Catalyst For Epoxidation Of Olefins Research Articles

Functionalization of magnetite–chitosan nanocomposite with molybdenum complexes: new efficient catalysts for epoxidation of olefins

Functionalization of magnetite–chitosan core–shell-type nanocomposite with molybdenum–Schiff base complex through a simple step-by-step path results in the preparation of new catalysts for the epoxidation of olefins. The functionalized nanocomposites were characterized by Fourier-transform infrared spectroscopy, X-ray diffractometry, energy-dispersive X-ray spectroscopy, scanning electron microscopy and vibrating-sample magnetometry. Finally, their abilities to catalyze the epoxidation of olefins with tert-butyl hydroperoxide in chloroform were evaluated. It was found that the prepared functionalized nanocomposites have high catalytic activities for heterogeneous epoxidation of olefins with epoxide as the main product in all cases. In particular, when the cyclooctene was employed as olefin, complete conversion and selectivity for epoxycyclooctene and high turnover frequency were obtained at 60 °C. The functionalized nanocomposites can be easily separated magnetically for reusing, and no activity loss was observed in five consecutive runs.

Synthesis, characterization and catalytic epoxidation properties of a new tellurotungstate(iv)-supported rhenium carbonyl derivative.

A monomeric tellurotungstate(iv)-supported rhenium carbonyl derivative: Na2H2[(CH3)4N]6[Te2W20O70{Re(CO)3}2]·20H2O (1) has been successfully isolated and structurally characterized by single crystal X-ray diffraction crystallography, IR and UV-Vis spectroscopy, thermogravimetric analysis, etc. In particular, complex 1 could act as a efficient and reusable heterogeneous catalyst for selective epoxidation of various alkenes including different cycloalkenes, styrene derivatives, internal and long-chain alkenes. For example, cis-cyclooctene undergoes up to 98.2% conversion and >99% selectivity at 75 °C in acetonitrile with 30% H2O2 as an oxidant. Additionally, the electrocatalytic property of 1 for NO2- reduction was also investigated.

Vanadyl β-tetrabromoporphyrin: synthesis, crystal structure and its use as an efficient and selective catalyst for olefin epoxidation in aqueous medium.

We hereby report the synthesis, characterization and catalytic applications in the epoxidation of alkenes by a vanadyl porphyrin having bulky bromo substituents at the β-positions viz. vanandyltetrabromotetraphenylporphyrin (1). The synthesized porphyrin was characterized by various spectroscopic techniques like UV-visible, FT-IR, EPR, MALDI-TOF mass spectrometry and single crystal X-ray analysis. Porphyrin 1 has a nonplanar structure as indicated by its X-ray structure, DFT and electrochemical studies. 1 was analyzed for its catalytic application in the epoxidation of various alkenes. The catalytic reactions were carried out in CH3CN/H2O mixture in 3 : 1 (v/v) ratio. 1 displayed good efficiency in terms of mild reaction conditions, lower reaction temperature and minimal catalyst amount consumption. 1 exhibited excellent selectivity, high conversion efficiency and huge TOF (7600–9800 h−1) in a significantly low reaction time of 0.5 h. Catalyst 1 was regenerated at the end of various catalytic cycles making it reusable and industrially important.

Hollow core-shell structured TS-1@S-1 as an efficient catalyst for alkene epoxidation.

Hollow core–shell structured TS-1@S-1 zeolite (HCS-TS) was prepared successfully for the first time, which exhibited excellent activity in the epoxidation of alkenes. Combining TEM, UV-vis, UV-Raman, pyridine-IR, solid-state MAS NMR, XPS and so on characterization, the improvement in the catalytic performance of hollow core–shell structured TS-1@S-1 zeolite was credited to the newly formed superior active sites: defective Ti(OSi)3(OH) species in HCS-TS and six-coordinated titanium active species in uncalcined HCS-TS (HCS-TSP). Interestingly, these two different titanium active species in the samples could be constructed through calcination or not in the same synthesis process. A possible formation mechanism was investigated in detail; it indicated that the hollowing treatment of TS-1 in the first step was conducive to the construction of the new superior active sites in the samples, and there was a synergistic effect on the formation of these active sites between TPAOH and TEOS in the second step of the synthesis process. This strategy is feasible to enhance the catalytic performance of TS-1, and is suitable for the synthesis of TS-1 on an industrial scale.

Polymer immobilized tantalum(v)–amino acid complexes as selective and recyclable heterogeneous catalysts for oxidation of olefins and sulfides with aqueous H2O2

Polymer supported peroxotantalate based heterogeneous catalysts served as highly efficient, selective and recyclable catalysts for alkene epoxidation and sulfide oxidation with green oxidant aqueous H2O2under mild reaction conditions.

Synthesis and crystal structures of oxidovanadium(V) complexes derived from hydrazones with the catalytic property

Two new structurally similar oxidovanadium(V) complexes [VOL1L] (1) and [VOL2L] (2) (L = acetohydroxamate) derived from N'-(5-bromo-2-hydroxybenzylidene)-2-methylbenzo­hydrazide (H2L1) and N'-(2-hydroxy-4-methoxybenzylidene)-3-methylbenzohydrazide (H2L2) hydrazones are prepared and characterized by elemental analyses, FT—IR, 1H NMR, and single crystal X-ray diffraction (CIF files CCDC Nos. 1859442 (1) and 1859446 (2)). The V atoms in the complexes are in the octahedral coordination, with hydrazones behaving as binegative donors and acetohydroxamate acting as a mono-negative ligand. The complexes function as effective olefin epoxidation catalysts.

Synthesis, Crystal Structures and Catalytic Property of Oxidovanadium(V) Complexes with Similar Aroylhydrazones

A pair of new oxidovanadium(V) complexes, [VOL1L]·EtOH (1) and [VOL2L]·EtOH (2) (L = acetohydroxamate), derived from the aroylhydrazones N'-(5-bromo-2-hydroxybenzylidene)-4-methoxybenzohydrazide (H2L1) and N'-(5-bromo-2-hydroxybenzylidene)-4-methylbenzohydrazide (H2L2), have been prepared and characterized by elemental analyses, FT-IR, 1H and 13C NMR spectroscopy and single-crystal structural X-ray diffraction. The complexes have octahedral structures in which the aroylhydrazone ligands behave as binegative donors. Single-crystal structure analyses reveal that the V centers are coordinated by the donor atoms of the aroylhydrazone ligands, the acetohydroxamate ligands and the oxido groups.Crystal structures of the complexes are stabilized by hydrogen bonds. The complexes function as effective olefin epoxidation catalysts.

Enhanced catalytic activity over Mo-containing hierarchical macro-mesoporous SBA-15 catalysts for epoxidation of olefins

In this study, a novel Mo-containing hierarchical ordered macro-mesoporous material, Mo-MM-SBA-15-4-30, was synthesized via a facile dual-templating technique. The formation of a well-defined macro-mesoporous structure was verified by N2 adsorption–desorption curves, SEM and TEM observations. Moreover, the characterization results of XPS, ICP-AES, EDX demonstrated the successful incorporation of molybdenum species into the bulk hierarchical macro-mesoporous material Mo-MM-SBA-15-4-30. A series of comparative studies revealed that this hierarchical macro-mesoporous material Mo-MM-SBA-15-4-30 exhibited higher catalytic activities for the epoxidation of linear α-olefin than Mo-containing mesoporous silica. Turnover number of linear α-olefins was also significantly enhanced due to the hierarchical macro-mesoporous structure of Mo-MM-SBA-15-4-30 in which the presence of mesoporous channels shortened diffusion limitation. Additionally, the catalyst Mo-MM-SBA-15-4-30 exhibits the excellent catalytic stability.

Analysis of the variables that modify the robustness of Ti-SiO2 catalysts for alkene epoxidation: Role of silylation, deactivation and potential solutions

Catalytic epoxidation of alkenes plays an essential role in the transformation and synthesis of many organic chemicals. Ti atoms grafted on mesoporous silica, silylated on the surface, is considered the most active and selective catalyst for these reactions. However, the durability and robustness of the active centers remain as the main drawback in industry. In this paper, the characterization of industrial samples is combined with DFT calculations to rationalize the deactivation process of the catalyst and improve its performance. Silylating agents are characterized by experimental and simulated 29Si-NMR and their role in the catalytic mechanism is analysed. Potential deactivation processes are identified before, during and after the reaction. Modifications of the silylating agents and of the active center are proposed to improve the durability of the catalyst.

A General and Simple Method of Preparing Molybdenum‐ Incorporated Silica Nanoparticles as Potential Catalysts for Epoxidation of Alkenes

AbstractMolybdenum incorporated silica nanoparticles were synthesized by a general and simple method and developed as efficient catalysts for epoxidation of alkenes with high performance. The nanoparticles were prepared in mild conditions with cetyltrimethyl ammonium bromide as template, tetraethyl orthosilicate as silica source and triethanolamine as mineralizing agent. Molybdenum precursor was added during the sol‐gel process and transferred to active sites MoO3 after calcination. Remarkably, the shape of silica nanoparticles gradually changed from raspberry to rose with the rising dosage of molybdenum precursor. The materials were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption/desorption, inductively coupled plasma‐atom emission spectroscopy (ICP‐AES) and X‐ray photoelectron spectra (XPS). To determine the reactivity of catalysts, epoxidation of cyclooctene was carried out as a model reaction. After 12 h reaction with H2O2 (50 wt%), above 92% conversion and 95% selectivity were reached. Furthermore, the catalyst still had high conversion (74%) and selectivity (97%) for 4 h epoxidation of cyclooctene even after being recycled for 6 runs.

Molybdenum complex supported on amine-functionalized natural sepiolite-type clay mineral as a recyclable inorganic-organic hybrid catalyst for epoxidation of alkenes

Sepiolite-based molybdenum catalyst (Sep-Am-MoO2) was prepared by immobilization of a bis-acetylacetonato-dioxo-molybdenum (VI) complex [MoO2(acac)2] onto the surface of sepiolite clay mineral which was functionalized by 3-(tri-methoxysilyl)propylamine (MSPA). Then the surface-functionalized sepiolite was characterized by the Fourier transform-infrared (FT-IR), X-ray fluorescence and X‐ray‐photoelectron spectroscopies along with powder X‐ray diffraction, thermal analysis, elemental analysis, inductively coupled plasma (ICP), and surface area (BET) techniques. Then it was applied for the catalytic epoxidation of cis-cyclooctene and the effect of several parameters such as the solvent, catalyst and oxidant contents, temperature, and time on this reaction were studied. Then it was used for the epoxidation of some other alkenes. Furthermore, because the use of this novel catalyst in large-scale reactions showed great catalytic activity, it could be a convincing candidate for the application in industry. More importantly, natural and cheap clay mineral precursor, facile preparation, simple work-up procedure, high product yield, high turn-over frequency, (TOF), and easy recovery and reusability, make Sep-Am-MoO2 an efficient candidate as a catalyst for the epoxidation of alkenes in the research and industrial applications.

Modification of Cu2+ into Zr-based metal–organic framework (MOF) with carboxylic units as an efficient heterogeneous catalyst for aerobic epoxidation of olefins

A series of metal-organic framework (MOF) based catalysts for aerobic epoxidation were reported. A post-synthetic modification strategy using a solvothermal method enabled the incorporation of three different copper salts on a Zr-based MOF material UiO-66-(COOH)2; catalysts Cu@UiO-1, Cu@UiO-2 and Cu@UiO-3 were obtained. When analyzed by SEM and EDX, no impact of the post-synthetic modification on the core structure of the UiO-66-(COOH)2 framework was noticed. Studies showed Cu@UiO-1 to be the optimal catalyst for aerobic epoxidation thanks to its broad substrate scope, thermal stability, excellent recyclability. Observed catalytic properties are also better than those of previously reported copper catalysts.

Ionic ammonium and anilinium based polymolybdate hybrid catalysts for olefin epoxidation

Ionic polymolybdate hybrids (IPH) are interesting catalysts for liquid phase olefin epoxidation with tert-butylhydroperoxide; (tbhp), e.g. conversion of terpenic and fatty acid methyl ester (FAME) components of biomass to useful bio-products. IPHs may be easily prepared, under clean, mild, aqueous phase conditions. The type of organic precursor and the synthesis conditions influence the structural features of the IPHs. In this work, IPH epoxidation catalysts possessing one- (1-D) or two-dimensional (2-D) structures were investigated, which included the new materials 1-D methylammonium ammonium trimolybdate [Mo3O10⋅CH3NH3·NH4] (1) and 2-D bis(2,5-dimethylanilinium) pentamolybdate [Mo5O16·2(NH3C6H3(CH3)2)] (4) with solved structures, and 1-D bis(3,5-dimethylanilinium) trimolybdate [Mo3O10·2(NH3C6H3(CH3)2)] (2), bis(4-methylanilinium) trimolybdate [Mo3O10·2(NH3C6H4CH3)] (3), 2-D bis(anilinium) pentamolybdate [Mo5O16·2(NH3C6H5)] (5), bis(4-methylanilinium) pentamolybdate [Mo5O16·2(NH3C6H4CH3)] (6) and bis(4-ethylanilinium) pentamolybdate [Mo5O16·2(NH3C6H4C2H5)] (7). Systematic characterisation and catalytic studies helped gain insights into structure-activity relationships. The best-performing catalyst (2) was effective for the epoxidation of the FAMEs such as, methyl oleate which gave 92% methyl 9,10-epoxyoctadecanoate yield, at 99% conversion, at 70 °C. The reaction conditions (temperature, type of cosolvent and oxidant) influenced the catalytic reaction. Catalytic performance in consecutive batch runs was steady, and the structural features were essentially preserved.

Olefin epoxidation with metal-based nanocatalysts

ABSTRACTAlkene epoxidations are an important class of reactions carried out in industry; however, current methods are plagued by problems, including high cost, difficulty in recovering catalysts, and generation of large quantities of acidic and chlorinated waste. In recent years, nanocatalysts have been considered as robust, heterogeneous alternatives to homogeneous catalysts. This work evaluates silver- and base metal-containing nanocatalysts as olefin epoxidation catalysts, highlighting the industrial applicability and green aspects of these catalytic systems. The nanocatalysts discussed are mostly supported or composite materials that showed (generally) good activity and selectivity for various/multiple olefin epoxidation reactions.

Manganes-Porphyrin as Efficient Enantioselective Catalyst for Aerobic Epoxidation of Olefins

A chiral manganese porphyrin, [Mn(TCPP-Ind)Cl], was synthesized using cis-1-amino-2-indanol substituent. It showed remarkable catalytic activity and enantioselectivity in the epoxidation of olefins with O2/RCHO. Terminal olefins and styrene derivatives were successfully oxidized (> 99% ee). TON of 73,000 was achieved in the epoxidation of α-methylstyrene after five times recycling.

Non-Heme Iron Catalysts for Olefin Epoxidation: Conformationally Rigid Aryl-Aryl Junction To Support Amine/Imine Multidentate Ligands.

Atom-transfer chemistry represents an important class of reactions catalyzed by metalloenzymes. As a functional mimic of non-heme iron enzymes that deliver oxygen atoms to olefins, we have designed monoiron complexes supported by new N-donor chelates. These ligands take advantage of heme-like conformational rigidity of the π-conjugated molecular backbone, and synthetic flexibility of tethering non-heme donor groups for additional steric and electronic control. Iron complexes generated in situ can be used to carry out catalytic epoxidation of a wide range of olefin substrates by using mCPBA as a terminal oxidant. The fate of initial iron-peracid adduct and the involvement of iron-oxo species in this process were investigated further by mechanistic probes and isotope exchange studies. Our findings suggest that anilidopyridyl-derived [N,N]-bidentate motif could serve as a versatile structural platform to build non-heme ligands for catalytic oxidation chemistry.

WITHDRAWN: Molybdenum complex supported on amine-functionalized natural sepiolite-type clay mineral as a recyclable inorganic-organic hybrid catalyst for epoxidation of alkenes

Abstract Sepiolite-based molybdenum catalyst (Sep-Am-MoO2) was prepared by immobilization of a bis-acetylacetonato-dioxo-molybdenum (VI) complex [MoO2(acac)2] onto the surface of sepiolite clay mineral which was functionalized by 3-(tri-methoxysilyl)propylamine (MSPA). Then the surface-functionalized sepiolite was characterized by the Fourier transform-infrared (FT-IR), X-ray fluorescence and X‐ray‐photoelectron spectroscopies along with powder X‐ray diffraction, thermal analysis, elemental analysis, inductively coupled plasma (ICP), and surface area (BET) techniques. Then it was applied for the catalytic epoxidation of cis-cyclooctene and the effect of several parameters such as the solvent, catalyst and oxidant contents, temperature, and time on this reaction were studied. Then it was used for the epoxidation of some other alkenes. Furthermore, because the use of this novel catalyst in large-scale reactions showed great catalytic activity, it could be a convincing candidate for the application in industry. More importantly, natural and cheap clay mineral precursor, facile preparation, simple work-up procedure, high product yield, high turn-over frequency, (TOF), and easy recovery and reusability, make Sep-Am-MoO2 an efficient candidate as a catalyst for the epoxidation of alkenes in the research and industrial applications.

One‐Step Synthesis of Hybrid Core–Shell Metal–Organic Frameworks

AbstractEpitaxial growth of MOF‐on‐MOF composite is an evolving research topic in the quest for multifunctional materials. In previously reported methods, the core–shell MOFs were synthesized via a stepwise strategy that involved growing the shell‐MOFs on top of the preformed core‐MOFs with matched lattice parameters. However, the inconvenient stepwise synthesis and the strict lattice‐matching requirement have limited the preparation of core–shell MOFs. Herein, we demonstrate that hybrid core–shell MOFs with mismatching lattices can be synthesized under the guidance of nucleation kinetic analysis. A series of MOF composites with mesoporous core and microporous shell were constructed and characterized by optical microscopy, powder X‐ray diffraction, gas sorption measurement, and scanning electron microscopy. Isoreticular expansion of microporous shells and orthogonal modification of the core was realized to produce multifunctional MOF composites, which acted as size selective catalysts for olefin epoxidation with high activity and selectivity.

One-Step Synthesis of Hybrid Core-Shell Metal-Organic Frameworks.

Epitaxial growth of MOF-on-MOF composite is an evolving research topic in the quest for multifunctional materials. In previously reported methods, the core-shell MOFs were synthesized via a stepwise strategy that involved growing the shell-MOFs on top of the preformed core-MOFs with matched lattice parameters. However, the inconvenient stepwise synthesis and the strict lattice-matching requirement have limited the preparation of core-shell MOFs. Herein, we demonstrate that hybrid core-shell MOFs with mismatching lattices can be synthesized under the guidance of nucleation kinetic analysis. A series of MOF composites with mesoporous core and microporous shell were constructed and characterized by optical microscopy, powder X-ray diffraction, gas sorption measurement, and scanning electron microscopy. Isoreticular expansion of microporous shells and orthogonal modification of the core was realized to produce multifunctional MOF composites, which acted as size selective catalysts for olefin epoxidation with high activity and selectivity.

Mn(III) and Mn(II) complexes of tridentate Schiff base ligands; synthesis, characterization, structure, electrochemistry and catalytic activity

Abstract Three Mn(III) complexes [Mn(L1)2] (ClO4) 1, [Mn(L2)2] (ClO4) 2, [Mn(L3)2] (ClO4) 3, and one Mn(II) complex [Mn(L4)2] 4 were studied for their efficiency as catalysts for epoxidation of olefins with H2O2 at room temperature and 0 °C in the presence of ammonium acetate-acetic acid or triethylamine-perchloric acid system as co-catalyst/buffer. The complexes were obtained from the reaction of Mn(ClO4)2.6H20 with NNO tridentate Schiff base ligands HL1-HL4 synthesized from the condensation reaction of 2-(2-aminoethyl)pyridine and 2-hydroxybenzaldehyde (HL1), 5-chloro-2-hydroxybenzaldehyde (HL2), 5-methoxy-2-hydroxybenzaldehyde (HL3), or 5-nitro-2-hydroxybenzaldehyde (HL4) respectively. The complexes were characterized by spectroscopic techniques as well as by single crystal X-ray diffraction analysis. Electronic effect of the substituents on epoxide yield was also investigated. The crystal structures of complexes confirm coordination of the manganese ion to the ligands through the NNO atoms of the ligands. The spectral changes observed as a function of time for the reaction of the complexes with aqueous (30%) hydrogen peroxide indicates possible formation of an intermediate product; hydroperoxo-complex implicated in the epoxidation reaction. The complexes catalyzed epoxidation of cyclohexene with low yield at room temperature but higher yield at 0 °C in the order complex 3 lower than 1, 1 lower than 2, with the Mn(II) complex 4 recording highest epoxide yield of 9% with turnover of 2.25 at room temperature and yield of 58% with turnover of 14.5 at 0 °C in the presence of ammonium acetate-acetic acid system/ buffer. With the triethylamine-perchloric acid system/buffer, epoxide yield of 46% and turnover of 11.5 was recorded at room temperature while 44% with turnover of 11.0 was obtained at 0 °C for complex 4.