Catalytic Oxidation Of Benzyl Alcohol Research Articles

Syntheses and molecular structures of novel Ru(II) complexes with bidentate benzimidazole based ligands and their catalytic efficiency for oxidation of benzyl alcohol

Five bidentate ligands derived from quinoline-2-carboxylic acid, i.e. 2-(1H-benzimidazol-2-yl)quinoline (L1), 2-(1-benzyl-1H-benzimidazol-2-yl)quinoline (L2), 2-[1-(2,3,5,6-tetramethylbenzyl)-1H-benzimidazol-2-yl]quinoline (L3), 2-[1-(4-chlorobenzyl)-1H-benzimidazol-2-yl]quinoline (L4), and 2-[1-(4-methylbenzyl)-1H-benzimidazol-2-yl]quinoline (L5) were synthesized. Treatment of L1-5 with [RuCl2(p-cymene)]2 and KPF6 afforded six-coordinate piano-stool Ru(II) complexes, namely, [RuCl(L1)(p-cymene)]PF6 (C1), [RuCl(L2)(p-cymene)]PF6 (C2), [RuCl(L3)(p-cymene)]PF6 (C3), [RuCl(L4)(p-cymene)]PF6 (C4), and [RuCl(L5)(p-cymene)]PF6 (C5). Synthesized compounds were characterized with different techniques such as 1H and 13C NMR, FT-IR, and UV–vis spectroscopy. The solid state structure of L1 and C3 was confirmed by single-crystal X-ray diffraction analysis. The single crystal structure of C3 verified coordination of L3 to the Ru(II) center. The Ru(II) center has a pseudo-octahedral three legged piano stool geometry. The complexes C1-5 were tested as catalysts for the catalytic oxidation of benzyl alcohol to benzaldehyde in the presence of periodic acid (H5IO6) (Substrate/Catalyst/Oxidant = 1/0.01/0.5). The best result was obtained with C2 (3 h→90%).

Selective Catalytic Oxidation of Benzyl Alcohol and Characterization Studies of Spinel MnAl<SUB>2</SUB>O<SUB>4</SUB> Nanoparticles by a Facile Synthesis Route

Spinel MnAl2O4 nanoparticles were prepared effectively by simplistic, economical microwave heating method (MHM) using Opuntia dillenii extract as reducing agent. The samples were successfully characterized by powder XRD pattern, EDX spectra, FT-IR analysis, HR-SEM analysis, and VSM instrumentation techniques. Powder XRD, EDX and FT-IR results demonstrated that the products contain a pure single-phase spinel structure lacking of other secondary phase impurities. HR-SEM results confirmed the spherical shaped nanoparticle morphology of the sample. Magnetic characterization property was confirmed by VSM analysis. VSM hysteresis loop established the superparamagnetism of the sample and the magnetization (Ms value of MnAl2O4 is 0.023 emu/g. It was found that MnAl2O4 nanoparticle is highly active towards the selective oxidation of benzyl alcohol into benzaldehyde at a low temperature with very high yield, due to the higher surface area and number of active sites.

Highly selective copper‐catalyzed oxidation of benzyl alcohols to aromatic aldehydes in water at room temperature

Water‐soluble 2N2O–Cu(II) complexes were synthesized and used for the catalytic oxidation of benzylic alcohols to the corresponding aldehydes in pure water resulting in high yields of up to 94%. Importantly, the catalytic system exhibits a wide substrate scope, high functional group tolerance and can be reused directly for subsequent reaction cycles. Using this catalytic system, the product 4‐methylbenzaldehyde can be produced on a multi‐gram scale and in the complete absence of any organic solvent, surfactant or phase transfer reagent. Copyright © 2016 John Wiley & Sons, Ltd.

Dicopper Complexes with Anthyridine-Based Ligands: Coordination and Catalytic Activity

Two new anthyridine-based ligands, 5-phenyl-2,8-bis(2-pyridinyl)-1,9,10-anthyridine (L3) and 5-phenyl-2,8-bis(6′-bipyridinyl)-1,9,10-anthyridine (L4), were designed for accommodation of dimetallic systems with the metal ions separated by ∼5 A. Complexation of Cu(ClO4)2 with L3 and L4 provided the corresponding dicopper complexes [{Cu2(L3)(H2O)4(CH3CN)2}(ClO4)4] (3) and [{Cu2(L4)(μ-ClO4)2}(PF6)2] (4), respectively. Both complexes were characterized by spectroscopic methods, and the detail structural features were further confirmed by X-ray crystallography. Structural analyses of 3 and 4 reveal the Cu···Cu distances in the complexes being 4.9612(7) and 5.013 (2) A, respectively. Both complexes are active in the catalytic oxidation of benzyl alcohols into the corresponding aldehydes. Furthermore, complex 4 appears to be a good catalyst for the oxidative coupling of primary alcohols into the corresponding esters with the use of hydrogen peroxide as the oxidant in an aqueous medium. The possible cooperative in...

Synthesis of cross-linked copolymers of the (3-(2-pyridyl) acrylic acid)–copper(ii) complex in supercritical carbon dioxide for the catalytic oxidation of benzyl alcohol

The copper(ii) complexes of poly[(3-(2-pyridyl) acrylic acid)-co-acrylic acid] {P(Pya-co-AA)} were prepared via precipitation polymerization in supercritical carbon dioxide.

Aloe vera Plant Extracted Green Synthesis, Structural and Opto-Magnetic Characterizations of Spinel Co(x)Zn₁₋xAl₂O₄Nano-Catalysts.

Spinel Co(x)Zn₁₋xAl₂O₄ (0 ≤ x ≤ 1) nano-catalysts were synthesized by a simple Aloe vera plant extracted green synthesis route. Powder XRD patterns and Rietveld analysis confirmed the formation of single phase, cubic spinel gahnite structure without other impurities. The lattice parameter increased from 8.089 to 8.125 A with increasing CO²⁺ content. The average crystallite sizes were estimated using Scherrer's method, and it was found to be in the range of 15.72 nm to 26.53 nm. FT-IR spectra showed vibrational stretching frequencies corresponding to the spinel structure. HR-SEM and HR-TEM images showed the features of well particle shaped crystals with nano-sized grains. The elemental compositions of Co, Zn, Al and O were quantitatively obtained from EDX analysis. The band gap energy estimated using Kubelka-Munk method by UV-Visible DRS method, and the values are decreased with increasing the Co²⁺ content (4.12 eV to 3.67 eV), due to the formation of sub bands in between the energy gap. PL spectra showed emission bands in UV as well as in the visible regions for ZnAl₂O₄ and Co-doped ZnAl₂O4, due to the defect centers acting as the trap levels. VSM measurements revealed that pure ZnAl₂O₄ has diamagnetic, while Co doped ZnAl₂O₄ samples (x = 0.2 to 0.8) have superparamagnetism, whereas the sample CoAl₂O₄ has ferromagnetic in nature. Catalytic oxidation of benzyl alcohol to benzaldehyde was found that the sample Co₀.₆Zn₀.₄Al₂O₄ showed 93.25% conversion with 99.56% selectivity, whereas for pure ZnAl₂O₄, the conversion was only 86.31% with 92.85% selectivity.

N-doped ordered mesoporous carbon supported PdCo nanoparticles for the catalytic oxidation of benzyl alcohol

A highly ordered nitrogen doped mesoporous carbon was prepared by passing acetonitrile as carbon and nitrogen source over a mesoporous SBA-15 silica template at 900 °C by using a CVD bubbling method. The silica template was removed by etching with HF, followed by filtration, washing and functionalization with HNO3 to give N-CMK-3 (N = 11.3 wt%). This material exhibited good mesostructural ordering (XRD analysis), a high surface area (885 m2/g) and a large pore volume (1.70 cm3/g). Addition of a monodispersed colloidal solution of PdCo (d = 3.3 nm), Pd (4.2 nm) or Co (10.5 nm) nanoparticles to N-CMK-3 as support gave highly uniform and well dispersed nano-sized Pd, PdCo and Co nanoparticle supported catalysts. The synthesized catalysts were activated with H2 (5%)/Ar at 400 °C to remove capping agents. These activated PdCo, Pd and Co/N-CMK-3 catalysts were tested for benzyl alcohol oxidation under solvent free conditions using oxygen as an oxidant at different temperatures (110–140 °C) and times (1–8 h) and compared with an equivalent carbon (Vulcan XC-72) supported catalyst. In the aerobic oxidation of alcohols, the PdCo/N-CMK-3 showed similar activity to the Pd/N-CMK-3 catalyst but only using 50% of the amount of Pd in a PdCo catalyst. An important role of Co is to reduce the bulk Pd content of the catalyst. This can be explained by a core-shell structure for the PdCo catalyst. The catalytic oxidation of a range of benzyl alcohols (no solvent, O2 as oxidant, 130 °C) in the presence of PdCo/N-CMK-3 typically gave aldehydes with conversions in the range 87–99% (selectivity 99%) after 5 h. The catalyst also retained its selectivity and activity after four recycles.

Continuous Heterogeneously Catalyzed Oxidation of Benzyl Alcohol in a Ceramic Membrane Packed-Bed Reactor

A ceramic membrane reactor was investigated for the continuous catalytic oxidation of benzyl alcohol with oxygen. The reactor had a concentric configuration. An inner tube created an annulus for the catalyst packed-bed (0.9 wt % Au− Pd/TiO2, particle size 90−125 μm) through which the liquid phase (benzyl alcohol, neat or dissolved in o-xylene) flowed. This was followed by the tubular ceramic membrane, which consisted of layers of alumina and a zirconia top layer with a nominal average pore size of 50 nm. The role of the membrane was to provide an interface for gas and liquid to come in contact. Pure oxygen was fed to the opposite side of the membrane in the outer shell of the reactor. Temperature affected conversion but not selectivity, possibly because of insufficient supply of oxygen. However, increasing catalyst contact time or decreasing benzyl alcohol concentration improved selectivity and conversion, indicating that a key parameter was the balance between oxygen supply by the membrane vs oxygen demand by the reaction. By adjusting the operating parameters, reaction performance improved. Selectivity to benzaldehyde 88% and conversion of benzyl alcohol 75% were obtained at 3.2 bara of gas pressure, 24444 gcat·s/galcohol catalyst contact time, 0.5 M benzyl alcohol concentration, and temperature of 120 °C. This performance was comparable to simulated trickle bed operation, where oxygen and substrate were premixed before entering the catalyst packed bed. The membrane reactor offers safer operation, since flammable oxygen/organic mixtures formed in the trickle bed are avoided.

Erratum to: Antimicrobial, free radical scavenging activities and catalytic oxidation of benzyl alcohol by nano-silver synthesized from the leaf extract of Aristolochia indica L.: a promenade towards sustainability

Erratum to: Antimicrobial, free radical scavenging activities and catalytic oxidation of benzyl alcohol by nano-silver synthesized from the leaf extract of Aristolochia indica L.: a promenade towards sustainability

Antimicrobial, free radical scavenging activities and catalytic oxidation of benzyl alcohol by nano-silver synthesized from the leaf extract of Aristolochia indica L.: a promenade towards sustainability

Silver nanoparticles (Ag-NPs) were synthesized from aqueous silver nitrate through a simple route using the leaf extract of Aristolochia indica L. (LAIL) which acted as a reducing as well as capping agent. X-ray diffraction confirmed that the synthesized silver particles have a face centred cubic structure. EDS predicted the presence of elemental silver. The SEM images showed the synthesis of spherically mono-dispersed particles, with nano dimensions accounted by the TEM images. Infra-red spectrum adopted to the different organic functionalities present at the surface of the particles. TGA indicated an overall 11 % weight loss up to 1000 °C, suggesting desorption of biomolecules from the surface. X-ray photoelectron spectroscopy (XPS) analysis revealed the presence of metallic silver nanoparticles. The prepared material was utilized as catalyst in the oxidation of benzyl alcohol with molecular oxygen as the oxidant in methanol, under ambient conditions of temperature and pressure. Also Ag-NPs showed good to moderate anti-microbial activity employing the Agar disc diffusion method against various strains using Ciprofloxacin and Fluconazole as standard. Free radical scavenging activity of the nanoparticles were observed by modified 1,1-diphynyl-2-picrylhydrazyl, DPPH and 2,2-azinobis(3-ethylbenzothiazoline-6-sulfonic acid), ABTS in vitro assays. The work presented here demonstrates the adaptability of the synthesized Ag-NPs in participating as a disinfectant agent, free radical scavenger and an effective oxidation catalyst. The basic premise of attaining sustainability through the green synthesis of smart multifaceted materials has been consciously addressed.

Synthesis, characterization, DNA binding and catalytic applications of Ru(III) complexes

A new series of azodye ligands 5-chloro-3-hydroxy-4-(aryldiazenyl)pyridin-2(1H)-one (HLn) were synthesized by coupling of 5-chloro-3-hydroxypyridin-2(1H)-one with aniline and its p-derivatives. These ligands and their Ru(III) complexes of the type trans-[Ru(Ln)2(AsPh3)2]Cl were characterized by elemental analyses, IR, 1H NMR and UV–Visible spectra as well as magnetic and thermal measurements. The molar conductance measurements proved that all the complexes are electrolytes. IR spectra show that the ligands (HLn) acts as a monobasic bidentate ligand by coordinating via the nitrogen atom of the azo group (NN) and oxygen atom of the deprotonated phenolic OH group, thereby forming a six-membered chelating ring and concomitant formation of an intramolecular hydrogen bond. The molecular and electronic structures of the investigated compounds (HLn) were also studied using quantum chemical calculations. The calf thymus DNA binding activity of the ligands (HLn) and their Ru(III) complexes were studied by absorption spectra and viscosity measurements. The mechanism and the catalytic oxidation of benzyl alcohol by trans-[Ru(Ln)2(AsPh3)2]Cl with hydrogen peroxide as co-oxidant were described.

Catalytic oxidation of benzyl alcohol over manganese oxide supported on MCM-41 zeolite

Potassium permanganate, nitrate and acetate acid precursors of manganese were used to as precursors of manganese to prepare dispersed manganese oxides on MCM-41 catalysts (MnOx/MCM-41), in order to compare the structure and activity. MnOx/MCM-41 were synthesized by impregnation method and calcined at different temperatures. The catalytic properties of these materials were investigated for the oxidation of benzyl alcohol using hydrogen peroxide as oxygen source. Catalysts were characterized by X-ray diffraction, N2 adsorption, H2 temperature programmed reduction, X-ray photoelectron spectroscopy and UV–Vis diffuse reflectance spectra. It was observed that the varieties of manganese precursors and calcination temperature affect the oxidation state and reducibility of MnOx, which play significant role in the catalytic process. The catalysts prepared from the potassium permanganate and acetate precursors exhibited the outstanding catalytic activity, which could be related to the reducibility of the surface Mnδ+ oxo species. It was found that the Mn4+ and Mn3+ oxo species present a higher intrinsic activity than that of Mn2+ oxo species.

Continuous Heterogeneously Catalyzed Oxidation of Benzyl Alcohol Using a Tube-in-Tube Membrane Microreactor

A Teflon AF-2400 tube-in-tube microreactor is investigated for the continuous, solvent-free, catalytic oxidation of benzyl alcohol with oxygen. The semipermeable Teflon AF-2400 tube acts as the interface between the gaseous oxidant and the liquid substrate. Because of the inherent safety of this contacting method, the use of pure oxygen is possible. The semipermeable tube was packed with 1 wt % Au–Pd/TiO2 catalyst particles and placed inside a PTFE tube to provide an annular region which was pressurized with pure oxygen. This design allowed continuous penetration of oxygen through the inner tube during the reaction, resulting in higher oxygen concentration in the catalyst bed and significantly improved conversion compared to a reactor operating with an oxygen presaturated feed. The amount of oxygen available for reaction in the tube-in-tube microreactor was 2 orders of magnitude higher than that in a nonpermeable reactor with oxygen presaturated feed. The semipermeable tube reactor performance in terms of both conversion and selectivity was enhanced by increasing the gas pressure, the catalyst contact time and by dilution of the catalyst. The highest conversion of benzyl alcohol obtained for the range of conditions investigated was 44.1%, with 73.0% selectivity to benzaldehyde, at 120 °C; catalyst contact time, 115 gcat·s/galcohol; and catalyst dilution factor, 4.

DFT study on the reaction mechanisms behind the catalytic oxidation of benzyl alcohol into benzaldehyde by O2 over anatase TiO2 surfaces with hydroxyl groups: Role of visible-light irradiation

Theoretical study on the catalytic oxidation of benzyl alcohol by molecular oxygen (O2) on the TiO2 surface was performed by DFT calculations. The anatase TiO2 crystal faces in the absence and presence of surface hydroxyl groups were modeled with a slab of Ti16O32 and Ti16O32(OH)H, respectively. The interaction of benzyl alcohol with Ti16O32 and Ti16O32(OH)H was calculated. It was clearly demonstrated that the surface hydroxyl groups on the TiO2 surface play a significant role in the formation of the alkoxide ([Ti]OCH2−ph) species. The orbitals of the alkoxide species was found to be hybridized with the O2p orbital in the valence band (VB) of the TiO2. The origin of the visible-light response in the photocatalytic system can be attributed to the electronic transition from the donor levels created by the alkoxide species to the conduction band (CB). Furthermore, reaction coordinates in the overall catalytic reaction of benzyl alcohol into benzaldehyde on the TiO2 surface were demonstrated, and the role of the visible-light irradiation was also discussed.

Factors influencing the catalytic oxidation of benzyl alcohol using supported phosphine-capped gold nanoparticles

The nature of Au cluster precursor and activation treatments affect catalyst activity in aerobic benzyl alcohol oxidation.

Preparation of Nano-Manganite Loaded Titanium Electocatalytic Membrane for the Catalytic Oxidation of Benzyl Alcohol

Preparation of Nano-Manganite Loaded Titanium Electocatalytic Membrane for the Catalytic Oxidation of Benzyl Alcohol

Studies on the roles of vanadyl sulfate and sodium nitrite in catalytic oxidation of benzyl alcohol with molecular oxygen

An efficient catalytic system consisting of vanadyl sulfate/sodium nitrite was disclosed previously for the oxidation of benzylic alcohols into aldehydes with molecular oxygen. However, the roles of catalyst components were not investigated. In this paper, we examined catalytic oxidation of benzyl alcohol as a model reaction, especially by infrared spectroscopy. The role of each component is discussed including nitrite, vanadyl, sulphate, and water. Sodium nitrite could be converted into nitrate and nitric acid. The vanadium(IV) could be smoothly oxidized into vanadium(V) under mild and acidic conditions without any organic ligands. The transformation of sulfate and bisulfate, the cessation of an induction period, and the oxidation of benzyl alcohol were closely interrelated. The multiple roles of water are discussed, including reduction of the induction period, participation in redox cycles of nitric compounds, deactivation of vanadium, and as a byproduct of oxidation. This study contributes to further development of aerobic oxidation using vanadium based catalysts.

One-Pot Flash Combustion Synthesis, Structural, Morphological and Opto-Magnetic Properties of Spinel Mn x Co1−x Al2O4 (x = 0, 0.3, and 0.5) Nanocatalysts

Spinel Mn x Co1−xAl2O4 (x = 0, 0.3, and 0.5) nanoparticles were synthesized by a simple microwave-assisted combustion method. Powder X-ray diffraction (XRD) analysis was confirmed the formation of single phase, cubic spinel structure without other impurities. Average crystallite sizes of the samples were found to be in the range of 10.12 nm to 1623 nm by Scherrer’s method. FT-IR spectra showed the stretching frequencies corresponding to the M–Al–O bond of spinel structure. High-resolution scanning electron microscope (HR-SEM) and high-resolution transmission electron microscope (HR-TEM) images showed the particle-like nanostructures. Band gap energy was estimated using UV-Visible DRS spectra and the values are increased with increasing Mn2+ content (345 eV to 3.75 eV). Vibrating sample magnetometer (VSM) measurements revealed that pure and Mn-doped CoAl2O4 samples have ferromagnetic behavior and the magnetization values increased with increasing the concentration of Mn2+ ions in the CoAl2O4lattice. Catalytic oxidation of benzyl alcohol into benzaldehyde was found that the sample Mn0.5Co0.5Al2O4showed 96.58 % conversion with 100 % selectivity, whereas pure CoAl2O4, the conversion was only 87.43 % with 100 % selectivity.

Introducing Potential Hemilability into “Click” Triazoles and Triazolylidenes: Synthesis and Characterization of d6‐Metal Complexes and Oxidation Catalysis

AbstractHemilabile ligands are known to impart remarkable properties to their metal complexes. Herein, we present arene half‐sandwich complexes of RuII, OsII, and IrIII with “click”‐derived 1,2,3‐triazole (L1) and 1,2,3‐triazol‐5‐ylidene (L2) ligands containing a potentially hemilabile thioether donor. Structural elucidation of the complexes revealed localization of double bonds within the triazole in L1 and a delocalized situation within the triazolylidene ring of L2. For complexes with L1, unusual coordination occurs through the less basic nitrogen “N2” of the 1,2,3‐triazole. All complexes were applied for the catalytic oxidation of benzyl alcohol to benzaldehyde using N‐methylmorpholine N‐oxide as sacrificial oxidant. Furthermore, oxidation of diphenylmethanol to benzophenone was also achieved by using low catalyst loadings in very good yields. These are rare examples of OsII–triazole, as well as of OsII–triazolylidene complexes with “click”‐derived ligands.

Nanostructured copper aluminate spinels: Synthesis, structural, optical, magnetic, and catalytic properties

Copper aluminate nanostructured materials were synthesized by a microwave combustion method (MWCM) using the plant extract (aloe vera) as a fuel without using any other template or surfactant. For comparison, it was also prepared by using the conventional combustion method (CCM). The as-synthesized copper aluminate was characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), high resolution scanning electron microscopy (HR-SEM), energy dispersive X-ray analysis (EDX), diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy, nitrogen adsorption/desorption isotherms, and vibrating sample magnetometer (VSM). The results indicated that the copper aluminate nanomaterials obtained by MWCM shows good crystallinity with the uniform size distribution than the ones prepared by CCM. The XRD and FT-IR results confirmed the crystal structure of copper aluminate. The formation of copper aluminate nano- and microstructures were confirmed by HR-SEM. The optical absorption and photoluminescence emissions were determined by DRS and PL spectra, respectively. The effect of the catalyst and the oxidant on the catalytic oxidation of benzyl alcohol was also investigated.