Reaction Kinetics, Mechanisms and Catalysis最新文献

In this study, we present a green synthesis approach for the fabrication of porous carbon supported palladium catalysts derived from Caesalpinia pods. The synthesis involves self-activation of Caesalpinia pods in a nitrogen atmosphere at various temperatures (600 °C, 800 °C, and 1000 °C) to produce porous carbon nanoparticles. Among the synthesized carbon materials, the sample CP-CNS/10 synthesized at 1000 °C exhibited the highest surface area of 793 m²/g with an average pore size diameter of 1.8 nm. The resulting porous carbon material served as an efficient support for palladium nanoparticles, with a low metal loading of about 0.2 mol% Pd for the reaction. This catalyst demonstrated excellent performance in the reduction of nitroarenes to their corresponding aromatic amines. The successful incorporation of approximately 4.5% Pd during the deposition process highlights the potential of the porous carbon supported palladium catalyst synthesized at 1000 °C for a sustainable and efficient heterogeneous catalyst for the reduction of nitroarenes.

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Synthesizing biogasoline from castor oil was catalyzed by Activated Natural Zeolite (ANZ) catalyst modified Ni and Zn metals in batch-cracking reactor. The process was affected by the modified catalyst on variation of Ni:Zn ratio (1:1, 1:2, and 2:1) at the calcination temperature of 500 °C, and variation of the calcination temperature (500, 600, and 700 °C) At Ni–Zn (1:1). After characterizations and analysis, the higher the calcination temperature, the lower the acidity of the catalyst caused the resulting yield also decreases. The density of the product obtained ranged from 0.765–0.83 g/mL, the viscosity ranged from 1.42–1.95, the refractive index was 1.421–1.431, and the calorific value tested on the cracking product with Ni:Zn (1:1) (500 °C) Fraction I, Fraction II, and Fraction III were 0.9966 kcal/kg, 0.9068 kcal/kg, and 0.8755 kcal/kg, respectively. The results of FTIR and GC–MS showed that the composition of the catalytic cracking product was composed of C₆–C₁₄ hydrocarbons consisting of aldehydes, alkanes, alkenes, and carboxylic acids. The composition was dominated by biogasoline compounds (C₅–C₁₂).

In this study, we meticulously analyzed the catalysis of azide-alkyne [3+2] cycloaddition reactions facilitated by metal-complexes with N, N-type ligands using MN12-L functional with Def2-TZVP/Def2-SVP basis sets. Specifically, the study contrasted mononuclear and binuclear mechanisms for silver (Ag) and copper (Cu) catalyzed reactions, employing ligands L1(2,2′-bipyridin), L2(1,10-phnanthroline) and L3(some derivative of 1,3-oxazole), under both gas phase and solvated conditions using toluene. Our results highlight that the binuclear mechanism is energetically favored over the mononuclear pathway, with activation energies for the former being notably lower. For instance, in the presence of toluene, the binuclear pathway for Cu-complexes with the L1 ligand demonstrated an activation energy of merely 2.3 kcal/mol, in stark contrast to the 11.8 kcal/mol required for the mononuclear process. This significant reduction in energy barrier elucidates the efficiency of binuclear complexes in facilitating [3+2] cycloaddition, potentially guiding the design of novel catalysts for synthetic chemistry applications. Furthermore, the study reveals that the transition state energies and the overall reaction energetics are critically dependent on the choice of metal and ligand, underscoring the complex interplay between metal coordination chemistry and catalytic performance in azide-alkyne cycloadditions. Analysis of computational results indicate that Cu-complexes with studied different ligands show higher activity compared to Ag-complexes in terms of energy barriers.

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In response to the pressing challenges in various fields, particularly healthcare and infection prevention, this research explores the synthesis, characterization, and assessment of ZnO–Ag nanocomposites for antibacterial properties. Employing a solvothermal method, silver nanoparticles were incorporated into hydrothermally synthesized zinc oxide nanorods, aiming to harness their synergistic antibacterial effects. The research systematically analyses the nanocomposites, unveiling their structural and compositional features. Antibacterial potential is evaluated through agar well diffusion assay, demonstrating increased efficacy against diverse bacteria. With implications extending to biomedical applications, these nanocomposites emerge as promising contenders for infection prevention in healthcare settings.

The impact of different concentrations of natural antioxidants (curcumin) on the thermal stability of UHMWPE (ultra-high molecular weight polyethylene) is examined via the thermogravimetric (TGA/DTA) technique, in the temperature region 50–600 °C at a 5 °C/min heating rate. This work employs the model fitting (Coats and Redfern) approach to determine the optimal curcumin concentration. UHMWPE samples at optimum concentration are further subjected to three other heating rates, viz., 10, 15 and 20 °C. A bi-Gaussian asymmetric function is utilized for deconvolution to elucidate the complexities of thermal decomposition. Through deconvolution, two peaks are obtained and the activation energy corresponding to each peak is determined through two iso-conversional kinetic (Friedman and Starink) models. By utilizing activation energy, the random nucleation reaction mechanism involved in thermal decomposition is recognized. Finally, changes in entropy (left(Delta Sright)), enthalpy (left(Delta Hright)) and Gibbs free energy (left(Delta Gright)) are determined.

This study investigates the potential of pomegranate peel (PP) as a raw material for synthesizing a novel biocatalyst metal oxide (BCMO) aimed at the efficient removal of methyl orange (MO) dye from aqueous solutions. The adsorption capacities of both PP and BCMO were systematically evaluated. PP was subjected to inorganic salt treatment and calcination to enhance its adsorption capacity and increase attractive forces at the nanoparticle level. The surface characteristics of the biocatalyst were thoroughly examined using FTIR, SEM, BET analysis, and EDX spectroscopy, revealing the development of a crystalline structure following treatment with Mg(NO₃)₂⋅6H₂O, along with observable changes in surface morphology and elemental composition. Under standard conditions, BCMO demonstrated a significant increase in efficiency, achieving 99.80% removal for 100 mg/L of methyl orange, compared to 44% for untreated PP at 50 mg/L. Kinetic analysis indicated a transition from pseudo-first-order to pseudo-second-order, signifying a shift from physical to chemical adsorption. This transition resulted in a substantial reduction in equilibrium time and a significant increase in maximum adsorption capacity from 17.3637 to 176.686 mg/g. Furthermore, the catalytic efficiency of BCMO was assessed over seven cycles, showing only a minor 5% reduction in efficiency, indicating its potential for practical applications. The environmental sustainability of the road was assessed using the AGREE and BAGI indicators, both of which are considered exemplary measures of environmental friendliness.

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A solvent-free, acid-free, and efficient strategy was developed for the selective preparation of 4-nitro-o-xylene (4-NOX) from the catalytic nitration of o-xylene with NO₂ mediated O₂ over BiCl₃ immobilized silicic acid catalyst (BiCl₃-SA). The results indicated that the Lewis acid BiCl₃-SA conjoined NO₂–O₂ as a composite system synergistically promotes o-xylene conversion and 4-NOX selectivity. Under optimal conditions, 52.4% of o-xylene conversion with 68.4% 4-NOX selectivity was obtained at 35 °C. The characterization demonstrated that the highly dispersed metal Bi species form stable chemical bonds with the SA surface, which can effectively inhibit the loss of metal species and generate abundant acid sites. The developed catalyst is not only inexpensive but also has excellent stability and catalytic performance. Furthermore, a plausible mechanism for the catalytic nitration of o-xylene using NO₂ as a nitration agent over BiCl₃-SA was proposed. This work provides an eco-friendly and practical protocol for improving desirable 4-NOX selectivity and reducing the discharge of acidic wastewater, with potential application prospects.

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Dissolution of a Nigerian antigorite-rich dolomite ore in methanesulfonic acid (MSA) solution for its optimal industrial application was investigated. The impact of the acid concentration, reaction temperature, particle diameter as well as reaction time on the rate of the ore dissolution was examined. The magnesium recovery was 97.2% at the optimal conditions: 2.5 mol/L MSA, solid/liquid 10 g/L, 56 µm in 2 h, and reaction temperature of 75 ºC. According to the shrinking core model, test results indicated that mass diffusion was the controlling step of the overall reaction kinetics. The activation energy of 11.26 kJ mol⁻¹ gives support to this assertion. The correlation coefficient value of (⁓0.98) indicates that the workability of the proposed kinetic model is highly effective or functional. At optimal conditions, a high-purity MgO product was obtained.