Efficient Catalytic Oxidation Research Articles

Efficient catalytic aerobic oxidation of chlorinated phenols with mixed-valent manganese oxide nanoparticles

BACKGROUNDMixed-valence manganese oxide nanoparticles (nano-MnOx) were prepared by the oxidation of Mn (II) with Mn-oxdizing bacteria Pseudomonas sp. G7. The chlorophenols transformation process was studied in detail. RESULTSThe materials were characterized by XRD, TEM-EDX, and XPS measurements. The characterization showed that mixed valence of Mn (II), Mn (III), and Mn (IV) existed in nano-MnOx-1 with the initial Mn (II) dosage of 0.4 mmol L-1. The catalyst was found to be highly effective, stable for catalytic aerobic oxidation of chlorophenols without any Mn (II) release from the catalyst throughout the reaction. Moreover, chlorinated phenols including 2-chlorophenol, 2, 4-dichlorophenol and 2, 4, 6-trichlorophenol, were partly converted into small organic acids. The formation of superoxide radicals (O-2(center dot-)) predominantly came from the interaction of oxygen in air with the reduced manganese in nano-MnOx on the basis of the studies of electron spin resonance and all other information. CONCLUSIONThe mixed valence in nano-MnOx-1 enhanced the formation of O-2(center dot-), resulting in the inhibition of Mn (II) release, maintaining the catalyst stable. Degradation of the tested chlorinated phenols was ascribed to the oxidation of Mn (III/IV) and O-2(center dot-) in nano-MnOx-1 suspension. This finding indicates the potential of nano-MnOx for the elimination of unbiodegradable chemicals in water. (c) 2013 Society of Chemical Industry

Facile fabrication of magnetically recyclable metal-organic framework nanocomposites for highly efficient and selective catalytic oxidation of benzylic C-H bonds.

HKUST-1@Fe3O4 chemically bonded core-shell nanoparticles have been prepared by growing HKUST-1 thin layers joined by carboxyl groups onto Fe3O4 nanospheres. These magnetic core-shell MOF nanostructures show exceptional catalytic activity for the oxidation of benzylic C-H bonds and they can be recovered by magnetic separation and reused without losing any activity.

Waste Not, Want Not: Mild and Selective Catalytic Oxidation of Uronic Acids

And isn't it uronic: A mild, highly efficient and selective catalytic oxidation of pectin-derived uronic acids to the corresponding aldaric acids is reported. Fast, quantitative conversions (>99%) of the starting materials are achieved with high selectivity (>97%) at room temperature, using supported gold catalysts and air as oxidizing agent.

SnO2 Nanoparticles: Preparation and Evaluation of their Catalytic Activity in the Oxidation of Aldehyde Derivatives to their Carboxylic Acid and Sulfides to Sulfoxide Analogs

A variety of aromatic and aliphatic aldehydes were converted to the corresponding carboxylic acid derivatives with 30% H2O2 and tert-butyl hydroperoxide as the oxidant in the presence of a catalytic amount of SnO2 nanoparticles as a precursor. These nanoparticles were also used for the efficient catalytic oxidation of sulfides to sulfoxides using 30% H2O2. The present methodology offers several advantages such as applicability to a wide range of aldehydes/ sulfides, convenient work-up, mild reaction conditions as well as good yields and reasonable time of the reactions. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.

An Efficient Oxidation of Benzoins to Benzils by Manganese(II) Schiff Base Complexes Using Green Oxidant

A simple, highly efficient and mild catalytic oxidation of benzoins to the corresponding benzils was developed using manganese(II) Schiff base complexes as novel and reusable catalyst in the presence of acetonitrile as solvent and H2O2 as green oxidant. This simple method affords benzil derivatives at room temperature in short reaction times with high yield and purity. This convenient procedure will allow a further increase of the diversity within the benzil family.

Efficient catalytic oxidation of hydrocarbons mediated by tricopper clusters under mild conditions

Two tricopper complexes are developed for efficient oxidation of hydrocarbons. These catalysts are based on the tricopper cluster that has been shown to be capable of mediating facile O-atom transfer to a number of organic substrates upon activation by dioxygen. It is demonstrated that the two tricopper complexes [CuICuICuI(L)]+, with L=3,3′-(1,4-diazepane-1,4-diyl)bis(1-(bis(pyridin-2-yl)methyl)amino)propan-2-ol (7-Dipy) and 3,3′-(1,4-diazepane-1,4-diyl)bis(1-thiomorpholinopropan-2-ol) (7-Thio), can sustain catalytic oxidation of cyclohexane to cyclohexanol and cyclohexanone with high turnover frequencies in the presence of H2O2 in acetonitrile under ambient conditions. These catalysts appear to be extremely robust, with turnover limited by the H2O2 available to drive the process. The turnover frequencies of the catalysts are found to depend linearly on the H2O2 concentration with a second-order rate constant of ∼1×10−2mol−1s−1.

Co3O4 nanocrystals on single-walled carbon nanotubes as a highly efficient oxygen-evolving catalyst

The efficient catalytic oxidation of water to dioxygen is envisioned to play an important role in solar fuel production and artificial photosynthetic systems. Despite tremendous efforts, the development of oxygen evolution reaction (OER) catalysts with high activity and low cost under mild conditions remains a great challenge. In this work, we develop a hybrid consisting of Co3O4 nanocrystals supported on single-walled carbon nanotubes (SWNTs) via a simple self-assembly approach. A Co3O4/SWNTs hybrid electrode for the OER exhibits much enhanced catalytic activity as well as superior stability under neutral and alkaline conditions compared with bare Co3O4, which only performs well in alkaline solution. Moreover, the turnover frequency for the OER exhibited by Co3O4/SWNTs in neutral water is higher than for bare Co3O4 catalysts. Synergetic chemical coupling effects between Co3O4 nanocrystals and SWNTs, revealed by the synchrotron X-ray absorption near edge structure (XANES) technique, can be regarded as contributing to the activity, cycling stability and stable operation under neutral conditions. Use of the SWNTs as an immobilization matrix substantially increases the active electrode surface area, enhances the durability of catalysts under neutral conditions and improves the electronic coupling between Co redox-active sites of Co3O4 and the electrode surface. Open image in new window

Retracted: A new nano bismuth(III) salophen catalyst for green and efficient catalytic oxidation of sulfides into the corresponding sulfoxides

Bismuth(III) salophen as a new catalyst has been synthesized. Structural properties of this complex have been studied by Fourier transform infrared spectroscopy, X-ray diffraction, differential scanning calorimetry, and thermal gravimetric analyses. The average crystalline size of Bi-salophen particles was 86 nm. Thermal analyses show that the complex is stable over 300°C. Catalytic activity of this catalyst has been investigated in oxidation of sulfides. Different kinds of sulfides have been oxidized to the corresponding sulfoxides efficiently in the presence of sodium periodate as oxidant in glacial acetic acid as solvent at room temperature. These sulfides were selectively and completely converted into their corresponding sulfoxides in very short reaction times. Selectivity of this method was excellent, which is another advantage of this method.

Efficient catalytic wet peroxide oxidation of phenol at moderate temperature using a high-load supported copper catalyst

The use of hydrogen peroxide as the oxidizing agent in the presence of a catalyst (Catalytic Wet Peroxide Oxidation, CWPO) has emerged as a clean and effective alternative among other catalytic oxidation processes. The objective of this study is to evaluate the CWPO of phenol solutions using a high-load CuO/Al2O3 catalyst, which allows maintaining a high activity and efficiency compared to homogeneous copper, also overcoming secondary effluent contamination.The catalytic oxidation of aqueous phenol solutions using H2O2 as oxidizing agent and a home-made CuO/Al2O3 catalyst was studied in a batchwise slurry reactor. The applied H2O2:phenol molar ratio was only nearly 30% higher than the stoichiometric ratio. Experiments were performed at temperatures between 303 and 343K using different catalyst loads. Phenol disappearance and TOC reduction were monitored throughout the reaction time.Both phenol and TOC conversions were larger as temperature and catalyst load increased, following the higher hydrogen peroxide decomposition rates achieved. At the highest catalyst load and temperature, complete phenol conversion and ca. 80% TOC removal was achieved. Catalyst performance in terms of phenol and TOC disappearance was maintained after 12h of usage. Although there is evidence of some copper leaching from the catalyst, the homogeneous contribution to the overall activity is marginal.

Efficient catalytic oxidation of internal alkenes, aromatic hydrocarbons and alcohols by using orthometallated and non-orthometallated PdII complexes

Efficient catalytic oxidation of internal alkenes, aromatic hydrocarbons and alcohols by using orthometallated and non-orthometallated PdII complexes

Shape-controlled fabrication of the porous Co3O4 nanoflower clusters for efficient catalytic oxidation of gaseous toluene

Co3O4 nanoflower clusters were fabricated by a simple low-temperature hydrothermal method. The properties of Co3O4 nanomaterials were comprehensively determined by combining different analytical techniques. The self-assembled Co3O4 nanoflower clusters had good crystallinity and porous structure. They were utilized as the catalyst for the degradation of gaseous toluene. The experimental results showed that the catalytic activity of the as-prepared Co3O4 nanoflower clusters was much superior to the Co3O4 blocks under the same reaction conditions.

Synthesis, characterization, DFT studies and catalytic activities of manganese(ii) complex with 1,4-bis(2,2′:6,2′′-terpyridin-4′-yl) benzene

A new di-manganese complex with "back-to-back" 1,4-bis(2,2':6,2''-terpyridin-4'-yl) benzene ligation has been synthesized and characterised by a variety of techniques. The back-to-back ligation presents a novel new mononuclear manganese catalytic centre that functions as a heterogeneous catalysis for the evolution of oxygen in the presence of an exogenous oxidant. We discuss the synthesis and spectroscopic characterizations of this complex and propose a mechanism for oxygen evolution activity of the compound in the presence of oxone. The di-manganese complex also shows efficient and selective catalytic oxidation of sulfides in the presence of H(2)O(2). Density functional theory calculations were used to assess the structural optimization of the complex and a proposed reaction pathway with oxone. The calculations show that middle benzene ring is distorted respect to both of metallic centers, and this in turn leads to negligible resonance of electrons between two sides of complex. The calculations also indicate the unpaired electron located on oxyl-ligand emphasizes the radical mechanism of water oxidation for the system.

The Chemoselective Reduction of Isoxazolineγ-Lactams Through Iminium Aza-Diels-Alder Reactions: A Short-Cut Synthesis of Aminols as Valuable Intermediates towards Nucleoside Derivatives

Isoxazoline γ-lactams are prepared starting from the regioisomeric cycloadducts of benzonitrile oxide to the N-alkyl 2-azanorbornenes taking advantage of the efficient catalytic oxidation by RuO4. The reduction of the amide groups is easily conducted in the presence of LiAlH4 under mild conditions, which allowed for the chemoselective reduction of the amide moiety followed by ring opening to afford the desired conformationally locked isoxazoline-carbocyclic aminols, as valuable intermediates for nucleoside synthesis.

Design and high efficient photoelectric-synergistic catalytic oxidation activity of 2D macroporous SNO2/1D TiO2 nanotubes

A novel catalyst was constructed by assembling 1D TiO2 nanotubes (TiO2 NTs) photocatalyst and 2D macroporous SnO2 electrocatalyst, which presents simultaneously the outstanding photocatalytic and electrocatalytic properties, and was applied to the photoelectric synergistic catalytic oxidation of biorefractory pollutants. Liquid crystal soft template was prepared by block copolymer self-assembly, and the macroporous SnO2 membrane grew orderly on the TiO2 NTs using the soft template by one-step assembly. The macroporous SnO2 has the pore size distribution between 150 and 400nm, small particle size (14.2nm), and high loading amount (27.3gm−2). The band gap of the 2D macroporous SnO2/TiO2 NTs is 2.93eV. Compared with the general TiO2 NTs and the SnO2/TiO2NTs, the 2D macroporous SnO2/TiO2 NTs possess better optical absorption and photocatalytic properties, with a photoelectric conversion efficiency of 35.2% at 365nm. Moreover, the hybrid anode presents smaller surface impedance and solution interface impedance, larger electrochemical surface absorption volume and lower electrochemical reaction activation energy. In the photoelectrocatalytic process, the 2D macroporous SnO2/TiO2 NTs exhibited higher removal rate for 2,4-dichlorophenoxyacetic acid, the initial instantaneous current efficiency was 100%, and COD removal rate reached 90.1% within 3h. The study showed that the intermediates was generated faster and removed quickly on the prepared catalyst.

Catalytic Modulation on the Regioselectivity of the Photosensitized Oxidation of α-Pinene with Molecular Oxygen under Sodium Lamp Irradiation

A simple and efficient photosensitized catalytic oxidation approach for α-pinene with molecular oxygen in a temperature-controlled reactor with sparged dioxygen as oxidant and an immersed high-pressure sodium lamp as a green irradiation light source was developed. The effects of various catalysts and reaction parameters on reaction performance were studied. The results indicated that 98% conversion with 84% total selectivity for verbenone and verbenol was obtained when N,N '-dimethylformamide (DMF) was used as a solvent. The product distributions were remarkably affected by the reaction media and DMF was found to especially modulate the regioselectivity of the products. Moreover, a possible photosensitized catalytic oxidation reaction mechanism in DMF is proposed and a clear acid-base synergetic catalysis effect was evident. The relationship between chemical reactivity and selectivity was modeled using density functional theory at the B3LYP/6-311+G(d) level from optimized molecular configurations. 发展了一种简单有效的 α-蒎烯光敏催化氧化方法, 该方法以高压钠灯为绿色光源, 内循环氧气作为氧化剂和搅拌气, 自制水浴式光化学反应器. 考察了催化剂种类和反应条件对 α-蒎烯转化率和产物选择性的影响. 结果表明, α-蒎烯可通过催化一步生成单萜醇、醛和酮, 且通过催化剂的酸碱协同作用可调节产物的区域选择性. 当以 N , N -二甲基甲酰胺为溶剂时, α-蒎烯的转化率可达 98%, 主产物马鞭草烯酮和马鞭草烯醇的总选择性达到了 84%. 此外, 还探讨了 N , N -二甲基甲酰胺酸碱协同催化的作用机理, 并利用密度泛函计算结果对 α-蒎烯分子中化学反应活性和产物选择性之间的对应关系进行了合理的解释. An efficient catalytic modulation approach for the photosensitized oxidation of α-pinene with molecular oxygen was developed. A relationship between the chemical reactivity and selectivity was modeled using density functional theory.

ChemInform Abstract: Epoxidation of Alkenes and Oxidation of Alcohols with Hydrogen Peroxide Catalyzed by a Manganese(V) Nitrido Complex.

AbstractThe first examples of efficient catalytic oxidation of alkenes and alcohols using H2O2 as oxidant and a manganese (V) nitrido complex as catalyst are given.

Hydrogen bioelectrooxidation in ionic liquids: From cytochrome c 3 redox behavior to hydrogenase activity

Electrochemistry of polyheme bacterial cytochrome c 3 and catalytic oxidation of hydrogen by two different bacterial [NiFe] hydrogenases were investigated for the first time in pure room-temperature ionic liquids (RTILs) as electrolyte. Direct electrochemical response of Desulfovibrio vulgaris Hildenborough cytochrome c 3 (DvH cytc 3) adsorbed at a pyrolytic graphite (PG) electrode was observed in the RTILs used in this work: 1-butyl-3-methylimidazolium tetrafluoroborate (BmimBF4), 1-ethyl-3-methylimidazolium tetrafluoroborate (EmimBF4) and 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EmimNTf2). The electrochemical signal differed however from that obtained in aqueous buffer, and depended on the type of RTIL. UV–vis measurements as well as transfer experiments from aqueous buffer to RTILs or RTILs to aqueous buffer strongly suggested that the protein was not denatured in the presence of RTILs. EmimNTf2, as a hydrophobic non-water-miscible RTIL, was demonstrated to stabilize the native form of DvH cytc 3. Moreover it allowed an amount of electroactive DvH cytc 3 30-fold higher than observed in aqueous buffer. Catalytic oxidation of H 2 via Desulfovibrio fructosovorans [NiFe] hydrogenase (Df Hase) mediated by DvH cytc 3 failed however. Further investigation suggested that Df Hase could be inhibited in the presence of RTILs. Reasons for such an inhibition were explored, including the blocking up of the substrate channels. By using hyperthermophilic [NiFe] membrane-bound hydrogenase from Aquifex aeolicus (Aa Hase) an efficient direct catalytic oxidation process was obtained in mixed aqueous buffer/RTILs electrolytes, although direct H 2 oxidation was not observed in pure RTIL. Chronoamperometric experiments showed that Aa Hase could afford 80% RTILs in aqueous buffer, thus giving the opportunity of future electrolytes with uncommon and variable properties for biofuel cell design.

Efficient catalytic cycloalkane oxidation employing a “helmet” phthalocyaninato iron(iii) complex

We have examined the catalytic activity of an iron(III) complex bearing the 14,28-[1,3-diiminoisoindolinato]phthalocyaninato (diiPc) ligand in oxidation reactions with three substrates (cyclohexane, cyclooctane, and indan). This modified metallophthalocyaninato complex serves as an efficient and selective catalyst for the oxidation of cyclohexane and cyclooctane, and to a far lesser extent indan. In the oxidations of cyclohexane and cyclooctane, in which hydrogen peroxide is employed as the oxidant under inert atmosphere, we have observed turnover numbers of 100.9 and 122.2 for cyclohexanol and cyclooctanol, respectively. The catalyst shows strong selectivity for alcohol (vs. ketone) formation, with alcohol to ketone (A/K) ratios of 6.7 and 21.0 for the cyclohexane and cyclooctane oxidations, respectively. Overall yields (alcohol + ketone) were 73% for cyclohexane and 92% for cyclooctane, based upon the total hydrogen peroxide added. In the catalytic oxidation of indan under similar conditions, the TON for 1-indanol was 10.1, with a yield of 12% based upon hydrogen peroxide. No 1-indanone was observed in the product mixture.

Rugged water-oxidation anodes

The efficient catalytic oxidation of water to dioxygen in the solid state is one of the challenges to be overcome to build sun-driven and/or electrocatalytic water-splitting devices. Now, an effective water-oxidation hybrid catalyst system has been made by attaching a ruthenium-polyoxometallate complex to a carbon nanotube.

Efficient catalytic oxidation of tetraethylated rhodamine over ordered mesoporous manganese oxide

Ordered mesoporous manganese oxide (m-MnO x ) which consists of catalytic active MnO 2 and Mn 2O 3 phases has been successfully synthesized by a simple template casting method. The as-prepared m-MnO x sample exhibited excellent catalytic activity on the degradation of tetraethylated rhodamine (RhB) dye. The degradation efficiency was found greatly influenced by the catalyst concentration, the reaction temperature and the pH value of the reaction system. The decrease of chemical oxygen demand (COD) value was also observed along with the decolorization indicating the mineralization of the dye.