Activity In Oxidation Of Cyclohexene Research Articles

Expanded titanosilicate MWW-related materials synthesized from a boron-containing precursor as an efficient catalyst for cyclohexene oxidation

Titanosilicate forms of expanded MWW-related materials (Ti-MWW-exp) are synthesized starting from a lamellar boron-containing MWW precursor. The boron expulsion by the nitric acid treatment from the molecular sieve framework left behind the vacancies. By extending the acid treatment time, Si species around the defects is dissolved and is the likely source for the species required to expand the interlayer space. The obtained Ti-MWW-exp material exhibits a superior catalytic activity in cyclohexene oxidation, and a high selectivity for cyclohexene oxide is also achieved. Moreover, this convenient post synthesis was also used in the preparation of interlayer expanded B-MWW and B–Al-MWW materials, giving rise to the design of the other interlayer expanded metallosilicates. A facile strategy is put forward to construct the interlayer expanded MWW-type metallosilicates. The interlayer expanded Ti-MWW-exp zeolite can exhibit the excellent catalytic performance in the epoxidation of bulky cyclohexene. • An interlayer expanded MWW-type metallosilicate is post-synthesized. • Removal of boron can change the stability of the neighboring Si species. • Si species reinserted into the zeolite can serve as pillars in the interlayer space. • The interlayer expanded Ti-MWW-exp is an efficient catalyst for the cyclohexene oxidation. • This strategy is a promising way for designing other interlayer expanded boron-containing zeolites.

Spectroelectrochemical Properties and Catalytic Activity in Cyclohexane Oxidation of the Hybrid Zr/Hf-Phthalocyaninate-Capped Nickel(II) and Iron(II) tris-Pyridineoximates and Their Precursors.

The in situ spectroelectrochemical cyclic voltammetric studies of the antimony-monocapped nickel(II) and iron(II) tris-pyridineoximates with a labile triethylantimony cross-linking group and Zr(IV)/Hf(IV) phthalocyaninate complexes were performed in order to understand the nature of the redox events in the molecules of heterodinuclear zirconium(IV) and hafnium(IV) phthalocyaninate-capped derivatives. Electronic structures of their 1e-oxidized and 1e-electron-reduced forms were experimentally studied by electron paramagnetic resonance (EPR) spectroscopy and UV−vis−near-IR spectroelectrochemical experiments and supported by density functional theory (DFT) calculations. The investigated hybrid molecular systems that combine a transition metal (pseudo)clathrochelate and a Zr/Hf-phthalocyaninate moiety exhibit quite rich redox activity both in the cathodic and in the anodic region. These binuclear compounds and their precursors were tested as potential catalysts in oxidation reactions of cyclohexane and the results are discussed.

Copper‐Coordinated Histidyl Bolaamphiphile Assembly as an Oxidative Catalyst: Coordination Structure and Catalytic Activity in Cyclohexane Oxidation

AbstractSurface‐exposed imidazole moieties of a supramolecular self‐assembly of histidyl bolaamphiphile (HisC7) readily coordinate at transition metal ions. In this study, the Cu‐coordinated histidyl bolaamphiphile assembly (HisC7[Cu]) is demonstrated to be an effective oxidative catalyst, with a Fenton‐active copper center. HisC7[Cu] catalytically oxidized cyclohexane to produce cyclohexanol in the yield of 20.2 %, which is comparable to other homogeneous catalysts. The coordination sphere of the active copper center is investigated through various spectroscopic techniques in consideration of the catalytic activity. The highest catalytic activity is exhibited by the HisC7[Cu] catalyst prepared at a HisC7/Cu molar ratio of 0.75, where the copper center of HisC7[Cu] has a 1N3O coordination environment. The copper center with bidentate coordination to imidazole groups shows low activity due to the lack of open coordination sites. The HisC7[Cu] catalyst is applied to the oxidation of cyclohexane, and the reaction characteristics and reusability of HisC7[Cu] are studied.

Synthesis and Catalytic Application of Mesoporous Titanium Silicoaluminophosphate-37 (MESO-TSAPO-37) Molecular Sieves Assembled from Microporous TSAPO-37 Precursor

Titanium containing mesoporous silicoaluminophosphate (MESO-TSAPO-37) molecular sieves were assembled from microporous titanium silicoaluminophosphate-37 (TSAPO-37) precursor possessing structural building units of SAPO-37. FT-IR studies and N2 sorption analysis supported the presence of microporosity on the walls of the mesoporous surface. The composite MESO-TSAPO-37 material showed promising catalytic activity in oxidation of cyclohexene. The catalyst showed complete conversion (100 %) of olefin with selective formation of allylic products (80 %). The catalytic activity persisted for several runs. Titanium substituted MESO-TSAPO-37 materials was assembled in presence of surfactant from microporous precursors of TSAPO-37 by a two step procedure. Thoroughly characterized MESO-TSAPO-37 was used for allylic oxidation of cyclohexene which resulted in 100 % conversion and 80 % selectivity towards allylic product.

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

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

Heterogeneous Catalytic Oxidation of Cyclohexane with H2O2 Catalyzed by Cs- and TBA-salts of Cu- and Mn-Polyoxotungstates on MCM-41

Cs-and tetrabutyl ammonium (TBA) salts of Cu- and Mn-polyoxotungstates were synthesized. They were loaded on MCM-41 support (by impregnation method in 20-30 wt%) to increase surface area of the catalysts. The supported catalysts were characterized by inductive coupled plasma emission (ICP), Fourier-Transform Infrared Spectroscopy (FT-IR), X-ray diffraction (XRD) and nitrogen adsorption-desorption. Their catalytic activities for oxidation of cyclohexane were compared using green oxidant H2O2 under mild reaction conditions. The oxidized products are cyclohexanol and cyclohexanone. The activities follow the order: TBA-CuPOM/MCM > TBA-MnPOM/MCM > Cs-CuPOM/MCM > Cs-MnPOM/MCM. The Mn containing catalysts gave higher cyclohexanone selectivity than Cu containing catalysts. The Cs salt catalysts can be reused without loss of activity due to its insolubility in the reaction medium. The 30wt%Cs-CuPOM/MCM and 30wt% Cs-MnPOM/MCM gave comparable activity (16-17 % conversion with 75-76 %selectivity using H2O2/cyclohexane mole ratio = 4 at 80 ˚C in 12 h. The oxidation reaction appears to be radical process, since it was inhibited in the presence of radical scavenger.

Cyclohexane oxidation: Small organic molecules as catalysts

The catalytic activity of several small organic molecules including ketones, aldehydes, esters, alcohols and amines toward cyclohexane oxidation was investigated. The catalytic activity was found to be closely related to polarity, α-H activity, the strength of hydrogen bond formed with cyclohexane and the radical scavenging capability of these molecules. Based on the obtained results, the catalytic role of the organic solvent must be considered for cyclohexane oxidation. Tripropylamine has very high activity in cyclohexane oxidation and it might be further developed as a promising small-molecule organocatalyst for future application. N- or O-containing small organic molecules were used as catalysts for cyclohexane oxidation. The polarity, α-H activity, strength of the hydrogen bond formed with cyclohexane and the radical scavenging capability of these molecules determine their catalytic activity.

Catalytic oxidation of cyclohexane with dioxygen over boehmite supported trans-A2B2 type metalloporphyrins catalyst

Metalloporphyrin-catalysed direct functionalization of saturated CH bonds is one among the topical and challenging areas within the chemical industry. In this work, three types of unsupported and boehmite supported trans-A2B2-metalloporphyrin chloride complexes (Co-D(p-Cl)PPCl, Fe-D(p-Cl)PPCl, Mn-D(p-Cl)PPCl) were prepared and characterized. It has been found that these trans-A2B2-metalloporphyrins have high catalytic activity in cyclohexane oxidation under dioxygen. The boehmite supported metalloporphyrins show better catalytic performance and are more stable than unsupported metalloporphyrins. Among these supported metalloporphyrin catalysts, Co-D(p-Cl)PPCl/BM was better than Fe-D(p-Cl)PPCl/BM and Mn-D(p-Cl)PPCl/BM, the cyclohexane conversion and selectivity to KA oil are 6.83% and 83.30%, respectively, and the turnover number is 1.05×107. The Co-D(p-Cl)PPCl/BM catalyst can be facilely recovered and was recycled up to six times without significant decrease in catalytic performance.

New soluble peripherally tetra-substituted Co(II), Fe(II) phthalocyanines: Synthesis, spectroscopic characterization and their catalytic activity in cyclohexene oxidation

Abstract New 4-{2-[3-(diethylamino)phenoxy]ethoxy}phthalonitrile 3 was obtained from 2-[3-(diethylamino)phenoxy]ethanol 1 and 4-nitrophthalonitrile 2 with K2CO3 in DMF at 50 °C. The novel iron(II) and cobalt(II) phthalocyanine complexes 4 and 5 were prepared by the reaction of the phthalonitrile derivative 3 with n-pentanol in a standard Schlenk tube in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU). These new phthalocyanine complexes were characterized by the spectroscopic methods (IR, 1H NMR, 13C NMR, UV–vis and mass spectroscopies) Complexes 4 and 5 are employed as catalyst for the oxidation of cyclohexene using tert-butyl hydroperoxide (TBHP), m-chloroperoxybenzoic acid (m-CPBA), aerobic oxygen and hydrogen peroxide (H2O2) as oxidant. It is observed that iron(II) phthalocyanine complex can selectively oxidize cyclohexene to give 2-cyclohexene-1-ol as major product, and 2-cyclohexene-1-one and cyclohexene oxide are minor products. TBHP was found to be the best oxidant since the minimal destruction of the catalyst, higher selectivity and conversion were observed in the products.

Enhanced Catalytic Activity on Titanosilicate Molecular Sieves Controlled by Cation−π Interactions

A new class of heterogeneous catalytic systems utilizing cation-guest interactions was designed based on microporous titanosilicate molecular sieves. Introducing heavier alkali metal cations on ion-exchange sites of the framework resulted in a significant enhancement of the catalytic activity for oxidation of cyclohexene and styrene, whereas such an enhancement was not observed in oxidation of cyclohexane without π systems. Distinct relationships between the catalytic activities and intermolecular interaction energies which were determined by IR spectroscopic and computational approaches clearly evidenced the predominance of the cation-π interaction in this catalytic system.

The Effect of Disulphide Bond in Metallodeuteroporphyrin on Their Catalytic Activity for Aerobic Oxidation of Cyclohexane

Two novel types of metallo-deuteroporphyrins bearing the disulphide bond were employed to investigate their catalytic activity in oxidation of cyclohexane with molecular oxygen (air) to cyclohexanol and cyclohexanone without the use of sacrificial co-reductant. The catalytic activity of metallo-deuteroporphyrin disulphide derivatives was obvious difference when different metals were incorporated into the porphyrin. However, the same metal cobalt porphyrin complexes exhibited the different catalytic efficiency due to the effect of substituents. Co(II)deuteroporphyrin disulphide derivative is more active than other metallo-porphyrin complexes. On the basis of the obtained results the new reaction process is discussed.

“Solvent-free” synthesis of thermally stable and hierarchically porous aluminophosphates (SF-APOs) and heteroatom-substituted aluminophosphates (SF-MAPOs)

Hierarchically porous aluminophosphates (SF-APOs) and metal substituted aluminophosphates (SF-MAPOs, M = Co, Fe, Cr) have been synthesized via simple grinding and heating in the absence of solvent. Characterization results show that these mesoporous aluminophosphates have a hierarchically microporous/mesoporous structure. In addition, metal atoms can be efficiently incorporated into the walls of mesoporous aluminophosphates, and the SF-CoAPO sample shows high catalytic activity in cyclohexene oxidation compared with microporous samples. Special features of the “solvent-free” synthesis route, such as increasing product yield, saving energy, elimination of pollution, and convenience for incorporation of heterogeneous atoms, ensure its great potential in the synthesis of porous materials.

Organic-Inorganic Hybrid Saponites Obtained by Intercalation of Titano-Silsesquioxane

The synthesis and characterization of two bifunctional composite materials based on synthetic saponite clays is here presented. These materials were prepared by intercalation of a Ti-containing aminopropylisobutyl polyhedral oligomeric silsesquioxane (Ti-NH(2) POSS) in synthetic saponite samples containing interlayer sodium (Na-SAP) or protons (H-SAP). Hybrid organic-inorganic materials, Ti-NHM-1 and Ti-NHM-2, were obtained upon ion exchange. Structural, spectroscopic, and thermal properties of both hybrid materials were investigated in detail along with their catalytic activity in cyclohexene oxidation.

Use of a New Polymer Anchored Cu(II) Azo Complex Catalyst for the Efficient Liquid Phase Oxidation Reactions

A new polymer anchored copper(II) azo complex has been synthesized and characterized by using scanning electron microscope (SEM), thermogravimetric analysis (TGA), elemental analysis, atomic absorption spectroscopy (AAS) and spectrometric methods like diffuse reflectance spectra of solid (DRS) and Fourier transform infrared spectroscopy (FTIR). The immobilized Cu(II) catalyst shows excellent catalytic activity in oxidation of cyclohexene, styrene, benzyl alcohol and ethylbenzene in presence of tert-butylhydroperoxide (TBHP) as an oxidant. The effects of different solvents, oxidants, temperature, substrate oxidant ratio and amount of catalyst were also studied. The catalytic results reveal that the polymer-anchored Cu(II) azo complex catalyst can be recycled more than five times without appreciable loss in the catalytic activity.

Undecatungstophospho(aqua)ruthenate(II): One pot synthesis, characterization and non-solvent liquid phase aerobic oxidation of alkenes

Keggin type undecatungstophospho(aqua)ruthenate(II) was synthesized by the reaction of [PM 12O 40] 3− (aq) and RuCl 3 (aq) under mild conditions and characterized by various physicochemical techniques. The catalytic activity of the synthesized complex was evaluated for non-solvent liquid phase oxidation of styrene, cyclohexene and cis-cyclooctene using molecular oxygen. The synthesized complex acts as an efficient catalyst, especially for oxidation of cyclohexene. It shows very high activity for oxidation of cyclohexene in terms of conversion as well as selectivity. It gives 69% conversion with 100% selectivity for cyclohexane oxide.

Synthesis, characterization and catalytic oxidation of cyclohexane using a novel host (zeolite-Y)/guest (binuclear transition metal complexes) nanocomposite materials

Transition metal (M = Mn(II), Co(II), Ni(II) and Cu(II)) complexes with octahydro-Schiff base (H 4-N 4O 4) = 2,7,13,18-tetramethyl-3,6,14,17-tetraazatricyclo-[17.3.1.1]-tetracosa-1(23),2,6,8(24),9,11,13,17,19,21-decaene-9,11,20,22-tetraol; H 4([H] 8-N 4O 4) = 2,7,13,,18-tetramethyl-3,6,14,17-tetraazatricyclo-[17.13.1.1.]-tetracosa-1(23),8(24),9,11,19,21-hexane-9,11,20,22-tetraol) have been encapsulated in nanopores of zeolite-Y; [M([H] 8-N 4O 4)]@NaY; with Flexible Ligand Method (FLM) for the first time. The new Host-Guest Nanocomposite Materials (HGNM) was characterized by several techniques: chemical analysis, spectroscopic methods (DRS, FT-IR and UV/Vis), BET technique, conductometric and magnetic measurements. The catalytic activities for oxidation of cyclohexane with HGNM complexes are reported. Zeolite encapsulated octahydro-Schiff base copper(II) complex; [Cu([H] 8–N 4O 4)]@NaY; was found to be more active than the corresponding cobalt(II), manganese(II) and nickel(II) complexes for cyclohexane oxidation. The catalytic properties of the complexes are influenced by their geometry and by the steric environment of the active sites. HGNM are stable enough to be reused and are suitable to be utilized as partial oxidation catalysts. The encapsulated catalysts systems; [M([H] 8-N 4O 4)]@NaY; were more active than the corresponding neat complexes; [M([H] 8-N 4O 4))].

Flexible ligand synthesis, characterization and catalytic oxidation of cyclohexane with host (nanocavity of zeolite-Y)/guest (Mn(II), Co(II), Ni(II) and Cu(II) complexes of tetrahydro-salophen) nanocomposite materials

Transition metal (M = Mn(II), Co(II), Ni(II) and Cu(II)) complexes with tetrahydro-salophen (salophen = N, N-bis-(salycilidene)-1,2-phenylenediamine; H 2[H 4salophen] = 2-({2-[(2-hydroxybenzyl)amino]anilino}methyl)phenol) have been encapsulated in nanopores of zeolite-Y; [M(H 4salophen)]-NaY; with Flexible Ligand Method for the first time. The new Host–Guest Nanocomposite Materials (HGNM) was characterized by several techniques: chemical analysis, spectroscopic methods (DRS, FTIR and UV/Vis), BET technique, conductometric and magnetic measurements. The catalytic activities for oxidation of cyclohexane with HGNM complexes are reported. Zeolite-encapsulated tetrahydro-salophen copper(II) complexes; [Cu(H 4salophen)]-NaY; was found to be more active than the corresponding cobalt(II), manganese(II) and nickel(II) complexes for cyclohexane oxidation. The catalytic properties of the complexes are influenced by their geometry and by the steric environment of the active sites. HGNM are stable enough to be reused and are suitable to be utilized as partial oxidation catalysts. The encapsulated catalysts systems; [M(H 4salophen)]-NaY; were more active than the corresponding neat complexes; [M(H 4salophen)].

Ship-in-a-bottle synthesis, characterization and catalytic oxidation of cyclohexane by Host (nanopores of zeolite-Y)/guest (Mn(II), Co(II), Ni(II) and Cu(II) complexes of bis(salicyaldehyde)oxaloyldihydrazone) nanocomposite materials

The monomer transition metal complexes; [ML] (M = Mn(II), Co(II), Ni(II) and Cu(II)) have been synthesized from the reaction of metal acetate with bis(salicyaldehyde)oxaloyldihydrazone, H 2L; in 1:1 molar ratio in ethanol under reflux. In all of the complexes, the principal dihydrazone ligand has been suggested to coordinate to the metal centres in the anti- cis-configuration. The complexes (Co(II), Ni(II) and Cu(II)) are suggested to have four-coordinate square-planar stereochemistry while the Mn(II) complex is suggested to have tetrahedral stereochemistry. These metal complexes with tetradendate Schiff-base ligand was entrapped in the nanocavity of zeolite-Y by a two-step process in the liquid phase: (i) adsorption of [bis(salicylaldiminato)metal(II)]; [M(sal) 2]-NaY; in the supercages of the zeolite, and (ii) in situ Schiff condensation of the metal(II) precursor complex with oxaloyldihydrazone; [ML]-NaY. The new Host–Guest Nanocomposite Materials (HGNM) was characterized by several techniques: chemical analysis, spectroscopic methods (DRS, NMR, BET, FTIR and UV/vis), conductometric and magnetic measurements. The catalytic activities for oxidation of cyclohexane with HGNM and neat were reported.

Catalytic Activity of Co-HMS Modified by Organic Groups for Cyclohexane Oxidation

By a one-step co-condensation route using hexadecylamine as the template, various organic groups were successfully immobilized on the surface of hexagonal mesoporous silicas (HMS) along with Co2+ ions incorporated into the framework. The obtained bifunctionalized materials showed high activity in the selective oxidation of cyclohexane. The Co2+ cations were active for oxidation while the organic groups played the key roles in modifying the surface properties. During the oxidation reaction, a phenyl group was found to be better than methyl and propyl groups.

Studies on QSAR of metalloporphyrin catalysts in the oxidation of cyclohexane to adipic acid

The catalysis of chloridized metalloporphyrins in the oxidation of cyclohexane to adipic acid was systematically investigated. The turnover numbers (TON) data of 19 catalysts were obtained experimentally under optimal reaction conditions, and 2.4×106 TON for T(o-Cl)PP-MnIIICl catalyst at 2.0×10−6 mol/L of dosage was reached under the conditions of dioxygen pressure of 2.5 MPa at 150°C for 4 h. This was the best result reported for this reaction up to now. The QSAR models for each concerned metalloporphyrin were established, where the catalytic activity was significantly correlated with the E LUMO (the energy level of the lowest unoccupied molecule orbit) and L M-N (the bond length between metal-nitrogen atoms). Using the QSAR models, four new metalloporphyrins with substituted nitro group were designed, and their catalytic activities were predicted. The experimental TON data of newly designed porphyrins were in good agreement with the predicted ones, and the square of their correlation coefficient was more than 0.958. The above results demonstrated that the proposed structure-activity relationship model could be applied to design some new metalloporphyrin catalysts, and to predict their catalytic activity in cyclohexane oxidation.