• KSBB Journal
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• v.14 no.6
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• pp.742-746
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• 1999

The microalgal, Chlorella sp. HA-1, had good $CO_2$ fixation efficiency compared to other algal strains at the same operating condition. In this study, Chorella sp. HA-1 showed similar tolerance both 10% and 20% $CO_2$ concentration. By optimization of the major operation variables such as pH, initial cell concentration, light intensity, the $CO_2$ fixation rate could be raised to a reasonably high value, 372 $gCO_2/m^2{\cdot}day$ in a 3 L internally illuminated photobioreactor. In order to maintain the $CO_2$ fixation rate for a long time, the method of semi-continuous operation was employed, in which dilution ratio was the controlling parameter. Starting with the dilution ratio of 0.5 with the increased increment of 0.1, the constant $CO_2$ fixation rate was obtained.

• Applied Chemistry for Engineering
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• v.10 no.1
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• pp.129-134
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• 1999

This study is related to the investigation of the direct incorporation of $CO_2$ to polymer using quaternary ammonium salt catalysts. Quaternary ammonium salts showed good catalytic activity of $CO_2$ fixation in the synthesis of poly[(1,3-dioxolane-2-oxo-4-yl)methyl methacrylate] [poly(DOMA)] by the direct incorporation of $CO_2$ to poly(glycidyl methacrylate)[poly(GMA)]. Among the salts tested, the ones with higher alkyl chain length and with more nucleophilic counter anion showed higher catalytic activity. The yield of carbon dioxide addition increased with the reaction temperature. Kinetic study was carried out by measuring the variation of $CO_2$, pressure in a high pressure batch reactor. The reaction rate was first order to the concentration of poly(GMA) and $CO_2$, respectively. The rate constant was $0.69L/mol{\cdot}h$ and Henry's constant of $CO_2$ in DMSO at $80^{\circ}C$ was $6.8{\times}10^{-4}mol/L{\cdot}KPa$.

• Korean Journal of Food Science and Technology
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• v.27 no.4
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• pp.564-570
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• 1995

N-Benzoyl-L-aspartyl-L-phenylalanine methyl ester(BzAPM), a novel aspartame precursor, was investigated for its enzymatic synthesis by immobilized thermolysin using a water-miscible organic solvent system. The substrate used were N-benzoyl-L-aspartic acid(BzAsp) and L-phenylalanine methyl ester (PheOMe). Synthetic conditions such as substrates concentration, temperature, pH, and some metallic ions were varied to study their effects on BzAPM synthesis. The synthetic reaction rate increased linearly as the PheOMe concentration increased at a constant concentration of BzAsp(100 mM), and the maximum reaction rate was obtained at BzAsp concentration of 200 mM when 300 mM PheOMe was used. The optimum pH and temperature were found to be 6.1 and $40^{\circ}C$, respectively. The metallic ions such as $Zn^{2+},\;Mg^{2+},\;Mn^{2+},\;Fe^{2+},\;Pb^{2+}\;and\;Cu^{2+}$ at 5 mM level showed inhibitory effect on BzAPM synthesis, while $Co^{2+}$ and $Ca^{2+}$ ion increased synthesis. $Co^{2+}$ ion was also found to have synergistic effect with $Ca^{2+}$ ion. Benzoic acid, L-phenylalanin and NaCl showed inhibitory effect.

• Applied Chemistry for Engineering
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• v.4 no.1
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• pp.144-152
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• 1993

Immobilized polyethylene glycols onto metal oxides such as ${\gamma}-Al_2O_3$, ${\alpha}-Al_2O_3$, $SiO_2$ and $TiO_2$ were used as phase transfer catalysts for the room temperature synthesis of aniline from nitrobenzene and ironpentacarbonyl. The amount of attached PEG molecules increased with specific surface area of metal oxides. Among the immobilized catalysts tested PEG/${\gamma}-Al_2O_3$ showed the highest activity. The reaction rate increased with the chain length of PEG mole-cules and the aqueous NaOH concentration. Mechanistic study carried out using infrared spectrometer revealed that the role of PEG was to increase the formation of $HFe(CO)_4{^-}$ ion, which is known as active species, and its movement from aqueous to organic phase.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.8
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• pp.663-672
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• 2009

In this studies, the adsorption test using Chlorella pyrenoidosa was conducted to examine the effect of Pb adsorption according to various immobilized methods such as Ca-alginate, K-carrageenan, and Polyacrylamide. From the results, the duration to need to reach adsorption equilibrium was delayed according to the immobilization. And, the higher adsorption capacity of immobilized Chlorella pyrenoidosa was represented in the higher concentration of Pb, the smaller amount of immobilizing agent, and the higher pH of solution. The maximum adsorption capacity of Pb was shown in the adsorption test using Chlorella pyrenoidosa immobilized with Ca-alginate even though it was sensitive pH. The adsorption results properly represented with Freundlich isotherm equations. And, pseudo second-order chemisorption kinetic rate equation was applicable to all the biosorption data over the entire time range. The FT-IR analysis showed that the mechanism involved in biosorption of Pb by Chlorella pyrenoidosa was mainly attributed to Pb binding of carbo-acid and amide group. Adsorbed Pb on immobilized Chlorella prenoidosa was easily desorbed in the higher concentration of desorbents(NTA, HCl, EDTA, $H_2SO_4,\;Na_2CO_3$). Among the several desorbents, NTA showed the maximum desoption capacities of Pb from Chlorella pyrenoidosa immobilized with Ca-alginate and K-carrageenan and EDTA was the most effective in Chlorella pyrenoidosa immobilized with polyacrylamide. The desoprtion efficiency in the optimum condition was 90.0, 83.0, and 80.0%, respectively.

• Journal of Energy Engineering
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• v.22 no.4
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• pp.347-354
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• 2013

This study was carried out to examine different mole ratio of $H_2/CO_2$ and EBCT using the continuous system in the lab scale throughout biological methods with accumulated hydrogenotrophic methanogen that can convert $CO_2$ to $CH_4$. The experimental-based results with various gas mixtures of mole ratio of 4:1($H_2/CO_2$) and 5:1($H_2/CO_2$), $H_2$ was converted more than 99% conversion rate. In case of $CO_2$, 4:1($H_2/CO_2$) and 5:1($H_2/CO_2$) were $74.45{\pm}0.33%$, $95.8{\pm}10.7%$, respectively, in addition, the study was confirmed that the amount of $H_2$ was more needed than stoichiometric equations, where approach methods are empirical versus theoretical frameworks, for converting total $CO_2$. As such, we have noticed that $H_2$ was used for energy source of hydrogenotrophic methanogen for maintaining life. Regarding the results of the ratio of treatment by retention time, limitation of treatment capacity showed that $H_2$(99.9%) and $CO_2$(96.23%) at EBCT 3.3 hrs indicated stable conversion ratio, as well as appeared that methane production rate and $CO_2$ fixation rate were investigated $1.15{\pm}0.02m^3{\cdot}m^{-3}{\cdot}day^{-1}$ and $2.01{\pm}0.04kg{\cdot}m^{-3}{\cdot}day^{-1}$, respectively.

• Korean Journal of Food Science and Technology
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• v.29 no.5
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• pp.969-973
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• 1997

In order to produce transglucosylated steviosides continuously, some types of bioreactors were investigated with cyclodextrin glucanotransferase immobilized on a high porous anion exchange resin, Diaion HPA75. Among the bioreactors, the packed-bed reactor (PBR) showed the highest specific productivity. The effect of linear velocity in a PBR on the stevioside conversion was not significant in the range of $10{\sim}60\;cm/hr$ at the same space velocity of $1.2\;hr^(-1)$. When the space velocity of bioreactor was varied from 0.2 to $1.1\;hr^{-1}$, the optimal velocity of substrate solution was determined as $0.7\;hr^(-1)$. The stevioside conversion of more than 70% was maintained during 20 days in the continuous operation, if about 20% of immobilized enzyme was replaced in the top of reactor after two weeks operation as the one of the control methods in bioreactor. The specific production, which refers to as the amount of commercially valuable transglucosylated steviosides produced by a unit amount of immobilized cyclodextrin glucanotransferase, was found to be ca. 150g product/g immobilized enzyme.

• Journal of Wetlands Research
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• v.20 no.4
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• pp.363-369
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• 2018

One of the recent environmental problems is climate change due to the increase of atmospheric $CO_2$, which causes ecological changes and various environmental problems. Therefore, various studies are being carried out to reduce $CO_2$ in the world in order to solve various environmental problems caused by increase of $CO_2$. The $CO_2$ reduction using microalgae is an environmentally friendly method by using photosynthesis reaction of microalgae. However, most studies using single species. There is no study on the $CO_2$ fixing efficiency of microalgae in natural rivers. Therefore, this study was to identify the microalgae in the Sum river and to analyze the growth characteristics of microalgae in the river to obtain optimal culture conditions. And the changes of biomass and chlorophyll-a of microalgae were analyzed according to $CO_2$ concentration and injection rate. The purpose of this study was to investigate the fixing efficiency of carbon dioxide in microalgae in natural rivers. Six kinds of dominant species were observed as a result of the identification of microalgae in Sum river(Ankistrodesmus falcatus, Scenedesmus intermedius, Selenodictyum sp., Xanthidium apiculatum var. laeve, Cosmarium pseudoquinarium, Dictyosphaerium pulchellum). All of these species were green algae. Biomass and chlorophyll-a increased with the increase of $CO_2$ concentration and biomass and chlorophyll-a increased faster flow rate at the same $CO_2$ concentration. Also, the quantity of $CO_2$ fixation on the microalgae tended to be higher when the flow rate of injected gas was faster. This study can be referred as being significant in the micro-algae in river. In addition, the optimal conditions for $CO_2$ fixation of microalgae in rivers and the quantification of the quantity of $CO_2$ fixation from microalgae in rivers can be used as basic data for future policy of $CO_2$ reduction.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1996.06b
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• pp.3-27
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• 1996

분체의 입자 배열이 불규칙한 경우뿐만 아니라 입자 크기가 극미세하여 X선회절분석이 불가능한 경우에도 비정질물질이라 한다. 수용액 속에서 이런 비정질 물질을 합성하기 위해서는 합성용액의 과포화도를 높여 계속 유지시킴에 따라 극미세 1차핵 생성의 지속적인 유도에 따른 입자 성장을 최대한 억제시켜야만 한다. 본 연구에서는 흡습제, 칼슘제 및 식품 첨가제 등으로 이용되는 비정질 탄산칼슘을 계에서 합성하고, 이때 생성된 비정질 상태의 겔을 수용액 환경을 변화시켜가면서 따라 결정화를 유도하고 탄산칼슘의 동질이상을 관찰하였다. CO2의 유속을 11/min, 교반속도를 600rpm으로 고정시키고, Ca(OH)2의 양을 10g에서 50g까지 변화시켜가면서 겔 상태의 비정질 탄산칼슘을 합성하였다. 이때 전기전도도는 CO2의 용해와 더불어 Ca(OH)2의 용해도가 증가함에 따라 변화하였으며, 반응종반부에는 겔화가 시작될 때까지 거의 일정하였다. 따라서, 이러한 사실들로부터 현탁액 내에서의 전기전도도의 변화는 Ca이온의 영향을 받는 것으로 사료된다. 비정질 탄산칼슘은 수용액에서 불안정하여 CO2 가스를 방출하면서 급격히 결정화되는데, 본 연구에서는 Ca(OH)2의 양을 20g으로 하여 위의 방법에 의해 얻어진 겔을 수용액의 종류와 농도 및 결정화 온도, 교반속도를 달리하면서 결정화시켰다. 교반속도를 100rpm으로 하여 물의 온도변화에 다라 결정화시킨 경우 전 온도범위에서 칼사이트상이었으며, 물의 온도가 5$^{\circ}C$일 경우에는 미세한 입자들이 응집된 형태였으나, 그 외의 온도변화조건에서는 모두 평균입경 0.4$\mu\textrm{m}$정도의 비교적 균일하 능면체 형태였다. 또한 교반속도를 500rpm으로 증가시켰을 경우에는 8$0^{\circ}C$에서 침상의 아라코나이트가 소량생성되었음을 SEM사진으로 관찰할 수 있었으며, 소량의 바테라이트도 혼재되어 결정화되었음을 XRD결과로 알 수 있었다. 교반속도를 100rpm으로 한 NH4Cl 0.5mol/l 수용액에서는 입자의 형태와 크기가 불규칙한 칼사이트로 결정화되었으며, MgCl2 0.05mol/l 수용액의 경우에는 순수한 H2O의 경우에서와는 달리 2$0^{\circ}C$에서는 모서리가 무딘 매우 균일한 크기의 칼사이트 입자가 관찰되었으며, 6$0^{\circ}C$부터는 아라고나이트가 생성됨을 관찰할 수 있었다. 따라서, 고온(8$0^{\circ}C$)의 농도 MgCl2 수용액(0.1, 0.2 mol/l)에서 교반속도를 높여(800rpm) 겔을 결정화시킨 결과 아라고나이트의 생성수율이 증가되는 것을 확인할 수 있었다.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.129.1-129.1
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• 2010

석탄가스화로부터 얻어진 합성가스는 CO, $H_2$가 주성분으로, 그 자체를 연료로 사용하여 발전을 하거나 또는 적절한 정제, 분리 및 합성을 통해 다양한 원료물질을 생산할 수 있다. 이러한 석탄의 청정 사용 기술은 최근의 에너지 분야에서 많은 관심을 불러일으키고 있는 고유가 현상 및 석유자원 고갈에 대비할 수 있는 현실적인 방법의 하나로 여겨지고 있다. 석유를 대체할 에너지원으로서 석탄을 이용하는 다양한 응용 방법 중의 하나로 가스화 반응을 통해 발생하는 합성가스를 이용한 SNG 제조 공정을 들 수 있는데, 이는 석탄 등의 고체 시료를 이용하여 메탄이 주성분인 연료가스를 생산하는 것이다. SNG(Synthesis Natural Gas 또는Substitute Natural Gas)는 합성천연가스 또는 대체천연가스로 불리어지는데 주로 석탄의 가스화를 통해 얻어진 합성가스(syngas 또는 synthesis gas)인 CO, $H_2$를 촉매에 의한 합성반응을 통해 얻을 수 있다. SNG 합성 반응(메탄화 반응)은 보통 수성가스 전환 공정과 가스 정제 공정을 거친 합성가스를 $CH_4$로 전환하는 것으로 석탄을 이용한 SNG 제조 공정에서 가장 핵심 공정인 메탄화 반응은 높은 발열반응으로 주로 니켈 촉매를 사용하며 $250{\sim}400^{\circ}C$에서 반응이 이루어진다. SNG 합성 반응은 공급되는 합성가스의 조성($H_2$/CO 비), 공급되는 합성가스의 유량과 반응기에 충진된 촉매의 부피와의 관계를 나타낸 공간속도, 반응온도 등의 조건에 따라 반응 특성이 달라질 수 있다. 가스화 반응을 통해 생성되는 합성가스를 이용한 SNG 합성반응(메탄화 반응)의 특성을 파악하기 위하여 Lab-scale 규모의 고정층 반응기를 이용하여 Ni 함량이 다른 2종류의 촉매를 대상으로 반응온도 및 압력에 따른 CO 전환율, $CH_4$ 선택도, $CH_4$ 생산성 변화를 파악하였다. 실험 결과 반응기의 온도가 350도 이상의 조건에서 CO 전환율은 99.8%이상, $CH_4$ 선택도는 90.7%이상으로 나타났으며, 공간속도가 2,000 1/h 이상의 조건에서는 $CH_4$ 생산성이 500 ml/g-cat, h을 만족하였다.