Heterogeneous Catalyst For Epoxidation Research Articles

In situ synthesis and encapsulation of copper phthalocyanine into MIL-101(Cr) and MIL-100(Fe) pores and investigation of their catalytic performance in the epoxidation of styrene

In this work, copper phthalocyanine (CuPc) was encapsulated into mesocages of MIL-101(Cr) and MIL-100(Fe) by assembling CuPc’s constitutional fractions using a deep eutectic solvent. The prepared materials, CuPc@MIL-101(Cr) and CuPc@MIL-100(Fe), were characterized by powder X-ray diffraction (PXRD), FT-IR, UV-vis and diffuse reflectance UV (DR-UV) spectroscopies, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and ICP-OES spectrometry. The prepared materials were used as heterogeneous catalysts for catalytic epoxidation of styrene with molecular oxygen and also tert-butyl hydroperoxide (TBHP) as oxidants in acetonitrile as a solvent. The impact of MOFs and the role of the CuPc complex as the active species in the MOFs’ cages in the epoxidation of styrene were investigated. Among the prepared catalysts, CuPc@MIL-101(Cr) showed the best performance. The heterogeneity of the catalysts was examined by a hot filtration test and ICP-OES of the filtrates after the reaction. Spent catalysts were analyzed by PXRD, FT-IR, UV-DRS, and TEM for reusability investigation and also to further explore the heterogeneous nature of the hybrid materials. Results showed that the prepared catalysts could be recycled and used for several concoctive times without a considerable drop in activity.

Recent Advances in Facile Liquid Phase Epoxidation of Light Olefins over Heterogeneous Molybdenum Catalysts.

Molybdenum complexes are versatile and efficient for liquid phase olefin epoxidation reactions. Rational design of catalysts is critical to achieve high atom efficiency during epoxidation processes. Although liquid phase epoxidation has been a popular topic for decades, three key issues, (a) rational control of morphology of molybdenum nanoparticles, (b) manipulating metal-support interaction and (c) altering electronic configuration at molybdenum center remains unsolved in this area. Therefore, in this paper, we have critically revised recent research progress on heterogeneous molybdenum catalysts for facile liquid phase olefin epoxidation in terms of catalyst synthesis, surface characterization, catalytic performance and structure-function relationship. Furthermore, plausible reaction mechanisms will be systematically discussed with the aim to provide insights into fundamental understanding on novel epoxidation chemistry.

Copper(II) Schiff base complex immobilized on graphene nanosheets: a heterogeneous catalyst for epoxidation of olefins

The present paper describes the preparation and characterization of Cu(II) Schiff base complex immobilized onto graphene oxide. The structural and morphological characterization of the heterogeneous catalyst was carried out by different techniques such as Fourier transform infrared and diffuse reflectance UV–Vis spectroscopies, X-ray diffraction, thermogravimetric analysis, nitrogen adsorption–desorption, transmission electron microscopy, field emission scanning electron microscopy and inductively coupled plasma atomic emission spectroscopy. The catalytic activity of the heterogeneous catalyst was studied in the epoxidation of various alkenes using tert-butyl hydroperoxide as an oxidant and it showed high selectivity and catalytic reactivity. The graphene-bound copper Schiff base was successfully reused for several runs without significant loss in its catalytic activity.

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.

Palladium nanoparticles supported on UiO-66-NH2 as heterogeneous catalyst for epoxidation of styrene

A series of different amount of Pd nanoparticles were successfully loaded on the metal-organic frameworks UiO-66-NH2 using a simple solution impregnation method and applied as efficient catalysts for epoxidation of styrene. In this work, the best reaction efficiency can be explored by altering Pd loadings of Pd/UiO-66-NH2, solvents, reaction temperatures and the molar ratios of styrene to tert-butyl hydroperoxide. Interestingly, when Pd loadings of Pd/UiO-66-NH2 is 3.69 wt%, the target product can be obtained in high yield and selectivity.

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.

Synthesis of Nickel Lysine Salen Complex and Its Catalytic Performance for Styrene Epoxidation

Nickel lysine salen complex was successfully synthesized via a stepwise procedure and applied as a heterogeneous catalyst for styrene epoxidation. For comparison, several other transition metal (Mn, Fe, Co, and Cu) lysine salen complexes were also synthesized. The prepared catalysts were characterized by Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX). Data obtained by FT-IR and Raman spectroscopy indicated the formation of C=N bonds and the complexation of these bonds with metal ions. SEM analysis revealed that the complexation of metal ions with the C=N involves the change in surface morphology of samples. In addition, atomic percent composition of samples was obtained from EDX spectra, which was the complementary evidence for the formation of complexes. Results of catalytic measurements showed that a high conversion of styrene (91.51%) and selectivity to styrene oxide (91.99%) could be achieved over the nickel lysine salen complex with tert-butyl hydroperoxide as the oxidant. When the catalyst was reused the conversion of styrene decreased but the selectivity to styrene oxide still remained high.

Magnetic polymer microspheres based on phosphotungstic acid quaternary ammonium salt as an efficient heterogeneous catalyst for epoxidation of cyclohexene

The magnetic polymer microsphere catalysts based on phosphotungstic acid quaternary ammonium salt were designed and prepared in order to improve the performance and reusability of the catalysts during the epoxidation of cyclohexene. The structure, particle size and surface property of the new catalysts were characterized by FTIR, laser particle size analysis and SEM, respectively. And the reactivity of the catalysts was detected in cyclohexene epoxidation. Among the obtained catalysts, PS-double-D-PW4 catalyst exhibited the best catalytic performance and high stability for cyclohexene epoxidation. The results showed that the optimum yield of epoxycyclohexane was 83% with a selectivity above 95% after 7 h. And the catalyst still showed a conversion above 78% after six runs.

Cobalt immobilized on hydroxyapatite as a low-cost and highly effective heterogeneous catalyst for alkenes epoxidation under mild conditions.

Transition metal Co immobilized on hydroxyapatite with a loading of 0.05 wt% (denoted 0.05 wt% Co/HAP) could catalyze partial oxidation of cyclic alkenes, aromatic alkenes and aliphatic alkenes to yield epoxide products with excellent selectivity at 30 °C with O2 and iso-butyraldehyde as co-oxidant. The TOF value was as high as 6261 h−1 for epoxidation of cyclohexene. In addition, the prepared 0.05 wt% Co/HAP catalyst can be re-used at least 6 times without significant loss of catalytic activity and selectivity.

Extremely low loading of Ru species on hydroxyapatite as an effective heterogeneous catalyst for olefin epoxidation.

We report a new class promising heterogeneous catalyst for olefin epoxidation based on 0.05 wt% Ru species supported on hydroxyapatite, which was prepared through a simple cation-exchange process between RuCl3·nH2O and hydroxyapatite. The new catalyst showed high activity, excellent selectivity and good recyclability for various olefins in the presence of molecular oxygen and iso-butyraldehyde as co-oxidants.

Co(II) Schiff base complex decorated on polysalicylaldehyde as an efficient, selective, heterogeneous and reusable catalyst for epoxidation of olefins in mild and self-coreductant conditions

A new Co(II)-Schiff base complex was decorated on a polysalicylaldehyde (PSA) framework and used as a selective and efficient catalyst for the epoxidation of alkenes in the presence of O2 as a green source of oxygen without aco-reductant. The catalyst was characterized step by step by FTIR, UV–Vis, 1H NMR, TGA, CHN, XPS and EDX analyses. Loading an amount of Co ions in the catalyst as well as its leaching amount were studied by an ICP-OES instrument. The catalyst demonstrated excellent activity for the of a variety of alkenes in a mild, inexpensive and efficient protocol. Also, the catalyst can be simply recovered from the reaction mixture and reused for several times without any noteiceable loss in its activity. Reaction parameters including temperature, oxygen flow volume, catalyst amount and solvent were screened by reaction time. Catalytic studies including XPS spectroscopy and some blank experiments were performed to obtain an initial insight into the reaction mechanism. Also, the reactivity of the novel catalyst was evaluated as the turnover frequency. A new and efficient protocol have been developed for the selective epoxidation of olefins using a heterogeneous recyclable Co(II)-Schiff base complex of polysalicylaldehyde in mild and self-coreductant conditions by molecular oxygen.

Nanocluster polyoxomolybdate supported on natural zeolite: a green and recyclable catalyst for epoxidation of alkenes

A heterogeneous catalyst for epoxidation of alkenes has been synthesized by introducing polyoxomolybdate into a natural zeolite as a solid and green support. The prepared catalyst was characterized by FT-IR, inductively coupled plasma optical emission spectrometry (ICP-OES), powder X-ray diffraction (XRD), N2 absorption–desorption, field emission scanning electron micrograph (FE-SEM) and transmission electron microscopy (TEM). The catalytic investigations disclosed that nanocluster polyoxomolybdate supported on the surface is an active and recyclable catalyst in liquid phase alkene epoxidation in dichloroethane at 80 °C.

Superiority of Activated Carbon versus MCM‐41 for the Immobilization of Molybdenum Dithiocarbamate Complex as Heterogeneous Epoxidation Catalyst

AbstractTwo heterogeneous catalysts were developed by covalent anchoring of molybdenum‐dithiocarbamate complex onto the mesoporous silica (MCM‐41) and activated carbon (AC). Characterization of the functionalized materials by various physicochemical techniques indicated that the molybdenum complex is grafted successfully on the surface of supports. Textural properties of the prepared catalysts proved that the surface properties of supports have been changed after grafting of molybdenum‐dithiocarbamate complex. These heterogeneous catalysts were utilized for the epoxidation of olefins with tert‐butyl hydroperoxide (TBHP) as oxidant, presenting high efficiency and facile recovery. These catalysts can be reused five times without apparent loss of their catalytic performance. Also, the effect of the nature of MCM‐41 and AC supports on the catalytic activity has been discussed based on their hydrophobic and hydrophilic character.

Graphene oxide supported copper coordinated amino acids as novel heterogeneous catalysts for epoxidation of norbornene

In this work, we explored whether graphene oxide after modification with copper coordinated amino acids could attain an excellent catalytic activity for the epoxidation of norbornene. Therefore, graphene oxide sheets were functionalized with different amino acids through coordination to copper ions for the synthesis of copper coordinated amino acids-grafted graphene oxide. For this aim, at first amino acids were coordinated to Cu2+. Then, copper ions were complexed with GO. The catalytic activity of the prepared novel catalysts were tested in epoxidation of norbornene. These catalysts showed excellent catalytic performance compared with reported catalysts in other works which demonstrated graphene oxide as a support is superior to other support materials.

ChemInform Abstract: Heterogeneous Epoxidation of Alkenes with H2O2 Catalyzed by a Recyclable Organic—Inorganic Polyoxometalate‐Based Framework Catalyst.

Four organic–inorganic polyoxometalate-based frameworks (HSiW-MOF, PMo-MOF, HPMo-MOF and PW-MOF) were synthesised and characterized by elemental analysis, UV-vis and FT-IR spectroscopy, cyclic voltammetry and XRD analysis. Organic–inorganic polyoxometalate-based frameworks could act as effective and reusable heterogeneous catalysts for selective epoxidation of alkenes with aqueous hydrogen peroxide in acetonitrile. In the presence of PW-MOF, various kinds of alkenes could selectively be converted into the corresponding epoxides with high conversion and selectivity. PW-MOF was stable to leaching, behaved as true heterogeneous catalysts, easily recovered by filtration, and reused four times with maintenance of the catalytic performance.

Mn(TPPS)] immobilized on ionic liquid-modified silica as a heterogeneous and reusable catalyst for epoxidation of alkenes with NaIO4 under ultrasonic irradiation

Effective epoxidation of alkenes using sodium periodate was accomplished with Manganese (III) tetrakis(p-sulfonatophenyl)porphyrin, [C44H26N4O12S4Na4], supported on ionic liquids-modified silica, Im-SiO2, under ultrasonic irradiation conditions is reported. This heterogeneous catalyst, [Mn(TPPS)@SiO2-Im] was characterized by elemental analysis, scanning electron microscopy (SEM), FT-IR and UV–Vis spectroscopic methods. The synthesized hybrid catalyst was applied for efficient epoxidation of various alkenes with sodium periodate in acetonitrile under ultrasonic irradiation conditions. This solid catalyst can be easily recovered by simple filtration and reused several time without apparent loss of its catalytic activity.

Co(ii) complexes loaded into metal–organic frameworks as efficient heterogeneous catalysts for aerobic epoxidation of olefins

An efficient cobalt(ii)-anchored Cr-MOF (Cr-MIL-101-NH2) catalyst, Co(ii)@Cr-MIL-101-P2I, has been successfully synthesized by one-pot modification of the terminal amino group with pyridine-2-aldehyde and anchoring of Co(ii) ions into the mesoporous Cr-MOF support.

A one-dimensional polyoxomolybdate polymer as a catalyst for the epoxidation of olefins

A 1-D polyoxomolybdate-based polymer as heterogeneous catalyst for olefin epoxidation.

Gold nanoparticles supported on nanoscale amine-functionalized MIL-101(Cr) as a highly active catalyst for epoxidation of styrene

Gold nanoparticles can effectively be incorporated on to the matrix of NH2-MIL-101(Cr) by a facile solution approach. The resulting nanocatalyst acts as efficient heterogeneous catalyst for epoxidation of styrene.

Catalyst structure and substituent effects on epoxidation of styrenics with immobilized Mn(tmtacn) complexes

Monomeric and dimeric complexes of Mn 1,4,7-trimethyl-1,4,7-triazacyclononane (tmtacn) were immobilized under reaction conditions onto solid supports to create heterogeneous catalysts for epoxidation with H2O2. These solid supports consist of activated carbon or silica grafted or co-condensed with benzoic or C3/C4 acids that function both as tethering points and as required co-catalysts. Immobilized catalysts were as much as 50-fold faster than the analogous soluble system, and an immobilized, dimeric Mn(tmtacn) complex with a solid benzoic acid co-catalyst gave the highest yields to epoxide. A Hammett study on the catalytic epoxidation of a series of styrenes showed weak increases in yield for more electron-withdrawing p-substituents reactants for both immobilized complexes, which runs counter to previous observations with analogous homogeneous catalysts, and which appears to reflect a previously unappreciated tradeoff between the intrinsic epoxidation reactivity and strong catalyst inhibition by styrene oxides and glycols. Finally, these catalysts were tested with a variety of solid-co-catalysts, and were successfully utilized in the challenging epoxidation of divinylbenzene to industrially-useful divinylbenzene dioxide using a cascade of two catalyst charges.