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Zn Promoted Mg-Al Mixed Oxides-Supported Gold Nanoclusters for Direct Oxidative Esterification of Aldehyde to Ester.

ABSTRACT: The synthesis of ester compounds is one of the most important chemical processes. In this work, Zn-Mg-Al mixed oxides with different Zn²⁺/Mg²⁺ molar ratios were prepared via co-precipitation method and supported gold nanoclusters to study the direct oxidative esterification of aldehyde and alcohol in the presence of molecular oxygen. Various characterization techniques such as N₂-physical adsorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and CO₂ temperature programmed desorption (TPD) were utilized to analyze the structural and electronic properties. Based on the results, the presence of small amounts of Zn²⁺ ions (~5 wt.%) provoked a remarkable modification of the binary Mg-Al system, which enhanced the interaction between gold with the support and reduced the particle size of gold. For oxidative esterification reaction, the Au₂₅/Zn_0.05MgAl-400 catalyst showed the best performance, with the highest turnover frequency (TOF) of 1933 h^-1. The active center was believed to be located at the interface between metallic gold with the support, where basic sites contribute a lot to transformation of the substrate.

SUBMITTER: Li J

PROVIDER: S-EPMC8395456 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Monodispersed Pd Nanoparticles Supported on Mg-Al Mixed Metal Oxides: A Green and Controllable Synthesis.

Project description:Aimed at the green synthesis of supported noble metal nanoparticles without any additional reducing agents or stabilizers at room temperature, a new strategy in which monodispersed Pd nanoparticles were successfully immobilized on Mg-Al mixed metal oxides derived from layered double hydroxides was developed, and the reduction mechanism was also proposed. It allowed the in situ immobilization of monodispersed Pd nanoparticles with a face-centered cubic structure, using only alcohols with α-hydrogen atom as the solvent and reducing agent. Control over the mean particle size and content of Pd nanoparticles was realized by adjusting the temperature, initial concentration, and type of alcohol. With the content of Pd varied from 6.4 to 42.3 mg/g, the mean particle size of Pd increased from 1.1 to 4.9 nm. The as-prepared catalyst showed high catalytic activity for oxidation of benzyl alcohol: when the Pd content was 6.4 mg/g, conversion of 60.3% and selectivity of 99.2% were obtained with a turnover frequency of 4807 h-1. Similarly, on the basis of the high stand electrode potentials, immobilized Ag (5.6 nm) and Au (4.7 nm) nanoparticles were also prepared through this methodology. Moreover, the choice of supports was extended to other powder supports that would react with the byproduced acid. Overall, this facile method opens up new opportunities for controllable synthesis of supported nanoparticle catalysts in a green way.

| S-EPMC6640783 | biostudies-literature

A combined experimental and computational study on the reaction of fluoroarenes with Mg-Mg, Mg-Zn, Mg-Al and Al-Zn bonds.

Project description:Through a combined experimental and computational (DFT) approach, the reaction mechanism of the addition of fluoroarenes to Mg-Mg bonds has been determined as a concerted SNAr-like pathway in which one Mg centre acts as a nucleophile and the other an electrophile. The experimentally determined Gibbs activation energy for the addition of C6F6 to a Mg-Mg bond of a molecular complex, ΔG‡298 K(experiment) = 21.3 kcal mol-1 is modelled by DFT with the ωB97X functional, ΔG‡298 K(DFT) = 25.7 kcal mol-1. The transition state for C-F activation involves a polarisation of the Mg-Mg bond and significant negative charge localisation on the fluoroarene moiety. This transition state is augmented by stabilising closed-shell Mg···F ortho interactions that, in combination with the known trends in C-F and C-M bond strengths in fluoroarenes, provide an explanation for the experimentally determined preference for C-F bond activation to occur at sites flanked by ortho-fluorine atoms. The effect of modification of both the ligand coordination sphere and the nature and polarity of the M-M bond (M = Mg, Zn, Al) on C-F activation has been investigated. A series of highly novel β-diketiminate stabilised complexes containing Zn-Mg, Zn-Zn-Zn, Zn-Al and Mg-Al bonds has been prepared, including the first crystallographic characterisation of a Mg-Al bond. Reactions of these new M-M containing complexes with perfluoroarenes were conducted and modelled by DFT. C-F bond activation is dictated by the steric accessibility, and not the polarity, of the M-M bond. The more open coordination complexes lead to enhanced Mg···F ortho interactions which in turn lower the energy of the transition states for C-F bond activation.

| S-EPMC5897846 | biostudies-other

Study on Mg/Al Weld Seam Based on Zn-Mg-Al Ternary Alloy.

Project description:Based on the idea of alloying welding seams, a series of Zn-xAl filler metals was calculated and designed for joining Mg/Al dissimilar metals by gas tungsten arc (GTA) welding. An infrared thermography system was used to measure the temperature of the welding pool during the welding process to investigate the solidification process. It was found that the mechanical properties of the welded joints were improved with the increasing of the Al content in the Zn-xAl filler metals, and when Zn-30Al was used as the filler metal, the ultimate tensile strength could reach a maximum of 120 MPa. The reason for the average tensile strength of the joint increasing was that the weak zone of the joint using Zn-30Al filler metal was generated primarily by α-Al instead of MgZn2. When Zn-40Al was used as the filler metal, a new transition zone, about 20 μm-wide, appeared in the edge of the fusion zone near the Mg base metal. Due to the transition zones consisting of MgZn₂- and Al-based solid solution, the mechanical property of the joints was deteriorated.

| S-EPMC5453102 | biostudies-other

Effect of Tetrahedrally Coordinated Al on the Surface Acidity of Mg-Al Binary Mixed Oxides.

Project description:Metal oxides (MOs) having Mg and Al with Mg/Al ratios of 1, 2, 3, and 4 were synthesized via calcination of the layered double hydroxides (LDH). The X-ray diffraction analysis revealed that all the MO consisted of periclase (MgO) crystallite with comparable crystallinity regardless of the metal ratio. According to the 27Al magic-angle spinning nuclear magnetic resonance, the phase transformation from LDH to MO upon calcination facilitated the evolution of the Al3+ ions with unsaturated coordination at the surface of MO. The specific surface area values of MOs were not significantly different from each other, ranging between 100 and 200 m2/g, suggesting that the metal ratio did not strongly influence the porous structure of MO. The temperature-dependent desorption of ammonia demonstrated that the Lewis acidity of the Al-rich MOs was the largest with an Mg/Al ratio of 1, attributed to the efficient exposure of the surface-active site Al3+-O2- pairs. The acidity of heterogenous Al-rich MOs significantly increased with the exposed tetrahedral Al site on the surface and dramatically diminished when the molar ratio (Mg/Al) was over two.

| S-EPMC10459910 | biostudies-literature

Zn-Al and Mg-Al layered double hydroxide nanoparticles improved primary and secondary metabolism of geranium plants.

Project description:Layer double hydroxide (LDH) nanoparticles (NPs) have been applied to enhance plant growth and productivity. However, their effects on carbon and nitrogen metabolism of aromatic plants, are not well understood. Therefore, we investigated the impact of foliar application of Zn-Al LDH and Mg-Al LDH NPs (10 ppm) on the growth and metabolism of geranium plants. Zn-Al LDH and Mg-Al LDH NPs significantly increased the dry biomass, photosynthetic pigment, and Zn and Mg uptake by treated plants. These increases were consistent with increased primary metabolism such as soluble sugars and their metabolic enzymes (invertase and amylase). The supply of high sugar levels induced TCA organic accumulation, providing a pathway for amino acid biosynthesis. Among amino acids, proline level and its biosynthetic enzymes such as pyrroline-5-carboxylate reductase (P5CR), ornithine aminotransferase (OAT), and pyrroline-5-carboxylate synthetase (P5CS), glutamine synthetase (GS), and arginase were increased. Increased primary metabolites can then be channeled into secondary metabolic pathways, leading to higher levels of secondary metabolites including tocopherols, phenolics, and flavonoids. These observed increases in primary and secondary metabolites also improve the biological value of geranium plants. Overall, our research highlights the potential of Zn-Al LDH and Mg-Al LDH NPs as elicitors to enhance metabolism in geranium plants, thereby improving their growth bioactivity.

| S-EPMC11375793 | biostudies-literature

Transition Metal-Promoted Mg-Fe Mixed Oxides for Conversion of Ethanol to Valuable Products

Project description:The conversion of

| S-EPMC10249133 | biostudies-literature

Cationic Heterobimetallic Mg(Zn)/Al(Ga) Combinations for Cooperative C-F Bond Cleavage.

Project description:Low-valent (Me BDI)Al and (Me BDI)Ga and highly Lewis acidic cations in [(tBu BDI)M+ ⋅C6 H6 ][(B(C6 F5 )4 - ] (M=Mg or Zn, Me BDI=HC[C(Me)N-DIPP]2 , tBu BDI=HC[C(tBu)N-DIPP]2 , DIPP=2,6-diisopropylphenyl) react to heterobimetallic cations [(tBu BDI)Mg-Al(Me BDI)+ ], [(tBu BDI)Mg-Ga(Me BDI)+ ] and [(tBu BDI)Zn-Ga(Me BDI)+ ]. These cations feature long Mg-Al (or Ga) bonds while the Zn-Ga bond is short. The [(tBu BDI)Zn-Al(Me BDI)+ ] cation was not formed. Combined AIM and charge calculations suggest that the metal-metal bonds to Zn are considerably more covalent, whereas those to Mg should be described as weak AlI (or GaI )→Mg2+ donor bonds. Failure to isolate the Zn-Al combination originates from cleavage of the C-F bond in the solvent fluorobenzene to give (tBu BDI)ZnPh and (Me BDI)AlF+ which is extremely Lewis acidic and was not observed, but (Me BDI)Al(F)-(μ-F)-(F)Al(Me BDI)+ was verified by X-ray diffraction. DFT calculations show that the remarkably facile C-F bond cleavage follows a dearomatization/rearomatization route.

| S-EPMC8361950 | biostudies-literature

Experimental Investigation and Thermodynamic Verification for the Phase Relation around the ε-Mg23 (Al, Zn)30 Intermetallic Compound in the Mg-Zn-Al System.

Project description:The appearance of the ε phase during the welding process can severely weaken the welding strength of dissimilar metals of Mg-Zn-Al alloy systems. An understanding of the accurate phase diagram, especially the equilibrium phase relation around the ε phase, is thus of particular importance. However, the phase interrelation near the ε-Mg23(Al, Zn)30 phase has not yet been fully studied. In this work, the local phase diagrams of the ε phase and its surrounding phases in the Mg-Zn-Al system are systematically determined by experimental investigation and thermodynamic verification. Five Mg-Zn-Al alloys and one diffusion couple were fabricated and analyzed to get accurate phase constituents and relationships adjacent to ε phase. The current experimental data obtained from Scanning Electron Microscope (SEM), X-ray diffraction (XRD), Differential Scanning Calorimetry (DSC), and Electron Probe Micro Analysis (EPMA) were further compared with the thermodynamically computed phase relations around ε phase for verification, showing good agreements. Several important conclusions are drawn based on current experimental work, which can provide supporting information for the follow-up studies on ε phase in the Mg-Zn-Al alloy systems.

| S-EPMC8625525 | biostudies-literature

Co-Precipitated Ni-Mg-Al Hydrotalcite-Derived Catalyst Promoted with Vanadium for CO2 Methanation.

Project description:Co-precipitated Ni-Mg-Al hydrotalcite-derived catalyst promoted with vanadium were synthesized with different V loadings (0-4 wt%) and studied in CO2 methanation. The promotion with V significantly changes textural properties (specific surface area and mesoporosity) and improves the dispersion of nickel. Moreover, the vanadium promotion strongly influences the surface basicity by increasing the total number of basic sites. An optimal loading of 2 wt% leads to the highest activity in CO2 methanation, which is directly correlated with specific surface area, as well as the basic properties of the studied catalysts.

| S-EPMC8588090 | biostudies-literature

Computational Study on Selective PDE9 Inhibitors on PDE9-Mg/Mg, PDE9-Zn/Mg, and PDE9-Zn/Zn Systems.

Project description:PDE9 inhibitors have been studied to validate their potential to treat diabetes, neurodegenerative disorders, cardiovascular diseases, and erectile dysfunction. In this report, we have selected highly potent previously reported selective PDE9 inhibitors BAY73-6691R, BAY73-6691S, 28r, 28s, 3r, 3s, PF-0447943, PF-4181366, and 4r to elucidate the differences in their interaction patterns in the presence of different metal systems such as Zn/Mg, Mg/Mg, and Zn/Zn. The initial complexes were generated by molecular docking followed by molecular dynamics simulation for 100 ns in triplicate for each system to understand the interactions' stability. The results were carefully analyzed, focusing on the ligands' non-bonded interactions with PDE9 in different metal systems.

| S-EPMC8151263 | biostudies-literature

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