• Title/Summary/Keyword: Sodium borohydride($NaBH_{4}$)

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Performance Evaluation of Hydrogen Generator for Fuel Cell Unmanned Aircraft (연료전지 무인기 탑재용 수소발생기의 성능평가)

  • Park, Dae-Il;Kim, Sung-Uk;Kim, Dong-Min;Kim, Tae-Gyu
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.39 no.7
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    • pp.627-633
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    • 2011
  • Performance of a hydrogen generator for a fuel cell unmanned aircraft was evaluated as the change of temperature environment. Sodium borohydride ($NaBH_4$) was used as a hydrogen source due to its high hydrogen content and good storability. The hydrogen gas was generated by the hydrolysis reaction using a catalytic reactor. Reaction chambers were set up with the range of temperatures from -20 to $60^{\circ}C$. The hydrogen generation rate and temperatures changes of reactor and separator were measured at the $NaBH_4$ concentrations of 20 and 25wt.%. As a result, the hydrogen generation rate was decreased as the repeated reaction cycles. It showed that the hydrogen generation rate was stable at low temperature, while at high temperature the hydrogen generation rate was rapidly decreased. The performance degradation was mainly caused by the catalyst loss and $NaBO_2$ deposition on the catalyst surface.

Photo-enhanced Reduction of Conjugated Enones with NaBH$_4$

  • Shim, Sang-Chul;Yeo, Ho-Seop
    • Bulletin of the Korean Chemical Society
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    • v.8 no.3
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    • pp.202-205
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    • 1987
  • The reduction of some cyclic conjugated enones with electron-donating substituent on C-3 by sodium borohydride was accelerated on irradiation. The photo-enhanced reduction seems to undergo through zwitterionic species formed from the (n, ${\pi}^{\ast}$) triplet state of conjugated enones, followed by hydride attack to yield unsaturated or saturated alcohols.

Synthesis and Characterization of DNA-mediated Gold Nanoparticles by Chemical Reduction Method (화학적환원에 의한 DNA-mediated 금 나노입자의 합성 및 특성)

  • Sohn, Jun Youn;Sohn, Jeong Sun
    • Applied Chemistry for Engineering
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    • v.26 no.4
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    • pp.515-519
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    • 2015
  • Complexes composed of hydrogen tetrachloroaurate (III) trihydrate ($HAuCl_4{\cdot}3H_2O$) and DNA were first formed for the synthesis of gold nanoparticle using a DNA template, which were validated using UV-Vis spectroscopy. The morphology of complexes were also characterized by scanning electron microscopy (SEM). DNA-mediated gold nanoparticles were synthesized by the chemical reduction of DNA-Au(III) complexes using hydrazine ($N_2H_4$) and sodium borohydride ($NaBH_4$) as reducing agents. The effects of reducing agent types and their concentration on the formation of gold nanoparticles were investigated. The results showed that hydarazine was the most effective for the reduction of DNA-Au(III) complex. The DNA-mediated gold nanoparticles were characterized SEM, particle size analyzer (PSA), and transmission electron microscopy (TEM). Gold nanoparticles with 55~80 nm in diameter were formed by the aggregation of smaller gold nanoparticles (~nm), which was confirmed in the DNA matrix.

Performance Evaluation of Hydrogen Generation System using NaBH4 Hydrolysis for 200 W Fuel Cell Powered UAV (200 W급 연료전지 무인기를 위한 NaBH4 가수분해용 수소발생시스템의 성능평가)

  • Oh, Taek-Hyun;Kwon, Sejin
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.43 no.4
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    • pp.296-303
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    • 2015
  • The concentration of solute in a $NaBH_4$ solution is limited due to the low solubility of $NaBO_2$. The performance of a hydrogen generation system was evaluated using various concentrations of $NaBH_4$ solution. First, a self-hydrolysis test and a hydrogen generation test for 30 min were performed. The composition of $NaBH_4$ solution was selected to be 1 wt% NaOH + 25 wt% $NaBH_4$+74wt% $H_2O$ by considering the amount of hydrogen loss, stability of hydrogen generation, $NaBO_2$ precipitation, conversion efficiency, and the purpose of its application. A hydrogen generation system for a 200 W fuel cell was evaluated for 3 h. Although hydrogen generation rate decreased with time due to $NaBO_2$ precipitation, hydrogen was produced for 3 h (conversion efficiency: 87.4%). The energy density of the 200 W fuel cell system was 263 Wh/kg. A small unmanned aerial vehicle with this fuel cell system can achieve 1.5 times longer flight time than one flying on batteries.

Synthesis of Iron Nanopowder from FeCl3 Solution by Chemical Reduction Method for Recycling of Spent Neodymium Magnet (네오디뮴 폐자석 재활용을 위한 화학환원법을 이용한 철 나노 분말 제조)

  • Ha, Yonghwang;Gang, Ryun-Ji;Choi, Seung-Hoon;Yoon, Ho-Sung;Ahn, Jong-Gwan
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.13 no.12
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    • pp.6187-6195
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    • 2012
  • Recycling process of iron should be developed for efficient recovery of neodymium(Nd), rare metal, from acid-leaching solution of neodymium magnet. In this study, $FeCl_3$ solution as iron source was used for synthesis of iron nanoparticle with the condition of various factors, etc, reductant, surfactant. $Na_4O_7P_2$ and polyvinylpyrrolidone(PVP) as surfactants, $NaBH_4$ as reductant, and palladium chloride($PdCl_2$) as a nucleation seed were used. Iron powder was analyzed with instruments of XRD, SEM and PSA for measuring shape and size. Iron nanoparticles were made at the ratio of 1 : 5(Fe (III) : $NaBH_4$) after 30 min of reduction time. Size and shape of iron particles synthesized were round-form and 50 nm ~ 100 nm size. Zeta-potential of iron at the 100 mg/L of $Na_4O_7P_2$ was negative value, which is good for dispersion of metal particle. When $Na_4O_7P_2$(100 mg/L), PVP($FeCl_3$ : PVP = 1 : 4, w/w) and Pd($FeCl_3$ : $PdCl_2$ = 1 : 0.001, w/w) were used, iron nanoparticles which are round-shape, well-dispersed, near 100 nm-sized can be made.

Development of a Bottle-Free Multipurpose Incubator for Generating Various Bacterial Culture Conditions

  • Yang, Nam-Woong;Lim, Yong
    • Journal of Microbiology
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    • v.43 no.1
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    • pp.28-33
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    • 2005
  • The purpose of this study was to develop a multipurpose incubator, without the gas cylinders (bottles) which are required for $H_2$ and $CO_2$ supplementation. In our bottle-free multipurpose incubator, the $H_2$ and $CO_2$ were generated by chemical reactions induced within the chamber. The reaction between sodium borohydride and acetic acid at a molar ratio of 1:1 was used to generate $H_2$, according to the following formula: $4NaBH_4+2CH_3COOH+7H_2O{\rightarrow} 2CH_3COONa+Na_2B_4O_7+16H_2$, whereas the other reaction, citric acid and sodium bicarbonate at a 1:1 molar ratio, was used to generate $CO_2$, according to the following formula: $C_6H_8O_7+3NaHCO_3{\rightarrow}Na_3(C_6H_5O_7)+3H_2O+3CO_2$. Five species of obligate anaerobic bacteria, one strain of capnophilic bacterium, and one strain of microaerophilic bacterium were successfully cultured in the presence of their respective suitable conditions, all of which were successfully generated by our bottle-free multipurpose incubator. We conclude that, due to its greater safety, versatility, and significantly lower operating costs, this bottle-free multipurpose incubator can be used for the production of fastidious bacterial cultures, and constitutes a favorable step above existing anaerobic incubators.

Preliminary Study on Reaction Mechanism for Energy Generation using Hydride and Hydrogen Peroxide (수소화물과 과산화수소를 적용한 에너지 생성 메커니즘 연구)

  • Seo, Seong-Hyeon
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2012.05a
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    • pp.300-303
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    • 2012
  • Global warming has been a serious problem due to excessive emissions of carbon dioxide from the increase of energy consumption. The present study investigates an energy generation mechanism that does not produce carbon dioxide and oxides of nitrogen. A reaction mechanism including sodium borohydride and hydrogen peroxide has been introduced and as a result, thermal energy can be generated from combustion of hydrogen with oxygen. Sodium borohydride dissolved in water reacting with liquid hydrogen peroxide may reveal maximum adiabatic reaction temperature of 1795 K at a mixture ratio of 0.89.

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Asymmetric Reduction of 3-Ketoproline Ethyl Ester by Modified Borohydrides and Various Vegetables

  • Wibowo, Agustono;Shaameri, Zurina;Mohammat, Mohd Fazli;Hamzah, Ahmad Sazali
    • Journal of the Korean Chemical Society
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    • v.61 no.5
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    • pp.244-250
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    • 2017
  • Reduction of (${\pm}$)-3-ketoproline ethyl ester (1) by $NaBH_4$ in the presence of $CaCl_2$ and $MgCl_2$ as the chelating agents gave selective products cis-3(R/S)-alcohols, while reduction by $NaBH_4$ alone or chelated with $NiCl_2$ and $AlBr_3$ gave mixtures of cis- and trans-alcohols. The reduction of (${\pm}$)-1 by various vegetables however, gave exclusively the cis-alcohol as the major and trans-alcohol as the minor. On the contrary, reduction of (${\pm}$)-1 by carrot afforded a mixture of cis- and trans-alcohols, in which the trans-alcohol exists as the major product. In addition, we found that this biocatalyst selectively converted S-enantiomer of (${\pm}$)-1 to the cis-alcohol, and R-enantiomer to a mixture of cis- and trans-alcohols with cis-alcohol as the major product. This fact prompted us to use various fresh plant tissues for stereoselective reduction of diverse types of pyrrolidinones, as its stereoselectivity towards racemic mixtures is higher compared to that using chemical reducing agents.

Heterogeneous Catalysts for Hydrogen Generation Based on Ru-Incorporated Hydroxyapatite

  • Jaworski, Justyn Wayne;Kim, Dae-Hyun;Jung, Kyeong-Mun;Kim, So-Hue;Jeong, Jong-Ok;Jeon, Hyo-Sang;Min, Byoung-Koun;Kwon, Ki-Young
    • Proceedings of the Korean Vacuum Society Conference
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    • 2011.02a
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    • pp.319-319
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    • 2011
  • Hydrolysis of sodium borohydride provides a safe and clean approach to hydrogen generation. Having the proper catalytic support for controlling this reaction is therefore a valuable technology. Here we demonstrate the capability of hydroxyapatite as a novel catalytic support material for hydrogen generation. Aside from being inexpensive and durable, we reveal that Ru ion exchange on the HAP surface provides a highly active support for sodium borohydride hydrolysis, exemplifying a high total turnover number of nearly 24,000 mol $H_2$/ mol Ru. Moreover, we observe that the RuHAP support exhibits a high catalytic lifetime of approximately one month upon repeated exposure to $NaBH_4$ solutions. In addition to examining surface area effects, we also identified the role of complex surface morphology in enhancing hydrolysis by the catalytic transition metal covered surface. Particularly, we found that a polycrystalline RuHAP catalytic support exhibits shorter induction times for the initial bubble formation as well as increased hydrogen generation rates as compared to a single crystal supports. The independent factor of a complex surface morphology is believed to provide enhanced sites for gas release during the initial stages of the reaction. By demonstrating the ability to shorten induction time and enhance catalytic activity through changes in surface morphology and Ru content, we find it feasible to further explore this catalyst support in the construction of a practical hydrogen generator.

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