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Abstract

Cu(II) tetradentate Schiff base complexes of N,N′-(bis(pyridin-2-yl)formylidene)ethane-1,2-diamine (pfed), N,N′-(bis(pyridin-2-yl)formylidene)propane-1,3-diamine (pfpd), N,N′-(bis(pyridin-2-yl)formylidene)benzene-1,2-diamine (pfbd), N,N′-(bis(pyridin-2-yl)formylidene)cycohexane-1,2-diamine (pfcd) and N,N′-(bis(pyridin-2yl)formylidene)meso-stilben-1,2-diamine (pfmd) were synthesized, characterized and immobilized on sodium montmorillonite. These catalysts were characterized by X-ray diffraction, IR spectroscopy, diffuse reflectance spectra (DRS) and atomic absorption spectroscopy. The IR and DRS data of the heterogeneous catalysts show that copper(II) complexes were physically entrapped within sodium montmorillonite. The basal spacing (d001) of heterogeneous catalysts indicates that Cu(II) Schiff base complexes were fixed in the axial direction into the interlayer of montmorillonite. All new heterogeneous catalysts show excellent catalytic activity in the epoxidation of cyclooctene using tert-butylhydroperoxide in acetonitrile. The supported [Cu(pfed)] exhibited a moderate 74 % selectivity for epoxidation with 76 % conversion. The catalytic activity and selectivity of heterogeneous catalysts have not changed after three times of reusing.

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Abstract

A new composite catalytic system of Pd/C, 2,4,6-trichloro-[1,3,5]-triazine and N,N-dimethylformamide was investigated in nitrocyclohexane hydrogenation to ∊-caprolactam. The Pd/C catalyst was prepared by the incipient impregnation method and characterized by BET, N2 adsorption–desorption, XRD, TEM and H2 chemisorption. The results indicate that 2,4,6-trichloro-[1,3,5]-triazine plays a key role in one step synthesis of ∊-caprolactam from nitrocyclohexane hydrogenation. Besides ∊-caprolactam, the products include cyclohexanone oxime, cyclohexamine, cyclohexanone and cyclohexanol. A possible mechanism for nitrocyclohexane hydrogenation in 2,4,6-trichloro-[1,3,5]-triazine and N,N-dimethylformamide complex was proposed.

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Reaction Kinetics, Mechanisms and Catalysis
Authors: A. Martínez-de la Cruz, D. B. Hernández-Uresti, Leticia M. Torres-Martínez, and S. W. Lee

Abstract

PbMoO4 oxide with scheelite structure was obtained by hydrothermal synthesis in the absence of additives. The material was characterized by X-ray powder diffraction, scanning electron microscopy, diffuse reflectance spectroscopy, and adsorption–desorption N2 isotherms. The organic dyes rhodamine B (rhB), indigo carmine (IC), orange G (OG), and methyl orange (MO) were selected as molecules model to study its photocatalytic degradation over PbMoO4 oxide under UV irradiation. Total organic carbon analysis of samples irradiated revealed that mineralization of organic dyes by the action of PbMoO4 was feasible in 80 % (rhB), 69 % (IC), 71 % (MO), and 65 % (OG) after 96 h of UV irradiation.

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Abstract

The electron transfer (ET) reaction between benzylthioacetic acid (BTAA) and tris(1,10-phenanthroline)iron(III) perchlorate resulted in the formation of benzylsulfinylacetic acid. The reaction is first order with respect to both BTAA and [Fe(phen)3]3+ and is retarded by hydrogen ion. The ET reaction is studied in 50 % aqueous methanol medium. The Marcus theory is successfully applied to the present redox system and this supports the operation of single electron transfer in the rate controlling step of the reaction.

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Abstract

Fe3O4 nanoparticles were prepared and modified with (3-aminopropyl) trimethoxysilane (APTMS) followed by complexation with Co(acac)2. The prepared nanocatalyst, designated as Fe3O4@APTMS@Co(acac)2 was characterized by FTIR, XRD, SEM, and TEM techniques. It was found that Fe3O4@APTMS@Co(acac)2 successfully catalyzes the epoxidation of cyclooctene, styrene, cyxlohexene, trans-stilbene, and norbornene with O2 as an oxidant and isobutyraldehyde (RCHO) as a co-reductant with 48–100 % reactivity and 40–92 % selectivity.

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Abstract

Preferential oxidation of CO (CO-PROX) was carried out over Ni supported on CeO2 prepared by the co-precipitation method. The influence of metal loadings (2.5, 5 and 10 wt.% Ni) and the reaction conditions such as reaction temperature and feed composition on CO oxidation and oxidation selectivity were evaluated by using dry reformate gas. No other reactions like CO or CO2 methanation, coking, reverse water gas shift (RWGS) reaction is observed in the temperature range of 100–200 °C on these catalysts. Hydrogen oxidation dominates over CO oxidation above the temperature of 200 °C. An increase in oxygen leads to an increase in CO conversion but a simultaneous decrease in the O2 selectivity. It has been noticed that 5 and 10 % Ni/CeO2 show better catalytic activity towards CO-PROX reaction. These catalysts were characterized by SBET, XRD, TEM, XPS and H2-TPR.

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Reaction Kinetics, Mechanisms and Catalysis
Authors: Susana Pinto-Castilla, Santiago Marrero, Yraida Díaz, Joaquín L. Brito, Pedro Silva, and Paulino Betancourt

Abstract

A novel synthesis route was designed to obtain highly active vanadium based catalysts. Three different activated carbons were used as supports (one of them being treated with ozone). The supported catalysts were characterized by XRD, TEM, XPS and EPR. These systems were tested in hydrotreating reactions (HDS, HDN and hydrogenation). The characterization results showed well dispersed vanadium nanoparticles. However, it was evidenced that during the synthesis process, a vanadium carbide phase was produced within vanadium oxides. Reactivity studies showed that the vanadium catalysts were slightly better for HDS and hydrogenation reactions than a commercial NiMoS catalyst, but that was not the case for HDN reactions. The reduction method proposed is potentially an excellent route to synthesize more active supported vanadium carbide catalysts than the conventional TPS method. Under reaction conditions, carbide and sulfide vanadium species coexist in the catalyst; vanadium carbide sites probably remain intimately mixed with the active vanadium sulfide sites.

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Abstract

In this work, a new approach was proposed to get glycerophosphocholine (GPC) from natural soybean lecithin catalyzed by the quaternary ammonium base resin made in our laboratory. The results showed that the resin has the potential for preparing GPC under mild conditions, and the catalyst could be easily separated and recycled with stable catalytic activity. The effects of different parameters on the rate of reaction verified that the transesterification was intrinsically kinetically controlled and there were no external and internal mass transfer resistance. The results showed that when the reaction was carried out with agitation speed of 675 rpm, reaction temperature of 50 °C, catalyst loading of 80 g L−1, the lecithin conversion was 98 % after 3.5 h. A kinetic model was developed and the experimental data fitted it well, and the mechanism of methanolysis of natural lecithin catalyzed by resin was proposed.

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Abstract

The kinetics of the reduction of nickel, cobalt and copper ferrites was studied by the temperature programmed reduction method at different heating rates in hydrogen atmosphere. The activation energy values of the reduction processes were calculated using the non-isothermal isoconversional method according to the Kissinger-Akahira-Sunose equation and the dependence of apparent activation energy on the degree of conversion was determined. The carbon monoxide oxidation activities of all the three samples were determined at various temperatures up to 140 °C. An interesting correlation between the apparent activation energies for the reduction process was observed. The decreasing trend of activation energy on the ‘extent of conversion’ in all cases showed that the reduction is a multi-step process involving a reversible process followed by an irreversible step.

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Abstract

A fast, economic, and green synthesis of benzimidazole derivatives using iron oxide modified sepiolite (IMS) as a catalyst has been reported. IMS showed excellent catalytic properties and the reactions completed within 20–30 min to give products in high yield. The adsorption mechanism of formic acid on IMS was studied by infrared (IR) spectroscopy at temperature range 120–400 °C. Thermal desorption of pyridine was followed by IR and thermal analysis techniques to estimate the acidity of IMS. Lewis acid-bound pyridine bands at 1,618–1,631 and 1,443–1,445 cm−1 were observed even after IMS sample were heated above 400 °C.

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