Topics in Catalysis最新文献

Solid acids and super-acids have been the subjects of continued interest due to their numerous applications in many chemical and pharmaceutical industries. They are claimed to be responsible for producing more than 1 × 10⁸ metric tons of products per year. In recent times, in particular, inorganic solid acid-catalyzed organic synthesis and transformation reactions have gained more attention due to the proven advantage of heterogeneous catalysts, simplified product isolation, mild reaction conditions, high selectivity, ease in recovery and reuse of the catalysts, and reduction in the generation of wasteful side products. In that context, we were interested in investigating various industrially important organic reactions to replace toxic and corrosive reagents, noxious or expensive solvents, and multistep processes with single-step and solvent-free ones by employing environmentally benign solid acid catalysts. The primary objective of this mini-review is to summarize the recent developments in biomass-based organic synthesis and transformation reactions of commercial significance catalyzed by WO_x/ZrO₂ green solid acid catalysts. The preparation of catalysts and their characterization are briefly discussed, emphasizing the application of these catalysts for a variety of practical reactions.

In this present review paper, the catalytic applications of carbon quantum dots (CQDs) as an efficient heterogeneous catalyst for organic conversion under sustainable and greener protocols have been investigated. The CQDs have carboxylic acid and hydroxyl functional moieties utilized for the modification of the surface of the CQDs. Moreover, CQDs and CQD-based composites have generated C–C, C–N, C–O, etc., bonds that leads to various organic synthesis via straightforward methodology. The following CQDs and decorated CQDs such as magnetic CQDs, CNDs, CQDs-N(CH₂PO₃H₂)₂, CQDs-N(CH₂PO₃H₂)₂/SBA-15, BPEI-CD, CDs/Bi₂MoO₆, Cu(I)-doped CQDs and SCQDs catalyzed one-pot multicomponent reactions are discussed. And also, CQDs and decorated CQDs have ensured excellent stability, recyclable, economically viable, and environmentally friendly, shorter reaction time, and avoid tedious work-up procedures. This review paper highlighted the synthesis of a one-pot multicomponent reaction catalyzed by the CQD catalyst.

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Single atom catalysts (SACs) have attracted significant interest due to their unique properties and potential for enhancing catalytic performance in various chemical reactions. In this study, we atomistically explore adsorption properties and catalytic performance of single Cu atoms anchored at low-index CeO₂ surfaces, focusing on the oxidation of CO and H₂. Utilizing density functional theory (DFT) calculations, we report that Cu adatoms bind favorably on different CeO₂ surfaces, following a stability order of (100) > (110) > (111). The charge transfer from a single adsorbed Cu atom to Ce leads to the reduction of Ce⁴⁺ to Ce³⁺ and the oxidation of Cu⁰ to Cu⁺. This strengthens molecular bonds at Cu sites, particularly for CO, while H₂ shows a by ~ 1 eV weaker adsorption. CO oxidation is energetically more favorable than H₂ oxidation on the Cu/CeO₂(111) surface. The rate-controlling steps for the Mars–van Krevelen mechanism involve the formation of a bent CO₂ intermediate for CO and H₂O for H₂. The lattice oxygen atom at the interface plays a key role for both oxidation processes. Our findings highlight the potential of single atom catalyst, Cu/CeO₂, for selective CO adsorption and its subsequent oxidation in heterogeneous catalysis.

In this work, Ni-Ga oxides in bulk and supported onto alumina were prepared by coprecipitation and impregnation for the evaluation of the oxidative dehydrogenation (ODH) of ethane assisted by CO₂. X-ray diffraction (XRD) results indicate that the enhanced catalytic activity exhibited by the Ni-Ga oxides bulk catalysts could be related to NiO crystallite size (8 nm) in addition to the high dispersion of the active phase observed by scanning electron microscopy (SEM). Diffuse reflectance spectroscopy (UV-Vis DRS) displayed a Ni predominance with octahedral symmetry (O_h) for the catalysts. X-ray photoelectron spectroscopy (XPS) revealed changes in the surface chemical environment for the catalysts related to the gallium promoter effect. Ni 2p_3/2 analysis indicated that the Ni²⁺ and Ni³⁺ ions, Ni²⁺-OH species, or Ni²⁺ vacancies on the surface of the unsupported catalysts have an important role in catalytic activity. In addition, Ga 3d results suggest that the catalytic activity of the unsupported catalysts could be connected to the similar concentration of Ga^y and Ga³⁺ species (ca. 50%), whereas the absence of activity for supported catalysts could be attributed to the Ga³⁺ species concentration higher than 90%. Finally, relationships for ethane conversion and selectivity toward ethylene with the Ox_(nuc)/Ox_(ele) ratio were found. The analysis of the peak areas in O 1s spectra revealed that the higher selectivity toward ethylene of the NiGa-8 catalyst (ca. 95%) could be related to a similar peak area of nucleophilic and electrophilic oxygen species in the surface.

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This study aims to develop a sustainable and recyclable SnO–CeO₂ nanocomposite catalyst for efficient one-pot synthesis of 5-amino-1,3-diphenyl-1 H-pyrazole-4-carbonitrile in water under mild conditions. SnO–CeO₂ nanocomposite was synthesized via a simple coprecipitation method and characterized using XRD, SEM, TEM, FTIR, XPS, BET, and UV-Visible spectroscopy. Its catalytic performance was evaluated in one three-component reaction of malononitrile, phenylhydrazine, and substituted aromatic aldehydes, using water as a green solvent. The recyclability of catalyst was assessed over multiple reaction cycles. The nanocomposite exhibited excellent catalytic efficiency, achieving high yields (81–96%) in shorter reaction times compared to conventional methods. Structural integrity and catalytic activity were retained after five cycles, confirming its stability and recyclability. The synthesized compounds were confirmed via ¹H NMR and ¹³C NMR spectral analysis. The synergistic effect between SnO and CeO₂ enhances catalytic performance, making nanocomposite a sustainable and cost-effective alternative to conventional catalysts. Its high efficiency, water-mediated reaction conditions, and reusability reinforce its potential for green and scalable organic synthesis.

Beech-wood lignin, derived from the wood of beech trees (genus Fagus), is a lignin-rich biomass with significant potential for valorization. Beech forests are prevalent in temperate regions worldwide, and beech wood possesses desirable properties for various applications, including the construction industry, furniture-making, and pulp production. The oxidative depolymerization of hardwood lignin is a sustainable approach to converting complex lignin structures into high-value aromatic compounds. In this study, the depolymerization of hardwood lignin was optimized using a Box-Behnken design (BBD) quadratic regression model to maximize monomer yields. The model demonstrated high predictive accuracy, with significant alignment between predicted and actual results, indicating its reliability in optimizing reaction conditions. Key operating parameters – temperature, pressure, and reaction time—were systematically varied, and the optimal conditions for monomer yield were found to be 191 °C, 5 bar O₂ pressure, and 25 min. Under these conditions, the primary monomers obtained included syringaldehyde (5.78 wt%) and vanillin (2.31 wt%), along with smaller quantities of acetovanillone, acetosyringone, syringol, and guaiacol. The reducing ability of the resulting monomers was investigated using density functional theory calculations, where electron, hydrogen-atom, and hydride donation ability were determined. Finally, size-exclusion chromatography confirmed the effective breakdown of lignin, showing distinct differences between blank and oxidized samples. This study highlights the effectiveness of oxidative depolymerization under controlled conditions for converting hardwood lignin into valuable aromatic compounds, with the BBD model playing a crucial role in optimizing the process for efficient lignin valorization.

Cyclic voltammetry (CV) is a fundamental electrochemical technique for studying catalytic surfaces, while IrO₂ serves as the gold standard for the oxygen evolution reaction in green hydrogen production. In this study, we simulated theoretical CV on IrO₂ surfaces with different orientations and compared the results with experimental data. Our findings reveal that in heterogeneous electrocatalysis, a single redox couple can manifest as multiple redox peaks, and conversely, a single redox peak may relate to multiple redox couples. This complexity arises from the interplay between surface structure and adsorbate coverage. We discuss strategies to enhance the accuracy and reliability of theoretical CV simulations, emphasizing the importance of comparing to high-quality experimental data from surfaces with low roughness and minimal pseudocapacitance. This integrated approach bridges theory and experiment, paving the way for improved predictions of catalytic activity and for the rational design of enhanced electrocatalysts for sustainable energy applications.

This study examines the electrochemical behavior of endosulfan on a glassy carbon electrode (GCE) and offers an extensive computational analysis of its electronic properties and interaction with graphene surfaces. The poor electrochemical activity of endosulfan at the bare GCE was evidenced by CV experiments, necessitating further exploration into the catalytic contributions of the electrode. Computational studies showed the localization of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) on the dichloroethene group, which means that this region is involved mainly in oxidation and reduction processes. Further analysis using the Fukui function supported the identification of reactive sites and electron transfer properties, indicating significant electron-accepting behavior by the molecule. Comparative studies on the interaction of endosulfan with basal and terminal carbon atoms of graphene showed subtle binding energy variations, which establish the importance of structural and electronic properties in sensor design. The combination of electrochemical and computational analyses gives a platform for developing more advanced, selective sensors toward the detection of persistent organic pollutants like endosulfan.