Selective Oxidation Of Cyclohexane Research Articles

Concepts of Heterogeneously Catalyzed Liquid‐Phase Oxidation of Cyclohexene with tert‐Butyl Hydroperoxide, Hydrogen Peroxide and Molecular Oxygen

AbstractThe oxidation of hydrocarbons is of great significance for the chemical industry as it provides access to valuable functionalized chemicals. The oxidation of cyclohexene has raised much interest because it enables the direct synthesis of adipic acid, which is an important building block in polymer chemistry. However, the selective oxidation of cyclohexene is rather challenging due to its two reactive centers so that epoxidation or allylic oxidation may occur leading to a variety of products. Whether the oxidation takes place at the allylic C−H bond or at the C=C bond is strongly influenced by the chosen oxidant and catalyst, and different reaction mechanisms can occur. Therefore, this concept article aims at giving a broad overview of the recent advances in the selective cyclohexene oxidation over heterogeneous transition metal‐based catalysts using environmentally benign oxidants like tert‐butyl hydroperoxide, H2O2 and molecular O2.

Design of Prussian Blue Analogue-Derived Magnetic Binary Ce–Fe Oxide Catalysts for the Selective Oxidation of Cyclohexane

Design of Prussian Blue Analogue-Derived Magnetic Binary Ce–Fe Oxide Catalysts for the Selective Oxidation of Cyclohexane

Synthesis of a highly active Nb2O5 for 1,2-cyclohexanediol production

A commercial niobium oxide was used to form a gelled material, which was lyophilized producing a novel polyoxoniobate catalyst (L-AmNbO) containing peroxo groups. The activity of this new catalyst was assessed through oxidation reactions of the cyclohexene. In the presence of L-AmNbO catalyst, the oxidation of cyclohexene with H2O2 reached 90% of conversion after 12 h at 75 °C, with selectivity for 1,2-cyclohexanediol (∼ 50%). The catalytic results and the surface properties of this new material indicated that it can be a promising catalyst for niobium compounds applications in the selective oxidation of cyclohexene.

Three new zinc(II) complexes: design, synthesis, characterization and catalytic performance

Three new Zn(II) complexes, [Zn2L2(OAc)2]2CH3OH (1), [ZnL(3-NA)2]·H2O (2) and [ZnL(2-NA)2] (3) were synthesized by the reaction of Zn(CH3COO)2·2H2O or Zn(ClO4)2·6H2O with 2-amino-N'-(pyridin-2-ylmethylene)benzohydrazide (HL), 3-nitrobenzoic acid (3-NA) or 2-nitrobenzoic acid (2-NA). The complexes were characterized by elemental analyses, single crystal X-ray diffraction, IR, UV-Vis and 1H NMR spectroscopy. The single crystal X-ray diffraction analyses revealed that the Zn ions in the complexes are five-coordinate in tetragonal pyramid configuration. The complexes and their starting materials Zn(CH3COO)2·2H2O and Zn(ClO4)2·6H2O were studied for their catalytic performance in the selective oxidation of cyclohexane (Cy) with aqueous H2O2 as oxidant. The conditions such as time, the amount of H2O2, solvent and HNO3 additive were optimized. The results showed that 3 has the best activity under mild conditions compared to the starting zinc materials and the referenced zinc complexes.

Poly(ionic liquid)s hollow spheres nanoreactor for enhanced cyclohexane catalytic oxidation

Hollow structure nanoreactors take advantage of catalyst loading and enhanced activity by shell construction. In this work, functionalized poly(ionic liquid)s (PILs) with hollow spherical structures were synthesized by polymerization- and quaternization-based approaches. These hollow structure PILs (HPILs) could be controllable designed from IL monomer easily, giving HPILs various properties. In the subsequent selective oxidation of cyclohexane, the HPILs acting as nanoreactors could efficiently improve the activity of metal salt catalysts (CoCl2) and displayed adjustable selectivity for cyclohexanone, cyclohexanol (KA) or adipic acid (AA) by different types of HPILs. In kinetic study, it follows first-order reaction kinetics which CoCl2/HPIL-C12 had a lower the activation energy of 29.1 kJ/mol. Importantly, these nanoreactors storing the catalysts could be recovered and reused more than 7 times without significant loss of activity. A theoretical model for the hollow spherical reactor was further established to support the advance of the HPILs reactor, which could also help to predict reaction process in other core-shell catalytic system. Due to controlled substrate transfer and enhanced radical generation in HPILs, the reaction process could be adjusted to enhance the conversion of cyclohexane and selective oxidation to AA.

Selective oxidation of cyclohexane over the bi-functional catalysts Co-MO-TUD-1 (MO = Al2O3, CeO2, NiO, or ZnO)

Selective oxidation of cyclohexane over the bi-functional catalysts Co-MO-TUD-1 (MO = Al2O3, CeO2, NiO, or ZnO)

Valence Band Edge Engineering of Mixed Metal Oxides Photocatalysts Derived from Transition Metal Intercalated Layered Double Hydroxide Towards Selective Oxidation of Cyclohexane Under Visible Light

Valence Band Edge Engineering of Mixed Metal Oxides Photocatalysts Derived from Transition Metal Intercalated Layered Double Hydroxide Towards Selective Oxidation of Cyclohexane Under Visible Light

Valence Band Edge Engineering of Mixed Metal Oxides Photocatalysts Derived from Transition-Metal-Based Layered Double Hydroxide Towards Selective Oxidation of Cyclohexane Under Visible Light

Valence Band Edge Engineering of Mixed Metal Oxides Photocatalysts Derived from Transition-Metal-Based Layered Double Hydroxide Towards Selective Oxidation of Cyclohexane Under Visible Light

Valence Band Edge Engineering of Mixed Metal Oxides Photocatalysts Derived from Transition-Metal-Based Layered Double Hydroxide Towards Selective Oxidation of Cyclohexane Under Visible Light

Valence Band Edge Engineering of Mixed Metal Oxides Photocatalysts Derived from Transition-Metal-Based Layered Double Hydroxide Towards Selective Oxidation of Cyclohexane Under Visible Light

Phase-dependent photocatalytic selective oxidation of cyclohexane over copper vanadates

Three copper vanadates with different crystal phases show different abilities for selective oxidation of cyclohexane.

Mesoporous SBA-15 supported gold nanoparticles for solvent-free oxidation of cyclohexane: superior catalytic activity with higher cyclohexanone selectivity.

Surface modification of mesoporous SBA-15 with (3-mercaptopropyl) trimethoxysilane greatly enhances its capability to adsorb the tetrachloroauric anion (AuCl4-). The calcination of the sample after the adsorption experiment led to the generation of homogeneously dispersed, spherical, single crystalline gold nanoparticles (Au0 NPs) of less than 5 nm size, embedded on SBA-15 as observed from the TEM images. The as-prepared SBA-15/Au0 nanohybrid material has offered excellent catalytic activity for the selective oxidation of cyclohexane using TBHP as the oxidant in the absence of any solvent. A maximum of 48.7% cyclohexane conversion was achieved and surprisingly, cyclohexanone (K) has much higher selectivity (>95%) than cyclohexanol (A). The hot-filtration study confirmed the leach-resistant characteristics as well as the true heterogeneous catalytic activity of the SBA-15/Au0 nanohybrid catalyst. The catalyst was recycled up to four times without significant loss in its catalytic activity.

Direct synthesis of Cu-containing Beta zeolite without template for selective oxidation of cyclohexane

Direct synthesis of Cu-containing Beta zeolite without template for selective oxidation of cyclohexane

Carbon supported copper catalyst prepared in situ by one-pot pyrolysis of Bougainvillea glabra: An efficient and stable catalyst for selective oxidation of cyclohexane

So far, the poor stability of Cu2O is still the major challenge in heterogeneous catalysis. Herein, Bougainvillea glabra (B. glabra) derived carbon supported copper composite (Cu2O/BGC) was synthesized in situ by one-pot pyrolysis method. In the synthetic strategy, B. glabra was used as reductant and carbon source simultaneously, and copper nitrate as copper precursor. Cu2O/BGC exhibited a significant enhancement in both catalytic activity and stability for cyclohexane oxidation with tert-butyl hydroperoxide as oxidant under solvent-free condition. Cu2O/BGC with a Cu/C ratio of 0.8 calcined at 800 °C showed the highest catalytic cyclohexane conversion efficiency (77.1%) and cyclohexanone selectivity (68.5%). Its turnover number (TON) is 12.2- and 1.3-fold compared to pure Cu2O and Cu2O/BGC prepared by deposition-reduction method, respectively. Hot filtration experiment confirmed that the sample was a heterogeneous catalyst which could be reused five times without losing its activity.

Photo-thermo catalytic selective oxidation of cyclohexane by In-situ prepared nonstoichiometric Molybdenum oxide and Silver-palladium alloy composite

The highly selective oxidation of cyclohexane to cyclohexanone and cyclohexanol (KA oil) is one of the most challenging issues in the chemical industry. However, the difficulty in attaining high selectivity and high conversion rate in parallel for the existing catalysts limits its practical application. In this paper, a novel photo-thermo synergistic catalyst was reported for the aerobic oxidation of cyclohexane. The uniform blue MoO3-x nanowires with small diameter stabilized by polyvinyl pyrrolidone (PVP) were synthesized by a hydrothermal method, and a series of MoO3-x-AgPd composite materials of different proportions were prepared by an in-situ reduction process. The morphology, crystalline structure, surface chemical bonding, photoelectrochemical properties of MoO3-x-AgPd composites are thoroughly characterized. The MoO3-x-AgPd composites present significantly increased catalytic performance than MoO3-x nanowires in the photo-thermo synergistic catalytic oxidation of cyclohexane under dry air. The high conversion rate of 11.3% with the KA oil selectivity of 99.0% was achieved by the MoO3-x-Ag20Pd20 composites under photo-thermo catalytic process at 120 ℃, which is 1.5 times of that by MoO3-x nanowires. Under photo-thermo catalytic process, a high cyclohexane conversion rate similar to that of higher temperature thermal catalysis can be obtained at lower reaction temperature, and more cyclohexanol can be produced with a ketone to alcohol (K/A) ratio of 0.254. The significantly enhanced catalytic activity can be attributed to the effective charge transfer in the AgPd alloy nanoparticles, the optimized band gap structure, the suppressed charge recombination, and the promoted photo-thermo synergetic catalytic effect. This work provides a new reference scheme for the design and preparation of high-efficiency photo-thermo catalysts for the selective oxidation of cyclohexane.

Construction of Indium Oxide/N-Doped Titanium Dioxide Hybrid Photocatalysts for Efficient and Selective Oxidation of Cyclohexane to Cyclohexanone

Construction of Indium Oxide/N-Doped Titanium Dioxide Hybrid Photocatalysts for Efficient and Selective Oxidation of Cyclohexane to Cyclohexanone

Synthesis and characterization of Pd-Ni catalysts supported on KIT-6 and their application in cyclohexane oxidation using molecular oxygen

Bimetallic Pd-Ni catalysts were prepared via impregnation method, with effects of Pd/Ni ratio (wt%) on their catalytic performance for the oxidation of cyclohexane with molecular oxygen being investigated. Synthesized catalysts were characterized by a series of techniques including XRD, Nitrogen adsorption–desorption, H2-TPR, XPS, ICP-AES, TEM, SEM, and EDX. Compared to monometallic Pd, the addition of Ni to Pd was found to be effective in enhancing the selective oxidation of cyclohexane. Parameters such as the temperature of the reaction, reaction times, catalyst amount, initial oxygen pressure and different solvents were investigated. Optimum conditions to improve cyclohexane conversion and selectivity towards KA-oil (a mixture of cyclohexanone and cyclohexanol) over 4.0%Pd-4.0%Ni/KIT-6 catalyst included 140 °C, 1.0 MPa O2 and acetonitrile as solvent. Under these reaction conditions, 10.87 % conversion and 95.45 % selectivity for KA-oil were observed after 8 h of reaction. Reusability studies of the selected catalyst revealed an outstanding stability along four reaction cycles.

Oxidation of Cyclohexane using Copper–Nickel Catalyst

The copper–nickel oxide catalyst was prepared by the incipient wetness impregnation method for the selective oxidation of cyclohexane. The catalysts 25Cu100−xNix/Al2O3 were characterized by surface area, XRD, H2-TPR, FE-SEM, and Raman spectra analysis. The investigation revealed that an optimum ratio of copper to nickel, calcination temperature of the catalyst, and the suitable support play a crucial role in converting cyclohexane, and yield of product (KA oil). The catalyst 25Cu50Ni50/Al2O3 showed a significantly higher conversion of cyclohexane compared to a single-metal oxide catalyst. The enhancements of conversion by the bimetallic oxides catalyst were due to the synergistic effect of copper–nickel bimetallic oxides. The support also plays a significant role in the increase in conversion of cyclohexane, and the order of KA oil selectivity followed as 25Cu50Ni50/Al2O3 > 25Cu50Ni50/SiO2 > 25Cu50Ni50/MgO.

Efficient and selective oxidation of cyclohexane to cyclohexanone over flake hexagonal boron nitride/titanium dioxide hybrid photocatalysts

• A flake h -BN/TiO 2 hybrid photocatalyst was successfully synthesized by hydrolysis-precipitation method. • h -BN/TiO 2 photocatalyst exhibited enhanced photocatalytic activity and selectivity. • A desired efficient and selective oxidation of CHA to CHA-one was achieved. • Possible mechanism for enhancing photocatalytic performance was proposed. Selective oxidation of cyclohexane (CHA) with oxygen (O 2 ) to product cyclohexanone (CHA-one) is an important reaction for the modern chemical industry. The present work constructs a flake hexagonal boron nitride/titanium dioxide ( h -BN/TiO 2 ) hybrid photocatalyst to achieve a desired selective and efficient oxidation of CHA to form CHA-one with a mild and green condition under atmospheric pressure, at room temperature, and in solvent-free. The activity of 14 wt% h -BN/TiO 2 composite is significantly enhanced to about four times as compared with that of bare TiO 2 . Moreover, the CHA-one selectivity of 14 wt% h -BN/TiO 2 composite (>85%) is much higher than that of pure TiO 2 (approximately 60%). Additionally, h -BN/TiO 2 composites can also display superior cycling stability and recoverability. The reasons for the promoted photocatalytic performance of h -BN/TiO 2 were revealed by the photo-electrochemical experiments and DFT calculations. Both the negatively charged h -BN and its flake structure can effectively enhance valence band holes transfer from the inside of TiO 2 to h -BN surface, and further improve the separation of photoformed hole-electron pairs to promote photocatalytic performance. The present approach will contribute to the build of more efficient photo-oxidation systems and to the construction of advanced composite photocatalysts for selective oxidation.

The Selective Oxidation of Cyclohexane via In-situ H2O2 Production Over Supported Pd-based Catalysts

The oxidation of cyclohexane via the in-situ production of H2O2 from molecular H2 and O2 offers an attractive route to the current industrial means of producing cyclohexanone and cyclohexanol (KA oil), key materials in the production of Nylon. The in-situ route has the potential to overcome the significant economic and environmental concerns associated with the use of commercial H2O2, while also allowing for the use of far lower reaction temperatures than those typical of the purely aerobic route to KA oil. Herein we demonstrate the efficacy of a series of bi-functional Pd-based catalysts, which offer appreciable concentrations of KA oil, under conditions where limited activity is observed using O2 alone. In particular the introduction of V into a supported Pd catalyst is seen to improve KA oil concentration by an order of magnitude, compared to the Pd-only analogue. In particular we ascribe this improvement in catalytic performance to the development of Pd domains of mixed oxidation state upon V incorporation as evidenced through X-ray photoelectron spectroscopy.Graphic

Nitrogen-doped mixed-phase TiO2 with controllable phase junction as superior visible-light photocatalyst for selective oxidation of cyclohexane

Nitrogen-doped anatase/rutile mixed-phase TiO2 photocatalysts with carbonaceous species were successfully fabricated by pyrolyzing MIL-125 (Ti) and P25 composite as the precursor, and subsequently doping nitrogen into the pyrolysis product using urea as the dopant in a sealed reactor. Through varying the addition amount of P25 in the precursor, the ratios of anatase/rutile phases in the photocatalysts were conveniently adjusted. The photocatalysts showed excellent photocatalytic cyclohexane oxidation performances under visible light irradiation. The yield of the KA oil (cyclohexanol and cyclohexanone) reached 112.44 μmol after 5 h illumination for the photocatalyst with the optimal anatase/rutile ratio (N-TiO2-3), which was 5.66 and 39.87 times that of N-TiO2-0 (nitrogen-doped anatase TiO2) and N-P25 (nitrogen-doped P25), respectively. In the meantime, the selectivity toward cyclohexanone could reach 100%. The influences of pyrolysis temperature and atmosphere on the microstructure of catalysts and resulting catalytic performances for cyclohexane oxidation were also investigated. The improved photocatalytic properties were attributed to the combined effects of the high visible-light absorption caused by nitrogen doping, valid separation of photogenerated electron-hole pairs derived from the mixed-phase junction, unique auxiliary function of carbonaceous species and porous structure. A possible photocatalytic mechanism was proposed according to the active species determined by trapping experiments.