Efficient Catalyst For Aerobic Oxidation Research Articles

Catalytic activity of CuI/CuII cyanide based phenanthroline-bicarbonate system for enhancing aerobic oxidation of 2,6-di-tert-butylphenol

The metal organic framework {[Cu2(CN)3(phen)3]5H2O} MOF1- bicarbonate system was investigated as an efficient catalyst for aerobic oxidation of 2, 6-di-tert-butylphenol (2,6- DTBP). The catalytic system showed very efficient catalytic behavior for the oxidation of selective coupling of 2,6- DTBP to 3,3′,5,5′-tetra-tert-butyl-4,4′-diphenoquinone (DPQ) in excellent yield. The influence of reaction parameters on the selective oxidation of 2, 6-DTBP to DPQ had been investigated. Photoluminescence probing technology of Disodium salt of terephthalic acid as well as scavenging experiments revealed the creation of the hydroxyl radicals as the main active oxidation radicals produced by the MOF1/O2/basic bicarbonate system. The oxidation reaction mechanism was also discussed. The recycled catalytic system retained its activity for eight successive runs.

G-C3N4 modified Co3O4 as efficient catalysts for aerobic oxidation of benzyl alcohol

Graphitic carbon nitride (g-C3N4) modified Co3O4 was prepared by impregnation and pyrolysis. The obtained g-C3N4/Co3O4 was thoroughly characterized by XRD, SEM, TEM, FTIR, TG and N2 adsorption. Its catalytic performance was investigated in the aerobic oxidation of benzyl alcohol in liquid phase. High activity as well as excellent selectivity to benzaldehyde can be obtained at mild condition (at atmospheric pressure and temperature of 80 °C). H2-TPR and XPS results show that the excellent activity over modified Co3O4 comes from the cooperative action of g-C3N4 and Co3O4 components. g-C3N4/Co3O4 can also be used as an efficient catalyst for the aerobic oxidation of various aromatic alcohols. However, it is not active for the aerobic oxidation of aliphatic alcohols.

Magnetic nano-structured cobalt–cobalt oxide/nitrogen-doped carbon material as an efficient catalyst for aerobic oxidation of p-cresols

Efficient aerobic oxidation has been developed for the selective preparation of a sequence of valuable p-hydroxybenzaldehydes from corresponding p-cresols, using a new magnetically separable catalyst of nano-structured cobalt–cobalt oxide/nitrogen-doped carbon (CoOx@CN) material. CoOx@CN showed high activity for the 2-methoxy-4-cresol oxidation to vanillin, giving great yield (90%) and with good turnover number (210), as well as other p-cresols in good to great yields. The catalytic performance was investigated and related to the structural, chemical and magnetic properties which determined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FT-IR) and vibrating sample magnetometer (VSM). The effects of base to substrate molar ratio, catalyst concentration, temperature, and solvent on the conversion and selectivity patterns also have been studied. The investigation revealed that remarkable catalytic properties of CoOx@CN could be ascribed to the active species cobalt oxide, doped nitrogen and porous carbon with large surface area. The size of the catalyst is a key factor for catalyst performance. The ferromagnetic property of catalyst enables to recycle easily by an external magnetic field and reuse six successive times without significant activity loss.

Iron-based metalloporphyrins as efficient catalysts for aerobic oxidation of biomass derived furfural into maleic acid

A series of porphyrin type catalysts with the metal active sites of Fe were prepared and investigated in aerobic oxidation of biomass-based furfural to maleic acid (MAD) in aqueous phase. The catalytic performance of meso-tetrakis(4-bromophenyl)porphyrin iron (III) chloride (FeT(p-Br)PPCl) immobilized on different supports was evaluated. It was interesting to find that the catalytic activity varied with the supports and followed the trend: FeT(p-Br)PPCl/SBA–15 > FeT(p-Br)PPCl/meso-ZSM–5 > FeT(p-Br)PPCl/MCM-41. The effect of reaction conditions were discussed in detail over FeT(p-Br)PPCl/SBA-15 catalyst, and 56.1% yield and 73.8% selectivity of MAD were obtained from renewable furfural under the optimal conditions. Moreover, the FeT(p-Br)PPCl/SBA-15 catalyst could be reused five times without a significant decrease of activity in recycling examinations.

A Low-Cost and Easily Prepared Manganese Carbonate as an Efficient Catalyst for Aerobic Oxidation of 5-Hydroxymethylfurfural to 2,5-Diformylfuran

A low-cost and easily prepared manganese carbonate (MnCO3) has been synthesized for catalytic conversion of 5-hydroxymethylfurfural (5-HMF) to 2,5-diformylfuran (DFF). The properties and morphology of the manganese carbonate were measured by SEM, XRD, TGA, BET and XPS. In this method, no harsh reaction conditions were required, and it was a simple and green process for the oxidation of 5-HMF into DFF. To achieve an optimum DFF yield, different reaction conditions, including reaction temperature, reaction time, catalyst amount, and solvents were investigated. Results from the experiments indicated that the highest DFF yield of 86.9% was obtained at 120 °C under atmospheric oxygen pressure after 6 h. Finally, MnCO3 could be used at least five times with considerable stability.

Bio-gel template synthesis of CoFe2O4 nano-catalysts and application in aerobic oxidation of cyclohexane

Magnetic cobalt ferrite (CoFe2O4) particles were synthesized via a solvothermal pathway by using the gel of natural lotus roots as bio-gel template. Samples with porous structure and of large specific area (∼95.6 m2/g) were prepared, which were assembled by CoFe2O4 particles of uniform sizes (ca. 15.0 nm). The annealed CoFe2O4 nanoparticles were proven to be highly efficient catalysts for aerobic oxidation of cyclohexane. Factors such as oxygen pressure, temperature, reaction time and self-catalysis by adding cyclohexanone have been studied in view of improving the conversion of cyclohexane as well as the selectivity of KA oil (cyclohexanone and cyclohexanol). Optimum parameters were found at an initial O2 pressure of 1.6 MPa when the reaction was conducted for 6.0 h at the temperature of 150 °C. The maximum conversion of cyclohexane oxidation reaches 16.43%, and the selectivity 90.3% for KA oil was obtained. This research provides a facile way of developing green catalysts in the aerobic oxidation of cyclohexane.

Co–N–C supported on SiO2: a facile, efficient catalyst for aerobic oxidation of amines to imines

The aerobic oxidation of amines to imines was catalyzed by Co–C–N/SiO2 which was obtained by the pyrolysis of silicone gel containing metal ion and triethanolamine.

Large-scale synthesis of ultrathin tungsten oxide nanowire networks: an efficient catalyst for aerobic oxidation of toluene to benzaldehyde under visible light.

As a very important chemical raw material, the selective formation of benzaldehyde from toluene at preparative or industrial levels requires the use of highly corrosive chlorine and high reaction temperatures, which severely corrodes equipment, pollutes the environment, and consumes a lot of energy. Herein, we report a robust and highly active catalyst for the benzaldehyde evolution reaction that is constructed by the surfactant-free growth of oxygen vacancy-rich W18O49 ultrathin nanowire networks. Under atmospheric pressure and visible-light irradiation, the new catalyst can selectively (92% selectivity) catalyze the aerobic oxidation of toluene to benzaldehyde with yields of above 95%.

Carbon nanotube-supported Au-Pd alloy with cooperative effect of metal nanoparticles and organic ketone/quinone groups as a highly efficient catalyst for aerobic oxidation of amines.

Functionalised carbon nanotube (CNT)-supported Au-Pd alloy nanoparticles were highly efficient catalysts for the aerobic oxidation of amines. We achieved the highest turnover frequencies (>1000 h(-1)) for the oxidative homocoupling of benzylamine and the oxidative dehydrogenation of dibenzylamine. We discovered a cooperative effect between Au-Pd nanoparticles and ketone/quinone groups on CNTs.

ChemInform Abstract: Organic Inorganic Hybrid Cobalt Phthalocyanine/Polyaniline as Efficient Catalyst for Aerobic Oxidation of Alcohols in Liquid Phase.

AbstractThe heterogeneous title reaction exhibits superior activity compared to homogeneous cobalt phthalocyanine catalysts with added benefits of easy recovery and recycling.

Organic inorganic hybrid cobalt phthalocyanine/polyaniline as efficient catalyst for aerobic oxidation of alcohols in liquid phase

Organic inorganic hybrid catalyst synthesized by doping of cobalt phthalocyanine (CoPc) on polyaniline support (CoPc/PANI) exhibited higher activity for the oxidation of various alcohols to the corresponding carbonyl compounds in high to excellent yield using molecular oxygen as oxidant and isobutyraldehyde as a sacrificial agent. Notably, the synthesized catalyst was found to be truly heterogeneous in nature and could be easily recovered, recycled for several recycling runs without loss of catalytic activity.

Facile synthesis of highly active Co(II) and Fe(II) phthalocyanine catalysts for aerobic oxidation of phenolic compounds

In this work, 2,3-dichlorophenoxy substituted cobalt and iron phthalocyanines have been synthesized and used as efficient catalysts for aerobic oxidation of nitrophenols. Co(II) and Fe(II) phthalocyanines have been characterized by IR, 1H NMR, 13C NMR, UV–vis, and mass spectroscopies. tert-butyl hydroperoxide (TBHP), m-chloroperoxybenzoic acid, hydrogen peroxide, and air oxygen have been used as oxygen source. These catalysts offered the highest activity on 4-nitrophenol oxidation in 3 h. In order to achieve the best reaction conditions, oxidant ratio, temperature, and oxidant type have been investigated with different nitrophenols in 3 h.

ChemInform Abstract: Silica‐Supported 4‐OH‐TEMPO/NOx: A Novel and Efficient Catalyst for Aerobic Oxidation of Alcohols.

Abstract Silica-supported 4-OH-2,2,6,6-tetramethylpiperidyl-1-oxy/NOx (4-OH-TEMPO was immobilized on the surface of silica using the sol-gel method, and then it adsorbed NOx), as a heterogeneous catalyst, has exhibited good catalytic performance in alcohol oxidation. A broad range of alcohols were oxidized to their corresponding aldehydes or ketones with more than 99% selectivity and 99% conversion rate by such a catalyst system at room temperature in air. NOx not only acted as an electron bridge between O2 and 4-OH-TEMPO but also were conducive to the formation of the aldehydes as active component. A possible mechanism for oxidation of alcohols promoted by silica-supported 4-OH-TEMPO/NOx was supposed. [Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]

One-step synthesis of Pd nanoparticles functionalized crystalline nanoporous CeO2 and their application for solvent-free and aerobic oxidation of alcohols

Crystalline nanoporous CeO2 (CM-CeO2) has been successfully prepared through self assembly of poly 4-vinylpyridine (P4VP) template with Ce(NO3)3·6H2O precursor based on their strong acid–base interactions under high temperature (180°C) hydrothermal conditions. After calcination of the sample at 550°C in the air, crystalline nanoporous CeO2 with opened nanopores was obtained. Pd nanoparticles acted as active species could be easily introduced into the sample, which gives the sample of CM-CeO2-Pd-1.0 (where 1.0 stands for weight percentage of Pd). CM-CeO2-Pd-1.0 exhibits very good catalytic activity (Conv. 82.1%) and selectivity (97.6%) for aerobic oxidation of benzyl alcohol under solvent-free conditions. The enhanced catalytic performance of CM-CeO2-Pd-1.0 should be attributed to synergistic effects between abundant nanopores, unique oxygen storage and release properties of CM-CeO2 support. The preparation of CM-CeO2-Pd-1.0 may help develop cost-effective and efficient catalysts for aerobic oxidation of various alcohols into useful fine chemicals under mild conditions.

Metal-Free Allylic Oxidation with Molecular Oxygen Catalyzed by g-C3N4 and N-Hydroxyphthalimide

Polymeric graphitic carbon nitride (g-C3N4) is a layered graphite-like nitrogen-rich material, bearing the potential ability to reductively adsorb molecular oxygen for catalytic allylic oxidation. Furthermore, N-hydroxyphthalimide (NHPI) has been recognized as an efficient catalyst for aerobic oxidation of various organic compounds under mild conditions in the presence of various co-catalysts. We present here a promising strategy for employing such nitride-rich g-C3N4 combined with NHPI to form an all-organic metal-free composite and have examined its activity for allylic oxidation with molecular oxygen as the primary terminal oxidant. In the case of allylic oxidation α-isophorone catalyzed by g-C3N4/NHPI gave priority to its corresponding carbonyl compound and epoxide. The effects of various reaction conditions on the catalytic reaction were optimized, affording 74.8 % conversion with 44.4 % selectivity of ketoisophorone at 130 °C in 5 h. Repeated runs demonstrated that the catalyst was stable for at least three cycles without noticeable loss of its catalytic activity.

ChemInform Abstract: Cu‐NHC‐TEMPO Catalyzed Aerobic Oxidation of Primary Alcohols to Aldehydes.

Imidazolium salts bearing TEMPO groups react with commercially available copper powder affording Cu-NHC complexes. The in situ generated Cu-NHC-TEMPO complexes are quite efficient catalysts for aerobic oxidation of primary alcohols into aldehydes. The catalyst is easily available, and various primary alcohols were selectively converted to aldehydes in excellent yields.

Silica-Supported 4-OH-TEMPO/NOx: A Novel and Efficient Catalyst for Aerobic Oxidation of Alcohols

Silica-supported 4-OH-2,2,6,6-tetramethylpiperidyl-1-oxy/NOx (4-OH-TEMPO was immobilized on the surface of silica using the sol-gel method, and then it adsorbed NOx), as a heterogeneous catalyst, has exhibited good catalytic performance in alcohol oxidation. A broad range of alcohols were oxidized to their corresponding aldehydes or ketones with more than 99% selectivity and 99% conversion rate by such a catalyst system at room temperature in air. NOx not only acted as an electron bridge between O2 and 4-OH-TEMPO but also were conducive to the formation of the aldehydes as active component. A possible mechanism for oxidation of alcohols promoted by silica-supported 4-OH-TEMPO/NOx was supposed. [Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]

Magnetically recyclable core–shell Fe3O4@chitosan-Schiff base complexes as efficient catalysts for aerobic oxidation of cyclohexene under mild conditions

Five magnetic core–shell type Fe3O4@chitosan-Schiff base Co(II), Cu(II) and Mn(II) complexes were prepared in a simple way and well characterized by Fourier transform infrared spectrophotometry (FT-IR), X-ray photoelectron spectroscopy (XPS), X-ray diffractometry (XRD), transmission electron microscopy (TEM), dynamic light scattering (DLS) and thermogravimetry (TG). Their abilities to catalyze oxidation of cyclohexene with molecular oxygen in the absence of any solvents or reducing agents were investigated. It has been revealed that the as-prepared samples have high catalytic activities for heterogeneously aerobic oxidation of cyclohexene and 2-cyclohexene-1-one is the main product in all cases. Especially, when the Schiff base Co(II) complex derived from 5-nitrosalicyaldehyde was employed as catalyst, 46.8% of cyclohexene conversion, 77.2% of selectivity for 2-cyclohexene-1-one and as high as 4.7×103 of turnover number were obtained under ambient pressure at 70°C for 12h of reaction. The catalyst can be magnetically separated easily for reuse and no obvious loss of activity was observed when reused in five consecutive runs.

Cu-NHC-TEMPO Catalyzed Aerobic Oxidation of Primary Alcohols to Aldehydes

Imidazolium salts bearing TEMPO groups react with commercially available copper powder affording Cu-NHC complexes. The in situ generated Cu-NHC-TEMPO complexes are quite efficient catalysts for aerobic oxidation of primary alcohols into aldehydes. The catalyst is easily available, and various primary alcohols were selectively converted to aldehydes in excellent yields.

Reduced graphene oxide supported Au nanoparticles as an efficient catalyst for aerobic oxidation of benzyl alcohol

Various Au/C catalysts were prepared by Au nanoparticels supported on different carbonaceous supports including reduced graphene oxide (RGO), activated carbon (AC) and graphite (GC) using sol-immobilization method. Au/RGO shows a much higher activity than Au/AC and Au/GC in the liquid phase aerobic oxidation of benzyl alcohol. The superior catalytic performance of Au/RGO may be related to the presence of surface O-containing functional groups and moderate graphite character of RGO supports.