Oxidation Of Alcohols In Water Research Articles

New reaction pathway induced by N-deficient conjugated polymer-supported bimetallic oxide quantum dot S-scheme heterojunction for benzyl alcohol oxidation in water

The catalytic conversion of aromatic alcohols to their corresponding carbonyls under mild conditions is challenging because of their low selectivity and activity. A 0D/2D based S-scheme heterojunction material with bimetallic oxide quantum dots (NixFe1-xO QD) and nitrogen-deficient conjugated polymers, such as g-C3N4 (NvCN), was designed for the photocatalytic conversion of benzyl alcohols to benzaldehyde/benzoic acid using simulated solar light. The optimized Ni0.5Fe0.5O QD/NvCN (NFO/NvCN) hybrid catalyst exhibited excellent conversion (85%) and selectivity (98%) for photocatalytic oxidation of benzyl alcohol (BzOH) to benzaldehyde (BzH) in an aqueous medium (88%) and for benzoic acid (BzA) under dilute alkaline conditions (99%). The structure-activity relationship was established using catalytic activity data, surface physicochemical characteristics, optoelectronic characteristics, and scavenging studies. The band alignment of the heterojunction converts the type-I junction into a type-II junction and follows S-scheme charge dynamic pathways through the nitrogen vacancy pathways, which can accelerate the separation and transfer of photogenerated charge carriers. Mechanistic pathways have been proposed based on O–H bond cleavage by electrons and C–H bond cleavage by holes. Hybrid materials based on defect-rich supports and bimetallic oxide-quantum dot interactions are promising catalysts that can compete with the best photocatalysts.

Thermo-responsive polymer-based catalytic nanoreactors for controllable catalysis of selective oxidation of alcohols in water

The study showcases a thermo-responsive polymer-based nanoreactor for controllable catalysis by “opening” and “closing” of the transport channel of water-soluble reactants.

Gold nanoparticles supported on carbon coated magnetic nanoparticles; a robustness and effective catalyst for aerobic alcohols oxidation in water

Three kinds of gold nanoparticles supported by carbon-coated magnetic nanoparticles were prepared using distinct reduction processes and appropriate quantities of carbon support. Among them, an active and magnetically recoverable catalyst known as Fe3O4@C@Au(H) was instrumental in the aerobic oxidation of alcohols in water, where it produced carbonyl compounds with high selectivities without the formation of any carboxylic acids in the case of primary alcohol. The recovered Au catalyst can be used efficiently and quickly in ten successive runs without a noteworthy decrease in activity and, simply isolated from the water by using an external magnetic at the end of the process. In particular, the possibility to carry out the reaction in water, and simultaneously, the straightforward protocol for recycling via the easy and rapid separation method makes this catalytic system a credible candidate towards the target of green chemistry.

Heterogenization of Phosphotungstate Clusters into Magnetic Microspheres: Catalyst for Selective Oxidation of Alcohol in Water

Heterogenization of Phosphotungstate Clusters into Magnetic Microspheres: Catalyst for Selective Oxidation of Alcohol in Water

Unsymmetrical PEG-substituted tris(triazolyl)amines as bi-functional surfactants for copper-catalyzed aerobic oxidation of alcohols in water

Unsymmetric tris(triazolyl)amine surfactants with mPEG550 and mPEG2000 substituents efficiently promote copper-catalyzed alcohol oxidation in water.

Selective iron-catalyzed aerobic oxidation of alcohols in water to carboxylic acids mediated by additives

The iron catalyst (POM-Fe) could combine with chloride ions to form a supramolecular aggregate FeMo6·Cl, which was used in the oxidation of alcohols to carboxylic acids under mild conditions and can tolerate 40 substrates with moderate to high yield.

TEMPO-Functionalized Nanoreactors from Bottlebrush Copolymers for the Selective Oxidation of Alcohols in Water.

Polymeric nanoreactors in water fabricated by the self-assembly of amphiphilic copolymers have attracted much attention due to their good catalytic performance without using organic solvents. However, the disassembly and instability of relevant nanostructures often compromise their potential applicability. Herein, the preparation of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-containing nanoreactors by the self-assembly of amphiphilic bottlebrush copolymers has been demonstrated. First, a macromonomer having a norbornenyl polymerizable group was prepared by RAFT polymerization of hydrophobic and hydrophilic monomers. The macromonomer was further subjected to ring-opening metathesis polymerization to produce an amphiphilic bottlebrush copolymer. Further, TEMPO, as a catalyst, was introduced into the hydrophobic block through the activated ester strategy. Finally, TEMPO-functionalized polymeric nanoreactors were successfully obtained by self-assembly in water. The nanoreactors exhibited excellent catalytic activities in selective oxidation of alcohols in water. More importantly, the reaction kinetics showed that the turnover frequency is greatly increased compared to that of the similar nanoreactor prepared from liner copolymers under the same conditions. The outstanding catalytic activities of the nanoreactors from bottlebrush copolymers could be attributed to the more stable micellar structure using the substrate concentration effect. This work presents a new strategy to fabricate stable nanoreactors, paving the way for highly efficient organic reactions in aqueous solutions.

Catalytic study of the copper-based magnetic nanocatalyst on the aerobic oxidation of alcohols in water

Catalytic study of the copper-based magnetic nanocatalyst on the aerobic oxidation of alcohols in water

Ultrasmall amphiphilic zeolitic nanoreactors for the aerobic oxidation of alcohols in water.

Organic reactors in a green solvent (water) is the goal of sustainable development. Green nanoreactors with excellent amphiphilicity and catalytic activity are strongly desired. Herein, a novel amphiphilic nanoreactor Pd@amZSM-5 with ultrasmall size has been successfully synthesized via a simple one-step oil bath method, subjected to the modification-etching-modification strategy and in situ reduction of Pd2+. Ultrasmall Pd@amZSM-5 nanoreactors (60 nm) with hierarchical structures showed outstanding amphiphilicity for forming Pickering emulsions with fine uniform droplets (50 μm). Fine droplets formed short diffusion distances, which can significantly improve the catalytic activity in biphasic reactions. Moroever, the ultrasmall Pd@amZSM-5 nanoreactors demonstrated excellent catalytic activity for the selective oxidation of alcohols in water using air as the oxidant. Alkali was not present in the reaction system. The hydrophilic aminopropyl groups on the surface of the Pd@amZSM-5 nanoreactors not only changed the affinity of the zeolite surface and provided targeting points for Pd nanoparticles but also provided an alkaline environment for the selective oxidation of alcohols. The ultrasmall Pd@amZSM-5 nanoreactors presented excellent universality for aromatic alcohols (with >90% conversion and >90% selectivity) and allylic alcohols (with 100% conversion and 100% selectivity).

Mesoporous Silica Nanoparticles Supported Atomically Precise Palladium Nanoclusters Catalyzed Aerobic Oxidation of Alcohols in Water

The first mesoporous silica nanoparticles (MSNs) supported atomically precise palladium nanoclusters catalyzed alcohol oxidation reactions in water have been achieved. The catalysts was synthesized with simple impregnation method and well characterized by TEM, FT-IR, XPS anddiffuse reflectance optical spectrum and the results proved that the Pd nanoclustersimmobilized into the pores of MSNs.The as-prepared catalyst show excellent activity for the alcohol oxidation reactions with high yield under extremely mild aqueous conditions utilizes 1 atmosphere of molecular oxygen as sole oxidant. The features of clean system, gram-scale oxidation and easy recovery catalyst make this method cost effectively and environmentally benign.

Mesoporous Silica Nanoparticles Supported Atomically Precise Palladium Nanoclusters Catalyzed Aerobic Oxidation of Alcohols in Water

The first mesoporous silica nanoparticles (MSNs) supported atomically precise palladium nanoclusters catalyzed alcohol oxidation reactions in water have been achieved. The catalysts was synthesized with simple impregnation method and well characterized by TEM, FT-IR, XPS anddiffuse reflectance optical spectrum and the results proved that the Pd nanoclustersimmobilized into the pores of MSNs.The as-prepared catalyst show excellent activity for the alcohol oxidation reactions with high yield under extremely mild aqueous conditions utilizes 1 atmosphere of molecular oxygen as sole oxidant. The features of clean system, gram-scale oxidation and easy recovery catalyst make this method cost effectively and environmentally benign.

Synergistic catalysis within core-shell Fe3O4@SiO2 functionalized with triethylene glycol (TEG)-imidazolium ionic liquid and tetramethylpiperidine N-oxyl (TEMPO) boosting selective aerobic oxidation of alcohols

HypothesisIt is expected that incorporation of 2, 2, 6, 6-tetra-methyl piperidine-N-oxyl radical (TEMPO) and an imidazolium bromide bearing hydrophilic triethylene glycol (TEG) groups on Fe3O4@SiO2 core–shell may not only result in a novel highly water-dispersible/magnetically separable multi-functional catalyst system for metal-free aerobic oxidation of alcohols, which operates through a synergistic relay pathway, but it could potentially provide a strong platform for simultaneous separation and recycling of all components. ExperimentsThe catalyst was prepared by anchoring TEMPO moieties onto a magnetic core–shell Fe3O4@SiO2 functionalized with an ionic liquid bearing TEG groups. The materials was characterized using transmission electron microscopy, Fourier transform infrared spectroscopy, nitrogen adsorption–desorption isotherms, thermal gravimetric analysis, and elemental analysis. The performance of the catalyst was evaluated and quantitatively measured in the aerobic oxidation of alcohols in water. FindingsThe catalyst exhibited excellent and stable colloidal dispersion in water and high performance in the aerobic oxidation of various types of alcohols under metal- and halogen-free reaction conditions. As hypothesized, strong synergistic effect between functionalized components was seen in the described reaction. The catalyst displayed excellent dual-adjustable-selectivity in the oxidation of primary alcohols to either the corresponding aldehydes or carboxylic acids by tuning the reaction solvent and/or reaction time and excellent recycling behavior through a “double-separation-strategy”.

Dual Stimuli-Responsive Copper Nanoparticles Decorated SBA-15: A Highly Efficient Catalyst for the Oxidation of Alcohols in Water

In the present work, a temperature and pH-responsive hybrid catalytic system using copolymer-capped mesoporous silica particles with metal nanoparticles is proposed. The poly(2-(dimethylamino)ethyl methacrylate)(DMAEMA)-co-N-tert-butyl acrylamide) (TBA)) shell on mesoporous silica SBA-15 was obtained through free radical polymerization. Then, copper nanoparticles (CuNPs) decorated SBA-15/copolymer hybrid materials were synthesized using the NaBH4 reduction method. SBA-15 was functionalized with trimethoxylsilylpropyl methacrylate (TMSPM) and named TSBA. It was found that the CuNPs were uniformly dispersed in the mesoporous channels of SBA-15, and the hybrid catalyst exhibited excellent catalytic performance for the selective oxidation of different substituted benzyl alcohols in water using H2O2 as an oxidant at room temperature. The dual (temperature and pH-) responsive behaviors of the CuNPs/p(DMAEMA-co-TBA)/TSBA catalyst were investigated using the dynamic light scattering technique. The conversion of catalytic products and selectivity were calculated using gas chromatographic techniques, whereas the molecular structure of the products was identified using 1H and 13C nuclear magnetic resonance (NMR) spectroscopy. The catalyst showed excellent catalytic activity toward the oxidation of alcohol to aldehyde in an aqueous medium below the lower critical solution temperature (LCST) and pKa values (7–7.5) of the copolymer. The main advantages of the hybrid catalyst, as compared to the existing catalysts, are outstanding alcohol conversion (up to 99%) for a short reaction time (1 h), small amount of the catalyst (5 mg), and good recyclability equal to at least five times.

Tungstate ion (WO42-) confined in hydrophilic/hydrophobic nanomaterials functionalized brönsted acidic ionic liquid as highly active catalyst in the selective aerobic oxidation of alcohols in water

A Brönsted acidic Ionic Liquid containing tungstate anion functionalized polysiloxane network (PMO-IL-WO42-) was synthesized by simple self-condensation of tungstic acid and zwitterionic organosilane precursor possessing both imidazolium and sulfonate groups. Characterization by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), thermal gravimetric analysis TGA, nitrogen porosimetry, solid-state NMR spectroscopy and elemental analysis confirmed that both imidazolium cation and tungstate anion of zwitterion are successfully incorporated inside the organosilica framework. The catalytic activity of resulting hybrid PMO-IL- WO42- material was studied in the selective aerobic oxidation of primary and secondary alcohols using an atmospheric pressure of air in pure water. Due to the ionic liquid-based charged surface containing hydrophilic sulfonic acid and tungstate group, the synergistic hydrophilic/hydrophobic and redox effect of PMO-IL-WO42- as water-friendly catalyst facilitates and enhances the activity and selectivity toward the target oxidative products in water and proved to have a particularly broad substrate scope for reliable aerobic oxidation reaction. Furthermore, the catalyst showed outstanding stability and could be easily separated and reused at least ten reactions run under the same conditions as fresh catalyst without any loss of catalytic activity and product selectivity.

Cubic nanocasted polyaniline-ordered mesoporous carbon composite and its application for enhanced catalytic activity of palladium nanoparticles in the aerobic oxidation of alcohols in water

A novel polyaniline-ordered mesoporous carbon composite (PANI/OMC) was prepared through a two-step nanocasting technique in the presence of KIT-6 as template. The material exhibits high surface area, accessible mesoporous structure as well as improved basicity and redox potential arising from the presence of polyaniline as a nitrogen-containing polymer. It was successfully used as an effective support for preparation of a Pd nanoparticle (Pd NPs) supported catalyst (Pd@PANI/OMC), which was then employed as a powerful catalyst in the aerobic oxidation of primary alcohols, affording the corresponding carboxylic acids in good to excellent yields in pure water. This excellent catalytic performance can be attributed to the synergism of the large surface area and highly dispersed Pd NPs derived from the extraordinary features of the support. Morphology, structure, and composition of the materials were characterized by N2 adsorption–desorption analysis, electron microscopy (TEM, SEM), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and Fourier-transform infrared spectroscopy (FT-IR).

Oxidation of Alcohols in Water on a Mesoporous Polypyrrole/Carbon-Supported Palladium Catalyst

Oxidation of Alcohols in Water on a Mesoporous Polypyrrole/Carbon-Supported Palladium Catalyst

Zinc substituted Keggin-type polyoxometalate on Dowex: a green heterogeneous catalyst for oxidation of alcohols in water

In this work, homogeneous and heterogeneous oxidation of alcohols by H2O2 in the presence of [(n-C4H9)4 N]5[PW11ZnO39].3H2O and [PW11ZnO39]5− supported on Dowex 22 as catalysts have been investigated. Using water as a green solvent, different alcohols were converted into the corresponding aldehydes and ketones in high to excellent yields. Dowex 22 supported polyoxometalate, PW11Zn@Dowex, was also catalyzed highly robust and selective oxidation of unsaturated alcohols. Leaching and recycling experiments on supported catalyst revealed the excellent stability and reusability of this catalytic system.

Proton-Coupled Electron Transfer Catalyst: Homogeneous Catalysis. Application to the Catalysis of Electrochemical Alcohol Oxidation in Water

Proton-coupled electron transfer (PCET) catalysts are investigated in the framework of cyclic voltammetry (CV). We analyze homogeneous catalysts and provide a detailed formal kinetic analysis of the various responses expected in the case of a PCET catalyst following either stepwise or concerted pathways. Both buffered solution and nonbuffered aqueous media are considered. In the first case we show that, in addition to possible limitation by buffer diffusion, the PCET sequence may be rate limiting. The CV wave shape, position, and intensity are discussed in terms of thermodynamic and kinetic penalties associated with each mechanism. In the second case, we show that a nonclassical pseudo-canonical cyclic voltammogram with hysteresis due to hydronium production is obtained for a Nernstian PCET catalyst with water as the proton acceptor. Thermodynamic and kinetic penalties resulting from water-based PCET specific pathways are analyzed. Finally, we use the present analysis to investigate the electrochemical catalysis of alcohol oxidation in water with a PCET catalyst, N-hydroxyphthalimide. We have found that the rate constant for benzyl alcohol oxidation is independent of pH, strongly suggesting a true hydrogen atom transfer (HAT) as the rate-determining step. When water is the proton acceptor to generate the active form of the catalyst, i.e. N-oxyl PINO radical, the catalytic process follows a stepwise PTET pathway whose kinetics partially limits the catalytic current.

Green synthesis of Pd@rGO nanocomposite using Piper (Piper nigrum) leaf extract and its catalytic activity towards alcohol oxidation in water at room temperature

A simple in situ methodology for the green synthesis of palladium decorated reduced graphene oxide (Pd@rGO) nanocomposite using green leaf extract of Piper plant (Piper nigrum) has been described. The one-pot synthetic method uses no external stabilizer. The obtained nanocomposite has very low Pd loading (0.012 mol % of Pd), and the size of the nanoparticles anchored in rGO sheets ranged between 6 to 20 nm. The as-synthesized nanocomposite was characterized by FT-IR, UV–vis, TGA, XRD, TEM, EDX, BET surface area measurement, and ICP-AES analysis. The Pd@rGO nanocomposite showed profound catalytic activity for the selective oxidation of primary as well as secondary alcohol in water at room temperature. It is worth noting that, under the optimal condition, it is equally useful for the oxidation of usually nonreactive alcohols like cyclohexanol, nonanol, furfuryl alcohol, etc. The catalyst showed excellent recyclability up to 5th cycles without significant loss of catalytic activity.

Highly efficient polymer-based nanoreactors for selective oxidation of alcohols in water

In this study, we demonstrate the fabrication of thermo-responsive polymer-based TEMPO nanoreactors and their application in the catalytic selective oxidation of alcohols as a highly efficient and recoverable catalyst in aqueous media. First, a diblock amphiphilic copolymer NHS-P(MMA25-b-OEGMA75) consisting of poly(methyl methacrylate) (PMMA) and poly[oligo(ethylene glycol) methyl ether methacrylate] (POEGMA300) with a terminal N-hydroxysuccinimide (NHS) activated ester was synthesized utilizing reversible addition–fragmentation chain transfer polymerization (RAFT) techniques. Free radical 2,2,6,6,-tetramethyipiperidinooxy (TEMPO) was then introduced into the end of the copolymer based on activated ester functionalization to afford the temperature responsive polymer-supported catalyst TEMPO-P(MMA25-b-OEGMA75). Next, core-shell TEMPO nanoreactors were formed through self-assembly of the amphiphilic block polymers in deionized water. The morphology of the nanoreactors was well characterized by dynamic light scattering (DLS) and scanning electron microscopy (SEM). The nanoreactors were then successfully applied in the selective oxidative of alcohols in water. A variety of aldehydes and ketones were achieved in excellent yields and selectivities in high reaction rates with low catalyst loading. The high efficiency in catalysis of the nanoreactors may attributed to the ideal environment where enhancing the interactions between the catalyst and the alcohol substrate, mimicking the environment of enzymes. The thermo-responsive polymer-based nanoreactors could be conveniently recovered in the temperature above the LCST of the polymer after extraction of product from the reaction mixture. This strategy provides an effective and cleaner way for the selective oxidative of alcohols in organic synthesis and industrial application.