Reaction Kinetics, Mechanisms and Catalysis最新文献

An operando Fourier transform infrared (FTIR) spectroscopy study of the catalytic conversion of isopropanol over a monolayer V₂O₅/TiO₂ catalyst was carried out at atmospheric pressure in a temperature range of 50–300 °C. The experiments were carried out using two FTIR spectrometers, which allowed us simultaneously to study the catalyst under reaction conditions, to analyze reaction products in the gas-phase, and to determine the isopropanol conversion. In addition, the catalyst state was analyzed by X-ray photoelectron spectroscopy (XPS) after treatments under reaction conditions. It was found that the reaction starts above 100 °C, the conversion of isopropanol increases with temperature, achieving 60% at 300 °C. The gaseous products include propylene, acetone, CO, and CO₂, with propylene being the main reaction product above 200 °C. It was also found that at low temperatures (between 50 and 150 °C), the main reaction intermediate adsorbed on the catalyst surface is molecular isopropanol, which is typical of the concerted elimination mechanism for the dehydration of isopropanol. At higher temperatures, there appear adsorbed acetone and carboxylate species on the catalyst surface. The overall mechanism for the catalytic conversion of isopropanol on supported vanadium oxide catalysts is discussed.

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The Nano-Chitosan was synthesized using the ionic gelation method, and then nano-chitosan/cefadroxil drug blends (NCH-Ce) were created using a Schiff base reaction via the microwave method. The reaction was confirmed using Fourier transforms infrared spectroscopy (FT-IR). Different blends were prepared by mixing the NCH-Ce with natural rubber (NCH-Ce/NR) using varying ratios of NCH-Ce. The micrographs obtained from TEM and FESEM showed spherical-shaped particles with smooth surfaces in the Nanometric range. The vulcanization kinetics of the NCH-Ce/NR blends were investigated using an oscillating disc rheometer. The study found that all blends’ scorch and curing times were significantly reduced by adding NCH-Ce, with values decreasing from 0.87 and 2.33 to 0.56 min and 0.68 min. The maximum vulcanization rate increased with increasing NCH-Ce loading, ranging from 0.435 to 4.029 min⁻¹, while the maximum torque values decreased from 16.28 to 7.88 Nm. The autocatalytic model best describes the reaction kinetic model of pure NR and NCH-Ce/NR blends. Therefore, the vulcanization kinetics of NR and its blends were found to be dominated by two steps, chemical, and diffusion. It was concluded that NCH-Ce acts as a vulcanizing agent for NR, leading to an enhancement in the rate of vulcanization.

A new heterocyclic compound, N,N-dimethyl-4-(3-phenyl-4,5-dihydro-1,2-oxazol-5-yl) aniline (DOD), was synthesized and investigated as a corrosion inhibitor for mild steel in 1 M hydrochloric acid (HCl). Structural characterization was confirmed by proton and carbon nuclear magnetic resonance (¹H and ¹³C NMR) spectroscopy. Corrosion inhibition performance was evaluated through weight loss (WL), potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS). Surface morphology analysis by scanning electron microscopy (SEM) revealed the formation of a protective film on the steel surface. Quantum chemical calculations, including frontier molecular orbitals and Fukui indices, provided insight into the reactivity and adsorption behavior of the compound. Molecular docking simulations demonstrated strong binding affinities of DOD with proteins 3SX6 (− 8.1 kcal/mol) and 1H1O (− 7.9 kcal/mol), from Acidithiobacillus ferrooxidans and Thiobacillus ferrooxidans, both of which contribute to microbiologically induced corrosion. At a concentration of 5 × 10⁻⁴ M and 303 K, DOD showed inhibition efficiencies of 92% (WL), 83.13% (PDP), and 94.78% (EIS). The PDP results indicated mixed-type inhibition behavior, while EIS data confirmed the formation of a stable adsorbed layer. The adsorption process followed the Langmuir isotherm model and kinetic/thermodynamic parameters indicated a dual mechanism involving both physisorption and chemisorption. Theoretical findings were in good agreement with the experimental results, confirming the efficiency and multifunctional performance of DOD as a corrosion inhibitor.

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This study investigated the adsorption of textile dyes (specifically the trisodium ferric complex of N-methyl-1,8-naphtalimide-4-sulfonate) from contaminated wastewater, focusing on a comparative analysis of industrial chitosan and iron-chitosan as adsorbent materials. Several physico-chemical analyses such as Fourier-transform infrared spectroscopy, X-ray diffraction and pH zero point charge were performed to characterize the adsorbent. Kinetic experiments demonstrated that iron modification significantly enhanced chitosan's adsorption capacity (96% of elimination), with equilibrium being achieved within 120 min for both adsorbents. Adsorption isotherm data were best described by the Freundlich model, indicating a heterogeneous adsorption process. The initial solution pH profoundly influenced dye removal; industrial chitosan exhibited optimal adsorption under basic conditions, while iron-chitosan performed best in acidic environments. Furthermore, a medium agitation speed was identified as optimal, facilitating both faster adsorption rates and higher retention capacities for both adsorbents compared to static or high agitation conditions. These findings highlight the potential of both chitosan forms, particularly the iron-modified variant, for efficient textile dye removal in wastewater treatment applications.

In this study, lead and lead-free simple perovskite nanomaterials were used as ferroelectric photocatalysts for the first time to degrade ibuprofen (IBP) (25 mg/L), under UV (254 nm) light. The materials BaTiO₃ (BT-h), BaZrO₃ (BZ-h), PbTiO₃ (PT-h), and PbZrO₃ (PZ-h) were prepared using a straightforward hydrothermal method. The morphology, surface area, pore size, crystalline phase purity, and optical properties of these materials were characterized by scanning electron microscopy (SEM), N₂ adsorption/desorption measurements, X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, and diffuse reflectance spectroscopy (DRS). SEM, XRD, Raman, and FTIR analyses confirmed the nano-perovskite structure in all materials, indicating piezoelectric characteristics due to their non-centrosymmetric nature. The photocatalytic degradation of IBP was monitored by high-performance liquid chromatography (HPLC). The results show photocatalytic efficiencies reaching 99% after 120 min, highlighting a strong ferroelectric effect in the BT-h, BZ-h, and PT-h photocatalysts, which induced spontaneous polarization that generates an electric field and enhances charge separation in the photocatalytic process. In contrast, PZ-h showed moderately lower degradation efficiency (86%) due to its antiferroelectric properties. BT-h exhibited excellent reusability, maintaining high degradation efficiencies over five consecutive cycles (99%, 95%, 94%, 94% and 92%, respectively). Gas chromatography–mass spectrometry (GC–MS) provided insights into the degradation mechanism, identifying four intermediate products formed during IBP degradation in the presence of BT-h, leading to mineralization at the reaction end. It also demonstrated admirable performance even under near-visible UV irradiation (360 nm), achieving a degradation rate of 84% after 120 min. Overall, our findings reveal that photocatalytic efficiency in IBP degradation is primarily driven by the ferroelectric properties of these materials, which promote effective charge separation under UV irradiation.

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Zinc-doped Zn_xCd_0.8-XBa_0.2Al_0.2Fe_1.8O₄(X = 0, 0.2) spinel ferrite nanoparticles were synthesized via the sol–gel auto-combustion method and characterized by XRD, FTIR, SEM, EDX, BET, and UV–Vis spectroscopy. Zinc incorporation at x = 0.2 reduced the optical bandgap from 2.86 eV to 2.69 eV, increased BET surface area from 7.54 to 10.23 m²/g (35.6% enhancement), and decreased crystallite size from 22.26 to 18.82 nm. Under visible-light irradiation (100 W, 105 min), the zinc-doped catalyst achieved 98% tetracycline degradation compared to 50% for the undoped material. The catalyst demonstrated broad-spectrum activity with degradation efficiencies of 85, 77, 65, and 48% for Congo Red, Rhodamine B, 65% for Methylene Blue, and 48% for Methyl Orange, respectively. The addition of peroxymonosulfate, hydrogen peroxide, and persulfate resulted in complete tetracycline removal at 15, 30, and 45 min, respectively. Scavenger experiments identified hydroxyl radicals as the primary degradation species, contributing to 63% of the overall process. The catalyst maintained an 82% efficiency after five consecutive cycles. Optimal performance was achieved at pH 3 (complete degradation in 30 min) with an 80 mg catalyst dosage (complete removal in 45 min). Under natural sunlight, complete tetracycline degradation was achieved in 30 min, demonstrating superior performance compared with artificial light sources.

Plasma-sprayed CoNiCrAlY alloy and yttria-stabilized zirconia (ZrO₂ + 8% Y₂O₃) coatings were investigated as scalable electrodes for the hydrogen evolution reaction (HER) in alkaline media. Coatings were deposited on mild steel substrates using atmospheric plasma spraying, followed by detailed structural, morphological, and electrochemical characterization. The CoNiCrAlY alloy exhibited a dense face-centered cubic (FCC) structure, while the ceramic displayed a stabilized tetragonal phase. Surface profilometry revealed high roughness values for both coatings (Ra = 14.742 µm for CoNiCrAlY, 12.55 µm for YSZ), enhancing surface area. Electrochemical measurements revealed that CoNiCrAlY exhibited enhanced HER activity, evidenced by a lower Tafel slope (0.1627 V/dec), higher exchange current density (4311.86 mA/cm²), and faster hydrogen evolution rate (5092.98 μmol/h) compared to YSZ (0.3186 V/dec, 711.22 mA/cm², 3547.55 μmol/h). Electrochemical impedance spectroscopy confirmed lower charge transfer resistance and Warburg-type diffusion behavior for the metallic coating. Raman spectroscopy identified protective oxide layers (Cr₂O₃, Al₂O₃) on the alloy surface, which contribute to increased durability. These findings highlight the promising catalytic performance and scalability of CoNiCrAlY coatings for alkaline water electrolysis.

In this study, palladium and copper alloy supported on carbon and carbon hybrid tungsten oxide (IV) (WO₃) for the oxygen reduction reaction (ORR) catalytic activities have been investigated. The nanostructured PdCu/C catalyst worked effectively in both acidic and alkaline conditions. The impact of adopting a WO₃ hybrid support medium i.e., PdCu/C-WO₃ on oxygen reduction reaction (ORR) have counted in both media. The phase transfer approach was used to synthesize a stable PdCu nanocatalyst (50:50). The synthesized nanocatalyst were characterized by X-ray diffraction (XRD), high-resolution electron microscopy (HRTEM) and fourier transform infrared (FTIR) techniques. The XRD peaks confirmed the alloy between Pd and Cu, and the particle size was less than 5 nm according to HRTEM. The FTIR data, revealed the bands of oxide’s resonance in its distinctive region. The electrochemical behaviour was determined by cyclic voltammetry (CV) via rotating ring disk electrode (RRDE). The WO₃ hybrid carbon supported PdCu demonstrated better ORR specificity and mass activities than unhybrid PdCu, in both media. The PdCu/C-WO₃ was more efficient than PdCu/C due to the structural effect significantly improved the efficiency of the synthesized nanocatalyst. Density function theory (DFT) calculations corelated with catalytic performance in term of energy of interaction of O₂ molecule on the prepared materials as well as its structures orientation and charge transfer approach. Both experimental and the theoretical analysis shows that the PdCu support on carbon hybrid with WO₃ have enhanced the catalytic activities for ORR.

The article presents the results of catalytic tests of copper-containing catalysts in the process of liquid-phase dehydration of glycerol to acetol. Copper-containing systems were obtained by various methods, including ion exchange, coprecipitation, thermal decomposition and reduction of the corresponding salts. All the catalysts were characterized by IR, SEM, EDS and BET surface area. The conversion of glycerol to acetol was carried out by reactive distillation in a batch reactor. The highest conversion of glycerol of 94% with a selectivity of acetol formation of 42% was achieved in the presence of 5 wt% Cu₂O for 6 h at 240 ℃ and a vacuum of 2.9 kPa. The distilled liquid product was analyzed by HPLC, GC and GC–MS. The surface acidity of the catalyst was evaluated by NH₃-TPD. The change in catalytic activity for acetol does not correlate with the decrease in acidity in the series: Cu₂O/Al₂O₃ → CuO → Cu → Cu₂O and can be explained by the HSAB theory. Cu₂O activity decreases during the recycler, which can be explained by Cu₂O transformation into Cu° (detected by XRD method), sintering of catalyst particles and tarring of catalyst surface caused by resin products (detected by BET surface area).

This study evaluates the efficiency of non-oxidative regeneration strategies for removing coke deposits from spent catalysts. Solid-state nuclear magnetic resonance and Fourier-transform infrared spectroscopy were used to characterize the structural and compositional properties of the coke. A two-step regeneration process combining accelerated solvent extraction (ASE) and hydrotreatment (HT) was applied at pilot scale. The aliphatic carbon content of the coke decreased from 39% in untreated samples to 17% after ASE and further to 3% following wet HT. Dry HT, involving heated hydrogen under pressure, promoted the formation of light hydrocarbons such as methane and ethane by disrupting carbon–catalyst bonds. Wet HT refers to utilizing a mixture of hydrogen and hydrogen sulfide gas under high-temperature and pressure, and dry and wet HT methods removed substantial amounts of coke, while Dry HT proved remarkably effective, eliminating over 72% of the deposited coke. However, HT-severe conditions (HT-S1) increased coke aromaticity. These findings provide practical insights into the development of non-oxidative regeneration protocols for spent refinery catalysts, thereby minimizing catalyst degradation while enhancing coke removal efficiency.