Reaction Kinetics, Mechanisms and Catalysis最新文献

This study explores the utilization of asphaltene an undesirable and abundant waste from an Algerian crude oil well, for activated carbon production via physical activation methods using two distinct activating agents: carbon dioxide and steam, at 780 °C, with varying degrees of burn-off. The carbons produced at different burn-off levels were characterized based on their nitrogen and carbon dioxide adsorption isotherms at 77 K and 273 K. The results indicate that the choice of gasification agent significantly influences the development of activated carbon porosity. Specifically, steam demonstrates higher reactivity and generally yields activated carbons with superior nitrogen adsorption capacity. Carbon dioxide activation, on the other hand, generates narrow micropores that contribute to total microporosity, while steam activation tends to widen micropores. The adsorption capacity of the resulting activated carbons (CAs) was assessed using ibuprofen as the adsorbate. Kinetic and equilibrium adsorption data indicate satisfactory removal of this contaminant. The adsorption process conforms to the pseudo-second order kinetic equation and the Sips and Langmuir adsorption models, highlighting the efficiency and reliability of the adsorption process.

A solvent-free metal–organic framework (MOF) [Cu₃(CN)₃(dtb)]_n (1) was hydrothermally constructed depending on 4,4′-di(4H-1,2,4-triazol-4-yl)-1,1′-biphenyl (dtb) and structural characterization was carried out through single crystal X-ray diffraction analysis. Compound 1 reveals an interpenetrated three-dimensional (3D) framework architecture by Cu6(CN)6 rings and dtb ligands, resulting in a fascinating configuration. 1 displays very high thermal stability with the thermal decomposition temperature up to 301 °C and the research on non-isothermal kinetics was conducted at different heating rates through adopting Kissinger’s and Ozawa-Doyle’s methods. Remarkably, the kinetic triplets (the apparent activation energy E_a, the preexponential factor logA and the mechanism function ƒ(α)) and the related thermodynamic parameters (the Gibbs energy of activation ∆G^≠, the enthalpy of activation ∆H^≠ and the entropy of activation ∆S^≠) are discussed and calculated in detail.

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A solvent-free 3D MOF based on 4,4′-di(4H-1,2,4-triazol-4-yl)-1,1′-biphenyl presents high thermal stability and its thermal decomposition kinetics was investigated.

In this work, the isothermal decomposition kinetics of a promising high-energy dense nitrated cellulose carbamate (NCC) was investigated, for the first time, using vacuum stability test (VST) at different isothermal temperatures. The kinetic triplet of NCC was calculated by model-fitting and model-free methods, and compared to that of the conventional nitrocellulose (NC). VST results showed that the gas pressure of the studied energetic cellulose-rich materials (NCC and NC) increased with the increase in time test, which is found more pronounced for NCC compared to NC. Furthermore, thermo-kinetic findings demonstrated that the Arrhenius parameters determined by the two performed kinetic approaches are in good concordance. Indeed, the apparent activation energy of NCC is found to be around 141 kJ/mol, which is lower than that of the common NC (Eα = 152 kJ/mol). The model-fitting approach revealed that the mechanism of isothermal decomposition of NCC and NC is controlled by a chemical process. Besides, a strong linear relationship between the activation energy and the logarithm of the pre-exponential factor is observed. This work provides valuable guidance for the isothermal decomposition kinetics of energetic cellulose-rich materials and further supports and complements their kinetic database.

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In a previous work, a cellulose paper film containing a nanocomposite charge (TiO₂/5%-curcumin) was developed and used in the photocatalytic degradation of methylene blue (MB), an organic dye, on a tubular reactor with trickling and circular flow under UV irradiation light. The effect of three main operational parameters on the photocatalytic degradation of MB was studied: the mass of TiO₂/5% Curcumin material deposited on the cellulose paper, the initial concentration of the pollutant (MB) and the intensity of UV irradiation light. The obtained results show that by working under operating conditions of mass of deposited material (14 mg), initial pollutant concentration (10 ppm) and intensity of UV irradiation light (3.76 w/cm²), approximately 85% of MB was removed after 220 min of irradiation. To help guide future experimental efforts, the present work proposes a data augmenting self-attention network (DASAN) for the prediction of the photocatalytic degradation efficiency from a set of experimental parameters. The suggested ensemble combines base models for data augmentation and a meta model incorporating a self-attention mechanism for the prediction. The model is trained using the obtained experimental data of operating conditions (mass of material, initial pollutant concentration and intensity of UV irradiation light). The base models achieved excellent fits to the data and the meta model attained a mean squared error of 0.0055 through five-fold cross-validation, predicting optimal degradation efficiencies of 86–90% for experimental values of 20–22 mg the catalyst charge, 11–15 ppm for the initial pollutant concentration and 4.4–5.7 w/cm² for the intensity of UV irradiation light.

Large-size 2D TiO₂ was prepared by hydrothermal method, then N doping was carried out ultrasound-assisted methods were utilized to successfully prepare N-TiO₂/MoS₂ composites for simulating the degradation of rhodamine B (RhB) under sunlight. The degradation rate of RhB by N-TiO₂/MoS₂ was as high as 92%, which was 40% higher than the 2D N-TiO₂ and 59% higher than that of TiO₂. N doping TiO₂ can effectively improve the response to visible light and regulate its conduction band, with MoS₂ to construct a new type of S-scheme heterojunction photocatalysts, which promotes the separation and transfer of carriers, and at the meantime, crushed MoS₂ exposes more active sites. So the performance of photocatalytic degradation was improved. This work constructs the efficient semiconductor photocatalytic nano-heterostructures which is important for the surface modification of defective TiO₂ to improve the degradation of photocatalysts. It also introduces a novel approach to the straightforward synthesis with fresh powerful photocatalysts.

In this work, a series of bimetallic nano-oxide ZrO₂–CeO₂ xerogel adsorbent with different Ce/Zr molar ratio (0.1, 0.2, 0.3 and 0.5) were prepared in one step via sol–gel method in order to obtain the highest-performing composition for fluoride removal from drinking water. BET, SEM, EDX, TEM, FTIR spectroscopy, and XRD techniques were performed to characterize the solids before and after fluoride adsorption. The selected material exhibits a high surface area (S_BET = 255 m² g⁻¹) and a large porosity (V_P = 0.30 cm³ g⁻¹). FTIR spectroscopy demonstrated the significant role played by the adjunct sulfate anion and superficial hydroxyl groups in the defluorination process. Thermodynamic study confirms that the sorption is spontaneous and endothermic. Our adsorbent's behavior for the removal of fluoride is described by the Freundlich isotherm model. The pseudo-second order kinetic model represents the adsorption kinetic process. Less than 1 min, 100% of fluoride removal is reached in a wide pH range (2–8). The results of this study were effectively applied to natural drinking water in Tunisia. The development of innovative water treatment technology can be effectively advanced by using our multifunctional nano-oxide.

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This study aims to investigate the atmospheric water sorption kinetics of a CaCl₂ salt-impregnated sorbent derived from waste sugarcane biomass under real-time semi-arid to semi-humid conditions. The samples prepared by impregnating highly porous activated carbon prepared from waste sugarcane bagasse in different salt concentrations of CaCl₂ was initially screened based on its water uptake and sorption kinetics. Subsequently, the screened sorbent underwent further characterization to assess its textural properties, surface morphology, thermal stability, functional groups, and density. Under low relative humidity (RH) conditions ranging from 30 to 50%, the sorbent exhibited commendable water uptake ranging between 0.71 and 0.95 g/g, coupled with rapid adsorption and desorption kinetics. The sorbent also demonstrated operational stability over 10 adsorption–desorption cycles. The experimental water uptake data was also fitted using the Linear Driving Force (LDF) model to determine the sorption rate constant and resulted in a very good agreement with the model. Furthermore, at 60 °C, more than 80% desorption was attained, indicating the feasibility of solar-assisted operation. This study highlights the potential of sorbents derived from waste biomass for sustainable AWH applications.

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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