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Abstract

The hydrogenation of biomass-derived ethyl lactate was studied over several ruthenium catalysts (Ru/TiO2, Ru/SiO2, Ru/γ-Al2O3, Ru/NaY and Ru/C), with the intent of developing a simple and additive-free catalytic system. The catalytic performance is dependent on the nature of the support. Ru/SiO2 was found to be an efficient catalyst for the hydrogenation of ethyl lactate to 1,2-propanediol (1,2-PDO). Parametric studies show that the reaction temperature, hydrogen pressure and catalyst amount can significantly influence the catalytic performance. Under optimal reaction conditions (433 K, 5 MPa), high yield of 1,2-PDO (82.1%) was obtained without the introduction of any additives. Form a practical point of view, this study may open the way to a new approach for the production of 1,2-PDO.

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In this study, nano-γ-alumina-supported unsubstituted Fe-, Co- and Mn-phthalocyanines were prepared and characterized. Catalytic activities of the supported phthalocyanines for the oxidation of cyclohexane with tert-butylhydroperoxide (TBHP) and H2O2 as the oxidant in the liquid phase were considered. For the MPc/nano-γ-alumina catalysts, a dimethylformamide:dichloromethane (3:7) solvent mixture was employed. The products of the catalytic reaction are cyclohexanone and cyclohexanol. The conversion percent of cyclohexane depended on the oxidant and the catalyst. TBHP was found to be a better oxidant than H2O2 since minimal destruction of the catalyst and higher conversion of cyclohexane were observed when this oxidant was employed. Under these reaction conditions, the order of catalytic activities is as follows: CoPc/γ-alumina > FePc/γ-alumina > MnPc/γ-alumina. Over γ-alumina, the conversion was much lower than on supported catalysts. The highest conversion of cyclohexane (13.21%) was observed on 10% CoPc supported.

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Abstract

Photocatalysis is often used for the decomposition of organic compounds in water, e.g., for dye decomposition. There are many problems with calculating the photocatalytic activity of photocatalysts during dye decomposition, especially in the case of photocatalysts with a high adsorption capacity because it is difficult to say whether a dye is photocatalytically decomposed or whether it is only adsorbed on photocatalyst surface. In both cases, the dye disappears from the water, but the optimal situation is when the dye is both adsorbed and decomposed on photocatalyst surface. Moreover, it is problematic to compare the photocatalytic activity of different photocatalysts when they have strong adsorption capacity. In this study a new method of measuring photocatalytic activity of photocatalysts with high adsorption capacity is presented. Reactive Red (monoazo) and Direct Green (poliazo) dyes were used to determine adsorption capacity and photocatalytic activity of commercial TiO2 Degussa P25, anatase TiO2 and carbon modified anatase TiO2.

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In this study, the preparation of titania dip-coated thin films on glazed porcelain substrates via the sol–gel process was investigated. The crystal structure and morphology of the dip-coated thin films were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The surface topography of the thin films was examined by atomic force microscope (AFM). Photocatalytic properties of the titania thin films were investigated by the degradation of methylene blue (MB). XRD patterns showed an increase in peak intensities of the crystalline phase by increasing the calcination temperature. The thickness of the thin film was less than 1 μm. The AFM image indicates that the surface morphology of the films is granular with about 50 nm average grain size. Higher photocatalytic activity of titania thin films was measured in the samples calcined at 400 °C.

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Abstract

Platinum catalysts supported on silicas with various physicochemical properties were prepared in order to investigate the effect of silica characteristics on their platinum dispersion and catalytic activity in the oxidation of carbon monoxide. Although titania-incorporation into silica and further treatment of the impregnated platinum precursor with hydrogen peroxide were effective for improving the dispersion and stability of platinum catalysts supported on silicas, regardless of the characteristic of the silicas, the platinum catalysts supported on fumed silica with a medium level of surface hydroxyl group concentration exhibited the highest catalytic activity among those supported on mesoporous silica, silica gel, and precipitated silica. The required properties of the highly active platinum catalyst seemed to be a high dispersion of platinum, the formation of a stable titania layer, and the generation of strong acid sites. By contrast, the precipitated silica with a small surface area and high concentration of surface hydroxyl groups was not appropriate for a catalytic support for platinum catalysts.

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Abstract

The N-alkylation of morpholine with alcohols in gas–solid phase was investigated in a fixed-bed reactor over CuO–NiO/γ–Al2O3 catalyst prepared by the impregnation method. The N-methylation of morpholine with methanol gave a 95.3% conversion with a 93.8% selectivity of N-methylmorpholine under the optimum reaction condition, and the corresponding apparent activation energy is 46.20 kJ mol−1. The present catalytic system is also applicable to other low-carbon primary alcohols. However, secondary alcohols enjoy relatively low product selectivity for the resulting ketone is a poorer electrophile than an aldehyde. For cyclohexanol, the low conversion and selectivity are mainly due to steric effects. The catalyst shows a high catalytic activity without obvious fluctuation during a long period of 120 h.

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Abstract

The heterogeneous catalytic oxidation of volatile organic compounds on Pd/CexLa1−xO2/monolith catalysts in the temperature range 160–230 °C has been studied, which took toluene combustion as a probe reaction. SEM, ICP-OES, XRD, laser Raman spectra, and temperature-programmed reduction (TPR) are used to characterize the Pd/CexLa1−xO2/monolith catalysts. A high activity of the catalyst with respect to the complete oxidation of toluene to carbon dioxide has been observed. The conversion of toluene approaches 100% at about 210 °C.

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Abstract

A heterogeneous photo-Fenton catalyst was prepared using the complex tris(1,10)-phenanthroline iron(II) loaded on the NaY type of zeolite. The catalyst displayed a feature of the photo-Fenton degradation of methylene blue, and a linear relationship between ln(C0/Ct) and reaction time was obtained, indicating the kinetic characteristics of a pseudo first-order reaction. The repeated cyclic experiments showed that the heterogeneous catalyst was stable and recoverable. Compared with the traditional homogeneous Fenton reagent, the heterogeneous catalyst has the advantage in the neutral or weakly basic medium used because the active component tris(1,10)-phenanthroline iron(II) is a stable chelate compound. The photo-Fenton degradation pathway for methylene blue was given based on the mass spectral data.

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Abstract

The influence of support porosity on the selectivity of home-made 5%Pd–2%In/support (support = SiO2, Al2O3, TiO2) catalysts in nitrate reduction was studied. The main final products of the reaction were N2 and NH4 +. Together with the decrease in pore diameter, an increase in ammonia concentration in the reaction mixture was observed. It is probably caused by slow diffusion of OH ions from narrow pores to the solution.

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Abstract

The enantio-differentiating hydrogenation of methyl acetoacetate was carried out over a (R,R)-tartaric acid-NaBr-modified Raney nickel catalyst under low hydrogen pressure. The rate of the supply of hydrogen on the catalyst surface would be an important factor for attaining high enantioselectivity, especially under low hydrogen pressure. A maximum enantioselectivity of 82% was attained under an initial hydrogen pressure of 0.2 MPa at 333 K with a high stirring rate.

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