• Korean Membrane Journal
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• v.5 no.1
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• pp.68-74
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• 2003

Methane steam reforming (MSR) reaction for hydrogen production was studied in a membrane reactor (MR) using two tubular membranes, one Pd-based and one of porous alumina. A higher methane conversion than the thermodynamic equilibrium for a traditional reactor (TR) was achieved using MRs. The experimental temperature range was 350-500$^{\circ}C$; no sweep-gas was employed during reaction tests to avoid its back-permeation through the membrane and the steam/methane molar feed ratio (m) varied in the range 3.5-5.9. The best results (the difference between the MR conversion and the thermodynamic equilibrium was of about 7%) were achieved with the alumina membrane, working with the highest steam/methane ratio and at 450$^{\circ}C$. Silica membranes prepared at KRICT laboratories were characterized with permeation tests on single gases (N$_2$, H$_2$ and CH$_4$). These membranes are suited for H$_2$ separation at high temperature.

• Carbon letters
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• v.25
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• pp.33-42
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• 2018

Activated carbon (AC) was modified by ammonium persulphate or nitric acid, respectively. AC and the modified materials were used as catalyst supports. The oxygen groups were introduced in the supports during the modifications. All the supports were characterized by $N_2$-physisorption, Raman, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and thermogravimetric analysis. Methanol synthesis catalysts were prepared through wet impregnation of copper nitrate and zinc nitrate on the supports followed by thermal decomposition. These catalysts were measured by the means of $N_2$-physisorption, X-ray diffraction, XPS, temperature programmed reduction and TEM tests. The catalytic performances of the prepared catalysts were compared with a commercial catalyst (CZA) in this work. The results showed that the methanol production rate of AC-CZ ($23mmol-CH_3OH/(g-Cu{\cdot}h)$) was higher, on Cu loading basis, than that of CZA ($9mmol-CH_3OH/(g-Cu{\cdot}h)$). We also found that the modification methods produced strong metal-support interactions leading to poor catalytic performance. AC without any modification can prompt the catalytic performance of the resulted catalyst.

• Journal of Magnetics
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• v.9 no.4
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• pp.109-112
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• 2004

The HDDR (Hydrogenation-Disproportionation-Desorption-Recombination) process is a special method to produce anisotropic NdFeB powders for bonded magnet. The effect of the modified HDDR process on magnetic properties of $Nd_2Fe_{14}B$-based magnet with several composition $Nd_{11.2}Fe_{66.5-x}Co_{15.4}B_{6,8}Zr{0.1}Ga_x(x=0{\sim}1.0)$ and that of microelement Ga, disproportional temperature and annealing temperature on $_jH_c$, grain size were investigated in order to produce anisotropic powder with high magnetic properties. It was found that modified HDDR process is very effective to enhance magnetic properties and to fine grain size. The addition of Ga could change disproportionation character remarkably of the alloy and could improve magnetic properties of magnet powder. Increasing annealing temperature induces significant grain growth. And grain size produced by modified HDDR process is significantly smaller than those produced by conventional HDDR process.

• Journal of the Korean Electrochemical Society
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• v.9 no.2
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• pp.95-99
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• 2006

Electrochemical properties were studied for a single particle of active material of hydrogen storage alloy $(MmNi_{3.55}Co_{0.75}Mn_{0.4}Al_{0.3})$ and nickel hydroxides $(NiOH)_2$ for the secondary Nickel Metal Hydride (Ni-MH) batteries using the microelectrode, which was manipulated to make electrical contact with an active material particle for cyclic voltammograms (CV) and potential-step experiments. As a result of CV test, it was found that three kinds of hydrogen oxidation peaks at -0.9, -0.75 and -0.65 V and hydrogen evolution peak at -0.98 V for hydrogen storage alloy were separately observed and two kinds of peaks of proton oxidation/reduction at 0.45 and 0.32 V and oxygen evolution reaction (OER) at 0.6 V for nickel hydroxides were also more clearly observed. Furthermore hydrogen diffusion coefficient within a single particle was also found to vary the order between $10^{-9}\;and\;10^{-10}cm^2/s$ over the course of hydrogenation and dehydrogenation process for potential-step experiments.

• Journal of Magnetics
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• v.4 no.2
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• pp.46-51
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• 1999

A solid-HDDR characteristics of the Nd-Fe-B-type alloys magnetic properties of the solid-HDDR treated materials have been investigated using three types of alloys; $Nd_{15}Fe_{77}B_8 (alloy A), Nd_{16}Fe_{75.9}B_8Zr_{0.1}(alloy B), and Nd_{12.6}Fe_{68.7}Co_{11.6}B_8Ga_{1.0}Zr_{0.1} $(alloy C). It has been found that the four-components alloy B and six-components alloy C have showed higher hydrogenation temperatures than the ternary alloy A. The alloys A and B appeared to absorb more hydrogen gas more rapidly as well compared to the alloy C. The disproportionation temperature of hydrogenated materials was exhibited no significant difference among the alloys. The thermal stability of the hydrided materials of the three types of alloys was found to become more stable in order of number of components. The disproportionation and the recombination kinetics were significantly sluggish in the solid-HDDR manner with respect to the conventional manner. Some degree of anisotropic nature was found to exist in the ingot and this anisotropic nature was retained even after the solid-HDDR treatment. It was suggested the solid-HDDR treatment may possibly be used for a preparation of an isotropic or anisotropic Nd-Fe-B-type cast magnets.

• Transactions of the Korean hydrogen and new energy society
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• v.9 no.3
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• pp.111-118
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• 1998

The intrinsic degradation behavior of $(V_{0.53}Ti_{0.47})_{0.925}Fe_{0.075}$ alloy with BCC structure and the two plateau regions (the low and high plateau region) has been investigate during the temperature-induced hydrogen absorption-desorption cycling (thermal cycling). After 400 thermal cycles between room temperature and $600^{\circ}C$ under 10atm $H_2$, the total reversible hydrogen absorption capacity decreased by about 40%. From thermal desorption analysis it was found that the degradation behavior at each plateau region was different. In addition, XRD analysis showed that the crystal structure of the sample in de-hydrided state was changed from BCC to BCT after degradation, and that of the sample in hydrided state it was maintained as FCC although peaks were broadened after degradation. From the result of static isothermal hydrogenation treatment it were found that crystal structure change from BCC to BCT was caused by the thermal energy. TEM analysis showed that the peak broadening was due to the formation of an amorphous phase in FCC matrix.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.2
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• pp.24-28
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• 2006

Electrochemical hydrogenation/dehydrogenation properties were studied for a single particle of a Mm-based(Mm : misch metal) hydrogen storage alloy($MmNi_{3.55}Co_{0.75}Mn_{0.4}Al_{0.3}$) for the anode of Ni-MH batteries. A carbon fiber microelectrode was manipulated to make electrical contact with an alloy particle, and the cyclic voltammetry and the galvanostatic charge/discharge experiments were performed. A single particle of the alloy showed the discharge capacity of 280[mAh/g], the value being 90[%] of the theoretical capacity. Data were compared with that of the composite film consisting of the alloy particles and a polymer binder, which is more practical form for Ni-MH batteries. Additionally, pulverization of the alloy particles are directly observed. Compared with the conventional composite film electrodes, the single particle measurements using the microelectrode gave more detailed, true information about the hydrogen storage alloy.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.793-794
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• 2010

Fischer-Tropsch(F-T) reaction, in which syngas($H_2+CO$) is transformed into liquid fuels, has attracted much attention recently due to the limited reservoir of petroleum. The formed F-T wax can be converted into various liquid fuels, such as gasoline, diesel, jet fuel, lubricants, etc., through the hydrocracking reaction. To carry out the hydrocracking reaction, the bifunctional catalyst is required, in which hydrogenation/dehydrogenation occurs over metal and cracking proceeds over solid acid sites. In this contribution, we review the reported hydrocracking catalysts and summarize some process variables (feed compositions, reaction temperature and reaction pressure) for each catalyst.

• Transactions of the Korean hydrogen and new energy society
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• v.22 no.3
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• pp.380-385
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• 2011

$MgH_2$ was synthesized by hydriding chemical vapor deposition (HCVD). In this study, we examined the hydrogen storage property of $MgH_2$ synthesized by HCVD. The results of pressure-composition-temperature (PCT) measurement showed that the HCVDed $MgH_2$ reversibly absorbed hydrogen as much as 6 wt%. Each hydrogenation rate was very greater than the conventional alloy methods. The reason was that the particle size made by HCVD was small as approximately 1 ${\mu}m$. The PCT of $MgH_2$ made by HCVD methode was similar to a commercial $MgH_2$. The ${\Delta}H$ and ${\Delta}S$ value are respectively -76.8 $kJ/mol{\cdot}H_2$ and -137.4 $kJ/mol{\cdot}H_2$. Mg made by HCVD methode was activated easily than commercial Mg. Also the initial reaction rate was faster than that of commercial $MgH_2$. 70% of the total storage were stored during 400s.

• Journal of Plant Biology
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• v.17 no.2
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• pp.69-83
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• 1974

To elucidate the relationship between chemical structure and biological activity of alantolactone, and also to investigate the relationship between the growth of cells and the respiration of Chlorella pyrenoidosa affected by alantolactone, alantolactone and isoalantolactone were isolated from Inula helenium L., and di-, and tetrahydroalantolactones were prepared by the hydrogenation. At a concentration of 5$\times$10-5M alantolactone, the growth rate of Chlorella was greatly reduced. The viability of cells was also reduced over 50% within 2 hr at a concentration of 2.5$\times$10-4M alantolactone. However, oxygen uptake was increased by 20% over 3 hr. And 14CO2 production from glucose-1-14C, glucose-6-14C and 14C-acetate-U.L. was also increased by alantolactone. Biological activityof alantolactone was significantly reduced by cysteine, reduced glutathione or cystine but not by tryptophan or histidine. It was detected by spectrophotometrically and by TLC that alantolactone was also reacted with thiols except cystine. The solution of alantolactone reached with thiol gave the UV absorption spectrum of $\alpha$-saturated ${\gamma}$-lactone, and most of SH groups were disappeared by the addition reaction. From the reaction mixture of alantolactone and cysteine, a lactone adduct was isolated and purified. Isoalantolactone had shown similar activity as alantolactone, however, it was appeared that di-, and tetrahydroalantolactones were not only inactive biologically but also in vitro. It was concluded that there was no correlationship between increased respiration rate and mortality of Chlorella. During the respiration TCA cycle was activated, however it was uncertain that the activation of EMP or HMP was also appeared. Alantolactone and isoalantolactone were biologically active compounds but others were inactive. The reactivity of $\alpha$-methylene ${\gamma}$-lactone moiety toward SH group was principally responsible for its biological activity in sesquiterpene lactones.