conversely, Cu showed high selectivity to furfuryl alcohol (100% in the first hour), despite its low activity. Pd and Ru provided 100% furfural conversion, but while Pd/Nb₂O₅ showed increasing selectivity to tetrahydrofurfuryl alcohol over time, Ru/Nb₂O₅ selectively formed furfuryl alcohol in the first 2 h (80%), then produced tetrahydrofurfuryl alcohol and difurfuryl ether. Thus, we provide useful insights to the design of a catalytic process based on the cascade conversion of furfural to furfuryl alcohol, tetrahydrofurfuryl alcohol and difurfuryl ether, which can be accomplished in biorefineries with bifunctional catalysts.

The present study was examining the remediation and elimination of Mayer’s Hematoxylin (MHX) solutions, a widely utilized dye in biochemical and biomedical laboratories, via adsorption process onto a naturally occurring clay mineral (NC) explored as a cost-effective and efficient adsorbent. Natural clay (NC) were characterized its properties through SEM, EDX, XRD, BET, FTIR, and TG&DTG techniques to identify active sites and structural characteristics. The treatment of MHX, especially at pH 3.5, presents notable challenges owing to the stability in aqueous solutions. The adsorption isotherms were assessed through Langmuir and the Freundlich isotherm models. The Langmuir model exhibited the superior fit (R² = 0.98) and suggested a maximum adsorption capacity of 17.5 mg g⁻¹. Kinetic studies indicated that the pseudo-first-order model accurately represented the adsorption process, attaining the R² value of (0.98). Batch adsorption experiments confirmed the effectiveness of NC in treating laboratory wastewater containing Mayer’s Hematoxylin. The findings of NC demonstrate the efficacy of palygorskite clay as a sustainable adsorbent for treating medical and laboratory effluents, presenting a viable approach to address environmental and wastewater management issues. The uniqueness of this study is to use natural clay as an adsorbent to eliminate MHX dye. Finally, Natural clay (NC) showed high efficiency in treating real wastewater samples from diagnostic laboratories in health sectors, suggesting a potentially cost-effective and sustainable alternative to conventional treatment methods for medical facility waste management.

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