Reaction Kinetics, Mechanisms and Catalysis最新文献

Bismuth chromate nanostructures were fabricated via hydrolysis technique using curcuma longa for enhancing the photocatalytic activity. The analytes have been labelled as Bi₂CrO₆-C, when prepared without using curcuma longa and Bi₂CrO₆-G, prepared using curcuma longa extract (Bi₂CrO₆/Curcuma longa). The as-fabricated catalysts have been confirmed via characterization techniques including X-ray diffraction, Transmission electron microscopy (TEM), and Field emission scanning electron microscopy (FESEM), UV–Vis. DRS. The as-synthesised analytes have been evaluated their photocatalytic efficiency via photodegradation of an organic pollutant, Methyl Orange (MO). The current research findings imposed the effect of inculcation of a green extract “curcuma longa” reduces particle size and increases surface area of the material and moreover makes heterostructure with Bismuth chromate and inhibits recombination of photogenerated charges for efficient degradation of the organic pollutant. Bi₂CrO₆-G demonstrates here enhanced photocatalytic activity as compared to Bi₂CrO₆-C.

This study explores oxidative coupling of para-aniline derivatives, including (p-methylthio aniline, p-methyl aniline, p-methoxy aniline, p-hydroxy aniline and p-amino aniline). The study investigates the influence of substituents on the kinetics, thermodynamics and stability constants of the resulting compounds. A number of hybrid exchange–correlation functionals, namely, B3LYP, PBE0, BMK, CAM-B3LYP, M06-2X, HSE06 and BH&HLYP with a number of basis sets, namely, STO-3G, 3-21G, 6-31G, 6-31G*, DGDZVP, 6-311G, LanL2MB, LanL2DZ and SDD have been employed to calculate the electronic spectra of all the products. The results are compared with available experimental data. In most cases studied, the density functional theory results based on the B3LYP functionals with the DGDZVP basis set indicate a better agreement with the experimental absorption bands in the UV–Visible and IR spectra. The study reveals a first order reaction model with rate constants (0.06433–0.09053 min⁻¹) across temperatures for the product of aniline and p-amino aniline. Characterization of the compounds involves experimental and computational techniques such as FTIR and UV–Visible spectrophotometries. Activation energy (E_a) and pre-exponential factor (A) ranging (6.679–9.337 kJ mol⁻¹) and (1.2839–2.809 min⁻¹), with the highest values observed for the product of p-hydroxy aniline. Stability constants increase with temperature indicating an endothermic reaction. Thermodynamic analysis unveiled values for activation parameters: entropy (ΔS* = −0.2513 to −0.2447 kJ mol⁻¹ K⁻¹), enthalpy (ΔH* = 4.168–6.826 kJ mol⁻¹) for the product of p-hydroxy aniline and aniline; and Gibbs free energy (ΔG* = 80.1856–81.0466 kJ mol⁻¹) for the product of p-amino aniline and aniline. ΔG* values indicate a non-spontaneous and endothermic processes. Computational investigations using density functional theory (DFT) with the B3LYP/DGDZVP basis set, authorize reliability and accuracy of the experimental results.

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This study effectively synthesized monoclinic bismuth oxide nano-photocatalyst (α-Bi₂O₃) using both template-assisted and template-free methods, employing the hydrothermal process. Xanthan gum, a type of soft biopolymeric material, was used as a sacrificial template to promote the regulated growth of nano-photocatalysts. The structure, morphology, surface features, optical properties, and catalytic activity of both templated and non-templated Bi₂O₃ were analyzed using XRD, FESEM-EDX, IR, and UV–Vis (DRS) spectral analysis techniques. Additionally, the chemical oxygen (COD) analyzer methodology was used to assess the catalytic activity. The combination of synthetic technique and template has successfully produced Bi₂O₃ nano-photocatalyst with a consistent and granular shape. Specifically, the template-assisted processes have produced nanostructures of bismuth oxide that are highly crystalline and low band gap (2.76–2.71 eV). The use of template-assisted metal oxide nanostructures has shown potential as very effective photocatalysts for breaking down developing pollutants, such as 2,4-dichlorophenol (2,4-DCP), which is found in paper and pulp mills, when exposed to sunlight. The xanthan gum templated α-Bi₂O₃ nano-photocatalyst almost completely photodegraded 2,4-DCP within 90 min under sunlight. The remarkable catalytic capability of bismuth oxide (Bi₂O₃) templated by xanthan gum has been confirmed by their high-rate constants of 0.01–0.05 min⁻¹. As the treatment duration increased to 90 min, the degradation of 2,4-DCP resulted in a maximum elimination rate of 97.5% for COD. As a result, the template-assisted approaches have successfully produced nanostructures with customized features, which makes them very efficient in photocatalysis for quickly breaking down certain emergent organic pollutants present in paper and pulp mill wastewater. These eco-friendly synthetic photocatalysts can be efficiently used for treating wastewater that is contaminated with emerging organic contaminants.

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This study reports the synthesis and characterization of Polyvinylidene Fluoride (PVDF)/TiO₂ composite nanofibers for photocatalytic CO₂ conversion. The nanofibers were fabricated via electrospinning, with TiO₂ supported in a PVDF matrix. The electrospinning parameters were optimized, with the speed of drum collector, voltage, flow rate, and temperature set at 321 rpm, 20 kV, 1 ml h⁻¹, and 24 °C. SEM and XRD analyses revealed a nanofiber width of approximately 250 nm and the presence of anatase phase TiO₂, with primary diffraction peaks at 2θ values of 38.24° and 48.62°. The PVDF/TiO₂–NFs sample exhibited a BET surface area of 17.2689 ± 1.1154 m² g⁻¹, a BJH adsorption pore volume of 0.025 cm³ g⁻¹, and a BJH pore diameter of 7.26 nm. The photocatalytic performance of PVDF/TiO₂ nanofibers was evaluated through CO₂ conversion experiments, measuring the production of solar fuels (methanol and ethanol) and the efficiency of carbon utilization. The obtained yield of methanol is at 15.66 μg L⁻¹, while ethanol is recovered at 19.15 μg L⁻¹. The results demonstrated significant CO₂ reduction capabilities, highlighting the potential of PVDF/TiO₂ nanofibers as a sustainable solution for environmental remediation and renewable energy generation.

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The purpose of this work was to establish a process model of a vacuum gas oil industrial hydrocracking. In this model, we divide the lumps by 10 K as the interval, the reaction kinetics model is established based on discrete lumping method. Besides, a relevant catalyst deactivation function for catalyst activity calculation was proposed, which includes the flow and properties of the feed for a long period. The simulated hydrocracking unit is the process with hydrotreating and hydrocracking reactors in series. Therefore, it is necessary to build a hydrotreating model to represent the feed oil properties at the inlet of the hydrocracking reactor. Owing to absence industrial hydrotreating reactor monitor data, the hydrotreating model is established by using the data of the pilot plant loaded with the same catalyst. The hydrocracking reactor model is established through the material balance, heat balance, and momentum balance equations. Multiple sets of data are used to verify the established hydrocracking reactor model, the errors between the calculated value and the actual value of hydrocracking products are basically less than 10 %, and the relative errors of the predicted temperature and pressure are less than 0.5 %. Based on the catalyst deactivation function, the average relative errors of the model can be reduced by 50%. The variation of the reactor along the height is analyzed, and the result shows that the model accuracy simulated the target hydrocracking unit.

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The present study attempts to decrease PM count from the exhaust gases by ionizing these particles. The ionized particles precipitate is collected in a collector tube and are separated from exhaust gases. The effect of turbulence in the smoke, ionizing electrode diameter, voltage and size of particles on the amount of PM precipitation has been studied. Three types of turbulators and four types of electrode thicknesses are studied. The swirl blade turbulator causes nearly 44.23% more precipitation than the swirl contour device. PM count reduced for all particle sizes with decrease in ionizing electrode thickness. The combination of swirl blade type turbulence device with minimum thickness electrode has shown the minimum PM_0.3 count. Maximum swirling has been generated in blade type turbulence due to that particulate matter quantity reduced sharply in significant manner.

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This study introduces a novel thermochemical conversion process to synthesize lignin-derived activated carbons (LEGHs) from sawdust, utilizing ethylene glycol (EG) as a liquefaction agent and phosphoric acid as an activating agent. The process was conducted at a 1:1 impregnation ratio, with temperatures ranging from 300 °C to 500 °C. The obtained materials were characterized using Scanning Electron Microscopy–Energy-Dispersive X-ray Spectroscopy (SEM–EDX), Fourier Transform Infrared Spectroscopy (FTIR), and nitrogen adsorption at 77 K. Optimal activation at 350 °C produced an activated carbon with a high surface area of 1230 m²/g and a micropore volume of 0.348 cm³/g. Adsorption tests for the removal of Basic Blue azo dye (BB9) were conducted in batch experiments mode to assess the influence of various parameters including pH, adsorbent dose, contact time, initial dye concentration, and temperature. The highest adsorption efficiency was obtained at pH 4, dose of 1 g/L and a contact time of 5 h, resulting in an adsorption capacity of 668 mg/g. The Langmuir isotherm model best described the adsorption equilibrium data (R² = 0.99), indicating adsorption on a homogeneous surface. The adsorption kinetics study well fitted by the pseudo-second-order model (R² = 0.99). Thermodynamic studies showed a spontaneous (ΔG°: −45.73 to −50.34 kJ/mol) and endothermic (ΔH° = 196 kJ/mol) adsorption process These findings underscore the potential of LEGHs as an effective and sustainable adsorbent for industrial wastewater dye removal, leveraging lignin, a byproduct of the paper and pulp industry, to enhance sustainability.

In this article we present and discuss the work and scientific legacy of Julian Hirniak, the Ukrainian chemist and physicist who published two articles in 1908 and 1911 about periodic chemical reactions. Over the last 110+ years, his theoretical work has often been cited favorably in connection with Alfred Lotka’s theoretical model of an oscillating reaction system. Other authors have pointed out thermodynamic problems in Hirniak’s reaction scheme. Based on English translations of his 1908 Ukrainian and 1911 German articles, we show that Hirniak’s claim (that a cycle of inter-conversions of three chemical isomers in a closed reaction vessel can show damped periodic behavior) violates the Principle of Detailed Balance (i.e., the Second Law of Thermodynamics), and that Hirniak was aware of this Principle. We also discuss his results in relation to Lotka’s first model of damped oscillations in an open system of chemical reactions involving an auto-catalytic reaction operating far from equilibrium. Taking hints from both Hirniak and Lotka, we show that the mundane case of a kinase enzyme catalyzing the phosphorylation of a sugar can satisfy Hirniak’s conditions for damped oscillations to its steady state flux (i.e., the Michaelis–Menten rate law), but that the oscillations are so highly damped as to be unobservable. Finally, we examine historical and factual misunderstandings related to Julian Hirniak and his publications.