Catalytic Oxidation Of Olefins Research Articles

Mechanistic studies on catalytic alkane oxidation by Murahashi’s O2/copper(II)/aldehyde system

Mechanistic studies on catalytic alkane hydroxylation by the Murahashi’s O2/copper(II)/aldehyde system have been conducted to show that the autoxidation of aldehyde (RCHO) by O2 generating acyl radical intermediate (RC(O)•) is...

Tetranuclear Copper(II) Complexes Derived from 5-Bromo-2-((2-(2-hydroxyethylamino)ethylimino)methyl)phenol: Synthesis, Characterization, Crystal Structures and Catalytic Oxidation of Olefins.

An acetate bridged tetranuclear copper(II) complex, [Cu4L2(μ2-η1:η1-CH3COO)6(CH3OH)2] (1), and a chloride, phenolate and azide co-bridged tetranuclear copper(II) complex, [Cu4L2Cl2(μ-Cl)2(μ1,1-N3)2]2CH3OH (2), where L is the deprotonated form of the Schiff base 5-bromo-2-((2-(2-hydroxyethylamino)ethylimino)methyl)phenol (HL), have been synthesized and characterized by elemental analysis, IR and UV spectra, and single crystal X-ray diffraction. Single crystalX-ray analysis revealed that the Cu atoms in both complexes are in square pyramidal geometry. In complex 1, two [CuL] units and [Cu2(μ2-η1:η1-CH3COO)4] core are linked through two acetate ligands. In complex 2, [Cu2LCl(μ-Cl)] units are linked together by two end-on azido ligands. The Schiff base ligand coordinates to the Cu atoms through four N and O donor atoms. The molecules of both complexes are linked through hydrogen bonds to generate three dimensional networks. The catalytic property of the complexes for epoxidation reactions of some alkenes was studied using tert-butylhydroperoxide as the terminal oxidant under mild conditions in acetonitrile.

Highly Efficient Oxidation of Propane at Low Temperature over a Pt-Based Catalyst by Optimization Support.

Pt-based catalysts have attracted widespread attention in environmental protection applications, especially in the catalytic destruction of light alkane pollutants. However, developing a satisfying platinum catalyst with high activity, excellent water-resistance, and practical suitability for hydrocarbon combustion at low temperature is challenging. In this study, the Pt catalyst supported on the selected Nb2O5 oxide exhibited an efficient catalytic activity in propane oxidation and exceeded that of most catalysts reported in the literature. More importantly, the Pt/Nb2O5 catalyst maintained excellent activity and durability even after high-temperature aging at 700 °C and under harsh working conditions, such as a certain degree of moisture, high space velocity, and composite pollutants. The excellent performance of the Pt/Nb2O5 catalyst was attributed to the abundant metallic Pt species stabilized on the surface of Nb2O5, which prompted the C-H bond dissociation ability as the rate-determining step. Furthermore, propane was initially activated via oxidehydrogenation and followed the acrylate species path as a more efficient propane oxidation path on the Pt/Nb2O5 surface. Overall, Pt/Nb2O5 can be considered a promising catalyst for the catalytic oxidation of alkanes from industrial sources and could provide inspiration for designing superb catalysts for the oxidation of light alkanes.

Catalytic Oxidation of Alkanes by Organometallics in an In Situ Combustion Process

Catalytic Oxidation of Alkanes by Organometallics in an In Situ Combustion Process

High ratio of Ce3+/(Ce3++Ce4+) enhanced the plasma catalytic degradation of n-undecane on CeO2/γ-Al2O3

n-Undecane (C11) is the main component of volatile organic compounds (VOCs) emitted from the printing industry, and its emission to the atmosphere should be controlled. In this study, a dielectric barrier discharge reactor coupled with CeO2/γ-Al2O3 catalysts was used to degrade C11. The effect of the chemical state of CeO2 on C11 degradation was evaluated by varying the CeO2 loading on γ-Al2O3. The C11 conversion and COx selectivity were as high as 92% and 80%, respectively, under mild reaction conditions of energy density 34 J/L and 423 K to degrade 134 mg/m3 C11 in a simulated air using 10 wt%CeO2 impregnated on γ-Al2O3. After analyses using in-situ plasma diffuse reflectance Fourier transform infrared spectroscopy and gas chromatography-mass spectrometry, it was found that most of C11 were degraded to CO2, and the main by-products on catalyst surfaces were alcohols and ketones. It was concluded from X-ray photoemission spectroscopy that the good performance of the 10 wt%CeO2/γ-Al2O3 catalyst was due to its high Ce3+/(Ce3++Ce4+) ratio as well as the oxygen vacancies. The Ce3+/(Ce3++Ce4+) ratio of CeO2 on γ-Al2O3 is crucial for the degradation of C11, providing a further roadmap for the plasma catalytic oxidation of alkanes.

New Strategy for Synthesis of Bis-Pocket Metalloporphyrins Enabling Regioselective Catalytic Oxidation of Alkanes

Abstract Cytochrome P450 selectively hydroxylates the ω and ω-1 positions of fatty acids. Among synthetic oxidizing catalysts, Suslick’s bis-pocket porphyrin Mn or Fe complex achieved ω oxidation for the first time, but the yield in the preparation of the catalyst was poor due to steric hindrance, and in addition, the catalyst turnover number in the oxidation reaction was low. We have devised a new synthetic strategy involving the introduction of eight bulky aryl groups at the 2,6-positions of the meso-phenyl groups after construction of the porphyrin skeleton. This strategy greatly improved the yield in synthesis of the catalyst, and a number of derivatives of bis-pocket porphyrin and their metal complexes were prepared. These Ru complexes show unique ω-1 selectivity and provide a much higher turnover number in the oxidation of linear alkane with 2,6-dichloropyridine N-oxide, as compared to the reaction catalyzed by conventional Ru porphyrins.

Polymer‐anchored mononuclear and binuclear CuII Schiff‐base complexes: Impact of heterogenization on liquid phase catalytic oxidation of a series of alkenes

Liquid phase catalytic oxidation of a number of alkenes, for example, cyclohexene, cis‐cyclooctene, styrene, 1‐methyl cyclohexene and 1‐hexene, was performed using polymer‐anchored copper (II) complexes PS‐[Cu (sal‐sch)Cl] (5), PS‐[Cu (sal‐tch)Cl] (6), PS‐[CH2{Cu (sal‐sch)Cl}2] (7) and PS‐[CH2{Cu (sal‐tch)Cl}2] (8). Neat complexes [Cu (sal‐sch)Cl] (1), [Cu (sal‐tch)Cl] (2), [CH2{Cu (sal‐sch)Cl}2] (3) and [CH2{Cu (sal‐tch)Cl}2] (4) were isolated by reacting CuCl2·2H2O with [Hsal‐sch] (I), [Hsal‐tch] (II), [H2bissal‐sch] (III) and [H2bissal‐tch] (IV), respectively, in refluxing methanol. Complexes 1–4 have been covalently anchored in Merrifield resin through the amine nitrogen of the semicarbazide or thiosemicarbazide moiety. A number of analytical, spectroscopic and thermal techniques, such as CHNS analysis, Fourier transform‐infrared, UV–Vis, PMR, 13C‐NMR, electron paramagnetic resonance, scanning electron microscopy, energy‐dispersive X‐ray analysis, thermogravimetric analysis, atomic force microscopy, atomic absorption spectroscopy, and electrospray ionization‐mass spectrometry, were used to analyze and establish the molecular structure of the ligands (I)–(IV) and complexes (1)–(8) in solid state as well as in solution state. Grafted complexes 5–8 were employed as active catalysts for the oxidation of a series of alkenes in the presence of hydrogen peroxide. Copper hydroperoxo species ([CuIII (sal‐sch)‐O‐O‐H]), which is believed to be the active intermediate, generated during the catalytic oxidation of alkenes, are identified. It was found that supported catalysts are very economical, green and efficient in contrast to their neat complexes as well as most of the recently reported heterogeneous catalysts.

Synthesis, Crystal Structures, and Catalytic Oxidation of Olefins of Novel Oxomolybdenum(VI) Clusters

Synthesis, Crystal Structures, and Catalytic Oxidation of Olefins of Novel Oxomolybdenum(VI) Clusters

Microbial Interconversion of Alkanes to Electricity

Electricity from fuels can be produced via 2 fundamentally different methods: By burning them to spin generators, or by direct abstraction of electrons at catalysts. The future is the flame-free production of electricity via catalysis, whereby the maximal theoretical yield scales inversely proportional to the process temperature. Low temperature fuel cells are thus needed, but they are not available for hydrocarbons due to the recalcitrant C-H bonds present in alkanes. Fuel cells for alkanes typically require process temperatures higher than 600 °C. The microbial pathway of anaerobic alkane oxidation, on the other side, converts alkanes reversibly to single electrons and CO2 at temperatures as low as 4 °C. In this perspective, I suggest to utilize this microbial metabolism for catalytic alkane oxidation at low temperatures, in order to convert alkanes to electricity with possibly higher thermodynamic efficiencies as current technologies. Alkane oxidation is partitioned into a biocatalytic (microbial) step to cleave the C-H bonds, and into an electrochemical step for harvest of electricity. In the biocatalytic step, the alkane is oxidized to CO2 and the resulting electrons are loaded onto an electron carrier. Electricity is then generated from the electron-carrier via fuel cells. Due to the intrinsic reversibility of the biochemical pathway, the whole process may be reversed to convert excess electricity (e.g. from solar or wind) with CO2 to alkanes, which is particularly interesting for the alkanes ethane, propane or butane that are easily liquefiable and storable.

Symmetric triazolylidene Ni(II) complexes applied as oxidation catalysts

A set of related Ni(II) complexes of N-heterocyclic carbene ligands (NHC) [trans-X2Ni(NHC)2] (X = Cl, I) bearing linear straight chain alkyl wingtip substituents have been synthesised and fully characterised. Single crystal XRD data revealed symmetrically aligned Ni(II) centres within square planar coordination of trans halide, trans NHC ligands. The complexes were used for the catalytic oxidation of alkanes under mild conditions in conjunction with tert-butyl hydroperoxide as an oxidant. Under optimised reaction conditions, the catalytic results pointed to good activities of circa 15% and 19% for cyclohexane and n-octane respectively. Furthermore, the catalytic systems are shown to be very efficient for the oxidation of linear alcohols to corresponding ketones.

Copper‐Functionalized Metal–Organic Framework as Catalyst for Oxidant‐Controlled Partial Oxidation of Cyclohexene

Microwave irradiation is exploited for the facile, one‐step functionalization of Cu(acac)2 to –NH2 pendant groups of MIL‐53(Al)‐NH2, a metal–organic framework material, under mild reaction conditions and a short reaction time. PXRD, XPS, XAS, and EPR spectroscopy are used to investigate the structure and chemical nature of the copper species on the framework. The copper center exists in the +2 oxidation state with a square‐planar geometry and NO3 coordination environment. The copper complex is anchored to the framework by imine bond formation. This copper‐functionalized MIL‐53(Al)‐NH2 or MIL‐53[Cu] is employed in the catalytic oxidation of olefins using molecular oxygen (O2) or tert‐butyl hydroperoxide (TBHP) as the oxidant. The chemoselectivities of the oxidation products depend on the type of oxidant and substrate. When O2 is used as the oxidant and isobutyraldehyde as the co‐oxidant in the oxidation of cyclohexene with MIL‐53[Cu], cyclohexene oxide is the major product. However, when TBHP is employed as the oxidant, 2‐cyclohexen‐1‐one is the major product. Furthermore, the catalyst can be reused at least three times without a significant loss in activity.

Synthesis, crystal structures, and catalytic oxidation of olefins of dioxomolybdenum(VI) complexes with aroylhydrazone ligands

Two Mo(VI) aroylhydrazone complexes, cis-[MoO2(L1)(CH3OH)] (I) and cis-[MoO2(L2)(CH3OH)] (II), derived from 2-bromo-N'-(3,5-dibromo-2-hydroxybenzylidene)benzohydrazide (H2L1) and 2-bromo-N'-(2-hydroxy-4-methoxybenzylidene)benzohydrazide (H2L2), respectively, are reported. The complexes were characterized by elemental analyses, infrared and electronic spectroscopy, and single crystal structure analysis (CIF files CCDC nos. 1443679 (I) and 1443678 (II)). The Mo atoms are coordinated by two cis terminal oxygen, ONO from the aroylhydrazone ligand, and methanol oxygen. Complex I crystallized as monoclinic space group P21/c with unit cell dimensions a = 8.075(2), b = 13.905(1), c = 16.448(1) A, β = 91.282(2)°, V = 1846.5(4) A3, Z = 4, R1 = 0.0859, wR2 = 0.2066. Complex II crystallized as triclinic space group P\(\overline 1 \), with unit cell dimensions a = 8.0824(6), b = 10.5919(8), c = 10.7697(8), α = 96.432(2)°, β = 97.438(2)°, γ = 103.119(2)°, V = 880.8(1) A3, Z = 2, R1 = 0.0271, wR2 = 0.0571. The complexes were tested as catalyst for the oxidation of olefins and showed effective activity.

Gabor A. Somorjai Award for Creative Research in Catalysis: John E. Bercaw

NATIONAL AWARDS Gabor A. Somorjai Award for Creative Research in Catalysis: John E. Bercaw ShareShare onFacebookTwitterWechatLinked InRedditEmail C&EN, 2017, 95 (1), pp 36–50January 2, 2017Cite this:C&EN 95, 1, 36-50John E. Bercaw (Credit: Bob Paz )Figure1of1Sponsor: Gabor A. & Judith K. Somorjai Endowment Fund Citation: For the elucidation of detailed mechanisms of organometallic reactions that comprise catalytic cycles. Current position: Centennial Professor Emeritus of Chemistry, California Institute of Technology Education: B.S., chemistry, North Carolina State University; Ph.D., chemistry, University of Michigan, Ann Arbor Bercaw on his scientific role model: “Harry Gray is one of my scientific role models. In addition to watching with amazement his scientific accomplishments, I have marveled at his enthusiasm, modesty, generosity, and love of interacting with students. He is truly a great man.” What his colleagues say: “Bercaw has made path-breaking contributions to developing and elucidating new homogenous catalytic reactions. His fundamental work in olefin polymerization catalysis and catalytic alkane oxidation is without equal.”—Maurice Brookhart, University of North Carolina, Chapel Hill

Catalytic oxidation of olefins and sulfides in the presence of hydrazone-oxidovanadium(V) complex containing VOCl2+ core

A new oxidovanadium(V) complex, [VO(L)Cl2] (1), is synthesized by the reaction of VOCl3 with (E)-N′-(phenyl(pyridin-2-yl)methylene)isonicotinhydrazide (HL) in chloroform as a solvent. The complex is characterized by elemental analysis, spectroscopic methods (FT-IR, UV–vis), and its structure is determined by single crystal X-ray diffraction analysis. X-ray studies reveal a mononuclear complex of V(V) with the hydrazone ligand coordinated to the V(V) center as a tridentate mononegative ligand. This complex is used as a catalyst precursor for oxidation of olefins and sulfides in the presence of hydrogenperoxide (H2O2) as a green oxidant. The effect of various parameters is studied including the amount of the catalyst, temperature and solvent. The results show the system corresponds to an active and selective catalyst for oxidation of cyclooctene and thioanisole.

Synthesis of titanium-containing helical silicates for catalytic oxidation of alkenes

A new series of titanium-containing helical silicates were prepared by doping of chiral sodium lactate in a sol–gel process. Characterizations revealed that the present titanium materials had good porosities, hexagonal symmetries, helical morphologies, as well as right-handed internal chiralities. Loading of chiral sodium lactate in preparation facilitated internal chiralities of synthetic products. In catalysis, the titanium materials showed moderate-to-excellent conversions, moderate-to-high stereoselectivities, and satisfactory recyclings for oxidation of aliphatic and aromatic alkenes by using solid oxidants such as iodobenzene diacetate and iodosylbenzene. Furthermore, both using ionic liquid as solvent and leaching of catalyst were studied. In general, titanium-containing chiral silicates were provided, and their applications in asymmetric catalysis were discussed too, which showed values on design of new efficient chiral catalysts.

Formation and High Reactivity of the anti-Dioxo Form of High-Spin μ-Oxodioxodiiron(IV) as the Active Species That Cleaves Strong C-H Bonds.

Recently, it was shown that μ-oxo-μ-peroxodiiron(III) is converted to high-spin μ-oxodioxodiiron(IV) through O-O bond scission. Herein, the formation and high reactivity of the anti-dioxo form of high-spin μ-oxodioxodiiron(IV) as the active oxidant are demonstrated on the basis of resonance Raman and electronic-absorption spectral changes, detailed kinetic studies, DFT calculations, activation parameters, kinetic isotope effects (KIE), and catalytic oxidation of alkanes. Decay of μ-oxodioxodiiron(IV) was greatly accelerated on addition of substrate. The reactivity order of substrates is toluene<ethylbenzene≈cumene<trans-β-methylstyrene. The rate constants increased proportionally to the substrate concentration at low substrate concentration. At high substrate concentration, however, the rate constants converge to the same value regardless of the kind of substrate. This is explained by a two-step mechanism in which anti-μ-oxodioxodiiron(IV) is formed by syn-to-anti transformation of the syn-dioxo form and reacts with substrates as the oxidant. The anti-dioxo form is 620 times more reactive in the C-H bond cleavage of ethylbenzene than the most reactive diiron system reported so far. The KIE for the reaction with toluene/[D8 ]toluene is 95 at -30 °C, which the largest in diiron systems reported so far. The present diiron complex efficiently catalyzes the oxidation of various alkanes with H2 O2 .

New aqua-soluble dicopper(ii) aminoalcoholate cores for mild and water-assisted catalytic oxidation of alkanes

Two new dicopper(ii) pre-catalysts were synthesized, fully characterized, and applied for the mild homogeneous oxidation of alkanes.

Ruthenium-Immobilized Periodic Mesoporous Organosilica: Synthesis, Characterization, and Catalytic Application for Selective Oxidation of Alkanes

Invited for the cover of this issue is the group of Kenji Hara and Atsushi Fukuoka at Hokkaido University (Japan). The image depicts the catalytic oxidation of alkanes over isolated Ru complexes formed on periodic mesoporous organosilica. Read the full text of the article at 10.1002/chem.201502638.

Efficient and selective oxidation of olefins and alcohols using nanoparticles of WO3-supported manganese oxides (W1−x Mn x O3)

Nanoparticles of manganese oxide supported on tungsten oxide (WO3) were synthesized by an impregnation method using Mn(NO3)2 and Na2WO4 as a source of manganese and tungsten. Atomic absorption spectroscopy (AAS), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize the physicochemical properties of compounds. Due to a highly dispersed state of manganese or insertion of manganese ions into the WO3 lattice, no manganese oxide peak was observed in the XRD patterns of the W1−x Mn x O3 nanoparticles. Investigation of W1−x Mn x O3 by AAS and EDX showed that the relative atomic abundance of Mn present in the bulk and on the surface of WO3 was 3.68% and 4.8% respectively. For the first time, the catalytic oxidation of olefins and alcohols, in the presence of these materials and hydrogen peroxide (H2O2) as a green oxidant at room temperature was studied. The recoverability and catalyst leaching of the W1−x Mn x O3 nanoparticles in epoxidation of styrene as a model reaction were also investigated.

Catalytic Oxidation of Alkanes and Alkenes by H2O2 with a μ‐Oxido Diiron(III) Complex as Catalyst/Catalyst Precursor

AbstractA new μ‐oxo diiron(III) complex of the lithium salt of the pyridine‐based unsymmetrical ligand 3‐[(3‐{[bis(pyridin‐2‐ylmethyl)amino]methyl}‐2‐hydroxy‐5‐methylbenzyl)(pyridin‐2‐ylmethyl)amino]propanoate (LiDPCPMPP), [Fe2(μ‐O)(LiDPCPMPP)2](ClO4)2, has been synthesized and characterized. The ability of the complex to catalyze oxidation of several alkanes and alkenes has been investigated by using CH3COOH/H2O2 (1:1) as an oxidative system. Moderate activity in cyclohexane oxidation (TOF = 33 h–1) and good activity in cyclohexene oxidation (TOF = 72 h–1) were detected. Partial retention of configuration (RC = 53 %) in cis‐ and trans‐1,2‐dimethylcyclohexane oxidation, moderate 3°/2° selectivity (4.1) in adamantane oxidation, and the observation of a relatively high kinetic isotope effect for cyclohexane oxidation (KIE = 3.27) suggest partial metal‐based oxidation, probably in tandem with free‐radical oxidation. Low‐temperature UV/Vis spectroscopy and mass spectrometric studies in the rapid positive detection mode indicate the formation of a transient peroxido species, [Fe2(O)(O2)(LiDPCPMPP)2]2+, which might be an intermediate in the metal‐based component of the oxidation process.