Aerobic Oxidation Of Alcohols Research Articles

Pd-Au nanoparticles supported reduced graphene oxide nanoplatelets toward aerobic selective oxidation of benzoyl alcohol

In this paper, mono-metallic catalysts, palladium (Pd) and gold (Au) and bi-metallic, Au-Pd supported on reduced graphene oxide (rGO) synthesized by Sol Immobilization technique. The as fabricated catalysts (Pd/rGO, Au/rGO and Au-Pd/rGO) have been tested by various techniques (Raman Spectroscopy, FE-SEM, XRD and TEM) to examine the structural, compositional and morphological characteristics. The performance of catalysts on the production of benzaldehyde via benzyl alcohol (BnOH) oxidation was investigated adopting H2O2 as an oxidizing agent. In general, Au-Pd/rGO catalyst presented a remarkable superiority over Au/rGO and Pd/rGO. The Au-Pd/rGO catalyst gave the best reaction conversion ratio of 24.3%, while its selectivity for benzaldehyde was 87.5% using 10 mg catalyst mass, reaction temperature 80 oC and 50% H2O2

Tetrabutyl Ammonium Salts of Keggin-Type Vanadium-Substituted Phosphomolybdates and Phosphotungstates for Selective Aerobic Catalytic Oxidation of Benzyl Alcohol

A series of tetrabutyl ammonium (TBA) salts of V-included Keggin-type polyoxoanions with W (TBA4PW11V1O40 and TBA5PW10V2O40) and Mo (TBA4PMo11V1O40 and TBA5PMo10V2O40) as addenda atoms were prepared using a hydrothermal method. These synthesized materials were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), UV-Vis diffuse reflectance (DRS UV-Vis), thermogravimetric analysis (TGA), CHN elemental analysis (EA), inductively coupled plasma spectrometry (ICP-MS), and N2 physisorption techniques to assess their physicochemical/textural properties and correlate them with their catalytic performances. According to FT-IR and DRS UV-Vis, (PVXW(Mo)12−XO40)(3+X)− anions are the main species present in the TBA salts. Additionally, CHN-EA and ICP-MS revealed that the desired stoichiometry was obtained. Their catalytic activities in the liquid-phase aerobic oxidation of benzyl alcohol to benzaldehyde were studied at 5 bar of O2 at 170 °C. Independently of the addenda atom nature, the catalytic activity increased with the number of V in the Keggin anion structure. For both series of catalysts, TBA salts of polyoxometalates with the highest V-substitution degree (TBA5PMo10V2O40 and TBA5PW10V2O40) showed higher activity. The maximum benzyl alcohol conversions obtained were 93% and 97% using (TBA)5PMo10V2O40 and (TBA)5PW10V2O40 as catalysts, respectively. In all the cases, the selectivity toward benzaldehyde was higher than 99%.

Polyimide-supported Cu/2,2,6,6-tetramethyl-1-piperidine-N-oxyl catalytic systems: Aromatic donor-acceptor interaction-directed cooperative catalysis

Non-covalent immobilization of multifunctional catalysts onto polymer supports is a promising technique to build highly efficient heterogeneous cooperative catalysts. Here, we present a strategy to build polyimide-supported Cu/2,2,6,6-tetramethyl-1-piperidine-N-oxyl (TEMPO) catalytic systems based on hydrophobic interactions and aromatic donor-acceptor interactions. Pyrene-containing catalytic species and naphthalene diimide (NDI)-based polyimides were chosen for the preparation of nanoparticle catalysts using the nanoprecipitation technique. The cooperative behaviors of catalytic components were evaluated by the catalytic activities of aerobic oxidation of benzyl alcohol (BnOH) in water. We studied the influence of effective constituent ratio of polymers, chain length of monomer, and the incorporation of a second monomer on catalytic activities. The aggregate structures were investigated by X-ray powder diffraction (XRD) patterns and small angle X-ray scattering (SAXS), and speculated to be random distributions of aromatic stacking clusters within nanoparticle catalysts. This strategy will find applications in the construction of other multifunctional heterogeneous catalysts.

Crystalline porous ionic salts assembled from polyoxometalates and cationic capsule for the selective photocatalytic aerobic oxidation of aromatic alcohols to aldehydes

Crystalline porous ionic salts (CPISs) represent a new type of porous materials constructed by electrostatic interaction, however, synthesis of CPISs bearing pre-designed functionality while exhibiting permanent porosity is still challenging. Herein we report the facile synthesis of a series of CPISs 1-3 built from photocatalytic-active polyoxometalate (POM) clusters and cationic Zr-based capsules, which showed open porous frameworks with BET surface area up to 33 m2/g and high activity and selectivity for photo-driven aerobic oxidation of alcohols to aldehydes. Compared with the pristine POM cluster {W10}, 1 can promote the reaction in much higher efficiency due to the concerted catalysis of preinstalled {W10} and Zr-based capsule together with open channels. This work highlights the advantage of CPISs as porous heterogeneous catalysts in organic transformation, and may shed light on the rational design of more delicate CPISs-derived functional materials.

Comparison of the Two Carbon Allotropes as Solid Support: Catalytic Efficiency of the Supported Metalloporphyrins for the Aerobic Oxidation of Alcohols

AbstractIn the present research, a new method for the aerobic oxidation of aromatic and cyclic aliphatic alcohols to the corresponding aldehydes or ketone was developed in the presence of two supported metalloporphyrins. The prepared heterogenized catalysts were fully characterized by transmission electron microscopy (TEM), scanning electron microscope (SEM), thermogravimetric analysis (TGA), atomic absorption spectroscopy (AAS), Fourier Transform Infrared (FT‐IR) and Ultra Violet‐Visible (UV‐Vis) spectroscopy. The role of structural and textural properties of carbon‐based materials as solid support on the catalytic efficiency of the supported catalysts was compared with each other and the results shows higher efficiency of the supported Fe‐porphyrin on multi‐walled carbon nanotube [Fe(THPP)Cl/MWCNT] compared to the anchored Fe‐porphyrin on the graphene oxide [Fe(THPP)Cl/GO]. The study on the aerobic oxidation of alcohols in the presence of the supported Fe‐porphyrins proved that the addition of isobutyraldehyde as reducing agent in several portions during the catalytic reaction significantly increased the product yields. The separation and recovery of the nanocatalyst was simple, effective and economical in this green oxidation method and the supported catalyst can reuse at least eight times without significant loss of activity.

(Catecholate)Cu I 2 -Displayed Porous Organic Polymers as Efficient Heterogeneous Catalysts for the Mild and Selective Aerobic Oxidation of Alcohols

(Catecholate)Cu ^I ₂ -Displayed Porous Organic Polymers as Efficient Heterogeneous Catalysts for the Mild and Selective Aerobic Oxidation of Alcohols

Highly Efficient One‐pot Aerobic Synthesis of α‐Aminophosphonate from Alcohols: Dual Catalytic Effect of Tetrabutylammonium Tribromide (TBATB)

AbstractIn this work, a simple, metal‐free, and homogeneous two steps one‐pot method for the synthesis of α‐aminophosphonate in the presence of tetrabutylammonium tribromide (TBATB) from alcohol was reported. Interestingly TBATB showed catalytic effect for both photo tuanable aerobic oxidation of alcohol (including electron rich and poor) and α‐aminophosphonate synthesis from in situ prepared aldehyde. Also, more interestingly efficiency of the synthesis is higher for starting from alcohols than aldehyde. The optimized condition including: solvent, catalyst amounts, photo and thermal factors was considered. Various derivatives of benzyl alcohol and aniline participated well in this reaction and produced the corresponding α‐aminophosphonates efficiently.

From Deep Eutectic Solvents to Nitrogen‐rich Ordered Mesoporous Carbons: A Powerful Host for the Immobilization of Palladium Nanoparticles in the Aerobic Oxidation of Alcohols

AbstractThe preparation of a nitrogen‐rich ordered mesoporous carbon (DNOMC) with three‐dimensional cubic structure was established via carbonization of a green, inexpensive and safe deep eutectic solvent consisting of choline chloride salt and D‐glucose in the presence of KIT‐6 template for the first time. The materials were characterized by TEM, N2 adsorption–desorption analysis, XPS, TGA, CHN, and FT‐IR. The DNOMC was shown to be a powerful support for the immobilization of palladium nanoparticles. The Pd@DNOMC catalyst exhibited high activity in the selective aerobic oxidation of various activated and non‐activated primary and secondary benzylic as well as linear and cyclic aliphatic alcohols to the corresponding carboxylic acids and ketones in pure water under molecular oxygen. The catalyst system could successfully be reused at least ten times without any significant decrease in either activity or selectivity. It is worth noting that, the hot filtration strongly showed that the catalyst works in a boomerang‐type catalyst pathway.

Solvent-free aerobic selective oxidation of benzyl alcohol over La-Co bimetallic catalyst: A kinetic study

It is desirable but challenging to explore non-noble metal based catalyst for the solvent-free aerobic oxidation of benzyl alcohol to benzaldehyde. LayCo1Ox was prepared through a co-precipitation method, which exhibited excellent catalytic performance for titled reaction with a yield of 73.1% and selectivity of 99.6%. Introduction of La in the Co3O4 can modify the electronic property of Co, improving the surface Co3+ content and enhancing the activity. The synergistic effects of La and Co in the bimetallic catalysts are kinetically discussed. In addition, the kinetic and experimental studies revealed that the generated water favors the selectivity but suppresses the activity for the titled reaction. It is found that good activity and excellent selectivity for the (heterocyclic)aromatic alcohols aerobic selective oxidation over the bimetallic catalyst were obtained.

Cobalt-doped g-C3N4/MOF heterojunction composite with tunable band structures for photocatalysis aerobic oxidation of benzyl alcohol

Due to decrease environmental pollution and energy crisis, it is necessary to find an excellent solution to utilize visible light with photocatalyst technology. Therefore, it can be argued that the use of photocatalysts as well as clean and natural solar energy can be considered as an efficient and promising solution. Constructing heterostructure photocatalysts with metal-organic frameworks (MOFs), and graphitic carbon nitride (g-C3N4-Co) is a powerful viewpoint to obtain high performance in visible-light photocatalysis. In this work, we prepared a heterostructure photocatalyst using Zn-based MOF and cobalt-doped graphitic carbon nitride (g-C3N4-Co) termed TMU-22/g-C3N4-Co. Characterization of TMU-22/g-C3N4-Co composite was performed by PXRD, FT-IR, TGA, SEM, EDS, UV-vis DRS, and BET. This composite showed a high performance in aerobic oxidation of benzyl alcohol to benzaldehyde under visible-light irradiation in mild conditions (at atmospheric pressure and room temperature) which comes from the cooperative performance of g-C3N4-Co and TMU-22(Zn) components. Additionally, studies performed using radical scavengers indicated that electrons and holes serve as the main reactive species. The superior photocatalytic activity of the composite is attributed to the enhanced separation of the photogenerated electron-hole pairs, as well as increased visible-light absorption.

Water tolerant base free Copper (I) catalyst for the selective aerobic oxidation of primary alcohols

We report here a base free copper(I) catalyst for the selective aerobic oxidation of primary alcohols to their corresponding aldehydes and various diols to their corresponding lactones or lactols. In the presence of the in situ generated Cu(I)-catalyst with 2,2′-dipyridylamine (dpa) as a ligand and 2,2,6,6-tetramethylpiperdine-N-oxyl (TEMPO) as a persistent radical, the oxidation reaction proceeds under true aerobic conditions, at ambient temperature, utilizing air as the oxidant and without added base. High catalytic activity without over oxidation was achieved for numerous primary alcohols (aliphatic, allylic, benzylic and diols) with different substitution patterns. The catalyst's stability is unique among reported Cu(I)-catalysts. It is not moisture or air sensitive, and is capable of e.g. oxidizing aliphatic and benzyl alcohols in a water/acetonitrile solution in moderate or in quantitative yield (> 99%) in 3 h.

Improved visible-light activities of ultrathin CoPc/g-C3N4 heterojunctions by N-doped graphene modulation for selective benzyl alcohol oxidation

The interface modulation is the key factor affecting the photoactivity of metal phthalocyanine (MPc)/g-C3N4 heterojunctions for aerobic selective alcohol oxidation. Here, we have successfully fabricated the N-doped graphene-modulated CoPc/g-C3N4 nanosheets (CoPc/NG/CN) heterojunctions. Optimal CoPc/NG/CN photocatalyst demonstrates approximately fourfold photoactivity improvement for benzyl alcohol oxidation with ∼99% selectivity toward benzyl aldehyde and of approximately ninefold 2,4-dichlorophenol degradation rate compared with bare CN, using O2 as oxidant. By means of steady-state surface photovoltage responses in N2 atmosphere, time-resolved photoluminescence spectra, single-wavelength photocurrent action spectra, and electrochemical O2 reduction measurements, it is confirmed that the exceptional photoactivities of resulting CoPc/NG/CN heterojunction are attributed to the facilitated interfacial charge transfer between CoPc and CN by the modulation of NG with favorable electron-induced capacity. In addition, more enriched hydroxyl groups of NG by N doping could induce high dispersion of CoPc molecules via H-bonding effect, resulting in the increase of exposed number of CoPc as visible-light absorption units and single Co2+ sites as catalytic centers for O2 activation so as to further benefit the photocatalytic oxidation processes. This work provides a feasible interfacial modulation strategy to fabricate efficient supported MPc-based heterojunction photocatalyst nanomaterials.

Facile fabrication of size-controlled Pd nanoclusters supported on Al2O3 as excellent catalyst for solvent-free aerobic oxidation of benzyl alcohol

Selective oxidation of benzyl alcohol (BzOH) to benzaldehyde is one of the most important organic transformations. It is vital to explore a stable, economic and highly efficient catalyst. Here, Pd/R-Al2O3 (R = Al(NO3)3/urea molar ratio) was prepared by hydrothermal process followed by cation-assisted polyol method, and utilized for solvent-free aerobic oxidation of BzOH without any additives. Characterization results from TEM, NH3/CO2/O2-TPD and XPS showed that the size of Pd nanoclusters on Pd/R-Al2O3 was controlled by base number on R-Al2O3, and the order of oxygen mobility was Pd/1:6-Al2O3 > Pd/1:7-Al2O3 > Pd/1:8-Al2O3 > Pd/1:9-Al2O3. In the BzOH oxidation, R-Al2O3 as a basic additive could improve the benzaldehyde selectivity, and all surface atoms of Pd nanoclusters displayed the same catalytic activity. Excellent oxygen mobility indicated a high catalytic performance since it accelerated oxygen transfer from gaseous molecular oxygen to the surface of Pd nanoclusters to rapidly regenerate active Pd0 species. Among Pd/R-Al2O3 catalysts, Pd/1:6-Al2O3 exhibited a turnover frequency of 70381 h−1 due to the smallest Pd size and the best oxygen mobility, and good stability after five recycles owing to the strong interaction between Pd0 species and R-Al2O3. Therefore, Pd/R-Al2O3 may be great potential as a promising candidate for numerous catalytic reactions.

Pickering Interfacial Catalysis for Aerobic Alcohol Oxidation in Oil Foams.

Oil foams stabilized by surface-active catalytic particles bearing fluorinated chains and Pd nanoparticles allowed fast and efficient aerobic oxidation of a variety of aromatic and aliphatic alcohols compared to bulk catalytic systems at ambient O2 pressure. High foam stability was achieved at low particle concentration (<1 wt %) provided that the contact angle locates in the range 41°-73°. The catalytic performance was strongly affected by the foaming properties, with 7-10 times activity increase in pure O2 compared to nonfoam systems. Intermediate foam stability was required to achieve good catalytic activity, combining large interfacial area and high gas exchange rate. Particles were conveniently recycled with high foamability and catalytic efficiency maintained for at least seven consecutive runs.

Atomically Defined Undercoordinated Copper Active Sites over Nitrogen-Doped Carbon for Aerobic Oxidation of Alcohols.

Selective aerobic oxidation of alcohols offers an attractive means to address challenges in the modern chemical industry, but the development of non-noble metal catalysts with superior efficacy for this reaction remains a grand challenge. Here, this study reports on such a catalyst based on atomically defined undercoordinated copper atoms over nitrogen-doped carbon support as an efficient, durable, and scalable heterogeneous catalyst for selective aerobic oxidation of alcohols. This catalyst exhibits extremely high intrinsic catalytic activity (TOF of 7692 h-1 ) in the oxidation of cinnamyl alcohol to afford cinnamaldehyde, along with exceptional recyclability (at least eight cycles), scalability, and broad substrate scope. DFT calculations suggest that the high activity derives from the low oxidation state and the unique coordination environment of the copper sites in the catalyst. These findings pave the way for the design of highly active and stable single atom catalysts to potentially address challenges in synthetic chemistry.

Bio-inspired lanthanum-ortho-quinone catalysis for aerobic alcohol oxidation: semi-quinone anionic radical as redox ligand

Oxidation reactions are fundamental transformations in organic synthesis and chemical industry. With oxygen or air as terminal oxidant, aerobic oxidation catalysis provides the most sustainable and economic oxidation processes. Most aerobic oxidation catalysis employs redox metal as its active center. While nature provides non-redox metal strategy as in pyrroloquinoline quinone (PQQ)-dependent methanol dehydrogenases (MDH), such an effective chemical version is unknown. Inspired by the recently discovered rare earth metal-dependent enzyme Ln-MDH, here we show that an open-shell semi-quinone anionic radical species in complexing with lanthanum could serve as a very efficient aerobic oxidation catalyst under ambient conditions. In this catalyst, the lanthanum(III) ion serves only as a Lewis acid promoter and the redox process occurs exclusively on the semiquinone ligand. The catalysis is initiated by 1e--reduction of lanthanum-activated ortho-quinone to a semiquinone-lanthanum complex La(SQ-.)2, which undergoes a coupled O-H/C-H (PCHT: proton coupled hydride transfer) dehydrogenation for aerobic oxidation of alcohols with up to 330 h−1 TOF.

Transition Metal‐Free Aerobic Oxidation of Aryl Secondary and Primary Alcohols to Carbonyl Compounds in Open Air

AbstractThe ketones and benzoic acids are very useful chemicals as the precursors and intermediates in both laboratory and synthetic industrial applications, which are usually obtained by selective catalytic oxidation of alcohols using a amount of certain expensive oxidants or metal catalysts. Here, an efficient and practical oxidation the aryl secondary and primary alcohols to corresponding carbonyl compounds using NaOtBu in open air at room temperature has been developed. And utilizing NaOtBu/air/ toluene, a series of ketones or benzoic acids were obtained from secondary and primary alcohols in high yields, respectively. More importantly, most of the substrates with electron‐withdrawing or electron‐donating groups could be converted to the corresponding products in high to excellent yields. Furthermore, the practicality of the reaction was demonstrated through 1.0 gram‐scale reaction with excellent yield.

A bagasse-supported magnetic manganese dioxide nanoparticle: applications in the selective aerobic oxidation of alcohols and one-pot tandem oxidative synthesis of quinazolinones

A bagasse-supported magnetic manganese dioxide nanoparticle: applications in the selective aerobic oxidation of alcohols and one-pot tandem oxidative synthesis of quinazolinones

MOF‐Stabilized Perfluorinated Palladium Cages Catalyze the Additive‐Free Aerobic Oxidation of Aliphatic Alcohols to Acids

AbstractExtremely high electrophilic metal complexes, composed by a metal cation and very electron poor σ‐donor ancillary ligands, are expected to be privileged catalysts for oxidation reactions in organic chemistry. However, their low lifetime prevents any use in catalysis. Here we show the synthesis of fluorinated pyridine‐Pd2+ coordinate cages within the channels of an anionic tridimensional metal‐organic framework (MOF), and their use as efficient metal catalysts for the aerobic oxidation of aliphatic alcohols to carboxylic acids without any additive. Mechanistic studies strongly support that the MOF‐stabilized coordination cage with perfluorinated ligands unleashes the full electrophilic potential of Pd2+ to dehydrogenate primary alcohols, without any base, and also to activate O2 for the radical oxidation to the aldehyde intermediate. This study opens the door to design catalytic perfluorinated complexes for challenging organic transformations, where an extremely high electrophilic metal site is required.

Fabrication of P-Doped Porous Carbon Catalysts, with Inherent N Functionality, from Waste Peanut Shells and Their Application in the Metal-Free Aerobic Oxidation of Alcohols

Based on low-cost, N-containing biomass waste peanut shells and phosphoric acid, the P element was successfully introduced into the carbon skeleton to obtain P-doped porous carbon materials, with inherent N functionality. In comparison to carbon catalysts functionalized with just N or P (NC-800 or PC), the as-prepared P-doped, N-containing porous carbon materials (NPC-T) possessed superior catalytic activity toward the aerobic oxidation of benzyl alcohol (BA). According to these findings, a synergistic effect of N and P species on the catalytic efficiency of carbon materials was observed. The amounts of graphitic N and C3PO species on the surface of NPC-T were shown to be correlated with catalytic activity. In the case of NPC-800, 100% conversion and 99.7% selectivity could be achieved along with a high TOF value (2.49 × 10–3 mol·g–1·h–1). Even when applied to various alcohols, the NPC-800 still showed good catalytic activity. Based upon the mechanistic investigations, both radical and nonradical reaction pathways occurred during the aerobic oxidation of BA over the NPC-800. Furthermore, to facilitate catalyst recycling, the granular P-doped, N-containing carbon (granular NPC-800) was generated, utilizing a kneading heat treatment and extrusion molding technique that did not require the addition of any extra adhesive. This work highlighted the potential high-value utilization of biomass waste in constructing P-doped, N-containing carbon materials and the application as metal-free catalysts in the aerobic selective oxidation reactions.