• Journal of Aerospace System Engineering
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• v.17 no.6
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• pp.1-8
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• 2023

Research, such as developing alternative energy in the transportation field, including aviation, is being actively conducted to solve the issue of current climate change. Interest in ammonia fuel as a carbon free energy (CFE) source is increasing due to the ease of liquefaction and transportation and similarity in energy density to that of methanol. However, explosiveness and toxicity of ammonia make it difficult to handle. Therefore, in this study, stable ammonia production was attempted using relatively easy-to-handle urea water solution (UWS). High temperature steam was used to promote the hydrolysis of ammonia. In order to determine the causes for ammonia production below the theoretical equivalent ratio, it was suggested that there were not enough collisions to promote the hydrolysis based on the kinetic theory of gases. The hydrolysis of unreacted isocyanic acid (HNCO) was tested according to the change in water supply. As a result, an increased amount of ammonia produced was confirmed. The increased amount of ammonia produced in a certain section was dependent on the steam temperature and the flow rate of water supplied.

• Journal of the Korea Institute of Military Science and Technology
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• v.18 no.2
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• pp.160-166
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• 2015

On board hydrogen generation from the hydrolysis of an active metal is very attractive due to its economical, convenient, and safe reasons. A Mg-graphite pellet has been designed as a hydrogen source for portable fuel cell. Mg (1 g) + 0.10 g graphite pellet showed an excellent hydrogen generation rate that is equivalent to 15.8 ml/g.min from its hydrolysis. The hydrogen generation rate of the pellet is significantly increased due to the galvanic corrosion by galvanic cells between Mg anode and graphite cathode in a 10.wt. % NaCl solution at a room temperature.

• Korean Chemical Engineering Research
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• v.53 no.1
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• pp.11-15
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• 2015

Sodium borohydride, $NaBH_4$, shows a number of advantages as hydrogen source for portable proton exchange membrane fuel cells(PEMFCs). Properties of $NaBH_4$ hydrolysis reaction using unsupported Co-B, Co-P-B catalyst were studied. BET surface area of catalyst, yield of hydrogen, effect of $NaBH_4$ concentration and durability of catalyst were measured. The BET surface area of unsupported Co-B catalyst was $75.7m^2/g$ and this value was 18 times higher than that of FeCrAlloy supported Co-B catalyst. The hydrogen yield of $NaBH_4$ hydrolysis reaction by unsupported catalysts using 20~25 wt% $NaBH_4$ solution was 97.6~98.5% in batch reactor. The hydrogen yield decrease to 95.3~97.0% as the concentration of $NaBH_4$ solution increase to 30 wt%. The loss of unsupported catalyst was less than that of FeCrAlloy supported catalyst during $NaBH_4$ hydrolysis reaction and the loss increased with increasing of $NaBH_4$ concentration. In continuous reactor, hydrogen yield of $NaBH_4$ hydrolysis was 90% using 1.2 g of unsupported Co-P-B catalyst with $3{\ell}/min$ hydrogen generation rate.

• Korean Chemical Engineering Research
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• v.50 no.4
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• pp.627-631
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• 2012

Sodium borohydride, $NaBH_4$, shows a number of advantages as hydrogen source for portable proton exchange membrane fuel cells (PEMFCs). The durability of Co-P-B/Cu catalyst for sodium borohydride hydrolysis reaction was studied. The effect of reaction temperature, $NaBH_4$ concentration, NaOH concentration and calcination temperature of catalyst on the durability of Co-P-B/Cu catalyst were measured. The gel formed during hydrolysis reaction affected the durability of catalyst (loss of catalyst). Formation of gel increased the loss of the catalyst. When $NaBH_4$ concentration was high and reaction temperature was higher than $60^{\circ}C$, loss of catalyst was low because gel was not formed. But under the temperature of $40^{\circ}C$, loss of catalyst increased due to gel formation When $NaBH_4$ concentration was 40 weight % and the reaction temperature was $40^{\circ}C$, the loss of catalyst increased as the NaOH concentration increased. As the calcination temperature of catalyst decreased, the loss of catalyst decreased and the activity of catalyst decreased. Calcination of the catalyst at high temperature enhanced the durability of catalyst but diminished the activity of catalyst.

• Korean Chemical Engineering Research
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• v.55 no.1
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• pp.13-18
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• 2017

Sodium borohydride, $NaBH_4$, shows a number of advantages as hydrogen source for UAV PEMFC (Unmaned Aerial Vehicle Proton Exchange Membrane Fuel Cells). In order to use for UAV, the weight and volume of byproduct should be small after $NaBH_4$ hydrolysis reaction. Therefore, the weight and volume of byproduct were studied after $NaBH_4$ hydrolysis reaction using unsupported catalyst. The effect of catalyst type, concentration of $NaBH_4$, concentration of NaOH and thickness of catalyst pack on the weight and volume of byproduct were studied. Most of byproduct was $NaB(OH)_4$ and superficial volume of byproduct increased due to foam evolved from byproduct. The weight and volume of byproduct were not affected by concentration of NaOH used stabilizer. The weight of byproduct decreased as concentration of $NaBH_4$ solution increased, but maximum volume of byproduct obtained at 23 wt% of $NaBH_4$. Suitable defoaming agent reduced the volume of byproduct.

• Journal of the Korean Applied Science and Technology
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• v.34 no.4
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• pp.883-891
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• 2017

For the preferential oxidation of CO contained in the fuel of polymer electrolyte membrane fuel cell (PEMFC), CuO-$CeO_2$ mixed oxide catalysts were prepared by the sol-gel and co-precipitation methods to replace noble metal catalysts. In the catalyst preparation by the sol-gel method, Cu/Ce ratio and hydrolysis ratio were changed. The catalytic activity of the prepared catalysts was compared with the catalytic activity of the noble metal catalyst($Pt/{\gamma}-Al_2O_3$). Among the catalysts prepared with different Cu/Ce ratios, the catalyst whose Cu/Ce ratio was 4:16 showed the highest CO conversion (90%) and selectivity (60%) at $150^{\circ}C$. As the hydrolysis ratio was increased in the catalyst preparation, surface area increased, and catalytic activity also increased. The highest CO conversions with the CuO-$CeO_2$ mixed oxide catalyst prepared by the co-precipitation method and the noble metal catalyst (1wt% $Pt/{\gamma}-Al_2O_3$) were 82 and 81% at $150^{\circ}C$, respectively, whereas the highest CO conversion with the CuO-$CeO_2$ mixed oxide catalyst prepared by the sol-gel method was 90% at the same temperature. This indicates that the catalyst prepared by the sol-gel method shows higher catalytic activity than the catalysts prepared by the co-precipitation method and the noble metal catalyst. From the CO-TPD experiment, it was found that the catalyst having CO desorption peak at a lower temperature ($140^{\circ}C$) revealed higher catalytic activity.

• Korean Chemical Engineering Research
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• v.57 no.6
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• pp.758-762
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• 2019

Sodium borohydride,$NaBH_4$, has many advantages as hydrogen source for portable proton exchange membrane fuel cells (PEMFC). When PEMFC is used for marine use, $NaBH_4$ hydrolysis using seawater is economical. Therefore, in this study, hydrogen was generated by using seawater instead of distilled water in the process of hydrolysis of $NaBH_4$. Properties of $NaBH_4$ hydrolysis reaction using activated carbon supported Co-B/C catalyst were studied. The yield of hydrogen decreased as $NaBH_4$ concentration and NaOH concentration were increased during $NaBH_4$ hydrolysis using sea water. At higher concentrations of $NaBH_4$ and NaOH, byproducts adhered to the surface of the catalyst after hydrolysis reaction using sea water, reduced hydrogen yield compared to distilled water. The activation energy of $NaBH_4$ hydrolysis is 59.3, 74.4 kJ/mol for distilled water and sea water, respectively. In order to increase the hydrogen generation rate in seawater as high as distilled water, the reaction temperature has to be increased by $80^{\circ}C$ or more.

• Analytical Science and Technology
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• v.23 no.1
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• pp.45-53
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• 2010

For the determination of chlorine in uranium compound, analytical methods by using a steam distillation and a pyrohydrolysis have been developed. The steam distillation apparatus was composed of steam generator, distilling flask and condenser etc. The samples were prepared with an aliquot of LiCl standard solution and a simulated spent nuclear fuel. A sample aliquot was mixed with a solution containing 0.2 M ferrous ammonium sulfate-0.5 M sulfamic acid 3 mL, phosphoric acid 6 mL and sulfuric acid 15 mL. The chloride was then distilled by steam at the temperature of $140^{\circ}C$ until a volume of $90{\pm}5\;mL$ is collected. The pyrohydrolysis equipment was composed of air introduction system, water supply, quartz reaction tube, combustion tube furnace, combustion boat and absorption vessel. The chloride was separated from powdered sample which is added with $U_3O_8$ accelerator, by pyrohydrolysis at the temperature of $950^{\circ}C$ for 1 hour in a quartz tube with a stream of air of 1 mL/min supplied from the water reservoir at $80^{\circ}C$. The chlorides collected in each absorption solution by two methods was diluted to 100 mL and measured with ion chromatography to determine the recovery yield. For the ion chromatographic determination of chlorine in molten salt retained in a metal ingot, the chlorine was separated by means of pyrohydrolysis after air and dry oxidation, and grinding for the sample.

• Polymer(Korea)
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• v.34 no.3
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• pp.202-209
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• 2010

Aromatic copolyamides were prepared and their applicability to proton exchange membrane wasstudied. The copolymer contains thermally stable and mechanically strong poly(m-phenylene isophthalamide) segments, and easily processable and good film forming polysulfone segments. For the copolymer, amineterminated sulfonated ether sulfone monomer, m-phenylene diamine, and isophthaloyl chloride were reacted, and the obtained copolymer was transformed into crosslinkable prepolymer by the reaction with acryloyl chloride. The prepolymer was thermally cured and converted into proton exchange membranes for fuel cell application. Each reaction step and the molecular characteristics of precursor copolymers were monitored and confirmed by $^1H$ NMR, FTIR, and titration. The performance of the membranes was measured in terms of water uptake, proton conductivity, and thermal stability. The water uptake, ion exchange capacity (IEC), and proton conductivity of the membranes increased with the increase of sulfonated ether sulfone segment content. Membrane containing 30 mol% sulfonic acid sulfone segment showed 1.57 meq/g IEC value. Water uptake was limited less than 44 wt% and the highest proton conductivity up to $3.93{\times}10^{-2}S/cm$ ($25^{\circ}C$, RH= 100%) was observed.

• KSBB Journal
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• v.11 no.2
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• pp.151-158
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• 1996

For the effective ethanol fermentation, the high concentration of sugar as the substrate of microbial fermentation is required. The most important reason in the inefficient hydrolysis; the easy deactivation of enzyme by temperature or shear stress and the severe inhibition effects of its products. In our work, we comprehended the kinetic characteristics of cellulose and ${\beta}$-glucosidase in the progress of hydrolysis, and observed the potential inhibitory effects of the hydrolyzed products and the deactivation of enzymes. We also tried to present the kinetic model of enzymatic hydrolysis of cellulose, which is applicable to process at the high concentration of sugar. Cellulase and ,${\beta}$-glucosidase exhibit diverse kinetic behaviors. At a level of only 5g/$\ell$ of glucose, the ${\beta}$-glucosidase activity was reduced by more than 70%. This result means that ${\beta}$-glucosldase was the most severely inhibited by glucose. Also at l0g/$\ell$ of cellobiose, the cellulose lost approximately 70% of its activity. ${\beta}$-glucosldase was more sensitive to deactivation than cellulose by about 1.6 times. The comprehensive kinetic model in the range of confidence was obtained and the agreement between the model prediction and the experimental data was reasonably good, testifying to the validity of the model equations used and the associated parameters.