• Transactions of the Korean hydrogen and new energy society
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• v.26 no.4
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• pp.339-346
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• 2015

The synthesis of Fischer-Tropsch (FT) oil is the catalytic hydrogenation of CO to give a range of products, which can be used for the production of high-quality diesel fuel, gasoline and linear chemicals. This studied catalyst was prepared Cobalt-supported alumina and silica by the incipient wet impregnation of the nitrates of cobalt, promoter and organic solvent with supports. Cobalt catalysts were calcined at $350^{\circ}C$ before being loaded into the FT reactors. After the reduction of catalyst has been carried out under $450^{\circ}C$ for 24h, FT reaction of the catalyst has been carried out at GHSV of 4,000/hr under $200^{\circ}C$ and 20atm. From these experimental results, we have obtained the results as following; In case of $SiO_2$ catalysts, the activity of 12wt% $Cobalt-SiO_2$ synthesized by organic solvent was about 2 or 3 times higher than the activity of 12wt% $Cobalt-SiO_2$ catalyst synthesized without organic solvent. In particular, the activity of the $Cobalt-SiO_2$ catalyst prepared in the presence of an organic solvent P was two to three times higher than that of the $Cobalt-SiO_2$ catalyst prepared without the organic solvent. Effect of Cr and Cu metal as a promoter was found little. 200 h long-term activity test was performed with a $Co/SiO_2$ catalyst prepared in the presence of an organic solvent of Glyoxal solution.

• Transactions of the Korean hydrogen and new energy society
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• v.25 no.2
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• pp.114-121
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• 2014

The synthesis of Fischer-Tropsch oil is the catalytic hydrogenation of CO to give a range of products, which can be used for the production of high-quality diesel fuel, gasoline and linear chemicals. Our cobalt catalyst was prepared Co/alumina, Co/silica and Co/titania by the incipient wetness impregnation of the nitrates of cobalt with supports. Co-based catalysts was calcined at $400^{\circ}C$ before being loaded into the FT reactors. After the reduction of catalyst has carried out under $450^{\circ}C$, FT reaction of the catalyst has carried out at GHSV of 4,000 under $200^{\circ}C$ and 20atm. From test results, the order of increasing activity for the catalyst was Co/alumina > Co/silica > Co/titania. When the content of Co metal such as 5, 12, 20 and 30wt% was changed, an CO conversion increased as the content of Co metal increased. The activity of catalyst has obtained the best value at 12wt% Co content.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.2
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• pp.147-150
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• 2020

Relatively pure YBCO was first synthesized by heating a mixture of metal carbonates at temperatures between 1,000 and 1,300 K, resulting in the reaction: 4BaCO₃+Y₂(CO₃)₃+6CuCO₃+(1/2_-x)O₂ → 2YBa₂Cu₃O_7-x+1/3CO₂. Modern syntheses of YBCO use the corresponding oxides and nitrates. The superconducting properties of YBa₂Cu₃O_7-x are sensitive to the value of x, i.e., its oxygen content. Only those materials with 0≤x≤0.65 are superconducting below Tc, and when x ~ 0.07, the material superconducts at the highest temperature, i.e., 95 K, or in the highest magnetic fields, i.e., 120 T and 250 T when B is perpendicular and parallel to the CuO₂ planes, respectively. In addition to being sensitive to the stoichiometry of oxygen, the properties of YBCO are influenced by the crystallization methods applied. YBCO is a crystalline material, and the best superconductive properties are obtained when crystal grain boundaries are aligned by careful control of annealing and quenching temperature rates. However, these alternative methods still require careful sintering to produce a quality product. New possibilities have arisen since the discovery of trifluoroacetic acid, a source of fluorine that prevents the formation of undesired barium carbonate (BaCO₃). This route lowers the temperature necessary to obtain the correct phase at around 700℃. This, together with the lack of dependence on vacuum, makes this method a very promising way to achieve a scalable YBCO bulk.

• Advances in environmental research
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• v.2 no.1
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• pp.19-33
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• 2013

Microalgae are receiving an increasing attention because of their potential use as $CO_2$ capture method and/or as feedstock for biofuels production. On the other hand the current microalgae-based technology is still not widespread since it is characterized by technical and economic constraints that hinder its full scale-up. In such contest the growth kinetics of Nannochloris eucaryotum (a relatively unknown marine strain) in batch and semi-batch photobioreactors is quantitatively investigated with the aim of obtaining the corresponding kinetic parameters suitable for process engineering and its optimization. In particular the maximum growth rate was evaluated to be 1.99 $10^{-3}\;h^{-1}$. Half saturation concentrations for nitrates ($K_N$) and phosphates uptake ($K_P$) were evaluated as 5.4 $10^{-4}\;g_N\;L^{-1}$ and 2.5 $10^{-5}\;g_P\;L^{-1}$, respectively. Yield factors for nitrogen ($Y_N$) and phosphorus ($Y_P$) resulted to be 5.9 $10^{-2}\;g_N\;g^{-1}$ biomass and 6.0 $10^{-3}\;g_P\;g^{-1}{_{biomass}}$, respectively. The possibility of using 100% (v/v) $CO_2$ gas as carbon source is also evaluated for the first time in the literature as far as N. eucaryotum is concerned. The strain showed a good adaptability to high concentrations of dissolved $CO_2$ as well as to low pH. The lipid content under 100% $CO_2$ is about 16.16 %wt $wt^{-1}$ and the fatty acid methyl esters composition of the extracted oil is in compliance with the European regulation for quality biodiesel.

• Journal of Korean Society for Atmospheric Environment
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• v.24 no.5
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• pp.594-603
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• 2008

A single particle analytical technique, named low-Z particle electron probe X-ray microanalysis, was applied to characterize four samples collected at an underground shopping area connected to Dongdeamun subway station, in January and May 2006. Based on the analysis of their chemical compositions of the samples, many distinctive particle types are identified and the major chemical species are observed to be soil-derived particles, iron-containing particles. sulfates. nitrates, and carbonaceous particles. which are encountered both in coarse and fine fractions. Carbonaceous particles exist in carbon-rich and organic. Soil derived particles such as aluminosilicates, AlSi/C, $CaCO_3\;and\;SiO_2$ are more frequently encountered in spring samples than winter samples. Nitrate- and sulfate-con taming particles are more frequently encountered in winter samples, and those nitrate- and sulfate-containing particles mostly exist in the chemical forms of $Ca(CO_3,\;NO_3),\;Ca(NO_3,\;SO_4),\;(Na,\;Mg)NO_3\;and\;(Mg,\;Na)(NO_3,\;SO_4)$. Fe-containing particles which came from nearby subway platform are in the range of about 10% relative abundances for all the samples. It is observed that nitrate- and sulfate-containing particles and carbonaceous particles are much more frequently encountered in indoor aerosol samples than in outdoor aerosols, implying that $NO_x,\;SO_x$, and VOCs at the underground shopping area were more partitioned into aerosol phase.

• Korean Journal of Materials Research
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• v.20 no.10
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• pp.508-512
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• 2010

The optimum route to fabricate nano-sized Fe-50 wt% Co and hydrogen-reduction behavior of calcined Fe-/Conitrate was investigated. The powder mixture of metal oxides was prepared by solution mixing and calcination of Fe-/Co-nitrate. A DTA-TG and microstructural analysis revealed that the nitrates mixture by the calcination at $300^{\circ}C$ for 2 h was changed to Fe-oxide/$Co_3O_4$ composite powders with an average particle size of 100 nm. The reduction behavior of the calcined powders was analyzed by DTA-TG in a hydrogen atmosphere. The composite powders of Fe-oxide and Co3O4 changed to a Fe-Co phase with an average particle size of 40 nm in the temperature range of $260-420^{\circ}C$. In the TG analysis, a two-step reduction process relating to the presence of Fe3O4 and a CoO phase as the intermediate phase was observed. The hydrogen-reduction kinetics of the Fe-oxide/Co3O4 composite powders was evaluated by the amount of peak shift with heating rates in TG. The activation energies for the reduction, estimated by the slope of the Kissinger plot, were 96 kJ/mol in the peak temperature range of $231-297^{\circ}C$ and 83 kJ/mol of $290-390^{\circ}C$, respectively. The reported activation energy of 70.4-94.4 kJ/mol for the reduction of Fe- and Co-oxides is in reasonable agreement with the measured value in this study.

• Microbiology and Biotechnology Letters
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• v.24 no.4
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• pp.519-524
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• 1996

The kinetics of growing microalga, Spirulina platensis was investigated to treat swine wastes with optimum growth conditions. Temperature was varied from 15 to 40$\circ$C at three different light intensities, 6 W/m$^{2}$, 12 W/m$^{2}$ and 24 W/m$^{2}$. The specific growth rate was increased as temperature increased up to 30$\circ$C. The activation energy was estimated as 13.5 kcal/mol by an Arrhenius relationship. 0.24 (1/day) of specific growth rate was obtained from batch cultivation with 30% swine wastes, compared to 0.31 (1/day) from clean culture. It was found that Spirulina platensis was able to reduce 70-93% of PO$_{4}$$^{3-}$ -P, 67-93% of inorganic nitrogen, 80-90% of COD and 37-56% organic nitrogen by adding various concentrations of swine wastes for 12 days of batch cultivation. Rate constants for removing nitrates and phosphates in treating swine wastes were estimated as 0.17 (1/day) and 0.14 (1/day) in the first order reaction, respectively. 1.52 (g/L) of maximum cell density was maintained at 0.20 (1/day) of dilution rate in continuous culture, adding 20% swine wastes for 30 days. The chemical composition of the biomass obtained from the process showed 58.7% of protein, 11.0% of lipid and 15.6% of ash.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.4
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• pp.651-659
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• 2000

The characteristics of ammonia removal by natural neutralizer were studied by using a scrubber type equipment. As operation parameters, neutralizer dilution ratio, neutralizer inlet flowrate, air flowrate and initial ammonia concentration were selected and their effects on ammonia removal efficiency were investigated. The optimal removal effect was achieved at neutralizer dilution ratio of 1.0% and neutralizer inlet flowrate of $60m{\ell}/min$. On the other hand, with respect to air flowrate and initial ammonia concentration, there was no significant effect on removal efficiency, when loading rate was considered. In addition, ammonia removal reaction was investigated by analyzing the ammonia oxides, such as nitrites and nitrates, after reacting ammonium solution with natural neutralizer. The result shows a partial oxidation by natural neutralizer besides dominant absorption of ammonia.

• Preventive Nutrition and Food Science
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• v.20 no.3
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• pp.198-203
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• 2015

The present study was conducted to assess the status of vitamin C among healthy young adults in relation to serum antioxidant parameters [glutathione (GSH), thiols, and total antioxidant capacity, (TAC)], and oxidative stress markers [malondialdehyde (MDA), and nitrites plus nitrates (NN)]. A prospective study included 200 young adults, and their dietary intake was assessed by using food diaries. Fasting plasma vitamin C, serum levels of GSH, thiols, TAC, MDA, and NN were measured using biochemical assays. It was observed that 38% of the enrolled subjects, n=76, had an adequate dietary intake of vitamin C (ADI group). Meanwhile, 62%, n=124, had a low dietary intake of vitamin C (LDI group) as compared to the recommended dietary allowances. The fasting plasma level of vitamin C was significantly higher in the ADI group as compared to the LDI group. Oxidative stress in the sera of the LDI group was evidenced by depletion of GSH, low thiols levels, impairment of TAC, an elevation of MDA, and increased NN. In the ADI group, positive correlations were found between plasma vitamin C and serum antioxidant parameters (GSH, thiols, and TAC). Meanwhile, the plasma vitamin C was negatively correlated with serum MDA and NN levels. This study reveals a significant increase of oxidative stress status and reduced antioxidant capacity in sera from healthy young adults with low intake of the dietary antioxidant, vitamin C.

• Transactions of the Korean hydrogen and new energy society
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• v.23 no.3
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• pp.199-206
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• 2012

HC-SCR was conducted over Co-Pt/ZSM5 catalyst coated over 200 cpsi cordierite in the condition of atomspheric pressure and $200^{\circ}C-500^{\circ}C$. Weight ratio of Co/Pt determined from EDX analysis was 8/2, which was almost equal to the weight ratio at preparation step. XPS showed that nitrates within cobalt precursor and chlorine withn Pt precursor were removed. TEM result demonstrated that crystallite size of cobalt and Pt was under 5nm. Among these tested hydrocarbon reductants, isobutane ($i-C_4H_{10}$) showed the highest de-$NO_x$ yield of 80% under the condition of the mole ratio of reductant/NOx=1.0 at $180^{\circ}C$. De-$NO_x$ yield from HC-SCR was increased as the carbon number of hydrocarbon reductant was increased. The decrease of bonding energy between C and H of HC reductant played a role to increase of de-$NO_x$ yield, which indicated that the dissociation step of C-H bond of hydrocarbon molecule might be the rate determining step of HC-SCR. The increase of oxygen concentration in the feed resulted in the decrease of de-$NO_x$ yield but the increase of CO and $N_2O$ yield.