Reaction Kinetics, Mechanisms and Catalysis最新文献

This study aimed to enhance the adsorption performance of diatomite through iron doping and evaluate its efficiency in removing Rhodamine B (RhB) dye from aqueous solutions. The adsorbents were characterized using X-ray fluorescence (XRF), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), Fourier-transform infrared spectroscopy (FTIR), and point of zero charge (pHpzc) determination. XRF results indicated that raw diatomite was mainly composed of SiO₂ (61.29%) and CaO (15.22%), and iron incorporation increased Fe₂O₃ content from 2.72% to 8.59%. Batch adsorption experiments systematically examined the effects of pH, contact time, adsorbent dosage, and initial dye concentration. Optimal adsorption was observed at pH 3 for both adsorbents. Non-linear kinetic and isotherm modeling demonstrated that the pseudo-first order model best described the adsorption process, indicating diffusion-controlled mechanisms. Langmuir analysis revealed maximum adsorption capacities of 11.78 mg/g for raw diatomite and 19.94 mg/g for iron-doped diatomite, representing a 69% improvement. These results highlight iron-doped diatomite as a cost-effective and promising adsorbent for cationic dye removal in wastewater treatment applications.

This study investigates the in-situ hydrogenation upgrading of coal pyrolysis gas-phase tar using a nickel-based catalyst, examining the effects of Ni loading and the Si/Al ratio of HZSM-5 on catalytic performance, and employing deuterium isotope tracing to elucidate the reaction mechanism. The results showed that in the Ni/γ-Al₂O₃ catalyst, a Ni loading of 5 wt% achieved the optimal upgrading effect, with light aromatic hydrocarbon content reaching 61.68% and cycloalkane content at 9.58%; In the Ni/HZSM-5 catalyst, a Si/Al ratio of 50 exhibited the highest monocyclic aromatic hydrocarbon selectivity (41.62%, an increase of 38.2% compared to the None group) and the lowest polycyclic aromatic hydrocarbon content (21.74% for bicyclic and 8.72% for tricyclic). NH₃-TPD and elemental analysis indicated that increased acid content enhanced sulfur and nitrogen removal efficiency (35.8% and 29.5%), but excessive acidity reduced tar yield to 5.332 wt%. EA-IRMS results under deuterium atmosphere showed that the catalyst with a Si/Al ratio of 50 had the highest deuterium content of 1.745 mg/g, confirming that the synergistic effect between acidic sites and Ni active centers promotes the activation and incorporation of external hydrogen.

A novel nanocatalyst composed of platinum nanoparticles (Pt NPs), gum acacia polymer (GAP), and nanoscale ZnO was developed for the selective hydrogenation of nitroarenes to arylamines under mild conditions. In this hybrid system, Pt NPs act as the primary catalytic sites, GAP functions as a non-toxic and biocompatible reducing and stabilizing agent that ensures nanoparticle dispersion, and ZnO nanoparticles serve as a support that enhances catalytic efficiency and stability through electronic and structural interactions. The structural and compositional features of the nanocatalyst were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), field-emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). Results confirmed well-dispersed Pt NPs (4.62%) stabilized within the GAP matrix and a uniform distribution of ZnO nanoparticles, validating the successful integration of all components. The catalyst efficiently utilized molecular hydrogen for the reduction of nitroarenes, delivering excellent activity and selectivity. Notably, ~ 99% yield for nitrobenzene hydrogenation was achieved at room temperature in methanol within 3 h, while maintaining high performance over five reuse cycles. This environmentally benign strategy provides a sustainable platform for nitroarene hydrogenation, offering mild reaction conditions, high selectivity, recyclability, and significant potential for green catalytic applications.

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In this study, the influence of deep eutectic solvent (DES) pretreatment on the thermal degradation kinetics and thermodynamic behavior of three lignocellulosic wastes viz. corn stover (CS), peanut shell powder (PSP), and sugarcane bagasse (SCB) was explored. Choline chloride (ChCl) and glycerol based DESs were synthesized, and lignocellulose dissolution was performed under mild operating conditions. The thermogravimetric analysis (TGA) data was modeled using the Horowitz–Metzger method coupled with a range of reaction mechanisms to predict thermal activation energy (E) and thermodynamic parameters (∆H, ∆G, ∆S). The DES pretreatment substantially modified the lignocellulosic composition of all three materials promoting cellulose enrichment and removing lignin and hemicellulose from virgin material. These structural changes improved the thermal stability of the regenerated lignocellulosic fibers resulting in a marked increase in the values of activation energy, change in enthalpy (∆H) and change in Gibb’s free energy (∆G) of decomposition, with the most notable enhancements recorded for SCB.

The triple molybdate of silver, aluminum and cobalt nanoparticles was synthesized via a solid-state method. X-ray diffraction analysis (XRD) was used to confirm the phase purity. Fourier-transform infrared (FTIR) and Raman spectroscopies were identified as characteristics of bond vibrations. The morphology study using Scanning Electron Microscopy (SEM) revealed the presence of agglomerate in the prepared nanoparticles. The Brunauer–Emmett–Teller (BET) was employed to determine the surface area and pore radius. Vibrational spectroscopy based on IR and Raman techniques provided insights into active phonon vibration modes in MoO₄. The ultraviolet–visible (UV–Vis) spectroscopy showed that the considered molybdate present a large bond gap of about 3 eV, favorable to interesting photocatalytic activity. A novel Ag_0.9Al_1.06Co₂(MoO₄)₅ nanoparticles were prepared and tested for the degradation of two toxic azo dyes Acid Black-52 (AB-52) and Acid Yellow-23 (AY-23) under solar light. The considered catalyst showed a super photocatalytic activity reaching over 69% and 93% degradation for AB-52 and AY-23 dyes. The kinetic rate constants were 0.183 ± 0.009 h⁻¹ and 0.175 ± 0.031 h⁻¹ for AB-52 and AY-23 dyes. Additionally, the recyclability of the prepared catalyst was tested by using it for three successive cycles. Thus, the Ag_0.9Al_1.06Co₂(MoO₄)₅ heterogeneous catalyst demonstrated excellent photocatalytic efficiency for degrading hazardous pollutants, environmental remediation and remained reusable in cyclic tests.

Heterogeneous photocatalysis is an advanced oxidation technique widely explored for the selective conversion of benzyl alcohol (C₇H₈O) into benzaldehyde, an important intermediate in organic synthesis. This review critically examines the influence of key operational and morphological factors—including solvent choice, temperature, and light intensity—on photocatalytic performance. The synthesis method notably affects catalyst activity, with solvothermal preparation of TiO₂ significantly enhancing the reaction rate constant. Photo-deposition emerges as an effective alternative when both catalyst and support materials are available. Among various TiO₂ nanostructures (nanowires, nanotubes, nanofibers, nanosheets, and hollow nanospheres), hollow nanospheres exhibit superior photocatalytic activity due to improved light absorption and charge separation. Elevated light intensity and temperature further accelerate the reaction rate, resulting in higher rate constants. A range of catalysts—including C-ZnInS₄, ZnInS₄, Pt-TiO₂, RuO₂/TiO₂ nanobelts, 0.95Ru/3DOM BiVO₄-Ar-300, Pt/Bi₂MoO₆-glycerol, Ni-OTO₂, W₁₀O₃₂⁴⁻,WO₃(7.6)/TiO₂, TiO_1.966.N_0.034, and Bi₂WO₆—demonstrate promising rate constants of 75.0, 53.75, 57, 46.0, 38.0, 34.0, 33.25, 29.6, 28.0, 27.0 and 22.25 g_cat⁻¹ h⁻¹ for alcohol oxidation. Notably, TiO₂N_0.034 and ZnIn₂S₄ achieve 100% conversion with > 99% selectivity within 4 and 2 h, respectively, underscoring their excellent photocatalytic potential.

This study examined the photocatalytic degradation of Basic Red 46 (BR46) and Basic Violet 16 (BV16) dyes using the n-TiO₂-P25@ECH@ZrO₂-SO₃H catalyst in aqueous media. The effects of pH and LED light wavelength (blue and green) on dye removal were tested over 0–5 h. BV16 showed highest degradation under blue light and adsorption (43%) in basic media. Kinetic modeling revealed two-step first order reactions with rate constants k₁ = 0.0111 min⁻¹ and k₂ = 0.0134 min⁻¹. Maximum BV16 adsorption (74%) occurred under acidic conditions, though degradation was minimal. BR46 showed best removal (48%) under acidic pH media. The catalyst demonstrated dual functionality: effective BR46 adsorption in acidic media and strong photocatalytic and adsorptive removal of BV16. These findings suggest tailored applications of the catalyst based on wastewater pH for optimal dye elimination.

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This study investigates the structural, morphological, optical, thermoelectric, photodetector, and photocatalytic properties of ZnO, and W-doped ZnO [2, 5, and 10%] thin films deposited via spray pyrolysis at 450 °C. The X-ray diffraction (XRD) analysis confirms the hexagonal wurtzite structure, with improved crystallinity and reduced lattice parameters (a, c) due to W incorporation. Crystallite size increases from 32.4 nm (pure ZnO) to 39.2 nm (5% W-ZnO), while lattice strain decreases from 0.189 to 0.162%. Optical studies reveal a bandgap narrowing from 3.30 eV (ZnO) to 3.24 eV (10% W-ZnO), attributed to defect states and band tailing. The refractive index at 598 nm decreases from 1.78 (ZnO) to 1.68 (2% W-ZnO) but increases to 1.76 for 10% W-ZnO. Seebeck coefficient measurements show an initial decrease from − 321.9 μV/K (ZnO) to − 273.9 μV/K (5% W-ZnO), followed by an increase to − 348.7 μV/K (10% W-ZnO), indicating optimized carrier concentration. Photocurrent response analysis demonstrates that both 2 and 5% W-ZnO exhibit enhanced UV photoresponse, with 2% W-ZnO reaching the highest stable response of 140 mA, while 5% W-ZnO also delivers a significantly improved response compared to pure ZnO. Photocatalytic degradation of methylene blue (MB) reaches nearly 100% efficiency within 120 min for 2% W-ZnO, with a reaction rate constant of 0.02759 min⁻¹ and an R² value of 0.9987, confirming its superior photocatalytic activity. Notably, 5% W-ZnO also demonstrates high photocatalytic efficiency, slightly lower than 2% W-ZnO, which highlights that both 2 and 5% W doping levels are optimal depending on the targeted property. These findings indicate that W doping at optimal concentrations (2 and 5%) significantly enhances ZnO’s multifunctional performance for optoelectronic and environmental applications. The photocatalytic degradation behavior of pure ZnO, 2% W-ZnO, and 5% W-ZnO thin films under UV light was further investigated using scavenger experiments, which revealed that W doping enhances degradation efficiency, with hydroxyl and superoxide radicals playing dominant roles in the photodegradation mechanism.

This study systematically investigates the reduction mechanism of CoAl₂O₄ (100) catalyst in H₂-selective catalytic reduction (SCR) of NO_x using density functional theory (DFT) calculations. The results show that H atoms adsorbed on the three-coordinated oxygen atoms (O_3C) of the CoAl₂O₄ (100) surface exhibit the highest stability, thereby forming Lewis acid sites favorable for NO adsorption. On the CoAl₂O₄ (100) O_3C site pre-adsorbed with H, the dissociation barrier of NO is reduced to 0.43 eV, significantly lower than that on the H-free surface (1.54 eV). The analysis of H₂O and N₂ formation pathways reveals low adsorption energies, enabling easy desorption of products from the CoAl₂O₄ (100) surface. The formation and desorption of N₂O, a by-product, have high energy barriers, suggesting an extremely low probability of N₂O generation in SCR and good selectivity of the catalyst. Moreover, the CoAl₂O₄ (100) surface shows excellent water tolerance but poor tolerance to sulfur, providing crucial references for future optimization of CoAl₂O₄ catalysts.

Herein, we demonstrate that pristine Co-based ZIF-9 exhibits exceptional peroxidase-mimicking activity, catalyzing the oxidation of o-phenylenediamine as a model substrate in the presence of H₂O₂. The nanozyme shows a maximum reaction rate (V_max) of 3.66 ± 0.10 × 10^–5 (M/s) which is 10³-fold higher than horseradish peroxidase (HRP). A simple, rapid, and low-cost colorimetric sensor platform for the detection of H₂O₂ was also developed, demonstrating a linear range of 10⁻⁴ − 1.4 × 10^–3 M and a detection limit of 0.94 × 10⁻⁵ M (S/N = 3).