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1.
Synthesis of Thermally Stable χ-Alumina by Thermal Decomposition of Aluminum Isopropoxide in Toluene
Okorn Mekasuwandumrong Hiroshi Kominami Piyasan Praserthdam Masashi Inoue 《Journal of the American Ceramic Society》2004,87(8):1543-1549
Thermal decomposition of aluminum isopropoxide in toluene at 315°C resulted in χ-alumina that had high thermal stability, whereas the reaction at lower temperatures resulted in formation of an amorphous product. The χ-alumina thus obtained directly transformed to α-alumina at ∼1150°C, bypassing the other transition alumina phases, whereas the amorphous product transformed to γ-alumina and then to θ-alumina before final transformation to α-alumina. When the χ-alumina, solvothermally synthesized at 315°C, was recovered by the removal of the solvent at the reaction temperature, thermal stability of the product was improved further. This procedure is convenient because it avoids bothersome work-up processes that yield large-surface-area and large-pore-volume alumina. 相似文献
2.
Ag-ZnO catalysts for UV-photodegradation of methylene blue 总被引:3,自引:0,他引:3
Murray J. Height Sotiris E. Pratsinis Okorn Mekasuwandumrong Piyasan Praserthdam 《Applied catalysis. B, Environmental》2006,63(3-4):305-312
High surface area Ag-ZnO catalysts have been made by flame spray pyrolysis (FSP) and characterized by X-ray diffraction (XRD), nitrogen adsorption, UV–vis spectroscopy and electron microscopy (SEM and transmission electron microscopy (TEM)) combined with energy dispersive X-ray spectroscopy (EDXS) for elemental mapping. Silver metal clusters deposited directly on ZnO nanocrystals were obtained from this process. The Ag loading (1–5 at.%) controlled the Ag cluster size from 5 to 25 nm but did not influence the ZnO crystal size. Photodegradation of 10 ppm methylene blue (MB) solution was used to evaluate the performance of these FSP-made Ag-ZnO and was compared to wet-made Ag-ZnO and reference titania photocatalysts. The rate of photodegradation was optimal for Ag loading around 3 at.%. The best photocatalytic performance was exhibited by flame-made Ag-ZnO produced at the longest high-temperature residence times having high crystallinity as determined by XRD and UV–vis. 相似文献
3.
O. Mekasuwandumrong P. Praserthdam M. Inoue V. Pavarajarn W. Tanakulrungsank 《Journal of Materials Science》2004,39(7):2417-2421
Thermal decomposition of aluminum isopropoxide (AIP) in inert organic solvents (toluene and mineral oil) resulted in the formation of -alumina. Phase evolution by calcination at various temperatures for this alumina was studied via X-ray diffraction. The results suggest a direct transformation from -alumina to -alumina at approximately 1180°C, without the formation of -alumina phase, while still maintaining the small particle size (<100 nm). The transformation behavior was observed by TEM and the crytallite size was calculated by the Scherrer equation. The results indicate one -alumina crystal transforms into one -alumina crystal at its critical size in a nucleation step. This crystal exhibits a rapid grain growth following the transformation. 相似文献
4.
Waraporn Chatpaisalsakul Okorn Mekasuwandumrong Joongjai Panpranot Chairit Satayaprasert Piyasan Praserthdam 《Journal of Industrial and Engineering Chemistry》2009,15(1):77-81
Nanocrystalline titania was prepared by solvothermal reaction of titanium butoxide in toluene at 300 °C for 2 h. Thus obtained-powder was calcined at 300 °C in box furnace for 1 h and then quenched in various media at different temperature. The physiochemical properties of samples were investigated by using X-ray diffraction (XRD), nitrogen adsorption, CO2-Temperature Programmed Desorption (CO2-TPD), UV–visible scanning spectrophotometer, Transmission electron microscopy (TEM) and electron spin resonance spectroscopy (ESR) techniques. All physical properties such as phase, BET surface area and crystal size were not changed after quenching processes. While the CO2-TPD and ESR results indicate the changing of Ti3+ contents on the surface of TiO2 after quenching process. The amounts of Ti3+ increased as the quenching temperature decreased. Photocatalytic decomposition of water was carried out to evaluate the catalytic activity of quenched TiO2. The activity of quenched-powder increased corresponding to the increasing of Ti3+ contents increased by following order: air at 77 K > air at RT > air at 373 K > 30 wt% H2O2 at RT = 30 wt% H2O2 at 373 K > H2O at RT > H2O at 373 K. 相似文献
5.
Okorn Mekasuwandumrong Nitikon Wongwaranon Joongjai Panpranot Piyasan Praserthdam 《Materials Chemistry and Physics》2008,111(2-3):431-437
In the present study, Ni-modified α-Al2O3 with Ni/Al ratios of 0.3 and 0.5 were prepared by sol–gel and solvothermal method and then were impregnated with 0.3 wt.% Pd. Due to different crystallization mechanism of the two preparation methods used, addition of nickel during preparation of α-Al2O3 resulted in various species such as NiAl2O4, mixed phases between NiAl2O4 and α-Al2O3, and mixed phases between NiAl2O4 and NiO. As revealed by NH3-temperature programmed desorption, formation of NiAl2O4 drastically reduced acidity of alumina, hence lower amounts of coke deposited during acetylene hydrogenation was found for the Ni-modified α-Al2O3 supported catalysts. For any given method, ethylene selectivity was improved in the order of Pd/Ni–Al2O3-0.5 > Pd/Ni–Al2O3-0.3 > Pd/Ni–Al2O3-0 Pd/α–Al2O3-commercial. When comparing the samples prepared by different techniques, the sol–gel-made samples showed better performances than the solvothermal-derived ones. 相似文献
6.
Parawee Tonto Okorn Mekasuwandumrong Suphot Phatanasri Varong Pavarajarn Piyasan Praserthdam 《Ceramics International》2008
Solvothermal reaction of zinc acetate in various alcohols resulted in the formation of zinc oxide (ZnO) nanorods. The effects of reaction conditions on the product morphology as well as crystallization mechanism were investigated by using X-ray diffraction (XRD), infrared spectroscopy (IR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and transmission electron microscopy (TEM) techniques. It was found that average diameter and length of the nanorods increased with an increase in reaction temperature or the initial concentration of zinc acetate. On the contrary, the aspect ratio of the product depended upon type of alcohol used as the reaction medium. The aspect ratio of ZnO nanorods increased from 1.7 to 5.6 when the alcohol was changed from 1-butanol to 1-decanol. An investigation of the reaction mechanism suggested that the formation of ZnO nanorods was initiated from the esterification reaction between zinc acetate precursor and alcohol to form ZnO seeds. 相似文献
7.
Terachai Sirikajorn Okorn Mekasuwandumrong Piyasan Praserthdam James G. Goodwin Jr. Joongjai Panpranot 《Catalysis Letters》2008,126(3-4):313-318
The catalytic activity and deactivation of nanocrystalline ZnAl2O4-supported Pd catalysts were investigated for the liquid-phase hydrogenation under mild conditions. Nanocrystalline ZnAl2O4 spinels with average crystallite size between 8 and 33 nm were synthesized by the solvothermal method in toluene. Higher turnover frequencies for 1-heptyne hydrogenation and less deactivation due to Pd leaching were obtained for the Pd/ZnAl2O4-33 nm catalyst. XPS and ESR results suggest that the presence of defects in larger crystallite size ZnAl2O4 resulted in higher Pd dispersion and stronger interaction between Pd and the support. 相似文献
8.
Chayanin Na-Chiangmai Napaporn Tiengchad Prathan Kittisakmontree Okorn Mekasuwandumrong Jonathan Powell Joongjai Panpranot 《Catalysis Letters》2011,141(8):1149-1155
Abstract
An ultra-large pore mesocellular foam silica (MCF) was employed as a support for preparation of supported Pd catalysts for the liquid-phase selective hydrogenation of phenylacetylene. The catalysts were prepared by three different routes: (i) incipient wetness impregnation using Pd(II)acetate solution (Pd/MCF-imp), (ii) impregnation of colloidal Pd nanoparticles obtained by the solvent reduction method (Pd/MCF-col), and (iii) in situ synthesis of MCF in the presence of the Pd colloid (Pd/MCF-ss). The conventional impregnation method resulted in more agglomeration of Pd particles and partial collapse of MCF structure, hence the Pd/MCF-imp exhibited the lowest selectivity towards styrene at total conversion of phenylacetylene. Only the Pd/MCF-ss, in which most of the Pd nanoparticles were encapsulated by the silica matrix, was found to retain high styrene selectivity (>80%) after complete conversion of phenylacetylene. Comparing to the other highly efficient Pd catalysts reported in the literature under similar reaction conditions, it can be emphasized that coverage of Pd surface by the support produces great beneficial effect for enhancing styrene selectivity, regardless of the type of supports used (i.e., TiO2, carbon nanotubes, or mesostructured silica). 相似文献9.
Cunningham Christopher L.; Dickinson Shelly D.; Okorn Dobrina M. 《Canadian Metallurgical Quarterly》1995,3(4):330
Mice (DBA/2J) received a Pavlovian procedure in which a distinctive floor stimulus was paired 4 times with ethanol (2 g/kg). A different floor stimulus was paired with saline. Naloxone (0.0, 1.5, or 10.0 mg/kg, intraperitoneal) given before each ethanol trial did not interfere with acquisition of conditioned preference, although naloxone alone produced conditioned aversion. When naloxone (0.0, 0.15, 1.5, 3.0, or 10.0 mg/kg) was given for the first time during testing, mice showed conditioned preference during the first 10 min. However, preference subsequently decreased dose-dependently over time. Control studies eliminated alternative interpretations based on pharmacokinetics or presence of an aversive state. The overall pattern of results suggests that naloxone facilitated extinction of conditioned place preference and supports the hypothesis that ethanol-induced conditioned reinforcement is mediated by the endogenous opioid system. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
10.
Sirima Somboonthanakij Okorn Mekasuwandumrong Joongjai Panpranot Tarit Nimmanwudtipong Reto Strobel Sotiris E. Pratsinis Piyasan Praserthdam 《Catalysis Letters》2007,119(3-4):346-352
In this study, Pd/SiO2 catalysts with 0.5–10 wt.% Pd loadings were prepared by one-step flame spray pyrolysis (FSP) and characterized by N2 physisorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), CO chemisorption, and X-ray photoelectron
spectroscopy (XPS). The average cluster/particles size of Pd as revealed by TEM were ca. 0.5–3 nm. The turnover frequencies (TOFs) of the flame-made catalysts decreased from 66.2 to 4.3 per s as Pd loading increased
from 0.5 to 10 wt.%, suggesting that the catalytic activity was dependent on Pd particle/cluster size. However, there were
no appreciable influences on 1-heptene selectivity. The flame-made Pd/SiO2 showed better properties than the conventional prepared catalysts. Their advantages are not only the presence of large pores
that facilitates diffusion of the reactants and products, but also the high-catalytic activity of as-synthesized catalysts
so that further pretreatment is not necessary. 相似文献