Hybrid Heterogeneous Catalyst Research Articles

Synthesis and characterization of Piperidine-4-carboxylic acid functionalized Fe3O4 nanoparticles as a magnetic catalyst for Knoevenagel reaction

Piperidine-4-carboxylic acid (PPCA) functionalized Fe3O4 nanoparticles as a novel organic–inorganic hybrid heterogeneous catalyst was fabricated and characterized by XRD, FT-IR, TGA, TEM and VSM techniques. Composition was determined as Fe3O4, while particles were observed to have spherical morphology. Size estimations using X-ray line profile fitting (10nm), TEM (11nm) and magnetization fitting (9nm) agree well, revealing nearly single crystalline character of Fe3O4 nanoparticles. Magnetization measurements reveal that PPCA functionalized Fe3O4 NPs have superparamagnetic features, namely immeasurable coercivity and absence of saturation. Small coercivity is established at low temperatures. The catalytic activity of Fe3O4–PPCA was probed through one-pot synthesis of nitro alkenes through Knoevenagel reaction in CH2Cl2 at room temperature. The heterogeneous catalyst showed very high conversion rates (97%) and could be recovered easily and reused many times without significant loss of its catalytic activity.

Proline confined FAU zeolite: heterogeneous hybrid catalyst for the synthesis of spiroheterocycles via a Mannich type reaction

A novel L-proline confined FAU zeolite catalyst system has been developed by confinement of L-proline in faujasite zeolite and its catalytic activity has been tested in the aqueous mediated synthesis of novel 1′,3′-di-(4-methylphenyl)-2′,3′,4′,6′-tetrahydro-1′H-spiro[indoline-3,5′-pyrimidin]-2-one (4a) and 1′,3′-di-(4-methylphenyl)-2′,3′,4′,6′-tetrahydro-1′H-spiro[indene-2,5′-pyrimidin]-1(3H)-one (4d) for the first time via the one-pot three-component condensation of lactams/cyclic ketones, amines and aqueous formaldehyde. The recyclability of the novel catalyst system was studied, which resulted in no loss of catalytic activity up to five cycles.

Sulfamic acid-functionalized magnetic Fe 3O 4 nanoparticles as an efficient and reusable catalyst for one-pot synthesis of α-amino nitriles in water

Grafting of chlorosulfuric acid on the amino-functionalized Fe 3O 4 nanoparticles afforded sulfamic acid-functionalized magnetic Fe 3O 4 nanoparticles (SA-MNPs) as a novel organic–inorganic hybrid heterogeneous catalyst, which was characterized by XRD, FT-IR, TGA, TEM, and elemental analysis. The catalytic activity of SA-MNPs was probed through one-pot synthesis of α-amino nitriles via three-component couplings of aldehydes (or ketones), amines and trimethylsilyl cyanide in water, at room temperature. The heterogeneous catalyst could be recovered easily and reused many times without significant loss of its catalytic activity.

A reusable Mn(ii)-dampy-MCM-41 system for single step amination of benzene to aniline using hydroxylamine

Reaction methodology for C–H bond amination of benzene catalyzed by Mn(II)-dien (ampy) immobilized organo modified MCM-41 in the presence of hydroxylamine in acetic acid–water medium is described. The organic–inorganic hybrid heterogeneous catalyst achieves high catalytic activity and selectivity for one step amination of benzene. Characterization of the immobilized catalyst by powder X-ray diffraction (XRD), N2 adsorption–desorption, CP MAS NMR spectroscopy (13C and 29Si), Fourier transform infrared spectroscopy (FT-IR) and diffuse reflectance UV–Vis spectroscopy demonstrates the successful grafting of the complex into functionalized mesoporous silica and that the mesostructure has not been destroyed in the multistep synthetic procedure. The variation of reaction conditions such as solvent, temperature, time, catalyst concentration etc. is well demonstrated to achieve high catalytic activity. Moreover, the anchored catalyst can be recovered and reused for multiple cycles without appreciable loss in catalytic activity, which is an alternative to the conventional industrial process.

A facile method for promoting activities of vanadium–schiffbase complex anchored on organically modified MCM-41 in epoxidation reaction

An organic–inorganic hybrid heterogeneous catalyst (V-MCM-41) was synthesized by anchoring vanadium–schiffbase complex on chloropropyl modified mesoporous silica (CP-MCM-41). Characterization of the functionalized ordered two-dimensional mesoporous material by powder X-ray diffraction (XRD), N 2 adsorption–desorption, CP-MAS NMR spectroscopy ( 13C and 29Si), Fourier transform infrared spectroscopy (FT-IR), diffuse-reflectance UV–vis spectroscopy, demonstrate the successful grafting of vanadium complex into the functionalized mesoporous silica. It is also observed that the mesostructure has not been destroyed in multistep synthetic procedure. We have performed the epoxidation reaction of various olefins using V-MCM-41 as the catalyst, hydrogen peroxide as the oxidant and sodium bicarbonate as the co-catalyst in acetonitrile solvent. The co-catalyst enhances the rate of reaction by many folds. The reaction requires minimum amount of H 2O 2, short time period and most importantly occurs at room temperature. The heterogeneous catalyst can be recovered easily and reused many times without significant loss in catalytic activity and selectivity.

Photo-induced ring-expansion reactions mediated by B12-TiO2 hybrid catalyst

Vitamin B(12)-TiO(2) heterogeneous hybrid catalyst (B(12)-TiO(2)) mediated ring-expansion reactions and their reaction mechanism were clarified by various spectroscopic methods. Diffuse reflectance UV/VIS (DR-UV/VIS) studies showed that B(12)-TiO(2) was activated to form the supernucleophilic Co(I) species of B(12) by irradiation with ultraviolet light. DR-UV/VIS and electron spin resonance (ESR) studies then elucidated the formation of the photo-sensitive intermediate on heterogeneous surfaces. The photo-excited B(12)-TiO(2) catalyzed ring-expansion reactions were efficient and eco-friendly. This catalytic efficiency was strongly dependent on the kind of solvent. The oxidation reaction of the solvent by holes at TiO(2) nanoparticle surfaces had a crucial role in the overall catalytic reaction.

Response surface methodology (RSM) analysis of photoinduced decoloration of toludine blue

In this study, the decoloration of toludine blue (TB) in the presence of UV radiation and heterogeneous hybrid catalyst, namely titanium oxide impregnated with vanadium oxide was optimized using response surface methodology (RSM). The optimum removal conditions were determined as 26.5 mg/20 mL V2O5/TiO2 catalyst concentration at pH 7.7. At optimized conditions the complete decoloration was obtained at 50 MT B concentration. In the optimization, R 2 and R 2 correlation coefficients for quadratic model was evaluated quite satisfactorily as 0.98 and 0.96, respectively.

The effect of operational parameters on the photoinduced decoloration of dyes using a hybrid catalyst V2O5/TiO2

Abstract The decoloration of three dyes namely Toludine Blue, Safranin Orange and Crystal Violet was studied in the presence of UV radiation using a heterogeneous hybrid catalyst, namely titanium oxide impregnated with vanadium oxide. The advantage of using a hybrid catalyst lies in the fact that the decoloration increased by more than five times as compared to in a neat catalyst. The influence of operational parameters, such as dye concentration, amount of catalyst and pH of the solution were thus determined for dye decoloration using a hybrid catalyst. Rate of photoinduced catalytic decoloration was calculated from the observed absorption changes and the induced effects were explained on a mechanistic model involving the generation of OH radicals which are responsible for the decoloration of dye solution. The kinetic data fitted well to pseudo first order equation and the Langmuir–Hinshelwood model. Dye decoloration was also investigated in the presence of some ions and their role was discussed in terms of chemical reactions.

Dioxomolybdenum(VI) modified mesoporous materials for the catalytic epoxidation of olefins

Organic–inorganic hybrid heterogeneous catalyst systems were synthesized by the reaction of the dioxomolybdenum(VI) complex MoO 2Cl 2(THF) 2 with the mesoporous silica MCM-41 functionalized with a pyrazolylpyridine ligand (MCM-41-PP). Two catalysts were prepared, one of which involved the postsynthesis trimethylsilylation of MCM-41-PP to remove the residual surface silanol groups. The model complex MoO 2Cl 2L {L = ethyl[3-(2-pyridyl)-1-pyrazolyl]acetate} was also synthesized. Elemental analysis of the supported mesoporous materials indicated molybdenum loadings of 8.0 wt.% (0.83 mmol g −1) for MCM-41-PP·MoO 2Cl 2 and 7.0 wt.% (0.73 mmol g −1) for silylated MCM-41-PP·MoO 2Cl 2. The supported materials were further characterized by N 2 adsorption, 13C/ 29Si (CP) MAS NMR, IR and Raman spectroscopy. The spectroscopic data are consistent with the successful formation of tethered complexes of the type MoO 2Cl 2(PP), although the materials also contained an excess of dioxomolybdenum(VI) species that were probably not coordinated directly with the surface-bound ligands. The modified materials are active and selective in the epoxidation of cyclooctene at 328 K using t-BuOOH (in decane) as the oxidant and no additional solvent. The initial specific reaction rates were about 350 mol mol Mo −1 h −1 for the modified materials and also the model complex MoO 2Cl 2L. Stability was checked by recycling the solid catalysts several times. Some activity is lost from the first to second runs, but thereafter stabilizes. The catalytic performance of the hybrid materials was further investigated in the oxidation of α-pinene, ( R)-(+)-limonene, trans-2-octene and 1-octene.

Mesoporous SBA-15 material functionalized with ferrocene group and its use as heterogeneous catalyst for benzene hydroxylation

An organic–inorganic hybrid heterogeneous catalyst system was synthesized by covalently anchoring ferrocene onto the mesoporous silica SBA-15 materials. FT-IR, TG-DSC-MS, and EDS analyses demonstrate that the ferrocene has been grafted successfully into the mesoporous SBA-15 materials. Powder X-ray diffraction, HRTEM, and nitrogen adsorption–desorption analysis proved that the textural characteristics of the support were preserved during the drafting experiments and the channels remained accessible, despite the sequential reductions in surface area, pore volume and pore size. The hybrid materials exhibit high catalytic activity for benzene oxidation, with hydrogen peroxide as the oxygen source, and are recyclable and reusable without apparently reduced activity.

Mesoporous MCM-41 Materials Modified with Oxodiperoxo Molybdenum Complexes: Efficient Catalysts for the Epoxidation of Cyclooctene

An organic−inorganic hybrid heterogeneous catalyst system was synthesized by covalently anchoring oxodiperoxo molybdenum complexes [(L−L)MoO(O2)2] (L−L = (3-triethoxysilylpropyl)[3-(2-pyridyl)-1-pyrazolyl]acetamide) onto the mesoporous silica MCM-41 (Si−MCM-41) and aluminosilicate MCM-41 (Al−MCM-41) materials. Characterization of the functionalized materials by powder X-ray diffraction (XRD), N2 adsorption, and solid-state CP-MAS NMR spectroscopy (13C and 29Si) demonstrates that the oxodiperoxo molybdenum complexes are grafted successfully into the mesoporous MCM-41 materials. The structures of both the mesoporous materials and the molybdenum complex are preserved during the grafting process. All the hybrid materials are active and truly heterogeneous catalysts for the liquid-phase epoxidation of cyclooctene with tBuOOH as the oxygen source. The catalytic properties (activity and recyclability) of the supported materials can be improved by their further silylation using Me3SiCl, which can be explained by ...

Oxodiperoxo Molybdenum Modified Mesoporous MCM‐41 Materials for the Catalytic Epoxidation of Cyclooctene.

A hybrid heterogeneous catalyst system, which has been synthesized by covalently anchoring oxodiperoxo molybdenum chelate complexes onto the surface of mesoporous MCM-41, is highly active and truly heterogeneous for the liquid-phase epoxidation of cyclooctene with tBuOOH as the oxygen source.

Oxodiperoxo molybdenum modified mesoporous MCM-41 materials for the catalytic epoxidation of cyclooctene.

A hybrid heterogeneous catalyst system, which has been synthesized by covalently anchoring oxodiperoxo molybdenum chelate complexes onto the surface of mesoporous MCM-41, is highly active and truly heterogeneous for the liquid-phase epoxidation of cyclooctene with tBuOOH as the oxygen source.

ROMP and RCM catalysed by (R 3P) 2Cl 2RuCHPh immobilised on a mesoporous support

Heterogeneous hybrid catalysts with respect to the metathesis of olefins have been prepared by ligand exchange reaction between Ru-alkylidene complexes (Grubbs’ type) and a phosphinated mesoporous matrix (P-MCM-41). The host/guest interaction is studied by FT-Raman, thermogravimetric analysis and N 2 adsorption. Catalytic tests in olefin metathesis reveal ROMP activity towards norbornene, even in aquatic environment, and a very high activity for the RCM of diallylamine and diethyldiallylmalonate.