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Ahmed K. Aboul-gheit - One of the best experts on this subject based on the ideXlab platform.
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Sol-Gel and Thermally Evaporated Nanostructured Thin ZnO Films for Photocatalytic Degradation of Trichlorophenol.
Nanoscale Research Letters, 2009Co-Authors: Sawsan A. Mahmoud, Ahmed K. Aboul-gheitAbstract:In the present work, thermal evaporation and sol–gel coating techniques were applied to fabricate nanostructured thin ZnO films. The phase structure and surface morphology of the obtained films were investigated by X-ray diffractometer (XRD) and scanning electron microscope (SEM), respectively. The topography and 2D profile of the thin ZnO films prepared by both techniques were studied by optical profiler. The results revealed that the thermally evaporated thin film has a comparatively smoother surface of hexagonal wurtzite structure with grain size 12 nm and 51 m2/g. On the other hand, sol–gel films exhibited rough surface with a strong preferred orientation of 25 nm grain size and 27 m2/g surface area. Following deposition process, the obtained films were applied for the photodegradation of 2,4,6-trichlorophenol (TCP) in water in presence of UV irradiation. The concentrations of TCP and its intermediates produced in the solution during the photodegradation were determined by high performance liquid chromatography (HPLC) at defined irradiation times. Complete decay of TCP and its intermediates was observed after 60 min when the thermal evaporated photoCatalyst was applied. However, by operating sol–gel Catalyst, the concentration of intermediates initially increased and then remained constant with irradiation time. Although the degradation of TCP followed first-order kinetic for both Catalysts, higher photocatalytic activity was exhibited by the thermally evaporated ZnO thin film in comparison with sol–gel one.
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Sol–Gel and Thermally Evaporated Nanostructured Thin ZnO Films for Photocatalytic Degradation of Trichlorophenol
Nanoscale Research Letters, 2009Co-Authors: A. Abdel Aal, Sawsan A. Mahmoud, Ahmed K. Aboul-gheitAbstract:In the present work, thermal evaporation and sol–gel coating techniques were applied to fabricate nanostructured thin ZnO films. The phase structure and surface morphology of the obtained films were investigated by X-ray diffractometer (XRD) and scanning electron microscope (SEM), respectively. The topography and 2D profile of the thin ZnO films prepared by both techniques were studied by optical profiler. The results revealed that the thermally evaporated thin film has a comparatively smoother surface of hexagonal wurtzite structure with grain size 12 nm and 51 m^2/g. On the other hand, sol–gel films exhibited rough surface with a strong preferred orientation of 25 nm grain size and 27 m^2/g surface area. Following deposition process, the obtained films were applied for the photodegradation of 2,4,6-trichlorophenol (TCP) in water in presence of UV irradiation. The concentrations of TCP and its intermediates produced in the solution during the photodegradation were determined by high performance liquid chromatography (HPLC) at defined irradiation times. Complete decay of TCP and its intermediates was observed after 60 min when the thermal evaporated photoCatalyst was applied. However, by operating sol–gel Catalyst, the concentration of intermediates initially increased and then remained constant with irradiation time. Although the degradation of TCP followed first-order kinetic for both Catalysts, higher photocatalytic activity was exhibited by the thermally evaporated ZnO thin film in comparison with sol–gel one.
Ricardo Gómez - One of the best experts on this subject based on the ideXlab platform.
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Synthesis of Camphene by α-Pinene Isomerization Using W_2O_3–Al_2O_3 Catalysts
Topics in Catalysis, 2010Co-Authors: Francisco Tzompantzi, Manuel Valverde, Alejandro Pérez, José L. Rico, Angeles Mantilla, Ricardo GómezAbstract:W_2O_3–Al_2O_3 Catalysts prepared by “sol–gel” and impregnation methods were characterised by XRD, FTIR and nitrogen adsorption. Both Catalysts were tested in the isomerization of α-pinene in a batch reactor at atmospheric pressure and 150 °C. Conversion of α-pinene and selectivity to camphene was superior for the “sol–gel” Catalyst than that observed for the impregnated Catalyst.
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Synthesis of Camphene by α-Pinene Isomerization Using W2O3–Al2O3 Catalysts
Topics in Catalysis, 2010Co-Authors: Francisco Tzompantzi, Manuel Valverde, José L. Rico, Angeles Mantilla, Alejandro Díaz Pérez, Ricardo GómezAbstract:W2O3–Al2O3 Catalysts prepared by “sol–gel” and impregnation methods were characterised by XRD, FTIR and nitrogen adsorption. Both Catalysts were tested in the isomerization of α-pinene in a batch reactor at atmospheric pressure and 150 °C. Conversion of α-pinene and selectivity to camphene was superior for the “sol–gel” Catalyst than that observed for the impregnated Catalyst.
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Effect of sulfation methods on TiO2-SiO2 Sol-Gel Catalyst acidity
Applied Catalysis A: General, 2000Co-Authors: Tessy Lopez, Francisco Tzompantzi, Ricardo Gómez, Pedro Bosch, J. Navarrete, Esteban López-salinas, M.e. LlanosAbstract:A series of x TiO2‐SiO2 (xD1.7, 4.0 and 6.7 wt.% TiO2) binary mixed oxides was prepared by a sol‐gel method in acidic and basic conditions. In order to upgrade the acidic properties of the obtained solids, their sulfation was carried out in three different ways: (1) by in situ (H2SO4 was admixed with the gel), (2) impregnating the dried solids with aqueous solutions of H2SO4, and (3) by impregnating as in (2) but with (NH4)2SO4. FTIR-pyridine adsorption and benzene deuteroexchange showed that the acid site strength depends on the sulfation method. The highest values of total acidity, determined by ammonia thermodesorption, correspond to the in situ sulfated samples. The obtained pore size distribution (4.0‐5.0 nm) was narrow and the specific BET areas (250‐350 m 2 /g) were large. X-Ray diffraction, RDF, XPS spectroscopy and catalytic activity in the 2-butanol dehydration show that one step sulfated in situ TiO2‐SiO2 sol‐gel preparations resulted in Catalysts with homogeneous and strong acidity. © 2000 Elsevier Science B.V. All rights reserved.
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Novel Pt-Sn/Al2O3 Sol-Gel Catalyst: synthesis and thermal characterization
Materials Letters, 1994Co-Authors: Tessy Lopez, M. Asomoza, Ricardo GómezAbstract:Alumina supported platinum-tin Catalysts were synthesized using the Sol-Gel method. The solids were characterized by TGA and DTA analyses. It was found that the Catalysts remain hydroxylated after having been thermally stabilized. Moreover, when under a hydrogen flux, Pt reduces producing an intense exothermic peak at room temperature.
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Pt/SiO2 Catalysts: A comparison of the impregnation and the sol—gel methods
Journal of Molecular Catalysis, 1993Co-Authors: Pedro Bosch, Tessy Lopez, Victor-hugo Lara, Ricardo GómezAbstract:Abstract A comparative study of Pt/SiO2 Catalysts prepared by impregnation or by the sol—gel method is reported. The Catalysts were characterized by chemisorption, electron microscopy and X-ray diffraction studies. The results showed that metallic particles (35 A) in sol—gel Catalyst, are particles coming out from the support. These “emerged particles”, in phenylacetylene hydrogenation, act like ultrahighly dispersed particles.
Tessy Lopez - One of the best experts on this subject based on the ideXlab platform.
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Effect of sulfation methods on TiO2-SiO2 Sol-Gel Catalyst acidity
Applied Catalysis A: General, 2000Co-Authors: Tessy Lopez, Francisco Tzompantzi, Ricardo Gómez, Pedro Bosch, J. Navarrete, Esteban López-salinas, M.e. LlanosAbstract:A series of x TiO2‐SiO2 (xD1.7, 4.0 and 6.7 wt.% TiO2) binary mixed oxides was prepared by a sol‐gel method in acidic and basic conditions. In order to upgrade the acidic properties of the obtained solids, their sulfation was carried out in three different ways: (1) by in situ (H2SO4 was admixed with the gel), (2) impregnating the dried solids with aqueous solutions of H2SO4, and (3) by impregnating as in (2) but with (NH4)2SO4. FTIR-pyridine adsorption and benzene deuteroexchange showed that the acid site strength depends on the sulfation method. The highest values of total acidity, determined by ammonia thermodesorption, correspond to the in situ sulfated samples. The obtained pore size distribution (4.0‐5.0 nm) was narrow and the specific BET areas (250‐350 m 2 /g) were large. X-Ray diffraction, RDF, XPS spectroscopy and catalytic activity in the 2-butanol dehydration show that one step sulfated in situ TiO2‐SiO2 sol‐gel preparations resulted in Catalysts with homogeneous and strong acidity. © 2000 Elsevier Science B.V. All rights reserved.
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Novel Pt-Sn/Al2O3 Sol-Gel Catalyst: synthesis and thermal characterization
Materials Letters, 1994Co-Authors: Tessy Lopez, M. Asomoza, Ricardo GómezAbstract:Alumina supported platinum-tin Catalysts were synthesized using the Sol-Gel method. The solids were characterized by TGA and DTA analyses. It was found that the Catalysts remain hydroxylated after having been thermally stabilized. Moreover, when under a hydrogen flux, Pt reduces producing an intense exothermic peak at room temperature.
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Pt/SiO2 Catalysts: A comparison of the impregnation and the sol—gel methods
Journal of Molecular Catalysis, 1993Co-Authors: Pedro Bosch, Tessy Lopez, Victor-hugo Lara, Ricardo GómezAbstract:Abstract A comparative study of Pt/SiO2 Catalysts prepared by impregnation or by the sol—gel method is reported. The Catalysts were characterized by chemisorption, electron microscopy and X-ray diffraction studies. The results showed that metallic particles (35 A) in sol—gel Catalyst, are particles coming out from the support. These “emerged particles”, in phenylacetylene hydrogenation, act like ultrahighly dispersed particles.
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Sol-Gel Ru/SiO2-Catalysts: Theoretical and Experimental Determination of the Ru-in-Silica Structures
Journal of Catalysis, 1993Co-Authors: Tessy Lopez, S. Castillo, Rosa María Gómez, Octavio Novaro, Alejandro Ramírez-solís, E. Sánchez-mora, E. Poulain, José Manuel Martínez-magadánAbstract:Preparation of Ru/SiO[sub 2] Catalysts with Sol-Gel techniques allows better selectivity and much greater resistance to coke formation and deactivation than the traditional impregnation method. This has been attributed to the incorporation of Ru into the silica network for the Sol-Gel Catalyst. To further understand the structure of the Ru occluded in the silica network, a variety of spectroscopical studies and quantum mechanical calculations were carried out, confirming previously proposed structures and showing good agreement between the theoretical and experimental results. 26 refs., 10 figs., 2 tabs.
Dmitry Yu. Murzin - One of the best experts on this subject based on the ideXlab platform.
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Liquid-Phase Hydrogenation of Cinnamaldehyde over a Ru−Sn Sol−Gel Catalyst. 1. Evaluation of Mass Transfer via a Combined Experimental/Theoretical Approach
Industrial & Engineering Chemistry Research, 2004Co-Authors: Jan Hájek, Dmitry Yu. MurzinAbstract:Hydrogenation of cinnamaldehyde over a 5% Ru−5% Sn/SiO2 sol−gel Catalyst was investigated in a stirred batch reactor. A combined experimental/theoretical approach was used to elucidate the impact o...
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Liquid-Phase Hydrogenation of Cinnamaldehyde over a Ru−Sn Sol−Gel Catalyst. 2. Kinetic Modeling
Industrial & Engineering Chemistry Research, 2004Co-Authors: Jan Hájek, Johan Wärnå, Dmitry Yu. MurzinAbstract:Selective liquid-phase hydrogenation of cinnamaldehyde to cinnamyl alcohol over a sol−gel 5% Ru−5% Sn/SiO2 Catalyst has been studied in a stirred batch reactor (373−483 K, 25−70 bar). Experiments provided information about the influence of temperature and pressure on the catalytic performance. The Catalyst deactivation in different solvents during repeated experiments has been studied, too. Kinetic modeling based on several reaction mechanisms allowing discrimination between rival models was carried out.
Kimio Kunimori - One of the best experts on this subject based on the ideXlab platform.
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Preparation of highly dispersed silica-supported palladium Catalysts by a complexing agent-assisted Sol-Gel method and their characteristics
Applied Catalysis A-general, 2002Co-Authors: S. Tanaka, Fujio Mizukami, Shuichi Niwa, Makoto Toba, Kazuyuki Maeda, Hiromichi Shimada, Kimio KunimoriAbstract:Abstract Pd/SiO2 Catalysts were prepared by a complexing agent-assisted sol–gel method, and impregnation methods using an organic complexing agent (imp-org) or water (imp-w) as the impregnation solvent. The Pd/SiO2 Catalysts were characterized by TG-DTA, Fourier transform-infrared (FT-IR) spectroscopy, 13 C NMR, X-ray powder diffraction (XRD), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and CO adsorption, and the difference between the preparation methods was discussed. The sol–gel Catalysts usually contained some organics after the heat treatment in hydrogen. Moreover, it was found that trace amounts of organics remain even in the sol–gel Catalyst activated at 873 K in hydrogen. In the sol–gel Catalyst at 673 K in hydrogen, the palladium was somewhat positively charged. On the other hand, the palladium in the sol–gel Catalyst activated at 873 K and both impregnation Catalysts activated at 673 K in hydrogen were completely metallic. The palladium particles in the sol–gel Catalysts were much smaller and more uniform in size than those in the corresponding impregnation Catalysts. Furthermore, on the TEM images, the metal particles in the sol–gel Catalysts in comparison with those in both impregnation ones seemed to be somewhat covered with the silica or embedded in the silica. Reflecting this, with an increase in the activation temperature, the particles did not grow in size as rapidly in the sol–gel Catalysts as in both impregnation ones.
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Highly selective formation of aldehydes in the hydrogenation of the corresponding acid chlorides with silica-supported palladium Catalysts prepared by a complexing agent-assisted sol–gel method
Applied Catalysis A-general, 2002Co-Authors: S. Tanaka, Fujio Mizukami, Shuichi Niwa, Makoto Toba, Gy. Tasi, Kimio KunimoriAbstract:Abstract Synthesis of aldehydes from acid chlorides was carried out using four types of supported Pd/SiO 2 Catalysts, which were prepared by a complexing agent-assisted sol–gel method and two types of impregnations with organic solvents or water, and a commercial Pd/BaSO 4 Catalyst. The performance of the Catalysts was much affected by the Catalyst preparation and activation conditions. The sol–gel Catalysts activated under milder conditions exhibited the highest performance for the formation of aldehydes. The high performance of the sol–gel Catalysts was due to the organic residues derived from acetylacetone and ethylene glycol used in the sol–gel Catalyst preparation process. The organic residues play a role similar to that of a poison added into the reaction solution for the traditional Rosenmund reduction, while being kept in the silica gel matrices.