• Korean Chemical Engineering Research
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• v.52 no.3
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• pp.279-288
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• 2014

Nuclear energy is expected to meet the growing energy demand while avoiding CO2 emission. However, the problem of accumulating spent fuel from current nuclear power plants which is mainly composed of uranium oxides should be addressed. One of the most practical solutions is to reduce the spent oxide fuel and recycle it. Next-generation fuel cycles demand innovative features such as a reduction of the environmental load, improved safety, efficient recycling of resources, and feasible economics. Pyroprocessing based on molten salt electrolysis is one of the key technologies for reducing the amount of spent nuclear fuel and destroying toxic waste products, such as the long-life fission products. The oxide reduction process based on the electrochemical reduction in a LiCl-$Li_2O$ electrolyte has been developed for the volume reduction of PWR (Pressurized Water Reactor) spent fuels and for providing metal feeds for the electrorefining process. To speed up the electrochemical reduction process, the influences of the feed form for the cathode and the type of anode shroud on the reduction rate were investigated.

• Applied Chemistry for Engineering
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• v.27 no.3
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• pp.313-318
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• 2016

In this study, an amorphous silica was functionalized with aminosilane, N-[(3-trimethoxysilyl)propyl]ethylenediamine (2NS) and the late transition metal catalysts including ($(DME)NiBr_2$ and $PdCl_2$(COD)) were subsequently immobilized on the functionalized amorphous silica for norbornene polymerization. Effects of the polymerization temperature, polymerization time, Al/Ni molar ratio, and type of co-catalyst on norbornene polymerization were investigated. Unsupported late transition metal catalysts did not show any activities for norbornene polymerization. However, the $SiO_2$/2NS/Ni catayst with MAO system, with increasing polymerization temperature, increased the polymerization activity and decreased the molecular weight of the polynorbornene (PNB). Furthermore, the catalyst when increasing polymerization temperature caused the decrease in both the polymerization activity and molecular weight of PNB. This confirmed that the stability of $SiO_2$/2NS/Ni at a high temperature was greater than that of $SiO_2$/2NS/Pd. Also the longer polymerization time resulted in the higher conversion of norbornene for both catalysts. When the Al : Ni molar ratio was 1000 : 1, the highest activity (15.3 kg-PNB/($({\mu}mol-Ni^*hr$)) but lowest molecular weight ($M_n$ = 124,000 g/mol) of PNB were achieved. Also $SiO_2$/2NS/Ni catalyst with borate/TEAL resulted in diminishing the polymerization activity and molecular weight of PNB with increasing the polymerization temperature.

• Korean Chemical Engineering Research
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• v.45 no.5
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• pp.506-514
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• 2007

To select the best oxygen carrier particle for syngas fueled chemical-looping combustor, the reduction reactivity and carbon deposition characteristics were determined in a thermogravimetric analyzer. Four kinds of oxygen carrier particles (NiO/bentonite, $NiO/LaAl_{11}O_{18}$, $Co_xO_y/CoAl_2O_4$, $NiO/NiAl_2O_4$) were tested with the simulated syngas (30% $H_2$, 10% $CO_2$, 60% CO) as a reduction gas. With each of these particles, the maximum conversion and oxygen transfer capacity increase with increasing the reduction temperature At the given experimental range, the optimum operating temperature to maximize oxygen transfer rate is found to be $900^{\circ}C$ and carbon deposition on the particles could avoid at the temperature above $800^{\circ}C$. Among four kinds of oxygen carrier particles, the NiO-based particles exhibits better reactivity than the CoO-based particle. Moreover, the NiO/bentonite particle produces the best reactivity based on the oxygen transfer rate and the degree of carbon deposition. The measured oxygen transfer rate increases as the metal oxide content in NiO/bentonite particle is increased thereby higher metal oxide contents could provide stable operation of chemical-looping combustor.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.13 no.4
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• pp.263-269
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• 2015

It is necessary to investigate the electrodeposition behavior of uranium and other elements on the cathode in the electrorefining process to recover the uranium selectively from the reduced metals of the electrolytic reduction process since transuranic elements and rare earth elements is dissolved in the LiCl-KCl eutectic salt. Study on separation factors of U, Ce, Y and Nd based on U and Ce was performed to investigate the deposition behavior of the cathode with respect to the concentration of rare earth elements in LiCl-KCl eutectic salt. After electrorefining with constant current mode by using Ce metal as a sacrifice anode, the contents of U, Ce, Y and Nd in the salt phase and the deposit phase of the cathode were analyzed, and separation factors of the elements were obtained from the analyses. Securing conditions of pure uranium recovery in the elctrorefining process was investigated by considering the separation factors with respect to $UCl_3$ and $CeCl_3/UCl_3$ ratio.

• Applied Biological Chemistry
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• v.42 no.2
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• pp.134-139
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• 1999

The characteristics of anthocyanin pigments extracted from cherry(Prunus serrulata L. var. spontanea Max. Wils.) were investigated at the various conditions, such as light, temperature, organic acid, metal ion and pH. The pigments were fairly stable under the sunlight during the 20 days storage period at room temperature. The pigments covered with the Al-foil, as well as red, blue, green and yellow films, were very stable at pH 2.5. The high thermal stability (over the 64% at $115^{\circ}C$, 30 min) of the pigments in the dark at pH 2.5 was also found. In the presence of organic acid, the hyperchromic effect of red color was greatly increased in the dark at $25^{\circ}C$. Addition of metal ion, such as $Na^+,\;K^+,\;Mg^{2+},\;Ca^{2+}\;and\;Mn^{2+}$, was contributed on the stability in color at pH 2.5 throughout 20 days storage period in the dark at $25^{\circ}C$. However, $Cu^{2+}\;and\;Fe^{3+}$ caused the rapidly degradation of pigments, and $Al^{3+}$ converted red color to blueish violet. The hyperchromic effect of the red color increased, as pH decreased. Therefore, these results indicated that cherry anthocyanin pigments might be used as the potential sources of natural red colorant for foods.

• Korean Journal of Food Science and Technology
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• v.47 no.4
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• pp.460-467
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• 2015

Sea urchin roe obtained from Anthocidaris crassispina and Pseudocentrotus depressus was briefly salt-fermented (5%), followed by ethanol treatment (1%) and the physicochemical properties as well as antioxidant activity were investigated. Compared to raw sea urchin roes, the salted one showed a significantly low amount of water (p<0.001) high salinity (p<0.05), ash content (p<0.001) and Na content (p<0.001). With salt-fermentation, the redness (p<0.05) and yellowness (p<0.001) of roe decreased noticeably, indicating the decomposition of endogenous carotenoids. Accordingly, the salted roe showed a lower DPPH radical scavenging activity than its unsalted counterpart. Additionally, it showed a significantly lower metal-chelating activity (p<0.05) and metal chelator content (e.g. ortho-phenolics) displayed by a negligible difference in titratable acidity. The salted roe showed significantly increased hardness (p<0.05) and total reducing capacity (p<0.001), which were attributed to the protein coagulation and the release of antioxidants bound to macromolecules after the ethanol treatment, respectively.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.8 no.1
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• pp.65-70
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• 2010

The distillation rate on LiCl-KCl eutectic salt under different vacuums from 0.5-50 mmHg was first investigated by using both a non-isothermal and a isothermal thermogravimetric (TG) analysis. Based on the non-isothermal TG data, distillation rate equations as a function of the temperature could be derived. Calculated flux by these model flux equations was in agreement with the distillation rate obtained from isothermal TG analysis. A distillation rate of $10^{-4}-10^{-5}$ mole $cm^{-2}sec^{-1}$ is obtainable at temperatures less than 1300K and vacuums of 0.5-50 mmHg. About a 99% salt distillation efficiency was obtained after an hour at a temperature above 1150 K under 50 mmHg in a small scale distillation test system. An increase in the vaporizing surface area is relatively effective for removing residual salt in the remaining particles, when compared to that for the vaporizing time. Over 99.95% of total distillation efficiency was obtained for a 1-h distillation operation by increasing the inner surface area from $4.52cm^2$ to $12.56cm^2$.

• Korean Chemical Engineering Research
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• v.50 no.2
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• pp.217-222
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• 2012

The synthesis of dimethyl carbonate(DMC) is a promising reaction for the use of naturally abundant carbon dioxide. DMC has gained considerable interest owing to its versatile chemical reactivity and unique properties such as high oxygen content, low toxicity, and excellent biodegradability. In this study, the synthesis of DMC through the transesterification of ethylene carbonate(EC) with methanol was investigated by using ionic liquid and metal oxide catalysts. The screening test of different catalysts revealed that choline hydroxide ([Choline][OH]) and 1-n-butyl-3-methyl imidazolium hydroxide([BMIm][OH]) had better catalytic performance than metal salts catalysts such as MgO, ZnO and CaO. The effects of reaction parameters such as reaction temperature, MeOH/EC mole ratio, and carbon dioxide pressure on the reactivity of [Choline][OH] catalyst were discussed. High temperature and high MeOH/EC mole ratio were favorable for high conversion of EC. However, the yield of DMC showed a maximum when carbon dioxide pressure was 1.34 MPa, and then it decreased for higher carbon dioxide pressure. Zinc chloride($ZnCl_2$) was used as co-catalyst with the ionic liquid catalyst. The mixed catalyst showed a synergy effect on the EC conversion and DMC yield probably due to the acid-base properties of the catalysts.

• Clean Technology
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• v.18 no.1
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• pp.83-88
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• 2012

In order to improve the stability of ${\gamma}-Al_2O_3$ on hydrolysis of $SF_6$, the catalytic promoters were investigated in this study. The crystal phase of ${\gamma}-Al_2O_3$ is transformed to their ${\alpha}$-phase during hydrolysis of $SF_6$. Various metal oxides were applied as the promoter material that is Ga, Mg, and Zn and the promoter of 1, 5, and 10 wt% was impregnated over ${\gamma}-Al_2O_3$ by the impregnation method. Specially, it were confirmed in the catalytic activity tests and XRD analysis that ZnO/${\gamma}-Al_2O_3$ catalyst had the high activity for decomposition of $SF_6$ by catalytic hydrolysis and the crystal phase of ZnO promoted ${\gamma}-Al_2O_3$ was not transformed. From these results, it could be known that the stability of ${\gamma}-Al_2O_3$ is enhanced with the catalytic promotion of ZnO impregnated over the surface of catalyst.

• Journal of the Korean Chemical Society
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• v.54 no.2
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• pp.192-197
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• 2010

The spinel compound was obtained by the thermal decomposition of Zn-Co and Zn-Ni gel prepared by sol-gel method using oxalic acid as a chelating agent. The formation of spinel compound has been comfirmed by thermogravimetric analysis (TGA), x-ray powder diffraction (XRD) and infrared spectroscopy (IR). The particle size of 13 nm~16 nm was calculated by Scherrer's equation. The sol-gel method provides a practicable and effective route for the synthesis of the spinel compound at low temperature ($350^{\circ}C$). The kinetic parameters such as activation energy (Ea) and pre-exponential factor (A) for each compound were found by means of the Kissinger method and Arrhenius equation. The decomposition of spinel compound has an activation energy about 155 kJ/mol. Finally, the thermodynamic parameters (${\Delta}G^{\varphi}$, ${\Delta}H^{\varphi}$, ${\Delta}S^{\varphi}$) for decomposition of spinel compound was determined.