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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.
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
4.
Joongjai Panpranot Surajee Kaewkun Piyasan Praserthdam James G. Goodwin Jr. 《Catalysis Letters》2003,90(1-2):95-102
The photocatalytic activity of titanium dioxide supported on zeolites HZSM-5, HY and H was evaluated for a novel intermolecular cyclization of ethylenediamine with propylene glycol leading to dihydropyrazine. Titanium dioxide supported on zeolites has been prepared with 2 and 5 wt% of TiO2 by solid-state reaction, impregnation and sol impregnation methods. From the characterization by XRD, BET, EDAX and TPD of NH3, it is deduced that in all cases titanium dioxide is in small particles of anatase on zeolites. The highest photocatalytic activity was obtained with 2 wt% TiO2/H prepared by solid-state reaction. The acidity determined by TPD of NH3 was found to be lower for TiO2/H than for TiO2/HZSM-5 and TiO2/HY. From the above observations, it can be concluded that adsorption, acidity and structure of zeolites have an influence on the activity of supported TiO2. 相似文献
5.
The effects of an anionic surfactant on the dispersion of carbon black (CB) for the purpose of forming conducting composite films were examined with ultraviolet–visible (UV–vis) absorption spectroscopy. To obtain a good dispersion and size reduction of aggregated CB in a polymer matrix, sodium dodecyl sulfate (SDS), used as a surfactant, was introduced into a CB suspension. A set of concentrations with various ratios of CB to SDS (ranging from 1 : 0.4 to 1 : 10) was established before mixing with poly(amic acid) (PAA), a precursor of pyromellitic dianhydride and oxydianiline, was performed. The CB/PAA solution mixtures were submerged under an ultrasonic bath for several hours, then cast onto dry plate glasses, and finally subjected to thermal imidization to produce CB/polyimide (PI) nanocomposite films with various CB weight fractions ranging from 0.025 to 0.50 wt %. A method for evaluating the absorbance at 500 nm of the CB/PI nanocomposite films was established. The absorbance of CB/PI nanocomposite samples of various thicknesses was also normalized to get rid of the effects of the different thicknesses. UV–vis spectra showed that the minimum weight ratio of CB to SDS in the nanocomposite films that achieved well‐dispersed CB and still had transparent properties was 1 : 2.0. Transmission electron microscopy demonstrated that CB was dispersed homogeneously in the PI matrix, and the size of the aggregated CB was affected by the amount of the surfactant. The dielectric properties of the nanocomposite films without the surfactant increased by approximately 2 orders of magnitude with an increasing mass weight fraction of CB and decreased when the surfactant was added. The surfactant also reduced the tensile strength of the CB/PI nanocomposites when the CB/SDS ratio was higher than 1 : 2.0. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
6.
Nicha Tangchupong Bunjerd Jongsomjit Piyasan Praserthdam 《Fuel Processing Technology》2010,91(1):121-126
The effect of catalyst calcination temperature (450 °C, 600 °C, and 750 °C) on catalytic performance of synthesized and commercial grade sulfated zirconia catalysts towards isosynthesis was studied. The characteristics of these catalysts were determined by using various techniques including BET surface area, XRD, NH3- and CO2-TPD, ESR, and XPS in order to relate the catalytic reactivity with their physical, chemical, and surface properties. It was found that, for both synthesized and commercial sulfated zirconia catalysts, the increase of calcination temperature resulted in the increase of monoclinic phase in sulfated zirconia, and the decrease of acid sites. According to the catalytic reactivity, at high calcination temperature, lower CO conversion, but higher isobutene production selectivity was observed from commercial sulfated zirconia. As for synthesized sulfated zirconia, the isobutene production selectivity slightly decreased with increasing calcination temperature, whereas the CO conversion was maximized at the calcination temperature of 600 °C. We concluded from the study that the difference in the calcination temperatures influenced the catalytic performance, sulfur content, specific surface area, phase composition, the relative intensity of Zr3+, and acid-base properties of the catalysts. 相似文献
7.
Watcharapong Khaodee Nicha Tangchupong Bunjerd Jongsomjit Navadol Laosiripojana Piyasan Praserthdam Suttichai Assabumrungrat 《Journal of Industrial and Engineering Chemistry》2010,16(3):411-418
Catalytic performances of sulfated zirconia catalysts with various contents of sulfur (from 0.1 to 0.75%) on isosynthesis were studied. It was firstly found that undoped-zirconia synthesized from zirconyl nitrate provided higher activity towards isosynthesis reaction (106 μmol kg-cat?1 s?1) compared to that synthesized from zirconyl chloride (84.9 μmol kg-cat?1 s?1). Nevertheless, the selectivity of isobutene in hydrocarbons was relatively lower. It was then observed that the catalytic reactivity and selectivity significantly improved by sulfur loading. The most suitable sulfur loading content seems to be at 0.1%, which gave the highest reaction rate and selectivity of isobutene. By applying several characterization techniques, i.e. BET, XRD, NH3- and CO2-TPD and SEM, it was revealed that the high reaction rate and selectivity towards isosynthesis reaction of sulfated zirconia catalysts are related to the acid–base properties, Zr3+ quantity and phase composition. 相似文献
8.
Ekrachan Chaichana Supaporn Khaubunsongserm Piyasan Praserthdam Bunjerd Jongsomjit 《Polymer Bulletin》2011,66(9):1301-1312
Copolymerization of ethylene and 1-hexene for obtaining the linear low-density polyethylene was conducted along with silicas
as supports for [t-BuNSiMe2Flu]TiMe2/MMAO catalyst. Two silicas with different pore sizes were used to investigate the effect of pore sizes on copolymerization.
In addition, gallium was also introduced into both silicas to improve their properties and enhance the catalytic activities
of the system. It was found that before modification, the larger pore silica exhibited higher catalytic activity than the
smaller one due to low internal diffusion resistance. After modification, both silicas exhibited higher catalytic activity
comparing to their pristine condition. However, 1-hexene incorporation in the obtained copolymers was lower. The reduced surface
area of silica after modification was the main reason for the decrease in 1-hexene incorporation. The properties of the copolymers
by means of differential scanning calorimetry, gel permeation chromatography, and 13C NMR spectroscopy were further discussed in more detail. 相似文献
9.
Assabumrungrat Suttichai Wongwattanasate Darin Pavarajarn Varong Praserthdam Piyasan Arpornwichanop Amornchai Goto Shigeo 《Korean Journal of Chemical Engineering》2004,21(6):1139-1146
The synthesis of ethyl tert-butyl ether (ETBE) from a liquid phase reaction between tert-butyl alcohol (TBA) and ethanol (EtOH)
in reactive distillation has been studied.β-Zeolite catalysts with three compositions (Si/Al ratio=13, 36 and 55) were compared by testing the reaction in a semi-batch
reactor. Although they showed almost the same performance, the one with Si/Al ratio of 55 was selected for the kinetic and
reactive distillation studies because it is commercially available and present in a ready-to-use form. The kinetic parameters
of the reaction determined by fitting parameters with the experimental results at temperature in the range of 343–363 K were
used in an ASPEN PLUS simulator. Experimental results of the reactive distillation at a standard condition were used to validate
a rigorous reactive distillation model of the ASPEN PLUS used in a simulation study. The effects of various operating parameters
such as condenser temperature, feed molar flow rate, reflux ratio, heat duty and mole ratio of H2O : EtOH on the reactive distillation performance were then investigated via simulation using the ASPEN PLUS program. The
results were compared between two reactive distillation columns: one packed withβ-zeolite and the other with conventional Amberlyst-15. It was found that the effect of various operating parameters for both
types of catalysts follows the same trend; however, the column packed withΒ-zeolite outperforms that with Amberlyst-15 catalyst due to the higher selectivity of the catalyst. 相似文献
10.
Bunjerd Jongsomjit Paninee Kaewkrajang Sieghard E. Wanke Piyasan Praserthdam 《Catalysis Letters》2004,94(3-4):205-208
Activities of ethylene/α-olefin copolymerization were found to increase with silane-modified silica-supported MAO using ansa-zirconocene catalyst. The increase in activities was less pronounced when higher α-olefins were used. However, silane modification resulted in the narrower molecular weight distribution of polymers. 13C NMR revealed that ethylene incorporation in all systems gave polymers with the similar triad distribution. 相似文献