Topics in Catalysis最新文献

A six-step synthesis to (+)-nebivolol ((S,R,R,R)-nebivolol or d-nebivolol) in a cumulative yield of 32% has been developed. Conventional use of diazo compounds has been replaced with a novel approach of sulphur ylide for a safer one-carbon chain extension of methyl 6-fluorochromane-2-carboxylate, which entailed the formation of racemic 2-[dimethyl(oxido)-λ6-sulfanylidene]-1-(6-fluoro-3,4-dihydro-2H-chromen-2-yl)ethenone from methyl 6-fluorochromane-2-carboxylate in high yield. Subsequently the β-keto sulfoxonium ylide was converted into 2-chloro-1-(6-fluorochroman-2-yl)ethanone. Reduction of 2-chloro-1-(6-fluorochroman-2-yl)ethanone to 2-chloro-1-(6-fluorochroman-2-yl)ethanol was catalyzed by Ketoreductase 228 from Syncozymes and resulted in halohydrins (R)-2-chloro-1-((S)-6-fluorochroman-2-yl)ethanol and (S)-2-chloro-1-((S)-6-fluorochroman-2-yl)ethanol in 92% yield. The halohydrins were separated by preparative HPLC. (S)-2-Chloro-1-((S)-6-fluorochroman-2-yl)ethanol underwent amination to produce (R)-2-amino-1-((S)-6-fluorochroman-2-yl)ethanol. The final synthesis step involved reaction of (R)-2-amino-1-((S)-6-fluorochroman-2-yl)ethanol and (R)-2-chloro-1-((S)-6-fluorochroman-2-yl)ethanol forming (+)-nebivolol with > 99% enantiomeric excess (ee).

In this study, a novel PCL-based polymer (6) containing A₃B-type zinc phthalocyanine was synthesized as a result of the ring-opening polymerization of ε-caprolactone (ε-CL), in which A₃B-type zinc phthalocyanine (5) prepared by condensation method of two different phthalonitrile precursor molecules, 4-(3-hydroxypropylmercapto)phthalonitrile (3) and 4-tert-butylphthalonitrile (4), in 3:1 molar ratios used as the initiator. (6) was synthesized in three stages; the synthesis of 4-(3-hydroxypropylmercapto)phthalonitrile (3) (i), novel A₃B-type zinc phthalocyanine (ii), PCL-based polymer (6) containing A₃B-type zinc phthalocyanine (iii). The novel compounds (5) and (6) were characterized by spectroscopic (FTIR, ¹H NMR. ¹³C NMR and UV-vis), DSC and chromatographic (GPC) methods. After that, a new generation hybrid material (PcY-MWCNTP and PcX-MWCNTP) was developed by treating bare Pc (PcX) and polymer-based Pc (PcY) with carboxyl-functionalized multi-walled nanocarbon tube powders (COOH-MWCNTPs). This new nanomaterial was also coated on the glassy carbon electrode (GCE) surface using the drip-dry technique. The sensitivities of the developed both nanosensor in the determination of rifaximin were investigated at first time. Compared to the other electrode, PcX-MWCNTP/GCE significantly increased the anodic signal of rifaximin (approximately 5-fold) and shifted the peak potential to the less positive region. A wide working range from 0.25 mg/L to 10.0 mg/L was obtained, and the limit of detection (LOD) was calculated as 48 µg/L by differential pulse voltammetry (DPV). Finally, the electrochemical method was successfully applied analytically in natural samples to test its accuracy and precision by using PcX-MWCNTP/GCE.

Arylhydrazone ligands Hsal-bzh (I), Hcsal-bzh (II), Hbsal-bzh (III), and Hnsal-bzh (IV) were synthesized using ethyl benzoate, hydrazine hydrate, salicylaldehyde and its 5-substituted –Cl, –Br, and –NO₂ derivative from refluxing methanol. Carefully characterized ligands I-IV, were reacted with appropriate vanadium precursor to isolate the oxidomethxidovanadium(V) complexes [VO(sal-bzh)(CH₃OH)(OCH₃)] (1), [VO(csal-bzh)(CH₃OH)(OCH₃)] (2), [VO(bsal-bzh)(CH₃OH)(OCH₃)] (3) and [VO(nsal-bzh)(CH₃OH)(OCH₃)] (4) as well as dioxidovanadium(V) complexes K[V^VO₂(sal-bzh)] (5), K[V^VO₂(csal-bzh)] (6), K[V^VO₂(bsal-bzh)] (7) and K[V^VO₂(nsal-bzh)] (8). A number of techniques like ⁵¹V NMR, ¹H NMR, ¹³C NMR, single crystal X-ray analysis, HR-MS analysis were performed to confirm the molecular structure of the vanadium(V) complexes in solid state as well as in solution. Dioxidovanadium(V) complexes 5–8 show good catalytic performance towards the homogeneous epoxidation of a series of olefins with high TOF values. Electron-rich and sterically accessible olefins indene exhibit the highest substrate conversion (94%) with very high TOF values of 3.032 × 10³ h⁻¹, and the least reactivity is observed in electronically poor allylbenzene. Generally, catalysts with the electron-withdrawing group at the 5-position of salicylaldehyde in 6–8 exhibit marginally better performance than catalysts with unsubstituted salicylaldehyde. During the catalytic reaction, the formation of oxidoperoxymonocarbonatevanadium(V) {[V^VO₂(OCO₃H)(nsal-bzh)] + H} intermediate, which is supposed to be the key component for epoxidation, was identified by ⁵¹V NMR and confirm by HR-MS analysis.

This study focuses on the fabrication and characterization of ZrO₂‒TiO₂ mixed oxides modified with gallium and surfactants and their potential application as supports for NiW hydrodesulfurization (HDS) catalysts. The mixed oxides were synthesized via the soft template sol‒gel method with the incorporation of triblock copolymers as surfactants (P123 and L64). We focus on the incorporation of gallium into the supports to modify their surface properties and acidity. The NiW catalysts were evaluated in the HDS of dibenzothiophene (DBT) under high pressure conditions. The results demonstrated that the incorporation of surfactants induced an increase in surface area and an improvement in pore structure within the oxides, which in turn led to enhanced dispersion of the active phases. Additionally, gallium facilitated the sulfidation of the W species and the formation of the NiWS active phase. The catalytic test demonstrated that the catalyst prepared with surfactants, particularly the NiW/ZT-P-Ga catalyst, exhibited the highest initial reaction rates and selectivity toward the hydrogenation pathway. The study demonstrated that the combination of surfactants and gallium ions in the preparation of ZrO₂–TiO₂ supports can significantly enhance the performance of NiW catalysts for deep desulfurization. These findings contribute to the development of more efficient catalysts for industrial HDS processes, addressing the challenges posed by refractory sulfur compounds in fuels.

Green synthesis is a sustainable alternative to traditional chemical methods for nanomaterial-based sensors because it is more affordable, scalable, and does not involve any harmful contaminants when using green materials’ extracts as stabilizing and reducing agents for nanoparticle synthesis. The green-synthesized nanoparticles are extremely attractive for various pharmaceutical applications. This review article examines the most preferred eco-friendly nanomaterials, their synthesis and characterization, and their pharmaceutical applications based on the selected studies conducted in the last five years. It concludes that the green synthesis methods allow the transformation of metals into nanoparticles or green materials that act as precursors to carbon-based nanomaterials. The nanoscale materials obtained through green synthesis methods contribute to low toxic, environmentally benign, easy, and low-cost sensing and enhanced electrocatalytic performance.

In this work, it is reported the physicochemical characterization and photocatalytic activity evaluation of TiO₂ thin films modified with Eu, Pd, Fe and Bi. Several characterization techniques were used to investigate thin film properties. The chemical composition as well as the chemical environment of the elements present were determined by X-ray photoelectron spectroscopy (XPS). The crystalline structure was characterized by X-ray diffraction (XRD) and micro-Raman spectroscopy (RS) whereas the optical band gap was determined using UV-Vis spectroscopy. The photocatalytic activity was evaluated in the degradation of the Malachite Green (MG) dye using simulated sunlight. It was found that films modified with Fe and Pd reached MG degradations close to 64.7 and 58.1% after 180 min of reaction. Additionally, thin films were photocatalytically evaluated under UV light (λ=254 nm) using wastewater containing diclofenac (DCF). The best catalytic performance (44% was reached by the film modified with Fe followed by the films modified with Pd (39%) and Bi (38%). To identify the role of reactive species for degradation of MG and DCF, triethanolamine (TEOA), isopropyl alcohol (IPA), ascorbic acid (AA) and benzoquinone (BZQ) were employed as scavenger’s molecules. The results obtained revealed that the O₂^• radical is the reactive specie that mainly contributes to the MG and DCF degradation.

Graphical abstract

Nanotechnology aims to enhance the progress of superior and highly intelligent products by manipulating molecules and atoms that are smaller than 100 nm, referred to as nanoparticles. These nanoparticles can be synthesized utilizing numerous techniques, such as chemical and physical approaches. Drawbacks associated with physical and chemical methods in nanoparticle synthesizing, such as environmental harm, equipment requirements, high temperature needs, and substantial expenses, underscore the importance of utilizing an eco-friendly approach that minimizes damage and costs. This necessity has been addressed through green synthesis techniques which aim to protect the environment by replacing hazardous chemicals with bioactive agents like plant-based materials, microorganisms, and diverse biowastes like waste of vegetable, fruit peel biomass, eggshell, agricultural byproducts, and more. Nanoparticles derived from the green synthesis have garnered remarkable attentiveness within the realm of electrocatalysis, specifically in the identification of different molecules, owing to their remarkable surface area to bulk atomic ratio. Electrochemical catalysis plays a pivotal role in nanotechnology, as it entails the manipulation of electrochemical reactions on electrode surfaces to augment reaction rates and system efficiency. By harnessing the potential of these nanoparticles, it becomes feasible to identify a wide range of biomarkers, thereby enabling the creation of a state-of-the-art system with exceptional capabilities.

We report the defluorination of the per- and polyfluoroalkyl substances (PFAS) chemical perfluorooctane sulfonate (PFOS) by deep ultraviolet light assisted electrocatalysis, using the industrial thermoelement materials Constantan and Nichrome as anodes. Surface analysis of wire anodes after anodic conditioning in aqueous base, which enabled uptake of incidental iron from the electrolyte, showed the in situ formation of surface nickel–iron (oxy)hydroxides, which are active electrocatalysts for PFOS defluorination. The defluorination activity of Constantan wire was higher than that of Nichrome wire, which was unstable under PFOS defluorination conditions. Constantan wire mesh completely defluorinated PFOS over a 48-hour period, maintaining 85.5% defluorination after 120 h. The decrease in PFOS defluorination efficiency was attributed to an increase in charge transfer resistance due to the buildup of transition metal hydroxides, oxyhydroxides, or oxides on the wire surface, rather than anode dissolution. Our results provide necessary mechanistic insights into the stability of commercially widely available nickel alloys for the development of economically viable aqueous PFAS remediation systems.

Potassium hexatitanate K₂Ti₆O₁₃ material was successfully synthesized by the sol-gel method. Silver was incorporated in different concentrations from 0.1 to 0.7 wt% by photo-deposition method. The Ag-K₂Ti₆O₁₃ composites were characterized by XRD, SEM, EDX, N₂ physisorption, UV–Vis diffuse reflectance spectroscopy, photoluminescence spectroscopy, and Mott-Schottky electrochemical test. The X-ray diffraction analysis showed an almost pure monoclinic crystalline phase of the K₂Ti₆O₁₃ with a preferential orientation in the plane (3 1 −1). Morphological characterization showed non-well-defined rod particles. The band-gap value for all the materials was 3.35 eV, while PL spectra showed a lower recombination rate of the photogenerated charges in Ag-KTO materials. The point of zero charge was also determined, resulting in pH values of 7.2 and 8.4 for K₂Ti₆O₁₃ and Ag-K₂Ti₆O₁₃ respectively. Catalysts with a lower content of silver show a higher density of positive holes generated with the irradiation of the semiconductor, consequently, these materials exhibited better photocatalytic activity towards the ketoprofen degradation. The results indicate that ketoprofen was completely degraded on 30 min of reaction generating several intermediate organic products that reached a maximum at 15 min, and 82% of all the organic compounds were mineralized in 5 h of reaction.

With increasing CO₂ pollution, the environment around us changes, necessitating our adaptation to these new conditions. A significant milestone in solving the environmental crisis would be the so-called hydrogen economy. However, this concept still faces substantial challenges as the required catalytic reactions show sluggish efficiency behaviors. To develop new generations of active electrocatalysts for those reactions better understanding of the nature of active sites is required. In 2017, Pfisterer et al. [1] demonstrated the power of tunneling current-noise analysis in electrochemical scanning tunneling microscopy (n-EC-STM) to detect active centers under reaction conditions. In this work, a new analytical tool has been developed to further enhance the distinction of active domains on catalytic surfaces. Additionally, an “activity curve” is introduced to achieve enhanced data representation. Several illustrative examples related to the reactions important for energy provision are presented.