• 제목/요약/키워드: 환원적 분해반응

Search Result 200, Processing Time 0.023 seconds

Effect of the Preparation Method on the Activity of CeO2-promoted Co3O4 Catalysts for N2O Decomposition (촉매 제조방법에 따른 Co-CeO2 촉매의 N2O 분해 특성 연구)

  • Kim, Hye Jeong;Kim, Min-Jae;Lee, Seung-Jae;Ryu, In-Soo;Yi, Kwang Bok;Jeon, Sang Goo
    • Clean Technology
    • /
    • v.24 no.3
    • /
    • pp.198-205
    • /
    • 2018
  • This study investigated the influence of catalyst preparation on the activity of $Co-CeO_2$ catalyst for $N_2O$ decomposition. $Co-CeO_2$ catalysts were synthesized by co-precipitation and incipient wetness impregnation. In order to estimate the performance of the as prepared catalysts, direct catalytic $N_2O$ decomposition test was carried out under $250{\sim}375^{\circ}C$. As a result, the catalyst prepared by co-precipitation (CoCe-CP) showed an enhanced performance on $N_2O$ decomposition reaction even in the presence of $O_2$ and/or $H_2O$, whereas the impregnation catalyst (CoCe-IM) did not. In order to investigate the difference in catalytic activity, characterization such as XRD, BET, TEM, $H_2-TPR$, $O_2-TPD$, and XPS was conducted. It is confirmed that the particle size and specific surface area were changed depending on the catalyst preparation method and the synthesis process influenced the physical properties of the catalysts. In addition, the improvement in the activity of the catalyst prepared by co-precipitation is due to the enhanced reduction from $Co^{3+}$ to $Co^{2+}$ and the improved oxygen desorption rate. However, it has been confirmed that the surface electron state and binding energy, which are related to $N_2O$ decomposition, do not change depending on the preparation method.

Thermal and Physical Properties of Poly(butylene succinate)/Poly(${\varepsilon}$-caprolactone) Copolyesters Prepared by Transesterification (에스테르 교환반응으로 제조된 Poly(butylene succinate)/Poly(${\varepsilon}$-caprolactone) Copolyesters의 물리적 및 열적 성질에 관한 연구)

  • Yoo, Young-Tai;Yang, Su-Bong;Im, Seung-Soon
    • Polymer(Korea)
    • /
    • v.25 no.4
    • /
    • pp.486-495
    • /
    • 2001
  • Degradable poly(butylene succinate) (PBS)/poly(TEX>${\varepsilon}$-caprolactone) (PCL) copolyesters were prepared by using transesterification between poly(butylene succinate) and poly(TEX>${\varepsilon}$-caprolactone). The thermal and mechanical properties of copolyesters were investigated using differential scanning calorimetry and tensile testing. Interchange reaction between PBS and PCL molecules could be identified from proton NMR spectra. The reduced viscosity of the PBS/PCL copolyesters increased with reaction time except for a series of PBS/PCL (50/50 wt%) copolyesters. For all the compositions, the melting point and crystallization temperature of high-$T_m$ component (PBS) decreased as reaction time increased. From the results of tensile testing, it was found that stress and strain at break of the PBS/PCL copolymers containing less than 40 wt% PCL improved as compared to those of pure PBS, but at 50 wt% PCL stress at break of PBS/PCL copolymers was lowered due to decrease of crystallinity. On the other hand, Young's moduli of all the copolyesters decreased with both reaction time and PCL content.

  • PDF

Influence of Ca Reduction Process on the Properties of Nanocrystalline Nd-Fe-B Powders Prepared by a Thermochemical Process (열화학공정으로 제조된 나노결정형 Nd-Fe-B 분말의 특성에 미치는 Ca환원 공정의 영향)

  • Lee, Dae-Hoon;Jang, Tae-Suk;Yoo, J.-H.;Choi, C.-J.;Kim, B.-K.;Park, Byeong-Yeon
    • Journal of the Korean Magnetics Society
    • /
    • v.15 no.1
    • /
    • pp.42-47
    • /
    • 2005
  • Nanocrystalline Nd-Fe-B powder was synthesized by a new thermochemical process that combined with past reduction-diffusion process and spray-dry process. In this process, Ca reduction process is vary important due to formation of hard magnetic$Nd_{2}Fe_{14}B$ phase from various oxides by Ca powder. Therefore, the final products are essentially affected a shape, size, and composition etc. of the Ca reduced powders. Ca reduction was performed to way that raw powders just mixed with Ca powder in proper ratio unlike to compress into compact. The powders after mixture-type Ca reduction mainly composited with $Nd_{2}Fe_{14}B$ phase even relativily low reaction temperature ($800^{\circ}C$) and all particle size of powder were distributed less than 1 ${\mu}m$ except for powder after Ca oxides as magnetic properties of powders after cake-type Ca reduction, with the consequence that high magnetic properties has been expected. The magnetic properties of powders prepared by mixture-type Ca ruduction, with the conseqence that high magnatic properties has been expected. The magnetic properties of powders prepared by mixture-type Ca reduction process showed $_iH_c$ = 5.9 kOe, $B_r$ = 5.5 kG, (BH)max = $Nd_{2}Fe_{14}B{\to}Nd_{2}Fe_{17}B$ decomposition by violent exothermic reaction during washing.

Synthesis of Long-Chain Unsaturated Acetates (장직쇄상(長直鎖狀) 불포화(不飽和) 초산화합물(醋酸化合物)의 합성(合成)에 관(關)한 연구(硏究))

  • Oh, Sung-Ki
    • Applied Biological Chemistry
    • /
    • v.19 no.1
    • /
    • pp.1-23
    • /
    • 1976
  • The female moths of Lepidoptera comprising over 1,000,000 described species possess long-chain unsaturated alcohols or esters as the typical structure of potential sex attractants. In this experiment, various stereoisomers of $C_{16}-unsaturated$ acetates were synthesized for potential sex attractants; e.g., $CH_3(CH_2)_mCH=CH(CH_2)_nOR$ (m=0-12, n=1-13, R=H and $-COCH_3$). Seventeen acetates were spectrometrically examined so that the data would provide a ready catalog of gas chromatography and mass spectrometric data for comparison with natural insect sex attractants. Exclusively cis and trans isomers were obtained by the catalytic and chemical reduction methods, respectively. Commercially available $CH_3(CH_2)_mBr,\;CH_3(CH_2)_mC{\equiv}CH,\;HC{\equiv}C(CH_2)_nOH\;and\;HO(CH_2)_n\;OH$ were used for the synthetic starting material. 1-Alkynes, $CH_3(CH_2)_m\;C{\equiv}CH$ exceeding nine methylene groups did not condense with alkyl dihalides. The yield of coupling products was gradually decreased with increasing the molecular weight of diols. In the coupling reaction of $BrCH_2CH_2$ OTHP with acetylene gas, the tetrahydropyranyl ether of bromohydrin produced undesirable elimination product. In this experiment, it seems that p-toluenesulfonic acid is greatly favoured hydrolyzing agent over dilute sulfuric acid in the hydrolysis of the tetrahydropyranyl ether of long-chain alkynols.

  • PDF

Direct Conversion of L-Selenomethionine into Methylselenol by Human Cystathionine ${\gamma}$-Lyase (인간 Cystathionine ${\gamma}$-Lyase에 의한 Selenomethionine의 Methylselenol로의 직접분해)

  • Cho, Hyun-Nam;Jhee, Kwang-Hwan
    • Microbiology and Biotechnology Letters
    • /
    • v.42 no.1
    • /
    • pp.11-17
    • /
    • 2014
  • Selenium is an essential trace element for mammals, but it is very toxic. Therefore, the control of selenium concentrations should be precisely and effectively monitored. Selenium is naturally obtained through foods and seleno-L-methionine (LSeMet) is a major form of selenium. It has been reported that L-SeMet is only converted into Se-adenosyl-L-SeMet. However, a recent study suggested that L-SeMet was directly metabolized into methylselenol ($CH_3SeH$) in mouse liver extract by the reaction of cystathionine ${\gamma}$-lyase (CGL). The canonical reaction of CGL was known to catalyze the cleavage of L-cystathionine to L-cysteine, ${\alpha}$-ketobutyrate and $NH_3$. In the present study, we found that L-SeMet could be directly converted to $CH_3SeH$ using purified homogenous human CGL instead of mouse liver cytosol. Authentic $CH_3SeH$ was prepared by reduction of dimethyldiselenide with sodium tetrahydroborate. The gaseous product of the enzymatic reaction with L-SeMet was analyzed by GC/MS spectrometry. The GC/MS data was identical to that of authentic dinitrophenyl selenoether. We also analyzed the kinetic parameters for the formation of $CH_3SeH$ from L-SeMet by human and mouse CGL. These results suggest that human CGL is a critical enzyme which is responsible for L-SeMet metabolism.

Synthesis and Characteristics of Aminated Poly(arylene ether sulfone) as Thermostable Anion Exchanger (내열성 음이온교환수지로서 Aminated Poly(arylene ether sulfone)의 합성과 물성)

  • 손원근;유현지;황택성;김동철;김상헌;송해영
    • Polymer(Korea)
    • /
    • v.26 no.1
    • /
    • pp.1-8
    • /
    • 2002
  • In this study, poly(arylene ether sulfone) (PAES) having thermal stability and excellent mechanical properties was synthesized to be useful for the matrix of anion exchange resin. $1^{\circ}$-Aminated poly(arylene ether sulfone) ($1^{\circ}$-APAES) was prepared by reduction reaction after lithiation of PAES. Then $3^{\circ}$-APAES was Prepared by alkylation of the amino group of $1^{\circ}$-APAES. The structures of PAES and APAESs were confirmed with FT-IR and $^1H-NMR$ spectroscopy. Also, thermal properties of the resins were characterized by DSC and TG analysis. The introduction of amine groups in PAES resulted in the increase of glass transition temperature and decrease of initial thermal degradation temperature. The ion exchange capacities of $1^{\circ}$-APAES and $1^{\circ}$-APAES were 1.19 and 1.45 meq/g, respectively.

Electrochemical Behaviors of Graphite/LiNi0.6Co0.2Mn0.2O2 Cells during Overdischarge (흑연과 LiNi0.6Co0.2Mn0.2O2로 구성된 완전지의 과방전 중 전기화학적 거동분석)

  • Bong Jin Kim;Geonwoo Yoon;Inje Song;Ji Heon Ryu
    • Journal of the Korean Electrochemical Society
    • /
    • v.26 no.1
    • /
    • pp.11-18
    • /
    • 2023
  • As the use of lithium-ion secondary batteries is rapidly increasing due to the rapid growth of the electric vehicle market, the disposal and recycling of spent batteries after use has been raised as a serious problem. Since stored energy must be removed in order to recycle the spent batteries, an effective discharging process is required. In this study, graphite and NCM622 were used as active materials to manufacture coin-type half cells and full cells, and the electrochemical behavior occurring during overdischarge was analyzed. When the positive and negative electrodes are overdischarged respectively using a half-cell, a conversion reaction in which transition metal oxide is reduced to metal occurs first in the positive electrode, and a side reaction in which Cu, the current collector, is corroded following decomposition of the SEI film occurs in the negative electrode. In addition, a side reaction during overdischarge is difficult to occur because a large polarization at the initial stage is required. When the full cell is overdischarged, the cell reaches 0 V and the overdischarge ends with almost no side reaction due to this large polarization. However, if the full cell whose capacity is degraded due to the cycle is overdischarged, corrosion of the Cu current collector occurs in the negative electrode. Therefore, cycled cell requires an appropriate treatment process because its electrochemical behavior during overdischarge is different from that of a fresh cell.

Problems and Solutions of Zymography Techniques (자이모그라피 기술의 문제점과 해결)

  • Kang, Dae-Ook;Choi, Nack-Shick
    • Journal of Life Science
    • /
    • v.29 no.12
    • /
    • pp.1408-1414
    • /
    • 2019
  • Enzymes are widely used in industrial applications such as detergents, food, feed production, pharmaceuticals and medical applications and major contributors to clean industrial products and processes. To screen, identify, and characterize the enzymes the zymography techniques are routinely used. The zymography technique is a simple, sensitive, and quantifiable technique that is widely used to detect functional enzymes following electrophoretic separation in sodium dodecyl sulfate (SDS)-polyacrylamide gels. The method is a versatile two-stage technique involving protein separation by electrophoresis followed by the detection of enzyme activity in polyacrylamide gels under non-reducing conditions. It is based on SDS-polyacrylamide gel (PAG) copolymerization with substrates, which are degraded by the hydrolytic enzymes restored in enzyme reaction buffer after the electrophoretic separation. Any kind of biological sample can be applied and analyzed on zymography, including culture supernatants of microbes, plants extracts, blood, tissue culture fluids, enzymes in foods extracts and metaproteome. The advantage of zymography is that it is possible to directly detect the protein with activity on the electrophoretic gel as well as confirm the activity at the nanogram level. Thus, this zymography technology can be applied in various fields. However, these advantages are rather disadvantageous and can often lead to experimental errors. In this review, the advantages, disadvantages, and problem solving of zymography technique are described.

The Effect of Electrode Spacing and Size on the Performance of Soil Microbial Fuel Cells (SMFC) (전극간 거리와 크기가 토양미생물연료전지의 성능에 미치는 영향)

  • Im, Seong-Won;Lee, Hye-Jeong;Chung, Jae-Woo;Ahn, Yong-Tae
    • Journal of Korean Society of Environmental Engineers
    • /
    • v.36 no.11
    • /
    • pp.758-763
    • /
    • 2014
  • Soil microbial fuel cells (SMFC) have gained a great attention as an eco-friendly technology that can simultaneously generate electricity and treat organic pollutants from the contaminated soil. We evaluated the effect of electrode spacing and size on the performance of SMFC treating soil contaminated with organic pollutants. Maximum power density decreased with increase in electrode distance or decrease in electrode size, likely due to higher internal resistance. The maximum voltage and power density decreased from 326 mV and $19.5mW/m^2$ with 4 cm of electrode distance to 222 mV and $5.9mW/m^2$ with 9 cm of electrode distance. In case of electrode size test, the maximum voltage and power density generated was 291 mV, $0.34mW/m^3$ when both of anode and cathode area were $64cm^2$ with 4 cm of electrode distance. The maximum voltage decreased by 19~29% when the anode area decreased to $16cm^2$ while only 3~12% of voltage decreased with cathode area decrease. The maximum power density decreased by 49~68% with decreasing anode size, and by 29~47% with decreasing cathode size. These results showed that the anode area had more significant effects than the cathode area on the power generation of SMFC which has a high internal resistance due to a coexistence of soil and wastewater in the reactor.

An Electro-Fenton System Using Magnetite Coated One-body Catalyst as an Electrode (일체형 산화철 촉매를 전극으로 하는 전기펜톤산화법)

  • Choe, Yun Jeong;Ju, Jeh Beck;Kim, Sang Hoon
    • Applied Chemistry for Engineering
    • /
    • v.29 no.1
    • /
    • pp.117-121
    • /
    • 2018
  • A stainless steel mesh was applied to the cathode of an electro-Fenton system. Methylene blue (MB) solution was chosen as the model waste water with non-biodegradable pollutants. For the model waste water, the degradation efficiency was compared among various SUS mesh cathodes with different surface treatments and magnetite coatings on them. With increasing amount of the magnetite coating on SUS mesh, the degradation efficiency also increased. The improved electro-catalytic characteristic was explained by the increased amount of in situ generated hydrogen peroxide near the cathode surface. Cyclic voltammetry data also showed improved electro-catalytic performance for SUS mesh with more magnetite coatings on them.