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51.
Pt, Ir, Pt-Ir and Pt-Ni bimetallic catalysts supported on NaY- and HY-zeolite were examined as a catalyst for producing gasoline
from n-decane via simultaneous reforming and cracking. The catalysts were prepared by calcining and reducing metal-ion-exchanged
Y-zeolite with O2 and H2 at 300°C., respectively. Thus prepared catalysts were characterized by hydrogen chemisorption and temperature programmed
desorption of ammonia. Pt-Ni/NaY and Pt-Ir/NaY bimetallic catalysts offered the improved activity maintenance compared to
Pt/NaY monometallic catalyst. The catalysts supported on HY-zeolite showed higher selectivity toward C5–C7 and skeletal isomers of C5–C7- and C8–C10 than those of the catalysts supported on NaY-zeolite, which is a desired characteristic for increasing octane value of gasoline
these days. However, deactivation with reaction time was much more pronounced on HY-zeolite-supported catalyst. When the catalyst
was prcsulfided with H,S, the stability with time on stream was enhanced and the selectivity was quite different from that
of the catalyst before presulfiding. The acidity of Y-zeolite and presulfiding of catalyst greatly influenced the activny,
selectivity and stability of Pt, Ir, Pt-Ir and Pt-Ni bimetallic catalysts supported on Y-zeolite in n-decane reforming reaction. 相似文献
52.
Hyoung Jin Choi Yong Woo Inn Myung S. Jhon 《Korean Journal of Chemical Engineering》1994,11(3):145-152
Polymer migration is a generally well-known phenomenon in a flow field, and it has been verified that the sources of such
phenomena are nonhomogeneity of the flow, concentration effects and hydrodynamic interactions between the polymer molecules.
In addition, temperature effects were found to be another source of polymer migration. The Langevin equation for a polymer
molecule was first derived from single chain dynamics using a kinetic theory for the bead-spring elastic harmonic dumbbell
model, as described in part I (reference [1]). In this paper the diffusion equation and concentration profile of the polymer
molecules induced by a temperature gradient are obtained from the Fokker-Planck equation. A new differential operator is also
introduced to calculate the concentration profile. From the concentration equation obtained in the general flow geometry,
we find that in dilute polymer solution there are significant effects on the polymer migration not only due to the nonhomogeneity
of the flow field but also due to temperature gradients. 相似文献
53.
Layered Li[Li0.12NizMg0.32−zMn0.56]O2 oxide cathodes containing lithium atoms in the transition metal layers were synthesized and characterized using X-ray diffraction (XRD), galvanostatic cycling, and differential scanning calorimetry (DSC). The Li[Li0.12NizMg0.32−zMn0.56]O2 cathodes deliver a specific discharge capacity of about 190 mAh/g at room temperature and 236 mAh/g at 55 °C when cycled between 2.7 and 4.6 V versus Li/Li+. Excellent capacity retention and smooth potential profiles at room and elevated temperatures over extended cycles suggest that this material does not convert into a spinel structure. 相似文献
54.
A D-Phenylalanine (Phe) imprinted terpolymer, Polyacrylonitrile-Poly(acrylic acid)-Poly(acryl amide) (Poly(AN-AA-AAm)) bead
was prepared by the wet-phase inversion method. Acrylamide (AAm) and acrylic acid (AA) were used as the functional monomer
and acrylonitrile (AN) was used as a physical cross linker. The characteristics of selective adsorption by the D-Phe imprinted
terpolymer beads were investigated at high concentrations of Phe racemate solution, 1 g Phe/L, and 10 g Phe/L. The adsorption
selectivity of the D-Phe imprinted terpolymer beads prepared by anin-situ implanting method reached 0.82 and 0.8 at 1.0 g and 10 g Phe/L racemate solution, respectively, and almost all of the adsorbed
D-Phe and about 43% of the adsorbed L-Phe were desorbed by 4% acetic acid. The uptake capacities of the terpolymer beads were
maintained for several repeated batches. 相似文献
55.
Jae Beom Kim Ki Hyun Yoon Yong S. Cho Woo Sup Kim Eung Soo Kim 《Journal of the American Ceramic Society》2005,88(3):612-616
Microwave dielectric properties of (1− x )(Na1/2 Nd1/2 )TiO3 (NNT)− x La(Mg1/2 Ti1/2 )O3 (LMT) system have been investigated with focus on structural ordering and far IR reflectivity spectra. A single perovskite phase was found to exist with various superlattice reflections over the entire compositional range. 1:1 ordering observed in the (111) reflection of X-ray diffraction patterns was found to progress significantly in the specimens above x =0.8. The ordering characteristics that presumably related to B-site Mg/Ti ordering were assumed to affect favorably the quality factor at microwave frequencies. The increase of the quality factor also could be explained in terms of the decrease of lattice anharmonicity with LMT by analysis of far IR reflectivity spectra. As expected from the values of pure NNT and LMT, the dielectric constant and the temperature coefficient of frequency tended to gradually decrease with increasing LMT content. 相似文献
56.
A heating process for obtaining free-standing carbon nanotube emitters is presented with the aim of improving field-emission properties from the screen-printed multiwalled carbon nanotube (MWCNT) films. Using an atmosphere with an optimum combination of nitrogen and air for heat treatment of CNT films, the CNT emitters can be made to protrude from the surface. This allows for a high emission current and the formation of very uniform emission sites without special surface treatment. The morphological change of the CNT film by this technique has eliminated additional processing steps, such as surface treatment which may result in secondary contamination and damage to the film. Despite its simplicity the process provides a high reproducibility in emission current density which makes the films suitable for practical applications. 相似文献
57.
D. J. Twait W. J. Lackey † Arlynn W. Smith Woo Y. Lee John A. Hanigofsky 《Journal of the American Ceramic Society》1990,73(6):1510-1518
Thermodynamic calculations were performed using a modified solgasmix-pv computer program in order to study the feasibility of codepositing boron nitride (BN) plus aluminum nitride (AIN) by chemical vapor deposition. Reactants considered were AICl3 , BCl3 or B2 H6 , NH3 , and H2 . Deposition diagrams were generated for the BCl3 -AICl3 -NH3 system over a range of processing conditions such as temperature, total system pressure, and reagent concentrations. Codeposition of BN + AIN was predicted by the calculations for temperatures in the range of 900 to 1700 K and pressures of 10.13 to 101.3 kPa. The predicted deposition efficiency at equilibrium was much higher for BN than for AlN at most reagent compositions. The AlN deposition efficiency increased with decreasing temperature and decreasing BCl3 content, with increasing NH3 content, or with the addition of H2 . Aluminum chlorides were found to be the dominant gaseous species. 相似文献
58.
Hydrogen sulfide gas was removed in a 2-dimensional gas-lift reactor by the photosynthetic microorganismChlorobium thiosulfatophilum using light emitting diodes (LEDs) as a light source. LEDs saved light energy by 99% compared with the incandescent light
source. The plate-type gas-lift reactor removed hydrogen sulfide five times better per unit mg of protein, and performed two
times better in the maximum performance per unit luminous flux, compared with cylindrical fermentors. 相似文献
59.
Sang Woo Kim Jong-Ho Lee Joosun Kim Hae-Weon Lee 《Journal of the American Ceramic Society》2004,87(12):2213-2217
The effect of zinc ions added to silica film on the electrical and structural properties of a silica/indium tin oxide two-layer film which had been prepared by solution coating for electromagnetic shielding of displays was studied. The volume resistivity of the undoped silica/indium tin oxide film was more than 3 times as high as that of the zinc-doped silica/indium tin oxide film. The addition of divalent cations, zinc ions, to the overcoated layer led volume resistivity of the two-layer film to decrease significantly and also caused a long-term increase in stability. The decrease in volume resistivity was due to the addition of zinc ions that changed the interface ionization and helped to enhance the electrical conductivity in the two-layer film. 相似文献
60.
Chang?Duk?Kang Sang?Jun?SimEmail author Young?Sang?Cho Woo?Sik?Kim 《Korean Journal of Chemical Engineering》2003,20(3):482-486
The removal of copper from wastewater by ferric/limestone coagulation followed by screen filtration was carried out at a laboratory
scale. The optimum coagulant (FeCl3) dose and working pH were 50 mg// of Fe(m) and pH 7.5, respectively, through jar tests. For the efficient removal of copper
from wastewater, we developed a novel process including the co-precipitation of copper with FeCl3, alkalization in a limestone aeration bed, and separation of precipitates in a sedimentation tank coupled with internal stainless
steel screen filter. The performance results showed that removal of copper from the solution was over 99.5%. The pH was effectively
maintained over 7.5 in limestone bed during the whole process. Ferric hydroxide/copper aggregates were removed over 99% by
stainless steel screen filter of 1,450 mesh. Periodic air backwashing alleviated fouling of the filter surface. 相似文献