Reaction Kinetics, Mechanisms and Catalysis最新文献

This study proposed a surface reaction model (SRM) and a volume reaction model (VRM), which do not rely on the reaction model functions (f(α) functions) to determine the kinetic parameters of coal oxidation. Based on the results of thermogravimetric analysis experiments for coal oxidation under different oxygen concentrations (1-21%), the activation energy (E) and pre-exponential factor (A) in the kinetics-controlled regime were determined using SRM, VRM, and the traditional model-based method (MBM) with three selected f(α) functions. It was found that the selected f(α) functions have great influence on the E obtained by MBM, with an average variation of 24%. For SRM and VRM, the decreasing oxygen concentrations (from 21 to 3%) mainly reduces the reactivity of coal oxidation by decreasing A, that is, the active sites. Moreover, the reaction rates of coal oxidation in the kinetics-controlled regime were predicted. Compared with the traditional MBM, the proposed VRM and SRM demonstrate better predictive performance for the reaction rates. Of these, SRM is the optimal model in this study, achieving an average prediction error below 10%.

This study aims to determine whether a sustainable and cost-effective biochar can efficiently remove 2-nitrophenol (2-NP) from wastewater by evaluating its adsorption efficiency in batch and fixed-bed column systems under a range of operating circumstances. Results indicate that the presence of hydroxyl (-OH), carboxyl (-COOH), and aliphatic C-H bonds, according to the FTIR analysis, is crucial for the 2-NP adsorption process. The prepared biochar (PF600) exhibited heterogeneous architecture with tunnel-shaped pores and substantial porosity. The maximum adsorption capacity at 71.08 mg/g, with R² = 0.99 according to the Langmuir model, suggesting monolayer adsorption phenomenon. In the fixed-bed column system, the optimal adsorption conditions were achieved at a bed height of 4 cm, an influent concentration of 160 mg/L, and a flow rate of 2 mL/min, resulting in a removal efficiency of 65.46% and a bed capacity of 31.42 mg/g. Breakthrough curve modelling using the Yoon-Nelson and Thomas models demonstrated excellent fitting (R² > 0.99), confirming their applicability for dynamic adsorption predictions. The novelty in this study involves the application of biochar from date palm fiber as a green and economically viable alternative for the removal of 2-NP, showing competitive potential adsorption performance comparable to other conventional adsorbents. These results are illuminating with regard to the applicability of agricultural waste in water treatment practices from economic and environmental standpoints.

Graphical Abstract

Cold spray technology is applied for the first time to fabricate nickel electrodes for the hydrogen evolution reaction (HER). This solid-state deposition process accelerates Ni particles to supersonic velocities, consolidating them into dense, adherent, and binder-free coatings while preserving chemical purity and crystallinity. The resulting electrode presents a rough, textured morphology with an enlarged electrochemically active surface area, a highly crystalline fcc structure with preferential (111) orientation, and a favorable Ni/NiO heterointerface that enhances electron transfer and water dissociation. Electrochemical testing in alkaline medium demonstrates excellent performance, with a low onset potential of –0.32 V vs. RHE, high current density (–120 mA cm⁻² at –1.0 V), a Tafel slope of ~ 122 mV dec⁻¹, and an exchange current density of 1.64 mA cm⁻². Electrochemical impedance spectroscopy indicates moderate charge-transfer resistance with efficient ionic diffusion, while hydrogen quantification confirms a stable production rate of 472 µmol h⁻¹. These results demonstrate that cold spraying offers a scalable and environmentally friendly route for producing high-performance Ni electrodes for alkaline water electrolysis.

Thermodynamic and kinetic study of Ru(II)-Pt(II) complexes with a semi-rigid linker 4’-pyridyl-2,2’:6’,2’’terpyridine (quarterpyridyl (qpy)) with biological nucleophiles was carried out under pseudo first-order conditions as a function of concentration and temperature using UV–visible spectrophotometer. The reactions proceeded via a single step following first-order kinetics with the pseudo first-order rate constant obeying the rate law; (k_{obs} = k_{2} left[ {Nu} right]). The study revealed that increase in the overall charges of the complexes is the key reason for the observed increase in the reactivity. Additionally, replacing the cis pyridyl group in Pt1 by Ru(III) polypyridyl to give Pt2 and Pt3 lowers the energy of the LUMO (π^*) orbitals and HOMO–LUMO energy gap which influences the reactivity to some extent. The two qpy groups in the trinuclar complex Pt3 only slightly increase the reactivity compared to Pt2. This is because the qpy groups are in orthogonal positions preventing π-electron communication; hence the two Pt(II) centers act independently. The marginal increase in reactivity is due to increased charge and extension of the π-surface. The observed activation parameters support an associative mode of substitution. Their observed lower reactivity towards classical model Platinum-biomolecule interaction than cisplatin revealed their moderate reactivity that makes them less interactive with biomolecules hence potentially less toxic, more effective and selective. Their increased charge makes them better soluble than cisplatin which potentially solves the solubility challenge. The higher binding ability towards 5’-GMP on introduction of the ruthenium polypyridyl moiety indicates their tendency to strongly bind DNA.

N-((5-chloropyridin-2-yl)carbamothioyl)thiophene-2-carboxamide (HL) ligand which is a novel thiourea derivative and its Ni(II), Co(II) and Cu(II) complexes were synthesized. Structural characterizations of all compounds were performed with FT-IR and ¹H-NMR techniques. Moreover, the thermal behaviors of all synthesized compounds were investigated by TG/DTA techniques. Thermal stability properties and degradation reactions of all compounds were determined The HL ligand and its Co(II) complex degrade in three consecutive stages.. However, the thermal decomposition reactions of the Ni(II) complex are completed in four consecutive stages. Besides, the degradation of the Cu(II) complex is completed in five consecutive stages. X-ray powder diffraction analysis was applied to the residues remaining as a result of the thermal degradation of the complexes and the residues were determined as Co₉S₈, Ni₃S₂ and Cu_1.96S. Apparent activation energy values of each degradation stages were calculated with using Flynn–Wall–Ozawa and Kissinger–Akahira–Sunose isoconversional methods. Graphs of change in activation energy with degradation ratio (α) were prepared and the results were interpreted.

N,N-Dimethyldodecylamine (DMA12) was used as a pore-forming agent to promote the porosity of low-density ZnTiO₃/ceramic hollow microspheres (ZnTiO₃(n)/CHM, n = volume (mL) of DMA12 in the precursor) synthesised via the sol–gel method. The surface of CHM was coated with a thin layer of ZnTiO₃. The bandgap energies of ZnTiO₃(0)/CHM, ZnTiO₃(1.5)/CHM, ZnTiO₃(2.5)/CHM and ZnTiO₃(4)/CHM were calculated as 3.59, 3.63, 3.65 and 3.60 eV, respectively. The porosity of ZnTiO₃(n)/CHM was enhanced by DMA12, increased in the sequence 0, 1.5, 4 and 2.5 mL of DMA12. The largest number of hydroxyl radicals were generated in the reaction involving ZnTiO₃(2.5)/CHM. A total of 20.8% of Acid Red 1 was degraded after 30 min of irradiation using ZnTiO₃(0)/CHM, while the degradation efficiency of ZnTiO₃(2.5)/CHM was 82.2% at the same time. ZnTiO₃(2.5)/CHM had a constant activity over five reaction cycles, and the degradation efficiencies were 82.2% and 80.8% in the first and the fifth cycles, respectively. The low-density ZnTiO₃(n)/CHM was prepared to facilitate the mixing of the photocatalyst and water, and to ensure a rapid separation of the photocatalyst from water.

The manuscript aims to presents a computationally efficient semi-analytical framework for modelling concentration profiles in fixed-bed catalytic reactors with electrochemical relevance, utilizing the Differential Transform Method (DTM). The governing system of nonlinear singular boundary value problems describing ethanol and acetaldehyde transformation processes in fixed bed catalytic reactor, poses significant challenges due to its coupled and nonlinear nature. DTM yields rapidly converging series solutions without the need for linearization, discretization, or iterative schemes by reformulating the equations into recursive relations. To demonstrate the predictive capability and accuracy of the suggested approach, a comparative study is done against numerical simulations and the Variational Iteration Method (VIM), showing excellent agreement. Residual error and convergence analysis guarantees the stability and accuracy of the DTM. The suggested semi analytical framework is not only computationally efficient but also offers new insights into mass transport and reaction mechanisms, making it a robust, promising tool for electrochemical reactor analysis, performance optimization, and design.

ZSM-11 zeolites were systematically synthesized by a simple two-stage crystallization method with TBABr and TBAF template respectively. The physical and chemical properties of the obtained samples were characterized by using XRD, FTIR, SEM, N₂ physical adsorption & desorption and NH₃-TPD. The effects of Br⁻ and F⁻ on the morphologies, structure, acidities as well as the catalytic performance of methanol to olefins (MTO) process were elaborately investigated. The findings suggested that the F⁻ anion facilitated the aggregation of nanocrystalline grains and a more refined MEL structure, thereby resulting in a larger BET surface, abundant mesopores and moderate acidity, which effectively improved diffusion ability and suppressed coke deposition. In contrast, the Br⁻ contributed to the morphology of rod-like crystals aggregation and the co-crystalline ZSM-11/5 zeolites. As a result, the ZSM-11 zeolite prepared with TBAF template exhibited significantly superior catalytic performance in MTO process with a longer lifetime and higher selectivity to propylene and butene, compared to the ZSM-11 synthesized using TBABr template.

In the context of this study, particular emphasis is placed on the identification of regularities in the influence of the number of amino groups and the particle size of functionalized silica, selected as a support for palladium nanoparticles, on the activity of the catalyst in the hydrogenation reaction of p-nitroaniline (p-NA). The study demonstrated that increasing the content of amino groups on the silica surface to achieve maximum activity necessitates the utilization of silica with a substantial particle size to ensure the maintenance of optimal distribution density of amino groups. This, in turn, enhances the activity of palladium in the liquid-phase hydrogenation of p-nitroaniline. A novel methodology for synthesizing core–shell particles of the Ni@SiO₂ type has been developed.

In this study, the influence of deposition potential on the morphology, microstructure, and hydrogen evolution reaction (HER) catalytic activities of Cu₂O nanostructures was investigated. These nanostructures were deposited on conductive FTO substrates via electrodeposition in a solution containing copper sulfate as a precursor at a temperature of 65 °C and pH ~ 12. X-ray diffraction (XRD) patterns showed that the Cu₂O nanostructures were polycrystalline in nature, with highly oriented cubic (111) crystallites. Scanning electron microscopy (SEM) images indicated that the morphology of the Cu₂O films changed from granular to cubic as the applied potential increased. The Mott-Schottky (M-S) curve showed that each of the films was a p-type semiconductor with a carrier density ranging from 1.99 × 10²⁰ to 8.99 × 10¹⁹ cm⁻³. These experiments also demonstrated that Cu₂O prepared at −0.4 V exhibited much greater catalytic activity compared to those prepared at higher potential (−0.5 and −0.6 V). In 0.1 M Na₂SO₄ solution, the thin film showed a lower overpotential of −368 mV and a smaller Tafel slope of 257 mV dec⁻¹. Electrochemical impedance spectroscopy also demonstrated that the Cu₂O thin film deposited at −0.4 V vs. Ag/AgCl had the largest electrochemically active surface area (ECSA) and double-layer capacitance (C_dl) which resulted in its outstanding HER performance. This work aims to assist in the development of Cu₂O beyond its intrinsic limitations for applications in the hydrogen evolution reaction.