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21.
A method of measurement of solids holdup in a three-phase reactor by analyzing the shape and the phase lag or lead of an ultrasonic wave has been proposed. The solids holdup in a solids-dilute three-phase fluidized bed could be measured without being affected by the presence of gas bubbles. The experimental values of solids axial dispersivity measured by the ultrasonic technique are in reasonable agreement with an empirical correlation of previous data obtained by other methods. The possibility of the application of the ultrasonic technique to the measurement of solids holdup in a three-phase fluidized bed has been suggested. 相似文献
22.
Silica-supported cobalt catalysts for the selective reduction of nitrogen monoxide with propene 总被引:1,自引:0,他引:1
Megumu Inaba Yoshiaki Kintaichi Masaaki Haneda Hideaki Hamada 《Catalysis Letters》1996,39(3-4):269-274
Catalytic behavior of silica-supported transition metals for NO reduction with propene in the presence of oxygen was investigated. While both silica and cobalt oxides did not show any activity for the selective NO reduction, impregnated CoO/SiO2 prepared from cobalt acetate showed good activity although the preparation conditions had significant effect on the activity. It was suggested that highly dispersed surface Co2+ ions on silica are responsible for the catalytic activity. 相似文献
23.
Yasuro Ikuma Eriko Shimada Nobuko Okamura 《Journal of the American Ceramic Society》2005,88(2):419-423
An extensive X-ray study of CeO2 –Nd2 O3 solid solutions was performed, and the densities of solid solutions containing various concentrations of NdO1.5 were measured using several techniques. Solid solutions containing 0–80 mol% NdO1.5 were synthesized by coprecipitation from Ce(NO3 )3 and Nd(NO3 )3 aqueous solutions, and the coprecipitated samples were sintered at 1400°C. A fluorite structure was observed for CeO2 –NdO1.5 solid solutions with 0–40 mol% NdO1.5 , which changed to a rare earth C-type structure at 45–75 mol% NdO1.5 . The change in the lattice parameters of CeO2 –NdO1.5 solid solutions, when plotted with respect to the NdO1.5 concentration, showed that the lattice parameters followed Vegard's law in both the fluorite and rare earth C-type regions. The maximum solubility limit for NdO1.5 in CeO2 solid solution was approximately 75 mol%. The relationship between the density and the Nd concentration indicated that the defect structure followed the anion vacancy model over the entire range (0–70 mol% NdO1.5 ) of solid solution. 相似文献
24.
Toshihiro Nagao Yuji Shimada Yoshie Yamauchi-Sato Takaya Yamamoto Masaaki Kasai Kentaro Tsutsumi Akio Sugihara Yoshio Tominaga 《Journal of the American Oil Chemists' Society》2002,79(3):303-308
A commercial product of CLA contains almost equal amounts of cis-9,trans-11 (c9,t11)-CLA and trans-10,cis-12 (t10,c12)-CLA. We attempted to enrich the two isomers by a two-step selective esterification using Candida rugosa lipase that acted on c9,t11-CLA more strongly than on t10,c12-CLA. An FFA mixture containing CLA isomers was esterified with an equimolar amount of lauryl alcohol in a mixture of 20%
water and the lipase. When the esterification of total FA reached 50%, two isomers were fractionated in a good yield: t10,c12-CLA was enriched in FFA, and c9,t11-CLA was recovered in lauryl esters. The FFA were esterified again to enrich t10,c12-CLA. At 27.3% esterification of total FA, the t10,c12-CLA content in FFA increased to 64.8 wt% with 89.3% recovery: The ratio of the content of t10,c12-CLA to that of two isomers was 95.9%. Lauryl esters obtained by the single esterification were employed for enrichment
of c9,t11-CLA. After the esters were hydrolyzed, the resulting FFA were esterified again with lauryl alcohol. At 62.0% esterification
of total FA, the c9,t11-CLA content in lauryl esters increased to 73.3 wt% with 79.4% recovery: The ratio of the content of c9,t11-CLA to that of two isomers was 95.6%. In a 600-g-scale purification, molecular distillation was effective in separating
the reaction mixture into lauryl alcohol, FFA, and lauryl ester fractions. 相似文献
25.
A simple solid state technique for electrochemical micromachining of metal substrates using a metal ion conductor (Na-β″-Al2O3) was proposed. The fundamental solid electrochemical cell consists of a (anode) metal substrate (M = Ag, Cu, Zn, and Pb)/pyramidal Na-β″-Al2O3/Ag (cathode) system, where the contact diameter between M/Na-β″-Al2O3 was extremely small, on the order of a few micrometer. Under an applied electric field, the metal substrate was electrochemically oxidized to metal ions (Mn+) at the M/Na-β″-Al2O3 microcontact. These Mn+ ions migrated into the Na-β″-Al2O3. As a result of continuous electrolysis, the metal substrate was locally consumed at the microcontact, and thus solid state electrochemical micromachining was accomplished. As expected, the machining size or depth depended on the electrolysis conditions (current, operating time) and the apex configuration of pyramidal Na-β″-Al2O3. Moreover, the scanning of the Na-β″-Al2O3 pyramid during electrolysis produced a fine patterned metal substrate. In the present paper, solid state electrochemical micromachining was performed for several metal substrates, and its advantages and disadvantages vis-a-vis the conventional electrochemical micromachining method are discussed in detail. 相似文献
26.
Masaaki Takehisa Hiromasa Watanabe Hirondo Kurihara Kouichi Yamaguchi Hayato Nakajima Toshiaki Yagi Terutaka Watanabe Takanobu Sugo Takeshi Suwa Shinsaku Maruyama Atsuro Kodama Takeo Shimada Yoshio Maruyama Masamichi Tohei Takeshi Wada Sueo Machi 《应用聚合物科学杂志》1979,24(8):1831-1844
Radiation-induced polymerization of ethylene using aqueous tert-butyl alcohol as medium was carried out in a large-scale pilot plant with a 50-liter central source-type reactor at a pressure of 105 to 395 kg/cm2, temperature of 30° to 80°C, mean dose rate of 4.5 × 104 to 1.9 × 105 rads/hr, ethylene feed rate of 5.5 to 23.5 kg/hr, and medium feed rate of 21 to 102 l./hr. The space–time yield and molecular weight of the polymer were in the range of 4.7 to 16.8 g/l.-hr and 1.3 × 104 to 8.9 × 104, respectively. The space–time yield and molecular weight increased with mean residence time at 30°C, whereas at 80°C they became almost independent of the time. The space–time yield increased with pressure and dose rate, slightly decreased with temperature, and was maximum at ethylene molar fraction of 0.5. The polymer molecular weight increased with pressure and ethylene molar fraction, and decreased with dose rate and temperature. The total amount of deposited polymer on the reactor wall, source case wall, and scraping blades was usually less than 1 kg, which was negligibly small for the analysis of polymerization. Continuous discharge of the polymer slurry and production of fine-powder polyethylene were successfully carried out. In the central source-type reactor, a dose rate of 1.9 × 105 rads/hr was obtained with a 60Co source of ca. 12 kCi. 相似文献
27.
Three kinds of trapped radicals are observed in poly(maleic anhydride) (Poly-MAH) which were prepared by the use of radical initiators such as AIBN or BPO. It was found that these radicals were transformed to the active species so as to initiate the cationic polymerization. The structure of these radicals was studied by the ESR and the kinetic analysis of MAH polymerization in the presence of various additives. 相似文献
28.
Nanocrystalline Ni3Al was fabricated through mechanical alloying of elemental powders and spark plasma sintering. The nanocrystalline Ni3Al has a nearly full density after being sintered at 1223 K for 10 min under a pressure of 65 MPa. Isothermal and cyclic oxidations of nanocrystalline Ni3Al were tested at 1173–1373 K with intervals of 100 K. The results indicate that nanocrystalline Ni3Al exhibits excellent isothermal and cyclical oxidation resistance. The oxide scales consist primarily of dense and continuous -Al2O3. The grain refinement is beneficial for improving the oxidation resistance of Ni3Al by providing more nucleation centers for the Al2O3 formation, promoting the selective formation of Al2O3 and improving the adhesion of oxide scales to the matrix. 相似文献
29.
We report experimental results on enhanced backscattering from a plane mirror that is viewed through polymer-film-dispersed nematic liquid crystals. The distribution of the averaged intensity of the light reflected from the mirror placed behind the polymer film is investigated with an image-processing system when a Gaussian beam wave is incident. The enhanced light peak is observed in an incident beam direction, the result of which is predicted by a theory based on the circular Gaussian statistic random-phase-screen model. We pay attention to the enhancement dependence on parameters such as the distance between the polymer film and the flat mirror. The observed result is similar to a previous study by Jakeman et al. in which a random diffusive glass plate was used as a random-phase screen [J. Phys. D 21, 32 (1988)]. 相似文献
30.