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• A polyvinylpyrrolidone (PVP) coating of fluffy self-assembled morphology of BiOCl by nanosheets with exposed {001} facets are synthesized via the solvothermal method. • The as-synthesized hierarchical BiOCl-P exhibits a significant presence of in-situ produced oxygen vacancies during photocatalysis. • The BiOCl-P achieved highly efficient and selective CHA photooxidation to KA oil with air as an oxidant in solvent-free at room temperature. • Possible mechanism for boosting photocatalytic performance was proposed. Cyclohexane (CHA) selective oxidation reactions are crucial in designing advanced organic intermediates but suffering from very challenges as the products of KA oil (cyclohexanol and cyclohexanone) are more readily oxidized to CO 2. Herein, we report that a polyvinylpyrrolidone (PVP) coating of fluffy self-assembled morphology of BiOCl by nanosheets with exposed {001} facets are synthesized via the solvothermal method. Moreover, the as-synthesized hierarchical BiOCl exhibits a significant presence of in-situ produced oxygen vacancies during photocatalysis, thereby facilitating efficient CHA oxidation to KA oil with air as an oxidant in solvent-free at room temperature. The crystallinity, micromorphology, and electronic structure of BiOCl can be significantly influenced by the concentration of NH 4 Cl and PVP. In the photocatalytic oxidation, oxygen vacancies act as traps to inhibit electrons and holes recombination and adsorb-activate the oxygen molecule, producing h + and ·O 2 − radical to achieve 466.7 μmol of KA oil (340.8 μmol of cyclohexanone and 125.9 μmol of cyclohexanol) with a selectivity of 93.9 %. The ∙OH radicals play a predominant role in the production of CHA-one. After conducting 5 experimental cycles, a consistent yield of 92 % towards KA oil and unchanged selectivity can still be maintained. The excellent photocatalytic performance can be attributed to the enhanced photo-absorption and narrow energy gap, abundant oxygen vacancies, high exposed {001} facets, smaller size and large specific surface area, and efficient electron-hole separation. The present work sheds light on the synergistic effect of PVP coating and in-situ formed oxygen vacancies on enhancing photocatalytic activity of Bi-based materials. [Display omitted] [ABSTRACT FROM AUTHOR]

• BiOI photocatalysts were synthesized at different pH values and characterized. • Cyclohexane oxofunctionalization was performed under visible light. • All BiOI samples showed higher selectivity for cyclohexanol than cyclohexanone. • Cyclohexanol yield was related to the exposed crystal facets of BiOI. • The higher cyclohexanol yield was associated with production of •OH. The development of semiconductors capable of photocatalytic activity under visible light is very important, because such materials are potentially useful for performing photocatalytic conversion under solar illumination. However, these processes are frequently unselective because they involve the production of free radicals. Reports suggest that the selectivity of the photocatalytic processes may be adjusted through modification of the structural parameters of the semiconductor photocatalysts by the preferential exposure of certain crystalline planes. The present work focuses on the relationship between the preferential exposure of the (1 1 0) and (0 0 1) facets of bismuth oxyiodide and the cyclohexanol produced by the photocatalytic oxofunctionalization of cyclohexane. For this purpose, four bismuth oxyiodide photocatalysts (BiOI-4, BiOI-6, BiOI-10, and BiOI-12) were synthesized at different pH levels and characterized (via X-ray diffraction, diffuse reflectance spectroscopy, scanning electron microscopy, and the Brunauer–Emmett–Teller surface area). All BiOI photocatalysts showed higher selectivity for cyclohexanol. Additionally, a linear dependence between the cyclohexanol yield and peak intensity (1 1 0)/(0 0 1) ratio was established and related to the relative amount of hydroxyl radicals formed in the photocatalytic system. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • VOCl 2 was use for the first time in photocatalytic oxidation of cyclohexane. • VOCl 2 exhibited much higher photocatalytic activity and selectivity. • The addition of HCl could promote the oxidation reduction process of V5+/V4+. • VO2+ species could be converted to VO 2 + species in the coexistence of light and O 2. • VO 2 + species played important roles in photocatalytic oxidation of cyclohexane. Abstract The efficient selective oxidation of cyclohexane to cyclohexanone and cyclohexanol (KA-oil) under mild conditions remains one of the most challenging and interesting projects in catalytic chemistry. Here, photocatalytic oxidation of cyclohexane was carried out in acetonitrile (MeCN) solution of VOCl 2 under Xe lamp irradiation and pure O 2 atmosphere. The results show that VOCl 2 has high photocatalytic activity in pure MeCN solution, and a cyclohexane conversion of 17.8% with ca. 99% selectivity for KA-oil can be obtained after light irradiation of 4 h. It is worth noting that the use of hydrochloric acid as an additive can effectively enhance the photo-catalytic oxidation of cyclohexane, providing a cyclohexane conversion of 23.3%, which may be due to the important role of HCl in improving the light absorption, decreasing the oxidation-reduction potential of V5+/V4+ and promoting the redox process of photocatalyst. The effects of photocatalyst concentration, hydrochloric acid addition amount, O 2 pressure and reaction time on photocatalytic performance were also studied. It was found that the optimization of these reaction conditions can further improve the conversion of cyclohexane and selectivity of KA-oil. A possible reaction mechanism for the photocatalytic oxidation of cyclohexane was proposed. [ABSTRACT FROM AUTHOR]

Highlights • Mixed-trophies biofilm for the cultivation of high cell density photobiocatalysts. • O 2 toxification was overcome by respiration, extraction, and biotransformation. • Mixed-trophies biofilms produce 3.76 g m−2 day−1 cyclohexanol for over a month. • Cyclohexane conversion of 98% and KA oil selectivity of 100% was obtained. Abstract Photosynthetic microorganisms have enormous potential to produce fuels and value-added compounds sustainably. Efficient cultivation concepts that enable optimal light and CO 2 supply are necessary for the realization of high cell densities (HCDs), and subsequently for process implementation. We introduce capillary biofilm reactors with a high surface to volume ratio, and thus enhanced light availability, enabling HCDs of photo-autotrophic microorganisms. However, oxygenic photosynthesis leads to O 2 accumulation in such systems, impairing biofilm growth. We combined O 2 producing Synechocystis with O 2 respiring Pseudomonas using proto-cooperation to achieve HCDs of up to 51.8 g BDW L−1. This concept was coupled to the challenging C-H oxyfunctionalization of cyclohexane to cyclohexanol with a remarkable conversion of >98% and selectivity of 100% (KA oil). High photoautotrophic biocatalyst concentrations were established and resulted in a productivity of 3.76 g cyclohexanol m−2 day−1, which was maintained for at least one month. [ABSTRACT FROM AUTHOR]

Abstract Nano-sized plate-like alumina is an important inorganic material in catalytic, ceramic and electronic applications due to its unique two-dimensional structure and properties, while its facile synthesis is still under investigation. In this work, nano-sized alumina plate was synthesized by solution combustion method with glycine and polyvinyl alcohol as composite fuels for the first time. The calcination temperature during solution combustion process was optimized as confirmed by XRD, FT-IR, TG-DSC, Raman, 27Al MAS NMR, SEM, TEM, and N 2 physisorbtion. Obtained alumina displayed special nano-sized plate morphology and porous structure. It was further adopted as support for cobalt acetate and used as catalyst for selective oxidation of cyclohexane. This work develops a facile approach to synthesize two-dimensional plate-like alumina for catalytic application. [ABSTRACT FROM AUTHOR]

The present study involved preparing of the barbiturate derivatives and corresponding copper(II) complexes. Catalytic activities of the copper(II)-barbiturate complexes were examined for the peroxidative oxidation of cyclohexane. Barbiturate derivatives were prepared by the reaction of 5-formylbarbiturates and primary aryl amines. The corresponding copper(II) complexes were synthesized by treatment of copper(II) acetate monohydrate with the prepared barbiturate derivatives. All the novel compounds were characterized by elemental analysis and spectroscopic methods. The structures of 3b and 3j were determined with X-ray crystallography. The X-ray crystallographic studies revealed that complexes 3b and 3j are 2-D coordination polymers. Also, the catalytic activities of the copper(II) complexes were examined for the peroxidative oxidation of cyclohexane under mild conditions. The results showed that the yields of the oxidation products were in the range 11.3–22.1%, depending upon the complex used and the promoter. [ABSTRACT FROM AUTHOR]

Abstract First-row-transition-metal silica coated magnetite nanoparticles (MNPs), Fe 3 O 4 @SiO 2 -M2+ [M = Mn2+ (1), Co2+ (2), Cu2+ (3) or Zn2+ (4)], were evaluated as catalysts for the selective oxidation of cyclohexane to cyclohexanone and cyclohexanol. The catalytic reaction occurred under mild conditions, using microwave-assisted heating in added solvent-free medium producing water as the only by-product. The manganese (1) and copper (3) surface enriched silica-coated MNPs leaded to the highest yield of oxygenated products (24% and 21%, respectively) after 2 h at 80 °C using hydrogen peroxide as oxidant. These surface modified MNPs can be readily isolated by using an external magnet and no significant loss of activity is observed when reused up to 5 consecutive runs. Graphical abstract Unlabelled Image Highlights • Novel, eco-friendly KA oil synthesis. • Reusable, stable magnetic Fe 3 O 4 @SiO 2 -M2+ nanocatalysts. • Solvent-free microwave-assisted selective oxidation of cyclohexane. [ABSTRACT FROM AUTHOR]

The selective one‐step aerobic oxidation of cyclohexane to ϵ‐caprolactone was achieved in the presence of N‐hydroxyphthalimide (NHPI) and aldehyde under mild conditions. Remarkably, 12 % of cyclohexane was converted with a selectivity of 77 % of ϵ‐caprolactone and 15 % of KA oil. Control experiments indicated that NHPI accelerated the oxidation of aldehydes and peroxy radicals generated from aldehydes in situ were the key intermediates in the period of CH bond activation. 2,2,6,6‐Tetramethylpiperidine 1‐oxyl (TEMPO) addition and a series of m‐chloroperoxybenzoic acid (m‐CPBA) oxidation experiments showed that the oxidation proceeded via a complex radical chain mechanism. [ABSTRACT FROM AUTHOR]

In the present study, the simultaneous production of formaldehyde and hydrogen is investigated in a thermally-coupled reactor. In the proposed reactor, production of formaldehyde as an exothermic reaction occurs in the tube side, while the dehydrogenation of cyclohexane (CH) which is an endothermic reaction takes place in the shell side. The endothermic reaction also acts as a heat absorber, which controls the temperature profile of the exothermic side. Based on flow direction, two possible arrangements, co-current and counter-current are considered and compared. The former shows better performance. Finally, the effect of important parameters on the performance of conventional and coupled reactor is examined. • Producing hydrogen by dehydrogenation of cyclohexane as hydrogen carrier. • Thermal coupling of methanol oxidation and cyclohexane dehydrogenation is proposed. • Proposing a novel autothermal bifunctional reactor to perform the coupling idea. • The operation of two arrangements, co- and counter-current flow pattern, is compared. • Increasing formaldehyde production by about 132 tons per year. [ABSTRACT FROM AUTHOR]

Graphical abstract Dinuclear complexes of Cu(II) and Ni(II) with 1-((2-hydroxyethylimino)methyl)naphthalen-2-ol have been synthesized, characterized and explored as catalyst for the oxidation of cyclohexane, toluene and cyclopentane using hydrogen peroxide as the oxidant. Copper(II) complex has been found to be active catalyst for oxidation of these hydrocarbons whereas nickel(II) complex is not. Highlights • Dinuclear Cu(II) and Ni(II) complexes with a Schiff-base ligand were synthesized. • They were characterized by standard methods including single crystal X-ray diffraction. • Copper(II) complex was active catalyst for oxidation of saturated hydrocarbons. • Nickel(II) complex acted as inactive in the same catalysis. Abstract Oxidation of saturated hydrocarbon by transition metal complexes is of great importance because this would give industrially valuable organic fine chemicals. Here, dinuclear copper(II) and dinuclear nickel(II) complexes with same N,O donor ligand have been used as catalyst for the oxidation of cyclohexane, toluene and cyclopentane using hydrogen peroxide as the oxidant to examine their catalytic activity and effect of nature of metal center on catalysis. [Cu 2 (L1) 2 (μ 2 -Cl)Cl]·2.5H 2 O (1) and [Ni 2 (L1) 2 (μ 2 -N 3) 2 (CH 3 OH) 2 ]·CH 3 OH (2) have been synthesized under mild conditions where HL1 is 1-((2-hydroxyethylimino)methyl)naphthalen-2-ol. These complexes have been characterized by elemental analysis, FT-IR, UV-Vis, mass spectroscopy, TGA-DTA and cyclic voltametric studies. Their structures have been confirmed by single crystal X-ray diffraction analysis. Some theoretical calculations have been performed to investigate spectral transitions. Copper(II) complex shows effective catalytic ability towards oxidation of the saturated hydrocarbons such as cyclohexane, toluene and cyclopentane in the presence of hydrogen peroxide when corresponding alcohols and ketones have been obtained as major products. However, complex 2 has been found to be inactive as catalyst for the oxidation. It is possible that Cu-hydroperoxo or Cu-peroxo species is formed during catalysis (as revealed from UV-vis spectral analysis) which could be the active species for the oxidation reaction. [ABSTRACT FROM AUTHOR]

Graphical abstract Total yields (cyclohexanol + cyclohexanone) up to 90% were achieved in cyclohexane oxidation using ethyl acetate, which is an efficient green solvent to replace dichloromethane. Abstract The selective cyclohexane oxidation to cyclohexanone and cyclohexanol based on a green strategy has been a challenge. A new manganese porphyrin [MnIII(T2,4,5TMPP)Cl] was prepared and its activity and selectivity as a catalyst were studied together with the classical manganese porphyrin [MnIII(TPP)Cl] using green solvents (dimethyl carbonate or ethyl acetate) and solvent-free systems. The effects of the solvent (or its absence), oxidant, and co-catalyst were investigated. Under the studied conditions, the new catalyst showed a higher selectivity for cyclohexanol (above 78%) in solvent-free systems compared to the [MnIII(TPP)Cl]. The highest total yield of the products (89%) was observed in ethyl acetate/PhIO/water system. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • d°-Vanadate shows superior visible-light responsiveness. • Heteroatom-tuning vanadates can alter the competitive reaction pathways. • Electronic structure of vanadates interface to various reaction intermediates change. • BiVO 4 promotes the oxidation with the higher TOF (7.5 h−1) than Cu 3 V 2 O 8 (2.8 h−1). • A different KA-oil selectivity is obtained for BiVO 4 (95%) and Cu 3 V 2 O 8 (54%). Abstract Structure-function correlation constitutes a central theme in the selective photocatalytic oxidation of cyclohexane with molecular oxygen, as a result of precise tailoring band-structure towards KA-oil selectivity. Herein, we comparatively and systematically investigate the correlation among optical properties, electronic structure, and photocatalytic performance of two d°-vanadate photocatalysts (BiVO 4 and Cu 3 V 2 O 8) using theoretical calculations and experimental techniques. Results show that BiVO 4 promotes the selective oxidation pathway under visible-light irradiation with higher efficiency (TOF = 7.5 h−1, based on the molar amount of V sites) and chemoselectivity (cyclohexanone/cyclohexanol molar ratio = 3.0) than the Cu 3 V 2 O 8. Meanwhile, the photocatalytic performance of BiVO 4 demonstrates high photocatalytic selectivity towards KA-oil (95%), while Cu 3 V 2 O 8 seems to facilitate the accommodation of chlorine promoters, leading to very different chlorocyclohexane selectivity (46%). Such the distinct photocatalytic performances of BiVO 4 and Cu 3 V 2 O 8 can be ascribed to their unique electronic structures to facilitate the e−−h+ charge carriers and generation of reactive species during photoirradiation. The Bi3+ 6p states of BiVO 4 are predominant components of the conduction band minimum (CBM) and hybridize with Bi3+ 6 s , and O2− 2p and V5+ 3d orbitals at the valence band maximum (VBM); whereas the Cu2+ 3d and V5+ 3d orbitals contribute to the CBM of Cu 3 V 2 O 8 , and Cu2+ 3d , O2− 2p and V5+ 3d orbitals at the VBM. So BiVO 4 with s − p matrix elements is more effective than the Cu 3 V 2 O 8 in producing OH, h+ and H 2 O 2 , which can rapidly oxidize the C − Cl band cleavage for chlorocyclohexane intermediate to regenerate newly Cl radicals in the next cycle reactions. Heteroatom-tuning of photocatalytic performance is further supported by universal evidences from experimental results by replacing Bi or Cu of the above vanadates with Ag, La, Sr, Fe or Ti atom and the study of the electrons, holes and radicals mediated reaction pathway by scavengers, respectively. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Preparation of μ-nitrido diiron phthalocyanine@oxide support. • Cyclohexane oxidation was conducted under mild condition. • Various metal oxide supports were employed and compared. • Acidic support afforded enhanced catalytic activity and stability. Abstract Various oxides, including Al 2 O 3 , Fe 2 O 3 , SiO 2 , and ZrO 2 , were employed as catalyst supports for the oxidation of cyclohexane by a μ-nitrido-bis[tetra(tert-butyl)phthalocyaninatoiron] complex. These oxide supports were characterized by Brunauer–Emmett–Teller surface area measurements and NH 3 temperature-programmed desorption analyses. The catalyst supported on Al 2 O 3 , which has the highest acidity among the oxides considered here, showed the best activity with a turnover number (TON) of ˜108.8, without any co-catalyst. Furthermore, recycle tests of the catalysts revealed a TON of 69.3 for the Al 2 O 3 -supported catalyst after the third run. The strongly acidic sites in the Al 2 O 3 support could be responsible for the strong adsorption of μ-nitrido diiron phthalocyanine, resulting in enhanced catalytic activity and stability. [ABSTRACT FROM AUTHOR]

The mechanisms of formation and transformation of cyclohexyl hydroperoxide, cyclohexanol, and cyclohexanone in the liquid-phase oxidation of cyclohexane are reviewed. Cyclohexyl hydroperoxide is formed in chain propagation reactions and decomposes via the degenerate branching reactions under the action of alkoxyl, alkyl, and peroxyl radicals, as well as via nonradical channels to form alcohol and ketone. The radicals of two types, HO 2 ⋅ radical and α-hydroxycyclohexylperoxyl radical, are involved in chain propagation in the course of cyclohexanol oxidation. In the chain propagation reactions, HO 2 ⋅ radicals are more reactive than α-hydroxycyclohexylperoxyl radicals. The dynamic equilibrium was established in the dissociation of 1-hydroxycyclohexylperoxyl radical to cyclohexanone and radical HO 2 ⋅ . During oxidation of cyclohexane, cyclohexanone is formed from peroxyl radicals, as well as by the decomposition of cyclohexyl hydroperoxide and chain-radical oxidation of cyclohexanol. The oxidation of cyclohexanone in positions 2 and 6 affords 2-hydroperoxycyclohexanone, which predominantly decomposes to form 2-hydroxycyclohexanone. The oxidation of 2-hydroxy-cyclohexanone proceeds via the main channels of destruction of the carbon chain of cyclohexane leading to adipic acid and adipic anhydride. The oxidation products of C—H bonds of all types in alcohol and ketone are accumulated simultaneously with the oxidation products of C(1)—H bonds in cyclohexanol and of C(2)—H and C(6)—H bonds in cyclohexanone. [ABSTRACT FROM AUTHOR]

In this work, we will report the generation of Au clusters in a purely siliceous MCM-22 zeolite. The catalytic properties of these Au clusters have been tested for the selective oxidation of cyclohexane to cyclohexanol and cyclohexanone (KA-oil). The Au clusters encapsulated in the MCM-22 zeolite are highly active and selective for the oxidation of cyclohexane to KA-oil, which is superior to Au nanoparticles on the same support. These results suggest that Au clusters are highly active for the activation of oxygen to produce radical species. [ABSTRACT FROM AUTHOR]

We aimed at elevating catalytic performances of cobalt tetrakis(pentafluorophenyl)porphyrin (Co TPFPP) through axial coordination, nanocavities, and covalently grafting action. The Co TPFPP was immobilized onto nanoporous and nonporous chitosan, forming Co TPFPP/np‐ and nonp‐CTS catalysts, respectively. The catalysts were characterized by various spectroscopic techniques. The catalytic performances of these catalysts for cyclohexane oxidation under response‐surface‐methodology‐optimized oxidation reaction conditions were estimated and compared. Co TPFPP/np‐CTS was an excellent catalyst at aspect of catalytic activity, exhibiting the considerable potential reusability, 24.2 mol % yields (KA oil : cyclohexanone and cyclohexanol) in average, and total turnover frequencies (TOFs) of 3.25×106 h−1. This is attributed to the structural characteristics of the Co TPFPP/np‐CTS catalyst: the cobalt porphyrin molecules could be highly scattered on CTS, forming the independent active sites, and were not leached. The axial coordination exerted the most important effect on the catalytic activity, and the covalent grafting action had a decisive effect on the increase of the total TOFs and on the reusability of the catalyst. Stable foundations: Cobalt tetrakis(pentafluorophenyl)porphyrin (Co TPFPP) immobilized on nanoporous (Co TPFPP/np‐CTS) is an excellent catalyst, which offers 24.2 mol % average yields (KA oil) and a total turnover frequency (TOF) of 3.25×106 h−1 in cyclohexane oxidation. The cobalt porphyrins are highly scattered on CTS and the axial coordination exerted the most important effect on the catalytic activity. The grafting action mainly has an affect on the catalyst stability. [ABSTRACT FROM AUTHOR]

The selective oxidation of cyclohexane (CHA) is still a significant challenge in the field of current catalysis chemistry and chemical industry. Here, nano-V2O5/Ti porous membrane electrodes with different morphologies, i.e., nanorods (NRs), nanosheets (NSs), and nanoparticles (NPs), were prepared by loading nano-V2O5 onto porous Ti membranes. Simultaneously, a nano-V2O5/Ti membrane electrode was employed to constitute an electrocatalytic membrane reactor (ECMR) for CHA oxidation. Results indicated that the electrochemical performance was significantly associated with the morphology of the nano-V2O5 catalysts on the membrane electrode. ECMR with V2O5 NSs/Ti electrode exhibited superior properties. Excellent electrochemical activity was obtained in the application of CHA oxidation with 28.4% conversion and 99.9% selectivity to cyclohexanone and cyclohexanol (KA oil), which is better than most noble-metal-based catalysts reported in the literature under aerobic reaction conditions. Further, a prominent catalytic activity (10.5% conversion and 99.5% selectivity to KA oil) was first achieved even under 0 °C. The preferable electrocatalytic performance of V2O5 NSs/Ti electrode for CHA oxidation was attributed to the large effective electrocatalytic surface area, high electron transfer rate, and high rate of hydroxyl radical (ṖOH) generation. Furthermore, the mechanism of CHA oxidation was explored. It was established that the valence change of V catalysts is an essential step during the selective oxidation of CHA by ECMR. Moreover, the V2O5 NSs/Ti electrode displayed excellent stability of oxidation during the selective oxidation of CHA. Therefore, our research opens up a new avenue toward the fundamental understanding and design of nanocatalysts in heterogeneous and electrochemical catalysis. [ABSTRACT FROM AUTHOR]

Liquid phase oxidation of cyclohexane, by molecular oxygen, has been carried out using cobalt molybdenum oxide (CoMoO 4 ) catalyst supported on mesoporous silica supports (SBA-15, KIT-6 and FDU-12). For each support, the catalyst activity has been studied as a function of loading, pore size, and calcination temperature. The catalysts were characterized using surface area analysis (BET), X-ray diffraction (XRD), and transmission electron microscopy (TEM). Among the three supported catalysts, the one on FDU-12 shows the highest activity. The catalysts with lower loading, lower calcination temperature and lower pore size of support show higher activity but with lower selectivity. All the studied catalysts gave about 7–8% conversion, with selectivity of 85% for cyclohexanone and cyclohexanol (KA oil), before deactivation took over. The deactivated catalysts could be fully regenerated by re-calcination in every case. With such regeneration between runs, the catalysts are shown to retain their activity and selectivity over multiple cycles. The kinetic model which was proposed for the unsupported catalyst has been shown to work well for the supported catalysts as well. [ABSTRACT FROM AUTHOR]

The future development of chemistry entails environment-friendly and energy-sustainable alternatives for organic transformations. Visible light photo-catalysis can address these challenges. Octahedral molecular sieve manganese oxide (cryptomelane, OMS-2) and Fe-doped OMS-2 nano-structures were prepared to be used as affective visible light photo-catalysts for the oxidation of cyclohexane. The photo-catalysts were prepared by reflux method (at 100°C, for 24 h) under atmospheric pressure by using different molar ratios of Fe/Mn (0, 0.03, 0.08 and 0.10). Several techniques such as X-ray diffraction, transmission electron microscopy, Fourier-transform infrared spectra, nitrogen adsorption/desorption isotherms and thermal analysis were performed for characterizing the structure and the morphology of the prepared samples. The results revealed that the Fe-OMS-2 samples have a well-crystalline cryptomelane framework. In addition, no peaks related to the Fe dopant were detected, indicating the incorporation of Fe species into the framework of cryptomelane. The main product of photo-catalytic oxidation reaction of cyclohexane is cyclohexanone with a selectivity of 100% after 3 h for highest conversion on using 0.08Fe-OMS-2 sample. [ABSTRACT FROM AUTHOR]

In this study, a C-doped Cr2O3/NaY composite membrane supported on stainless steel mesh with layer-by-layer structure was successfully synthesized and used in the partial oxidation of cyclohexane. In the composite membrane, NaY zeolite membrane acted as absorbent and the C-doped Cr2O3 behaved as photocatalyst, which was successfully prepared using a chromium-containing MOF as precursor. The supported composite membrane was characterized by a series of analysis techniques. Comparing with the stainless steel mesh-supported C-doped Cr2O3 membrane, the supported C-doped Cr2O3/NaY composite membrane exhibited superior visible-light-driven photocatalytic performance for cyclohexane oxidation. This is due to its layer-by-layer structure and NaY membrane with high surface areas and polarity which can preferentially adsorb KA oil products, avoiding their overoxidation. [ABSTRACT FROM AUTHOR]

Reaction of sodium (E/Z)-2-(2-(1-cyano-2-methoxy-2-oxoethylidene)hydrazinyl)benzene-sulfonate (NaHL) with copper(II) nitrate hydrate in the presence of imidazole (im) in methanol affords [CuL(im)(H 2 O)] ( 1 ). Complex 1 is characterized by IR spectroscopy and ESI-MS spectrometry, elemental and single crystal X-ray crystal structural analyses. The coordination environment of the central copper(II) is nearly intermediate between ideal square-based pyramidal and trigonal bipyramidal geometry, three sites being occupied by the L 2− ligand, which chelates in the O, N, O fashion, while two other sites are filled with the water and imidazole molecules. Extensive intermolecular hydrogen bonds between the L 2− , water and imidazole ligands lead to a 3D supramolecular network. 1 and known Cu(II) complexes [Cu(H 2 O) 2 L]·H 2 O ( 2 ), [Cu(H 2 O)(py)L]·H 2 O ( 3 ) and [Cu 3 (µ 3 -OH)(NO 3 )(CH 3 OH)(µ 2 -X) 3 (µ 2 -HL)] ( 4 ) act as effective catalysts in the oxidation of cyclohexane to cyclohexanol and cyclohexanone, using low power microwave (MW) irradiation, under mild conditions. Without a promoter, the activity of the catalyst reached a turnover number of 1.44 × 10 3 and a turnover frequency of 1.98 × 10 3  h −1 , after 2 h, at 50 °C. [ABSTRACT FROM AUTHOR]

For the first time, a magnetic C-scorpionate catalyst was prepared from the iron(II) complex [FeCl2{κ3-HC(pz)3}] (pz = pyrazol-1-yl) and ferrite, using the sustainable mechanochemical synthetic procedure. Its catalytic activity for the cyclohexane oxidation with tert-butyl hydroperoxide (TBHP) was evaluated in different conditions, namely under microwave irradiation and under the effect of an external magnetic field. The use of such magnetic conditions significantly shifted the catalyst alcohol/ketone selectivity, thus revealing a promising, easy new protocol for tuning selectivity in important catalytic processes. [ABSTRACT FROM AUTHOR]

Рассмотрен способ усовершенствования процесса жидкофазного окисления циклогексана. Определен положительный эффект кислородосодержащей добавки - Бис-2 цианетилового этера - на основные технико-экономические показатели процесса - конверсию сырья, селективность по продуктах окисления и соотношение целевых продуктов. Исследовано оптимальное соотношение компонентов бинарной каталитической системы. Предложен комплексный метод использования продуктов окисления циклогексана путем утилизации полученных побочных кислот эстерификацией их со спиртами. [ABSTRACT FROM AUTHOR]

Coupling reaction of cyclohexyl hydroperoxide (CHHP) decomposition and cyclohexane oxidation in the process of catalytic decomposition of CHHP was identified via cyclopentane instead of cyclohexane used as solvent. A method was established to evaluate this coupling reaction. Based on this method, it can be accurately distinguished the product of cyclohexanol and cyclohexanone (K/A oil) derived from whether decomposition of CHHP or oxidation of cyclohexane. The established method is of great significance to the further study of the coupling reaction. [ABSTRACT FROM AUTHOR]

The design of efficient and stable clay based materials for catalytic technologies is a great challenge. We demonstrated a new approach of fabricating vanadium incorporated silica-pillared clay by interlayered self-assembly synthetic route. And such synthetic route utilized tartaric acid as the complexing reagent, both dodecyl dimethyl benzyl ammonium bromide and octadecylamine as the mixed structure-directing agent. The obtained vanadium-containned silica-pillared clay samples were characterized by X-ray fluorescence, X-ray diffraction, transmission electron microscopy, N 2 adsorption-desorption isotherms, Fourier-transform infrared spectroscopy, diffuse reflectance ultraviolet–visible spectroscopy and X-ray photoelectron spectroscopy techniques. Characterization results indicate that there is an important correlation between the concentration of octadecylamine and uniform structure of the obtained vanadium-containned sample. The octadecylamine is not only used as swelling agency but also decreases the polarity to confirm the uniform mesoporous structure form in the interlayered regions. It was generally considered that hydrothermal synthesis bears the advantage of incorporating active metal ions into the framework in the tetrahedral coordination with V 4+ state under the combined action of complexing reagent and mixed structure-directing agent. And the V 2 O 5 phase was gradually formed via aggregation and agglomeration of increasing highly dispersed vanadium species. The catalytic behaviour and performance was examined using the selective oxidation of cyclohexane. The obtained catalyst possesses larger surface area and mesoporous volume and uniform slit-shaped mesopores, which are beneficial to the diffusion of the vanadium atom and responsible for higher yield of the KA oil. And the mechanism associated with the porous structure change has also been discussed. [ABSTRACT FROM AUTHOR]

In this research, strontium titanate ( $$\hbox {SrTiO}_{3})$$ nanoparticles were synthesised using an ultrasonic method, then were doped with Pt using a photo-assisted deposition method to form $$\hbox {Pt}/\hbox {SrTiO}_{3}$$ nanoparticles. $$\hbox {SrTiO}_{3}$$ and $$\hbox {Pt}/\hbox {SrTiO}_{3}$$ nanoparticles were characterized by XRD, XPS, TEM, BET surface area UV-Vis and PL techniques in order to explore their chemical and physical properties. The visible light irradiation photocatalytic performances of $$\hbox {SrTiO}_{3}$$ nanoparticles and $$\hbox {Pt}/\hbox {SrTiO}_{3}$$ nanoparticles for photocatalytic oxidation of cyclohexane was investigated, and the results revealed that platinum was doped onto the $$\hbox {SrTiO}_{3}$$ nanoparticles surfaces as metallic platinum, and the weight percent of doped platinum greatly affected the band gap, and the 1.5 wt% $$\hbox {Pt}/\hbox {SrTiO}_{3}$$ nanoparticles showed the highest photocatalytic activity due to the low band gap. The stability of the $$\hbox {Pt}/\hbox {SrTiO}_{3}$$ nanoparticles for the photocatalytic oxidation of cyclohexane was examined and the results revealed that the $$\hbox {Pt}/\hbox {SrTiO}_{3}$$ nanoparticles could be used five times without losing their efficiency. Graphical Abstract: TEM images of $$\hbox {SrTiO}_{3 }$$ (A) and 1.5 wt% $$\hbox {Pt}/\hbox {SrTiO}_{3}$$ (B) nanoparticles, which showed that $$\hbox {SrTiO}_{3}$$ is a spherical nanoparticle (A) and that platinum was doped as dots (B). [ABSTRACT FROM AUTHOR]

A new bis(μ-chlorido)-bridged cobalt(II) complex [Co2(μ-Cl)2(HL²)4][CoCl4] (1), where HL² is a silyl-containing Schiff base, was synthesised. The structure of this compound was established by X-ray crystallography revealing a zwitterionic form adopted by the organic ligand. The temperature dependence of the magnetic susceptibility and the field dependence of the magnetisation indicate the presence of ferromagnetic interactions between paramagnetic d7 cobalt(II) centres (SCo = 3/2). The exchange coupling parameter J(Co1-Co2) = +7.0 cm-1 extracted from broken-symmetry (BS) DFT calculations agrees well with the value of +8.8 cm-1 determined from the experimental data by fitting them with the Hamiltonian Ĥ = -JCo1-Co2exch ŜCo1·ŜCo2. Electrochemical studies indicate that complex 1 is inefficient as a catalyst in electrochemical reduction of protons. One of the reasons is the low stability of the complex in solution. In contrast, 1 acts as an effective homogeneous (pre)catalyst in the microwave-assisted neat oxidation of cyclohexane with aqueous tBuOOH (TBHP). The possible mechanism of catalytic oxidation and other advantages of using 1 in the oxidation of cycloalkanes are discussed. [ABSTRACT FROM AUTHOR]

A porphyrinic metal–organic framework (MOF), PCN-222(Fe), was found to exhibit sound activity and selectivity to cyclohexanone and cyclohexanol (known as KA oil) toward cyclohexane oxidation. Remarkably, hydrophobicity engineering of the MOF pore walls led to significantly enhanced activity and selectivity to KA oil, far superior to that of the homogeneous porphyrin catalyst. [ABSTRACT FROM AUTHOR]

The liquid-phase oxidation of cyclohexane to cyclohexanol and cyclohexanone was investigated by synthesizing and testing an array of heterogeneous catalysts comprising: monometallic Ag/MgO, monometallic Pd/MgO and a set of bimetallic AgPd/MgO catalysts. Interestingly, Ag/MgO was capable of a conversion comparable to current industrial routes of approximately 5 %, and with a high selectivity (up to 60 %) to cyclohexanol, thus making Ag/MgO an attractive system for the synthesis of intermediates for the manufacture of nylon fibres. Furthermore, following the doping of Ag nanoparticles with Pd, the conversion increased up to 10 % whilst simultaneously preserving a high selectivity to the alcohol. Scanning transmission electron microscopy and energy dispersive spectroscopy of the catalysts showed a systematic particle-size-composition variation with the smaller Ag-Pd nanoparticles being statistically richer in Pd. Analysis of the reaction mixture by electron paramagnetic resonance (EPR) spectroscopy coupled with the spin-trapping technique showed the presence of large amounts of alkoxy radicals, thus providing insights for a possible reaction mechanism. [ABSTRACT FROM AUTHOR]

To improve the understanding of low temperature oxidation of methyl cyclohexane, the potential energy surfaces for O 2 addition to two of its radicals ( t cy -C 6 H 10 (*)CH 3 with a tertiary radical site and ortho - cy -C 6 H 10 (*)CH 3 with a secondary radical site in the ortho position to the methyl substitution) have been investigated by high level quantum chemical calculations. The reaction kinetics was studied by the ab initio transition state theory based on master equation methodology. The relationship between low temperature oxidation reactivity and molecular structures was explored, typically in terms of the barrier heights of 1,5 H-shift for peroxy radicals. The computed phenomenological rate constants reveal that the ROO stabilization dominates the fates of two methyl cyclohexyl radicals reacting with O 2 at pressures higher than 1 atm over the studied temperature range. The balance between ROO stabilization, HO 2 elimination, QOOH stabilization, and OH formation was further revealed by branching ratios of these four types of reactions. This study extends kinetic data for cyclic alkanes oxidation in a wide range of pressure and temperature. [ABSTRACT FROM AUTHOR]

The highly efficient dibenzodioxin-forming reaction between the (pentafluorophenyl)porphyrin manganese(III) (MnP) and hexahydroxytriptycene (HHT) provide a new microporous network polymer (P1) , which demonstrated a large surface area (1080 m 2 g − 1 ) and proved to be an efficient solid for heterogeneous catalysis for cyclooctene and cyclohexane oxidation under mild conditions and with high capacity of recovery and reuse in many catalytic cycles. [ABSTRACT FROM AUTHOR]

BACKGROUND Zeolite encapsulated transition metal complexes have proven to be better catalysts for most organic transformations as they share advantages of both homogeneous and heterogeneous catalysts because the complex inside the zeolite cage can move within the cavity but at the same time cannot come out of it owing to its size. Hence, some reports claim application of these encapsulated complexes in various organic transformations. Introduction of bromine into aromatic compounds is an important fundamental reaction in organic chemistry. On the other hand, oxidations of saturated and unsaturated compounds also find application in the synthesis of fine chemicals. RESULTS The positions of peaks in the cyclic voltammogram of the encapsulated complex were unaltered, accompanied by an increase in current with scan rate, substantiating encapsulation of the complex within the cavity. This complex was catalytically active in the presence of H2O2 towards the oxidation of cyclohexane and ethylbenzene. Its catalytic efficiency was examined in the oxidative bromination of organic substrates using KBr at room temperature, wherein high para-selectivity was obtained. It displayed better conversion/selectivity than Fe(opbmzl) 2NO3 retaining its catalytic activity up to five consecutive runs. Plausible mechanisms involving hydro-peroxo intermediate have been proposed. CONCLUSION Zeolite encapsulated bis[2,2'-hydroxyphenylbenzimidazole]Fe( III) complex behaved as a versatile catalyst for various organic transformations. © 2017 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Magnetic cobalt ferrite (CoFe 2 O 4 ) 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 m 2 /g) were prepared, which were assembled by CoFe 2 O 4 particles of uniform sizes ( ca. 15.0 nm). The annealed CoFe 2 O 4 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 O 2 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. [ABSTRACT FROM AUTHOR]

This study investigates how ligands modulate metalloporphyrin activity with the goal of producing a practical biomimetic catalyst for use in the chemical industry. We immobilized iron porphyrinate [iron-tetrakis-(4-sulfonatophenyl)-porphyrin; Fe(III) (TPPS)] on powdered chitosan (pd-CTS) to form an immobilized catalyst Fe(III) (TPPS)/pd-CTS, which was characterized using modern spectroscopic techniques and used for catalytic oxidation of cyclohexane with O 2 . Amino coordination to iron porphyrin in Fe(III) (TPPS)/pd-CTS altered the electron cloud density around the iron cation, probably by reducing the activation energy of Fe(III) (TPPS) and raising the reactivity of the iron ion catalytic center, thereby improving the catalytic efficiency. One milligram of Fe(III) (TPPS) catalyst can be reused three times for the oxidation reaction to yield an average of 22.9 mol% of cyclohexanone and cyclohexanol. [ABSTRACT FROM AUTHOR]

The activity and selectivity of vanadium phosphate (VPO) catalysts on the mesoporous KIT-6 support for green oxidation of cyclohexane to cyclohexanone and cyclohexanol were studied using H 2 O 2 . The catalysts were characterized using XPS, XRD, ICP-AES, TEM, SEM, EDX, BET, FT-IR and adsorption of pyridine. Small angle X-ray diffraction spectroscopy confirmed formation of well-ordered mesoporous KIT-6 material. The BET analysis showed a high surface area and well-ordered support formed. The XRD analysis demonstrated the loaded VPO existed almost wholly as VOHPO 4 0.5H 2 O phases and after calcination converted mainly to the form of (VO) 2 P 2 O 7 phase on KIT-6. XPS analysis revealed that a vanadium oxidation state of catalyst is approximately 4+. Within the studied range, the optimum condition to improve cyclohexane conversion and selectivity towards KA-oil (a mixture of cyclohexanone and cyclohexanol) over vanadium containing catalyst was performed in the presence of 27 wt% catalyst VP-loading at 65 °C with 1:4 (cyclohexane: H 2 O 2 ) molar ratio, in acetonitrile. Under these reaction conditions 19.3% conversion and 69.9% selectivity for KA-oil were observed after 4 h of reaction time. Finally, the recyclability of the catalyst was studied through five consecutive catalytic runs. [ABSTRACT FROM AUTHOR]

The efficient single-pot oxidative functionalisation of alkanes and alcohols under mild conditions was catalysed by Au nanoparticles supported on Al2O3, Fe2O3, ZnO and TiO2. The obtained materials were tested for cyclohexane oxidation under mild conditions (60 °C, atmospheric pressure) using an environmentally friendly oxidant (H2O2). The materials were also tested in the oxidation of benzyl alcohol and methylbenzyl alcohol in the presence of tert-butylhydroperoxide as the oxidant under microwave irradiation. With regard to cyclohexane oxidation, all materials were highly selective towards the formation of cyclohexanol and cyclohexanone. No traces of byproducts were detected under the optimised conditions. Au on Fe2O3 led to the best results (13.5 % yield). This system showed an interesting almost exclusive formation of cyclohexanol at 4 h reaction time. Catalyst recycling was tested in up to five cycles, and the catalyst maintained almost the original level of activity after three cycles with no significant leaching. With regard to oxidation of benzyl alcohol and methylbenzyl alcohol, all materials were highly selective towards the formation of benzaldehyde or acetophenone, respectively. No traces of byproducts were detected. Addition of Au increased alcohol conversion from 5 (TiO2) to 91 % (Au/TiO2). The recycling of Au/TiO2 was tested in up to 10 cycles, and the catalytic activity remained high in the first four cycles. [ABSTRACT FROM AUTHOR]

The two-fluid model was applied to simulate the hydrodynamics based on the process conditions in a cyclohexane oxidation airlift loop reactor (ALR). A lab-scale ALR was first investigated to validate the simulation methods and the simulated gas holdup and liquid velocity agree well with the experimental data. Following the validation, computational fluid dynamics (CFD) was then extended to study the industrial scale cyclohexane oxidation ALR. The CFD results indicate that the key hydrodynamic parameters for the circulation flow are the liquid circulation velocity and liquid circulation flux. The increasing liquid circulation flux in the downcomer enhances the downcomer gas holdup, while the increasing liquid circulation velocity in the riser reduces the riser gas holdup. The factor influencing the gas phase entrainment in the draft-tube is the liquid circulation flux rather than the liquid circulation velocity. With a constant reactor diameter, the gas holdup and liquid circulation flux increases with the increasing cross-sectional area ratio of downcomer to riser. The draft-tube with a horn-mouth can efficiently enhances the gas–liquid separation at the reactor top. Within a certain range, the axial position height of the draft-tube can influence the circulation driving force and resistance loss in the reactor. The results of this study are significant for guiding production, the optimization and scale-up study of this kind of reactors. [ABSTRACT FROM AUTHOR]

The highly selective aerobic oxidation of cyclohexane to cyclohexanone and cyclohexanol (KA-oil) under benign and green conditions is still a challenging topic. In this work, V2O5@TiO2 catalysts were prepared by V species deposited on TiO2 (P25) and characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (XRD), and UV-vis diffuse reflectance techniques. The selective aerobic oxidation of cyclohexane was carried out over V2O5@TiO2 catalysts with oxygen as an oxidant under simulated light irradiation. The influences of solvents, metals and mass of V species deposited on TiO2, pressure of oxygen, and reaction time on the reaction were investigated. It was found that the V species deposited on the TiO2 surface was very efficient for the photocatalytic oxidation of cyclohexane under simulated solar light irradiation. More interestingly, the selectivity of the reaction in an acetonitrile/water mixed solvent was much higher than that in other solvents. Under the optimized conditions, the selectivity to KA-oil products could be nearly 100% at a cyclohexane conversion of 18.9%. The possible pathway for the catalytic reaction was proposed. [ABSTRACT FROM AUTHOR]

The complexes of copper [Cu(κ ONN ’-HL)(NO 3 )(DMF)](NO 3 )∙H 2 O ( 1 ) and [Cu(κ ONN ’-HL)Cl 2 ]∙½DMSO ( 2 ), and of manganese [Mn(κ ON -HL) 2 Cl 2 ]Cl ( 3 ) and [Mn(κ ON -HL) 2 (NO 3 ) 2 ](NO 3 )∙H 2 O ( 4 ) were synthesized by reactions of the respective chloride or nitrate salt with a non-aqueous solutions of the Schiff base aminoalcohol HL (product of condensation of salicylic aldehyde and aminoethylpiperazine) and characterized by X-ray diffraction analysis. The catalytic investigations disclosed a prominent activity of the copper compounds 1 and 2 towards oxidation of cyclohexane with hydrogen peroxide in the presence of various promoters (nitric, hydrochloric, oxalic acids and pyridine), under mild conditions. The unusual promoting effect of pyridine on the catalytic activity of the copper catalysts allowed to achieve yields up to 21% based on cyclohexane. Chromatographic studies revealed that cyclohexyl hydroperoxide is a main reaction product and chlorocyclohexane (in the presence of HCl as promoter) was also detected, suggesting a free radical reaction pathway with hydroxyl radicals as attacking species. Complexes 1 and 2 act also as catalysts in the oxidation of 1-phenylethanol with tert -butylhydroperoxide, showing acetophenone yields up to 62% and TON (turnover numbers) up to 620 in the presence of the K 2 CO 3 promoter. [ABSTRACT FROM AUTHOR]

Metal--organic frameworks are a new class of heterogeneous catalysts in which molecular-level control over both the immediate and long-range chemical environment surrounding a catalytic center can be readily achieved. Here, the oxidation of cyclohexane to cyclohexanol and cyclohexanone is used as a model reaction to investigate the effect of a hydrophobic pore environment on product selectivity and catalyst stability in a series of iron-based frameworks. Specifically, expanded analogues of Fe2(dobdc) (dobdc4- = 2,5-dioxido-l,4-benzenedicarboxylate) were synthesized and evaluated, including the biphenyl derivative Fe2(dobpdc) (H4dobpdc = 4,4'-dihydroxy-[l,l'-biphenyl]-3,3'-dicarboxylic acid), the terphenyl derivative Fe2(dotpdc) (H4dotpdc = 4,4"- dihydroxy-[l,l':4',l"-terphenyl]-3,3"-dicarboxylic acid), and three modified terphenyl derivatives in which the central ring is replaced with tetrafluoro-, tetramethyl-, or di-ferf-butylaryl groups. Within these five materials, a remarkable 3-fold enhancement of the alcohohketone (A:K) ratio and an order of magnitude increase in turnover number are achieved by simply altering the framework pore diameter and installing nonpolar functional groups near the iron site. Mossbauer spectroscopy, kinetic isotope effect, and gas adsorption measurements reveal that variations in the A:K selectivities arise from differences in the cyclohexane adsorption enthalpies of these frameworks, which become more favorable as the number of hydrophobic residues and thus van der Waals interactions increase. [ABSTRACT FROM AUTHOR]

Copper complexes bearing readily available ligand systems catalyzed the oxidation of alkanes with H2O2 as the oxidant with high efficiency in remarkable yields (50-60 %). The reactions proceeded with unprecedented selectivity to give alkyl hydroperoxides as the major products. Detailed scrutiny of the reaction mechanism suggests the involvement of C-centered and O-centered radicals generated in a Fenton-like fashion. [ABSTRACT FROM AUTHOR]

Here, we report on structure-reactivity trends for cyclohexane oxidative dehydrogenation (ODH) with silica supported copper oxide catalysts as a function of surface structure. Copper oxide was supported on mesostructured KIT-6 silica at low surface densities <0.2 Cu/nm 2 using copper (II) nitrate, ammonium and sodium copper (II) ethylenediaminetetraacetate, and a hexanuclear copper (I) siloxide complex. Copper oxide surface structures were characterized by X-ray absorption spectroscopy as well as ambient and in situ diffuse reflectance UV–visible (DRUV–vis) spectroscopy to determine trends in copper oxide nuclearity. DRUV–vis spectroscopy identifies three copper species based on Cu 2+ ligand to metal transfer (LMCT) bands at 238, 266, and >300 nm as well as Cu + LMCT bands at 235, 296, and 312 nm. Counterintuitively, EXAFS analysis shows that the multinuclear precursor leads to fewer average Cu–Cu interactions than syntheses with mononuclear copper salt precursors. Turnover frequency and selectivity to benzene increase with decreasing copper oxide nuclearity, and thus the multinuclear precursor leads to the highest turnover frequency and benzene production. This work shows the variety of surface species that exist even at extremely low copper surface densities, control of which can improve reactivity of an atypical ODH catalyst up to rates comparable to benchmark vanadia catalysts. [ABSTRACT FROM AUTHOR]

Naphthalene-2-ol is a typical biologically recalcitrant pollutant in dye wastewater. Solvent extraction of naphthalene-2-ol from aqueous solutions using mixed solvents was investigated. Various extractants and diluents were evaluated, and the effects of volume ratio of extractant to diluent, initial pH, initial concentration of naphthalene-2-ol in aqueous solution, extraction time, temperature, volume ratio of organic phase to aqueous phase (O/A), stirring rate and extraction stages, on extraction efficiency were examined separately. Regeneration and reuse of the spent extractant were also investigated. Results showed that tributyl phosphate (TBP) achieved 98% extraction efficiency for naphthalene-2-ol in a single stage extraction, the highest among the 12 extractants evaluated. Extraction efficiency was optimized when cyclohexane and n -octane were used as diluents. The solvent combination of 20% TBP, 20% n -octanol and 60% cyclohexane ( V / V ) obtained the maximum extraction efficiency for naphthalene-2-ol, 99.3%, within 20 min using three cross-current extraction stages under the following extraction conditions: O/A ratio of 1:1, initial pH of 3, 25°C and stirring rate of 150 r/min. Recovery of mixed solvents was achieved by using 15% ( W / W ) NaOH solution at an O:A ratio of 1:1 and a contact time of 15 min. The mixed solvents achieved an extraction capacity for naphthalene-2-ol stably higher than 90% during five cycles after regeneration. [ABSTRACT FROM AUTHOR]

Cu(II), Co(II), Mn(II) and Ni(II) complexes of silica-supported N 4 O 4 type bis (diazoimine) ligands were synthesized and characterized by using FT-MIR/FAR, TG/DTA, elemental analysis, ICP-OES, SEM and EDX techniques. Catalytic activities of the complexes were investigated on the selective oxidation of cyclohexane, cyclohexene, cyclooctane and styrene under microwave power. In cyclohexane oxidation, L1-Cu(II) catalyst showed the best catalytic activity with the conversion of 73.31% and 46.05% cyclohexanol and 34.87% cyclohexanone selectivity. L1-Cu(II) and L2-Cu(II) catalyst were selective for 2-cyclohexen-1-ol (40.54% and 65.01%) in the cyclohexene oxidation with high conversions (66.77% and 54.59%). Cycloctanone selective L1-Cu(II), L2-Cu(II), L2-Cu(II) and L1-Ni(II) (75–80%) complexes showed very selective catalytic properties in the catalytic oxidation of cyclooctane. L1-Ni(II), L2-Ni(II) and L3-Ni(II) catalysts have had 81.28%, 73.70% and 81.39% selectivities respectively in styrene oxidation. Generally, it can be said that Cu(II) complexes are highly active and selective catalysts on the oxidation of cyclohexane, cyclohexene and cyclooctane. Nevertheless, Ni(II) complexes of L1 and L2 showed important selective catalytic performances towards the epoxidation of styrene. [ABSTRACT FROM AUTHOR]

The reaction of the Schiff base (3,5-di-tert-butyl-2-hydroxybenzylidene)-2-hydroxybenzohydrazide (H3L) with a copper(II) salt of a base of a strong acid, i.e., nitrate, chloride or sulphate, yielded the mononuclear complexes [Cu(H2L)(NO3)(H2O)] (1), [Cu(H2L)Cl]μ2MeOH (2) and the binuclear complex [{Cu(H2L)} 2 (μ-SO4)]μ2MeOH (3), respectively, with H2Lμ in the keto form. Compounds 1-3 were characterized by elemental analysis, Infrared (IR) spectroscopy, Electrospray IonisationMass Spectrometry (ESI-MS) and single crystal X-ray crystallography. All compounds act as efficient catalysts towards the peroxidative oxidation of cyclohexane to cyclohexyl hydroperoxide, cyclohexanol and cyclohexanone, under mild conditions. In the presence of an acid promoter, overall yields (based on the alkane) up to 25% and a turnover number (TON) of 250 (TOF of 42 h-1) after 6 h, were achieved. [ABSTRACT FROM AUTHOR]

Transition metal supported porous carbon materials have become a promising aspirant in energy storage, solid catalysis, and material chemistry. Palladium, gold, and gold–palladium anchored carbon composites (CPC-25/170, CGC-25/170, andCGPC-25/170) with two different sized carbon cages (∼25 and 170 nm) were constructed using nano-silica ball (NSB) as the template and a pyrolysis fuel oil (PFO) based pitch residue as the carbon source. The Pd, Au, and Au–Pd doped carbon nanoreactors were characterized by various physicochemical analysis methods. The developed materials were used as heterogeneous catalysts for the oxidation of cyclohexane to cyclohexanol and cyclohexanone using H2O2at room temperature (25°C) and atmospheric pressure. The most active catalystCGC-170showed combined cyclohexanol and cyclohexanone yield of 7.7% after 4 h reaction time. The conversion of 2.4%, 0.05%, and 0.32% was achieved usingCGC-25, CGPC-25, andCGPC-170catalysts, respectively. Recyclability of the catalysts maintains no observable loss of performance during catalytic oxidation reaction. [ABSTRACT FROM AUTHOR]

Ag nanoparticles (with 2–5 nm size) supported on Mn3O4 nanorods were prepared in the presence of the cationic surfactant cetrimonium bromide using a hydrothermal method. The material was characterized in detailed by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, scanning transmission electron microscopy-mapping, Raman spectroscopy, Fourier-transformed infrared spectroscopy and inductively coupled plasma-atomic emission spectroscopy. Electron microscopy studies revealed the formation of 1D nanorods morphology. XRD revealed the formation of Mn3O4 spinel phase and TEM showed that ultrasmall-sized metallic Ag-nanoparticles deposited on Mn3O4 spinel (nanorods). This Ag/Mn3O4 nanomaterial exhibited excellent catalytic activity in the cyclohexane oxidation reaction at room temperature. The impacts of various reaction parameters (e.g. time, substrate : H2O2 molar ratio etc.) were investigated in detail. A detailed characterization study demonstrated the correlation between the physicochemical properties of the Ag–Mn oxide nanorods and their catalytic performance. A cyclohexane conversion of 88% with 75% cyclohexanone selectivity with an overall C6 selectivity (cyclohexanol + cyclohexanone) of 100% was accomplished at room temperature. The Ag/Mn3O4 catalyst hardly exhibited leaching up to eight reuses, proving its true heterogeneous nature. [ABSTRACT FROM AUTHOR]

A precipitation-deposition method in an organic medium was used to prepare vanadium phosphorus oxide (VPO) catalysts supported on SBA-15 and TUD-1. Oxidation of cyclohexane has been examined over mesoporous silica supported VPO catalyst. The supported VPO catalyst has been characterized by XRD, N 2 physisorption, SEM, HRTEM, H 2 -TPR and NH 3 -TPD techniques. The characteristic X-ray diffraction patterns of bulk VPO catalyst and VPO catalysts supported on mesoporous SBA-15 and TUD-1 showed that each of them are having well-crystallized vanadyl pyrophosphate [(VO) 2 P 2 O 7 ] phase. The vanadium redox centers were easily accessible for supported VPO catalyst. The TUD-1 supported VPO catalyst had higher acidity as found in NH 3 -TPD studies. The conversion of cyclohexane increased in the case of VPO dispersed on TUD-1 mesoporous material. From SEM and HRTEM results it is found that the nature of the support and VPO loading had a profound influence on the crystallinity, morphology and chemical property of the dispersed VPO phase. The changes in all the property had a prominent role on its catalytic activity for the oxidation of the cyclohexane. [ABSTRACT FROM AUTHOR]

Covalently anchored transition-metal salicylaldimine complexes on α-titanium phosphate {α-TiP.M(salicylaldimine) where M = Co, Cr, Cu and Fe} were synthesized by in situ method and characterized by BET surface area, XRD, SEM, EDX, FTIR, TGA and ICP techniques. Its catalytic activity was tested for the oxidation of cyclohexane under solvent free condition using tert-butyl hydroperoxide as an oxidant. The oxidation of cyclohexane gave cyclohexanol, cyclohexanone and some unidentified products. The activity of heterogeneous catalysts in the oxidation reaction decreased in the order of α-TiP.Co(salicylaldimine) > α-TiP.Cr(salicylaldimine) > α-TiP.Cu(salicylaldimine) > α-TiP.Fe(salicylaldimine). The α-TiP.Co(salicylaldimine) gave maximum conversion 14.85 % of cyclohexane with 92.13 % selectivity of KA-oil (cyclohexanol + cyclohexanone) in 6 h. The catalyst, α-TiP.Co(salicylaldimine) was reused for five cycles without significant loss of catalytic activity. Graphical Abstract: A heterogeneous catalytic system, α-TiP.Co(salicylaldimine)/TBHP gave maximum 14.85 % conversion and 92.13 % selectivity for KA-oil in oxidation of cyclohexane. The catalyst can be reused for five cycles.[Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]