Reaction Kinetics, Mechanisms and Catalysis最新文献

In this study, the effect of lanthanum (La) as a promoter on the metal–acid balance and catalytic performance of Pt–Sn/Al₂O₃ catalysts for naphtha reforming was systematically investigated. The effects of different La loadings on the structure and performance of the catalyst were investigated using characterization methods such as XRD, NH₃-TPD, H₂-TPR, and XPS. The introduction of La was found to preferentially anchor on the Al₂O₃ surface, enhancing the dispersion of Pt. Optimal La loading (0.5 wt%) significantly improved the catalyst’s low-temperature reduction ability and NH₃ desorption properties, leading to enhanced catalytic performance in naphtha reforming. The modified catalyst improved selectivity towards isomerization and aromatization, while suppressing undesirable cracking reactions. The study revealed that La promotes Pt dispersion and adjusts the metal active sites-acid sites balance, with an optimal ratio of 1/35 (Pt active sites to acid sites) yielding the highest C₅₊ product yield (86.4%). This work demonstrates that La-modified Pt–Sn/Al₂O₃ catalysts offer a promising approach for improving naphtha reforming efficiency, with potential applications in industrial catalytic processes.

In this study, we successfully introduced NiCl₂ and CoCl₂ into hydrazine borane (N₂H₄BH₃, HB) via a solution mixing method, synthesizing a series of transition metal doped materials with varying weight fractions. Under open-system conditions, 15 wt% NiCl₂ doped N₂H₄BH₃ exhibited a remarkable reduction in activation energy from 107.0 (pristine HB) to 47.1 kJ mol⁻¹, along with a substantial decrease in the pre-exponential factor from 2.91 × 10¹³ to 9.92 × 10⁵ min⁻¹. In contrast, 5 wt% CoCl₂ doped N₂H₄BH₃ showed an increase in activation energy to 125.7 kJ mol⁻¹, while the pre-exponential factor increased significantly to 1.10 × 10¹⁶ min⁻¹, which may indicate an altered reaction mechanism. More notably, in a closed system, the decomposition of 15 wt% NiCl₂ doped N₂H₄BH₃ occurred rapidly at temperatures as low as 97 °C, releasing 10.6 wt% of H₂ at 200 °C. Despite the activation energy in the closed system being slightly higher (53.8 kJ mol⁻¹) than that in the open system (47.1 kJ mol⁻¹), the pre-exponential factor increased by more than 2 order of magnitude (from 9.92 × 10⁵ to 1.16 × 10⁷ min⁻¹), suggesting a different and more favorable decomposition pathway under confined conditions. Characterization results indicate that the formation of Ni–B species may be responsible for the enhanced catalytic behavior, enabling significant reductions in both activation energy and decomposition temperature of N₂H₄BH₃, especially under closed-system conditions.

The denitrification performance of 2%Fe/X zeolite and Mn-2%Fe/X zeolite was investigated by hydrothermal synthesis of X zeolite without templating agent using alkali fusion-activated rare-earth tailings and fly ash as raw materials instead of pure chemical reagents, and the Mn-Fe co-loaded Mn-Fe/X zeolite was prepared by impregnation method. The denitrification activity results showed that the 2%Fe/X zeolite reached an optimum denitrification efficiency of 67% at 400 °C. The addition of Mn makes the activity shifted to lower temperatures. The denitrification efficiency of the 8%Mn-2%Fe/X zeolite catalyst at 250 °C was 97%. The characterization results showed that the Fe element in the rare earth tailings entered into the X zeolite in the form of Fe³⁺, which enabled it to maintain excellent denitrification activity even at medium and high temperatures. After the introduction of Mn, there was a synergistic effect between Mn and Fe, which resulted in a shift in the binding energy of Fe³⁺ and a decrease in the density of the surrounding electron cloud. The high concentration of Mn⁴⁺ and Mn³⁺ improved the low-temperature oxidation performance, and increased the number of acidic sites and adsorbed oxygen on the surface, which led to a better denitrification activity for the 8%Mn-2%Fe/X zeolite catalysts.

Zeolitic niobium oxide is synthesized successfully, the surface of which is modified by sulfate functionalization with sulfuric acid. The sulfonated zeolitic niobium oxides act as solid acid catalysts for conversion of glucose to 5-hydroxymethylfurfural in aqueous solution at 150 °C for 4 h, and 47% of glucose conversion, 35% of selectivity to 5-hydroxymethylfurfural, 16.5% of yield to 5-hydroxymethylfurfural are obtained, which is higher than the other niobium oxide-based catalysts. The reaction conditions for obtaining 5-hydroxymethylfurfural, including temperature, time, catalyst dosage, and reactant concentration, are investigated in detail. The catalyst is able to be reused for 3 times without loss of activity, which demonstrates that the catalyst is stable during the catalytic reaction.

In this study, ZnO Nano-particles (ZnO NPs) were synthesized by green chemistry using an aqueous extract of Salvia Verbenaca leaves (S. Verbenaca) for the first time. The as-prepared ZnO NPs were characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), UV–Vis spectroscopy, FT-IR spectroscopy, thermo gravimetry (TG) and BET analysis. The diffractogram confirmed the hexagonal structure of ZnO NPs with crystallite size of 50 nm, while the SEM image revealed that the particles are agglomerated with a spherical shape. The optical properties of ZnO NPs were studied and the band gap (3.01 eV) was determined from the diffuse reflectance. The FT-IR spectra indicated the presence of biomolecules from the plant extract acting as capping agent. The TG analysis indicated the formation of ZnO NPs and BET analysis, confirmed the formation of a mesoporous NPs. The photocatalytic activity of ZnO NPs was evaluated through the degradation of Basic Fuchsine (BF), a hazardous dye under solar irradiation. This study was undertaken by varying the physical parameters namely the initial concentration of the dye (C_o: 5–50 ppm), the catalyst dose (10–45 mg) the extract dose (5–15 g/L). The results show that the best abatement was obtained for the initial concentration of 10 mg/L and 45 mg of ZnO NPs. More interestingly, we also prepared the hetero-junction (90% ZnO–10% CuO) and a degradation yield of 90% was reached after 90 min under sunlight. The stability test shows that the product maintains its effectiveness after 4 successive cycles as checked by FT-IR spectroscopy. The oxidation state of Zn was investigated by XPS analysis and the elements Zn and O are indicated by the surface survey spectrum. The photoluminescence shows strong emission at 528 nm, associated to surface defects on the nanoparticles. Additionally, ZnO NPs exhibited potent antibacterial activity against both Gram (positive–negative) bacteria, with a higher effectiveness observed for Gram-positive strains. This work highlights the potential of S. Verbenaca-mediated ZnO NPs as an eco-friendly solution for environmental remediation and antimicrobial applications.

In this research, manganese ferrite MnFe₂O₄ spinel was synthesized using the sol–gel method and characterized to explore its structural, surface, and photocatalytic properties. X-rays diffraction (XRD) analysis confirmed the successful formation of the MnFe₂O₄ spinel phase at 950 °C without the presence of secondary phases. The surface properties of the material, investigated through Brunauer–Emmett–Teller (BET) analysis, revealed a specific surface area of 15.633 m²/g. Optical characterization using the Tauc plot demonstrated that the synthesized powder exhibits semiconducting behavior, with an energy bandgap (Eg) of 2.64 eV. The photocatalytic performance of MnFe₂O₄ was evaluated for the degradation of Methylene Blue (MB), Crystal Violet (CV), and Neutral Red (NR) dyes under solar irradiation, showing that the material acts as an effective photocatalyst for water treatment applications where the removal effectiveness surpassing 95% for each dye.

The current work involves the synthesis of a composite of carbon nanotubes and kaolinite (CNTs/kaolinite). This composite was synthesized using a simple evaporation and drying method. The synthesized materials were investigated using different techniques such as the XRD technique, SEM–EDS, Sears method, and point zero charges (pzc). The activity of synthesized materials was studied by following the removal of methyl red dye (MR) from its aqueous solution by adsorption over these synthesized materials. Different adsorption parameters and conditions were conducted such as the effect of the used doses of the adsorbent, period of adsorption, effect of temperature, and pH effect. The obtained results found that the best removal efficiency of MR dye was achieved upon using a dose (0.07 g) of the synthesized composite at 25 °C, and the optimum pH was 5. Also, it was found that the removal efficiency of this dye over composite was better than that in comparison with each of kaolinite and CNTs alone under the same adsorption circumstances. The adsorption behavior of MR dye onto the CNTs/kaolinite composite is well described by the Freundlich isotherm and follows the pseudo-second order kinetic model. Additionally, the data indicates that CNTs/kaolinite are highly recyclable, indicating that they would be a cost-effective material with substantial potential for water treatment.

An Fe₂O₃-functionalized brown algae-derived activated carbon (BAAC/Fe₂O₃) nanocomposite was synthesized and evaluated for its efficacy in the adsorption of methylene blue (MB) from aqueous media. The composite was prepared through chemical activation of brown algae biomass with KOH, followed by sol–gel-assisted deposition of Fe₂O₃ nanoparticles. Structural and surface characterizations performed using SEM–EDX, FTIR, and BET analyses confirmed the successful incorporation of Fe₂O₃ and revealed a high specific surface area of 720 m²/g with an average pore size of 1.82 nm. Batch adsorption experiments demonstrated that BAAC/Fe₂O₃ achieved a maximum MB removal efficiency of 71.19% under optimized conditions (1 g adsorbent, 120 min contact time). The incorporation of Fe₂O₃ not only enhanced adsorption capacity through increased active surface sites but also imparted magnetic properties that enable facile separation and potential reusability. The findings establish BAAC/Fe₂O₃ as a promising, sustainable, and cost-effective adsorbent for dye removal in controlled aqueous environments, with potential applicability to industrial wastewater pending further validation under complex real-world conditions.

In the present work, the corrosion rate of inner-side boiler tubes was experimentally investigated by weight loss technique. Corrosion rates were evaluated as a function of NaCl concentration, temperature, and pressure. Three variables with four levels for each variable factorial experimental design (64 runs) were used for the regression process, while two variables with four levels for each variable design (16 runs) were used for the validation process. It was found that the corrosion rate increased with the increase of these variables. The maximum corrosion rate value was 6.03 g/m² day at 1000 ppm, 140 °C, and 5 bar. Two groups of models were proposed: Kinetics and mathematical models. In the first group, the kinetic-exponent model was better than the kinetic model with a higher correlation coefficient. According to the value of the exponent, the effect of NaCl concentration and temperature was higher than the pressure. In the second group, the quadratic model was better than the linear and linear with interaction model. Again, the coefficients of NaCl concentration and temperature were more significant than the pressure. In the validation process, the deviation from experimental data was observed at elevated values of temperature and NaCl concentration. The mean absolute percentage error of the kinetic-exponent model and quadratic model were 19.5% and 29.5%.

This study explores the synthesis, characterization, and application of CuFe₂O₄ nanoparticles as an efficient photocatalyst for the degradation of Rhodamine B (RhB) under visible light. CuFe₂O₄ was synthesized via the coprecipitation method, and its structural integrity and purity were confirmed through X-ray diffraction (XRD) and Raman spectroscopy, which identified a spinel cubic phase with high crystallinity. Scanning Electron Microscopy (SEM) revealed agglomerated nanoparticles, while Energy-Dispersive X-ray Spectroscopy (EDX) verified the elemental composition and purity of the material. Optical characterization using UV–Vis diffuse reflectance spectroscopy and the Tauc plot demonstrated a narrow bandgap of 1.43 eV, enabling strong absorption of visible light, while the Valence Band Maximum (VBM) at 1.94 eV highlighted its high oxidative potential. Electrochemical impedance spectroscopy (EIS) and Nyquist plots showed low charge transfer resistance, facilitating efficient charge separation, and photoluminescence (PL) spectra revealed moderate emission intensities, indicating reduced electron–hole recombination. Dielectric studies further confirmed strong light-matter interactions, with favorable optical and electrical conductivities for photocatalytic applications. The photocatalytic activity of CuFe₂O₄ was evaluated for RhB degradation, achieving a significant degradation rate of 57.89% within 90 min under visible light, following pseudo-first order kinetics with a rate constant (k = 0.01961 ± 0.0027 min⁻¹) much higher than photolysis alone (k = (7.2 ± 0.1) × 10⁻⁴ min⁻¹). Reusability tests confirmed the catalyst's stability over six cycles, with a degradation efficiency of 46% in the final cycle. Scavenger tests identified superoxide radicals (O₂⋅⁻) as the dominant reactive species, with significant contributions from photogenerated holes (h⁺), while hydroxyl radicals (⋅OH) played a negligible role. A detailed mechanism was proposed, involving visible-light absorption, charge carrier generation, and reactive oxygen species formation to degrade RhB into harmless products.