Catalysts For Oxidation Of Cyclohexane Research Articles

Heterogeneous Green Catalyst for Oxidation of Cyclohexene and Cyclooctene with Hydrogen Peroxide in the Presence of Host (Nanocavity of Y‐zeolite)/Guest (N4‐Cu(II) Schiff Base Complex) Nanocomposite Material

AbstractCopper(II) complex of a Schiff base ligand derived from pyrrolcarbaldehyde and o‐phenylenediamine (H2L) has been synthesized and encapsulated in Y‐zeolite matrix. The hybrid material has been characterized by elemental analysis, IR and UV‐Vis spectroscopic studies as well as X‐ray diffraction (XRD) pattern. The encapsulated copper(II) catalyst is an active catalyst for the oxidation of cyclooctene and cyclohexene using H2O2 as oxidant. Under the optimized reaction conditions 81% conversion of cyclohexene with 65% selectivity for 2‐cyclohexenone formation and 87% conversion of cyclooctene with 46% selectivity for epoxide formation were obtained.

Immobilization of metalloporphyrin on organosilicon microsphere mixed with ceria as a new catalyst for oxidation of cyclohexane

In this study, cobalt tetraphenylporphyrin was immobilized through amide bond on organosilicon microsphere mixed with ceria. The catalysts were characterized and the catalytic performance was investigated. The results show that the catalysts are nanoparticles with average sizes of 30 nm and organosilicon microsphere is mixed with ceria. In addition, the catalysts exhibit excellent catalytic performance for selective oxidation of cyclohexane by molecular oxygen without solvent in a sealed autoclave reactor, due to the cooperative effect among the metalloporphyrin, organosilicon microsphere and ceria. The conversion of cyclohexane and the selectivity of cyclohexanol + cyclohexanone reached 14.21% and 54.6%, respectively. After repeated reuse, the conversion of cyclohexane and the selectivity of cyclohexanol + cyclohexanone were still kept at about 13.1% and 61.9%, respectively.

Homogenous and Heterogeneous Catalytic Activity of Azo-Linked Schiff Base Complexes of Mn(II), Cu(II) and Co(II)

Azo linked Schiff-base[L] complexes of Mn(II)(1), Cu(II)(2) and Co(II)(3) obtained by template method, in the reaction of 4-(benzeneazo) salicylaldehyde with 1,2-propanediamine in the present of metal acetate, respectively. Complexes are used as catalyst for oxidation of cyclohexene with tert-butylhydroperoxide (TBHP); oxidation of cyclohexene catalyzed by these complexes gave 2-cyclohexene-1-one and 2-cyclohexene-1-ol as major products. Conversion of cyclohexene achieved was 95–100% with (1), (2) and (3), with selectivity of 57, 92 and 100% for 2-cyclohexene-1-one, respectively. The encapsulated Cu(II) complex (Cu–NaY) catalyzes the oxidation of cyclohexene using TBHP as oxidant in good yield. (Cu–NaY) under optimized reaction condition gave three reaction products. A maximum of 100% conversion of cyclohexene has been achieved where selectivity of 2-cyclohexene-1-one was 83%.

Copper(II) complex of monobasic tridentate ONN donor ligand: synthesis, encapsulation in zeolite-Y, characterization, and catalytic activity

Reaction between CuCl2 and (Z)-2-(1-(2-(1H-benzo[d]imidazol-2-yl)ethylimino)ethyl)phenol (Hhap-aebmz) derived from o-hydroxyacetophenone (Hhap) and 2-aminoethylbenzimidazole (aebmz) gives [CuII(hap-aebmz)Cl]. Elemental analysis, magnetic susceptibility, spectral (IR and electronic) data, and single crystal X-ray studies confirm the distorted square planar structure of the complex. [CuII(hap-aebmz)Cl] has been encapsulated in the nano-cavity of zeolite-Y and its encapsulation is ensured by various physico-chemical techniques. The encapsulated complex has been used as a catalyst for oxidation of cyclohexene and phenol in the presence of H2O2. With nearly quantitative oxidation of cyclohexene, the selectivity of the oxidation products follows the order, 2-cyclohexene-1-ol (44%) > 2-cyclohexene-1-one (40%) > cyclohexeneoxide (12%) > cyclohexane-1,2-diol (4%). Oxidation of phenol (65.7%) gives catechol (66.1%) > hydroquinone (32.9%).

Immobilization of Metalloporphyrin on Functionalized Magnetic Nanoparticles as a Catalyst in Oxidation of Cyclohexene: Novel Modified Fe3O4 Nanoparticles with Triethoxysilane Agent

Magnetic nanoparticles, Fe3O4, have been prepared and functionalized by (N-(3-(triethoxysilyl)propyl)isonicotinamide) and characterized by infrared spectroscopy, thermal analysis (TGA/DTA), X-ray powder diffraction, scanning electron microscopy, elemental analysis and BET surface area measurement. The functionalized Fe3O4 nanoparticles were used as a support to anchor metalloporphyrin. Application of immobilized metalloporphyrin as a heterogeneous catalyst in the oxidation of cyclohexene was explored. Effect of various parameters such as solvent and temperature on immobilization process and also various parameters (solvent, time, oxidant and axial group effect) on oxidation of cyclohexene has been investigated. The result showed that the immobilized metalloporphyrin on functionalized magnetic nanoparticles is an efficient and reusable catalyst for oxidation of cyclohexene.

MCM-41 Anchored Manganese Salen Complex as Catalysts for Cyclohexene Oxidation

Novel catalysts with higher metal content were synthesized through the addition of a diamine. The catalysts showed excellent performances in the oxidation of cyclohexene and the higher metal content decreases the amount of the catalyst to be used, which are promising in industrial application.

Synthesis and application of new Schiff base Mn(III) complexes containing crown ether rings as catalysts for oxidation of cyclohexene and cyclooctene by Oxone

Six catalysts MnClL1–MnClL6, containing two crown ether rings, were synthesised and characterised by IR spectroscopy and CHN microanalysis. A combination of Oxone, as oxidant, and these catalysts was used for the oxidation of cyclohexene and cyclooctene. Among the prepared catalysts, MnClL3 and MnClL4 exhibited the best catalytic efficiency. Catalysts MnClL1, MnClL2 and MnClL6 showed a moderate efficiency and MnClL1 showed the lowest efficiency. Comparison of MmclL1–MnClL4 and MnClL6 containing crown ether rings with an identical mixture of uncrowned complex MnClL7 [manganese N,N′-bis(salicylidene)ethylenediamine chloride] and crown ether 2 (4′-hydroxybenzo-15-crown-5), revealed a more important role for the crown ether than increasing solubility of Oxone in the organic phase. The effect on reaction times and chemical yields of temperature, pyridine as the axial base, and different alkali metal salts was also investigated.

Self-assembly preparation of Au/SiO2 catalyst and its catalysis for cyclohexane oxidation with air

Au/SiO2 catalysts were prepared by self-assembly technique and characterized by EDS, XRD, XPS, AAS and N2 adsorption/desorption. They were found to be very efficient catalysts for the selective oxidation of cyclohexane with air in the absence of any solvent or promoter. The influences of Au loading, reaction temperature, reaction pressure and reaction time on the catalytic activity were explored in detail. Under suitable reaction conditions, the conversion of cyclohexane and total selectivity of cyclohexanone and cyclohexanol were up to ~10 and ~92%, respectively.

ChemInform Abstract: Oxidation of Alkanes by Cobalt(II) Salts of Weakly Coordinating Anions.

Catalysts which effect the selective oxidation of alkanes under mild reaction conditions are highly desired. Commercial processes exist which involve the oxidation of alkanes by O{sub 2} with cobalt carboxylate catalysts. Elevated temperatures and pressures are required, and the metal ion function is to decompose hydroperoxides formed in a radical-chain process. The authors have demonstrated that a weakly solvated cobalt-acetonitrile complex (Co(NCCH{sub 3}){sub 4})(PF{sub 6}){sub 2}, with a weakly coordinating anion catalyzes the air oxidation of alkanes under mild conditions (75C and 3 atm). Cyclohexane and adamantane are converted to the corresponding alcohol and ketone products. The commercial catalyst for cyclohexane oxidation does not function under these milder conditions. Experiments indicate a mechanism in which the metal ion functions both as an initiator and as a hydroperoxide decomposition catalyst.

Synthesis and characterization of a Fe(III)-Schiff base complex in a Zn-Al LDH host for cyclohexane oxidation

The paper reports the synthesis, characterization and catalytic evaluation of a Fe(III)-Schiff base complex intercalated Zn-Al layer double hydroxide (LDH). The immobilized complex was characterized by powder X-ray diffraction, FT-IR, UV–vis spectroscopy, N 2 adsorption desorption, scanning electron microscopy and TGA techniques. The immobilization complex was found to be an effective catalyst for oxidation of cyclohexane using H 2O 2 as an oxidant under mild conditions. A conversion of 45.5% of cyclohexane was obtained with selectivity of 100% of the cyclohexanone/cyclohexanol at 70 °C in 8 h in acetonitrile solvent. Recycling test of the catalyst showed that it was recovered and reused up to 3 more cycles without loss of performance.

Tetranuclear copper(ii)–Schiff-base complexes as active catalysts for oxidation of cyclohexane and toluene

Three new Cu(ii) complexes, [Cu(4)(O)(L(n))(2)(CH(3)COO)(4)] where HL(1) = 4-methyl-2,6-bis(2-fluoroethyliminomethyl) phenol for complex , HL(2) = 4-methyl-2,6-bis(2-chloroethyliminomethyl) phenol for complex .0.25CH(3)CN and HL(3) = 4-methyl-2,6-bis(2-bromoethyliminomethyl) phenol for complex have been synthesized and characterized by elemental analysis, FTIR, UV-vis spectroscopy, and electrospray ionization mass spectroscopy. The structure of complex .0.25CH(3)CN has also been confirmed by single crystal X-ray diffraction analysis. These complexes have been found to be active catalysts for the oxidation of cyclohexane and toluene in the presence of hydrogen peroxide as the oxidant under mild conditions. Cyclohexane is oxidized to yield cyclohexanol and cyclohexanone, whereas toluene is oxidized to benzyl alcohol and benzaldehyde.

Metalloporphyrins encapsulated mesoporous molecular sieves as efficient heterogeneous catalysts for oxidation of cyclohexene with iodosylbenzene

The cationic Fe, Mn or VO porphyrins were encapsulated in Si, Al, Ti and V-MCM-41. The catalytic activity was investigated for the oxidation of cyclohexene with iodosylbenzene (PhIO) as oxidant. Manganese porphyrin supported catalysts produces epoxide as major products whereas iron and vanadyl porphyrins gave allylic oxidation products as major constituents. The results obtained clearly shows that the selectivity of various products depends not only on the nature of the support materials but also on the combined effects of metalloporphyrins and the supports. The recyclability of the heterogeneous catalysts was also investigated. The decrease in catalytic activity and leaching of active centers were observed when porphyrins were supported on Si-MCM-41.

Exfoliated VOPO 4·2H 2O dispersed on alumina as a novel catalyst for the selective oxidation of cyclohexane

The VOPO 4·2H 2O phase has been exfoliated in 2-propanol and the exfoliated solution dispersed on alumina in the ratio 1:1 (VPO-ED). A sample of exfoliated VOPO 4·2H 2O was also obtained by recovering the solid from the exfoliated solution of VOPO 4·2H 2O (VPO-E). Both these samples were characterized by XRD, FTIR, TGA/DTA, and SEM studies and it was shown that VPO-ED and VPO-E have the original VOPO 4·2H 2O structure although the morphology, crystallinity and crystal size and surface areas of the samples are affected both on exfoliation and subsequent dispersion on alumina. These phases have been shown to be active catalysts for the oxidation of cyclohexane preferentially to cyclohexanol. The conversion of cyclohexane increased markedly in the case of the sample dispersed on alumina. Thus, using VPO-ED as the catalyst, a cyclohexanol/cyclohexanone ratio of 71 can be obtained even at a high cyclohexane conversion of 83.3%. The present work therefore not only represents a novel approach for preparing dispersed VPO phases but also demonstrates the efficiency of the VOPO 4·2H 2O phase in catalyzing the oxidation of cyclohexane selectively to cyclohexanol.

Immobilization of manganese tetraphenylporphyrin on Au/SiO2 as new catalyst for cyclohexane oxidation with air

Abstract Manganese tetraphenylporphyrin was successfully immobilized on Au/SiO 2 , by using mercaptopyridine with sulfhydryl and pyridyl groups as bridging agent. The synthesized catalyst with novel structure was characterized by FTIR spectroscopic technique, XPS measurement, TG–DTA analysis and so on. During aerobic oxidation of cyclohexane in the presence of this material, the conversion of cyclohexane and total selectivity to cyclohexanone and cyclohexanol were up to 5.39% and 88.74%, respectively.

Silica immobilized salicylaldimine Cu(II) and Co(II) complexes as catalysts in cyclohexene oxidation: A comparative study of support effects

Unsubstituted and tertiary-butyl substituted salicylaldimine complexes of Cu(II) and Co(II) immobilized on silica supports (MCM-41, SBA-15 and Davisil 710) were tested as catalysts for cyclohexene oxidation using hydrogen peroxide as an oxidant under an oxygen atmosphere. The effect of the nature of the salicylaldimine ligand and the type of support were investigated. Allylic species were isolated as the major products with cyclohexene–epoxide produced as a by-product in only some instances. Product selectivity was found to be greatly influenced by the nature of the support material.

Silica-metalloporphyrins hybrid materials: preparation and catalysis to hydroxylate cyclohexane with molecular oxygen

Three types of novel silica-metalloporphyrins hybrid materials, Si-S-APTCPPFe, Si-S-APTCPPMn and Si-S-APTCPPCo, were prepared at room temperature by sol–gel method involving a thiol-ene polymerization reaction of 5-(4-allyloxy)phenyl-10,15,20-tri(4-chlorophenyl)porphyrin (APTCPP) with 3-mercaptopropyltrimethoxysilane (MPS). The hybrid materials were characterized by XRD, SEM, FT–IR, UV–Vis and TG, and were investigated as catalysts for the aerobic oxidation of cyclohexane. It is found that these hybrid materials are more efficient catalysts than the analogous non-supported metalloporphyrins for cyclohexane hydroxylation in metalloporphyrin–O2–ascrobate system and the metal ion in the porphyrins significantly affected the catalytic efficiencies of these hybrid materials.

Synthesis of heterogeneous copper complex catalyst for oxidation of cyclohexane using molecular oxygen

AbstractBinuclear macrocyclic copper complex was synthesized and bonded ionically to the montmorillonite clay to enhance thermal stability upto 600°C. The oxidation of cyclohexane using molecular oxygen in the absence of initiators, promoters and coreactants has been studied in the temperature range 145–190°C. The overall cyclohexane conversion was 21% at 180°C and cyclohexanone, the major product with 71% selectivity. The experimental data were analyzed against kinetic scheme proposed and the rate constants determined using Genetic Algorithm.

Catalytic oxidation of cyclohexane over Cu-Zn-Cr ternary spinel systems

Spinel systems with the composition of Cu1−xZnxCr2O4 [x = 0 CCr, x = 0.25 CZCr-1, x = 0.5 CZCr-2, x = 0.75 CZCr-3 and x = 1 ZCr] were prepared by homogeneous co-precipitation method and were characterized by X-ray diffraction (XRD) and FT-IR spectroscopy. Elemental analysis was done by EDX, and surface area measurements by the BET method. The redox behavior of these catalysts in cyclohexane oxidation at 243 K using TBHP as oxidant was examined. Cyclohexanone was the major product over all catalysts with some cyclohexanol. 69.2% selectivity to cyclohexanol and cyclohexanone at 23% conversion of cyclohexane was realized over zinc chromite spinels in 10 h.

Preparation of MCM-41 Supported Salen Vanadium Complex and its Catalysis for the Oxidation of Cyclohexane with H2O2 as an Oxidant

A secondary amino group modified MCM-41 (mobile crystalline material number 41) was synthesized and used as a support for the immobilization of a salen oxovanadium complex via a multi-grafting method. The immobilized complex was characterized by UV–Vis spectroscopy, X-ray diffraction (XRD), N2 adsorption and ICP analysis techniques. The immobilized complex was found to be an effective catalyst for oxidation of cyclohexane using H2O2 as an oxidant under mild conditions. A conversion of 45.5% of cyclohexane was obtained with a selectivity of 100% of the cyclohexanone/cyclohexanol mixture when the reaction was run at 60 °C for 12 h in acetonitrile. Decomposition of the complex, which leads to the deactivation of the catalyst, is observed and a decomposition mechanism is discussed.

Oxidation of Cyclohexane with Molecular Oxygen Catalyzed by SiO2 Supported Palladium Catalysts

The di(ethylthio)ethane palladium (A) and di(ethylthio)propane palladium (B) complexes have been immobilized on the surface of silica gel and these catalyst systems are shown to serve as effective supported Pd catalysts for cyclohexane oxidation with O2 under solvent free condition. The supported catalyst A provides best results (overall ca. 16.2% conversion, with a selectivity of 72 or 24% for cyclohexanol or cyclohexanone, respectively, which are further promoted in the presence of 2-pyrazinecarboxylic acid which acts as a co-catalyst (overall ca. 21.2% conversion).