Catalysts For Oxidation Of Cyclohexane Research Articles

MgAl and ZnAl layered double hydroxides modified with molybdate and tungstate anions as catalysts for oxidation of cyclohexane

Catalytic oxidation of cyclohexane to cyclohexanol and cyclohexanone with H2O2 was performed at a mild temperature of 40 °C and atmospheric pressure, using ZnAl (ZA) or MgAl (MA) layered double hydroxides (LDHs) modified with tungstate and molybdate anions as catalysts in heterogeneous medium. The catalysts were prepared by direct anion exchange reactions of tungstate and molybdate on LDHs intercalated with chloride/carbonate anions. All the solids showed catalytic activity in the cyclohexane oxidation, with slight selectivity for the ketone product. The catalytic efficiency was sensitive to the M2+ present in the composition of the LDH as well as to the anions. ZnAl-modified with WO42- was more active and more selective for ketone than the MgAl-modified WO42- or any molybdate-based LDH catalysts.

Fe3O4@MOF hybrid for supercilious recovery of Au(III) and Pd(II) from e-waste and spent as catalysts for cyclohexane oxidation

Improving the economic viability of the most successful precious metal catalysts is one of the significant challenges in renewable energy production. We designed a magnetic hybrid material based on Cu-pPDA MOF and Fe3O4 nanosphere for selective recovery of Au(III) and Pd(II) from e-waste. Owing to its superior maximum adsorption capacities of 1450 and 1236 mg/g for Au (III) and Pd(II), respectively, at 45 °C with the pH of 3 and 1, the sorbed samples were converted into catalysts through an annealing process to obtain carbon supported FeAu and FePd nanoparticles catalysts (FeAu/C and FePd/C). Furthermore, these catalysts were applied for the oxidation of cyclohexane and resulted that FeAu/C catalyst exhibited higher conversion rate of cyclohexane (93.2%) than FePd/C catalyst (88.3%). Mechanistic investigations suggested that synergetic effect of Fe and Au on the supported carbon promoted better bond cleavage of the O–O bond in cyclohexyl hydroperoxide, a crucial intermediate species in the oxidation of cyclohexane. This study provides an alternate approach for the sustainable preparation of highly desired catalytic materials.

One-step production of adipic acid from cyclohexane over stable oxides (CeO2 & ZrO2) using O2: Enhanced oxidation activity in acidic medium

One-step production of adipic acid from cyclohexane using O2 is a long due process for replacing conventional two-step process involving nitric acid oxidation of KA-oil. This work presents one-step oxidation of cyclohexane into adipic acid using O2 over stable oxides including CeO2 (Redox) and ZrO2 (Non-Redox) in acid medium. The effect of acidic medium and nature of metal oxide catalysts in cyclohexane oxidation have been investigated. While no activity was observed in solvent-free condition, presence of a polar protic solvent promoted significant improvement in oxidation activity.

Spectroscopic and microscopic studies of Co, Ce, and Pd containing gamma-alumina as catalysts for cyclohexene oxidation

The oxidation of cyclohexene belongs to the most important reactions in organic chemistry and leads to the production of the precursors for surfactants, polymers, agrochemicals, and drugs. So far, however, due to a complex reaction mechanism, it was hard to find the catalyst of satisfactory properties.Attractive catalysts in this reaction could be sonochemically prepared Co, Ce, and Pd containing γ-Al2O3, which is the object of the undertaken research. What is more, this combination of metals in the oxide system has not been studied. The analysis of catalytic performance indicated that all studied catalysts were active in the catalytic oxidation of cyclohexene. For metal-containing alumina (Me=Co, Ce, Pd), the conversion of cyclohexene was 61–84%. The best catalyst was Co5Ce5/γ-Al2O3s, prepared via the sonochemically-assisted procedure.It was also shown that the application of ultrasonic irradiation during the preparation of samples enhanced metal distribution over alumina support, resulted in smaller crystallites of prepared materials, and caused higher surface area with simultaneous smaller both pore size and pore volume in comparison with counterparts prepared via the standard procedure. XRD, Ra, and DR..-UV–vis spectroscopies indicated the coexistence of Co as Co3O4 and CoAl2O4 spinel, however, Ce was found in the form of CeO2. The addition of Pd to Co/γ-Al2O3 did not influence the status of cobalt.

Graphene supported CoO nanoparticles as an advanced catalyst for aerobic oxidation of cyclohexane

Transition metals are commonly employed as catalysts for the oxidation of cyclohexane.

‘Oxygen-Consuming Complexes’–Catalytic Effects of Iron–Salen Complexes with Dioxygen

[(salen)FeIII]+MeCN complex is a useful catalyst for cyclohexene oxidation with dioxygen. As the main products, ketone and alcohol are formed. In acetonitrile, [(salen)FeII]MeCN is rapidly oxidized by dioxygen, forming iron(III) species. Voltammetric electroreduction of the [(salen)FeIII]+MeCN complex in the presence of dioxygen causes the increase in current observed, which indicates the existence of a catalytic effect. Further transformations of the oxygen-activated iron(III) salen complex generate an effective catalyst. Based on the catalytic and electrochemical results, as well as DFT calculations, possible forms of active species in c-C6H10 oxidation have been proposed.

Catalytic Oxidation of Cyclohexane on Small Silver Clusters Supported by Graphene Oxide

Metal clusters including those supported on graphene-based materials have attracted extensive research interest in the past decade allowing dissection of the interfaces, stability, electronic properties, and catalytic activities at an atomically precise scale. Here, we have synthesized glutathione-protected Ag6 clusters via a facile green reaction route, transferred onto graphene oxide (GO) and exploit as catalyst for cyclohexane oxidation under ambient conditions. High selectivity and high yields to produce cyclohexanone are attained with tert-butyl hydroperoxide (TBHP) as the oxidant in the oxygen-flowing atmosphere. Based on density functional theory calculations, it is demonstrated that both TBHP and oxygen interact with the GO-supported Ag6 clusters, giving rise to the peroxide structure and hence facilitating the catalytic oxidation of cyclohexane. It is interestingly found that the hydrogen-added hydroperoxyl (−OOH) brings forth largely decreased activation barrier for the O–O bond dissociation. Th...

The metal complexes of new Schiff bases containing phosphonate groups and catalytic properties for alkane oxidation

In this study, two new salicylidene phosphonate ligands (HL1 and HL2) and their metal complexes (Cu2+, VO2+ and La3+) were synthesized and characterized by spectroscopic and analytical methods. The molecular structure of the ligand HL1 was determined by single‐crystal X‐ray diffraction study. In the structure of the ligand, there is an intramolecular phenol‐imine hydrogen bond. The synthesized compounds exhibit only one emission maximum upon excitation at 270–295 nm range. Complexation of the Schiff base ligands with metal ions did not cause a considerable quenching effect. Finally, the complexes prepared were used as catalysts in cyclohexane oxidation under microwave irradiation. The complexes showed high conversion rates (> 90%) for cyclohexane oxidation; however, poor selectivity was observed for all complexes. The La3+ complexes showed better selectivity for cyclohexane → cyclohexanol transformation with about 45% selectivity.

HKUST-1 Supported on Zirconium Phosphate as an Efficient Catalyst for Solvent Free Oxidation of Cyclohexene: DFT Study

Layer by layer metal-organic framework (MOF) supported on zirconium phosphate (ZrP) was synthesized at very mild conditions and used for the liquid phase oxidation of cyclohexene in solvent free condition in the presence of molecular oxygen. The MOF-ZrP was characterized by X-ray diffractometer (XRD), scanning electron microscope (SEM), thermal gravimetric analyzer (TGA), Fourier-transform infrared spectrometer (FT-IR) and Brunauer-Emmett-Teller (BET) surface area analyzer. The characterization shows a smooth morphology of MOF-ZrP with good stability under 200 °C having surface area 285 m2/g. The catalytic activity of the MOF-ZrP revealed that increase of layers of MOF on ZrP enhances conversion, as well as selectivity of oxidation of cyclohexene. DFT studies were used to explore the structure and electron properties of HKUST-1 (Hong Kong University of Science and Technology), which is a clue for the catalytic behavior of the catalyst.

Copper(II) complexes with an arylhydrazone of methyl 2-cyanoacetate as effective catalysts in the microwave-assisted oxidation of cyclohexane

Abstract 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)(H2O)] (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 L2− 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 L2−, water and imidazole ligands lead to a 3D supramolecular network. 1 and known Cu(II) complexes [Cu(H2O)2L]·H2O (2), [Cu(H2O)(py)L]·H2O (3) and [Cu3(µ3-OH)(NO3)(CH3OH)(µ2-X)3(µ2-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 × 103 and a turnover frequency of 1.98 × 103 h−1, after 2 h, at 50 °C.

Effective removal of Cr(VI) from aqueous solution by diamino-functionalised mesoporous MCM-48 and selective oxidation of cyclohexene and ethylbenzene over the Cr containing spent adsorbent

Adsorptive removal of Cr(VI) by N-3-trimethoxysilylpropylethylenediamine (AEAPTMS) functionalised MCM-48 prepared via grafting method was investigated with respect to contact time, adsorbent dose, initial metal ion concentration, pH, amine loading and temperature. The synthesized samples were characterized by X-ray diffraction (XRD), fourier transform infrared (FTIR) spectrocopy, scanning electron microscopy (SEM), N2 adsorption-desorption isotherm and thermogravimetric analysis (TGA). 1.5mmol AEAPTMS functionalised MCM-48 sample showed highest adsorption among the modified samples under similar conditions. Adsorption kinetics was successfully fitted by pseudo second-order kinetic model. The experimental data fitted well to the Langmuir adsorption isotherm model with a calculated maximum adsorption capacity of 166.67mg/g. The overall adsorption was a spontaneous and endothermic process as signified by the thermodynamic parameters. Another aspect of the work was the high catalytic efficiency of chromium containing spent adsorbent obtained by adsorption of Cr(VI) from the aqueous solution. The catalytic activity of the obtained catalyst was found to depend on the amount of adsorbed chromium. The spent adsorbents behaved as efficient catalysts for oxidation of cyclohexene (81.0% conversion) and ethylbenzene (94.6% conversion) with 96.7% and 100% selectivity towards desired product when 70% tert-Butyl hydroperoxide (TBHP) was used as oxidant.

Ni-Amino Acid–CaAl-Layered Double Hydroxide Composites: Construction, Characterization and Catalytic Properties in Oxidative Transformations

Host–guest composite materials were prepared applying the anionic forms of Ni(II)-amino acid (l-histidine, l-cysteine, and l-tyrosine) as the guests and CaAl-layered double hydroxide (CaAl-LDH) as the host. The syntheses were performed either by introducing the amino acid anions first and then constructing the metal ion–amino acid complexes or intercalating the pre-prepared complexes in anionic forms. The pristine as well as the composite LDH samples were structurally characterized by X-ray diffractometry, mid IR spectroscopy and scanning electron microscopy. The structural features of the interlayer complexes were studied by UV–Vis, inductively coupled plasma optical emission, mid and far IR and X-ray absorption spectroscopies as well as energy-dispersed X-ray analysis. On the basis of the acquired data, structural models were constructed. The composites were applied as catalysts in the liquid-phase oxidation of cyclohexene applying peracetic acid and the in situ formed iodosyl benzene as oxidants. Using peracetic acid afforded epoxide, while applying iodosyl benzene provided cis diol as the major or exclusive oxidation product. The catalysts displayed good recycling properties.

Aerobic oxidation of cyclohexane catalyzed by graphene oxide: Effects of surface structure and functionalization

Despite extensive development efforts on new catalysts for cyclohexane oxidation, current commercial processes are still desirable to further decrease the economic and environmental costs in the oxidation procedures. In this study, the catalyst properties of metal-free functionalized graphene oxide (GO) in the selective oxidation of cyclohexane is investigated to understand the effects of structure, functional groups and oxygen-containing groups. Both GO sheets and nano graphene oxide (NGO) sheets possess high cyclohexane conversions of 16.7% and 17.7% comparable to that of metal catalysts in the aerobic oxidation of cyclohexane. The higher catalytic activity of NGO sheets is caused by the smaller size and the higher content of −COOH. Within the oxygen-containing groups, the carboxylic acid groups on the surfaces of GO are supposed as the active site for the generation of O2− radical, which is the active oxygen species in this catalytic oxidation process.

CuO/Graphene Oxide Nanocomposite as Highly Active and Durable Catalyst for Selective Oxidation of Cyclohexane

AbstractAchieving breakage of C−H bond of hydrocarbons performance still remains a significant challenge in oxidation chemistry for heterogeneous catalyst. In this work, we report copper oxide‐ graphene oxide (CuO‐GO) nanocomposites as durable and highly active and selective catalyst for oxidation of cyclohexane. Different wt% of Cu(II) loaded on RGO surface to form a nanocomposite as well as Co(II) and Ni(II) loaded GO composites were prepared by wet impregnation method. The efficacy of catalyst was tested towards selective oxidation of cyclohexane. 5wt%CuO‐GO proved to be superior in terms improved selectivity towards cyclohexanone (82 %) and short reaction times, plus easy recovery and reusability of the catalyst. The presence of functional groups prevent the aggregation of catalytically active CuO species during the reaction progress.

Cu(II), Co(II) and Ni(II) Complexes Installed on Functionalized Silica Surface for Hydrogen Peroxide Assisted Cyclohexane Oxidation

In this work, Cu(II), Co(II) and Ni(II) complexes of the Schiff base ((S,E)-2-(3,4-dimethoxybenzylideneamino)-3-(1H-imidazol-4-yl)propionic acid) were synthesized and subsequently anchored onto amine functionalized silica. They were characterized by FT-IR, UV–vis., 29Si NMR, TG-DTG, ESR, FE-SEM and AFM techniques, and employed as catalysts in cyclohexane oxidation using hydrogen peroxide oxidant. Silica supported Cu(II) catalyst was shown the highest catalytic activity (70%) than rest of the catalysts used. On the other hand, all the complexes were selective as they yield only cyclohexanol and cyclohexanone. Silica supported catalysts were maintained their catalytic activity over five successive catalytic run. As these catalysts are selective, reusable and functioning well with hydrogen peroxide, they could design the environment friendly catalytic system for effective cyclohexane oxidation.

Mn porphyrins immobilized on non-modified and chloropropyl-functionalized mesoporous silica SBA-15 as catalysts for cyclohexane oxidation

In this work, solid catalysts were prepared by the heterogenization of Mn porphyrins (MnP) on mesoporous silica SBA-15 by two simple strategies: (1) immobilization of the three cationic isomers of Mn(III) N-methylpyridiniumporphyrins (MnTM-X-PyPCl5, X=2, 3,4) on mesoporous silica SBA-15 by electrostatic interaction; and (2) anchoring of the three neutral isomers of Mn(III) N-pyridylporphyrins (MnT-X-PyPCl, X=2, 3, 4) on chloropropyl-functionalized mesoporous silica SBA-15Cl via covalent bonding. SBA-15 and SBA-15Cl solids were characterized by FTIR, TGA-DTA, elemental analysis, SAXS, textural analysis, SEM, TEM, and 13C CPMAS NMR (for SBA-15Cl only). The resulting MnP-supported materials with MnP loadings of 0.3% w/w were characterized by diffuse reflectance UV/VIS spectroscopy and explored as catalysts for hydroxylation of cyclohexane using iodosylbenzene as oxygen donor. Changes on SBA-15Cl silanol and CCl bands on FTIR spectra, and UV/VIS analyses confirm the porphyrin immobilization. The heterogenized catalysts were more efficient and selective toward alcohol than the corresponding homogeneous systems. The covalently immobilized catalysts SBA-15Cl/MnT-X-PyPCl (X=2, 3, 4) showed total oxidation yields and selectivities slightly higher than those of SBA-15/MnTM-X-PyPCl5. In both solid systems, the efficiency and selectivity remained essentially unaffected by the immobilized MnP isomer. The strong interaction between MnP and the mesoporous silica, in both SBA-15 and SBA-15Cl systems, was verified by the low-leaching of MnP from the materials even after exhaustive washings. The solid catalysts were recovered and reused in recycling studies showing high resistance against oxidative destruction with no significant changes in catalytic efficiency upon recycling.

A Manganese-Based Coordination Polymer; Synthesis, Structure and Catalytic Activity

Atwo-dimensional manganese(II)-based coordination polymer [Mn(L)4(CH3COO)2] [L=1,4-bis(1-imidazolyl)benzene] has been synthesised. Its X-ray structure revealed that the layers of the 2D structure are stacked together by two types of weak interactions extending to form a three-dimensional supramolecular structure. The thermal stability of this coordination polymer is described and the compound has been used as a heterogeneous catalyst in oxidation of cyclohexene to cyclohexene oxide. A density functional study of structural parameters, position of the HOMO and LUMO energies, electrophilicity and global hardness is reported.

Oxidation Of Cyclohexane To Cyclohexanol And Cyclohexanone Using H4[α-SiW12O40]/Zr As Catalyst

Synthesis and preparation of polyoxometalate H4[α-SiW12O40].nH2O with Zr as support at various weights of Zr 0.01g; 0.05 g; 0.25 g; 0.5 g; 0.75 g; 1 g and 1.25 g to form H4[α- SiW12O40]/Zr was conducted. The compounds from preparation were characterized using FTIR spectroscopy and crystallinity analysis using X-Ray diffraction. Thus H4[α- SiW12O40]/Zr was applied as catalyst for oxidation of cyclohexane to cyclohexanol and cyclohexanone. Oxidation process was studied through reaction time, hydrogen peroxide amount, temperature, and weight of catalyst. FTIR spectrum of H4[α-SiW12O40]/Zr was appeared at wavenumber 771.53-979.84 cm-1 and Zr at 486.06-1481.33 cm-1. Diffraction pattern of H4[α-SiW12O40]/Zr showed that high crystallinity was identified at 2θ 8o-10o and 28.3o. Based on FTIR spectrum and XRD powder pattern, the optimum preparation of H4[α-SiW12O40]/Zr was obtained using 0.5 g of Zr. The catalytic study of cyclohexane using H4[α-SiW12O40]/Zr at 0.5 g of Zr resulted conversion about 99.73%. Catalyst can convert cyclohexane with the highest conversion then used for further deep catalytic investigation. Optimization of oxidation process resulted optimum reaction time at 2 h, 3 mL of hydrogen peroxide amount, 80 oC of temperature, and 0.038 g of catalyst. The GCMS analysis indicated the oxidation of cyclohexane using H4[α-SiW12O40]/Zr at 0.5 g of Zr formed cyclohexanol and cyclohexanone with selectivity 18.77 and 23.57, respectively.

Interesting Green Catalysis of Cyclohexane Oxidation over Metal Tetrakis(4-carboxyphenyl)porphyrins Promoted by Zinc Sulfide

To mimic the activity regulated by a cysteinate axial ligand in cytochrome P450 enzymes, metal tetrakis(4-carboxyphenyl)porphyrins (M TCPP) were immobilized on ZnS. They were characterized by a variety of spectroscopic techniques and were used as a catalyst for cyclohexane oxidation. The small amount of metal (Co, Fe, or Mn) TCPP (1.1 μmol) in the immobilized catalyst could be reused three times for oxidation, providing more than 6.5 × 105 turnover number and 20% molar yield of cyclohexanone and cyclohexanol (KA oil) on average. The coordination of ZnS played a key role. These catalysts were applied to green catalytic oxidation of cyclohexane to produce KA oil products.

Silver supported on hierarchically porous SiO2 and Co3O4 monoliths: Efficient heterogeneous catalyst for oxidation of cyclohexene

This study describes silver (Ag) nanoparticles supported on hierarchically porous SiO2 and Co3O4 monoliths and the use of these materials as heterogeneous catalysts for the oxidation of cyclohexene. Structural characterization of these materials was carried out by various techniques including scanning electron microscopy (SEM), N2 adsorption, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Characterization results revealed that Ag nanoparticles were incorporated into hierarchically porous SiO2 and Co3O4 without significantly affecting the structures of the supports. The oxidation of cyclohexene was investigated for hierarchically porous Ag/SiO2 and Ag/Co3O4 monoliths and powdered forms of the catalysts using H2O2 as oxidant. Detailed parameters including the effect of temperature, oxidant, catalyst loading, and substrate to oxidant ratio were thoroughly studied. The catalyst was found to be stable and could be reused several times without affecting its catalytic activity under the optimized reaction conditions.