Reaction Kinetics, Mechanisms and Catalysis最新文献

The carboxylic multi-walled carbon nanotube-loaded nickel (Ni/c-MWCNT) catalyst prepared by the excess impregnation method was used for the hydrogenation of oleoresin-based turpentine (OBT) into high energy density fuel. Benefiting from small nickel nanoparticle sizes (about 10 nm) and the carrier’s high surface area, a hydrogenation rate of 99.1% was achieved at 145 °C and 3 MPa, superior to a commercial 5 wt.% Pd/C. Hydrogenated oleoresin-based turpentine (HOBT) satisfied the density, flash point, and freezing point outlined by the American Society of Testing and Materials standard. Hydrogenation improved the oxidative stability, smoke point, and calorific value of OBT while changing its color to water white. The impact of blend ratio on the blended biomass fuel performance was evaluated by measuring the smoke point, density, kinematic viscosity, calorific value, freezing point, and flash point of biofuels blended with HOBT and exo-tetrahydrodicyclopentadiene (JP-10). When HOBT was blended up to 20% (v/v) with JP-10, the performance of blended biomass fuel was comparable to that of JP-10 and even superior at freezing temperatures.

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In this work, the definition of deactivation kinetic model (DKM) has been given under some assumptions and its features were illustrated through comparison with prior kinetic models such as DM (deactivation model), Langmuir rate equation, pseudo kinetic model and unreacted SCM (shrinking core model). DKM is based on fractional conversion of solid and concentration of fluid phase, which is one of the different kinetic models for the heterogeneous processes. DKM has no thermodynamic equilibrium quantities such as adsorption amount (q_e) unlike the previous pseudo-order models. Therefore, DKM can offer more accurate kinetic parameters than other models. Main equations of DKM can be solved by using Matlab functions such as “ODE” and “lsqnonlin”. This DKM is a semi-empirical and apparent kinetic model for fluid/solid heterogeneous processes and its kinetic equations can be used not only in heterogeneous reactions, but also in adsorption processes.

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In this research, three distinct ternary-nanothermites were subsequently integrated into double base propellant formulated with nitrocellulose (NC) and diethylene glycol dinitrate (DEGDN). These nanothermites consisted of magnesium and aluminum alloy (MgAl) as fuel and metal oxides (CuO, NiO, and TiO₂) acting as oxidizers. Experimental results demonstrated the uniform distribution of the three investigated nanothermites throughout the NC/DEGDN composite. DSC findings indicated a significant increase in the overall heat release of the NC/DEGDN double base propellant upon the addition of the three nanothermites. It is found that the type of oxidizer within the nanothermite composition played a crucial role in the thermo-kinetic proprieties of the NC/DEGDN propellant. Specifically, nanothermites incorporating CuO and TiO₂ acted as catalysts, substantially enhancing the thermolysis of the propellant. In contrast, MgAl–NiO exhibited a stabilizing effect on the thermal decomposition of NC/DEGDN propellant. These findings offer appreciated insights into the tailoring properties of double-base propellant by selectively incorporating specific nanothermites based on their oxidizer content.

Two Mo-Bi based catalysts were prepared with the assistance of PMMA with different sizes, and tested in selective oxidation of tert-butanol to methacrolein. The prepared catalysts, especially C-PM-6 with μm-PMMA, exhibited excellent catalytic performance. Based on the characterization results (BET, MIP, SEM, TEM, XRD, FTIR), the effects of the assistance of PMMA with different sizes were verified. Without modifying the highly active Co₆Fe₄Mo₁₂Bi_1.5O_x phase, the formation of over-oxidation MoO₃ phase was effectively inhibited due to the decomposition of PMMA particles. Importantly, the PMMA assistance could develop hierarchical pore structures, especially mesoporous pores of 6 nm for C-PM-6 catalyst, by preventing primary particles’ agglomeration. Therefore, the mesoporous/macroporous specific surface area obviously increased and thus the abundant active sites were exposed. More importantly, in the newly-formed mesopores pores, there happened Knudsen or molecular diffusion with relatively high mass transfer coefficient, avoiding the overoxidation of target product MAL. From the perspective of reaction engineering, our finding may suggest a new way for developing ultra-high performance commercial selective oxidation catalyst.

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In this study, we synthesized a novel ceramic material Bi_0.5Na_0.5Ti_0.95 (Ni_0.2Fe_0.2Sb_0.6)_0.05O₃ named BNT-NFS via the solid-state route and assessed its efficacy as a photocatalyst for removing methylene blue dye from wastewater. The synthesized samples underwent thorough characterization using thermogravimetric analysis combined differential thermal analysis TGA-TDA, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) analysis, and UV–Visible measurements. TGA-DTA and XRD analyses confirmed the successful formation of BNT-NFS material at 1150 °C, exhibiting a hexagonal phase structure. FTIR analysis revealed an intense band at 421 cm⁻¹, corresponding to metal-oxide vibrations in the BNT-NFS spectrum. SEM observations unveiled a distinct microstructure of BNT-NFS composed of grains of varying sizes. BET analysis indicated that the prepared BNT-NFS powder possessed a significant specific surface area of 261.36 m²/g. Optical and photocatalytic assessments demonstrated that BNF-NFS perovskite is a semiconductor material with a band gap of 2.73 eV, exhibiting satisfactory photocatalytic activity for methylene blue MB dye removal. Notably, the removal efficiency reached 60% after 210 min of exposure to sunlight irradiation. This result is better than that registered for the pristine BNT.

In this study, the UVA-induced degradation of Basic Red 18 and Reactive Red 180 was examined using a photocatalytic treatment system using magnetic activated carbon derived from the fruit rind of Brachychiton populneus. Numerous factors, including the pH of the solution, the dose of photocatalyst, and the initial concentration of the dye, have been optimized because they affect the photocatalytic activity of magnetic activated carbon.The pH of the solution (6 for basic Red 18 and reactive red 180) and 0.75 g L⁻¹ of magnetic activated carbon with a degradation rate of 100% and 82% for Basic Red 18 and Reactive Red 180, respectively, are the parameters that should be set at their optimal values for an initial dye concentration of 50 mg L⁻¹. Superoxide and electrons are the main active species and play a major role in the photocatalytic degradation of dyes by magnetic activated carbon under UVA light irradiation. The two dyes had five cycles of reuse, according to a study on magnetic activated carbon that was completed under optimal conditions.

In this study, manganese-doped titanium dioxide nanoparticles (Mn–TiO₂), strontium-doped titanium dioxide (Sr–TiO₂), and co-doped with both manganese and strontium (Mn–Sr–TiO₂) were synthesized using the sol–gel method. The resulting powders underwent comprehensive characterization employing techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-Diffuse Reflectance Spectroscopy (UV–DRS), and Fourier-transform infrared spectroscopy (FT–IR). X-ray diffraction pattern analysis confirmed the presence of the anatase phase in the catalyst. According to the Scherrer equation, the crystallite size was estimated to be 12 nm for pure TiO₂ and 10 nm for co-doped TiO₂. Importantly, co-doping induced a reduction in the band gap energy, decreasing from 3.3 to 3.05 eV. The photocatalytic performance of the synthesized materials was evaluated for the degradation of methylene blue (MB), revealing that co-doping facilitated the degradation of 95% of the target compound (MB) within 2 h. The synergistic interaction of manganese and strontium ions played a crucial role in reducing the band gap of TiO₂ and delaying the recombination of photo-generated electrons and holes. This synergistic interplay between manganese and strontium enhanced photocatalysis, reducing the total organic carbon (TOC) content from 35.6 to 5.5 mg/l after 2 h of UV light exposure.

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We investigated the effect of linker defects induced by recycling MOF-508, a metal–organic framework with dual linkers, for the catalytic cycloaddition of the CO₂ reaction. MOF-508 catalysts are characterized using various analytical techniques such as powder XRD, FT-IR, FE-SEM, HR-TEM, TGA, BET, NH₃- and CO₂-TPD, NMR, and CO₂ adsorption isotherm. MOF-508 catalysts could perform the coupling reaction between epoxide and CO₂ with > 99% selectivity toward cyclic carbonates under solvent-free and moderate reaction conditions. After the cycloaddition reaction, the recycled MOF-508 exhibited higher catalytic activity than freshly prepared MOF-508 at all the temperature ranges. The origin of increased cyclic catalytic activities was attributed to the creating of additional catalytic active sites from the linker defects. Molecular modeling techniques were used to elucidate the catalytic mechanism and quantify the degree of linker defects in MOF-508.

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Zinc oxide (ZnO) powder synthesized by microwave irradiation method was used as photocatalyst for optimization of the photocatalytic degradation conditions of Rhodamine B dye under UV irradiation. The structural, morphological and optical characterizations of elaborated ZnO were performed by infrared spectroscopy, UV spectroscopy, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and Bruner-Emmett-Teller surface area analysis. Plackett–Burman design was first used to evaluate the effects of five parameters (initial dye concentration, contact time, lamp height, material dose and initial pH of the solution) on the photocatalytic degradation efficiency of the dye. The obtained results showed that contact time and initial dye concentration are the parameters that influence the photocatalytic degradation yield. The effects in decreasing order of the five factors were as follows: contact time (46.597) > initial dye concentration (− 29.149) > lamp height (− 8.419) > ZnO mass (7.263) > pH (1.0072). Subsequently, a central composite design for the two influencing parameters was performed to optimize the dye photodegradation process. It was found that the effect of contact time on the photodegradation efficiency was the highest, followed by the effect of initial dye concentration, and the interactions between initial dye concentration and contact time. The predicted and the experimental values were found to be in good agreement; the coefficient of determination value 0.996 and the adjusted coefficient of determination value 0.993 indicated that the model was significant. First‐order kinetic model successfully fitted the experimental data. The synthesized photocatalyst was found to be photostable during at least five regeneration cycles.

This research paper investigates the photodegradation of Malachite Green (MG) using a new composite of river sediment (Sd) and synthesized TiO₂ (Sd-TiO₂-X%). TiO₂ powder was synthesized using the sol–gel method and catalyst composites Sd-TiO₂-X% (X = 10%, 15%, and 20%) were obtained using the wet impregnation. The photocatalytic performance of the composites was investigated using Box–Behnken design and results in the optimal parameters of %TiO₂ (%) = 19.73, [MG] (ppm) = 42.25, and pH 9.58. Furthermore, Sd-TiO₂-20% demonstrated exceptional stability and performance after undergoing five cycles. The scavenging tests for free radicals strongly confirmed the activity of superoxide ions (O₂^⋅−) and hydroxyl radicals (^⋅OH) as the primary species responsible for degrading MG. The findings highlight the synergetic effect between river sediment and TiO₂ in the photodegradation of organic pollutants-contaminated wastewater. This confirms the potential of valorizing sediments for promising and sustainable depollution applications using sediment-based materials.